Regional WELLHEAD
PROTECTION Process Status
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by Lloyd Brewer
Environmental Programs
City of Spokane
Why?
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Protection of:
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Drinking water quality
Infrastructure investments
Hydro-geological resources
Local economy
From:
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Increased cost of water
Health Risks (Acute & Chronic)
Contaminant Types &
2007-2008 Incidents (CDC)
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Chemical (1)
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Radiological
Biological
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Degradable
Non-degradable
Bacteria (21)
Viruses (5)
Parasites (3)
4,128 illnesses (4 unknown cause), 3 deaths
Chronic Risk
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Critical Materials 2,241 on City List
Examples:
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Hexavalent Chromium MCL 100 ppb;
CAHG 0.02 ppb
Arsenic MCL 10 ppb; MCLG 0
Lead Action Level 15 ppb; MCLG 0
Trihalomethanes MCL 80 ppb; MCLG 0
Dilution vs. Distance Between Drywell and Water Well
300
244.3
250
209.7
200
Dilution Factor
175.1
140.5
150
105.8
100
71.2
50
36.6
15.8
2.0
0
0
200
400
600
800
1000
1200
1400
1600
Distance Between Drywell and Water Well
Annual Discharges
25 Year Storm Event
10 Year Storm Event
1800
2000
Stormwater Facilities &
Distance from Wells
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Additional protection of groundwater quality can be
achieved by:
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Siting BMP’s outside of capture areas, or
Careful siting and maintenance inside capture areas
Should be sited as far up-gradient of wells as
possible
The greater the separation distance, the more benefit
is achieved
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Increased warning time
Increased attenuation of degradable pollutants
Somewhat increased dilution of non-degradable pollutants
Main Considerations

The main considerations for siteing recharge
facilities are (1) whether the separation
distance can be increased to allow for greater
attenuation of some pollutants during routine
stormwater infiltration events, and (2) whether
the recharge facility will alter the alignment of
downgradient or cross-gradient SWPAs.
Other Considerations
A 10-year (or less frequent) precipitation event will
generate such large quantities of stormwater that
chloride and other pollutants would likely be much
more diluted than those seen during more routine
conditions.
Adverse conditions such as flooding do not result in the
collection of samples that are representative of
typical stormwater quality. The highest
concentrations of pollutants in stormwater typically
occur during the first 30 minutes of the first rainfall
event that occurs after an extended dry period (see
pgs. 24 & 25 of EPA, 1992).
History
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a) 1979 – Spokane Aquifer Water Quality Management Plan
b) 1986 – Safe Drinking Water Act amended to require States to
develop Wellhead Protection Plans
c) 1992-1993 – grant for technical aquifer model development
d) 1998 (OPR 98-144) agreement between the SAJB, Spokane
County, Millwood, and the City of Spokane for WHPPC
e) Sept. 2007 SAJB Wellhead Protection Update
f) Nov. 2007 – Council Resolution 2007-0125 Stated support
for regional wellhead protection
g) 2011 State DOH grant for Wellhead Protection Aquifer
Model update
h) Now - WHPPCC works to complete recommendations
SAJB Wellhead Protection
Update Issues
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Aquifer / Aquifer Water Quality Recognition/Protection
Special Wellhead Protection Area (SWPA) recognition by land
use regulators
Stormwater handling in/or impacting SWPAs
Wastewater handling in SWPAs
Septic systems in/or impacting SWPAs
Reclaimed water use in/or impacting SWPAs
Control of relatively high risk business activities in SWPAs
SAJB Wellhead Protection
Proposed Mechanisms (slide 1 of 2)
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Promote consistent regional aquifer protection
Special Wellhead Protection Area (SWPA)
recognition by land use regulators ( one year time of
travel )
Improve communication between land use regulators
and drinking water purveyors
Increase control of reclaimed water, stormwater,
wastewater, & septage handling in SWPAs
Checks on NEW stormwater & reclaimed water
facility proposals to assess potential to adversely
impact SWPAs/wells
SAJB Wellhead Protection
Proposed Mechanisms (slide 2 of 2)
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Stormwater- reduce contaminant concentrations
reaching the aquifer using source control, increased
dispersion/degradation, and treatment systems
beyond the minimum normally required.
