documents & reports - all documents | the world bank ......«vodovod i kanalizacija ogulin»....

OGULIN SEWERAGE SYSTEM &

WASTE WATER TREATMENT WORKS

ENVIRONMENTAL IMPACT STUDY (UPDATED)

Parsons Brinckerhoff Parnell House

Oikon Ltd Vlade Prekrata 20 1000 Zagreb Croatia

E1592 V 5

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Environmental Impact Study of the Ogulin Sewerage System

2

25 Wilton Road London SW1V 1LW June 2005


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1 INTRODUCTION ......................................................................................................................................... 2

1.1 OVERVIEW................................................................................................................................................. 2 1.2 THE PROPOSED PROJECT............................................................................................................................ 2 1.3 PROJECT PROPONENT................................................................................................................................. 7 1.4 APPROACH TO THE EIA.............................................................................................................................. 7 1.5 STRUCTURE OF THE ENVIRONMENTAL STATEMENT .................................................................................. 8

2 LEGISLATIVE AND PLANNING CONTEXT FOR THE EIA .............................................................. 9

2.1 INTERNATIONAL CONVENTIONS, PROTOCOLS AND COMMITMENTS........................................................... 9 2.2 NATIONAL LEGISLATIVE REQUIREMENTS................................................................................................ 10 2.3 PHYSICAL PLANNING DOCUMENTS.......................................................................................................... 11 2.4 PROTECTED NATURAL, URBAN AND RURAL VALUES.............................................................................. 12

3 EXISTING CONDITIONS......................................................................................................................... 14

3.1 SITE LOCATION........................................................................................................................................ 14 3.2 SURFACE DRAINAGE................................................................................................................................ 14 3.3 GEOLOGY AND SOILS............................................................................................................................... 19 3.4 HYDROGEOLOGY..................................................................................................................................... 23 3.5 CLIMATE AND METEOROLOGY................................................................................................................. 36 3.6 SOCIO-ECONOMICS................................................................................................................................... 39 3.7 TRAFFIC................................................................................................................................................... 39 3.8 ECOLOGY AND NATURE CONSERVATION................................................................................................. 40

4 PROJECT DESCRIPTION........................................................................................................................ 44

4.1 OVERVIEW............................................................................................................................................... 44 4.2 NEED FOR THE PROJECT........................................................................................................................... 44 4.3 THE PROPOSED SEWERAGE SYSTEM........................................................................................................ 45 4.4 THE WASTE WATER TREATMENT PLANT................................................................................................. 49 4.5 RECEIVING WATERS................................................................................................................................ 56 4.6 ANALYSIS OF ALTERNATIVES .................................................................................................................. 56

5 IMPACT ASSESSMENT AND MITIGATION ....................................................................................... 62

5.1 INTRODUCTION........................................................................................................................................ 62 5.2 THE SEWAGE NETWORK.......................................................................................................................... 62 5.3 THE WASTE WATER TREATMENT PLANT................................................................................................. 63 5.4 IMPACTS DURING DECOMMISSIONING...................................................................................................... 67 5.5 IMPACTS DURING ABNORMAL OPERATION.............................................................................................. 67

6 ENVIRONMENTAL MONITORING, MANAGEMENT AND CONSULTATION............................ 69

6.1 OVERVIEW............................................................................................................................................... 69 6.2 SURFACE WATERS.................................................................................................................................... 69 6.3 GROUNDWATERS..................................................................................................................................... 69 6.4 SLUDGE QUALITY .................................................................................................................................... 71 6.5 AIR QUALITY ........................................................................................................................................... 71 6.6 NOISE....................................................................................................................................................... 71 6.7 ENVIRONMENTAL POLICIES ..................................................................................................................... 72 6.8 PUBLIC CONSULTATION........................................................................................................................... 72

7 LEGISLATIVE REFERENCES................................................................................................................ 74


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Introduction

Overview

Ogulin is a market town located in northern Croatia (see Figure 1.1, 1.2 and 1.3 for location). The town has long-held problems of wastewater and stormwater treatment and disposal. At present the majority of the households collect wastewater on their own and discharge it without prior treatment into septic tanks (“black pits”) or directly into the nearby sinkholes or abysses, where it enters the local groundwaters. The situation with stormwater drainage is the same, and the increase in hard surfaces that has accompanied urbanisation has resulted in not only a considerable increase in the flow of stormwaters, but also in their pollution, with heavy precipitation commonly resulting in clogging and local flooding, which in turn have impacts on hygiene, ecology and economy.

The Proposed Project

Project Location

Ogulin town is located in the Ogulin-Plaški valley, a hilly area some 300 m above sea level, and rising to 500-600 m in higher elevations (see Figure 1.3). The valley is comprised of two karst fields, the Ogulin and Plaški Fields, made of highly pervious layers of limestone and dolomite with occasional impervious Triassic layers. The karst area is characterized by long cave systems such as ula’s Precipice- Medvednica Cave, etc.

Figure 1.2 Ogulin Town Setting


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This area is considered sensitive since local pollution can have grave consequences on a wide area and the construction of a drainage system has therefore been set as one of the priorities of the town of Ogulin and conceptual designs for the sewerage system and the wastewater treatment plant were first developed in 1989. It was decided to form the combined sewerage system in the town, i.e. the system of transporting household and industrial wastewaters together with precipitation waters through the same (common) collectors. The idea was that wastewater will first be treated and then discharged into the underground on the territory of Galga, to the north of the settlement of Otok Oštarijski.


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Figure 1.1. Location Map for Ogulin Town


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Figure 1.3 The Ogulin Region


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Project Concept

The proposed project provides for the construction of a partly combined system with a network of sewers which would receive both household and industrial wastewater, with stormwaters collected from those (mostly traffic) surfaces where they could cause traffic difficulties or endanger the town in some other way. The need for such a sewerage system is determined by a number of factors, including the current number of inhabitants, the quality and composition of wastewater, and ecologic and sanitary requirements. The conceived sewerage system shall provide proper medical conditions on the area of the town and gravitational suburban settlements, as well as lessen the negative impacts of waste and dirt on the living environment. The issue of draining precipitation water from the areas not encompassed by this design will be the subject of a separate conceptual design on storm water. Due to the necessity of constructing the Ogulin Sewerage System (transport and collection canals with the treatment plant), the town of Ogulin through its public utility Vodovod i kanalizacija has commissioned the preparation of the project documentation for the collection canals (Catchment area A) for the central part of Ogulin, as well as for the wastewater treatment plant. Up till now only the main collector of catchment area A has been constructed, excluding collection sewerage network.The sewerage system implies a set of construction facilities collecting the polluted wastewater, the transport of wastewater from the source to the wastewater treatment plant, where it is treated up to the legally prescribed degree, and the discharge of wastewater into the groundwaters. The main purpose of the sewerage system may be said to be a prompt removal of wastewater from a populated area and its treatment until achieving the quality required for the area in question before disposing it into the recipient.

The purpose and the objective of constructing the sewerage system is to use the set of construction facilities for a safe and economical collection and treatment of wastewater, thus creating an inhabited area that would constantly provide optimal healthy conditions. Wastewater has to be treated up to the level not harmful for the recipient and thus for the environment in general. Furthermore, the construction of the urban sewerage system will improve the drainage regime of precipitation water, thus protecting the surface and subsurface urban elements from flooding and enabling the drainage of traffic surfaces. The wastewater drainage system will be connected onto the wastewater treatment plant. The recipient of the effluent coming out of the plant as well as of the diluted water will be absorbing wells or the River Dobra.

Interaction with the National Water Plan

The National Water Protection Plan requires waters to be managed on the principles of an integrated water system and sustainable development, with implementation of the precautionary principle to prevent and restrict the discharge of hazardous and other substances which might cause water pollution. The proposed project proposes the construction of the public drainage system to be completed by 2010 for the facilities between 10,000 and 15,000 PE. The construction of the wastewater treatment plant can begin if at least 70% of the total capacity of the public drainage system has been completed.


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EIA and Permitting Requirements

In accordance with the current legislation, the sewerage systems higher than 10,000 PE require the preparation of the Environmental Impact Study. The Environmental Impact Study of the Ogulin Sewerage System has been prepared according to the conclusions and the minutes of the meeting held on August 8, 2000 on the premises of the Ministry of Environmental Protection, Physical Planning and Construction,. The primary duty of all the interested parties (Hrvatske vode, the town of Ogulin and other beneficiaries of the Ogulin sewerage system) is the construction of the central wastewater treatment plant “Ogulin”, including the main drainage canals.

A location permit for the main sewage collectors and pumping stations project of the drainage system of the town of Ogulin (collection canal – Catchment area A) as well as for the Ogulin Wastewater Treatment Plant has been obtained, following completion of the process of assessing the acceptability of the project with regard to the environment and establishing the necessary environmental protection measures, and once those components were included in the Programme Draft of the planned project.

Project Proponent

The immediate project beneficiary of the project is the municipal company ViK Ogulin «Vodovod i kanalizacija Ogulin». This is a public company, formally established by the Town of Ogulin, which is the majority shareholder. ViK is responsible for the construction and maintenance of the drinking water supply system to households and industries as well as the construction and maintenance of the wastewater collection system, network enlargement plans and the construction of a wastewater treatment plant. ViK Ogulin is an independent legal entity with limited liability and managed by a Director, who is appointed by the Supervisory Board of ViK Ogulin, which in turn is appointed by the Town. The Director reports to the Board and the Town Council on regular basis and is responsible for day-to-day operations and the financial stability of the company. However, the Town must approve important issues including investment policy and tariff increases. A private sector share in the municipal infrastructure is neither present nor planned. The relationship between the Town Administration and ViK is governed by a set of regulations, ownership of assets, control mechanisms and the mutual desire to improve water supply and wastewater services in the Town. All environmental mitigation and management activities related to the construction and management of the collector network of the sewerage system and the wastewater treatment plant will be the responsibility of the ViK Ogulin municipal company.

Approach to the EIA

A significant amount of research and interpretation of collected data have been conducted on the project site of the wastewater treatment plant with the purpose of defining geological, hydrogeological and geo-mechanical features of the terrain. Particular field studies undertaken for the project have included the following (see Section 3):

• Hydrogeological research. The Institute of Geology, Zagreb has carried out hydrogeological research needed for the design and construction of the Ogulin wastewater treatment plant. The design provides for the discharge of treated water


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through absorbing wells into the carbonate underground on the territory of Galge, north of the settlement of Otok Oštarijski. The programme of works includes hydrogeological mapping of the locations of the planned facilities in scale 1:1,000, a review of more pronounced depressions (sinkholes), as well as an assessment of the conditions or hydrogeological features of the rocks. In order to determine the condition of the rocks in the bedrock (fissures and cracks) and in order to test permeability to water, two bores, each 30 m deep, were made on the locations of the planned absorbing wells. The bores were cored at entire depth; the core was placed into crates, intended for technical documentation. Water permeability was tested during boring at each 5 meters, under pressure of 2, 5 and 7 bars (10 bars were not achieved). The boring was performed with a boring machine BA-300, with initial diameter of 116 mm and final diameter of 86 mm. Protective columns of 110 mm in diameter were implanted into the bores, 12.00 m into B-1 and 4.00 m into B-2.

• Dye Tests. Dye tests have also been carried our to examine groundwater flow. Three of four planned excavations were made on the slopes of sinkhole a. Following an experimental absorption performed by pouring out a fire-engine tank into each selected suffosion, sinkhole b was established to possess a considerably higher absorptive capacity. The dye that was to establish the direction of the underground flow (12 kg of Na-fluorescein) was therefore poured into sinkhole b, along with 50 m3

of water. More important sources from Gojak to Kuka�e were under observation.

• Geotechnical Study. A geotechnical study for the foundation of the proposed wastewater treatment plant was also prepared. The structure shall consist of a prepumping station, a retention basin and a wastewater treatment plant. The composition of soil obtained from hydrogeological research was used for the assessment of the geotechnical characteristics (parameters) of the soil, needed for the preparation of the geotechnical study.

Structure of the Environmental Statement

The remainder of this EIA Study is structures as follows:

• Section 2 outlines the legislative and planning context for the EIA; • Section 3 describes existing conditions; • Section 4 describes the proposed project; • Section 5 identifies potential impacts and proposed mitigation; • Section 6 outlines a monitoring plan for the project; • Section 7 describes public consultation held to date ; and • Section 8 includes main project references.


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Legislative and Planning Context for the EIA The project has been developed to fully comply with environmental regulations of the host country as well as the EU. Particular attention has been paid to environmental impact assessment, environmental performance and public consultation requirements. Croatia has a well-developed set of environmental laws. There is a requirement under the Law on Environmental Protection (NN 82/94) for a comprehensive review of a project’s potential environmental impacts (By-Laws on Environmental Impact Assessment, NN 34/97 and NN 37/97). The agency responsible for review and approval of environmental impact assessment (EIA), the Ministry of Environmental Protection and Physical Planning is also the main agency responsible for implementing the laws related to nature conservation, potential air emissions, water/wastewater management, and solid waste management. The assessment presented in this EIA incorporates information presented in the Croatian requirements for EIA. As part of its ongoing plan to start accession process for the European Union, Croatia has been making progress in harmonising its environmental laws with those of the EU. For example, the Croatian Law on Environmental Protection (NN 34/97), Law on Nature Conservation (NN 30/94), Law on Waste Management (NN 34/95), Law on Air Protection (NN 48/95) are being continuously updated to conform to EU Council Directives.

International Conventions, Protocols and Commitments

The Republic of Croatia is a signatory to a number of international obligations as shown in Table 2.1 below.

Subject International Conventions, Protocols and Commitments EIA Convention on Environmental Impact Assessment in a

Transboundary Context (Espoo 1991) came into force with respect to the Republic of Croatia on 10 September 1997.

Protocol on Strategic Environmental Assessment The Republic of Croatia signed the Protocol in 2003. Climate

Law on Ratification of the United Nations Framework Convention on Climate Change (Rio de Janairo 1992)

Published in OG–IT, No. 2/96, came into force in Croatia on 7 July 1996.

Kyoto Protocol to the Convention on Climate Change (Kyoto 1999.)

The Republic of Croatia signed the Protocol in 1999.

Gov. Legislation OG-IT No.12/93 – Montreal Protocol on Substances that Deplete the Ozone Layer – dated 8th October 1991 Stockholm Convention of Presistent Organic Pollutants signed in 2001

Air Convention on Long-range Transboundary Air Pollution (Geneva 1979)

the Republic of Croatia became a party to the Convention on 8 October 1991 (OG- IT 12/93)

Protocol to the 1979 Convention on Long-range Transboundary Air Pollution on Persistent Organic Pollutants (Aarhus 1998)

The Republic of Croatia signed the Protocol in Aarhus in 1998.

Vienna Convention for the Protection of the Ozone Layer (Vienna 1985)

Pursuant the notification on succession, the Republic of Croatia became a party to the Convention on 8 October 1991 (OG- IT 12/93).

Stockholm Convention on Persistent Organic Pollutants (Stockholm 2001)

Republic of Croatia signed the Convention in 2001.

Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal 1987)

the Republic of Croatia became a party to the Convention on 8 October 1991 (OG- IT 12/93).

Sea * Croatia has a large number of Protocol relating to sea, these however are felt not to be relevant to this project. Waste Gov. Legislation OG-IT No.3/94 Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and

their Disposal - dated 9th May 2000 General European Landscape Convention (Florence, 2000) Published in OG–IT, No. 12/02, came into force with respect

to the Republic of Croatia on 1st March 2004, and the effective date was published in OG-IT 11/04.

Protocol on Pollutant Release and Transfer Registers to the Aarhus Convention (Kyev 2003)

The Republic of Croatia signed the Protocol in 2003.


