annex1 hydraulic calculation of the sewer network

Ujësjelles Kanalizime Qytet Shkoder Kreditanstalt für Wiederaufbau

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WATER & SEWERAGE PROJECT SHKODRA

FEASIBILITY STUDY

PROJECT CONCEPT DRAFT REPORT

ANNEX No. 1Hydraulic Calculation of the

Sewer Network

June 2006

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TABLE OF CONTENTS

1 METHODOLOGY..............................................................................................................1

1.1 Preparation of the Hydraulic Calculation...................................................................1

1.1.1 Topographic Survey..............................................................................................1

1.1.2 Sub-system, Main and Sub-Catchment Areas......................................................1

1.2 Hydraulic Calculation of the Sewage System...........................................................2

1.2.1 Design Criteria.......................................................................................................2

2 RESULTS..........................................................................................................................5

2.1 Existing Sewer Network without Sewer Extensions..................................................5

2.1.1 Existing Situation 2006..........................................................................................5

2.1.2 Future Situation 2015 and 2030............................................................................5

2.1.3 Conclusion.............................................................................................................6

2.2 Existing Sewer Network with Extension Areas for 2030...........................................6

2.2.1 Sewer Network Extensions...................................................................................6

2.2.2 Results..................................................................................................................6

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TABLES

Table 1-1: Domestic Sewage Production Rates.......................................................................3

Table 1-2: Specific Large Water Consumer..............................................................................3

Table 1-3: Extraneous Water Flow...........................................................................................4

APPENDICES

Appendix 1- 1: Hydraulic Calculation of the Sewer Network – Existing Situation 2006

Appendix 1- 2: Hydraulic Calculation of the Sewer Network – Existing Sewer Network, Situation 2015

Appendix 1- 3: Hydraulic Calculation of the Sewer Network – Existing Sewer Network, Situation 2030

Appendix 2- 1: Hydraulic Calculation of the Sewer Network – Existing Sewer Network with Extensions, 2030

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1 METHODOLOGY

In order to assess the capacity of the existing sewage system for the planning horizon 2030 and to identify the required measures for the improvement of the hydraulic capacity, a detailed hydraulic calculation of the primary and part of the secondary sewer network has been carried out.

1.1 Preparation of the Hydraulic Calculation

1.1.1 Topographic Survey

For the preparation of the hydraulic calculation, a topographic survey of the complete primary and part of the secondary network has been implemented. X and Y coordinates of the manholes, as well as cover and invert levels and diameters of the pipe have been surveyed. In the case that manhole covers could not be opened the invert level has been estimated on the basis of the average slope of the pipe between the preceding and following manhole.

A total length of 16,5 km of the existing sewer network, including 278 manholes, has been surveyed.

1.1.2 Sub-Systems, Main and Sub-Catchment Areas

1.1.2.1 Existing Sewer Network

The area of the city which is currently served by the existing sewer network has been divided in 3 sub-systems corresponding to the area respectively drained by the three main sewers K1, K2 and K3. In each of this sub-systems, main catchment areas (e.g. K1.1, K1.2, etc…) have been defined according the to the up-dated drawing of the existing sewer network, site investigations and information provided by local experts acquainted with the existing sewer network.

For each main catchment area has been determined the area and the existing and forecasted population for the planning horizon 2030, as well as, the population density.

Each of the main catchment area is divided in single sub-catchment area (e.g. K1.1.1. to K1.1.8.) corresponding to a pipe section between two manholes. The name of the sub-catchment area correspond to the number of the upper manhole. The area of each sub-catchment area is calculated according to the ratio of the length of the considered sewer section to the total length of the sewer in the main catchment area. The population of each sub-catchment area is calculated on the basis of its area and the average population density in the main catchment area.

The sewer network and main catchment areas which have been considered in the hydraulic calculation of the sewer network area shown in Drawing no. 002-02-01 and 002-02-02.

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1.1.2.2 Sewer Network Extension

Extension areas of the sewer network have been defined according to the forecasted increase of the population and urban development in Shkodra and in the surrounding villages as well as the proposed concept for the sewerage of the city of Shkodra.

Extension areas of the sewer network, include the currently not connected areas of the city of Shkodra including mainly the industrial and the informal areas east, north and west of the city. These extensions areas have been divided in several sub-systems according to the topography and the connection point to the existing sewer network. These sub-systems are numbered with the prefix “X” followed by the number of the existing main sewer to which it is connected (e.g. Extension are X1 is connected to the main sewer K1).

