Virginia Regulatory Town Hall View Comments

Department of Environmental Quality

State Water Control Board

Guidance Document Change: The Virginia Stormwater Management Handbook, Version 1.0 (Handbook) provides guidance to implement water quantity and water quality criteria in the Virginia Erosion and Stormwater Management Regulation, 9VAC25-875, effective July 1, 2024. The Handbook replaces nine guidance documents, listed below, that the Department of Environmental Quality (DEQ) plans to rescind effective July 1, 2025: 1. Virginia Erosion and Sediment Control Handbook, Third Edition, 1992 2. Virginia Stormwater Management Handbook, First Edition, 1999 3. Guidance Document on VSMP Site Inspection Strategies 4. Guidance Document on Utilization of Nonpoint Nutrient Offsets 5. Guidance Memo No. 14-2002 Implementation Guidance for the 2009 General Permit for Discharges of Stormwater from Construction Activities, 9VAC25-880 6. Guidance Memo No. 14-2014 Implementation Guidance for Section 47 (time limits on applicability of approved design criteria) and Section 48 (grandfathering) 7. Guidance Memo No. 15-2003 Postdevelopment SW Mgmt Implementation Guidance for Linear Utility Projects 8. Guidance Memo No. 22-2011 Streamlined Plan Review for Construction Stormwater Plans and Erosion and Sediment Control Plans submitted by a Licensed Design Professional and reviewed by a Dual Combined Administrator for Erosion and Sediment Control and Stormwater Management 9. Guidance Memo No. 22-2012 Stormwater Management and Erosion & Sediment Control Design Guide The reason that the guidance documents will be rescinded effective July 1, 2025, through a separate Town Hall notice, is that they have been incorporated into the Handbook to reduce complexity and improve the ease of use. A one-year transition period allows plans and permit applications submitted between July 1, 2024 and June 30, 2025 to utilize either the existing manuals, handbooks and guidance or the Virginia Stormwater Management Handbook, Version 1.0. The Handbook is available as a Portable Document Format (pdf) file and online at https://online.encodeplus.com/regs/deq-va/index.aspx. Due to the large file size and number of pages in the Handbook, DEQ recommends using the web-based version to review it and submit comments. Chapters, best management practice specifications, and other information from the Handbook may be downloaded from the website as pdf files. Written comments on the Handbook may be submitted directly through the enCodePlus website that is hosting the handbook, as well as through the Town Hall website, and by email to the contact address provided with this notice. Instructions for submitting comments through the host website are available from the “Comment” link on the webpage banner. DEQ will use comments received during this forum and after the Handbook becomes effective to maintain its content consistent with the process for updates and revisions described in Chapter 1: Introduction. DEQ formed a Stakeholders Advisory Group (SAG) to help develop the Handbook and its content. The SAG met 12 times between July 2022 and October 2023. Members of the SAG were provided an opportunity review and provide feedback on a draft version of the Handbook during November 2023. DEQ reviewed and revised the draft Handbook based on the feedback SAG members provided. Handbook Version 1.0 reflects those revisions. Two Excel spreadsheets with comments SAG members submitted on the draft version of the Handbook, and responses to those comments, are available from the DEQ website at: https://www.deq.virginia.gov/our-programs/water/stormwater/stormwater-construction/handbooks under the Virginia Stormwater Management Handbook, Version 1.0 banner.

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3/21/24 2:29 pm

Commenter: Megan, Kirk Engineering

A.3.7.2 Post-development CN Selection REPEAT Comment

Please source where in NEH or other non-VA DEQ standard engineering hydrologic
documents that require to adjust the HSG by atleast 1 factor when disturbing soils or
working with disturbed soils as described in GM 22-2012 Section 5.302 AND this new SWHB in section A.3.7.2. THIS COMMENT WAS MADE during comment period for GM 22-2012 and it was not addressed properly then and is now carried over into this SWM HB with little back up.

It is not found in the state regulations. The state regulations specifically state in 9VAC25-870-66.E "all pervious lands on the site shall be assumed to be in good hydrologic conditions in accordance with the US Dept of Ag NRCS standards, regardless of conditions existing at the time of computations." In otherwords, despite how disturbed the conditions are, it does not give leeway for predevelopment to downgrade the runoff CN to poor. Post development may use "poor" pervious conditions due to disturbance if engineer judges so.
NRCS has hydrologic conditions already assigned for poor and good conditions stating that
"Poor=Factors impair infiltration and tend to increase runoff; Good= Factors encourage average and better than average infiltration and tend to decrease runoff"

It seems redundant to re-create NEH guidance and state that if lands are now disturbed (which is equivalent to impairing the infiltration ability of the soil using conditions of Poor) that instead of using historic standard practices (and whats used all over the country), that we should negate NEH and come up with new rules/science for hydrology. This is not common practice anywhere, and is creating a new "regulation" per se that is outside the science that is already approved by the State Regulations. If new regs/rules outside of the State Regulations are being created please provide the actual science/studies that supports this hydrologic adjustment (similarly to how NEH has done) for public commenting prior to putting this in an adopted manual for local regulatory agency to follow. This method needs further discussion and commenting before adopting.

9VAC25-870-72.C also specifically states "NRCS OR other standard hydrologic & hydraulic
methods shall be used..." This curve number adjustment described is not standard with
NRCS, or Rational Method, or previous VA SWM/ESC Handbooks. It is not standard in other hydrologic methods or engineering practice. As it is not actually standard, VA DEQ guidance to adjust disturbed soils is then going against the State Regulations and created a new requirement/science that is not allowing proper time to discuss/comment before adopting.

Also something to consider-Shouldn't the energy balance equation with the improvement factor already take into consider all these nuance adjustment with post development soils mixing? It would make things much simpler then messing/overcomplicating common Hydrologic modeling practices that have been tried and true over the many years.

Same/similar comment was written during SAG comment period by James Taylor with Balzer & Associates stating:

"Modification of the pre- to post- HSG is not possible with the VRRM spreadsheets. If you do not provide matching soil area totals, the VRRM worksheet returns an error and does not compute.

Full implementation of DEQ Spec. No. 4 (Soil Compost Amendment) per the specifications is not practical in western parts of the state due to the slope limitations in the specification.

While the science behind the concept is acknowleged, a requirement to adjust the post-developed CN for disturbed soils is not stated in the VSMP Regulations, current and previous Virginia Stormwater Handbooks, or previous DEQ guidance (Virginia Runoff Reduction Method, GM 16-2001). Nor is modifying the HSG from pre-to post-development a common practice across the state currently.

Universal application of an adjustment for any disturbed soil would translate to a substantial additional burden on land development, particularly in rural areas where pre-development lands are undisturbed. This is new content/rules from previous Virginia regulations/guidance and we request that this topic be discussed further including a formal reponse from DEQ if not accepted."

DEQ SAG response said "The review team appreciates the suggested revision. However, proposed revision is too extensive to incorporate at this stage of review. We look forward to addressing this issue in the next update."

If the review team finds it too extensive to properly incorporate and address this issue, then it should NOT be put in the SWM HB at all, and should be removed until it is fully able to be resolved. It was rushed through in the GM-22-2012 guidance and it is being rushed again now.

CommentID: 222332