8 comments
The Virginia Association of Soil & Water Conservation Districts (VASWCD) is pleased to offer comments on DEQ's Guidance Memo No. 22-2012- Stormwater Management and Erosion & Sediment Control Design Guide. The VASWCD is a private nonprofit association of 47 Soil and Water Conservation Districts in Virginia. The VASWCD's voting members are all elected and appointed directors. SWCDs were established in the 1930's as political subdivisions of the state in response to the pressing need for conservation of our natural resources in the Commonwealth. The mission of the VASWCD is to provide and promote leadership in the conservation of natural resources through stewardship and education programs.
Specifically, with respect to Chapter 5.500 of the document, VASWCD recently adopted policy at its annual meeting in December 2022 that speaks to the environmental impact of utility scale solar development in the Commonwealth. The policy calls on the General Assembly to amend the Virginia Clean Economy Act (VCEA) to remove any incentives to convert forest and prime agricultural lands into solar industrial facilities, but instead provides incentives for such solar facilities to be developed on brownfields and on existing residential and commercial structures, where they can contribute to greenhouse gas emission reduction without impairing environmental quality in the Commonwealth.
Consistent with that policy, we urge DEQ in the Guidance Memo to:
I continue to have concerns about the application of channel protection criteria per 9VAC25-870-66.B.3 in conjunction with the karst loss modification values, specifically if discharging to a karst feature.
There are significant problems with applying channel and flood protection independently to each karst feature per 3.306.A.
General best practice dictates that the existing hydrologic flow regime to a karst feature should maintained to the extent possible. The application of energy balance does not result in an allowable post-development discharge regime that is similar to the pre-developed flow.
Even in a case where no impervious area is added to a drainage area to a sinkhole, the application of the karst loss adjustment factor, and then energy balance results in a lower peak discharge to the karst feature due to the improvement factor alone.
For example, if:
Pre -dev peak discharge = 0.25 cfs
Pre-dev runoff volume = 500 cf
In this case, we will say the area is not developed, and so pre- and post- numbers are the same.
Apply KAF – presumably the whole drainage area to the karst feature is “in karst”, so the KAF is 0.33.
0.25 cfs x 0.33 = 0.0825 cfs
New Pre-dev peak discharge is 0.0825 cfs.
The table indicates that the KAF is applied to peak flow rate (does not mention volume, which seems like another issue altogether when applying KAF to energy balance methodology), so presumably the energy balance equation now looks like this:
Q-1 allowable = 0.8 (0.0825 x 500) / 500
Q-1 allowable = 0.066
This allowable is 80% of the original peak flow. Or only 26.4% if you look at the unadjusted pre-development peak, which I believe there is a good case for (see further explanation on this point below).
For a scenario where some of the area to the karst feature is developed:
Post- peak discharge = 2.5 cfs
Post- volume runoff volume = 2000 cf
Q-1 allowable = 0.8 (0.0825 x 500)/ 2000
Q-1 allowable = 0.0165
Or only about 20% of the original karst-adjusted peak flow to the feature. This does not result in maintaining the existing hydrologic regime.
Furthermore, if the drainage area discharges to a karst feature, KAF may not even make sense, as the entire amount (100%) of predeveloped surface runoff would make its way into the feature. I believe the KAF is meant to be applied more at a landscape scale, where your surface point of discharge may need to be adjusted due to karst losses across the landscape. In that scenario, the adjusted peak represents the water that does not enter the karst system.
This is different than analyzing a point of discharge directly into a karst feature, where all of the runoff does enter the karst system, and therefore should not require an adjustment. If you look at the allowable from the second scenario compared to the unadjusted pre-development peak, the allowable discharge is only 6.6% of the pre-development peak, and nowhere close to the existing hydrologic regime.
Remaining comments from the earlier version. Comments that have been addressed by revisions have been removed.
Thank you for the opportunity to comment.
These comments are submitted upon behalf of the Chesapeake Solar and Storage Association (CHESSA).
CHESSA is regional professional and trade association whose members are solar energy and energy storage developers of small, medium and large solar and storage projects. Our members engage project engineers, contractors, attorneys, industry experts and other professionals to assist in all stages of permitting, project approvals, environmental and other compliances, including E&S and SWM. In short our members and their engaged professionals have a high level of expertise and public policy related experience to contribute to this discussion.
