section 6 ground water ground water - gwpcstormwater is an integral part of the hydrologic cycle and...

tormwater ManagementStortorm&&

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Contaminated stormwater is a major source of ground water and

surface water degradation. Furthermore, land-development practices

often create impervious surfaces that increase stormwater runoff and

inhibit ground water recharge. A combination of approaches is

needed to improve runoff quality and maximize quality recharge to

ground water. These approaches include preventing the

contamination of stormwater, minimizing impervious surfaces,

segregating clean and contaminated stormwater, and applying best

management practices (BMPs) that promote natural aquifer recharge

and treat stormwater sufficiently before it is discharged to ground

water.

Key Message

Section 6

Top: Construction of buildings, streets, and parking lots prevents rainfall from recharging soiland ground water. It also increases the rate of runoff and contributes to water pollution. Thisis an aerial view of San Francisco, California.

Left: An unknown number of stormwater drainage wells (UIC Class V) such as this can befound throughout the country, discharging stormwater directly into ground water.

Photo Credits. Top: Copyright © Bruce Molnia, Terra Left: Oregon DEQ

Ground Water Report to the Nation…A Call to Action

6 • 2

Keeping on the Sunny Side ofStormwater Runoff

“Local governments nationwide are beginning to utilize Low Impact Development

(LID) along with other storm water management approaches to deal with water quality

problems associated with urban development and redevelopment. Many have revised

their ordinances and building codes and incorporated these concepts into holistic

growth-development plans. However, it is critical that they acknowledge and address

the potential for transferring a problem from surface water to ground water. The key to

protecting both surface and ground water is to make sure that we select best

management practices that proactively address the generation and treatment of

potential storm water contaminants before they enter the hydrologic cycle.”Mary Ambrose, P.G. | Water Policy Specialist | Texas Commission on Environmental Quality

Development alters natural systems as vegetation andopen spaces are replaced with new areas of impervioussurfaces, such as roads, parking lots, roofs, and turf,which greatly reduce infiltration and thus groundwater recharge. A much larger percentage of precipita-tion becomes surface runoff, which moves across landareas at accelerated speeds, creating additional

A redevelopment project in Seattle, Washington, includes a natu-ral drainage system and a site-design strategy to treat and pro-mote onsite stormwater infiltration. Such proactive approachessave communities and property owners money while reducing

overall environmental impact.

whyStormwater matters to ground water…

While stormwater runoff is the natural result of a precipitation event, stormwater in urbanized

watersheds greatly influences ground and surface water quality and quantity—not to mention

the health of aquatic ecosystems. Whether it is

rainwater or snowmelt, water has to go some-

where. In natural, undeveloped areas, a large

percentage of relatively uncontaminated precipi-

tation infiltrates the ground, thus recharging

ground water; the remaining runoff flows to

nearby water bodies or evaporates.

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problems of soil erosion,flooding, and naturalhabitat destruction. Un-controlled runoff also col-lects pollutants such assediments, pathogens, fer-tilizers/ nutrients, hydro-carbons, and metals,which ultimately contam-inate and degrade surfaceand ground water.

Historically, stormwaterhasn’t received the samelevel of attention as otherpollution sources, but it isnow clear that this neglectcan have serious conse-quences. So, taking theircue from nature, commu-nities, planners, engi-neers, architects, and busi-nesses have begun to iden-tify practical ways to restore natural hydrology andprevent the contamination of our water resources.

Many innovative, effective, and earth-friendlystormwater management approaches are in practicealready—and more are hitting the streets each day.Federal and state policies, guidance materials, andoutreach efforts are turning this corner. USEPA andsome states have embraced Low Impact Development(LID), which emphasizes reducing impervious areas,disconnecting impervious areas from one another,and treating stormwater so that it can infiltrate theground near the source. The real challenge will be tomake these approaches standard practice at the locallevel and to ensure that they are designed and main-tained properly so that ground water is not degraded.

STORMWATER IN THE NATURAL ENVIRONMENT

In the natural environmental, the fate of stormwateris influenced by the timing of precipitation and/ormelting, and by topography, geology, and land cover.Under natural hydrologic conditions, a large percent-age of rainwater infiltrates soil or bedrock and replen-ishes ground water. Natural physical, chemical, and

biological processes cleanse the water as it movesthrough vegetation and soil. Water that does not infil-trate the soil is taken up by plants (evapotranspira-tion), runs off into surface waters, or evaporates.Ground water, in turn, discharges to surface waters,such as rivers, streams, lakes, and wetlands.Stormwater is an integral part of the hydrologic cycleand the interplay between surface water and groundwater. During periods of dry weather, ground watersustains stream baseflow and helps maintain freshwa-ter wetlands and aquatic habitats.

