HomeMy WebLinkAboutSDP202200013 Correspondence Initial Site Plan 2022-03-29(Z)
Commonwealth of Virginia
VIRGINIA DEPARTMENT OF ENVIRONMENTAL QUALITY
1111 E. Main Street, Suite 1400, Richmond, Virginia 23219
P.O. Box 1105, Richmond, Virginia 23218
(800) 592-5482 FAX (804) 698-4178
www.deg.virgirda.gov
Travis A. Voyles Michael S. Rolband, PE, PWD, PWS Emeritus
Acting Secretary of Natural and Historic Resources Director
(804) 698-4020
MEMORANDUM
To: All Members of the Stormwater Management Development/Design Community,
All Local Virginia Stormwater Management Program Administrators
From: Michael S. Rolband, PE, PWD, PWS Emeritus /
Director, Department of Environmental Quality ��•
Date: March 29, 2022
Subject: Post -development Stormwater Management at Solar Projects
Dear All:
To date, the Department of Environmental Quality (DEQ) has not required solar projects that are
subject to Virginia Stormwater Management Program (VSMP) requirements to account for the
imperviousness of the solar panels when applying the Commonwealth's post -development
stormwater management technical criteria. When performing water quantity (rainfall -runoff)
calculations, DEQ's practice has been to consider only the solar panel support posts and beams
as impervious areas. However, this approach has the potential to underestimate the post -
development runoff volume or runoff rate from solar panel arrays, which in turn has the potential
to negatively impact downstream waterways or properties. Additionally, the Environmental
Protection Agency's (EPA) Chesapeake Bay Program considers the solar panels to be
impervious areas for the purposes of performing water quality modeling/calculations for the
Chesapeake Bay Total Maximum Daily Load.
To safeguard the protection of downstream waterways and properties as well as ensure
consistency with EPA's Chesapeake Bay Program, DEQ will be implementing a stronger post -
development stormwater management policy for solar projects that are subject to VSMP
requirements. The new policy will go into effect immediately (i.e., the policy applies to all
stormwater management plans not approved prior to the date of this memorandum regardless of
the stage of design), and is as follows:
March 29, 2022
SWM at Solar Projects
Page 2 of 2
Water Quantity. Solar panels are to be considered unconnected impervious areas when
performing post -development water quantity calculations using the hydrologic methods
specified in the Virginia Stormwater Management Program Regulation, 9VAC25-870-72.
Current information regarding the application of unconnected impervious areas can be
found in Chapter 9 (Hydrologic Soil -Cover Complexes), Part 630 (Hydrology) of the
Natural Resource Conservation Service's National Engineering Handbook.
2. Water Quality. Solar panels are to be considered impervious areas when performing
post -development water quality calculations using the Virginia Runoff Reduction Method
(VRRM). To account for the disconnection of the solar panels from the overall drainage
system, the area of the solar panels may be entered into the applicable "Simple
Disconnection" stormwater best management practices section of the VRRM compliance
spreadsheet (i.e., 2a — Simple Disconnection to A/B Soils or 2b — Simple Disconnection
to C/D Soils).
Alternative Methods. This policy does not prohibit any alternative method. If
alternative proposals are made, such proposals will be reviewed and accepted or denied
based on their technical adequacy and compliance with the appropriate laws and
regulations.
DEQ staff are currently preparing an agency guidance document to provide additional clarity on
the implementation of this memorandum. Until the guidance document is finalized, please feel
free to contact Drew Hammond (Andrew.Hammond(a,deq.virginia.gov or 804-698-4101) or Erin
Belt (Erin. Beltkdeq.virginia.gov or 757-374-4621) should you have any questions.