Our comments will be brief.
First. CHESSA sincerely appreciates DEQ and the Youngkin Administration for considering our comments and perspectives on this important subject, in this Guidance Document and its companion Guidance Document, 22-2011.
Second. CHESSA associates its bigger picture comments with those more detailed comments of ACP, AES and the comments previously made by the project engineers, CHESSA members and other industry experts in the comments that were submitted by August 31, 2022.
Third. CHESSA believes the revised language in Section 5.500 strikes an important balance for solar projects well underway and provides a glide path for a change in the rules going forward.
Fourth. CHESSA still has concerns about Section 3.307 relating to requiring off-site drainage easements and hopes that use of "best practices" may provide mitigation of this requirement. CHESSA believes that one efficient way of complying with this requirement will be to acquire more land than is actually required for the solar project itself, which increases the expense of solar development and also runs counter to the stated goals of HB 206. But, this approach will eliminate or at least mitigate the need to acquire off-site easements. CHESSA appreciates DEQ considering our perspectives on this particular item in development of this Guidance Document.
Fifth. With respect to "best practices", CHESSA would observe that what constitutes a "best practice" evolves with time and the solar industry will always appreciate DEQ considering new development techniques that are more efficient in protection of natural resources to include SWM. DEQ Staff and CHESSA have discussed reduction of high compaction levels as one way of reexamining current best practices.
In closing, CHESSA appreciates the open dialog between DEQ Staff and the solar industry on the SWM discussion and looks forward to our future discussions on all matters of environment protection and regulation affecting solar development.
Respectfully submitted,
CHESSA
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.
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?
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.
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.
AES CE seeks clarification on the specific language of “directly connected” and requests specific examples of this type of direct connection be provided.
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.
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.
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.
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.
Appalachian Power Company (APCo) appreciated the opportunity to provide comments on the Virginia Department of Environmental Quality (DEQ) Guidance Memo No. 22-2011 and Guidance Memo No. 22-2012. As you are aware, the application of traditional design criteria to linear utility projects creates significant challenges due to limited space and lack of ownership in right-of-way (ROW) and access easements. Our comments are presented to help APCo better understand the agency’s desired outcomes associated with the current guidance documents and language included in current regulations. This understanding will allow APCo to guide future internal engineering practices and policy more effectively. APCo respectfully requests that DEQ consider the following comments:
Guidance Memo No. 22-2012
Comment #1: The provided design guidance is understood to have been developed to “assist the public and the development community in determining the policies and procedures” and provide interpretations of how the law and regulations are to be applied to erosion and sediment control and stormwater management plan design and development. However, some items may require a more formal evaluation with stakeholders before rollout to determine potential consequences of the guidance provided, and to determine if they constitute a change in regulations. Several examples that will have significant impacts on development include: requiring converted sheet flow to comply with channel/flood protection criteria, the new maximum sheet flow lengths, requiring drainage easements below sheet flow areas, etc. DEQ should consider developing a committee of stakeholders and professionals to help better define regulatory requirements around sheet flow and include input from the linear development and annual standards and specifications communities which administer non-traditional projects.
Comment #2: Clarify how the following statement in the guidance document will be considered for Annual Standards and Specifications holders, and provide procedures for review and approval where a licensed professional in the Commonwealth of Virginia is proposing designs which are not prohibited by law or regulation but may conflict with the guidance document(s):
“This document is provided as guidance and, as such, sets forth standard operating procedures for the agency. However, it does not mandate or prohibit any particular action not otherwise required or prohibited by law or regulation. If alternative proposals are made, such proposals will be reviewed and accepted or denied based on their technical adequacy and compliance with appropriate laws and regulations.”
Comment #3: The regulations and this document discuss two types of flow: Concentrated Flow (within the Channel & Flood Protection sections) and Sheet Flow. However, there is another type of flow utilized in time of concentration modeling that is not discussed: Shallow Concentrated Flow. Although the term includes the word concentrated, it cannot be analyzed in the same way that channel or pipe flow can analyzed be due to the lack of a defined cross-section and is not considered a point source discharge associated with construction activities. AEP considers this type of flow to fall under sheet flow characteristics and requests DEQ to include those flow lengths and depths when talking about design or restoration of sheet flow on construction sites. Our concern is that the requirement as proposed in GM 22-2012 may have unintended consequences and be counterproductive to protecting water quality. For example, NRCS equation 15-9 would dictate point source discharge classifications so engineers will be forced to design conveyance systems which would break up the natural flow patterns and potentially divert water from natural resources such as wetlands, purely based on a formula for time of concentration. NRCS equation 15-9 is not provided in the national hydraulic handbook to classify flow but to calculate timing of flow as it is under the title “630.1502 Methods for estimating time of concentration”.
