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The Impact of Runoff Reduction Method on Land Developent Projects

By Tom Cook, PE, Project Manager, Koontz-Bryant, P.C.

On July 1, 2014 the Virginia Department of Environmental Quality (DEQ) began requiring that the impact of stormwater runoff from proposed land development activities be analyzed by the Runoff Reduction Method as part of the Virginia Stormwater Management Regulations (4 VAC 50-60).

In general terms, the more impervious area added to a land development project site, the greater the cost will be to implement the BMPs to meet the new State stormwater management regulations. Therefore, early evaluation of the potential BMP requirements to develop a site, as dictated by the Runoff Reduction Method, will be essential in estimating stormwater management design and construction costs and its potential effect on project feasibility.

The Runoff Reduction Method (RRM) is based on the effectiveness of various best management practices (BMPs) to reduce pollutant loads (phosphorous and nitrogen) to watersheds below land development/disturbance activities by reducing the quantity or runoff rate to pre-developed conditions. This approach to controlling increased stormwater runoff from land development sites is intended to simulate pre-developed stormwater runoff rates and pollutant loads from a proposed project site, which should ideally not adversely impact downstream natural conveyance channels and ultimately the Chesapeake Bay.

The RRM of stormwater runoff control also gives significant weight to minimizing the impervious cover (typically pavement and building area) and mass grading of sites that may occur with a proposed land development project. On small intensely developed project sites where open space may not be achievable, a series of BMPs may be needed to meet the required runoff reduction.

The DEQ is quick to point out that the Runoff Reduction Method is a planning tool for determining what BMP options may need to be utilized to offset the effects of adding impervious cover (increased runoff volume and pollutants) to a site within a given watershed.

For more information on Run Off Reduction Methods and the impacts to your projects, contact Tom Cook.