STORMWATER IN THE URBAN ENVIRONMENT

In urbanized environments, the natural water cycle isdrastically altered owing to a reduction in permeable

6 • 3

Section 6 • Ground Water and Stormwater Management

A stormy day in Salt LakeCity, Utah.

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areas, such as fields and woodlands, and an increasein impervious surfaces, such as roads, rooftops, side-walks, parking lots, concrete structures of all sorts,and compacted soils stripped of vegetation. Theamount of stormwater runoff and concentrations ofcontaminants in stormwater runoff tend to increasewith population density.

With increased impervious surfaces, less rain soaksinto the ground, and less vegetation is available tosoak up, store, and evaporate water. Impervious sur-faces reduce ground water recharge, which leads toreduced stream baseflows. Impervious surfaces causean increase in runoff volume and speed, whichincreases the frequency of high stream flow and asso-ciated flooding and erosion. Impervious surfaces alsoretain heat, which increases runoff temperatures and,in turn, surface water temperatures.

In the developed environment, stormwater also playsan active role in transporting contaminants. Asstormwater flows over the land surface, it picks upmaterials such as debris, chemicals, oil and grease,

dirt, road salt, sediment, fertilizers, bacteria, and ani-mal wastes—which then enter water courses or infil-trate to ground water. The longer pollutants remainin the environment, shifting through different phasesof the hydrologic cycle and building up in ponds andwetlands and, in some cases, basins designed to con-trol stormwater, the greater the possibility that theywill infiltrate and accumulate in ground water overtime. Besides increasing pollutant loads in surfaceand ground water, contaminated stormwater can haveadverse effects on people, plants, animals, fish, andthe aquatic ecosystem as a whole.

STRATEGIES FOR REDUCINGSTORMWATER IMPACTS

Traditional stormwater management techniques usedevices such as gutters, drains, and pipes to collectrunoff from impervious surfaces and convey it to var-ious discharge points, often by way of detentionbasins or other treatment structures. As a result, large

6 • 4

UIC Class V Well

UIC Class V Stormwater Wells

UIC Class V Stormwater Well

Drinking water well

Bioretention facility

Drinking water wellStormwater

Drainage StormwaterDrainage

Natural Process

Human Impact

Ground Water Flow

FIgure 1. This diagram shows the many of the potential impacts on ground water from various land use types (e.g., agriculture,suburban, urban, industrial, commercial, protected areas) and the variety of paths contaminated stormwater can take to groundwater (e.g., UIC Class V stormwater injection or drainage wells, bioretention facilities, land-surface runoff into rivers and streams,and land-surface infiltration into shallow aquifers). The interconnection between surface water and ground water is also shownas stormwater contaminants move between the two regimes. Showing the location of drinking water sources further demon-strates how stormwater contaminants can influence the water we drink.

POTENTIAL STORMWATER IMPACTS TO GROUND WATER QUALITY AND QUANTITY

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volumes of untreated or minimally treated stormwa-ter rapidly discharge into ground and surface waters.

There are better ways to manage stormwater that aimto replicate the predevelopment hydrology of a site.These approaches also seek to mimic nature’sprocesses for treating stormwater. In this scenario,stormwater management becomes an integral part ofsite and building design, rather than an afterthought.

This new stormwater management paradigm can befound under the umbrella of Low Impact Develop-ment (LID), pioneered in Prince George’s County,Maryland. LID is a hydrology-based approach to landdevelopment that is designed to reduce impacts onwatersheds and other aquatic resources through the

6 • 5


Half of Michigan’s residents rely on ground waterfor their drinking water. That’s why the MichiganGround Water Stewardship Program (MGSP), with-in the Michigan Department of Agriculture’sEnvironmental Stewardship Division, has been cre-ated as a cooperative effort designed to reduce therisks of ground water contamination associatedwith the use of pesticides and nitrogen fertilizers.The program is funded through fees that areassessed on sales of pesticides and nitrogen fertiliz-ers. More than $3 million annually is distributedthrough a competitive grants process to local stew-ardship teams that set local ground water protec-tion priorities based on local needs.

The MGSP, which is voluntary, locally driven, anddesigned to address the concerns of individuals,offers community outreach and educationthroughout the state to address a number ofground water-related issues, including environ-mentally friendly lawn care. With the goal of edu-cating everyone, not just farmers, MGSP seeks toenlighten residents that what they do on theirproperty can have an impact far beyond it.

Lawn care practices are a major source of stormwa-ter runoff and ground and surface water pollution.Residents learn that fertilizers and pesticidesapplied on their on land can move off site andeventually get into the waters that make up theirwatershed. Rather than just putting an ordinance

in place, MGSP helps homeowners evaluate theirlawn management in light of its impact on waterresources. They learn about relatively simple thingsthey can do to help the environment—startingwith their own lawns and yards. MGSP’s tipsinclude:

• Use native plants to create “rain gardens” nearstorm drains in their yards and natural bufferstrips along shorelines and drainage ditches tofilter out pollutants before they reach the water-shed.