Comment #4 (Section 2.303.1 - C.1.d): This section suggests evaluation of the 2-year 24-hour storm event for both capacity and velocity within the natural channel while also referencing 9VAC25-870-66 which requires a 1-year energy balance analysis and 10-year flood protection analysis for capacity. Please clarify if a temporary sediment basin discharging to a natural channel requires analysis of energy balance and flood protection calculations required in 9VAC25-870-66 in addition to a 2-year capacity and erosion evaluation.
Comment #5 (Section 3.302.1 - C.3.d): This section provides a table for permissible velocities but does not provide the required storm for analysis. Please clarify which design storm event is expected to be used for channel protection permissible velocity calculations.
Comment #6 (Section 3.305.1 - B.1): This section states “The 10-year 24-hour post-developed sheetflow velocity should be less than or equal to the following table”. Please confirm the design storm event to be used in permissible velocity calculations. In the regulations, velocity calculations are based on the 1- or 2-year storm event while flooding is based on the 10-year storm event. See Comment #3 above regarding sheet flow.
Comment #7 (Section 3.305.1 - B.2 & B.3): Section 3.305.1.B.2 states that the sheet flow depth should be less than or equal to 0.1 ft for the entire length of the flow path to the downgradient stormwater conveyance system and Section 3.305.1.B.3 provides guidance that the length of sheet flow shall be equal to or less than NRCS NEH Equation 15-9. These two sections seem to indicate that despite existing surveyed contours showing parallel contours that would induce flow across a planar surface (i.e. sheetflow), a distance alone (as determined by Equation 15-9, which is based primarily on flow depths) would define a concentration point. Equation 15-9 is under the title “630.1502 Methods for estimating time of concentration” and the NRCS NEH does not indicate that it calculates a maximum slope length at which sheetflow conditions will exist. Additionally, if a site is not within that distance to an existing stormwater conveyance system, the engineer will be required to concentrate flows and direct them into a BMP or manmade conveyance system which could dramatically change the post-development drainage areas within a watershed, potentially bypassing existing natural resources/wetlands. Please clarify if it is DEQ’s intention to channelize flow and require energy balance for all areas of parallel contours longer than Equation 15-9 slope length. If so, this requirement may contradict Section 5.200B which states that post developed drainage areas should not deviate pre to post by approximately 10% or more, as the more channelized flow present onsite, the higher likelihood of changing pre and post development drainage areas greater than 10%. This is an important issue for our projects in southwestern Virginia along ridges and hillsides. See Comment #3 regarding shallow concentrated flow regimes.
Comment #8 (Section 3.305.2 - C.9): This section indicates that additional analysis is required downgradient of level spreaders. The level spreader design detail was created by DEQ with the intent that the design community would use a standardized approach to converting concentrated flow to sheetflow. If a DEQ approved detail for level spreader is not sufficient to demonstrate design adequacy, DEQ should provide the design community with examples as to how this calculation should be performed.
Comment #9 (Section: 3.307 Drainage Easements Obtainment): The Virginia Stormwater Management laws and regulations are written such that compliance with the laws and regulations must be met at the LOD of the project. Accordingly, it is unclear why this section requires easements to be obtained within downgradient properties when regulatory compliance is met at the LOD, especially for runoff released as sheetflow or as concentrated flow into existing drainage features or flow paths. We request DEQ include an explanation why such easements are statutorily required when any future downgradient development will require stormwater plans and calculations that take into account the developed watershed conditions and must demonstrate compliance with the appropriate laws and regulations to obtain the permits required for construction. This requirement for the acquisition and recordation of easements is especially onerous for linear projects with long, narrow limits of disturbance.
