January 18, 2023

From:  AES Clean Energy

To:       Virginia Department of Environmental Quality

RE:      AES Clean Energy Response to Guidance Memo No. 22-2012

AES CE appreciates the opportunity to comment on GM No. 22-2012. We recommend that the guidance memo be updated and reissued for public comment.

1. “[P]reviously DEQ-approved solar project that does not obtain an interconnection approval by …. may submit a revised stormwater management plan to DEQ for a fast-tracked (expedited) review...”

AES CE seeks clarification on the “expedited process” that DEQ is referencing. Is this the current DEQ 45-day expedited review process or is DEQ referencing the proposed streamlined review process per GM22-2011?

2. “Permanent or temporary soil stabilization should be applied within seven (7) days to all denuded areas at final grade. See Minimum Standard #1, 9VAC25-840-40 1…

A permanent vegetative cover should be established on all denuded areas not otherwise permanent stabilized. See Minimum Standard #3, 9VAC25-840-40 3, and Standard and Specification 3.32 (Permanent Seeding).”

A timeline for the application of initial soil stabilization is identified in this section; however, there are no clear timelines for re-stabilization of previously stabilized but not established denuded areas that do not exhibit excessive erosion. AES CE seeks clarification on whether there is a required timeline for previously stabilized yet not established denuded areas or if these areas, although not established, are considered stabilized and no additional stabilizing measures are necessary.

3. “Specifically, the memo states that ground mounted solar panels shall be considered unconnected impervious cover as defined in Chapter 9, Part 630 of the NRCS National Engineering Handbook.”

AES CE seeks clarification on the technical basis (i.e., baseline studies) for considering ground mounted solar panels as “unconnected impervious surface”. AES CE recommends the inclusion of the following language: “Utility-scale solar projects designed and constructed in accordance with the following criteria shall be considered "vegetated open space" for the ground mounted panel area: (1) solar panels are constructed on post and rack systems and elevated above the ground surface; (2) rows are spaced such that the clear open space between the panels is equal to or greater than the horizontal width of the rows; and (3) the ground surface below the panels consists of well-established vegetation. For any traditional impervious areas (roads, inverter and substation pads, etc.), the SWPPP shall address post-construction stormwater management controls for those areas only.”

Additionally, AES CE recommends a formal study be conducted that evaluates ground surfaces during construction, including vegetated and non-vegetated surfaces, with regard to the issue of erosion concerns associated with ground mounted solar panels. Erosion concerns may be associated with vegetation management under the solar arrays during construction, which may become irrelevant once uniform permanent vegetation is established. AES CE recommends conducting additional studies and evaluating these considerations before implementing drastic design alterations and requirements that may not resolve the underlying issue of erosion. AES would welcome a partnership opportunity with DEQ in accomplishing this goal.

4. “Unless directly connected to the stormwater conveyance system, the horizontal projected area of all solar panels should be considered unconnected impervious area when performing runoff computations…”

AES CE seeks clarification on the specific language of “directly connected” and requests specific examples of this type of direct connection be provided.

5. “Should a project owner elect to implement rain-sensing technology such that the solar panels rotate to a vertical position during storm events, the horizontal projected area may be assumed to be zero...”

AES CE requests the DEQ reevaluate the concept of “vertical position” in regard to panels. Single axis trackers, which are used as the tracking system on the majority of utility-scale solar projects, do not have the capability to go to a 90 degree vertical position. It is common for the maximum allowed angle to be approximately up to  60 degrees from horizontal.

Additionally, AES CE recommends encouraging a dynamic tilt method to disperse rainfall over a larger surface area, reducing both the volume of the impact a single area affected. Tracking systems cannot achieve a vertical position, as DEQ has referenced, but can be set to stow at their maximum tilt angle. AES CE requests the ability to further work with the DEQ on determining tracking system angle variability when considering stormwater calculations and best practices during these storm events.

6. Section 6.500 subsection I table (page 59) states “HSG” means Hydrologic Soil Group. See Appendix 6C of 1992 Virginia Erosion & Sediment Control Handbook for groupings.”

AES CE recommends the inclusion of the U.S. Department of Agriculture Natural Resources Conservation Services Web Soils Survey for reference to hydric soil group information to prevent the utilization of outdated data. 

7. The DEQ SWM ESC 24” x 36” Cover Sheet

1. • Section D – “PROPERTY OWNER” information

AES CE recommends reconsidering how this is outlined on the cover sheet as large-scale projects will typically consist of multiple properties and property owners. This information is best provided in a table format for clarity and ease of reference. AES CE recommends adding a note to this cover sheet that states that the format may vary as long as all information is provided.  

2. • Solar Specific Requirements part II. “SOLAR PANEL ARRAY HORIZONTAL PROJECTED AREA”

AES CE requires clarity on what equation is being referenced in this section. The equation components are provided but the equation is not included under this section. AES CE recommends adding the appropriate equation to the cover sheet.