• Before purchasing fertilizer, have a soil test doneto determine soil needs.

• Maintain septic systems properly and locatecompost piles far from waterways,

• Cut grass high, at about 3 to 4 inches. (Studiesperformed at Michigan State University’sHancock Turfgrass Research Center show thatwith a higher cut, lawn quality is improved andnutrients and other contaminants are kept onthe property, rather than running off. A highercut also reduces weed competition, improvesdrought tolerance and promotes beneficialinsects.)

• Mulch fallen leaves into the lawn and returnclippings to the turf to recycle the nutrients.

For more information, go to:http://www.kbs.msu.edu/mgsp/

MICHIGAN GROUND WATER STEWARDSHIP PROGRAM SPREADING THE WORD ONECO-FRIENDLY LAWN CARE

A rain garden in the MarcyHolmes Neighborhood ofMinneapolis, Minnesota.

Rain gardens are designedto slow down, capture,

and absorb water usingelements similar to thosein nature—plants, rocks,

shallow swales anddepressions—that hold

water temporarily ratherthan let it quickly drain or

run off. Rain gardensreduce drainage and

flooding problems, keeppollutants out of the near-

by streams, rivers, andlakes, and bring beauty

and wildlife to thelandscape. Ph

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use of a variety of best management practices(BMPs). It is based on the premise that natural sys-tems can accomplish a great deal if they are not over-whelmed with large volumes of stormwater or inordi-nate pollutant loadings.

A key aspect of LID is reducing the amount of imper-vious surface on development sites, thus reducing theamount of runoff that must be managed. Thisapproach relies on thoughtful site design, decentral-ized stormwater management, native vegetation,landscaping, and small-scale hydrologic controlsdesigned to minimize, capture, treat, and infiltratestormwater.

LID stormwater BMPs can involve one or a combina-tion of strategies. For example:

• Reducing impervious surfaces to decrease sur-face runoff and promote stormwater infiltrationinto the ground. This often involves protectingand encouraging trees and open space, mini-mizing pavement, and using permeable surfaces(e.g., permeable pavement, turf block, gravel).

• Disconnecting impervious areas by directingrunoff elsewhere (e.g., directing residential

downspouts to landscaped areas or rain barrels,and eliminating roadside curbs, where appro-priate, to allow water to run off over the shoul-der).

• Intercepting stormwater by capturing rainwaterbefore it comes into contact with an impervioussurface (e.g., trees, ecoroofs, roof gardens).

• Detaining and infiltrating stormwater in smallvegetated areas, allowing it to soak into theground or move more slowly into the storm sys-tem (e.g., planter boxes, infiltration basins,swales, soakage trenches, drywells, rain gar-dens).

LID seeks to design the developed environment sothat it remains a functioning part of the hydrologicsystem. It provides technological tools to plan anddevelop most types of urban sites to maintain orrestore a watershed’s hydrologic and ecological func-tions. It is an important means for maintainingstream baseflows, minimizing loss of recharge toaquifers, maintaining stream and wetland buffers,addressing flood concerns, and reducing stormwaterpollutant loads from developed areas.

6 • 6

A system of stormwater infiltration ponds in the Uplands neighborhood of North Bend, Washington.

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It is important to note, however, that while many LIDtechniques effectively manage stormwater, they arenot always applied from the perspective of potentialimpacts to the three-dimensional watershed, whichincludes ground water. Without considering groundwater, even LID techniques can allow pollutedstormwater to impact ground water.

RECHARGE WITH CARE

While the LID approach has both strong environ-mental benefits and great possibilities to enhance thedeveloped landscape, it can pose a threat to groundwater if we are not careful. As discussed earlier,stormwater, particularly from urban areas, containshigh concentrations of contaminants that may not beadequately removed or attenuated when stormwateris infiltrated into the ground. As techniques that cap-ture, treat, and infiltrate stormwater onsite continueto be developed, improved, and widely used, federaland state regulators and local communities must keepin mind these potential impacts by consideringaquifer sensitivity, the quality of stormwater, and thepotential impact of stormwater on ground water.

Infiltration drainage systems typically allow stormwa-ter from impervious surfaces to be temporarily storedand then released into ground water over a period oftime. However, a New Jersey study found that “infil-tration of storm water through detention and reten-tion basins may increase the risk of ground watercontamination, especially in areas where the soil issandy and the water table shallow, and contaminantsmay not have a chance to degrade or adsorb onto soilparticles before reaching the saturated zone” (Fischeret al., 2003).