Comment #10 (Guidance Criteria: 4.302.D): This section states that linear utility projects that “will not result in changes to the pre-development runoff characteristics of the land” may be eligible for a permit or stormwater management plan waiver per DEQ guidance Memo No 15-2003. This statement is not consistent with GM 15-2003 text which includes scenarios where there are changes to the landcover and pre-development runoff characteristics, but the DEQ or VSMP authority determines the changes are not “significant”. We request this guidance memo include an explanation or calculations to show how significance is determined by the DEQ and request a TAC be formed to update GM 15-2003 to include more types of linear projects such as our electrical utility lines where, as DEQ states, “the application of the postdevelopment water quantity and water quality controls to these types of projects and the preparation and implementation of a stormwater management plan may provide minimum water quality benefit”. With regards to GM 15-2003 and land disturbance over an acre with no permit required by DEQ we request clarification that the applicability of the VSMP Regulations (9VAC25-870) for these projects is based on the definition a “land-disturbing activity,” which is “a manmade change to the land surface that potentially changes its runoff characteristics…” If there are no changes in pre-development runoff characteristics as stated in this section and proposed by GM 15-2003, the VSMP Regulations should not be applicable and would not even require an application or waiver from the DEQ.
Comment #11 (Guidance Criteria: 5.302.D): APCo agrees with DEQ that changes to the soil profile occur during construction that may not be known by the design professional, but the requirements added by DEQ here do not seem to follow any current regulations and the code referenced is for design storms and not soils or curve numbers. DEQ should reference where the new interpretation builds on current scientific research and current DEQ permit or regulatory requirements under the runoff reduction method. Per 630.0702 of the National Engineering Handbook one cannot accurately describe the hydrologic properties of the disturbed soil without an onsite investigation, which could alter the designed BMPs. Any decision to change the pre-construction HSG values for post-construction conditions should be left to the design professional sealing the plan set.
We greatly appreciate the opportunity for this review of the revised document and believe that additional changes will benefit the regulated community and DEQ in implementing the stormwater program.
Stantec sincerely appreciates the opportunity to review the draft guidance document, and we remain supportive of Department’s effort of providing a comprehensive reference. Based on review of the latest release; however, it appears that limited changes have been made to Draft Guidance Memo No. 22-2012. Stantec staff have noted several questions and concerns that remain with the guidance as proposed.
Many of the subjects, while understandable and of legitimate concern, could be dealt with in a more context-specific manner, targeting the desired environmental outcomes and/or agency concerns. While not comprehensive, an itemization of specific comments is included under Attachment A for consideration. We look forward to continued discussion and working together with DEQ, and fruitful dialogue under eventual guidance implementation.
Attachment A - Comments on Guidance Memo No. 22-2012 - Stormwater Management and Erosion & Sediment Control Design Guide
| Comment # | Guidance Section | Comment |
| 1 | Summary | It is unclear from the summary if the guidance is intended to be applied to Annual Standards and Specifications holders and projects. |
| 2 | 2.200 | There is quite a bit of uncertainty surrounding the language. The guidance states that, “Nothing contained herein shall be deemed to waive or modify other requirements of existing law or regulations,” but the language and tone of the guidance document would seem to be inconsistent with this statement. In one instance the document indicates this is “preferred guidelines” for ensuring compliance, other sections indicate land development “is subject to” the guidance, yet other areas of the document indicate that the Authority “may allow for variations” to the guidelines or may allow for “exceptions” to the guidelines, and yet other sections refer to this as the “minimum acceptable”. Given that the guidance extrapolates quite significantly from standard engineering practice for stormwater over the past 8 years, modifies the current technical guidance, and infers several requirements which are not stated in the guidance, the language above does not jibe with the disclaimer language that indicates that alternative proposals are to be reviewed or denied based on technical adequacy and compliance with the regulations, and that this does not mandate or prohibit any action not already mandated or prohibited by the law and regulations. It is very clear that projects will be reviewed for strict adherence to this guidance, and that administrative action is required to vary from it or to take exception to it. |
| 3 | 2.303.D.2 | This criteria applies post-construction stormwater quantity criteria to temporary construction sediment basin releases. Post-construction regulations specifically indicate that post-development numbers are based on ultimate build-out, not temporary conditions. |
| 4 | 3.302.1.C.3* | Asterisk – It appears advisable to perform case studies / scenarios to confirm this criteria doesn't unduly, or double, penalize highly erodible soils. It would seem that highly erodible is largely related to slope, and slope is already accounted for in the permissible velocities cited above. |
| 5 | 3.302.4 | This section is inconsistent with the definitions above. The flood-prone area is the area outside of the main channel This obviates the entire purpose for creating definitions of conveyance systems (instead of just channels). This section effectively requires definition of the floodprone area with a storm that likely never leaves the main channel (the 1-yr). Additionally, as written it would appear that all outfalls would need to be reviewed and approved by DEQ, regardless of the applicability of GM22-2011 (streamlined review). Further, this section could encourage additional impacts to wetland fringe areas adjacent to the main channels, which would may result in an adverse environmental impact. |
