Storm Water Quality & Dry Wells

On average it only rains about seven inches a year. There are two completely separate sewer systems in Gilbert and in most of the surrounding municipalities.

• There is a sanitary sewer that collects waste from homes and businesses from the sinks, toilets, showers, and baths. From there the waste water goes through pipes to a waste water treatment plant.
• Then there is the storm sewer that includes the gutters, streets, retention basins, drywells, and other storm sewer structures. The water and other things that enter the storm sewer aren't treated for contaminants, it goes right into the ground via infiltration into the soil or though a drywell.

Municipal Permits

The Clean Water Act (CWA), among other things, regulates storm water and urban runoff to protect water quality. The Phase II Final Rule requires small municipal storm sewer systems (MS4s) such as Gilbert to obtain a permit which specifies the measures that will be taken to prevent pollution from entering the storm system. In Arizona, Phase II permits are administered by the Arizona Department of Environmental Quality (ADEQ). Links outside of Town of Gilbert website

There are several requirements imposed on Gilbert by the permit including having a Storm Water Management Plan (SWMP). Gilbert is required to prohibit non-storm water discharges into the storm sewer system and to implement enforcement procedures.

The SWMP also mandates that Gilbert require construction sites to:

• implement erosion, sediment, and waste control measures
• address post construction runoff from new development and redeveloped projects

In order to meet these requirements, the Gilbert Town Council adopted Ordinance 1590 on August 3, 2004. The SWMP includes six Minimum Control Measures with best management practices (BMPs) and measureable goals for each:

Public Education and Outreach
Public Participation/Involvement
Illicit Discharge Detection and Elimination
Construction Storm water Runoff Controls
Post Construction Storm Water Management
Pollution Prevention

Download Information

Storm Water Management Fact Sheets

What you should know…

Water is a precious commodity in the desert, as we have learned during drought years. As our Town grows, there will be an ever-increasing need to protect our water resources from pollutants. Each of us can share in that responsibility by taking simple measures to ensure that our daily activities help to protect our water resources.

Water flowing over streets and other surfaces picks up sediment and pollutants and carries them into the storm drainage system. Storm drains are flood control systems designed to carry rainwater from streets and properties in order to prevent flooding after a heavy rain. Unlike the sanitary sewer system, the storm drain system does not connect to a wastewater treatment plant, but flows directly into local waterways or retention basins, many of which are parks were children and pets play.

Without good storm water management, pollutants can enter our waterways where they can have a harmful impact on water quality and the environment. Discharges that can introduce pollutants into our waterways through storm water runoff include soaps, automotive fluids, litter, sediment, pesticides and many other materials washed off roadways, sidewalks, buildings, vehicles and other equipment.

Not only can pollutants enter our waterways, they can also be directly injected into our groundwater. Drywells are bored holes, deeper than they are wide. Drywells play an important role in stormwater management by quickly and effectively allowing water to infiltrate into the ground. Because of this function they are also direct conduits for water carrying pollutants into the ground water.

It is easier and cheaper to prevent storm water pollution than to clean it up. The Town of Gilbert has adopted a Storm Water Management Program that includes public outreach and education of its residents and local businesses, so that everyone can contribute to keeping our storm water system free from pollution.

Here are some fact sheets for general information, residents, and businesses in Gilbert. Check out Arizona Department of Environmental Quality’s (ADEQ) website Links outside of Town of Gilbert website or the Maricopa County Environmental Programs website for more information.

General Information for Everyone

Information for Residents

Information for Businesses

Other Stormwater Permits

ADEQ's Multi-Sector General Permit for Industry

ADEQ's multi-sector general permit (MSGP) is designed for discharges of storm water from certain industrial sites that are of a non-construction nature. The MSGP is one large permit divided into numerous separate sectors. Each sector represents a different type of activity and is dependent on its standard industrial classification (SIC) code or narrative description. Information on Facilities required to apply for a storm water permit and SIC codes can be found in 40 CDF 122.25(b)(14). The Environment Protection Agency (EPA) and the Arizona Department of Environmental Quality (ADEQ) Links outside of Town of Gilbert website provide further information on the MSGP.

ADEQ's General Permit for Construction

The construction general permit authorizes storm water discharges from large and small construction-related activities that result in a total land disturbance of equal to or greater than 1 acre (including smaller parcels that are part of a larger common plan of development or sale that are equal or greater than 1 acre) where those discharges enter surface waters of the U.S. or a storm drain.

Under the Arizona Pollutant Discharge Elimination System (AZPDES), the operator of a construction site is responsible for obtaining coverage for their site. The operator could be the owner, developer, general contractor or an individual contractor. Information, including a Notice of Intent (NOI) form Links outside of Town of Gilbert website and a Construction SWPPP checklist can be found on ADEQ's website. Information is also available on EPA's website.

**Important: A copy of the NOI and SWPP must be submitted to the Town of Gilbert.**

Dry Wells

What is a dry well?

A dry well is defined as a bored, drilled, or driven shaft or hole whose depth is greater than its width. A dry well is designed specifically for the alleviation of flooding and the disposal of storm water.

Why do we use dry wells?

