Regional WELLHEAD PROTECTION Process Status

by Lloyd Brewer Environmental Programs City of Spokane

Why? Protection of:

Drinking water quality Infrastructure investments Hydro-geological resources Local economy

From: Increased cost of water Health Risks (Acute & Chronic)

Contaminant Types & 2007-2008 Incidents (CDC) Chemical (1)

Degradable Non-degradable

Radiological Biological

Bacteria (21) Viruses (5) Parasites (3)

4,128 illnesses (4 unknown cause), 3 deaths

Chronic Risk Critical Materials 2,241 on City List Examples:

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

0 200 400 600 800 1000 1200 1400 1600 1800 20000

50

100

150

200

250

300

2.0

15.8

36.6

71.2

105.8

140.5

175.1

209.7

244.3

Dilution vs. Distance Between Drywell and Water Well

Annual Discharges 25 Year Storm Event 10 Year Storm Event

Distance Between Drywell and Water Well

Diluti

on F

acto

r

Stormwater Facilities & Distance from Wells Additional protection of groundwater quality

can be achieved by: 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

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 ConsiderationsA 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 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 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)

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)

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 )

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 )

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 )

Vehicle Washing Wastewater Bulk Storage, Treatment &

Pumping Facilities Wood Treatment Facilities

NEXT STEPS 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/orwww.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

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 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 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 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 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

1Year 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 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 high-rainfall 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 Facilities Length

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. 

# of drywells Storm Frequency

year inches precip* equal impervious area Equivalent

1 1.01 1.0147 1 1year

2 1.4 1.4 0.897404 2 10

10 2 2 1.014246 1.014683 3 100

25 2.4 2.6 4 1000

50 2.6 2.8 5 10000

100 3 3 10 1000000000

100 1E+99

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 Cost of protection vs impact of loss Stormwater & Wastewater costs

are already increasing Existing regulation vs new

regulation

Generally one of two solutions Clean up contaminated water

OR Abandon the well