| 6 | 3.303 | Localized flooding is only defined as flood conditions which are likely to cause property damage or unsafe conditions. The reason for the definitions of the conveyance systems themselves were to be permissive of small amounts of additional flooding where it was not injurious to property. |
| 7 | 3.303.D | This doesn't appear to be sound universal criteria. There are many new culverts with design HW elevations higher than the channel during a 10-year event. |
| 8 | 5.302.D | We recommend adding language clarifying that the use of DEQ Stormwater Design Specification No. 4 (Soil Compost Amendment) should only be necessary as part of the water quality compliance approach (crediting BMP). Applicants should have other acceptable means of returning disturbed areas to a hydrologically functional condition outside of strict adherence to Specification No. 4. Further, "full implementation" of Specification No. 4, would require potentially overly burdensome aspects, including maintenance activities, agreements, easements, etc. |
| 9 | 3.307.D | This effectively invalidates the purpose and viability of the sheet flow requirements that were intentionally embodied in the regulations, and is inconsistent with the goal of maintaining pre-development drainage areas. |
| 10 | 4.400 | Environmental Site Design (ESD) is certainly encouraged; however, there are many instances where the process does not apply and is not required to achieve compliance with current regulations. The section implies that reviewers may request a demonstration of ESD steps that have been taken on a given project, which may lead to additional review iterations and potential for schedule impacts with no tangible environmental benefit in many cases. There were several regulatory meetings and discussions to not mandate ESD like this guidance document effectively implies. The simplicity and elegance of the VRRM/EB is that it rewards ESD and encourages it, without mandating ESD to the maximum extent practicable. |
| 11 | 5.302.D | Without discussing the applicability of this criteria, or providing nuance and context, the proposed requirement is a sweeping change from current practice, deviates from the basis of the regulations, and will potentially result in a greater increase to stormwater facility sizes that the regulations themselves did when adopted. There are certainly instances where massive changes to the soil strata may warrant this consideration; however, that would deviate from longstanding stormwater practices and numerous hydrologic validation studies. The options for dealing with the matter effectively resolve to 1 or 5. Option 2 appears to be excessively costly and Items 3 and 4 area generally impracticable due to the need to revise plans after construction. Item 5 could be expanded upon and could involve deep ripping or tilling, strip, segregate, stockpile and re-application of in-situ topsoil, or other more practical and cost-effective means of dealing with the underlying issue. |
| 12 | 5.302.E | This will have implications on water quality too. Water quantity and water quantity were deliberate equiavalated when the regulations and technical criterion were developed. This will require updates to the VRRM spreadsheets. Further, see our forest/open space comment. |
| 13 | 5.302.E | Forest cover and open space were defined as hydrologically equivalent during the development of the regulations and the methodology and this was deliberate. When the regulations and technical framework (VRRM/Energy Balance methods) were developed, there was a deliberate decision to draw equivalence between forest and unmanaged pervious open space (such as utility easements). The reasons were several, but include, in part: • The near equivalence of forest and open space in terms of curve number. • The added complexity of bifurcating forest and open space, which would affect both quantity and quality computations (both are based on runoff volumes, either on an event basis or annual basis, respectively). • The inability of an easement holder to control the overall drainage patterns and infrastructure on privately-owned property through which a utility traverses. • The impracticality of servicing new or expanded vegetated linear easements with stormwater practices. • Related to the above point, during the development of the regulations, based on discussions with many stakeholders, it was not deemed desirable to the Commonwealth, landowners and utility entities to force structural stormwater facilities treating meadows and woods in a vegetated utility corridor. It is further likely to be very costly and provide no measurable environmental benefit (and expanded land disturbance). Based on the above, when the regulations were adopted, the Commonwealth elected to employ a compliance framework which assured that vegetated open space areas meeting the Forest and Open Space Management conditions be deemed effectively equivalent from a water quality and quantity standpoint. As such, these landuses remain computationally equivalent under current VRRM. These conditions generally set forth that the entity mow or maintain the areas no more than four times per annum, and have a maintenance plan consistent with these criterion. Suggest striking this table, or use the CN values that are consistent with the VRRM categories (three categories, not four). |
| 14 | 5.500 | The language requires “compliance” with a handbook that is not referenced in the regulation. |
| 15 | 7.400 | Why is DEQ requiring as-built drawings for storm sewers and culverts? The regulations require construction record drawings for permanent stormwater management facilities only. Additionally, we suggest avoiding the use of the term (as-built drawing) as it was intentionally avoided during the regulatory process. |
January 18, 2023
Ms. Rebeccah Rochet, P.E.