Drywells are primarily used as a means of flood control here in the arid southwest. With our intense, short duration storms it is important to have a way to get that storm water off of the streets and away from buildings where it could do damage and be a safety hazard. Drywells are meant to be safe way of quickly disposing of flood waters by allowing quick infiltration into the ground.

Are dry wells regulated?

Yes. Dry wells are regulated by the Arizona Department of Environmental Quality (ADEQ). Arizona state law requires that all new, existing, or abandoned dry wells be registered with ADEQ.

Drywells can only receive storm water runoff or discharges that are exempted by A.R.S. § 49-250(23). If other fluids have been directed to the drywell, it is subject to the aquifer protection program (APP) and/or closure requirements and may be considered an underground injection well that requires both ADEQ and USEPA permitting. Spills to the drywell may also trigger permitting, clean closure, or enforcement actions. An APP permit is required for any drywell located in an area where hazardous substances, including motor fuels, are used, stored, treated or loaded.

Two important types of dry well permits available from ADEQ include:

Dry Well Permits
Type	Covers
2.01 Drywells that drain areas where hazardous substances are used, stored, loaded or treated.	Facilities with potential for spills of pollutants into those drywells
2.04 Drywells that drain areas at motor fuel dispensing facilities	Facilities where motor fuels Are used, stored, or loaded

For more information on Dry Wells

Visit ADEQ’s website Links outside of Town of Gilbert website

or call ADEQ's Drywell Unit at (602) 771-4385, if you have any questions regarding the registration or permitting of your dry well.

Care should be taken to eliminate common sources of pollutants to dry wells:

• Hot water heater drainage (should go to sanitation sewer)
• Dumping of excess chemicals, like oil, paint, cleaners, etc., on the ground or in the gutter (excess chemicals should be taken to Household Hazardous Waste Collection Event for proper disposal)
• Irrigation runoff containing excess pesticides/herbicides/ fertilizers these products should be applied following the instructions, excess chemicals that can no longer be used should be taken to the Household Hazardous Waste Collection Event)
• Detergent/oil from car and engine washing (engine washing should be performed at a self-serve car wash because they have an underground oil/water separator that collects the dirt and oil for proper disposal)

How can dry wells worsen environmental contamination?

Because of their design, dry wells, if not properly maintained can serve as a "straight-shot" conduit for ground water contamination. Dry wells use a filtration and sediment separation system that includes an upper settling chamber with an injection pipe and a lower rock fill section. As water drains into the dry well, the settling chamber slowly fills with water, allowing sediment to settle out and become trapped in the bottom of the chamber. The water then drains to an overflow (injection) pipe, is released to the bottom of the drywell, and slowly percolates down to the water table.

In urban areas, storm water frequently carries significant levels of petroleum products, pesticides, and other chemicals washed from streets and landscaped areas. Drywells are designed to prevent this pollution from reaching the water table but not be able to do so if not properly maintained. Storm water containing pollutants may drain into dry wells and percolate into the water table. This is one reason why it is important to make sure pollution does not enter the storm system. The storm system is composed of the streets, gutters, and retention basins just to name a few.

What other environmental problems are linked to dry wells?

A dry well that is not functioning properly can lead to improper drainage and the flooding of the area surrounding the dry well.

The resulting standing water can become a perfect breeding ground for mosquitoes. Mosquitoes can have a serious impact on the health, comfort, and economic welfare of people. Generally, a body of water that stands for more than three days will produce mosquitoes. In addition to inoperable dry wells, mosquito breeding sites can be caused by irrigated or poorly leveled yards and retention basins, bird baths, decorative ponds, improperly maintained swimming pools, and flood control drainage areas. More information on mosquitoes is available by visiting the Public Works Mosquito Control webpage.

What do I need to do to ensure proper dry well operation?

Chapter III, Article XI, Section 11.15 (Drywell Policy) of the Town's Unified Land Development Code states:

"It is the owner's responsibility to maintain drywells . . . Drywells that cease to drain a project within a 36-hour period are to be replaced with new ones where alternate methods of drainage are still not available.

It is important that property owners maintain their dry wells to ensure the efficient disposal of storm water.
Dry wells should be inspected and cleaned annually by a dry well services company to ensure proper operation.
In addition to regular inspections, dry well performance should be monitored more frequently during the monsoon season.
If drainage appears slow, or if water is standing for more than 36 hours, the system should be inspected by a dry well service company.
If it is determined that the dry well needs to be replaced, the Town's Community Development Department should be consulted for information on dry well replacement requirements.

Questions?

• For general information on dry wells, contact the Town's Environmental Program Section at (480) 503-6400.
• For information on the placement or replacement of dry wells, contact the Town's Community Development Department at (480) 503-6833.
• For regulatory information on dry wells, contact the ADEQ Dry Well Unit at (602) 771-4385.
• Access ADEQ's website
• For general information on the Town of Gilbert's mosquito control program, contact the Town's Wastewater Section at (480) 503-6400.
• For general information on mosquito control, call Maricopa County Vector Control at (602) 506-0700.
• For a copy of the Town's Mosquito Control brochure, contact Public Works at (480) 503-6400.