welcome to p - project dewatering · project dewatering limited p ... percussive or rotary drilling...

WELCOME TO PROJECT DEWATERING LIMITED

Project Dewatering Limited is a leading specialist dewatering subcontractor operating in the UK, Ireland and across Europe, offering clients professional,

cost-effective solutions to groundwater engineering.

We have highly skilled and reliable design, estimating and operation teams, with the technical ability needed to undertake wide scale design, installation and maintenance of dewatering projects.

We are committed to:

• Providinginnovative,tailormade,reliablesolutions

• Investingintheexpertiseofourstaff

• Underpinningallofourworkwithhighquality,consistent,transparentprocesses

Our particular expertise in monitoring and control systems allows us to provide fully instrumented pumping tests, automated treatment and remediation plants, and borehole pumping systems for both water supply and ground-source energy purposes. For a truly comprehensive service we combine this with hydrogeological, geotechnical, mechanical and electrical engineering disciplines.

For projects outside of the UK and Ireland we draw upon our in-house capability, supported by the extensive resources of our parent company, Hӧlscher Wasserbau GmbH, which is an international market leading dewatering company. We benefit from sharing best practices from across the Hӧlscher Wasserbau group, which provides a wealth of experience in all types of ground conditions and construction environments.

CALL US TODAY for Free initial advice 01473 658 807

DESIGN We design cost-effective dewatering systems specific to your site and ground conditions. We have expertise in the following areas:

• AssessmentofSiteInvestigationreports

• Analysisofpumpingtestdatatoestimatesoilpermeability,aquiferstorageandboundaryconditions

• Designbyvariousmethods,including2-dimensionaland3-dimensionalgroundwatermodelstodetermineflowrates,flowpathtraveltimes,contaminantmigrationrisksandrechargerates

• Designofwellstoensuremaximumyieldwhileeliminatingpumpingoffines

• Validationofdewateringdesign,usingearlypumpingmonitoringdata

• Calculationoftheoreticalsettlementsthatmayresultfromdewatering

• ProductionofdetaileddesigndrawingsinAutoCAD

EARLYCONTRACTORINVOLVEMENT(ECI)

We understand that getting involved at the earliest stage of any construction project is beneficial to all parties and if dewatering is factored into any project at the initial stages, substantial amounts of time and money can be saved through careful planning and co-ordination. Early Contractor Involvement (ECI) enables us to get a better understanding of your requirements, and to develop reliable and workable solutions based on solid technological knowledge and know-how.

Early factoring of dewatering will:

• Providetimetodetermineimportantinformationanddevelopinnovativesolutions

• Allowforplanningandpreparation,ensuringcriticalconstructioneventsarefactoredinandcontrolled

• Ensuretherightteamandexpertiseforthejob athand

• Allowtimeforpumpingtestsortrialstobecarriedout,therebyreducingriskatlaterstages

• Ensurepropermeasuresareputinplacetomonitorandmanagestakeholderexpectations

GROUNDWATER MODELLING

PUMPING TEST ANALYSISPUMPED WELL: PW1TEST:72HRCONSTANTRATETESTFLOWRATE:12.4L/S

An example output of a 3D groundwater model is shown for a dewatering system required for the construction of three shafts, with contours displaying groundwater levels. The model is used to predict required pumping rates, along with both internal and remote external drawdown, calibrated with pumping test data and then validated with monitoring data from the system operation.

An example of pumping test data analysis for a project involving deep chalk well dewatering, with potential for under-drainage of the overlying Thanet Sands in the London Basin.