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The study complies with all the above protocols and conventions and is not expected to have any adverse transboundary influence.

National Legislative Requirements

The proposed project is required to be in accordance with the National Water Protection Plan (Official Gazette 8/99) and the Regulations on Limit Values of Indices, Hazardous and Other Substances in Wastewater (Official Gazette 40/99), which prescribe both recipient category and effluent standard.

In addition, the project is required to operate in accordance with the national and European legislation outlined in Table 2.2 below.

Subject

Croatian legislation EU legislation (number only)

EIA Gov. Legislation – Ordinance on Environmental Impact Assessment (OG No. 59/00, 136/04)

97/11/EC, 85/337/EEC

Air Quality

Gov. Legislation – Air Protection Act (OG No. 48/95, 178/04), will be applied from 31st March 2005

96/62/EC, 97/101/EC, 1999/30/EC, 2000/69/EC, 92/72/EEC

Gov. Legislation – Regualtion on Limit Values of Pollutant Emissions from Stationary Sources into the Air (OG No. 140/97, 105/02, 108/03, 100/04)

96/62/EC, 91/692/EEC, 84/360/EEC, 97/101/EC, 96/61/EC

Gov. Legislation – Regulation on Recommended and Limit Air Quality Values (OG No. 101/96, 2/97) Gov. Legislation – Regualtion on Substances Depleting the Ozone Layer (OG No. 7/99, 20/99) Gov. Legislation – Regulation on Sitting of National Network Stations for Continous Air Quality Monitoring (OG No. 4/02) Gov. Legislation – Programme on Air Quality Measurement in the National Air Quality Monitoring Network (OG No. 43/02)

–

Water Quality 76/464/EEC, 91/271/EEC, 96/61/EC, 2000/60/EC 91/271/EEC, 76/464/EEC, 80/68/EEC, 86/280/EEC

General Gov. Legislation – National Environmental Strategy (OG No. 46/02)

–

Gov. Legislation – National Environmental Action Plan (NEAP) (OG No. 46/02)

–

Waste Gov. Legislation – Waste Act (OG No. 178/04) –91/698/EEC 86/278/EEC 2000/532/EC, /442/EEC, 94/3/EC, 91/689/EEC, 94/904/EC, 2001/118/EC, 2001/119/EC, 2001/573/EC 76/116/EEC, 80/876/EEC, 87/94/EEC

Receiving Water Category

The National Water Protection Plan (Official Gazette 8/99, Annex D-2) prescribes water classification. The waters at Ogulin are classed as belonging to category A (Highly Sensitive Areas) which include the following:

• groundwater used or planned for use in water supply • mountain streams up to settlements • watercourses in karst areas up to settlements • water in national parks and nature parks


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Effluent Standard

The Regulation on Limit Values of Indices, Hazardous and Other Substances in Wastewater (Official Gazette 40/99) defines limit values for: suspended matter, BOD5,COD, total phosphorus and total nitrogen, which are, following treatment, discharged from the public sewerage system into the natural recipient, and determined on the basis of plant size (PE) and recipient water class (area sensitivity). Based on the above, wastewater of the town of Ogulin belongs to "c) watercourse of the II. water class ("sensitive areas"), and therefore requires the following treatment levels for different plant sizes:

- up to 10,000 PE primary (I) + secondary (II) - over 10,000 PE primary (I) + secondary (II) + tertiary (III)

Treatment levels are defined in chapter C "Definition of Terms", para III, items 12-16 of the National Water Protection Plan (Official Gazette 8/99). Limit values of indices in wastewater discharged from a wastewater treatment plant after a certain level of treatment into a natural recipient are determined in the following table: TREATMENT LEVEL

INDICES LIMIT VALUE

L Total suspended matter 120-150 mg/l

II. Total suspended matter 35 mg/l (over 10,000 PE)

60 mg/l (up to 10,000 PE)

Biochemical oxygen demand 25 mg O2/l (over 10,000 PE)

BOD5 (20°C) without nitrification 40 mg O2/l(up to 10,000 PE)

Chemical oxygen

demand - CODcr

125 mg 02 / l (over 10,000 PE)

150 mg O2/l (up to 10,000 PE)

DL Total phosphorus 2 mg P/l (10,000-100,000 PE)

1 mg P/l (ve�e od 100.000 ES)

Total nitrogenH (organic N + NH3 + NO2+ NO3)

5 mg N/l (10.000-100.000 PE)

10 mg N/l (over 100,000 PE)

Physical Planning Documents

Both the proposed sewerage system and the wastewater treatment plant are considered part of the local infrastructure. The guidelines for the physical planning conditions (location permit) of the Physical Plan of the Former Municipality of Ogulin prepared by the Ogulin Municipal Assembly in 1978 (The Official Gazette, No. 28/78) state that the infrastructure facilities can be constructed within the proposed project location, and that the construction of the sewerage system with the wastewater treatment plant is requested with the purpose of protecting the River Dobra.

The Amendments to the Physical Plan of the Former Municipality of Ogulin (The Gazette of the County of Karlovac, No. 12/99), Paragraph B Issuing Location Permits, Article 32, require the location permits for municipal infrastructure facilities to be issued on the basis of the appropriate conceptual designs. The conceptual designs on the basis of which the issuing of the location permit is requested include the Wastewater Canals Conceptual Design (Hidroprojekt-Ing, April 1996) and the Conceptual Design for the Wastewater Treatment Plant Location Permit (Hidroprojekt-Ing, 1999). Another precondition for the location permit is the preparation of this Environmental Impact Study:


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Protected Natural, Urban and Rural Values

Pursuant to the Nature Conservation Act (Narodne novine, No. 30/94, 72/94), the parts of nature that are of interest to the Republic of Croatia and enjoy its special protection are as follows: - National park is a broad, mostly unmodified area of exceptional and multiple natural values, comprising one or more preserved or slightly modified ecosystems. The national park has scientific, cultural, educational and recreational purposes. Activities that do not threaten the authentic nature are permitted, whereas the economic use of natural resources if prohibited. - Nature park is a broad natural or partly cultivated area with marked aesthetic, ecological, educational, cultural, historical, tourist and recreational values. Activities that do not threaten its essential features are permitted. - Strict reserve is an area of unmodified or slightly modified nature. It is intended exclusively for scientific research, which shall neither change the nature’s biological diversity and authenticity nor threaten the undisturbed development of natural processes. - Special reserve is an area with one or more outstanding unmodified natural elements, of particular scientific importance and purpose. The special reserve can be: botanical (floristic, forest vegetation, etc), zoological (ornithological, ichthyologic, etc), geological, hydrological, marine reserve, etc. None of the activities, which might harm the distinctive characteristics of a special reserve, is permitted (picking and destroying plants, disturbing, hunting and killing animals, introducing non-native species, melioration activities, various forms of economic or other exploitation, etc). - Park-forest is a naturally grown or planted forest of a considerable landscape value intended for relaxation and recreation. The only permitted activities are those intended for the preservation and maintenance of the park-forest. - Protected landscape is a natural or cultivated area of a considerable aesthetic or cultural and historical value, or a landscape characteristic of a certain area. None of the activities, which might disturb the distinctive characteristics of a protected landscape, is permitted. - Nature monument is a single unmodified part or a group of parts of animate or inanimate nature with a scientific, aesthetic or cultural and historical value. It can be geological (mineralogical or paleontological site, layer structure, etc), geomorphologic (cave, solitaire rock, etc), hydrological (spring, waterfall, lake, etc), botanical (rare or site-specific plant specimen, etc), a small botanical and zoological locality, etc. Any activity endangering its characteristics and values is prohibited on or in the immediate vicinity of the nature monument.

- Park architecture monument is an artificially formed area (alley, botanical garden, arboretum, town park, line of trees, a set of trees and a single tree, as well as other horticultural forms) of a significant aesthetic, stylistic, artistic, cultural and historical or scientific value. Any activity that would change or damage its lasting values is prohibited in the park architecture monument or in its immediate vicinity.

- The category of individual plant or animal species under special State protection includes endangered or rare species. Any activity disturbing and obstructing the protected plant or


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animal in its natural growth and unhindered development (picking, damaging or removing a plant from its habitat, scattering, pursuing, hunting, restraining, injuring and killing animals, damaging their life forms, nests or broods and habitats) is prohibited. It is prohibited to hide, sell, purchase and seize or in some other manner obtain the protected plants and animals, as well as to stuff the protected animals. Wild growth and wildlife within a national park, strict reserve and special reserve are also under protection, as well as cave animals, regardless of whether they belong to the protected plant and animal species or not.

In the above-mentioned areas it is forbidden to perform any activity that might disturb the characteristics on the basis of which they were proclaimed reserves (picking and destroying plants, disturbing, hunting and killing animals, introducing non-native species, melioration activities, various forms of economic use, etc).

As the project site is located on the area of the town of Ogulin, a thorough research of the protected areas has been carried out in order not to harm or endanger the nature and the environment. According to available data, there are no registered protected structures and historical units or registered protected parts of nature on the wastewater treatment plant construction area. The purpose of the project itself is to protect the environment and prevent the pollution of surface water and groundwater.


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Existing conditions

Site Location

The town of Ogulin is located in the centre of Croatia, within Karlovac County, approximately half way between the cities of Zagreb and Rijeka. It is an important regional centre that grew up around the agriculture and wood processing industries and has extremely good links to other parts of the country. The town is situated on the Zagreb-Split highway, which opened in 2003 and also the Zagreb-Rijeka railway.

The town is situated within the Ogulin-Plaški valley at an altitude of about 300m above sea level, at the foot of Mt. Klek. The topography rises to between 500-600m in a line of limestone hills to the south-west and west of the town. Many springs emerge along the valley side, the largest of which is harnessed for the public water supply. These also feed surface watercourses where these flow over less permeable soils. The general landscape is of gently undulating fields with irregular, shallow depressions, sinkholes and valleys, typical of karst scenery, caused by varying amounts of dissolution of the underlying limestone bedrock. This low level plateau is cut by several canyons in the valleys of important karst watercourses, including the Dobra, Mre�nica, Kupa and Korana rivers.

Surface Drainage

Ogulin lies within the catchment of the Dobra River, which flows into the town from the west in a deep gorge, before sinking underground in a large sinkhole, known locally as ula ponor.Once underground, the river flows through an extensive cave system before emerging approximately 4km to the north-east before flowing in a general north-easterly direction towards Karlovac, approximately 40km distant. In the town centre the gorge is approximately 30m deep. Approximately once per year, after intense rainfall events and Spring snow melt, the capacity of the sinkhole is insufficient to cope with the high river flows generated and the gorge fills, resulting in flooding of the town centre. Water quality in the Dobra is monitored at a number of locations by Croatian Water (see Figure 3.1 for monitoring location points). Results indicate that high levels of BOD are present downstream of Ogulin, consistent with extensive discharge of wastewaters into the upstream catchment. Monitoring data from these sites are provided in Tables 3.1a and 3.1b.

Apart from the main drainage features associated with the Dobra River, however, the surface drainage network tends to be poorly developed due to the permeability of the surface soils and underlying bedrock. Rainfall tends to infiltrate the ground rapidly, where it causes dissolution of the carbonate substrata and results in the formation of dissolution features and the formation of karst topography. As a result, most of the drainage infrastructure within the town, such as from rooftops and highways, has historically been to soakaway, typically to areas of naturally increased infiltration capacity, signified by small surface depression features. The infiltrated water emerges as springs at lower elevations around the town. In the wider Ogulin area most of the drainage emerges at springs in the valley of the Dobra River, although some is known also to emerge in the valley of the Mre�nica River, to the south-east.

Most dwellings discharge wastewater and sewage in a similar manner. Whilst some properties have septic tanks, which are emptied by the municipality when necessary, it is understood that the majority of buildings do not require this service; raw sewage being discharged to solution features, where it rapidly infiltrates the ground. This is confirmed by the water quality of the main springs around the town, which show evidence of extremely high concentrations of faecal bacteria.

Five of the main springs in the vicinity of the town (Tounj�ica, Bistrac, Pe�ina, Gojak and Kuka�a) were monitored on 12 occasions between July 1995 and October 1996. The data obtained indicate consistent contamination by faecal coliforms, at times in excess of 2400


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counts/100ml. As these bacteria do not live long outside the gut, the data suggest a relatively rapid transportation of the contamination from ground surface to the spring sources (ie of the order of a few days only), consistent with groundwater movement through mature karst systems.


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Table 3.1a: Average Annual Water Quality Data for the DobraRiver (2003)

16581 - Dobra, Luke Upstream 0f Ogulin 16572 - Dobra, Leš�e Downstream of Ogulin

Indicator groups Indicator Measure unit n Relevant value Category Evaluation n Relevant value Category Evaluation

pH 12 8.28 I 12 8.269 I

conductivity uS/cm 12 325.4 I 12 333.1 IA - Physical-chemical

alkalinity m-value mgCaCO3/L 12 187.7 II 12 197.5 II

dissolved oxygen mgO2/L 12 10.8 I 12 10.32 I II

oxygen saturation % 12 85.5 I 12 85.5 I II

COD-Mn mgO2/L 12 2.371 I 12 1.9 I IIB - Oxygen regime

BOD5 mgO2/L 12 1.89 I

I

12 2.1 II II

ammonium mgN/L 12 0.0506 I 12 0.06 I

nitrits mgN/L 12 0.0164 II 12 0.01 II

nitrats mgN/L 12 2.0039 III 12 1.6 III

total nitrogen mgN/L 12 2.392 II 12 1.7 II

C - Nutrients

total phosphorus mgP/L 12 0.0598 I

III

12 0.09 I

III

nr. of coliform bacteria NCB/100mL 12 4380 III 12 10010 IV

nr. of faecal coliforms NFCB/100mL 12 2310 IV 12 1036 IVD - Mikrobiološki

nr. of aerob. bacteria BK/mL 37 0C 12 762 I

IV

12 1224 II

IV

E - Biological P-B saprobity indeks 2 1.84 II II 2 1.94 II II


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Table 3.1b: Average Annual Water Quality Data for the DobraRiver (2004)

16581 - Dobra, Luke Upstream 0f Ogulin 16572 - Dobra, Leš�e Downstream of Ogulin

Indicator groups Indicator Measure unit n Relevant value Category Evaluation n Relevant value Category Evaluation

pH 12 8.157 I 12 8.1 I

conductivity uS/cm 12 377.7 I 12 366.8 IA - Physical-chemical

alkalinity m-value mgCaCO3/L 12 186.8 II 12 198.5 II

dissolved oxygen mgO2/L 12 10.5 I 12 9.8 I

oxygen saturation % 12 94.8 I 12 93.3 I

COD-Mn mgO2/L 12 1.7 I 12 2.1 IB - Oxygen regime

BOD5 mgO2/L 12 1.9 I

I

12 1.8 I

I

ammonium mgN/L 12 0.06 I 12 0.1 II

nitrits mgN/L 12 0.007 I 12 0.01 II

nitrats mgN/L 12 1.9 III 12 1.5 II

total nitrogen mgN/L 12 2.1 II 12 1.7 II

C - Nutrients

total phosphorus mgP/L 12 0.06 I

III

12 0.09 I

II

nr. of coliform bacteria NCB/100mL 12 1038 III 12 1100 III

nr. of coliform bacteria K/100mL

nr. of faecal coliforms NFCB/100mL 12 438 III 12 276 III

nr. of faecal coliforms FC/100mL

D - Microbiological

nr. of aerob. bacteria CB/mL 370C 12 2790 II

III

12 309 I

III

E - Biological P-B saprobity indeks 2 1.9 II II 2 2.0 II II


18

Figure 3.1 Dobra River Monitoring Locations


19

Geology and Soils

Regional Geology

The geology of the Ogulin Area comprises primarily of Jurassic, Cretaceous, Miocene and Quaternary deposits, with occasional Tertiary sediments1. Most of the strata surrounding Ogulin are carbonates of Lower Cretaceous age; mainly fine-gained (micritic) limestones and dolomitic limestones. These are present over the area from Ljuboština in the north-west, across Ogulin and all the way to Plaški. These strata consist of grey and brown-grey medium-grained-to-coarse-grained dolomites and dolomitized limestones, fragmented and covered with humus layer up to 1 m thick. Due to dolomitization, the limestone structure is hardly noticeable, while the clasts of slightly dolomitized limestone point to the development of dolomites from algal-foraminiferal micrites and biomicrites. The town of Ogulin lies on the carbonate Cretaceous sediments of Neocomian age (K1

