Detention Basin

Detention Basin POLLUTANTS ADDRESSED: Heavy Metals, Nutrients and Organics, Salinity, Sediments

DESCRIPTION: A detention basin is a constructed basin designed to collect and temporarily store water or waterborne debris or sediment.

ADDITIONAL BENEFITS: Flood protection POTENTIAL TREATMENT AREAS: Agricultural lands Developed lands

LOAD REDUCTION MECHANISM: Heavy Metal Reduction – Improves water quality by filtering pollutants from collected runoff using a combination of microbial soil processes, infiltration, evaporation, and plant uptake.

ALTERNATIVE MANAGEMENT MEASURES: Brush trench Silt fence Straw bale barrier Sloped drain

Nutrients/Organics Management- - see above Salinity Reduction – see above

PERMITTING REQUIREMENTS: Requirements vary by location. A permit under Section 404 and 401 of the Clean Water Act may be necessary.

Contact county regional flood control district.

Sediment Reduction – Suspended sediments settle within the basin.

LAND USE CLASSIFICATION: Disturbed areas Agricultural lands Urban areas

Arid Southwest BMP

Note: Retention Basins are not allowed in Arizona under ADWR rules. http://www.azwater.gov/azdwr/default.aspx.

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Detention Basin POLLUTANTS ADDRESSED: Heavy Metals, Nutrients and Organics, Salinity, Sediments

Level 500: INTENSE ENGINEERING LOAD REDUCTION POTENTIAL: LOW

MEDIUM

3. Effects on volume of discharge flow on the environmental, social, and economic conditions.

4. Effects on the water table downstream and the results of changes of vegetative growth.

5.

HIGH

ESTIMATED TIME FOR LOAD REDUCTION: IMMEDIATE

MONTHS2 YEARS

Effects on water quality to be considered:

> 2 YEARS

1. Effects on erosion, movement of sediment, pathogens, and soluble and sediment-attached substances that could be carried by runoff.

2. Effects on the visual quality of onsite and downstream water resources.

3. Effects of construction and early establishment of protective vegetation on the surface and ground water.

4. Effects on wetlands and water-related wildlife habitats.

EXPECTED MAINTENANCE: LOW

MEDIUM

HIGH

ESTIMATED COST: LOW

MEDIUM

Riparian Planting Zone: Upland Zone and Flood flows areas.

HIGH

PLANNING AND IMPLEMENTATION: Effects on water quantity to be considered: 1. Effects on the water budget, especially on volumes and rates of runoff, infiltration, evaporation, transpiration, deep percolation, and groundwater recharge.

2. Effects on downstream flows and aquifers that would affect other water uses and users.

Photo courtesy of ADEQ NPS Plan

Arid Southwest BMP

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