Manager, Office of Stormwater Management
Virginia Department of Environmental Quality
rebeccah.rochet@deq.virginia.gov
Dear Ms. Rochet,
Thank you for the opportunity to provide feedback on the revised GM22-2012 Stormwater Management and Erosion & Sediment Control Design Guide. Balzer and Associates joined many other engineers, developers, and other stakeholders in providing comments on the initial publication of this document in August 2022. As stated previously, we applaud DEQ’s efforts to consolidate and standardize erosion control and stormwater management design guidance in the Commonwealth to ensure that developers, engineers, and plan reviewers have clear expectations surrounding enforcement of Virginia’s stormwater and environmental regulations. Our clients include Virginians doing business across the state including many rural communities. We continue to serve on DEQ’s Stormwater Management Handbook Stakeholder Advisory Group and be encouraged by the effort to bring a diverse group of stakeholders together to collectively write a handbook that is consistent with the regulations and compatible with development across Virginia.
We understand that DEQ intends for GM22-2012 to be a document to assist in “fast-tracking” review of plans submitted to the agency. However, our clients and our organization remain concerned that the implementation of this document is encumbered by two flaws: (1) it introduces new technical criteria or rules that are above and beyond what is stated in the Virginia regulations and (2) it blurs the line between recommended practices and requirements grounded in law. We have seen that concepts presented in this guidance document, defined as “good engineering practices”, have already been enforced as requirements for plan approval at the regional office level. The impact that the application of this guidance document will have on Virginia’s economy commands more study than a 30 day public comment period.
Based on our review of the revised guidance memo, we offer the following specific comments. References are made to DEQ’s response to comments on the initial posting of GM22-2012, as made available on DEQ’s website.
|
Section |
Comment |
|
2.303 (D) |
Repeat Comment: This section should include meeting the channel and flood protection requirements of 9VAC25-870-66 or meeting the Safe Harbor provisions as options for compliance for sediment basin discharges in lieu of analysis of the downstream channel to the limit of analysis. This is stated in Minimum Standard 19(n) (9VAC25-840-40).
Follow-up: This was added under item d. (natural conveyance systems), but the applicable compliance methods above would apply to manmade or restored conveyance systems as well. This should be a separate item, not contained within item d. |
|
3.302.3 |
Repeat Comment: The Guidance Document should clarify (as is done in Section 3.302.1(A)(1)) that the energy balance requirement applies only if a natural conveyance system is reached before the limits of analysis. As an example, this is clearly explained in Section 11.5.2.1.7 of the VDOT Drainage Manual: “The point where the limit of analysis occurs does not need to be included in the evaluation of adequacy, but the system from the outfall or point of discharge up to (but not including) the limits of analysis must be analyzed. If there is a natural channel anywhere in the system from the outfall up to the limit of analysis (but not including the point defining the limit of analysis), then the energy balance will apply.”
The suggested text keeps in line with the long-standing Virginia Statewide Stormwater Runoff Standard (Virginia Erosion and Sediment Control Handbook, Chapter 4) in which a receiving channel may be assumed adequate if the total drainage area to the point of analysis is 100 times greater than the contributing drainage area of the project site. If the channel is adequate, there remains no reason or benefit to apply the energy balance reduction. This section may also be improved by creating a list of specifically excluded water bodies, such as tidal waters, and rivers such as the James, the New, the Dan, the, Roanoke, and the Rappahannock. However, at some point, the exclusion must still come back to a limit based on a comparison of the site area to the watershed area (considering the headwaters of these rivers) – in lieu of regulatory changes, this must be 100 times the site area, unless a locality has adopted more stringent technical criteria.