1+2), which are present above the Jurassic layers and comprise various sequences of limestones, dolomites and breccias. The boundary between the Upper Jurassic (Malm) rocjs and those of the Lower Cretaceous is characterized by change between limestones and dolomites. The foraminiferal limestones from the Cretaceous contain many orbitolinas and represent the so called “Upper Orbitolina limestones”. The Middle Miocene strata comprise layers of marl and sand with younger interlayers of carbon (M2), preserved in the remnants of old fault depressions located transgressively towards the Cretaceous bedrock. The Middle Miocene is lithologically represented by grey-blue marls, with fine-grained sands, with only rare interlayers of carbon. The Middle Miocene rocks are estimated to be approximately 100 m in thickness. The Quaternary deposits are of colluvium, ie poorly cemented to-non-bonded fragments of older rocks, which were transported from hillsides and ridges into lower elevations, probably during the Upper Pleistocene. The permeability of the carbonate strata varies according to its composition (for example, the proportion of clay or degree of dolomitisation), geological structure and tectonic damage (the amount of faulting/fissuring etc). In general, however, the presence of well developed cave systems suggests a highly developed solution network, where rainfall infiltrates and moves through the ground rapidly through preferential pathways, the capacity of which has been enhanced by carbonate dissolution. Limestones (ie calcium carbonate) are generally highly water-permeable, because of their fracture network, which is enhanced by carbonate dissolution from percolating waters. The large number of sinkholes in the area and the general absence of runoff during rainfall events indicates that the majority of precipitation infiltrates the ground readily, eventually to emerge at various spring sources of the Rivers Dobra and Mre�nica. Dolomites (ie calcium-magnesium carbonate), by contrast, tend to be generally of lower permeability, whilst surface clays have very low permeability and tend to retain water locally, such as in the base of sinkholes. Both dolomitic rocks and clay soils therefore act to retard the movement of water locally but do not prevent its movement completely. Local soils comprise “subsoil karst”, where limestones and some dolomites are mostly covered with red soil as much as 10 m thick (Mayer 1980). The soil is heterogeneous in structure and features, which are less prominent on the areas of “subsoil karst”, reservoirs of red soil material, and on the area of the Oštarije basin lying on gravelly clay.

1See 1:100,000 scale mapping entitled Ogulin - Veli� & Soka�, 1982


20

A geological map for the region is shown in Figure 3.2.

Local Geology

The proposed wastewater treatment works (WWTW) site at Galge, to the north of the settlement of Otok Oštarijski. The area has an undulating topography with a partial covering of shallow red Quaternary sediments. Several depressions (sinkholes) are noticeable, the bottoms of which filled with red clay-rich material of undetermined thickness. Elsewhere, poorly cemented limestones are present at surface, with alternating limestones and dolomites or dolomite outcropping in the western part of the terrain. The limestones are grey-brown to dark brown in colour, with beds typically between 0.2-2m in thickness, which mostly outcrop in a NE-SW direction and dip towards the north-west at between 14 - 38°. These show signs of lamination and contain numerous fissures, mostly vertical, but also parallel and diagonal in relation to the direction of the strata.


21

Figure 3.2 Geology of the Ogulin Area.

There are two prominent faults in the area, both of which trend from north-west to south-east. In the south-eastern part of the area, the fault is mostly manifested as a zone of prominent parallel fissures. To the south-west, this fault accentuates a hill, up to 323 m in elevation. The hill is surrounded by arable land with Quaternary soil cover, the bedrock of which is likely to contain dolomites. Limestone and dolomite strata are seen in suffosion in the peripheral part of the sinkhole (field). Vertical fissures are also visible. Where outcrop is absent the soil cover is of varying thickness. In the south-eastern part of the map (to the west of sinkhole d), the cover is between 0.7m and 1.0 m, which can be seen from ditches. In the area of test boreholes B-1 and B-2, the Quaternary cover is probably thick between 1m and 3 m. Borehole data from the site investigations are included in Figures 3.4 and 3.5. The cave systems, which are located underneath the central part of Ogulin town, are shown in Figure 3.3.

Figure 3.3 The Cave Systems below Ogulin


22


23

3.3.3 Geomorphology

A number of different features are present within the area of the proposed treatment plant, including a large number of small sinkholes, a fault plane and two small hills. The sinkholes are of particular importance, and investigation showed the following:

• Sinkhole a is the largest solution feature and seemed suitable as the location for discharge of treated effluent, particularly because in its lowest part it has a disc-shaped suffosion depression ca. 0.70 m deep and 3 m in diameter. During experimental infiltration of water, however, infiltration was relatively slow, considerably slower than in sinkhole b (see below). Three trial pits were excavated in sinkhole a to determine the condition of the rock beneath the Quaternary cover. These indicated that the soil cover is variable in composition and occasionally clay-rich, and that the underlying limestones are highly fissured.

• Sinkhole b is the nearest to the location of the planned wastewater treatment facilities. It

is approximately 5m deep; 15 m in diameter at the surrounding ground surface and between 5-6 m in diameter in its base. All other sinkholes are also equally shallow (or even shallower), with Quaternary sediments at the bottom or noticeable limestone outcrops both at the bottom and on the flanks.

Seismic data has been recorded in Croatia since the end of the 19th century, when a seismologic station was put into operation in Zagreb, following an earthquake in the city in 1880. Published data indicate a maximum expected earthquake intensity near Ogulin of 6° MCS.

Hydrogeology

Exploratory Boring and In-Situ Testing

A geotechnical assessment of the proposed wastewater treatment works site by the Institute of Geology in Zagreb indicates that the underlying geology consists of low plasticity clay overcrumbling rocky karst material. The results two 30m boreholes drilled on the site are considered in detail in the Institute report and are summarised as follows:

• Borehole B1. The upper 13m consisted of clay strata of low permeability. Beneath this was limestone with numerous fissures and notable traces of limestone dissolution. The maximum pressure that could be achieved between 13-18m was 2 bars at a pumping rate of 100 l/min, which corresponds to a permeability of 76 Lugeons (Lu). The maximum pressure obtained between 20-25 m was 7 bars at an average water flow of 78 l/min, which corresponds to water permeability of 18 Lu.

• Borehole B2. The upper 3m of this borehole comprised of clay and the first permeability

test was performed between 5-10 m depth, in fissured and chipped limestone. The maximum pressure achieved was only 2 bars with a flow of 100 l/min, which corresponds to 76 Lu. Beneath this only 30 cm of core was recovered (metres 5-6) and this zone is considered to have the maximum permeability, due to the presence of solution cavities. Steep diagonal fissures up to 1 cm in width, “covered” in yellowish calcitic clay, as well as cavities, were also recorded between 9.1 and 9.5 m depth. Between 10-13 m, compact limestone with occasional diagonal fissures was present and pressures of 2 and 5 bars were achieved with permeabilities of between 22 Lu and 29 Lu were obtained. Between 13 and 15 m there was increased fissure density and vertical fissures up to 1 cm wide were present. Between 15-20 m fragmented and fissured limestone, infilled with red clay, was present with a water permeability of 16 - 22 Lu.


24

Below this the rocks were even more badly broken and the maximum pressure obtained between 20-25m was 2 bars with a flow of 100l/min (corresponding to a water permeability of between 58.8 Lu and 64.9 Lu). Core recovery indicated that a fault was present in this borehole between 23.5 - 26.7 m.


25

Figure 3.4. Borehole Profile for B1


26


27

Figure 3.5 Borehole Profile for B2


28


29

3.4.2 Groundwater Dye Test

In order to establish the direction of groundwater flow from the Galga area and potential links with spring sources in the valleys of the Rivers Goja�ka Dobra, Bistrac, Tounj�ica and Kuka�a, adye test was undertaken from sinkhole b (Figure 3.3). The details of the testing carried out are reported separately in the report by the Institute of Geology, Zagreb and are summarised below. Prior to undertaking the dye test the absorptive capacity of the sinkhole was determined and background water samples were obtained from all the proposed spring locations, shown on Figure 3.3. Some 12 kg of sodium-fluorescein, dissolved in 200 l of water, were then poured into the base of the sinkhole and flushed into the subsurface by 50 m3 of water. Monitoring of the spring sources was undertaken three times a day. The dye test was performed at a time of a relatively fast recession of high water level. During the previous day, water had ceased to flow through the Zagorska Mre�nica river bed, while in the course of 46 hours, between November 15 - 17, the water level on the Bistrac River had fallen from 38 cm (flow approximately 2.20 m3/s) to 30 cm (flow approximately 1.32 m3/s). During an inspection on November 22, it was established that dye had emerged at the Pe�ina source, greening the entire downstream flow of the River Bistrica. The dye could not be seen by the naked eye at other sources. Subsequent analysis of all samples by a digital Perkin Elmer photospectrometer the dye was also established at the sources of the River Bistrica (Bistrac) and the River Kuka� but at considerably lower concentrations. The apparent rate of underground flow obtained from the test was between 1.2 cm/s and 2.7 cm/s. Groundwater data from the springs is provided in Tables 3.2a - 3.2l below

Table 3.2a Sampling conducted 19.07. 1995., sunny weather with no wind, during dry period

Parameters Tounj�ica Bistrac Pe�ina Gojak Kuka�a

Turbidity SiO2/l 0 0 0 0 0

Colour Co-Pt scale up to 5 up to 5 up to 5 up to 5 0

Temperature C 11.6 11 13 14.8 11.6

Conductivity (uS/cm) 357 396 406 365 482

PH 7.75 7.45 7.45 7.45 7.4

KMnO4 demand (mg O2/l) 0.88 0.4 0.4 1.28 0.64

BOD5 (mg O2/l) 0.71 0.93 0.4 0.96 1.12

Dissolved oxygen (mg O2/l) 12.96 11.66 11.97 10.16 10.44

Ammonium (mg N/l) 0 0 0 0.044 0

Nitrits N/l 0.005 0.003 0.002 0.017 0.002

Nitrats N/l 1.257 2.533 3.924 1.733 2.509

Anionic detergents mg/l 0.082 0.044 0.088 0.102 0.081

Non- ionic detergents ug/l 0 18.3 0 228.5 51.8

Fats and oils ug/l 28.4 21.3 39.2 33.8 22.6

Mineral oils ug/ 7.7 8.2 8.3 10 4.5

Lead ug/l <50 <50 <50 <50 <50

Total coliforms in 100 ml 930 150 1500 750 150

Faecal coliforms in 100 ml 0 70 70 150 0

Fecal streptococcus in 100 ml 4 23 23 23 23


30

Figure 3.3 Groundwater Dye Test Locations


31

Table 3.2b Sampling conducted 24.08.1995 after a rain period


Turbidity SiO2/l up 5 0 up to 5 0 5-10.

Colour Co-Pt scale 5 up to 5 up to 5 up to 5 up to 5

Temperature C 18 12 13 13 12


pH 7.4 7.7 7.45 7.4 6.45

KMnO4 demand (mg O2/l) 9.2 7.4 5.8 6.6 6.8

BOD5 (mg O2/l) 2.5 5.32 2.25 1.75 2.4


Ammonium (mg N/l) 0.790 0.253 0.238 0.173 0.197

Nitrits N/l 0 0 0 0 0

Nitrats N/l 3.166 2.547 2.027 2.083 1.391

Anionic detergents mg/l 0 0 0 0 0

Non- ionic detergents ug/l 0 18.28 12.19 9.14 0

Fats and oils ug/l 94.1 61.4 38.7 39.7 42.5

Mineral oils ug/ 13.8 11.7 7.3 5.8 5.6

Lead ug/l 10.2 7.7 20.2 7.7 14.8

Total coliforms in 100 ml >2400 >2400 >2400 240 43

Faecal coliforms in 100 ml >2400 >2400 150 240 43


Table 3.2c. Sampling conducted 28.09. 1995. In a period of heavy rainfall


Turbidity SiO2/l 0 0 0 0 0

Colour Co-Pt scale up to 5 up to 5 up to 5 up to 5 up to 5



PH 7.5 7.6 7.6 7.55 7.5

KmnO4 demand (mg O2/l) 2.79 2.96 2.64 2.79 2.48

BOD5 (mg O2/l) 0.1 1 2 2 1


Ammonium (mg N/l) 0 0 0 0 0

Nitrits N/l 0.008 0.016 0.013 0.014 0.012

Nitrats N/l 1.21 1.08 1.10 1.09 1.19


Non- ionic detergents ug/l 48.8 64.0 42.7 51.8 30.5

Fats and oils ug/l 25.7 42.3 26.2 131.8 32.9

Mineral oils ug/ 2.3 2.6 3.1 55.4 2.8

Lead ug/l 0.017 0.027 0.025 0.015 0.013



Fecal streptococcus in 100 ml >16 >16 9 16 16


32

Table 3.2d . Sampling conducted 07.11.1995.


Turbidity SiO2/l 0 0-5 0 0 0-5

Colour Co-Pt scale up to 5 5 up to 5 up to 5 5



PH 7.6 7.5 7.3 7.6 7.45

KMnO4 demand (mg O2/l) 1.76 1.59 1.99 1.19 1.84

BOD5 (mg O2/l) 1.3 2.8 1.3 2.5 2.3


Ammonium (mg N/l) 0.114 0.088 0.034 0.072 0.099

Nitrits N/l 0.021 0.015 0.001 0.009 0.021

Nitrats N/l 0.74 0.94 0.76 1.01 0.91

Anionic detergents mg/l 0 0 0 0 0

Non- ionic detergents ug/l 93.7 316.3 89.7 64 24.4

Fats and oils ug/l 36.7 51.8 36.7 76.5 183.9

Mineral oils ug/

Lead ug/l 16.0 16.5 15.1 15.1 30.0




Table 3.2 e Sampling conducted 20. 12. 1996. during cloudy weather. Samplings taken after heavy rainfall and rapid snowmelting


Turbidity SiO2/l 40 30 20-25 20-25 40

Colour Co-Pt scale 5-10. 5 5 up to 5 5-10.



