BMP Maintenance Brochure

WHY ARE BMPS NECESSARY, WHO ADDITIONAL INFORMATION Urban Stormwater MAINTAINS THEM, AND WHY DOES THE Links to the following resources can be found at: Best Management Practices CITY INPSECT THEM? http://alexandriava.gov/tes/DEQ/deqpublications.html (BMPs) Inspection Program The City of Alexandria Environmental • Alexandria Supplement to the Northern Virginia City of Alexandria, Virginia Management Ordinance implements the BMP Handbook City’s stormwater management program in • City of Alexandria BMP Maintenance Agreement A stormwater “Best Management Practice” compliance with the Virginia Stormwater (BMP) is a facility or structure that reduces Management Act and Chesapeake Bay • City of Alexandria Environmental Management the water quality impacts of stormwater Ordinance Preservation Act. These regulations runoff from developed areas. require the City to control the level of • City of Alexandria Master Plan Water Quality pollutants entering waterways such as the Management Supplement Potomac River and the Chesapeake Bay. Wet pond treating • “Stormwater Pollution and Management” brochure stormwater from a BMPs are designed to reduce pollutants shopping center such as sediments, oil, grease and nutrients. Examples of urban stormwater MAINTENANCE SERVICE PROVIDERS BMPs are wet and dry ponds, bioretention The City’s Division of Environmental Quality can areas, sand and storm filters, and provide BMP owners with a list of vendors who hydrodynamic separator devices. Regular have experience in maintaining stormwater maintenance is necessary for proper Trash inside an management facilities. overflow riser function and long-term viability. Please note that the City makes no representation or Ultra urban areas such as the City of warranties regarding the qualifications or suitability of Alexandria are densely developed areas any particular vendor, nor does a vendor's inclusion or with scarce open space and pervious non-inclusion on this list constitute any such surfaces. Underground stormwater storage representation or warranty. You should retain a maintenance company only after making a thorough and treatment practices such as sand Maintaining an review of that company's qualifications and its ability to underground BMP filters and hydrodynamic separators are service your particular needs. well suited because they require very little surface space. This brochure was developed to help As a requirement of development individuals and property owners approval, the City requires BMP owners to understand what BMPs are, their maintain their facilities (Article XIII, Section maintenance requirements, and the role of 13-109).This is stated in their maintenance For more information about this brochure and the City’s inspection program. agreement. The agreement conveys to stormwater BMPs, contact: BMPs are an important component of the successive landowners. City staff conducts City of Alexandria City’s stormwater management program inspections of BMPs to ensure facilities are Department of Transportation and which aims to reduce the impacts of storm- being maintained and functioning properly. Environmental Services water pollution on local water resources. Division of Environmental Quality Maintenance needs will vary according to 301 King Street, Room 3900 Alexandria, VA 22314 Department of Transportation and Environmental the type of facility and the drainage area Services, Division of Environmental Quality Phone: 703-838-4334 http://www.alexandriava.gov/tes/DEQ/ contributing to it. Owners should inspect http://www.alexandriava.gov/tes/DEQ/ their facilities every few months and after significant rainfall events. SAND FILTERS WET PONDS BMP INSPECTION AND MAINTENANCE NEEDS Urban sand filters are located in underground BMP INSPECTION AND MAINTENANCE NEEDS Wet detention ponds concrete vaults that have multiple chambers. The are constructed basins first chamber is for settling, the second chamber has that have a permanent BIORETENTION AREAS the filter and under lying drainage system, and the pool of water through- Bioretention areas, often referred to as rain gardens, are third is a discharge chamber or clear well. As storm- out the year, or at landscape features that store and treat stormwater runoff. water flows into the first chamber, large particles least during periods of Surface runoff is directed into shallow, vegetated settle out, finer particles and other pollutants are normal rainfall. depressions with removed as stormwater flows through the filter me- Pollutant removal Wet Pond underlying layers of dium. Pollutants are removed by physical filtration, occurs through soil, sand, and gravel. adsorption, and bacterial uptake. settling, as stormwater runoff is stored in the pond. These areas are Additional pollutant uptake of nutrients also occurs There are several design variations of sand filters designed to mimic through biological activity (i.e. algal uptake). Wet including: Delaware, DC, Austin, Alexandria natural ecosystems ponds are among the most cost-effective and Compound, and Dry Vault filters. where pollutant widely used BMP when space is available. removal occurs Access to sand filter Inside vault of sand filter through soil infiltration Recently installed Maintenance: bioretention area and plant uptake. They • Conduct routine mowing are commonly located • Keep embankments stable / fill animal burrows in parking lot islands or in residential open spaces. • Remove sediment from pond when necessary • Manage vegetation / seed and stabilize bare Maintenance: spots • Maintain vegetation and replace mulch as needed • Inspect and clean any mechanical components • Remove trash and sediment STORM FILTERS • Keep free of debris / remove trash • Watch for water standing > 72 hours which can indicate These BMPs are comprised of an underground • Keep risers, spillways and outlets clear clogging of subsurface layers and under-drain system concrete vault that houses media-filled filter cartridges. Pollution removal occurs through DRY PONDS mechanical filtration, ion exchange, and adsorption Dry detention ponds to the filter media. The vault has an under-drain sys- HYDRODYNAMIC SEPARATOR DEVICES are basins with out- tem to release treated stormwater. Examples of this Hydrodynamic separators are flow-through structures lets that have been type of BMP are StormFilter™ and VortFilter™. that have an insert chamber to trap sediments, oil and designed to store other pollutants. Water enters the vault insert and drops stormwater runoff for Inside StormFilter™ vault through a weir / pipe into a settling chamber where large a specified period of particles settle out. Examples of these devices are Dry Pond time, usually 48 Stormceptor™, Vortechnics™, AquaShield™, hours, to allow BaySaver™, and Downstream Defender™. particles and pollutants to settle. Unlike wet ponds, these facilities do not have a large permanent pool. Maintenance: ™ Filter Cartridge View inside Stormceptor Dry ponds can be planted with wetland vegetation • Check oil and sediment to provide additional nutrient and pollutant uptake. levels Maintenance for Sand and Storm Filters: • Clean out chamber when Maintenance: • Remove trash and sediment from chambers unit has reached capacity • Conduct routine mowing • Remove oil layer from permanent pool (this is performed with a • Keep embankments and slopes stable • Remove and replace top layer of sand filter and sump vac or vacuum underlying filter fabric • Remove sediment as necessary truck, depending on type Manage vegetation, seed and stabilize bare spots • Keep inlets and outlets clear of debris • of unit). See device’s • Fill animal burrows • Maintain wiring and pumps (if applicable) operation manual • Keep trenches / basin free of debris and trash • Replace media-filled filter cartridges • Remove trash and keep access • Keep risers, spillways and outlets clear • Maintain access areas (doors, grates, covers) areas clear of debris Access manhole cover • Watch for water standing > 72 hours .

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