Where pathogenic organisms are potential
contaminants such as in surface water, seek a
distance of 1 year time of travel from source to well.
For relatively high risk business activities who do not
have approval of the water purveyors and land use
regulator whose areas they would develop in – a
requirement to get a conditional use permit via public
process.
Proposed Relatively Risky
Business Activities List (slide 1 of 3 )
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Animal Feedlots
Bio-research Facilities
Chemical/Agricultural chemical warehousing
Composite (“fiberglass”) Products Manufacturing
Dry Cleaning (performed on location)
Electronics Manufacturing
Electroplating/Metal Finishing
Engine & Vehicle Repair/Service/Salvage
Furniture Stripping
Junk Yards
Proposed Relatively Risky
Business Activities List (slide 2 of 3 )
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Metal Fabrication
Mining/Sand & Gravel Extraction
Storage of Critical Materials
Transfer of Critical Materials
Oil & Gas Drilling
Paint Manufacturing and Wholesale Storage
Petroleum Bulk Storage & Transmission
Photo Processing
Printing and Lithography
Solid Waste Handling & Recycling Facilities
Proposed Relatively Risky
Business Activities List (slide 3 of 3 )
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Vehicle Washing
Wastewater Bulk Storage, Treatment & Pumping
Facilities
Wood Treatment Facilities
NEXT STEPS
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Complete WPPCC Recommendations
Pass recommendations & process details to the
SAJB, other purveyors, and WA-DOH
Pass recommendations to local government
planners, plan commissions, and elected officials
Support local government processes to put
recommendations into place
There will be opportunities for further
public input at the local government
venues
Questions?
Follow the process at:
www.greenspokane.org/water/
or
www.sajb.org
Draft Recommendations
Within SWPAs
slide 1 of 3
5) The Wellhead Protection PCC recommends that each
jurisdiction adopt the following in their Critical Area Ordinances
Disposal of Stormwater within Special Wellhead Protection Areas
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a) Will be in compliance with the Spokane Regional Stormwater
Manual and/or the Stormwater Management Manual for Eastern
Washington and no new direct injection of untreated stormwater1
in special wellhead protection zones is allowed.
1 untreated stormwater here means stormwater that has not
passed through a stormwater best management practices
facility before discharge to a drywell regardless of the level of
treatment provided.
Draft Recommendations
Within SWPAs
slide 2 of 3
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b) The size of the post-development basin flowing into a special
wellhead protection zone shall not be greater than the size of
the predevelopment basin flowing into it unless an engineering
analysis demonstrates that the proposed basin increase does
not have an adverse impact to the wellhead protection zone.
c) In special wellhead protection areas stormwater injection and
injection wells should be located as far as practical from
wellheads.
d) Except for uncontaminated roof runoff, no stormwater
discharge treated or otherwise should occur within100 feet of a
drinking water well.
Draft Recommendations
Outside of SWPAs
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d) Stormwater disposal facilities over the Aquifer but
not in special wellhead protection zones which are:
a. designed to handle greater volumes than would
be modeled coming from a wellhead protection area,
or, b. immediately up-gradient of a wellhead
protection zone and within 2 year time of travel, or c.
near the aquifer boundary, or d. facilities that would
be handling runoff which at least in part came from
perennial surface water bodies,
should be required to be modeled using the same
aquifer model used for the delineations
Acceptable When
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1) no more than 20% of any well’s modeled
production comes from this source of
recharge, and
2) where stormwater runoff could include
perennial surface water, the annual recharge
is at least a one year time of travel from all
drinking water wells.