An 18-month study monitoring swales and detentionpond systems receiving stormwater runoff frominterstate highway, residential, and commercial land-use areas in Florida found that most stormwater canlikely be infiltrated with minimal impacts (Harper,1988). The study indicated that removal processes insoils are likely to reduce most infiltrated pollutants;however, some pollutants are more likely to causeproblems than others, and these must be more care-fully considered in infiltration projects. The authorcautions that critical pollutant source areas should beavoided and that pretreatment before infiltration to

remove particulate forms of the pollutants should beconsidered.

Concerns associated with stormwater infiltrationinvolve the design life of the systems and the potentialto contaminate ground water if they are not appliedappropriately and monitored and maintained so theyfunction as intended. Earlier generations of infiltra-tion BMPs (e.g., infiltration trenches, retentionponds) tended to clog with silt, largely because theywere not properly sited, designed, installed, ormaintained. Once clogged, such systems do not workand may even degrade surface water quality by allow-ing resuspended sediment to run off into receivingwaters. (NHDES, 2001)

A big issue is that while there is more and more inter-est in using infiltration BMPs, we have relatively littleinformation on the transport of pollutants aroundand through infiltration systems. What is the risk toground water resources from recharging pollutedstormwater? There are situations where infiltration issimply not suitable because the potential to contami-nate ground water is too great (e.g., stormwater fromindustrial sites, petroleum storage facilities).

6 • 7


This development project in Minnesota uses several methodsof managing stormwater to mitigate negative impacts towater quality. The grassy swale area provides filtrationbefore stormwater recharges the underlying aquifer.

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A study by Robert Pitt and colleagues (1994) foundthat some pollutants in stormwater may have animpact on ground water in certain circumstances.These pollutants include nutrients (e.g., nitrates), pes-ticides (e.g., lindane and chlordane), other organics(e.g., 1,3-dichlorobenzene, pyrene, fluoranthene,VOCs), pathogens, heavy metals (e.g., nickel andzinc), salts (e.g., chloride, road salts). (See Table 1.)

Pollutant threats vary with land uses and humanactivities. For example, as detailed in the study, pesti-cides tend to be found in urban runoff from residen-

6 • 8

Rain in Fisherville, Kentucky, and a strip mall in Lexington,Kentucky. Ground water quality in Kentucky is generally good;water quality is directly related to land use, geology, groundwater sensitivity, and well construction. Nonpoint-source impactson ground water quality from anthropogenic sources occur pri-marily from nutrients and pesticides associated with agriculturalactivities. In addition, urban sprawl and stormwater runoffimpact karst aquifers and improper stormwater injection in karstareas also impacts local karst ground water quality.Ph

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Nutrients

Pesticides

OtherOrganics

Pathogens

HeavyMetals

Salts

nitrates

2,4-Dγ-BHC (lindane)malathionatrazineChlordanediazinon

VOCs1,3-dicloro-

benzeneanthracenebenzo(a)

anthracenebis(2-ethylhexyl)

phthalatebutyl benzyl

phthalatefluoranthenefluorenenaphthalenepentachlorophenolphenanthrenepyrene

enterovirusesShigellaPseudomonas

aeruginosaprotozoa

nickelcadmiumchromiumleadzinc

chloride

mobile

mobileintermediatemobilemobileintermediatemobile

mobile

lowintermediate

intermediate

intermediate

lowintermediateintermediatelow/inter.intermediate intermediateintermediate

mobilelow/ inter.

low/ inter.low/ inter.

lowlowinter/very lowvery lowlow/very low

mobile

low/moderate

lowmoderatelowlowmoderatelow

low

highlow

moderate

moderate

low/moderatehighlowlowmoderatemoderatehigh

likely presentlikely present

very highlikely present

highlowmoderatemoderatehigh

seasonally high

high

likely lowlikely lowlikely lowlikely lowvery lowlikely low

very high

highmoderate

very low

likely low

moderatehighlikely lowmoderatelikely lowvery lowhigh

highmoderate

moderatemoderate

lowmoderatevery lowvery low high

high

low/moderate


low

lowlow

moderate

moderate

lowmoderatelowlowmoderatemoderatemoderate

highlow/moderate

low/moderatelow/moderate

lowlowlow/moderatelowlow

high

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lowlow low lowlowlow

low

lowlow

low

low

lowmoderatelowlowlowlowmoderate

highlow/moderate

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lowlowlowlowlow

high

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low

highlow

moderate

moderate

low/moderatehighlowlowmoderatemoderatehigh

highhigh

highhigh

highlowmoderatemoderatehigh

high

SurfaceInfiltration withSedimentation

SubsurfaceInjection withMinimal Treatment

SurfaceInfiltration andNo Pretreatment

Fraction Filterable

Abundance inStormwater

Mobility(sandy/loworganic soils)

Table 1. A summary of the pollutants found in stormwater that may cause ground water contamination problems for variousreasons. Source: Robert Pitt et al., 1994.