PH 7.6 8.0 7.6 7.8 8.0

KMnO4 demand (mg O2/l) 1.7 1.5 2.4 1.6 1.5

BOD5 (mg O2/l) 0.3 0.5 0.5 0.6 0.7


Ammonium (mg N/l) 0.071 0.057 0.066 0.078 0.101

Nitrits N/l 0.022 0.021 0.022 0.021 0.027

Nitrats N/l 0.596 1.034 0.966 0.923 0.656

Anionic detergents mg/l 0 0.228 0.193 0 0

Non- ionic detergents ug/l 0 0.0 0 0 0

Fats and oils ug/l 77.7 88.6 70.0 72.3 75.8

Mineral oils ug/ 4.6 4.0 5.8 8.0 4.6

Lead ug/l 10.3 10.9 9.0 12.0 10.0





33

Table 3.2f Sampling conducted 11.04. 1009. while sunny weather, without wind.Week ago rainfalls with snow


Turbidity SiO2/l 0 10 do 5 5-10. 0

Colour Co-Pt scale up to 5 up to 5 up to 5 up to 5 up to 5

Temperature C 9.2 9 9 9.6 9


pH 8.2 7.9 8.1 7.9 7.9

KMnO4 demand (mg O2/l) 1.36 1.44 1.28 1.2 1.12

BOD5 (mg O2/l) 0.5 0.5 0.5 0.6 0.4


Ammonium (mg N/l) 0.041 0.106 0.039 0.032 0.050

Nitrits N/l 0.614 0.677 0.679 0.952 0.783

Nitrats N/l 0.012 0.015 0.013 0.013 0.014


Non- ionic detergents ug/l 0.0 18.3 12.2 0.0 15.2

Fats and oils ug/l 58.3 69.7 71.2 82.7 62.0

Mineral oils ug/ 9.5 12.6 10.8 12.9 11.3

Lead ug/l 9.0 2.8 3.0 4.1 4.5




Table 3.2 g. Sampling conducted 23.05. 1996. while sunny and humid weather, without wind. Dry period preceeded


Turbidity SiO2/l 5 5 5

Colour Co-Pt scale up to 5 up to 5 up to 5

Temperature C 11 7 6

Conductivity (uS/cm) 421 410 401

pH 7.5 7.6 7.6

KMnO4 demand (mg O2/l) 1.0 2.2 1.1 Not Available

BOD5 (mg O2/l) 0.3 0.63 0.22

Dissolved oxygen (mg O2/l) 8.9 9.04 9.02

Ammonium (mg N/l) 0.070 0.046 0.061

Nitrits N/l 0.097 0.092 0.095

Nitrats N/l 0.120 0.218 0.245

Anionic detergents mg/l 0 0 0

Non- ionic detergents ug/l 12.2 0.0 0

Fats and oils ug/l 49.7 61.5 63.8

Mineral oils ug/ 8.3 5.5 7.4

Lead ug/l 19.4 18.2 19.5

Total coliforms in 100 ml 23 43 240

Faecal coliforms in 100 ml 4 7 93

Fecal streptococcus in 100 ml 23 9 23


34

Table 3.2h Sampling conducted 07.06.1996. during sunny weather


Turbidity SiO2/l 5 5 5




pH 8.4 8.5 8.5

KMnO4 demand (mg O2/l) 3.1 1.99 1.59

BOD5 (mg O2/l) 5 4 1.1

Dissolved oxygen (mg O2/l) 13 13 12

Ammonium (mg N/l) 0.087 0.039 0.060

Nitrits N/l 0.067 0.016 0.021

Nitrats N/l 1.002 0.525 0.888

Anionic detergents mg/l 0 0.199 0.332

Non- ionic detergents ug/l 0 0 0



Lead ug/l 4.2 13.4 13.2



Fecal streptococcus in 100 ml 23 4 9

Table 3.2i Sampling conducted 14.08.1996. , sunny weather with light wind. The day before heavy rainfall


Turbidity SiO2/l 45-50 0-5 0-5

Colour Co-Pt scale 15-20 up to 5 up to 5



pH 8.0 8.4 8.5

KMnO4 demand (mg O2/l) 2.7 1.2 1.1

BOD5 (mg O2/l) 2.5 1 1.8

Dissolved oxygen (mg O2/l) 9.8 10.5 11.14 Not Available Not Available

Ammonium (mg N/l) 0.199 0 0

Nitrits N/l 0.130 0.020 0.024

Nitrats N/l 2.960 0.954 0.928

Anionic detergents mg/l 0.211 0.085 0.229




Lead ug/l < 50 < 50 < 50



Faecal streptococcus in 100 ml 0 43 23


35

Table 3.2 j Sampling conducted 11.09.1996. during cloudy weather,


Turbidity SiO2/l 0-5 0-5 0-5




pH 7.9 7.8 8.4

KMnO4 demand (mg O2/l) 1 1 3.5

BOD5 (mg O2/l) 1.6 1.3 4.1


Ammonium (mg N/l) 0.131 0.131 0.223

Nitrits N/l 0 0 0.001

Nitrats N/l 2.380 1.430 0.857

Anionic detergents mg/l 0 0 0


Fats and oils ug/l 45 104 110

Mineral oils ug/ 4 9 11

Lead ug/l 0 0 0




Table 3.2k Sampling conducted 08.10. 1996. during calm weather with light wind. The day before heavy rainfall


Turbidity SiO2/l 5-10. 0-5 0-5

Colour Co-Pt scale 5 5 10



pH 8.0 8.0 8.0

KMnO4 demand (mg O2/l) 2.1 1.3 1

BOD5 (mg O2/l) 7 3.5 2.5


Ammonium (mg N/l) 0.333 0.191 0.218

Nitrits N/l 0.009 0.002 0.006

Nitrats N/l 0.898 0.942 0.907

Anionic detergents mg/l 0 0.307 0




Lead ug/l 17.6 14.9 9.7





36

Table 3.2 l. Sampling conducted 22.10.1996. during sunny and clear weather,


Turbidity SiO2/l 5 0-5 0-5

Colour Co-Pt scale 5-10. 5 5

Temperature C 8 7 7


pH 7.9 8.2 8.0

KMnO4 demand (mg O2/l) 2 1.6 1.44

BOD5 (mg O2/l) 1.3 1 1

Dissolved oxygen (mg O2/l) 10.7 11.5 11.4

Ammonium (mg N/l) 0.172 0.131 0.239

Nitrits N/l 0.017 0.003 0.021 Not Available Not Available

Nitrats N/l 0.637 0.664 0.869

Anionic detergents mg/l 0.136 0.208 0.484




Lead ug/l 13.6 11.8 10.2




Note: Second half of 1996. was mostly rainy

Climate and Meteorology

Data for the meteorological assessment has been obtained from the Ogulin weather station, which is the nearest station of the Meteorological and Hydrological Service (DHMZH). The Ogulin area has a temperate continental climate and belongs to a circulation belt of mid-latitude winds with intensive and frequent weather changes. According to the Köppen Climate Classification System, this area’s climate can be marked as Cfsbx, which represents a moderately warm, moist climate, with the following characteristics:

• average monthly temperature is above 10° in more than 4 months in a year • average temperature of the coldest month in a year is between -3 ° C and 18 ° C • total quantity of precipitation is between 700 mm and 900 mm per year • shifting windiness; frequent light winds and calm, rare heavy winds.

Rainfall

Precipitation occurs throughout the year, although there is a wide variability in rainfall patterns. The 30-year mean recorded annual precipitation (1961-1990) is 1577mm as shown below.

Table 3.3 Average Monthly Precipitation, 1961-1990 (mm) (Source: DHMZH)

MONTH I II III IV V VI VII VIII IX X XI XII Year

Mm 106 110 122 138 125 129 119 136 139 139 175 141 1,577


37

The maximum 24 hour rainfall between 1983 and 1995 was between 49-106mm, as shown below.

Table 3.4 maximum Recorded Daily Precipitation (mm) (1983-1995) (Source: DHMZH)

YEAR ’95 ’94 ’93 ’92 ’91 ’90 ’89 ’88 ’87 ’86 ’85 ’84 ’83

DAILY PRECIPITATION

106 80 73 71 87 98 75 67 110 74 49 69 65

Air Temperature

The area around Ogulin lies is characterized by warm summers, cold winters and temperate transitional spring and autumn periods. The average yearly temperature is ca. 9.7 ° C, with June the warmest month (average temperature of 25.6 ° C) and January the coldest (average temperature of -5.0 ° C). The absolute minimum of -26.1 ° C was recorded in January 1968, while the absolute maximum of 38.0 ° C was reached in July 1983. The annual air temperature values for the period between 1949 and 1993 are shown in Table 3.5.

TABLE 3.5 – Average air temperatures (S), related standard deviations (SD), absolute maximum (M), absolute minimum (m), absolute amplitudes (A), average maximums (M) and minimums (m) of air temperatures (° C) at the Ogulin weather station in the period 1961-1990 (Source: DHMZH)

MONTH I II III IV V VI VII VIII IX X XI XII PER YEAR

S -0.5 1.4 5.1 9.6 14.2 17.4 19.2 18.2 15.0 10.3 5.3 1.0 9.7

SD 2.7 3.0 2.4 1.6 1.2 1.0 1.0 1.2 1.4 1.6 2.2 2.3 0.6

M 18.9 19.7 25.4 27.6 30.6 34.1 38.0 34.1 32.8 28.7 24.7 20.9 38.0

M -26.1 -24.3 -19.9 -8.1 -2.7 2.1 4.3 2.4 -2.2 -5.1 -19.1 -22.3 -26.6

Wind

Wind data has been obtained from observations performed at the Ogulin station over the period 1981-1990 and Figure 3.4 illustrates the annual rose wind obtained. The force of wind is determined on the basis of the Beaufort scale consisting of 12 grades as shown in Table 3.6 below.

Table 3.6 Beaufort grades-m/sec ratio

BEAUFORTS m/secCalm 0.0 - 0.2

1 0.3 - 1.52 1.6 - 3.33 3.4 – 5.44 5.5 - 7.95 8.0 – 10.76 10.8 – 13.87 13.9 – 17.18 17.2 – 20.79 20.8 – 24.4


38

Figure 3.4. Annual Wind Roses


39

Socio-economics

The Ogulin administrative region covers an area of 542 km2, comprising 14.9% of the total area of the County of Karlovac. The municipal centres include Josipdol, Tounj, Plaški and Saborsko, and the local centres are Oštarije and Jasenak. Whilst the town belongs to a sparsely populated area of Croatia, 16,732 people were recorded as inhabiting the town of Ogulin in the 1991 Population Census, which accounted for 9.1% of the county’s population. In addition, some 30,000 people gravitate towards the town, mostly from the Ogulin-Plaški plateau and the surrounding hills.

The following settlements are considered part of Ogulin town, with the nearest settlements (Lomost, Otok Oštarijski and Ku�ini� Selo)located some 2km away from the wastewater treatment plant site:

Bartolovi� Brestovac Ogulinski Desmerice Donje Dubrave Donje Zagorje Donji Zatezali Dre�nica Dujmi� Selo Gojak Gornje Dubrave Gornje Zagorje Gornji Zatezali Hreljin Ogulinski Janjani Jasenak Krakar Kucaj Maravi� Draga Markovi� Selo Mikašinovi�i Miri� Selo Miri�i Munjasi Nikoli�i Ogulin Oklinak Okruglica Otok Oštarijski Perici Podbitoraj Ponikve Popovo Selo potok Musulinski Puškari�i Radoj�i�i Seo�ani Tomi�i Trbovi�i Trošmarija Turkovi�i Ogulinski Višnji� Brdo Vitunj Vru�ac Vuceli�i Vukeli� Zagorje Modruško Ze�ica and Zrni�i.

The town’s economy depends on transportation, communications, health, and, traditionally, on forestry and agriculture, whilst the vicinity of the Croatian Olympic Centre Bjelolasica and Lake Sabljaci offers many possibilities for the development of tourism in the future. The recent modernisation of the main roads to the area are expected to contribute to the development of other forms of tourism apart from transit and weekend tourisms, and the area has many attractions to offer including the old zulum town, the River Dobra abyss, the Klek massive, Bukovnik and Sabljaci Lakes, etc, together with breathtaking scenery. The construction of the sewerage system and wastewater treatment plant is expected to contribute to a faster development of the town, as well as to a higher level of environmental protection.

Traffic

Ogulin is located at an important transit node. The recent modernisation of “Emperor Joseph’s Road” and the Ogulin-Novi Vinodolski and Vrbovsko - Ogulin - Plaški – Rakovica roads has helped the area become much more integrated into the traffic routes to the Croatian Littoral. The Zagreb-Rijeka railway also passes through Ogulin, thus putting the town into a favourable position with regard to the transport of goods and passengers, as well as with regard to its connection with other parts of country.

Within the town, there have been a number of traffic problems for several years, many of which are associated with local flooding during certain periods of the year. The critical spots of the town’s traffic system are the following:

• The bridge over the River Dobra in the very town centre (the so called Blue Bridge), which is 120 years old but has not been properly maintained, and is now closed to traffic and can be used only by pedestrians.

• When the water level of the Dobra grows high, which can occur several times during a year, the regional road Josipdol-Vrbovsko becomes flooded, thus breaking off not only all traffic connections between the eastern and western parts of the town, but also


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transit connections between main roads Karlovac-Vrbovsko-Rijeka and Karlovac-Jezerane-Senj.

• The spatial structure of the town, determined by the area’s geomorphology and by traditional links between the settlements, is formed as a radiant traffic network with several radiant directions towards the town. Such network might be convenient if there were several transversal connections, which still do not exist.

• The Zagreb-Rijeka railway passes through Ogulin, dividing it into two parts. The insufficient number and poor condition of railway crossings cause problems in interconnecting various parts of the town, particularly the industrial zone and the town centre.

Ecology and Nature Conservation

Overview

Croatia is amongst one of the most biologically rich countries in Europe and supports an unusually high concentration of endemic species, with the karst ecosystems considered especially valuable. The aquatic habitats within the system support a unique flora and fauna with a number of endemic species of fish, invertebrates and amphibians of particular note (for example some 11 species of fish are known to live only within the karst region of Croatia, with the cave dwelling species even more unique, diverse and restricted in their range). There are more then 8,000 known caves, sinkholes and underground rivers distributed throughout Croatia, and species new to science are continually being discovered. The flora and fauna of the Karst areas are threatened by numerous activities including the following:

• changes in water regimen (drainage, regulation of watercourses, etc.) • physical changes (eg. backfilling or natural overgrowing, particularly related to smaller

wetland habitats) • biological changes (excessive exploitation of resources or introduction of foreign

species) and • pollution of watercourses.

In the Ogulin area, the steep slopes of the River Dobra and its tributaries also provide an area of nationally significant habitat and several protected animal species are present including wolf, lynx, goshawk and raven. Local forest vegetation comprises of associations of sessile oak, bitter oak, hornbeam, and beech forest, whilst other habitats include areas of heaths and bracken, meadows and fragmented agricultural plots. The proposed WWTW site itself is located within a state-owned area of the “Krpel” hunting-ground, a large area of some 3000 ha of forest and agricultural land, but has no specidic ecological value.

Regional Flora

In the Ogulin area, the Mountain beech forests (Fagetum illyricum montanum) are commonly found in upland areas, and are dominated by beech (Fagus sylvatica) and silver fir (Abies alba), with wild cherry (Prunum avium), wych elm (Ulmus glabra) and sycamore maple (Acer pseudoplatanus). Shrubs include Rhamnus fallax, red elderberry (Sambucus racemosa), field rose (Rosa arvensis), dewberry (Rubus caesius) and daphne (Daphne mezereum), and low groundcover is represented by sweet woodruff (Galium odoratum), rattlesnake root (Prenanthes purpurea), wood anemone (Anemone nemorosa), woodland sedge (Carex sylvatica), dog’s mercury (Mercurialis perennis), odorous pig-salad (Aposeris foetida), woolly buttercup (Ranunculus lanuginosus), Gentiana aclepiadea, and several types of bitter cress (Dentaria bulbifera, D. enneaphvllos, D. trifolia, Cardamine trifolia). Christmas hellebore


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(Helleboro-Fagetum sylvaticae) is found on a dolomite ground together with Christmas rose (Helleborus macranthus), hepatica (Hepatica nobilis), hacquetia (Hacquetia epipactis) and Italian maple (Acer obtusatum). Other species include cornelian cherry dogwood (Cornus mas), black bryony (Tamus communis), bastard balm (Melitis melissophyllum), broad-leaved sermountain (Laserpitium latifolium) and Laserpitium marginatum, broad-leaved spignel (Peucedanum cervaria), autumn moor grass (Sesleria autumnalis), Aristolochia pallida, etc.

