Supplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

1 40 CFR 450.21(a) Erosion and Sediment Controls. Design, install and maintain effective erosion controls and sediment controls to minimize the discharge of pollutants. At a minimum, such controls must be designed, installed and maintained to: (6) Provide and

maintain natural buffers around surface wate rs, direct stormwater to vegetated areas to increase sediment removal and maximize stormwater infiltration, unless infeasible.

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(1) P roviding and maintaining natural buffers arou nd surface waters, and directing stormwater to vegetated areas to increase sediment removal and maximize stormwater infiltration, control

s or minimizes the discharge of stormwater from the site

.

This requirement reduces the discharge of sediment and oth er pollutants from construction activities. As described by Muñoz

- Carpena et al. (Modeling Hydrology and Sediment Transport in vegetative filter strips, Journal of Hydrology , Volume 214 (1999), pg. 111

- 129), vegetative areas, including vegetated filter str ips, remove pollutants through “ filtration, deposition, infiltration, absorption, adsorption, decomposition and volatilization .” This paper further described the mechanisms of pollutant removal as follows:

“ Vegetation at the downstream edge of disturbed a reas may effectively reduce runoff volume and peak velocity primarily because of the filter’s hydraulic roughness, and subsequent augmentation of infiltration. Decreasing flow volume and velocity translates into sediment deposition in the filter as a resul t of a decrease in transport capacity (Wilson, 1967). Barfield et al. (1979) and Dillaha et al., (1986) reported that grass filter strips have high sediment trapping efficiencies as long as the flow is shallow and uniform and the filter is not submerged. As sediment is deposited from runoff in these vegetated zones, sediment

- bound nutrients are also removed (Bolton et al., 1991; Flanagan et al., 1989). For nutrients attached to sediment (i.e. organic phosphorous, ammonium and organic N) the deposition proc ess largely controls the effectiveness of the filter area, whereas infiltration is the controlling factor for soluble nutrients (such as nitrates and inorganic orthophosphates).”

Therefore, buffers and vegetated areas provide removal of sediment and other pollutants through filtration and other mechanisms. In addition, infiltrating stormwater reduces the amount of water being discharged

, thereby potentially reducing the amount of erosion the discharge will produce. Directing stormwater to vegetated areas t o allow for filtration and infiltration can be a highly effective means of managing stormwater on construction sites because this will reduce the amount of pollutants contained in the discharge through filtration and other removal mechanisms, and infiltrat ion will reduce the volume of the discharge and the associated dissolved pollutants in the infiltrated volume. This can be accomplished in a number of ways. Examples include directing sheet flow leaving si lt fences, filter berms or other perimeter controls to vegetated buffers adjacent to streams. EPA notes that this is common practice on many linear projects where dispersion of stormwater to adjacent vegetated areas can be preferred over designing and constructing conveyances. Other examples include direct ing stormwater exiting sediment basins to vegetated areas such as vegetated buffers adjacent to streams or other vegetated areas on or adjacent to the site through the use of corrugated pipes and level spreaders. EPA notes that this technique is highly app ropriate on sites incorporating low

- impact development and environmental site design, since sites constructed using these principles will typically have areas of vegetation preservation that may be appropriate for dispersion of treated stormwater during th e construction phase. However, permittees need to consider the total volume of stormwater and the amount of sediment in the stormwater when selecting appropriateSupplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

2 mechanisms and locations for dispersion, filtration and infiltration in vegetated areas. Using these techniques is not a substitute for up

- slope erosion and sediment controls. In addition, concentrated points of discharge, such as discharge from sediment basins, should incorporate appropriate energy dissipation devices if necessary to prevent erosi on when directing these flows to vegetated areas. These techniques will help to prevent the formation of gulleys and

associated erosion.

(2) What EPA does not mean by this requirement

.

This requirement only applies during the active phase of construction. This requirement does not mandate providing or maintenance of the buffer in the post

- developed condition. This requirement is also not intended for the operator to have to create vegetated buffers in areas that would not be appropriate for ve getative buffers (e.g., in areas where the existing , natural area adjacent to a stream is not comprised of vegetation but rather consists of rocks, gravel, sand, cobble, etc.). In these cases, the existing, natural area could be considered the appropriate buffer and preservation of that area in its natural state could constitute compliance with this requirement , as any setback between the areas of disturbance and the surface water will provide some attenuation of pollutants and stormwater flows

.

( 3 ) In its comments on the proposed C&D ELG/NSPS, NAHB expressed support for non

numeric effluent limitations in the form of BMPs like this provision.

