Rating System

LEED BD+C: New Construction, LEED BD+C: Core and Shell, LEED BD+C: Schools

Rating System Version

v3 - LEED 2009, v2 - Schools 2007, v2 - LEED 2.2

Inquiry

Short of credit acceptance, please comment on whether the following conditions are likely to be sufficient for compliance, and if not what additional measures would need to be taken. Reduce Impervious Cover: The subject site is part of Mark Center Plaza 1, which is part of a larger development, the Mark Center area of Alexandria. The Winkler Botanical Preserve Pond, treats runoff from the subject site as well as a large portion of the Mark Center area, was designed and constructed with future urban development in mind and with a purpose of treating stormwater runoff from a large, relatively impervious urban area. Prior to construction of the Winkler Botanical Preserve Pond, which treats all runoff from the subject site, the Winkler Botanical Preserve was created. This preserve was created as part of the development of Mark Center Plaza 1A & 1B (which includes the subject site) and is approximately 40 acres of undeveloped, forested land which was dedicated to the City of Alexandria as an area that cannot be developed in the future. Because such a large area of land, which is located adjacent to the subject property and helps to treat runoff from the subject site before it enters the Winkler Botanical Preserve Pond, has been dedicated for preservation, the stormwater management plan for the Mark Center area, which includes the subject site, includes significant steps to reduce impervious area in an urban setting to the greatest extent possible. Promote Infiltration: The subject site provides approximately 30% vegetated open space, which helps to promote infiltration. In addition, all runoff from the subject site is conveyed via open channels through the above referenced Winkler Botanical Preserve and into the Winkler Botanical Preserve Pond. Because all runoff from the site flows through open channel streams in an undeveloped setting that has been designed to reduce velocities to the greatest extent possible, a significant amount of runoff leaving the site will infiltrate prior to reaching the Winkler Botanical Preserve Pond. BMPs Treat Runoff Capable of Removing 80% Total Suspended Solids: As mentioned above, runoff from the subject site flows into Winkler Botanical Preserve Pond, which is a wet pond. Virginia and City of Alexandria Stormwater Management regulations are designed to promote removal of Phosphorus in lieu of Total Suspended Solids (TSS), so the design of the pond was not intended to quantify removal of TSS. However, as shown on the attached research summary, studies have shown that wet ponds remove 80% - 90% of total suspended solids. Detailed calculations will be provided to quantify TSS removal and demonstrate that the Winkler Botanical Preserve Pond does remove 80% TSS.