Pollutants Compounds

POTENTIAL OF STORMWATER POLLUTANTS TO CONTAMINATE GROUND WATERContamination Potential

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tial areas, especially in dry weather flows associatedwith landscaping irrigation runoff. Volatile organicsare mostly found in industrial areas. Zinc is oftenfound in roof runoff and areas where galvanizedmetal comes into contact with rainwater. Road saltsare at their greatest concentrations in snowmelt andearly spring runoff in northern areas.

The Pitt study emphasizes that control of these com-pounds requires various approaches, includingsource-area controls, end-of-pipe controls, and pollu-tion prevention. However, “with a reasonable degreeof site-specific design considerations to compensatefor soil characteristics, infiltration may be very effec-tive in controlling both urban runoff quality andquantity problems.” In keeping with the LIDapproach to stormwater management, the studyencourages use of the natural filtering and sorption

capacity of soils to remove pollutants, but cautionsthat the potential for some types of urban runoff tocontaminate ground water through infiltrationrequires some restrictions, including adequate pre-treatment or diversion of polluted waters away frominfiltration devices.

Stormwater infiltration is of greater concern nowbecause federal stormwater requirements under theNational Pollutant Discharge Elimination System(NPDES) encourage infiltration of stormwater as ameans of avoiding an NPDES permit for a dischargeto surface water, and because more states are recogniz-ing the potential for reducing hydrologic impacts ofurbanization by recharging a prescribed amount ofstormwater.

6 • 9


LEMON GROVE, CALIFORNIA’S, STANDARD URBAN STORMWATER MITIGATIONPLAN (SUSMP) INCLUDES RESTRICTIONS ON INFILTRATIONThe City of Lemon Grove,California, has adopted a localordinance that includes the guid-ance contained in USEPA’sPotential Ground Water Con-tamination from Intentional andNon-Intentional Stormwater In-filtration (EPA/600/R-94/051).Step 10 of the ordinance addresses restrictions onthe use of infiltration BMPs. This provision statesthat three factors significantly influence the poten-tial for urban runoff to contaminate ground water:pollutant mobility, pollutant abundance in urbanrunoff, and the soluble fraction of the pollutant.The risk of ground water contamination may bereduced by pretreating urban runoff. At a mini-mum, stormwater infiltration BMPs must meet thefollowing conditions:

• Urban runoff from commercial developmentsmust undergo pretreatment to remove bothphysical and chemical contaminants prior to infil-tration.

• All dry weather flows must be diverted from infil-tration devices.

• Pollution prevention and source control BMPsmust be implemented at a level appropriate toprotect ground water quality at sites.

• The vertical distance from the base of any infil-tration structural treatment BMP to the seasonalhigh ground water mark must be at least 10 feet.

• The soil through which infiltration occurs musthave physical and chemical characteristics thatare adequate for proper infiltration durationsand treatment of urban runoff for the protectionof ground water beneficial uses.

• Structural infiltration treatment BMPs may notbe used for areas where there is industrial orlight industrial activity and other areas wherethere is a high threat to water quality land usesand activities.

• The horizontal distance between the base of anyinfiltration structural BMP and any water supplywells must be 100 feet.

Where infiltration BMPs are authorized, their per-formance must be evaluated for impacts on groundwater quality. In those instances where the City hasdetermined that implementation of proposed infil-tration BMPs has the potential to impact groundwater quality in another jurisdiction, the City mayrequire that a notification be placed upon thoseproposing such use in addition to the required pro-tection measures.Source: www.ci.lemon-grove.a.us/documentview.asp?DID=97


6 • 10

THE UNIVERSITY OF NEW HAMPSHIRE STORMWATER CENTER

DEDICATED TO PROTECTING WATER RESOURCES THROUGH EFFECTIVE STORMWATER MANAGEMENT

The UNH Stormwater Center, funded by theNational Oceanic and Atmospheric Administration(NOAA) through a grant from the CooperativeInstitute for Coastal and Estuarine EnvironmentalTechnology (CICEET), studies stormwater-relatedwater quality and quantity issues. The center’s mis-sion is to:

• Test stormwater control measures.

• Disseminate test results and evaluations.

• Demonstrate innovative stormwater manage-ment technologies.

One unique feature is its field research facility usedto evaluate and verify the performance of stormwa-ter management devices and technologies.