Chalk

Thanet Sand

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.01 10 100 1000

Dra

wdo

wn

(m)

Distance from pumped well (m)

PORTFOLIO & SECTORS


Project Dewatering has a long-standing reputation for delivering expert groundwater management to the construction industry. Our team of expert engineers, designers and project managers have over 150 years of combined experience working on high profile projects, spanning a wide range of sectors, including:

1 RAFLakenheath,Suffolk(Wellpoints)

2 RAFKinloss,Scotland(Wellpoints)

9 ForthRoadReplacementCrossing(Deepwells,WellDrilling,PumpingTests,Monitoring)

10 MilfordHaven (Deepwells,WellDrilling)

11 BelgraveRoadPumpingStation,Bridlington(Deepwells,WellDrilling,PumpingTest)

18 TyneTunnel2,Newcastle (Ejectors,WellDrilling)

19 LondonPowerTunnels,HackneyShaft (Ejectors,Deepwells,WellDrilling,PumpingTests,Monitoring)

20 BelfastSewers,Ireland (PassiveReliefWells,WellDrilling,Deepwells,Monitoring)

3 OneTheSquare,Cambridge(Deepwells,WellDrilling)

4 TheBroadwayShoppingCentre,Bradford (Deepwells,WellDrilling)

5 VictoriaSquareShoppingCentre,Belfast (Deepwells,WellDrilling)

12 GreatBlakenham(EfW) (Deepwells,PumpingTests, WellDrilling,Monitoring)

13 Peterborough(EfW) (Ejectors,WellDrilling,Monitoring)

14 Cardiff(EfW) (Deepwells,PumpingTests, WellDrilling,Monitoring)

21 AshcroftCoastHolidayPark,Kent(WellDrilling,PumpingTests,Ejectors,Monitoring)

22 BelleVueRoad,Weymouth(WellDrilling,Deepwells,Monitoring)

6 MarketDeepingHousingDevelopment,Lincolnshire (Wellpoints)

7 NorthstoweHousingDevelopment,Cambridgeshire(Wellpoints)

8 KentCountyCricketClub,Kent(Wellpoints)

15 CopenhagenCityringenMetro(Deepwells,WellDrilling,Remediation,Monitoring)

16 Stuttgart21(WellDrilling,Remediation,Monitoring)

17 ChannelTunnelRailLink,Stratford(WellDrilling,Deepwells,PumpingTests,Monitoring)

23 StokeBardolphWWTW,Nottingham(Wellpoints)

24 StanleyWWTW,Wakefield(WellDrilling,Deepwells)

25 LeominsterWWTW,Slough(WellDrilling,Deepwells, PumpingTests)

26 AbertonReservoirColchester (Wellpoints)

27 FrankleyWTW,Birmingham(Deepwells,WellDrilling,Monitoring)

28 ImperialWest,London (PumpingTests,GroundSourceEnergy,Monitoring)

AIRPORTS

PORTS & MARINE

SHAFTS&TUNNELS

BASEMENTS

POWER STATIONS SLOPE STABILISATION

GROUNDWORKS

RAILWAYS

WATER WORKS

WATER SUPPLY

15

16

1

2

3

4

5

17

6

7

8

9

10

11

12

13

14

18

19

20

21

22

23

24

25

26

27

28

D eepwells are used for dewatering of excavations when drawdown is required below 6m depth and

permeability of the targeted soil is moderate to high. In addition, deepwells may be used to underdrain less permeable overlying strata in certain ground conditions.

An array of deepwells is installed either internally or externally, and may work to control groundwater in conjunction with a physical cut-off wall, such as a sheet-pile, secant-pile, or diaphragm wall. Each deepwell typically consists of a borehole, lined with a slotted screen and annular filter pack through the target stratum. An electric submersible pump is installed within the liner close to the base of the well and connected to the surface via a riser pipe. Water is then pumped into a common header main before being discharged or recharged back to the ground.

As water is pumped from a deepwell, a hydraulic gradient is formed and water flows into the well, forming a cone of depression around it, in which there is little or no water remaining in the pore spaces of the surrounding soil.

Deepwells are typically drilled using cable percussive or rotary drilling methods, usually terminating in a 300mm or 250mm bore. In competent ground, such as chalk or sandstone, wells may be installed with an open-hole section as per a traditional water supply well.