Many forests are privately logged with oaks and other large trees selectively felled. Timber mass, as the main indicator of the state of these forests, ranges mostly between 60 and 130 m3/ha. These forests, in the form of chopped plots, are owned by a larger number of owners and occur outside of the large, well marked state forests, which are the responsibility of the public enterprise “Hrvatske šume” through Uprava šuma Ogulin (The Ogulin Forest Management). The state forests can be divided into two groups: Naturally-grown forests, many of which have been actively felled, and plantations, mostly conifers, which are found largely on former common grounds, which have become overgrown by bracken due to neglect and end of exploitation. Seedlings of coniferous species were planted some thirty years ago (spruce, larch, Scots pine and black pine, Eastern white pine).

Amongst the agricultural lands, a range of meadows and heaths are present. Greenweed and heather (Genisto-Callunetum illyricum) heaths are common on acidified nutrient-poor soils where grazing and occasional burning of weeds is common. The typical species are heather (Calluna vulgaris) and greenweed (Genista pilosa, G. germanica), as well as a number of acidophilic species such as nuolike (Chamaespartium sagittale), erect cinquefoil (Potentilla erecta), matgrass (Nardus stricta), wood hawkweed (Hieracium sylvaticum), bracken (Pteridium aquilunum).

Oat meadows (Arrhenatheretum elatioris) grow on moderately moist soils rich in nutrients. Typical grass species include Arrhenatheretum elatius, Trsetum flavescens,meadow salsify (Tragopogon pratensis), wild parsnip (Pastinaca sativa) and field scabious (Knautia arvensis). There are also narrowleaf plantain (Plantago lanceolata), birdsfoot trefoil (Lotus corniculatus), sweet vernal grass (Anthoxanthum odoratum), meadow clary (Salvia pratensis), common yarrow (Achillea millefolium), barnyard grass (Dactylis glomerata), bugleweed (Ajuga reptans), red clover (Trifolium pratense), black medick (Medicago lupulina), etc.

Meadows of erect bromegrass and medium plantain (Bromo-Plantaginetum mediae) are found in mountainous regions. Plants are indicative of calcareous soils poor in nutrients, such as erect bromegrass (Bromus erectus), tor grass (Brachypodium pinnatum), Danthonia calycina,bulbous bluegrass (Poa bulbosa), kidney-vetch (Anthyllis vulneraria), self heal (Prunella grandiflora), speedwell (Veronica jacqinii), Hungarian clover (Trifolium pannonicum)and Genitana ciliata.

The proposed wastewater treatment plant would be located within an area of secondary regrowth and ephemeral scrub2 at the outskirts of the town. Such habitats are common within the Ogulin area and not considered to be of significant ecological value and no uncommon species have been recorded from the site itself.

Karst Habitats

2the invasive plant species Japanese Knotweed was also present on several areas of the site, and should be controlled during

construction


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Croatia’s karst area represents both a peculiarity and a “locus typicus” of an exceptional geological structure and hydrogeological characteristics, and the area around Ogulin is considered to be of global landscape value with its clear and unique watercourses. The mountain vegetation of the karst area, with plants growing in rock cracks and screes, also contains several endemic species including Croatia’s rarest plan– Velebit degenia – both the genera and species of this peculiar tertiary relict are endemic for Croatia. A great number of other relict taxa originating from the tertiary period also survive in Croatia’s karst region owing to the fact that they were not affected by icing. Among wetland plants which are threatened or rare at the European level, the following are particularly prominent: Siberian iris, arrowhead, water-aloe grassy-rush, calamus, roothless duckweed, greater bladderwort, water chestnut, scullcap, water germander, fritillary, water-clover, certain types of orchids and others. The unique underground system of fissures and watercourses are home to a wide diversity of underground fauna whose uniqueness is reflected in the number of endemic taxa. Several endemic fish taxa are present and the ichthyofauna of Croatia’s karst rivers is a wealth and value in global proportions. The karst rivers are also of especial interest for the special travertine-building community of the aquatic moss Cratoneuron commutatum which has developed, a phenomenon which is most evident in the area of the Plitvice Lakes, a national park registered on the World Cultural and Natural Heritage List. The blue-green algae living on the moss surface participate in the process of extracting calcium carbonate from water, producing a special form of loose, diaphanous travertine that mirrors the form of moss. The survival of the habitat depends on maintaining this biodynamic process and preserving the travertine-building community that is highly vulnerable to changes in water quality as well as the shading provided here by the dense surrounding forest.

Fauna

Many of the central European fauna are found in the Ogulin area, including some large species such as deer, boar, brown bear (Ursus aarctos), wolf (Canis lupus) and Eurasian lynx (Lynx lynx). Most of these larger species are protected under international conventions and whilst habitat fragmentation poses a threat to their future in the region in general, they have appeared more frequently in the area surrounding Ogulin in the last 30 years, with some 400 bears, 100 wolves and 80 lynxes recorded. Other species recorded from the general area include European wildcat (Felis sivestris), dormouse (Muscardinus avelanarius), greater and lesser horseshoe bat (Rhinolophus ferrumequinum and R. hipposideros), Mediterranean horseshoe bat (Rhinolophus euryale), Myotis emarginautus, long-fingered bat (Myotis capaccinii) and Bechstein’s bat (Myotis bechsteinii) as well as more common species such as hare, fox, badger, pine marten and polecat. The rare long-fingered bat is particularly associated with the karst area where it roosts in the local caves and feeds on insects above the streams and lakes, although poulations are threatened by infill of caves, vandalism, disturbance of colonies and changes in insect abundance as a result of changes in karst water quality. Otter and beaver are also present in some areas.

Birds present in the area include short-toed snake-eagle (Circaetus gallicus), peregrine falcon (Falco peregrinus), barn owl (Tyto alba), grey-headed woodpecker (Picus canus), flycatcher (Muscicapa striata), red-backed shrike (Lanius collurio) partridge, duck and pheasant.

Amphibians and reptiles found in the region include green lizard (Lacerta viridis) and Aesculapian snake (Elaphe longissima), and the karst habitats are particularly important for the endemic and relict amphibian species the Olm which lives in the underground lakes and stiller parts of watercourses where it feeds on aquatic animals. This species is considered threatened by chemical and biological pollution of underground waters. These watercourses are


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also important for fish - Croatia has 145 known kinds of freshwater fish, of which 11 are endemic. Although more than 55,000 species of invertebrate are predicted to live in Croatia, only about 17,500 have been recorded to date including some 730 endemic species including Troglocaris anophthalmus- a very rare cave-dwelling crayfish that is vulnerable to changes in the ground waters. The highest levels of endemism are in the underground species of snails and isopods, each group with more than half the underground species endemic to Croatia (Tsee table below), most often associated with aquatic systems in caves. Most groups of invertebrates are too poorly studied to estimate endemism and threats. Group No. of taxa No. of endemics % endemics MOLLUSCA Gastropoda(snails) Aquatic 129 79 61% ARTHROPODA (insects and relatives)

Pseudoscorpiones 80 27 34% Isopoda (sowbugs, pillbugs and relatives) Aquatic 24 12 50% Diplopoda (millipedes) 175 75 43%


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Project Description

Overview

The project involves the establishment of some 13 km trunk sewer for the collection of domestic and industrial sewage effluent and stormwater from high flood risk areas from the town of Ogulin. Effluent from the proposed sewer infrastructure will flow to a new tertiary wastewater treatment plant which will use biological means to treat the sewerage effluent to an acceptable standard before discharge to the groundwater via an adjacent sinkhole3. The plant will produce a stabilised sludge, which will be disposed of to an engineered domestic landfill. The proposed sewer system and wastewater treatment plant will be developed in a number of stages:

• Phase 1: initially the trunk sewer will be installed to collect stormwater from high risk

flood areas of the town with an expected maximum flow of 180 l/s. The stormwater effluent will be pumped in phase 2 to the wastewater treatment plant, which will treat the stormwater in an oil and sand trap to remove entrained oils and particulate matter before the discharge to the adjacent sinkhole. This phase of the project is complete.

• Phase 2: In phase 2 the treatment plant will be built and include additional equipment

downstream of the stormwater sewer installed in phase 1. The equipment, will allow the treatment of faecal wastewaters to a tertiary standard. The plant will use an activated sludge and membrane filtration methodology before discharge of the treated effluent to the adjacent sinkhole. The sewers constructed in phase 1 will be extended in phase 2 to become a partly combined sewerage system.

Following the commissioning of the phase 2 tertiary treatment plant it is envisaged that further domestic houses and industrial premises will connect to the sewer infrastructure thereby decreasing the regions current reliance on septic tank infrastructure. It is envisaged that during this transition phase any septic tank contents will be able to be treated in the plant. The contracts for the detailed design and construction of the proposed sewer system will be under ‘FIDIC Red Book’ and waste water treatment plant will be let under a ‘FIDIC Yellow Book’ contract. The yellow book rules specify a ‘performance based’ contract and as such the contractor is free to determine the exact equipment specification. With this in mind the following is a summary and description of a typical process methodology to provide a general understanding of how the plant will operate. The details of the size and operation of each process vessel and compartment may vary from one manufacturer to another, although the overall performance of the system will be tied down in the contract documentation.

Need for the Project

The construction of the proposed storm water and sewerage system is designed to replace the current system in the Ogulin area where sewerage is discharged without treatment to unlined

3Such solution has been confirmed by exploring the underground and testing ground absorption in abysses, presented in the

study “Geomehani�ko-geofizi�ki istra�ni radovi - ure aj za pro�iš�avanje otpadnih voda grada Ogulina“, prepared by “Geokon“, Zagreb (October 1999, no. E-090-99), as well as by previously prepared studies and tests conducted on the field.


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septic tanks or directly into the nearby sinkholes from where they are discharged directly into the groundwater environment. In addition to treating this wastewater, the growing urbanisation of Ogulin has led to an increase in impermeable surfaces, resulting in increased stormwater runoff and local flooding with associated impacts upon public health, ecology and economy. It is proposed that collect storm waters from those surfaces which in a significant storm event would cause traffic difficulties or would endanger the town area from flooding are piped into the proposed sewerage system.

It is relevant to that the fractured nature of geology in the area result in a direct pathway between the degraded groundwater resources in the Ogulin area and the Dobra River, which is used as a primary source of potable water for the region. As such it can be seen that the current sewerage disposal practices in the Ogulin area represent a clear risk to public health of the region.

In addition, the following are of direct relevance to the project:

o The karst watercourses fall into the category of threatened habitats among which the underground waters of Ogulin, are considered remarkable for their interesting fauna. Among the most serious and immediate threats to the unique karst fauna of Croatia is pollution resulting from inadequately treated wastewater, and other urban, industrial and agricultural runoff. Subterranean biota in the karst region in particular are seriously threatened by changes in water quality, and pollution from the city of Ogulin is cited as the cause for the decline of several such species.

o The landscape value in the karst region is considered to be of global, and the ‘Strategy & Action Plan for the Protection of Biological & Landscape Diversity of Croatia’, includes the preservation of the existing values of the biological and landscape diversity of the karst region as one its strategic objectives. To ensure the coordinated management of all natural resourcesin this area, one of the strategic guidelines calls ‘to commence a systematic rehabilitation of the existing sources of pollution posing threat to underground and surface waters of the karst region.

The Proposed Sewerage System

Overview

The proposed sewer system and plant will be designed primarily for the treatment of faecal sewerage from domestic sources and, potentially, industrial wastewater. However it is also proposed that the system will collect stormwaters from areas, mostly roadways, which are know high risk flood areas.

Ogulin is characterized by a number of separate zones within which the sewage will flow via gravity towards a common collection point (at the lowest terrain elevation). Other zones will be developed with the development of new suburban settlements and linking of existing settlements to the town. Currently four zones have been identified to supply sewer infrastructure to the Ogulin area, namely:

• Zone A. The zone encompasses the largest part of the town of Ogulin and hence represents the bulk of the drainage systems capacity.


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• Zone B. This zone encompasses the area of the town north of the Zagreb-Rijeka railway, including the settlements of Cindri�i, Vrta�e, Petar Ogulinski, Drenovac, Podvrh and � egar.

• Zone C. This zone encompasses the town area south of the Zagreb-Rijeka railway and west of the River Dobra.

• Zone D This zone encompasses the settlements in the southwestern part of the town: Otok Oštarijski, Kalca, Bošt, Brezik, Ku�ini� Selo, Sabljak Selo and Salopek Selo.

Zone A, the town of Ogulin, forms the centre of the sewer system and hence gravitational flow of effluent collected at the central collection point in Zones B, C and D are pumped to zone A before discharge to the treatment plant. The proposed layout for the sewage works is shown in Figure 4.1, and the zonage is shown in Figure 4.2.

Drainage Design - Zone A

The zone encompasses the largest part of the town of Ogulin and hence represents the bulk of the drainage systems capacity. The zone is based around the town centre, the area west of the River Dobra and the part to the northeast of the Zagreb-Rijeka railway. Roughly 6,190 inhabitants are expected to be living in the zone. This zone includes the settlements of Sv. Jakov, Lomost, Bira�i, Proce and Peš�enica. The total canal length proposed in the zone is 17,570 m, and the zone includes some of the more significant facilities being the pumping stations Centar, Proce and Peš�enica

The backbone of this zone’s sewerage network are the collectors A-1 to A-6. The combined drainage system will be retained for the very centre of the town. A relief facility - rainwater overflow K.P.-2 - is scheduled to be built in that part of the town, for peak stormwater events. Collectors A-1 and A-2 are designed to receive stormwater from the roads alongside which they are placed. The remainder of the network is designed for the collection of faecal sewerage. The nature of the terrain largely provides for gravitational flow. However it is proposed to build three pumping stations of a low capacity within the zone. The pumping station Ogulin 2 is necessitated by the existing topographic conditions, which will not enable gravitational drainage of wastewater produced by the inhabitants gravitating towards collector A-5.3.1. The other two pumping stations (Ogulin 3 and Lomost) are required by the need to transport wastewater over the Zagreb-Rijeka railway.

The high quantities of sewage and stormwaters waters flowing from the town centre and settlement of Sv. Jakov to the south to the River Dobra have made this a priority area for development. Under the proposed system these waters will drain to Knot 94, and special emphasis has been placed on the capacity of the facilities here. A rainwater overflow has been designed as the optimal solution to deal with stormwater flows above the critical intensity of rcrit=15 l/s/ha

Figure 4.1 The Proposed Sewage System


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Figure 4.2 The Proposed Sewerage Zoning System


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Drainage Design - Zones B, C and D

Catchment areas B, C and D will be developed to supply sewer infrastructure to suburban settlements around Ogulin, with 27,685 m of canals and several minor pumping stations which will pump sewerage into catchment area A before disposal to the treatment plant. The details of the zones are as follows:

• Zone B This zone encompasses the area of the town north of the Zagreb-Rijeka railway, including the settlements of Cindri�i, Vrta�e, Petar Ogulinski, Drenovac, Podvrh and �egar. This zone is designed solely for the collection of faecal sewage with an expected number of inhabitants in the zone is estimated at 2,875. The backbone of this zone’s sewerage network is the collectors B-1 to B-3. The existing topographic conditions in the area necessitate the construction of two pumping stations of low capacity: pumping station Petar Ogulinski at the end of canal B-1.6 and pumping station Drenovac at the end of canal B-2.3. Pumping station Ogulin 1 is intended to be constructed at the end of collector A-1. This pumping station will transport the wastewaters from Zones B and C over the River Dobra.