This facility serves as a site for both testing storm-water treatment processes and performing tech-nology demonstrations. The testing results andtechnology demonstrations serve a vital role formunicipalities, town engineers, and others chargedwith developing and implementing stormwatermanagement plans. The purpose of the stormwatermanagement plans is to reduce nonpoint-sourcepollution, the nation’s single largest water qualityproblem.

The research facility houses three categories ofstormwater treatment processes: conventionalstructural devices, low-impact development de-signs, and manufactured devices. In addition to itsmain field facility, center researchers are planningtwo other field projects: a porous pavement park-ing lot (already built and being tested) and a street-vacuuming study. Both of these projects representmeasures to treat and/or minimize stormwater atthe source, rather than after it is collected.

The center’s research program has three mainobjectives: (1) to provide rigorous independentevaluations of stormwater treatment technologies,(2) to aid municipalities and others charged withdeveloping and implementing stormwater manage-ment plans in compliance with Phase II of the CleanWater Act, and (3) to address concerns that havesurfaced as the result of research.

Visit the UNH Stormwater website at:www.unh.edu/ erg/cstev/

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An assortment of stormwater treatment technologies.

WHO REGULATES STORMWATERRECHARGE?

States can and do play an important role in control-ling and overseeing stormwater discharges to groundwater. In a 2005 Ground Water Protection Council(GWPC) survey of state regulatory personnel, morethan half of the states that responded indicated thatthey encourage stormwater infiltration, where feasi-ble, over surface discharge.

The majority of responders indicated that some typeof authorization is needed for installing unitsdesigned to direct stormwater into the subsurface,both infiltration systems and direct discharge sys-tems. The type of authorization required rangeswidely, from UIC rule authorization to different per-mitting mechanisms, such as sensitive area permits,stormwater general permits, or individual permits.Several states have enhanced protection/restrictionsfor introducing stormwater into the subsurface (moreprotective or otherwise segregated) in or near sourcewater protection areas, wellhead protection areas,vulnerable aquifers, or other sensitive ground waterareas.

Site-specific case studies have documented groundwater contamination from stormwater drainagewells. States need this information in order to regu-late stormwater discharges to ground water in a waythat maintains ground water availability while pre-venting contamination. USEPA’s current stormwaterguidance, Potential Ground Water Contamination

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FEDERAL STORMWATER REGULATION

In 1987, Congress amended the Clean Water Act tocreate, in two phases, a comprehensive nationalprogram for addressing stormwater discharges.Phase I extended the National Pollutant DischargeElimination System (NPDES) to require permits forstormwater discharge from a large number of pri-ority sources, including medium and large munici-pal separate storm sewer systems (MS4s) that serveurbanized areas and several categories of industri-al activity, including construction activity.

The Stormwater Phase II Final Rule (December1999) expands the Phase I program by requiringoperators of smaller systems and small construc-tion sites to implement programs and practices tocontrol stormwater runoff. Under Phase II, hun-dreds of urbanized communities, as well as institu-tions (e.g., public universities, state highway facili-ties, prisons) that have separate storm sewer sys-tems are regulated. To comply, they must developcomprehensive stormwater management pro-grams that include:

• Educating and involving the public.

• Finding and removing illicit discharge connec-tions such as sanitary sewage being routed intostorm sewers.

• Controlling runoff from construction sites dur-ing and after construction.

• Preventing stormwater pollution at municipalfacilities.

Storm water structures along roadways cancapture hazardous materials from cata-

strophic spills (either intentional or uninten-tional). This photo shows how a hazardous

materials trap (HMT) can be sited within thefootprint of the storm water control struc-

ture (a sand filter in this case) to both treatstormwater and collect hazardous material.

Note that the invert of the openings fromthe splitter box to the HMT is set slightlylower than that of the openings into the

sedimentation basin, allowing any hazardousspills as well as the first flush of runoff to be

captured by the HMT. Once the HMT is full,the backwater level rises and allows the

remaining runoff to enter the sedimentationbasin directly. HMTs must be drained after arain event (either manually or by use of an

automatic siphon device).


from Intentional and Nonintentional StormwaterInfiltration (Pitt et al., 1994), developed under theNPDES stormwater program, is probably not suffi-ciently protective of ground water. For example, theguidance promotes the use of Class V stormwaterdrainage wells as BMPs to prevent the release of pol-lutants to surface waters. However, the placement ofdiverted stormwater underground via such wells mayendanger underground sources of drinking water.

States need state-of-the-art technical and best man-agement practices guidance to protect ground waterfrom stormwater discharges. At a minimum, a com-plete compilation and synthesis of case studies onground water contamination from stormwater dis-charges is needed. It is inefficient for the states toindividually research this subject whenever they arerevising their stormwater rules and/or guidance,when much of the same research could be appliednationally.