ADAPTABLE

Where soil permeability is low, it is common to seal the well and apply a vacuum to improve the well yield and the overall drawdown of a system. Experience shows that applying a vacuum to a low yielding well, such as the one installed in the Lambeth Group in London, can improve the rate of extraction by 50%. For depths in excess of 45-50m, vacuum deepwells are usually more efficient than ejectors wells.

Where there is a need to minimise external of remote drawdowns, maybe due to settlement concerns or risk of contaminant migration, water can be recharged back to ground using recharge or reinjection wells. These wells are very similar in design to a deepwell, but often recharge the water to different strata.

DEEPWELLS


Where groundwater must be lowered more than six metres below ground in lower

permeability soils, such as silt or fine sand, ejectors often offer the best dewatering solution. At depths greater than 45-50m, ejector systems can become inefficient, often making a vacuum deepwell system more appropriate.

Ejectors occupy a niche in the dewatering industry, where pumping levels are too deep for wellpoints, but well yields are too low to allow the use of electric submersible pumps alone (as with classic deepwells).

Ejector wells are drilled and installed, just like deepwells, but they differ from them in the way that the water is extracted. Unlike electric submersible pumps – which can quickly burn out if run in a dry borehole – ejectors can pump air and water mixtures without issue, and if the top of the borehole is sealed, then a vacuum produced by the pumping action will improve

gravity drainage towards the well as a result of the creation of a vacuum-assisted drainage path.

Ejector systems require both a high-pressure supply and low-pressure return header main following the line of wells. Project Dewatering Limited offers the choice of either a double pipe or concentric pipe ejector system to suit the site conditions.

EXPERIENCE

Ejectors require a greater level of experience to successfully operate than traditional wellpoint and deepwell systems, and can often require more regular maintenance, due to the loss of performance and efficiency caused by naturally occurring iron-related bio-fouling. Project Dewatering Limited has a wealth of experience in the installation, monitoring, control and maintenance of these systems, ensuring drawdown requirements are met and sustained throughout the course of dewatering.

EJECTORS


Project Dewatering Limited can provide specialist services to clients involved in designing and installing ground source

energy systems by applying skills from other areas of our business. Typically, we are involved in open-loop schemes, but can also provide a thermal response testing service for closed-loop wells.

WE ALSO CARRY OUT:

• Borehole drilling

• Well development by airlift and acidisation

• Pump tests to allow application of an Environment Agency abstraction licence

• Installation and commissioning of permanent borehole equipment (pumps, pipework and controls)

• Maintenance of wells and borehole equipment

• Well rehabilitation

GROUND SOURCE ENERGY


Monitoring is at the heart of everything we do, whether it be for the control of a dewatering system,

the instrumentation of high quality pumping tests or for compliance with Environment Agency abstraction licence and discharge consent conditions.

Our monitoring and control systems typically consist of:

• A central data logger or PLC unit with remote GPRS/GSM modem connection

• Water level monitoring by transducers (wired or wireless)

• Flow meters, including electromagnetic, mechanical (with pulse output) and ultrasonic types

• In-line water quality sensors, such as pH, electrical conductivity and turbidity

• Pump function alarms and a remote or automated facility to switch-on/off

• Solenoid valve controls for automated process control

For complex projects, our clients can view and track data on a web-based portal, but if they want a more simplistic approach, we will instead provide regular monitoring reports. All data is continually reviewed in-house and compared to manual measurements made onsite to provide quality assurance and ensure we are aware of all of the project’s developments.

Alarm functionality can be provided to warn the site management in the event of a power failure, pump trip, or trigger level exceedance. As ever, the level of monitoring is always appropriate to the site in question to ensure cost effectiveness.