In its cover comment letter on the proposed C& D ELG/NSPS, NAHB stated that it “has consistently advocated for an ELG that allows for site

- specific selection of BMPs, appropriate sediment basin sizing criteria and the implementation of pollution prevention practices.” NAHB

comment cover letter at 2. NAHB stated that EPA’s proposed Option 1, a BMP

- only ELG, “would build upon the significant environmental progress made to date by ensuring that all construction sites meet a minimum standard of excellence by adopting those erosion and

sediment controls th at have evolved and are now accepted across the country.” Id. NAHB urged EPA to broaden “best management practices and pollution prevention to ensure these practices can be implemented at every permitted construction site, in all circumstances across

the country.” Id. at 3.

In its detailed comments attached to its cover letter, NAHB continued to support a BMP

- only ELG to control stormwater discharges from active construction sites. NAHB urged EPA “to remove any requirements to meet numeric effluent limits and proceed with a BMP

- based ELG to control stormwater discharge.” NAHB detailed comments at 38. NAHB claimed that “[i]n the case of EPA's proposed C&D ELGs, the combination of ELG precedent and the fact that EPA is focusing exclusively on stormwa ter provides irrefutable support for a BMP

- based ELG approach.” Id. at 42. NAHB concluded that “[t] here is substantial authority for and evidence regarding the success associated with permitting authorities relying on BMP

- based approaches

to achieve envi

ronmental objectives. EPA also should rely on a BMP

- based approach for the C&D ELG rulemaking.” Id. at 46 (emphasis in original).

In addition, in its redline/strikeout “precisely crafted edits” of EPA’s proposed Option 1, the BMP

only ELG, NAHB suggeste d a revision to proposed 450.21(a)(7) to make that provision read as follows: “Provide and preserve natural buffers around surface waters.” EPA had proposed “Provide and maintain natural buffers around surface waters.” Thus, while NAHB suggested changin g “maintain” to “preserve”, it did not suggest deleting the requirement, thereby acknowledging, consistent with its overall comments in support of a BMP

- only ELG, that providing and, at a minimum, preserving natural buffers around surface waters is key toSupplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

3 controlling and minimizing the discharge of stormwater from active construction sites. See reference to “precisely crafted edits” on page 144 of NAHB’s detailed comments on the proposed ELG/NSPS, as well as the attachment to EPA

- HQ

- OW

- 2008

- 0465

- 1360. See also NAHB’s reasoning for changing “maintain” to “preserve” on page 147 of its detailed comment

letter.

( 4 ) Implementation of this provision in NPDES permits.

The construction stormwater ELG will be implemented in NPDES permits as the applicable

techno logy

- based effluent limitations in those NPDES permits. The ELG is not directly applicable to any regulated entity. If the permitting authority chooses to copy the ELG verbatim into its draft proposed NPDES permit as the technology

- based effluent limitat ion, dischargers will have an opportunity to provide comment on the need for more specificity if they are concerned that the narrative nature of the limit could unfairly subject them to arbitrary enforcement. Furthermore, in the event that the permitting authority does not provide any additional specificity, it is typical in stormwater permits for active construction for the permitting authorities to include a requirement to prepare a storm water pollution prevention plan (SWPPP) in the permit. While the provisions of the SWPPP are not effluent limitations themselves, they indicate how the discharger intends to meet the narrative effluent limitations in the permit. As

such

, SWPPPs can be helpful to the regulated entity in demonstrating how they are meeting

their effluent limitations.

In the 2012 CGP

, EPA has included a provision requiring permittees discharging to a surface water within 50 feet of their site to implement one of three compliance alternatives:

1. Provide and maintain a 50

- foot buffer of undisturbed natural vegetation; or

2. Provide and maintain an undisturbed naturally vegetated buffer that is less than 50 feet and is supplemented by additional erosion and sedimen t controls, which in combination achieves the sediment load reduction equivalent to a 50

- foot buffer of undisturbed natural vegetation; or

3. If it is infeasible to provide and maintain an undisturbed naturally vegetated buffer of any size, you must implement erosion and sediment controls that achieve the sediment load reduction equivalent to a 50

- foot buffer of undisturbed natural vegetation.

EPA believes that the compliance alternatives provide permittees with needed flexibility to meet this requirement.

( 5 ) A ppropriate time for implementation of this BMP in the construction process

.

Preservation of buffers adjacent to water bodies should be done at the beginning of construction. The use of temporary exclusion fencing or silt fence s are examples of appropriate means of delineating the buffer boundaries. The use of fencing allows equipment operators and others working on site to clearly see the buffer areas and other areas of no disturbance. As sediment controls (such as basins) are b rought on

- line, provisions for directing treated stormwater to vegetated areas and buffers can be implemented.

