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.