Follow-up: DEQ’s response did not address this change in technical criteria and long-standing state stormwater standard that conveyances receiving greater than 100 times the site area may be assumed adequate and excluded from contributing to the technical requirements that the site is subject to (i.e. energy balance). The application of 9VAC25-870-66(B)(3) in the above described scenario violates and represents more stringent technical criteria than the limits of analysis per 9VAC25-870-66(B)(4). |
|
3.302.3 |
Repeat comment: “A manmade lake or reservoir not created for the purpose of managing post-development stormwater should be considered a natural stormwater conveyance system.”
This modifies the definition of a natural conveyance system (as defined in 9VAC25-870-10) and adds an unnecessary and wasteful burden on development, particularly when the receiving waterbody has a watershed greater than 100 times the site area and is controlled by a release structure. A suggested improvement would be to either clarify the applicability based on the 1% limits of analysis as described above in VDOT’s Drainage Manual and/or create a list of specifically excluded controlled water bodies such as Kerr Lake, Smith Mountain Lake, Lake Gaston, Lake Anna, Claytor Lake, etc.
Follow-up: DEQ’s response states that the definition of a natural conveyance channel is not modified with this guidance, however, the guidance definitively subjects additional systems (manmade lakes and reservoirs) to the more restrictive detention requirements of 9VAC25-870-66(B)(3). Manmade lakes and reservoirs cannot reasonably be discerned as an intended subset of the definition of a “natural stormwater conveyance” in the current regulations and thus this represents new technical criteria and burden on development. |
|
3.302.4 |
Repeat comment: The 1-year storm is not a channel forming or flooding event in natural channel design parameters. A more appropriate flood event to analyze and determine the flood-prone area would be the 2- or 10-year storm event.
Follow-up: No change was made to this section of the document and no justification for the use of the 1-year storm event for channel forming or flooding analysis was provided. |
|
3.305.1 3.305.2 |
Repeat comment: All references in these sections to 10-yr 24-hour storm velocity are inconsistent with the regulations. The VSMP Regulations and all other VA state standards evaluate erosive velocities based on the 2-yr 24-hour storm.
Follow-up: No change was made to this section of the document and no justification for the use of the 10-year storm event for velocity analysis was provided. Use of the 10-year storm to evaluate velocity is a departure from current technical criteria. |
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3.305.2 |
Repeat comment: “The length of sheet flow path to the down-gradient stormwater conveyance system should be less than or equal to the following…” This requirement is not stated in the regulations and ignores the condition where the pre-development downstream flow path may be shallow concentrated flow.
Instead of tying the issue of post-development stormwater discharges to NEH Part 60 Chapter 15 which speaks in terms of Time of Concentration, this section should focus on whether the discharge mimics the pre-development rate and volume in line with Va. Code § 62.1-44.15:28 A 10. For example, the pre-development runoff may be shallow concentrated flow across a rolling farmland or karst swale; or, a sheet flow discharge to a wetland or RPA may be more beneficial (provide greater infiltration) when located more than 100 feet from the main channel. |
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3.307 |
Repeat comment: All discharges that are made in accordance with the Virginia Stormwater Management Act and/or VSMP Regulations and do not require/propose construction, improvement, or modification of downstream flowpaths should not be subject to obtaining easements or agreements from downstream property owners. This section should specifically exclude discharges to an existing stormwater conveyance system that is not being modified. |
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Chapter 5
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Repeat comment: This section of good engineering practices should be more specifically defined in section 5.100 as suggestions and not requirements. Good engineering practices relies on the judgement of engineers through the design practice and do not always include the steps or processes described in this section. This chapter should be emphasized as suggestions for the engineering community and not requirements for DEQ or local authorities to adhere to in their reviews |
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5.200 (A) and (B) |
Repeat comment: “Post-development drainage areas and drainage divides should replicate, as nearly as practicable, the pre-development drainage areas and drainage divides. See Va. Code § 62.1-44.15:28 A 10.” This statement misrepresents Va. Code § 62.1-44.15:28 A 10. It replaces the parameters of rate of flow, runoff characteristics, and site hydrology with “drainage areas and drainage divides” and ignores the provision that the law provides for improvement of existing erosion and flooding conditions. It should be noted that the existing channel and flood protection requirements already address Va. Code § 62.1-44.15:28 A 10, including the change in runoff volume incurred by changes in drainage divides.