• Zone C This zone encompasses the town area south of the Zagreb-Rijeka railway and

west of the River Dobra. The expected number of inhabitants is estimated at 2,555. The backbone of this zone’s sewerage network is the collectors C-1 to C-3. The zone is designed for the collection of faecal sewerage, however collectors C-1 and C-2 are expected to receive stormwater from the roads. The topographic conditions of the area necessitate the use of two pumping stations of low capacity: pumping station Prapu�e at collectors C-3, C-3.2 and C-3.3, and pumping station Bukovnik at collector C-5.. Effluent from this zone flows via gravity to Zone B and is pumped via pumping station Ogulin 1,into zone A before disposal to the treatment plant.

• Zone D This zone encompasses the settlements in the southwestern part of the town:

Otok Oštarijski, Kalca, Bošt, Brezik, Ku�ini� Selo, Sabljak Selo and Salopek Selo. The main collectors are collectors D-1 to D-6. The expected number of inhabitants by the end of the planned period is estimated at ca. 2,180. The entire sewerage network of this area is designed as faecal sewerage. The existing topographic conditions of the area necessitate the use of five pumping stations of low capacity: Salopek Selo, Sabljak Selo 1, Sabljak Selo 2, Bošt 1 and Bošt 2. At the end of this zone, the wastewaters are transported into Zone A through collector D-1 via gravity flow before disposal to the wastewater treatment plant.

The Waste Water Treatment Plant

A Membrane Biological Reactor (MBR) has been selected as the most appropriate treatment process for the Ogulin WWTP. The MBR WWTP process include two distinct operations:

• the Mechanical Section where effluent is treated by a number of physical steps to remove oils and grease and entrained solid material. This step is known as primary treatment; and

• the Membrane Biological Reactor (MBR) section where the effluent is treated by

exposure to bacteria activated sludge and the treated effluent is separated from the sludge by use of a membrane filter before disposal, which includes the secondary and tertiary treatment step.


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The plant will be constructed in two stages, which roughly aligned to these two process operations:

• Stage I will involved the construction and commissioning of the mechanical section of the plant for the treatment of primarily stormwater effluent from high flood risk areas of the Ogulin township before discharge to the groundwater environment. This plant will have a capacity of 600 l / sec.

• Stage II will involve the construction of the membrane biological reactor, which will

allow the treatment of faecal sewage. Upon the completion and commissioning of phase II a program will be initiated to allow the connection of residential and industrial premises to the sewer system described above for processed in the WWTP.


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Figure 4.3 Proposed WWTW Layout


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Table 4.1 Plant Design Parameters

Size of the plant (final stage) 15,000 PE Size of the plant (after completion of stage 1) 10,000 PE Level of treatment Tertiary treatment Hydraulic load - Phase 1 Qdry = 40 l/s Hydraulic load - Phase 2 Qrain = 60 l/s Time of retention in the rainwater retention tank Ca 10 min

Table 4.2 Characteristics of incoming wastewater

BOD5 250-300 mg/l COD 500-600 mg/l SS 300-350 mg/l Ptotal 11-12.5 mg/l Ntotal 50-55 mg/l NH4 N 30-32 mg/l

Table 4.3 Characteristics of the treated effluent

BOD5 2 mg/l COD 15 mg/l SS. 2 mg/l Ptotal 0.5mg/l Ntotal 10 mg/l NH4-N 3 mg/l Ammonia 1.5-4 mg/l Nitrates 50 mg/l NO3(reduced concentration - 60-70% of total N) Coliform bacilli - total 5,000 t.c./1000 ml Coliform bacilli – faecal 1,000 f.c./100 ml Faecal streptococci 1,000 f.s./100 ml

Phase 1 Mechanical Treatment

The mechanical section of the plant as discussed above consists of a number of process steps outlined in detail below:

• Rough screen Sewerage effluent from the Ogulin sewer will be fed through a closed channel to an automatic grid which is designed to separate the roughest content from raw wastewater, protecting the plants pumps and fine automatic sieves. The automatic rough grid will have a mesh size of 4 - 5 cm and will be fitted with a manual bypass for use in the event of a blockage. Waste separated out in the rough grid will be separated in the reception tank on ground level and disposed of at a municipal waste landfill.

• Feed Pumps It is planned to install 2 submersible pumps, one operational and an

installed spare, of 40 l/sec capacity in Phase I for lifting the influent 5 -6 m into the


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WWTP. Pumps of 450 l/sec will be installed to lift rainwater into the rainwater retention tank which is located at a level whereby gravitational flow can be used for the remainder of the plant. It is planned in Phase II of the project to install and additional 20 l/sec capacity pump and a 150 l/sec pump to the mechanical section of the plant.

• Rainwater Retention Tank A rainwater retention tank of 280 m3 volume for the

intake of wastewater during the rainy period and the period of peak inflow. A rainwater overflow will be built along the route of the main collector, whereby only the critical quantity of the rain will flow into the plant. The tanks is intended to be used to allow the retention of high intensity short duration rain events whose rate of rainfall within the catchment area exceeds that capacity of the plant. The tank provides a 10 minute retention capacity at the peak rate of the sewer system, which is somewhat longer than the usual retention time (5 minutes) given the sensitivity of the receiving environment.

• Automatic “fine” screens An automatic fine sieves of 2 - 3 mm screen size will be installed in reinforced-concrete closed canals. The fine sieve, contains a spiral press for pressing and dehydrating the material separated from wastewater. Such processed waste material will be stored in plastic bags and deposed of to the engineered landfill. In Phase I one fine automatic sieve with a capacity of 60 - 120 l/sec will be installed. In Phase II an additional sieve will be installed providing installed redundancy with one operational and one reserve sieve.

• Flowmeter The current and total flow will be measured by a flow meter canal (60

cm wide) with a venturi device. On the basis of the capacities of the pumps which raise wastewater onto the wastewater treatment plant, the selected size of the canal provides the recording of all amounts of the flown-through water.

• Station for the reception of contents of septic tanks It is proposed to install a station for

the reception of the sceptic tank effluent delivered by special utility vehicles for processing in the plant. This capability will be important in the initial developmental stages of the sewerage network when large numbers of properties are not yet connected to the network and maintain using their septic tank infrastructure. Facilities will be provided for cleaning of the trucks between leads with the effluent treated in the plant.

• Aerated sand and grease traps It is planned to install two parallel sand and grease

traps, one on line and one installed spare. The sand and grease traps are used to separate sand and other inorganic particles with a density higher than that of water by gravity sedimentation, and floating matter such as grease and other substances with density smaller than that of water by phase separation from the effluent. The sand trap is also used for preliminary aeration pre-treatment for subsequent process steps. The sand trap is a long partially partitioned concrete tank. Sand is transported to an outlet at the beginning of the sand trap, and pump to a sand classifier with separated water returned to the sand trap. The sand is discharged to a container and transported to the municipal waste facility. Floating matter and grease is collected, along with the calming of the surface in a pit at the end of the grease trap, from where it is disposed of to a solid waste facility.


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The treated rain water will be discharged to the groundwater environment at maximum rate of 180 l/s into a fenced sinkhole on the area of the plant.

Biological Processes

Mechanically treated wastewater is transported to the aeration tank with the mixers of the volume of 250 m3 (in stage I), and after that to the Membrane Bio Reactor (MBR), which represents the basic active unit of such a plant. The MBR integrates the biological reactor with a membrane system for ultra-filtration based on porous membranes. The MBR replaces the biological reactor, secondary sedimentation tank and sand filter in the conventional active sludge plant thereby significantly decreases the required space for the plant. The influent is first pumped into the anoxic zone of the reactor (denitrification), and then gravitationally flows to the aeration zone (nitrification). Aeration in the aerobic zone of the bioreactor is achieved through a diffuse aeration system installed at the bottom of the tank. Bacteria present in the biomass in the aerated tank (bioreactor) act to decompose the organic content of the sewerage, producing CO2 and water in the process. In order to perform this process, the bacteria require dissolved oxygen, nutrients, and a balanced pH. The nutrients are a constituent part of wastewater, while the fine aeration system in the bioreactor provides the necessary oxygen. The concentration of dissolved oxygen (DO) is also controlled by the PLC with the help of DO sensors installed in the bioreactor. There is also a pH sensor in the bioreactor, which controls the pH of wastewater. Treated effluent is separated from the sludge by membrane modules such as ZW-500, which perform the function of treatment in the way that treated wastewater is drawn through the membranes of this module by special (vacuum) pumps. The flow through the membranes and pressure on the membranes are constantly controlled. The net accumulation of sludge on the membrane surface is prevented by the periodic application of reversing the flow through the membrane (so-called "backpulse" process). The backpulse cleaning cycle uses treated wastewater, which is stored a backpulse tank. The tank is automatically filled with treated wastewater during normal operation of the plant, when the water level in this tank is low, the flow of treated wastewater is directed towards it, and when the tank is full the treated effluent flow is directed towards the discharge of the plant. The vessel membranes is cleaned by reversing the flow of the main pump system which is usually used for pumping treated wastewater towards the discharge, and thus the water from this tank, rinses the membranes and removes collected particles from them. Chlorine in the concentration of 5 mg/l may be added to this reverse flow and improves particle removal and membrane cleaning. The conventional frequency of such membrane treatment is every 10-15 minutes, in duration of 20-30 seconds, which is sufficient for continuous, long-term operation of the plant. On a less frequent basis the facility can be taken off line to allow for the automated membrane cleaning with a concentrated chemical solution for removal of collected particles. The selection of chemical solution for cleaning depends on the characteristics of wastewater that is treated, and therefore the kinds of particles that collect on the membrane.


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Due to a high concentration of dissolved oxygen in treated effluent and vacuum on the membranes, there is a tendency of release of dissolved oxygen from water. To prevent problems with air caught in the system or pipes, a separate vertical tank is provided to allow for degasification of the treated effluent and the air collects in top of the vessel and is automatically released through a system of valves. Turbidity of treated wastewater is constantly measured by a turbidimetre as increase of turbidity above the usual values usually means that a membrane was damaged allowing remedial action. The flow of treated wastewater which passed through the membranes is directed towards the discharge from the plant. This treated wastewater has a usually very low turbidity degree and it is possible, if desired, to disinfect it before being discharged from the plant, in accordance with the wishes of the owner or applicable legislation (in the case when the number of coliform bacteria in the effluent is limited). Besides CO2 and water, the process that takes place in the bioreactor also produces excess bacteria. Due to this, the sludge from the bioreactor is periodically removed with the help of the re-circulation pump, which ensures that the total mass of bacteria in the system is kept at a constant level. This way stabilized sludge is produced, which can be deposited on the location of the plant, dehydrated, and transported to the waste dump, or disposed of in a different manner. The following vehicles can arrive/depart at the location of the wastewater treatment plant:

- a utility vehicle specialized for the collection of waste dehydrated and “sacked” waste from the automatic grid - 2-3 times a week;

- a utility vehicle specialized for the removal of “containers” the removal of dehydrated and dry sludge to the waste dump - 2-3 times a week (in Phase II);

- a vehicle specialized for the transport of chemicals (powder in sacks) the transport of chemicals required by the technologies of treatment stages I and II, 1-2 times a month (in Phase II);

- official and private vehicles of the personnel (including maintenance personnel)

The contents of septic tanks shall also be transported to the Ogulin wastewater treatment plant by specialized vehicles.

Ancillary Facilities

The administrative-management facility will not be constructed in the initial stage so the necessary electrical equipment (the switchboard) will be placed in an enclosed facility where a fine automatic sieve and other equipment will be located. The site of the wastewater treatment plant shall be fenced by a two-meter high fence. In Phase I, in which only the mechanical part of the plant will be constructed, only that part will be enclosed with a fence. It is ca. 110 m long in the NW-SE direction, and ca. 80 m wide in the SW/NE direction.

The wastewater treatment plant and the main road shall be linked through the already existing route. This route shall be renovated for the approach of the vehicles engaged in the maintenance of the wastewater treatment plant and paved with asphalt.


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A connection pipeline, running from the built collector, i.e. from the manhole which ends that section, to the incoming manhole at the location of the wastewater treatment plant shall be placed in such a way as to ensure unhindered transport of wastewater into the treatment process. The connection pipeline will be ca. 150 m long, 800 mm in diameter, made out of ACC (asbestos cement pipes, just like the 2,000 m already built), of a longitudinal sloping of ca. 1.5‰.

Connections onto the public water supply network will be provided for the purposes of technological-sanitary needs (automatic rinsing of grids and sieve, rinsing of sand, etc, preparation of chemicals (Phase II - sludge dehydration, etc, ongoing maintenance of the facilities and the environment and sanitary needs of the personnel and maintenance workers in the administrative-maintenance facility and other facilities of the plant) for which a supply of up to 2.50 l/s at a minimum pressure of 3 bars is required, and for the outer hydrant network which will require 10.00 (2 × 5.0) l/s and a minimum pressure of 3 bars. The water supply network has already been brought to the location of the plant, along the road by the collector.

The telephone network will be connected upon the construction of the administrative-maintenance facility. The facilities of the Ogulin wastewater treatment plant shall be connected to a 380 V / 50 Hz power supply network, i.e.:- Peak load in Phase I: Npeak=42.0 kW4 with PEAK LOAD IN PHASE I (biological treatment):of 170 kW and PEAK LOAD IN PHASE II (completed plant):of 300 kW.

Receiving Waters

The treated water will be discharged to the groundwater environment through a sinkhole on site in accordance with the study “Geomenhani�ko-geofizi�ki istra�ni radovi -URE AJ ZA PRO� IŠ� AVANJE OTPADNIH VODA GRADA OGULINA” (‘GeoKon-Zagreb’, Zagreb, no. E-090-99, October 1999). The sinkhole located on the south-western part of the location of the wastewater treatment plant is suitable to receive the treated wastewater. The tests have shown that the ground consists of highly permeable layers up to the depth of some 20 meters. The absorption quality in the above-mentioned sinkhole is high enough (water currently disappears in the underground without slowing down). Furthermore, on the area of this sinkhole there are more cavernous zones, suitable for the construction of absorbing wells.

Analysis of Alternatives

Alternative Locations

The site was selected a for the construction of the proposed facility is located on the Galge area, south-east of Ogulin and north-east of the settlement of Otok Oštarijski. The plot, shaped as an irregular polygon, will cover a total area of ca. 6,900 m2. That land has to been earmarked by the local authority for the development of the facility primarily due to the presence of the on site sinkhole for the disposal of treated effluent. However factors such as a topographical situation which facilitates the maximum use of gravity flow and the fact that’s the site has a buffer distance of approximately 2000 m to the nearest

4 Peak loads of subsequent and final phases are based on “Idejno rješenje ure aja za pro�iš�avanje otpadnih voda Ogulina”, Hidroprojekt-ing Zagreb, 1997.


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sensitive receptor also lead to the conclusion that the site is appropriate for the development of the plant.

Alternative Technologies

Wastewater treatment is divided, with respect to treatment effect, into three groups as follows:

- Primary treatment Primary treatmeat includes procedures of mechanical or physical-chemical processing, which primarily remove suspended matter from wastewater. Chemically enhanced primary treatment (CEPT) can be given as an example of physical-chemical treatment (i.e. increased elimination by dosing chemicals as flocculants and coagulants in the form of metal salts, iron or aluminium.

- Secondary treatment Secondary treatment includes biological procedures by which the contents of biologically decomposable carbon compounds, expressed and measured as BOD5, are long-term reduced.