Furthermore the extension areas include the village of Dobraci and Golemi (respectively numbered with the prefix “D” and “G”) and the area located between Kir River and the Tepe Hills, near to Rozafa Castle (extension area “R” for Rozafa).

For each of these extension areas sub-catchment areas have been defined according to the topography and the route of the main collector (e.g. X1.1.1 to X1.1.5).

The surface as well as the forecasted population for the planning horizon 2030 has been determined for each of these catchment areas.

For the hydraulic calculation of the sewer extension hydraulic calculation system points have been defined. The ground level of each of theses system points has been measured on the available topographic maps. The number of each sub-catchment area correspond to the number of the upper system point.

The sub-catchment areas and system points which have been considered for the hydraulic calculation of the sewer extensions are shown in Drawing no. 002-04-00 until 002-04-04.

1.2 Hydraulic Calculation of the Sewage System

The hydraulic calculation of the sewer network has been carried out according to the German technical Standard DWA-A 118 by use of the Prandtl/Colebrook formula.

Considering the current hydraulically unfavourable condition of the sewer network, a roughness factor of 3,0 mm has been considered for the current situation. For the future (planning horizon 2015 and 2030) it has been considered that the hydraulic condition of the sewer network will be significantly through better maintenance as well as rehabilitation measures and replacement of some sections of the sewer network. Therefore a roughness factor of 1,5 mm has been considered for the future. ,

1.2.1 Design Criteria

The applied design criteria for the hydraulic calculation of the sewer network are given in section 2.3 of the Project Concept Report.


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The hydraulic calculation of the existing sewer network has been carried out for the current situation (2006) and for the planning horizon 2015 and 2030 according to the following criteria.

1.2.1.1 Sewage Production

Domestic Sewage Production

The domestic sewage production is based, according to the measurements and the water consumption forecast upon the following:

Horizon Domestic water consumption

Commercial water consumption

Discharge relevant ratio Sewage rate

2005 250 l/c·d 40 l/c·d 90% 261 l/c·d2015 180 l/c·d 30 l/c·d 90% 189 l/c·d2030 120 l/c·d 20 l/c·d 90% 126 l/c·d

Table 1-1: Domestic Sewage Production Rates

Industrial Sewage Production

For industrial wastewater a specific sewage peak flow of 0,5 l/s·ha, related to the corresponding surface of the connected industrial area has been considered.

Specific large water consumer

On the basis of the water consumption data provided by the water utility, the wastewater discharge of the following significant large drinking water consumers has been considered separately.

Water Sewage Working Average Average PeakConsumer Consumption rate Days per

MonthSewage

FlowSewage

FlowSewage

Flow[m³/month] [%] [d/month] [m³/d]] [l/s] [l/s]

1. Police Directories 900 90 30 27,0 0,31 0,31 2. Electrical Company 1.750 90 22 71,6 0,83 1,24 3. Hospital 13.020 90 30 390,6 4,52 10,85 4. Student Dormitory 1.207 90 30 36,2 0,42 1,26 5. High School 1.406 90 22 57,5 0,67 2,00 6. Senior House 1.140 90 30 34,2 0,40 0,95

Table 1-2: Specific Large Water Consumer


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1.2.1.2 Extraneous Water Flow

Dry Weather Extraneous Water

According to the results of the wastewater measurement campaign, the specific extraneous water rate as given in the following table have been considered for the three main sewer K1, K2 and K3.

For the future situation a progressive decrease of the extraneous water rate, through rehabilitation measures on the sewerage and drinking water supply system, has been considered.

Rain Weather Extraneous Water

In order to take into consideration inevitable false or illegal connection of storm water to a separate sewage water system an additional storm water flow corresponding to 100 % of the average sewage flow has been considered. It should however be mentioned that this additional storm water should be considered as a maximum value after rehabilitation of the sewer network and removal of illegal connection. At the time being the storm water flow connected to the sewer network is much higher.

HorizonMain

SewerDry Weather

Extraneous WaterRain Weather

Extraneous water[l/s·ha] [% of QSW 24]

2006 K1 0,20100 %

K2 0,10100 %

K3 0,50100 %

K0 0,23100 %

2015 all 0,15100 %

2030 all 0,10100 %

Table 1-3: Extraneous Water Flow


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2 RESULTS

2.1 Existing Sewer Network without Sewer Extensions

The results of the hydraulic calculation of the existing sewer network without considering sewer extension are given in the attached Appendices no.1-1 (current situation 2006), no. 1-2 (horizon 2015) and no. 1-3 (horizon 2030).

