Inspection of Stormwater Controls for Better Performance

Authors:

  • Ryan O’Banion - Hazen and Sawyer
  • Karlee Copeland - Fairfax County, VA

~70% (4,100 of the 6,000) of facilities in the Fairfax County inventory are privately owned and/or maintained. Privately owned facilities are inspected at least once every 5 years (~800/year).

Inspection services are characterized by three phases: pre-inspection data collection, field inspections, and remediation and reporting

A pilot study completed by Hazen and the County using 360° imagery as a tool for documenting the state of stormwater controls established the level of effort required to use 360° technology and highlighted additional benefits for inspectors.

To remedy ponding issues at bioretention sites, during design utilities should consider the use of berms (particularly for grassed bioretention) and lowering the grade of the media surface.

To properly maintain infiltration practices, utilities should: inspect pretreatment devices and the facility at least twice per year and remove sediment, trash and organic debris; remove any plants and trees from the facility as needed; replace pea gravel and topsoil when clogged

Design considerations for dry/wet ponds include a planting plan with clear zones and a limited palette and ensuring plantings are maintainable and appropriately sized trash racks are on each orifice.

To comply with conditions of a VPDES Phase I MS4 Stormwater Discharge Permit, Fairfax County, Virginia, inspects approximately 20% of its inventory of privately maintained stormwater controls every year. In support of this permit condition, comprehensive inspections were conducted for more than 500 constructed stormwater facilities, representing a combination of green infrastructure practices and conventional stormwater controls.

Inspection services are characterized by three phases: pre-inspection data collection, field inspections, and remediation and reporting. Hazen and Fairfax County worked together to compile the inspection reporting results into a database for analysis. Using this database, a number of key maintenance issues were consistently identified across the varying types of stormwater controls.

Preliminary findings suggest that the most frequent maintenance items across the multitude of stormwater controls include: insufficient or incorrect vegetation, insufficient mulch layers, bare spots or erosion, and trash, sediment, or debris. These findings and inspection methodologies can help other inspectors, designers, and municipalities ensure stormwater controls continue to function as designed.

For more information, please contact the author at robanion@hazenandsawyer.com.

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