Draft Recommendations
Within SWPAs
slide 3 of 3
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e) Stormwater facilities within 300 feet of a drinking water well
need to provide treatment at least equivalent to a 208 swale with
engineered soil.
f) Stormwater facilities within special wellhead protection areas
should be designed such that: 1) the impervious surface area
they each handle is less than the standard area of such
facilities; and/or 2) treatment systems beyond the minimum are
added; and/or 3) such stormwater facilities should be
maintained and rehabilitated at a frequency exceeding the norm.
g) At the well, maximum well pumping should result in no
greater than a 20% stormwater contribution given annual
average stormwater injection.
Horizontal Distance Between Well & UIC Facility
1 Year Time of Travel Goal
Depth to Water Table from Land Surface at UIC Facility (feet)
0
20
40
120
200
280
360
440
540
1000
Aquifer
0
0
0
0
0
0
0
0
0
0
0
Velocity
1
365
350
335
304
274
243
213
183
152
-30
ft/day
6
2190
2100
2008
1825
1643
1460
1278
1095
913
-183
10
3650
3500
3346
3042
2738
2433
2129
1825
1521
-304
15
5475
5250
5019
4563
4106
3650
3194
2738
2281
-456
17
6205
5950
5688
5171
4654
4137
3620
3103
2585
-517
20
7300
7000
6692
6083
5475
4867
4258
3650
3042
-608
25
9125
8750
8365
7604
6844
6083
5323
4563
3802
-760
30
10950
10500
10038
9125
8213
7300
6388
5475
4563
-912
35
12775
12250
11710
10646
9581
8517
7452
6388
5323
-1065
40
14600
14000
13383
12167
10950
9733
8517
7300
6083
-1217
45
16425
15750
15056
13688
12319
10950
9581
8213
6844
-1369
50
18250
17500
16729
15208
13688
12167
10646
9125
7604
-1521
55
20075
19250
18402
16729
15056
13383
11710
10038
8365
-1673
60
21900
21000
20075
18250
16425
14600
12775
10950
9125
-1825
In most cases it will not be possible to achieve a one year time of travel.
Storm Events &
Distance from Wells
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However, pollutant transport models and in-aquifer
dilution calculations illustrate that a small versus
large separation distance will have little, if any, effect
on pollutant attenuation during low-recurrence highrainfall events (such as the 24-hour event that has a
10-year or greater recurrence interval), particularly for
a non-degradable pollutant such as chloride that may
be present in municipal stormwater generated during
such an event (for example, a rain on-snow event
that generates stormwater from roadways that have
been salted during the winter, prior to the event).1
In Special Wellhead Protection Area
with discharge to ground
Total SPWA Dispersed
Impervious Similar UIC
SWPA
Area
Length
Facilities
sq.feet
#
years
100,000
1
1
100000
100,000
10
1
10000
100,000
10
0.5
20000
1
1
1
1
Assuming:
a)
The impervious area is the source of contaminants and they are evenly spread.
b)
More treatment time and more surface area equals reduced contaminant load reaching aquifer.
Then:
The smaller the value in column J the less contaminant load reaches the well.
This would be true for contaminants that are treatable and/or bio-degrade.
It would also be true for other contaminants in terms of concentrations reaching the well at once.
year inches precip*
1
1.01
1.0147
2
1.4
1.4
0.897404
10
2
2
1.014246
25
2.4
50
100
# of drywells
Storm Frequency
equal impervious area
Equivalent
1
1 year
2
10
3
100
2.6
4
1000
2.6
2.8
5
10000
3
3
10
1000000000
100
1E+99
1.014683
1000
#NUM!
* Precipitation values come from the Regional Stormwater Manual Isopluvial maps.
The largest value over the Aquifer area was assigned per design storm year.
http://www.spokanewastewater.org/Docs/Stormwater/Spokane_Regional_Stormwater_Manual.pdf
pages 131-135
The above calculations show that the volume of water going into a drywell during a one year storm event
is only tripled in a one hundred year storm event.
This also indicates that the stormwater from larger events is relatively easy to handle with addition of drywells.
Balance Needed
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Cost of protection vs impact of loss
Stormwater & Wastewater costs are
already increasing
Existing regulation vs new regulation
Generally one of two solutions
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Clean up contaminated water
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OR
Abandon the well