The results for the situation 2030 are shown in Drawing no. 002-03-00.

2.1.1 Existing Situation 2006

The hydraulic calculation for the current situation show that the existing sewer network has in general sufficient hydraulic capacity with most of the network having large spare capacity (hydraulic loading ratio < 0,5). Critical sections, with some located bottlenecks are the following:

Lower part of K2, downstream of the Square of Five Heroes (sections DN 600 K2.26 to K2.33);

Sewer of the Bujar Bishanaku street upstream of the Square of Five Heroes (section DN 500 K2.24)

Main sewer K3 upstream of the crossroad with Isuf Sokoli Street (section DN 500 K3.11 to K3.14)

Whole length of Main sewer K0 (DN 1000) up to the pumping station.

Excepted for some localised sections with low slope, the above mentioned sewers are however in general not highly overloaded (hydraulic load ratio between 1,0 and 1,5).

2.1.2 Future Situation 2015 and 2030

Despite of the increased population connected to the sewer network, the hydraulic calculation for the future situation 2015, and even more 2030, show improved hydraulic conditions thanks to the forecasted decrease of water consumption as well as extraneous water.

As shown in drawing no. 002-03-00, with the above mentioned design criteria and assumption for the future situation, the existing sewer network has sufficient hydraulic capacity for the planning horizon 2030 without connection of additional catchment areas.

With exception of the above mentioned sewer sections which are working quite close to their full capacity, the remaining part of the sewer network and especially most part of K1 and the upper part of K2 have large spare capacity for future extensions.


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2.1.3 Conclusion

According to the results of the hydraulic calculation of the existing sewer network the main conclusion are as follow:

Without consideration of future sewer extensions, the existing sewer network has sufficient capacity for the planning horizon 2030;

In particular K1 and most of K3 have large spare capacity which allow for the connection of extension areas of the sewer network;

Connection of additional extension areas to K2 shall be avoided in order to allow the DN 600 lower part of this sewer to be maintained in the future;

Main sewer K0, which already works near to its full capacity, will probably need to be replaced with the connection of extension areas to the existing sewer network.

2.2 Existing Sewer Network with Extension Areas for 2030

2.2.1 Sewer Network Extensions

According to the analysis of the existing situation and the above mentioned hydraulic calculation of the existing sewer network, the main lines of the proposed concept for the future extension of the sewer network is as follow:

Connection of the industrial area to the upper part of main sewer K1 in Çerçiz Topulli street;

Connection of the currently not connected areas east and south east of the city on several points of main sewer K1;

No additional areas connected to main sewer K2;

Dobraci and Golemi connected on several points to the upper part of K3 north of the town;

Extension area west of the town connected to a separate sewer system with a pumping station and discharging in the lower part of K3;

Areas near to Kir river south-east of the Tepe hills served by a separate sewer network with a pumping station discharging directly into the main pumping station.

2.2.2 Results

The hydraulic calculation of the existing sewer network for the planning horizon 2030, according to the above-described concept, is given in Appendix 2-1. Results are shown in Drawing no. 002-05-00.

Following section of the network need to be replaced and reinforced for the planning horizon 2030 to allow for the connection of additional catchment areas as described above:


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Main Sewer K1:

Section K1.2 (K1.2.2 to K1.2.6): sewer DN 300 in the upper part of Skenderberg street, on which will be connected the industrial area;

Section K1.6 (K1.6.1 to K1.6.4): sewer DN 400 in Skenderberg street upstream of the crossroad with Marin Barleti street;

Main Sewer K3:

Sections K3.12, K3.13 and K3.14: sewer DN 500 in Mujo Ulqinaku street upstream of the crossroad with Isuf Sokoli street.

Main Sewer K0:

Sections K0.1 (K0.1.3 to K0.1.14): sewer DN 1000 connecting to the m,ain pumping station.


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A P P E N D I C E S


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Appendix 1- : Hydraulic Calculation of the Sewer Network – Existing Situation 2006

Appendix 1- : Hydraulic Calculation of the Sewer Network – Existing Sewer Network, Situation 2015

Appendix 1- : Hydraulic Calculation of the Sewer Network – Existing Sewer Network, Situation 2030

Appendix 2- : Hydraulic Calculation of the Sewer Network – Existing Sewer Network with Extensions, 2030


annex1 hydraulic calculation of the sewer network

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