( 6 ) Where a buffer boundary start s and end

s.

The final rule does not establish a minimum buffer width. However, in implement ing the buffer requirements in NPDES permits, permitting authorities may establish minimum buffer widths soSupplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

4 that the permit requirements are more transparent, environmentally effective, and enforceable

. EPA does not believe that there is one appropriate minimum buffer width that should apply to all

sites nationwide . EPA believes that the establishment of a minimum buffer width is best determined through consideration of several factors by the permitting authority

. Some of the

factors that a permitting authority may evaluate in developing a minimum buffer width include : How effective are buffers at removing sediment and other pollutants in the area s covered under the permit ?

What size buffers are necessar y to provide high levels of pollutant removal? What types of state and local regulations already affect the buffer area? Is a uniform buffer width requirement appropriate? Permitting authorit ies may consider providing flexibility to any minimum buffer width requirements for sites that may have difficulty implementing a minimum buffer width on their site, and to provide flexibility for situations in which buffer disturbances are necessary.

( 7 ) C ircumstances that make buffer controls “in feasible”

.

EPA does not intend for this requirement to conflict with state water right law, and thus the Agency believes that it would be infeasible to provide and maintain natural buffers around surface waters where doing so would conflict with state wat er right law. In addition, f or some projects that are in close proximity to surface waters (such as streams and lakes), there may not be preexisting buffers between the new construction project and the surface water or the vegetation quality may be poor. In these cases, the permitting authority should exercise discretion in establishing appropriate requirements. For example, the permitting authority may authorize disturbance within the buffer in order to allow removal of existing vegetation and

installatio n of new vegetation. Another example of where this standard may require discretion by the permitting authority is reclamation or stream stabilization/improvement projects. In these cases, disturbance within the buffer may be an integral part of the construction project. EPA does not intend this requirement to limit activities within buffers necessary to complete restoration or stabilization projects, or other projects where removal, replacement or alteration of vegetation is a necessary component of the project.

For certain locations within projects, such as locations where stream crossings or other water

oriented features are constructed, EPA would not expect that buffers would be maintained since

this would be infeasible

. Additionally, EPA recogniz es that it may not be feasible to provide a buffer if space constraints require disturbances within the buffer, or if the nature of the development requires it to occur within the buffer (e.g., a waterfront marina). EPA also notes that it does not expect p ermittees to provide buffers around constructed conveyances on site

, such as channels that are constructed on site to convey stormwater.

EPA also recognizes that certain linear projects may have difficulty in complying with a minimum

fixed buffer width requirement due to space constraints. If you are subject to the requirements

in this Part of the final CGP for “linear construction projects” (see Appendix A of the final CGP), you are not required to comply with this requirement if site constraints ( e.g. , limited right

- of

- way ) prevent you from meeting the requirements of the compliance alternatives in Part 2.1.2.1a, provided that you retain as much natural vegetation as is feasible and/or to the extent feasible provide supplemental erosion and sediment co ntrols in the buffer area. You must also document in your SWPPP your rationale as to why it is infeasible for you to comply with the requirements in Part 2.1.2.1a, and describe any buffer width retained and/or supplemental

erosion and sediment controls in stalled.Supplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

5 EPA notes that individual permitting authorities can develop appropriate criteria for determining feasibility and infeasibility criteria for these types of situations

. EPA also notes that permitting authorities may consider alternative erosion and sediment control requirements to provide flexibility for sites that are unable to implement buffers in order to minimize pollutant discharges

to surface waters.

( 8 ) C ircumstances that make directing stormwater to vegetated areas to increase

sediment r

emoval and maximize stormwater infiltration “infeasible”

.

EPA does not intend for this requirement to conflict with state water right law, and thus the Agency believes that it would be infeasible to direct stormwater to vegetated areas to increase

sedimen t removal and maximize stormwater infiltration where doing so would conflict with state water right law. In addition, EPA notes that dispersion to vegetated areas may not be appropriate in some arid and semi

- arid areas where little or no vegetation exists and slow or

non

- infiltrating soils are present . However, in arid and semi

- arid areas with soils that will readily infiltrate (e.g., hydrologic soil group A or B soils), dispersion and infiltration techniques may still be feasible and appropriate and can ac complish significant volume (i.e., pollutant) reductions

. These techniques may also not be appropriate for certain projects, such as trench excavations in urban areas where pervious or vegetated areas within the project footprint are non

- existent.

For some highly developed projects, there may not be available land that can be used as a discharge area for stormwater or the available land may be very small in relation to the volume of stormwater requiring management. In these cases, this requirement may not b e feasible for managing all of the stormwater, but management of some of the stormwater through dispersion and infiltration may be feasible.