“Post-development drainage areas should deviate from the pre-development condition by no more than plus or minus 10%.
Because after-development runoff can be exponentially changed whether drainage areas/divides are modified or exactly the same, a 10% change in area is substantively irrelevant to the intent of the Virginia Stormwater Management Act and VSMP Regulations or the effects of stormwater runoff on the Commonwealth. Varying pre-development conditions including topography, site size, and geographic location, urban versus rural settings, and linear development projects make application of this new criteria highly impractical.
A better application of this concept would be to use a ±10%-20% change in area to trigger an evaluation of the impacts by way of the adopted technical criteria:
Follow-up: As discussed above, a stipulation on maximum change in drainage areas is not a valid association to the statutory authority referenced in Va. Code § 62.1-44.15:28 A 10. DEQ’s response did not address the disassociation between drainage areas and other factors that influence site hydrology. Additionally, DEQ’s response did not validate or justify the selection of 10% as this new technical criteria. Stakeholders object to the implementation of this requirement without further study. While DEQ Staff has made attempts to assure that such “good engineering practices” would be implemented as “guidance and guidelines to fast-track review”, the reality is DEQ Regional Offices have already begun enforcing this as a requirement for plan approval, not an option or suggestion.
Further discussions with industry professionals, including VSMP authorities, and DEQ’s response and modification to this section continue to shed light on the short-sighted nature of this requirement. No evidence has been provided as to the prevalence or practicality of this concept outside of urban environments. In rural areas, shifts in drainage divides are often done for the purpose of routing stormwater discharges to existing or proposed stormwater conveyance systems where other drainage basins do not have a defined downstream channel. The application of the sheet flow analysis in other parts of this guidance memo further restricts the ability to discharge to basins that do not have defined downstream channels. The updated guidance in 5.200 (B) states that >10% deviations may be permitted where post-development volumes do not exceed pre-development volumes but that caveat in itself is often highly impractical in new development sites where impervious covers are increased. |
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5.301(D) 5.302(D) |
Repeat comment: “The hydrologic soil group (HSG) used for post-development CN selection should be based on the ultimate development condition of the subject land-disturbing activity…For disturbed soils (e.g., pre-development soil profiles that will be mixed or removed or fill material from other areas will be introduced), the design professional should:
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 Agency guidance (Virginia Runoff Reduction Method, GM 16-2001). 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.
Modification of the pre- to post- HSG is not possible with the Agency provided 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.
A suggested modification to these sections would be to provide further clarification limiting the applicability of HSG adjustment. For example, limiting pre- and post- development adjustment to situations where pre-construction infiltration testing was performed.
An alternate suggestion would be clarification that implementation of an adjustment is optional at the discretion of the design professional (as long as if the adjustment is applied it is applied based on consistent criteria from pre- to post- development). Hydrologic soil grouping, like all stormwater computations, is based on a set of assumptions including but not limited to large scale soil mapping from USDA; there must be understanding regarding the level of accuracy relative to the engineering factor of safety present in stormwater design.
Follow-up: DEQ’s response states that “it is common that site developments adjust the post-development HSG classification as a result of construction activities”. The prevalence of negative feedback provided as part of the public comment period during the initial publication of GM22-2012 regarding this section in particular would suggest that this is not standard practice across the Commonwealth. Additionally, no explanation was provided in DEQ’s response as to the clear incompatibility of this guidance with the VRRM worksheets. |
Because the comments noted above involve clear changes to existing technical criteria and rules (as defined in the Administrative Process Act), we again urge DEQ to defer implementation of this document for at least 30 days and provide justification that such changes, if they remain, are appropriate for inclusion in a guidance document. We would also like to again request that stakeholder engagement be considered to refine this document prior to re-publication.
Thank you again for your time in consideration of our concerns and we look forward to continued discussion regarding these matters.
Sincerely,
BALZER AND ASSOCIATES, INC.
James R. Taylor, PE
Engineering Department Manager
Christiansburg, VA