Another federal and state regulatory issue related toground water impacts from stormwater is the defini-tion of Underground Injection Control (UIC) Class Vwells. Based on the definition published in the 1999Class V Rule, stormwater Class V wells includestormwater drainage structures that are wider than

they are deep, such as improved sinkholes andsubsurface fluid distribution systems.

Yet there are still some categories of stormwaterdrainage structures that fall into a gray area as towhether they are considered Class V wells. Thus,they may present risks to underground sources ofdrinking water similar to those posed by Class Vstormwater drainage wells. Federal and state UICClass V Programs and NPDES StormwaterPrograms must work together to clarify suchissues and educate communities on how to bestmanage and regulate stormwater to protect allwater resources effectively.

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Infiltration basins can be a very effective technique for con-trolling urban runoff quality and quantity problems. However,because of the potential for some types of urban runoff tocontaminate ground water through infiltration, some restric-tions are needed, including site-specific designs that considersoil characteristics.

Two green roofs in Chicago, Illinois. In addition to their ecological,aesthetic, and temperature-moderation values, green roofs dramati-cally reduce the volume of stormwater runoff and the peak flowrate. Rapid runoff from roof surfaces can result in flooding,increased erosion, and the discharge of contaminants directly intosurface and ground water. A green roof can absorb stormwater andrelease it slowly over a period of several hours. The bottom photoshows a prairie twelve stories up on the roof of Chicago’s City Hall.

One factor that may have a bearing on how statesapproach stormwater infiltration is a determinationas to whether infiltration is considered to be an“aquifer recharge system” or a “stormwater disposalsystem.” The GWPC survey indicates that the majori-ty of states view stormwater infiltration as disposal,suggesting that recharge is not addressed with thesame level of concern for ground water as it would ifit were treated as a drinking water source. State drink-ing water, UIC, and stormwater regulatory programsneed to coordinate the manner in which they controlstormwater discharges to ground water. They alsoneed stormwater monitoring (surface or groundwater) requirements for units that infiltrate or direct-ly discharge stormwater to ground water.

LOCAL REGULATION IS THE KEYTO STORMWATER MANAGEMENT

The day-to-day work of managing stormwater rests,for the most part, with local governments. In fact,communities may have several stormwater require-ments that they must meet. For example, the federalNPDES Stormwater Phase II requirements requiremany urban communities to develop comprehensivestormwater management programs. States may alsohave comprehensive stormwater manage-ment policies or requirements thatcommunities must meet. However,both must have a ground watercomponent to be fully effective.

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THE STORMWATER UTILITY ALTERNATIVE

An alternative to private ownership with publicoversight of stormwater BMPs is for the municipal-ity to take ownership and maintenance responsibil-ity for all stormwater BMPs, assessing an annual feeto cover all costs (e.g., maintenance, repair). Agrowing number of communities nationwide haveestablished stormwater utilities so they can assessfees to fund their stormwater systems and annualmaintenance costs and provide a wide range ofservices. The utility approach may, in fact, be one ofthe most effective ways to ensure BMP mainte-nance and consequently intended performance.

Washburn, Wisconsin’s, Storm WaterManagement UtilityUntil the heavy rainfalls of 2000 and 2001, whichcaused considerable public and private propertydamage, the City of Washburn, Wisconsin, was ableto ignore stormwater management issues. Witheach passing storm, however, it became moreapparent that existing stormwater conveyance sys-tems could not handle regularly occurring runoffand that long-range plans and the use of appropri-ate BMPs were needed to minimize future prob-lems.

Washburn needed a stormwater management sys-tem that would retain water on the properties thatgenerate storm water, wouldn’t overload con-veyance and handling systems, and would elimi-nate flooding and minimize environmental degra-dation, thereby improving living conditions in thecity. Regardless of their location in the watershed,the city recognized that all properties have animpact on stormwater drainage and that stormwa-ter needed to be viewed from a total managementperspective. Much research and deliberation madeit clear that a stormwater utility would allow forsuch an approach.

The City of Washburn’s Storm Water ManagementUtility went into operation in 2006. It is self-sup-porting, just like the city’s water and wastewaterutilities. Revenue collected from utility services isdedicated solely to stormwater management. Themonthly utility fees pay for the operation, mainte-nance, and capital improvements of the system. Thecharge also provides an incentive for the largestgenerators of storm water—commercial, industrial,and institutional properties—to incorporate BMPswithin their properties.

Source: http://www.cityofwashburn.org/storm.htm


But when it comes right down to it, communitiesneed to develop their own comprehensive stormwatermanagement programs. Local governments are mak-ing the land-use decisions that will either make orbreak the health and well-being of their waterresources. Local governments need to recognize thatthey have this responsibility and develop storm sewermanagement programs that address the followingissues:

• How to assess existing stormwater patterns.

