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
0.000
5.000
10.000
15.000
0
15
30
45
60
75
90
105
120
01-J
an-9
0
01-J
an-9
1
01-J
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2
-Dec-9
2
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an-9
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an-9
5
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an-9
6
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an-9
7
01-J
an-9
8
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an-9
9
02-J
an-0
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1
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an-0
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an-0
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Co
nc
en
tratio
n (U
g/l)S
tati
on
Ou
tpu
t [l
/s]
Date
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
0
5
10
19
/07
/99
15
/01
/00
13
/07
/00
09
/01
/01
08
/07
/01
04
/01
/02
03
/07
/02
30
/12
/02
28
/06
/03
25
/12
/03
22
/06
/04
19
/12
/04
17
/06
/05
14
/12
/05
12
/06
/06
09
/12
/06
07
/06
/07
04
/12
/07
01
/06
/08T
CM
(ug/l)
Date
Tack Lane and Norton DSR TCM
RAW 1
OS map. Severn
Trent Water Ltd
copyright
WU298522
Examples of Urban Source quality
Sunnyside
0
1
2
3
4
5
6
7
8
9
Jan-04 Jan-06 Jan-08
No.3 Lst
No.4 Sdst
Terachloroethene [ug/l]
West to East ... A60 to Hospital Borehole
-100
-80
-60
-40
-20
0
20
40
60
80
100
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700
Chainage from A 60 (m)
m A
OD
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
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