Project Dewatering Limited works with a number of trusted and established suppliers to develop monitoring systems specific to our clients’ needs. In addition, our parent company, Hӧlscher Wasserbau GmbH, designs and creates its own PLC systems, which are routinely used on the largest dewatering and treatment systems operated across Europe such as the Copenhagen Cityringen Metro and Stuttgart 21 projects.

MONITORING


Project Dewatering Limited carries out pumping tests (or aquifer tests) to evaluate an aquifer by stimulating it

through constant pumping, and observing the response (drawdown) in an array of observation wells. From the results, it is possible to determine the hydrogeological characteristics of the ground, which can be used for further design work.

The resulting data can be used to:

• Determine the hydraulic properties of an aquifer or aquifers for both dewatering design and water supply investigations

• Determine potential for under drainage, hydraulic connectivity between layers, and possibly indicate anisotropic permeability that may impact cut-off wall depth design

• Determine spatial effects of pumping, including distance of influence

• Assess the hydraulic behaviour of a well to assist future well design optimisation

• Provide information on water quality and its variability with time

We offer a comprehensive, high-quality pumping test service, carried out to Standard BS EN ISO 22282-4:2012. Our tests are instrumented with water level transducers and electromagnetic flow meters to provide automated monitoring, with manual measurements provided for confirmation of data. We provide a detailed factual report as standard, and can also offer interpretative reports (with groundwater modelling) as part of our in-house design service.

For dewatering projects, the cost of carrying out an initial survey is typically far less than that of dealing with unforeseen hydrogeological conditions encountered once site work begins.

PUMPING TESTS


Treatment of groundwater is carried out in order to improve water quality when dealing with an aquifer where there

is legacy contamination. This is carried out either as aquifer and ground remediation, or in conjunction with dewatering operations, to ensure water is suitably clean for discharge.

Groundwater can become polluted or contaminated as a result of aquifer exploitation and historical industrial land-uses. Where dewatering systems are used, there can be a risk of mobilising contaminants from remote areas, which should be taken into consideration as part of a dewatering or hydrogeological risk assessment. Contaminants found in groundwater include the entire spectrum of physical, organic and inorganic chemical, bacteriological, and radioactive parameters.

We can help you analyse the quality of your groundwater by taking samples from boreholes

and pumping systems and, once determined, provide you with the solution most appropriate to your needs. We commonly deploy granular activated carbon vessels, oil/water separator tanks, or air strippers to the site. Other treatment technologies are available depending on contamination type.

COST-EFFECTIVE

Project Dewatering Limited has many years of experience in groundwater remediation, and offers a wide range of cost-effective solutions. Our treatment plants can be installed with continued monitoring capabilities and automated control for your project. We have access to an extensive range of state-of-the-art equipment, often used in some of the most demanding European water treatment schemes and construction projects.

REMEDIATION & TREATMENT


Project Dewatering Limited typically drills wells for dewatering systems, pumping tests, water supply, ground

source energy and groundwater remediation. Through our long-standing relationships with our partner companies, we have access to a wide variety of drilling equipment and techniques to suit all ground conditions. We commonly use cable percussion drilling, rotary cased and open-hole methods, and, where appropriate, auger drilling. Plants and machinery are well-maintained and comply with the latest Health and Safety requirements.

We will assess the specific ground conditions that we expect to encounter and determine suitable drilling methodology to ensure both quick progress and a high-quality finished installation. We insist on using drilling techniques that optimise well efficiency and yield, and closely monitor drilling processes to ensure that installation of well screens and grouted-casings is carried out to the highest standard.

Drilling projects range from shallow wellpoints to large diameter deep water supply wells.

OPTIMISATION

Following drilling, well development is carried out to maximise yield and eliminate fines in the discharge, ensuring pumping of clear groundwater. This usually involves development by airlift techniques, but for chalk wells could include treatment by acidisation.