- Tertiary treatment (long-term treatment) If in addition to carbon compounds elimination, the removal of nitrogen and phosphorus nutrients from wastewater is required as well, tertiary or long-term treatment is implied.

After consideration of the very demanding local conditions, including high requirements of effluent standard, the following is considered the most suitable construction option for the sewerage system of the town of Ogulin:

1. design and construction of the sewerage network for wastewater removal (faecal wastewater, industrial/small enterprise wastewater, and only the most polluted stormwater in the central section of the town of Ogulin), in accordance with ATV guidlines A118 and DIN 4033.

2. design and construction of the wastewater treatment plant in accordance with ATV guidlines A131 for tertiary treatment level

The Ogulin sewerage system has been designed as a single technical and technological unit and all the relevant local conditions, legislative regulations (The Water Act, The Environmental Protection Act etc) have been taken into account during its design, as well as the feasible wastewater treatment technologies. In addition the required guidelines have been followed to guarantee the optimum for the following: - drainage system (separate and combined systems) - drainage method (gravitation drainage and pressure drainage) - method of relieving precipitation waters - optimizing facilities relevant for wastewater drainage (pumping stations, overflows,

rainwater basins) - rational dimensioning of the network and the facilities according to the ATV

guidelines (guidelines of the German Association for the Water Environment) and the current DIN standards

- carrying out research work (hydrogeological, geotechnical)


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- taking into consideration all the relevant local conditions (sewerage routes, locations of the facilities)

- honouring all specific construction conditions (particularly water rights conditions relating to the criteria for the discharge of treated wastewater and minimal flowing speeds)

Honouring and consistently following the above-mentioned criteria and guidelines shall, together with constant control, enable the preparation of a high-quality project, which is essential to satisfy the cost-efficiency and environmental protection objectives. A number of process options were investigated in the The Conceptual Design for the Wastewater Treatment Plant for the City of Ogulin 2002 undertaken by Vodovod I Kanalizacija d.o.o. The report analysed a number of design for the plan, these were: • Option 1 - Active sludge with simultaneous nitrification-denitrification; • Option 2 - Active sludge with a SIMPLEX interrupted denitrification; and • Option 3 - Membrane bioreactors (MBR). Each of these process options is outlined in more detail below. The report also considered the Sequencing Batch Reactor and the Physical-Chemical procedure however these options were ruled out at an early stage as they would not achieve the wastewater discharge standards that will be required of the proposed plant. Option 1 - Active Sludge With Simultaneous Nitrification-Denitrification Plant This process option involves the follow step procedures:

• incoming grid; • pumping station with submersible pumps; • “fine” sieves; • Sand traps and grease trap; • Septic tanks contents receiving station; • Anaerobic phosphorus removal tanks; • Anoxic aerobic nitrification-denitrification and sludge stabilisation tank; • Secondary sedimentation tank; • Sludge densifier; • Sludge dehydration; • Sludge re-circulation pump stations; • Sand filter; • Active carbon filter; and • UV disinfection.

Option 2 - Active Sludge With Simplex Interrupted Denitrification Plant

This process option involves a similar process steps to those described above however the ‘Anaerobic phosphorus removal’ and ‘Anoxic aerobic nitrification-denitrification and sludge stabilisation’ steps are replaced with a SIMPLEX plant where nitrification and denitrification occurs in an aerated tank with a secondary sedimentation tanks provided to facility sludge re-circulation with an additional dephosphatization by addition of ferric chloride salts.

Option 3 - Membrane Bioreactors Plant (MBR)


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The operation of this process option is described in more detail in WWTP section of the report. Uses a many of the process steps described in option 1 however biological treatment and sludge separation steps are achieved in the one process vessel, the MBR, which is capable of treating effluent to a tertiary standard without additional steps such as a sand filter, active carbon filter and UV disinfection. Comparison of Options The conceptual design report compared the typical treatment efficiencies of each of the process options discussed above. The results of this comparison is shown below in Table 4.5 below which shows that Option 3 the MBR process is capable of achieving a higher level of effluent treatment across a broad spectrum of effluent quality parameters particularly in the total number of coliform and faecal coliform bacteria.


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Table 4.5 Effect of reduction of waste substances (%) for each process option

TREATMENT METHOD

INDEX Option 1 - Active sludge with simultaneous nitrification-denitrification plant

Option 2 - Active sludge with SIMPLEX interrupted denitrification plant

Option 3 – Membrane bioreactors (MBR) Plant

BOD5 97.5 97.5 99 COD 97.5 97.5 97.5 S.S. 97 97 99.4 N 88 88 88 P 95 95 96 TC/l (5x105) (5x105) (5x104)FC/l ( 104 ) ( 104 ) (103)

The conceptual design report goes on to analyse each process options by allocated a weighted ranking against a number of criteria with a view to determine which option was most applicable to the Ogulin plant. The results of this comparison is shown below in table 4.6 Table 4.6 Weighted Comparison of the process options.

Factor Weighting Option 1 Option 2 Option 3 Ranking Weighted

ranking Ranking Weighted

ranking Ranking Weighted

ranking Efficiency of treatment

20 4 80 4 80 4 80

Simplicity of the plant

10 3 30 3 30 4 40

Adaptability to changes of load

10 4 40 3 30 4 40

Environmental impact

15 3 45 3 45 4 60

Construction costs 15 3 45 3 45 3 45 Annual operating costs

20 4 80 4 80 3 60

Stages of construction

10 4 40 3 30 4 40

TOTAL: 360 340 365

Where: 4 – very good; 3 – good; 2 – acceptable; 1 – poor As such it can be seen that whist each of the plants overall performance is broadly similar, Option 3 – Membrane bioreactors (MBR) Plant – was considered to be most applicable to the Ogulin area as the plant is:

• broadly similar for a capital cost and operating cost perspective to the other process

options; • capable of achieving a superior levels of effluent treatment to the other process options

which, given the sensitivity of the receiving environment, was considered to be of key factor in the selection of this process option;

• able to avoid all problems related to poor sludge sedimentation which may occur in the conventional process;

• resistant to the changes of hydraulic and organic load, keeping the high quality of effluent in the process;

• suitable for bioreactor operation with significantly larger concentrations of biomass than the conventional plants, where the limitation is conditioned by sludge sedimentation.

• Capable of a high level of automatization and as such is likely to be simple to operate; and


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• known to have an ability to quick adaptation to oscillations of quantity of influent.


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Impact Assessment and mitigation

Introduction

This section evaluates the impacts associated with the construction, operation and eventual decommissioning of the proposed sewerage system, comprising of the wastewater disposal systems, the sewerage network, the wastewater treatment plant, the sludge treatment system and the treated wastewater discharge sites.

The Sewage Network

Impacts During Construction

Impacts arising during construction of the sewerage network will be primarily restricted to physical impacts arising from digging of the sewerage trenches (including noise, dust, and impacts to traffic) and impacts associated with the risk of physical damage to neighbouring facilities and installations. Other impacts have been avoided by designing the drainage system profile for optimal functionality (ie minimal acceptable number of pump stations) and care has been taken in selection of all pipeline material to ensure water-tightness. Careful planning and scheduling of the works will be undertaken to minimise impacts arising from construction disturbance. Prior to construction start, the contractor will be obliged to prepare a project plan, for example to control noise originating from the construction site to within permitted ranges. The contractor will also be obliged to take protective measures on the construction site to prevent atmospheric pollution, and to ensure transport of excess excavated material under supervision (eg prevent excessive loading of vehicles and, when necessary, dampen excavated material prior to vehicle exit from the construction site). The contractor will also be obliged to supervise and maintain machinery and vehicles, to ensure that exhaust fumes concentrations are within permitted values. All sewerage ditches will also be carefully filled in and the environment will be restored to its original state after construction.

Impacts during Operation

Operation of the sewerage network is not expected to result in any significant adverse environmental impacts. Risks of infiltration of wastewater into the groundwaters following damage or poor construction of sewer pipelines or explosion risks arising from natural gas entering into the sewerage system will be managed through good maintenance practices. The quality, composition and quantity of wastewater entering the plant, and the high sensitivity of the local environment have also dictated the selection of the wastewater drainage pipelines, and only high-quality polyester pipes (or the like) will be used. In general, properly ventilated sewerage systems have few significant problems with odours, although the typical smell of wastewater may be detected sporadically. More unpleasant odours may arise when industrial wastewaters contain particularly toxic chemicals, or are retained in anaerobic conditions in the pipelines; or when sludge deposition within the pipelines occurs as a result of low wastewater flows. Long sewers with insufficient ventilation or too low flowing speed are particularly known to suffer from anaerobic reduction of sulphates, resulting in a strong smell of sulphide amongst other compounds, but this can be controlled by adequate grading of the system and good sewer maintenance. Thus the proposed


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sewerage system has been designed to minimise odours by keeping the wastewater flowing and avoiding potential areas where the wastewater would be trapped by:

• providing sufficient ventilation in the sewerage system; • designing the system with a suitable minimum fall and using short pressure pipelines with

short retention times in the pumping station to prevent sediments developing in the sewerage system

• avoidance of unpleasant wastewater agitation by avoiding sudden changes in the sewerage system gradient and using as few pumping stations as possible.

• Preventing unpermitted connection of problematic waste substances and wastewater (eg from slaughterhouses, food processing industry, septic tank sludge)

• Ensuring that wastewaters with the potential for strong odour are connected to the sewerage system only after pre-treatment

• addition of lime and other chemicals for treatment.

The Waste Water Treatment Plant

The WWTP has been designed to allow disposal of rainwaters under most storm conditions, and and care has been taken to design protection of concrete and equipment from the corroding effect of wastewater. Key impacts that have required to be addressed include the liquid wastes; solid wastes; odours and noise impacts. Potential Impacts during construction and operation of the WWTP are shown in Tables 5.1 and 5.2 respectively, whilst issues related to odour control are discussed further below.

Odours Treatment

Biological treatment of wastewaters and the associated intensive aeration, can lead to odours and air emissions primarily from the release of volatile substances (such as solvents) and aerosols (tiny drops of wastewater in air) from the aeration basins, as well as from by-products of anaerobic decomposition in the aeration basins or the waste sludge treatment. Potential sources of odours are shown in Table 5.3 below:

Table 5.3 Potential sources of odours

WASTEWATER DRAINAGE WASTEWATER TREATMENT SLUDGE TREATMENT at wastewater connection place in the sewerage in pressure pipeline at the end of the pressure pipeline spindle drag pump surface pumps (turbines) retention area in pumping station in access shafts turbulent places in general

grid equalization basins, rainwater overflow basins sand filter aerated sand filter grease and oil separator primary sedimentation tank reaction basins neutralisation basins heapers and other equipment (devices) aeration basins pool drain pipes secondary sedimentation tanks filters lagoons and oxidation ditches digesters -third treatment stage

thickening sludge silo digesters incineration thermal, chemical conditioning filter presses, chamber presses, suction filters sludge lagoons sludge drying beds irrigation fields composting disposal

The significance of any environmental impact arising from such odours and emissions is dependent on the exposure of sensitive receptors (eg people) to the smells, and is a


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combination of smell intensity and effect duration. The intensity is itself affected by the following: - the composition of the raw (untreated) wastewaters - the technological treatment process used - the type of sludge treatment - water and air temperatures - the level of maintenance of the plant The primary mitigation for odours has been the siting of the plant an adequate distance and downwind of Ogulin to reduce exposure of the local population. In addition the aeration basins and primary sedimentation tanks will be covered to reduce emissions, and sludge dehydration and thickening will also be undertaken in an enclosed environment. Waste matter from the grid, sand filter and grease trap can also result in odours, and to mitigate against this such wastes will be removed regularly in enclosed compact units, as will stabilised and dehydrated sludges .


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Table 5.1 Potential ImpactsArising During Construction of theWWTP

Receptor Potential Impact Proposed Mitigation SignificanceLand Use The proposed site is undesignated and is currently not used for any specific purpose The

development of the treatment workswill however precludeany other land use for the site.The chosen site is well outside the existing townand in an area that has beenzoned for such use, with no recognised ecological, agricultural or culturalvalue. There is plenty of land near the town for future developments. Nofurther mitigation isproposed.

Not Significant

TerrestrialEcology

Existing habitats present on the site are primarily secondary regrowth and ephemeral scrub,although the invasive plant species Japanese Knotweed was present on several areas of the site. Theproposed project will result in habitat loss, aswell asdisturbance to flora and fauna

Whilst the habitats and species present at the proposed WTW site arecommon in the Ogulin area, the proposed project site will be landscapedfollowing construction, using approved and ecologically appropriatespecies. No further mitigation is proposed.

Not Significant

Aquatic Ecology N/A N/A N/AWastemanagement

Construction of the facility will result in a range of standard construction waste, as well as theproduction of significant amounts of spoil

Construction wastes will be disposed of to an approved landfill. Spoil will bereused on site in landscaping and bunding.

Minor adverse

Air quality Construction can result in generation of dusts and emissions from diesel generated engines.However the location of the site over2km from the town means that the severity of such impacts isminimised.

Impacts will be minimised by use of good working practices. Not significant

Noise Construction works will generate acertain amount of noise Impacts will be minimised by use of good working practices.Water Construction works can lead to increased run off of spoil and other pollutants. Care will be needed

to ensure that good working practicesminimise impacts.All work and traffic surfaces will be provided with a drainage system, andregular maintenance, i.e. washing of such surfaces, wil l be ensured.Water remaining on all (also traffic) surfaces will be avoided byapplication of adequate slopes and watertrap shafts.

Minor adverse

Cultural andhistoricalheritage

The site is not located in an area of cultural or historic heritage.No impacts are expected. No mitigation is required Notsignificant.

Visual amenity The site is located in asecluded areaaway from local sensitive receptors. Landscaping will beundertaken as part of theconstruction works Minor adverseTraffic Construction generated traffic could lead to local disturbance work Impacts will be minimised by careful scheduling and the use of good working

practices.Minor adverse


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Table 5.3 ImpactsDuring Operation (excluding odour)

Issue Potential Impact Proposed Mitigation SignificanceLand Use Odours from theproposed plant may precludeadjacent sites from futuredevelopment. The chosen site is well outside the existing town and in an area that has been zoned

for such use, with no recognised ecological, agricultural or cultural value. There isplenty of land near the town for future developments. No further mitigation isproposed.

MinorAdverse

Ecology The aquatic ecology of the karst ecosystem is both unique and fragile. Treatment ofwastewaters prior to disposal will result in a net ecological benefit to the unique localecosystems.

The proposed system has been designed with sufficient capacity to allow the overflowif needed. The improvements that will arise from the scheme will not require anymitigation. No further mitigation suggested.

Majorbeneficial

Surface &Groundwaters

Local water resources are highly valued and operation of the plant will greatly improveexisting conditions

The allowable effluent standard with regard to this highly sensitive receivingenvironment (the underground streams in the karstic soil) has dictated the selection ofthe wastewater treatment technology, which has been designed to achieve tertiarylevels of treatment in accordance with the National Water Protection Plan. To protectgroundwaters from wastewater seepage, watertight connections of channels,manholes and tanks must be built.

