Matilda Beatty

Principal Hydrogeologist, Severn Trent Water

A Water Company Perspective

Urban Groundwater for PWS

Presentation structure

• An introduction to the STWL area

• Catchment risk assessment and DWSPs

• Existing problems with sources in urban areas

• New risks

• New source development in urban areas

• Summary of key issues for PWS

Severn Trent sources of supply

Annual average supply1700 – 1900Ml/d

1/3 reservoirs 1/3 rivers1/3 groundwater

Coventry

Birmingham

Leicester

Stoke

Kidderminster

•Sherwood Sandstone

•Carboniferous Limestone

•Magnesian Limestone

•Permo-Carb. Sandstone

•Jurassic Limestone

Major Aquifer Types (unconfined extent)

Nottingha

m

Shrewsbur

y

Mansfield

Severn Trent sources of supply

Examples of Urban Source quality

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TL - TCM Concentrations vs. Station Output[01/01/90-31/12/08]

Average (l/s)

NB: TCM Concentrations for Borehole BH2 on

23/06/08 represent Depth Sampling Results and are

not representative of abstracted water quality

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Tack Lane and Norton DSR TCM

RAW 1

OS map. Severn

Trent Water Ltd

copyright

WU298522

Examples of Urban Source quality

OS map. Severn

Trent Water Ltd

copyright

WU298522

Examples of Urban Source quality

Sunnyside

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Jan-04 Jan-06 Jan-08

No.3 Lst

No.4 Sdst

Terachloroethene [ug/l]

West to East ... A60 to Hospital Borehole

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Chainage from A 60 (m)

m A

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Ground Level SUNNYSIDE SITE Sunnyside Operational RWL Sunnyside No.3

Screen and Pack Limestone PWL Range Sunnyside No.4 Sandstone PWL Range

Hospital Borehole Hospital RWL Hospital PWL Casing Shoe

Base SSG [Incl. Brotherton Fm] Base Edlington Fm Base SSG [Incl. Brotherton Fm] Base Edlington Fm

Base Cadeby Edlington Formation Edlington Formation 1989 Test Data No.3 pumping

OS map. Severn

Trent Water Ltd

copyright

WU298522

• Historic usage, no longer in business – who liable?

• Proof of liability

• Cost of treatment vs cost of investigation and legal costs

• As no significant environmental impact – no EA / Government funds, down to civil claim from water company (will this change with Article 7 of WFD?)

Polluter pays principal

• Opportunity to use other techniques rather than treat at point of abstraction?

• Cost of treatment

• Cost of investigation and remediation

• Risk – of not achieving drinking water standards at the point of abstraction

Alternative to treatment at

abstraction point

• Redevelopment of old industrial sites

• Drilling of exploratory gas boreholes

• New development close to boreholes – crypto, SUDS

• Allotments!

• Will protection via planning drop with abolishment of regional planning strategy and EA funding cuts?

New Risks

(No Water Available)

(Over Abstracted)

(Over Licensed)

(Water Available)

WA = Water Available for futher abstraction

NWA = No Water Available for further abstraction

OL = Over Licensed

OA = Over Abstracted

2

New Source Development

EA CAMS

evaluations

Where is

groundwater

available for

new supply....

.....urban areas

Experience of new sources in

Birmingham

• River augmentation boreholes developed between ~2000 and 2009

Birmingham geological setting

• Brown field sites identified, mostly on unconfined Sherwood Sandstone

Pilot borehole testing and final BH design

• Pilot borehole drilling and testing

• Two aquifer horizons of differing water quality identified

Shallow aquifer

• High conductivity (1200uS/cm)

• Acidic pH (6.5)

• High NO3 (100mg/l)

• Elevated major ions (SO4, Mg)

• Elevated metals (Ba, Cu, Pb, Ni, Cr)

• Trichloroethene (42ug/l)

Birmingham BHs quality results

and future risks

Deep aquifer

• Water quality more typical of natural aquifer

• Conductivity (450uS/cm)

• NO3 (30mg/l)

• Trichloroethene (2ug/l)

Uses geological structural, hydraulic and natural attenuation properties to maximise protection of the water quality of the new sources

• Some of river augmentation BHs to be developed for public water supply

• Development of one new urban source

• Further quality risks – implications for treatment costs?

• ASR schemes, but in confined areas.....

Planed New PWS sources

• Historical pollution a problem, some sources only now being significantly impacted

• Customers pay for treatment, or undertake further investigation to pursue civil claim

• Reliable cost effective options of in-situ remediation, cost and risk

• Exploit hydrogeological protection in the design of new urban sources, uncertainty in quality over time

• Changes to planning policy and government funding, potential increased risk to drinking water supply sources

Summary

• (HSI) – Scott Wilson

• Grontmij

• MWH

• Matt Hudson

• Rick Ireland (Aquarite)

• Environment Agency

• Others........

Contributions from

Many thanks