• How to mitigate existing runoff threats tosource water areas.

• How to ensure that future development will notexacerbate stormwater impacts in the watersupply watershed.

• How to take into account the cumulativeimpacts of runoff on the water supply region orwatershed.

• How to change public and political attitudestoward the value of and need for an effectivestormwater management program.

• How to fund an effective stormwater manage-ment program.

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Abacoa, Florida’s, stormwater runoff is managed within a greenway system that provides filtration and allows recharge locally.The higher density homes allow the developers to preserve more open space.

Source: http://www.epa.gov/smartgrowth/case/abacoa_p2.htm

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To USEPA:

Establish better coordination among federal stormwater management,ground water protection, underground injection control (UIC), and water-quality monitoring programs so that programmatic overlaps and opportu-nities for collaboration in protecting surface and ground waters can beidentified and initiated.

Accord the protection and recharge of ground water and protection of sur-face water equal importance when regulating and providing guidance tostate stormwater programs. For example:

• Develop and field-test BMPs specifically designed to manage stormwaterin a manner protective of ground water in different hydrogeological set-tings (e.g., karst, sand and gravel).

• Ensure that states may utilize §319 funds to conduct research anddemonstration projects, and to develop and field-test BMPs specificallydesigned to manage stormwater in a manner that is protective ofground water.

To State Agencies:

Establish better coordination among stormwater management, groundwater protection, underground injection control (UIC), and water qualitymonitoring programs so that programmatic overlaps and opportunities forcollaboration in protecting surface and ground waters can be identifiedand initiated.

Review stormwater management plans and total maximum daily load(TMDL) determinations from a ground water program perspective toensure protection and conservation of the resource.

To Local Governments:

Protect all water resources through local stormwater management activi-ties, and require the use of stormwater BMPs (including ongoing mainte-nance and monitoring), stormwater utilities, and stormwater managementplans that are designed to conserve and protect both surface water and

ground water and promote natural ground water recharge.

Recommended Actions

A thunderstorm over Chaparral, New Mexico.

Photo: Greg Lundeen

Source: http://www.srh.noaa.gov/elp/swww/v8n1/Chaparral%20Supercell%202.JPG


6 • 16

Section 6 References: Ground Water and Stormwater Management Fischer, David, E. G. Charles, A. L. Baehr. May 2003. “Effects of Stormwater Infiltration on Quality of Ground water

Beneath Retention and Detention Basins” Journal of Environmental Engineering 129, no. 5.

GWPC. 2005. State Regulation and Research on Storm Water Impacts to Ground Water.

Harper, H. H. 1988. Effects of Stormwater Management Systems on Groundwater Quality. Final Report to the FloridaDepartment of Environmental Regulation. Available at: http://stormwaterauthority.org/assets/115PGroundwater.pdf(accessed July 2007).

NHDES. 2001. Managing Stormwater as a Valuable Resource . Available at: www.des.state.nh.us/dwspp/stormwater.pdf(accessed July 2007).

Pitt, Robert, S. Clark, K. Parmer. 1994. Potential Groundwater Contamination from Intentional and NonintentionalStormwater Infiltration. USEPA. EPA/600/SR-94/051 Available at: http://www.p2pays.org/ref/07/06744.pdf

Stormwater-Related Websites:USEPA Stormwater website: http://cfpub.epa.gov/npdes/home.cfm?program_id=6

National Stormwater BMP Database: www.bmpdatabase.org

Bioretention and Stormwater ResearchPublications: http://www.ence.umd.edu/~apdavis/LID-Publications.htm

Low Impact Development Center: http://www.lowimpactdevelopment.org/

Stormwater journal: http://www.forester.net/sw.html

Stormwater Authority: http://www.stormwaterauthority.org/

Suggested ReadingLow-Impact Development Design Strategies An Integrated Design Approach. EPA 841-B-00-003.

Low-Impact Development Hydrologic Analysis. EPA 841-B-00-002.

Using Smart Growth Techniques as Stormwater Best Management Practices. EPA 231-B-05-002.

Ground water is a crucial resourcefor Hawaii. It provides over 90%of the fresh drinking water forisland residents and is used forcommercial, agricultural, recre-ational, industrial, and thermo-electric power activities.Precipitation, the source ofHawaii's fresh ground water, isnaturally filtered as it infiltratesthrough the soil. Favorable geo-logic factors (i.e., the content,structure and extent of Hawaii'svolcanic rock) and hydrologic fac-tors (i.e., reliable rainfall, rechargecapacity, recharge rates) con-tribute to the high quality ofground water. The state also man-ages stormwater quality throughits nonpoint-source pollution con-trol program, protecting groundwater by controlling surface waterpollution, recognizing the inter-connection between surface andground water.Ph

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