WELL DRILLING


Wellpoints are small-diameter, closely-spaced shallow wells, which offer a highly economic and

versatile method of groundwater control, where drawdown requirements are less than 5-6 m depth. Wellpoints are pumped using specialist surface vacuum pumps, and are particularly effective in stratified and fine-graded soils, and also have the advantage of being installed comparatively quickly, making them ideal for dynamic sites, such as pipeline installation, where many metres of pipe can be laid in a single shift.

Each wellpoint consists of a small diameter riser (typically 38 to 50 mm), with a slotted filter at the base. Typically, they are installed around the perimeter of an excavation, or parallel to a pipeline trench, by either jetting, augering or traditional drilling techniques.

As vacuum and flow is generated by a surface pump, limiting drawdown to 5-6m depth, a second stage of wellpoints can be installed at a lower level for greater depths. Commonly, wellpoints are regarded as ‘disposable’, but steel self-jetted wellpoints can often be retrieved after pumps are turned-off.

We offer a wide variety of wellpoint installation methods, providing our clients with significant advantages:

• Wellpoints can be installed quickly in most ground conditions

• They are easy to maintain

• They can be used for both large and small-scale projects

• Steel self-jetting wellpoints can also be deployed, which are both re-usable and advantageous in environments with limited headroom

• Wellpoints can be installed within tunnels and cross-passages to depressurise confined layers encountered during construction

Where difficult ground conditions exist, such as open gravel or overlying firm clays, wellpoints can be installed using a small rotary drilling rig, with either temporary casing, or traditional and hollow-stem augers. By adopting the most appropriate installation methodology for the ground conditions at hand, we can ensure optimal installation times for our clients.

WELLPOINTS


MEET THE TEAM

MARC BEVANManaging Director

Marc is an expert in the field of dewatering and is responsible for the development of the company’s technical and operational capabilities, as well as the design of dewatering systems. Marc is also responsible for the overall management of the company’s UK development, while working closely with parent company, Hölscher Wasserbau.

MICHAEL CRONEYContracts Manager

Michael is responsible for overseeing day-to-day company operations, allocating resources and administering contracts. With a great combination of hands-on experience and a sound understanding of dewatering processes, he enjoys finding practical solutions to any groundwater control issue.

BJÖRN WEBERWater Treatment Manager

Björn is responsible for the acquisition, design and delivery of groundwater treatment and management plants (WTP and General Manager of the‘Environmental Department’ within Hölscher Wasserbau. He has recently provided WTP design and management for the multi-billion euro Stuttgart 21 Railway project and the Copenhagen Metro Cityringen.

ALEX DEL VECCIO MBA

Business Development Manager

Alex is responsible for identifying opportunities, raising company profile and building long-term working relationships with clients. Alex has over 10 years’ experience working within the Hazardous Waste and Bio Remediation industries, where he was responsible for offering both in and ex situ solutions to contaminated land issues for clients.

TIM ROEDERInternational Division Director

Tim is an expert in all fields of Civil Engineering, with specialist knowledge of dewatering. Appointed Director of the International Division of Hölscher Wasserbau in 2008, he oversees the operational aspects of Hölscher Wasserbau’s international growth and ensures that the additional expertise available to Project Dewatering is widely accessible to its UK client base.

MANFRED SCHNIEDERSMonitoring Manager

Manfred is responsible for the technical design of groundwater management control processes for both small and large-scale systems. He has applied his design skills to many extensive infrastructure projects across Europe, where dewatering systems deployment of state-of-art water monitored treatment plants. And 24/7 monitoring and control systems are required.

WHATOURCLIENTSHAVETOSAY...

“Project Dewatering complete their work quickly and efficiently, to the very highest standard, with reliable and effective equipment. We are thoroughly satisfied with their service.”

Jackson Civils.

Unit 3, The Old Wireless Station, Great Bricett, Ipswich, Suffolk, IP7 7DSREGISTERED COMPANY NO. 03809255

01473 658 807 • [email protected]

www.project-dewatering.co.uk

welcome to p - project dewatering · project dewatering limited p ... percussive or rotary drilling...

Documents