Majorbeneficial

SolidWastes

Treatment and the final disposal of waste sludges is an issue for wastewater treatment plantsand the selection of an appropriate location for the ultimate sludge disposal is critical toprevent secondary environmental pollution. Waste sludge, (especially active sludge with itsmixed culture of micro-organisms), has the capacity of binding various organic and inorganicsubstances, many of which may be toxic (heavy metals, organic chemicals) and can lead toboth bacteriological and chemical pollution, resulting in further risks to groundwater.Esti mated sludge quanti t i es (20% dry matter), are 5.7 m3/d for the Phase 1 plant and7.7m3/d for the Phase II

To mitigate this, waste materials from the screens and sand traps will be collected andtransported (in an enclosed environment to prevent further odour issues) on a regularbasis to a Class 1 disposal site in line with the Regulations on Waste HandlingConditions. Oils and fats from the fat trap will also be collected in closed storagesand transported for incineration, in line with the Regulations on Waste Types(Official Gazette 27/96).Stabilized sludge, drained from excess water, will becollected in special storages and transported to a disposal si te of I. class, in linewith the Regulations on Waste Handling Conditions (Official Gazette 123/97).Prior to disposal the composi ti on of the stabl i l i zed sludge eluate wi l l bedetermined in l ine wi th the Regulations on Waste Handling Conditions.

Minoradverse

Noise The operational facility will use either compressors or blowers for aeration and this combinedwith the operation of the various mechanical parts of the plant as well as the “wastewater”medium itself will result in the generation of round-the-clock noise. The use of an enclosedsystem will however help ensure that permitted daily and nightly noise limit levels of 55and 45 dBA respectively at the site boundary will not be exceeded.

To meet local permitting requirements, the plant has been designed to ensurethat noise levels at the boundary do not exceed the highest permitted daily andnightly levels of 55 and 45 dBA respectively. To ensure this, the plant has beendesigned with all machinery producing high-intensity noise placed in closedstructures, with specific noise protection measures including roofing of the facilities(basins), and the use of elevated basin walls, protective walls and protective dams.

Minoradverse

Culturalheritage

N/A N/A N/A

Visualamenity

An area of green belt will be established around the site. This will also help filter air pollution N/A Notsignificant

Traffic Disposal of wastes will result in some traffic movements, but these will be less than under thecurrent situation

N/A Minorbeneficial


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As described above, and in order to protect the environment from unpleasant odours, key areas of the plant parts and inflow sewerage pipelines will be covered. These will include both the water line (pumping station, screen, sand trap, primary sedimentation, aeration basins, secondary sedimentation, tertiary treatment level) and the sludge line (thickening, stabilization, conditioning, drainage). In addition air quality at the site boundary line of the plant location will be monitored to ensure that it doesn’t exceed 24 hour limit levels as follows:

• Ammonium 70 g/m3

• Hydrogen sulphide 2 g/m3

• Mercaptans 1 g/m3

• Sulphur-dioxide 80 g/m3

Overall, odours are not expected to adversely effect sensitive receptors in the vicinity of the plant. Aerosols are colloidal systems in which solid or liquid substances are finely dispersed in the form of gases. The size of most particles is between 0.003 and 50 . Aerosol develops due to the turbulence and agitation of the surface layer of wastewater (e.g. surface aeration with turbines), but also at incoming and outgoing basin baffles, aeration sand filter, filters, and particularly during wastewater rains. Recent tests carried out by the U.S. Environmental Pollution Agency (EPA) indicated potential threats from aerosol borne wastewaters represent no infection risk to neighbouring populations but can become a local sensitivity. A number of aerosol protection measures have been included within the scheme including use of enclosed pipelines rather than open sewers, use of protective walls, and vegetation particularly at surface aeration (turbines, mammoth rotors) and use of a fully roofed basin.

Health and Safety Measures

The proposed project will be implemented in accordance with all the conditions of safety at work, which including traffic safety, the arrangement of working areas, ventilation, fire prevention and environmental protection. During construction and operation workers will be provided with sanitary facilities containing a shower, a sink and a toilet.

Impacts during decommissioning

The wastewater treatment plant is intended for long-term use, and the site will be decommissioned in accordance with applicable standards and legislation at the time of decommissioning. Impacts of decommissioning are considered of minor significance.

Impacts During Abnormal Operation

Hazardous substances in the wastewater can adversely affect the functioning of wastewater treatment works and a long-term functioning break of the biological unit in the plant could result in insufficiently treated water being released into the underground streams. Whilst no significant quantities of potentially hazardous materials (acids, alkalis, etc) will be used during operation of the plant, there is always a risk of hazardous materials entering the wastewater stream as a result of industrial accidents upstream. To avoid such a risk, wastewater influent quality will be continuously monitored at the plant, and all industries and small enterprises connected to the central plant, will be required to have the approval of "Vodovod i kanalizacija" d.o.o. (Water Supply and Sewerage), the company for


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provision of municipal services, or the manager of the central plant, prior to a connection or any change in the technological process. Local industries will also be required to work out a system of measures to ensure a timely break in draining wastewater toward the Ogulin plant should an accident occur, whilst the stormwater overflow would provide additional protection at the plant. Even should any of the units break down due to a partial or complete loss of biological activity, the plant construction using four independent modular technical units (parallel structures), will allow the facility to continue in operation. Automatic backup power generation is also provided, together with a system of permanent monitoring of quality and quantity of inflowing/outflowing wastewater. The risk of a fire from the operational facilities is generally considered to be low, and no especially flammable materials will be used on the site. A hydrant network has been included in the project design and fire extinguishers will be available in enclosed and roofed facilities.


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Environmental Monitoring, Management and consultation

Overview

During construction and subsequent plant operation, it is necessary to monitor the environmental status of the project in order to determine potential unfavourable and undesirable impacts. Monitoring results will be used for possible additional environmental protection measures, in cases of increased quality requirements for parts of the environment, or the inefficiency of planned protection measures. An Environmental Management Plan will be developed for the project, which will further outline environmental protection measures to be used during construction and use, and suspension of use and/or removal of the construction, including a proposal of measures for prevention and mitigation of potential ecological accidents.

Surface waters

Surface waters will be monitored at four locations (upstream and downstream of the treated water discharge locations, and at the plant entrance and exit) to ensure appropriate levels of environmental protection and ensure that the plant is operating efficiently. Surface water monitoring will also be carried out at the spring sources identified at the tracer tests and the plant will liaise with Croatia Water with regard to the monitoring of river water quality on the Dobra River downstream of Ogulin.

Water samples will be collected in proportion to the 24-hour flow of water, and sound laboratory practices will be used to preserve samples in accordance with the requirements of the State Office for Standardization and Metrology. Effluent waters will be tested at least weekly and stormwater discharges will also be monitored regularly on an as and when required. Indicators will include:

• water flow (m3/s) • water temperature (°C) • pH • dissolved oxygen (mg O2/I) • dissolved matter (mg/l) • five-day biochemical oxygen demand (mg O2/I) • chemical oxygen demand (mg O2/l)

• total nitrogen (mg N/l) • total phosphorus (mg P/l) • total chromium (mg Cr/1) (only in wastwater) • total oils and fats (mg/l) • mineral oils (mg/l

Groundwaters

Groundwater quality monitoring will be undertaken to determine the potential impacts of the plant on groundwater quality using three piezometers located within the boundaries of the plant’s plot, one upstream of the plant and two downstream of the plant in the direction of the flow of groundwater along the boundaries of the plot. The piezometers will be located deep enough to enable monitoring water quality in upper water-bearing layer. Groundwater monitoring will be undertaken on a monthly basis following the standard method prescribed by the State Office for Standardization and Metrology. Monitoring will start at least a year prior to the start of plant operation, in order to determine the state of groundwater quality, not influenced by the plant.Piezometers will register the following


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data5:

5Listed parameters have been specifically selected to determine the influence of the proposed plant on the groundwater;

therefore, all parameters typically used to monitor groundwater quality are not included


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• water level (m) • water temperature (°C) • turbidity (mg SiO2/l) • pH • KmnO4 demand (mg O2/l) • electroconductivity ( S/cm)

• ammonia (mg N/l) • nitrites (mg N/l) • nitrates (mg N/l) • mineral oils (mg/l)

Sludge Quality

To safely monitor potential unfavourable impacts on the environment, it is necessary to permanently monitor the contents and concentrations of hazardous substances in the processed sludge. The monitoring program will include the following parameters:

• daily quantity of processed and dehydrated sludge (m3/d) • daily mass of dry matter in sludge (t/d) • concentration of total nitrogen (mg N/kg of dry matter) • concentration of total phosphorus (mg P/kg of dry matter) • concentration of total potassium (mg K/kg of dry matter) • concentration of cadmium (mg Cd/kg of dry matter) • concentration of chromium (mg Cr/kg of dry matter) • concentration of lead (mg Pb/kg of dry matter) • concentration of zinc (mg Zn/kg of dry matter)

• concentration of harmful organic substances (PCB, HCH, etc.) (mg/kg of dry matter)

Initially sludge samples will be taken on a monthly basis from tanks for stabilized, dehydrated sludge prepared for transport. Reference parameters for permanent sludge monitoring will be determined one year after connection of all present water users to the plant.

Air Quality

The influence of the plant on the surrounding air quality will be monitored at two stations located along the boundaries of the proposed plant. The air monitoring program will monitor the following parameters:

• direction and velocity of wind (m/s), • air temperature (°C), • air humidity (%), • precipitation (mm/min),

• ammonium (ug NH3/m3), • hydrogen-sulphide ( g H2S/m3), • mercaptanes ( g C2H5SH/m3), • sulphur dioxide ( g SO2/m

3)

Samples will be tested at least quarterly according to the methods prescribed by the Regulation on the Recommended and Limit Air Quality Values (The Official Gazette, Narodne novine, No. 101/96). Monitoring will commence at least a year before the plant starts functioning in order to determine the impact of other air pollutants surrounding the plant.

Noise

Noise levels will be recorded at the western boundary of the plant to ensure that the limits permitted for industrial areas are not exceed in accordance with Article 6 Paragraph 3 of the Regulations on the Highest Permitted Noise Level in People’s Living and Working Environment (The Official Gazette, Narodne novine, No. 37/90). The measuring of noise level (dBA) shall be performed night and day during working hours. Four measurements a year are suggested, starting one year before the plant starts functioning.


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Environmental Policies

During the implementation of the construction, the project proponent will implement all environmental protection measures described in this study and in the technical documentation. "Vodovod i kanalizacija"d.o.o. (Waster Supply and Sewerage) will also, during all activities, comply with the existing regulations of the Republic of Croatia, particularly in the area of occupational protection, environmental protection, construction, water and air protection.

Public Consultation

Vodovod i kanalizacija has reported no difficulties to date with the public regarding the construction of the sewerage and wastewater treatment plant. The project team has taken a positive approach towards environmental protection, and has informed the public on a regular basis about the intentions of the company related to the construction of the sewerage system. Local residents are reported as regarding the construction of the collector with the adjoining network as being in the interest of the town and the surrounding settlements, and whilst some minor concerns are expected to arise during the construction of the wastewater treatment plant the site is visually isolated and located far enough from town zones for the residential facilities to be distant enough from the plant.

Public consultation efforts to date include notices by the local authorities of the City of Ogulin in the announcements section of Karlovacki List, dated 23 July 2001, inviting comments and concerns from local population to the proposed project. As confirmed by the official correspondence from the officials of Karlova�ka �upanija (Karlovac county), no critical concerns or complaints have been raised by the population concerned.

Several public consultation meetings took place in 2001 and the results of these confirm the above statement. In June 2005 the project team followed up this work with a study carried out in the project impact area which raised the following questions:

1. please list any environmental concerns that you have in connection with the proposed completion of the sewerage system and WWTP for the Town of Ogulin

2. please list any environmental benefits that you see this project would bring to the area

3. what level of further environment-related information would you like to have regarding this project?

4. which local tools/sources of information on the project would you prefer, e.g. TV, newspapers, local government websites, other?

The results of the questionnaire are reported in the “willingness to pay study” and showed strong support for the project.

An ongoing program of public information is planned for the project. This will involve the following raising awareness and environmental education for different population groups in the area (e.g. existing households, schools, businesses, NGOs, general public) using a range of methods such as public meetings, newspaper adverts, radio and TV programs and announcements, information posters, flyers/leaflets, etc.


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legislative References

- Regulation on environmental impact assessment (Official Gazette 34/97, 37/97) - Environmental protection act (Official Gazette 82/1994) - Construction act (Official Gazette 52/99) - Occupational protection act (Official Gazette 59/96) - Water act (Official Gazette 107/95) - Standardization act (Official Gazette 55/96) - Fire protection act (Official Gazette 58/93) - Waste act (Official Gazette 34/95) - Nature protection act (Official Gazette 54/76 and 41/83) - Physical planning act (Official Gazette 30/94) - Noise protection act (Official Gazette 17/1990) - Regulations on waste types (Official Gazette 27/96) - Regulations on package waste handling (Official Gazette 53/96) - Regulations on waste handling conditions, (Official Gazette 123/97) - Regulations on occupational protection for work rooms and auxiliary rooms (Official

Gazette 6/84) - Regulations on highest permitted noise levels in which people work and live (Official

Gazette 37/90) - Regulation on water classification (Official Gazette 77/98) - Regulation on hazardous substances in water (Official Gazette 78/98) - Regulations on limit values of indices, hazardous and other substances in wastewater

(Official Gazette 40/99) - National water protection plan (Official Gazette 8/99)

- Decision on enactment of physical planning program of the Republic of Croatia (Official Gazette 50/99) - B. Bakari� et al, Waste act, Basel Convention, Regulations on waste types, with comments, IZOS, Zagreb, 1996 - Environmental protection regulations, Zagreb, 1997

- Physical plan of the Ogulin municipality - Preliminary design for wastewater treatment plant of Ogulin (I. phase - construction), study for location permit (Hidroprojekt-ing, 1999) - Study for issue of location permit for sewerage network (section A) (Aauacon, 1999) - Geomechanical-geophysical investigation works (Geocon, 1999)

- DIN standards

DIN 1045 - Concrete and reinforced concrete, dimensioning and construction DIN 1055 - Loads for structures, traffic loads, wind loads (part 4) at structures which are not subject to dynamic impacts DIN 1055 - Loads for structures, traffic loads, snow and ice loads (part 5) DIN 4281 - Concrete for drainage facilities (building, requirements, investigation)


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DIN 4226 — Addition for concrete, additions fro water impermeability, terms, (part 1) labels and requirements DIN 17440 — Stainless steels, technical conditions of delivery for sheet-metal,

thermal strips, wire, drawn wire, concrete iron DIN 19551 — Treatment plants, rectangular basins with a scraper, (part 1) principal dimensions DIN 19551 - Treatment plants, rectangular basins with strip scrapers for sludge, (part 2) principal dimensions DIN 19551 - Treatment plants, rectangular basins as sand traps with suction (part 3) scrapers, principal dimensions

DIN 19551 — Treatment plants, rectangular basins with suction scrapers, principal (part 4) dimensions DIN 19552 — Treatment plants, circular basins with a sludge scraper, (part 1) principal dimensions DIN 19552 — Treatment plants, circular basins with a suction scraper, principal (part ) dimensions DIN 19552 — Treatment plants, circular basin as a sludge thickener, (part 3) principal dimensions DIN 19553 - Treatment plants, trickling filters with a rotating distributor DIN 19554 - Treatment plants, screen facility with a flat screen, (part 1) principal dimensions DIN 19554 - Treatment plants, screen facility with an arched screen, (part 2) principal dimensions DIN 19554 - Treatment plants, screen facility with a counterflow screen,

principal dimensions DIN 19556 - Treatment plants, open channel with sluices, principal dimensions DIN 19557 - Treatment plants, minimum filling for trickling filters, (part 1) requirements, investigations, delivery, installation DIN 19558 - Treatment plants, overflow stills and floating wall, consolidation,,

principal dimensions and discharge DIN 24420 - List of replacement parts, general (part 1) DIN 19569 - Engineering basis for facilities and technical equipment (structures (part 2)

and facilities for thickening and separation - screens, sieves, sand traps, fat traps, sludge thickeners)


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