Supp lemental 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: (7) Minimize soil compaction and, unless infeasible, preserv e topsoil.

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(1) M inimizing soil compaction and, unless infeasible, preserving topsoil control s or minimiz es the discharge of stormwater from the site

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This requirement is des igned to reduce the amount of soil eroded and discharged from the site by reducing the amount of runoff generated and by providing conditions conducive to establishing vegetative stabilization. Compacting soil increases the amount of runoff produced.

This is because compacted soil does not allow water to infiltrate as rapidly as loose soil. Minimizing soil compaction allows for infiltration and retention of stormwater within the soil, which reduces the amount of runoff. Reducing the amount of runoff will re duce erosion, and therefore reduce the amount of sediment and other pollutants that can be transported within the site and to sediment controls and through perimeter controls. Since sediment controls and perimeter controls are not 100% effective in removin g sediment and other pollutants, reducing

the amount of sediment and runoff directed to these controls will reduce the amount of pollutants discharged from these controls.

Topsoil improves soil structure and provides a favorable growing medium for tempora ry and permanent vegetative stabilization measures. Preserving topsoil allows for better vegetative stabilization. Better vegetative stabilization reduces erosion rates of the underlying soil and also increases the infiltrative capacity of the soil. Reduci ng erosion rates and reducing the runoff volume will reduce the amount of sediment transported to downslope sediment and perimeter controls. Since sediment controls and perimeter controls are not 100% effective in removing sediment and other pollutants, re ducing the amount of sediment and runoff directed to these controls will reduce the amount of pollutants discharged from these controls.

Preservation of topsoil also means limiting disturbance and removal of the topsoil and associated vegetation. Limiting clearing and grading to only those areas where necessary to accommodate the building footprint is an example of topsoil preservation. Preserving topsoil in this manner would reduce the volume of stormwater as well as the quantity of sediment and other pol lutants mobilized from these areas of preservation, which would reduce the amount of pollutants discharged from the site.

Topsoil stockpile areas , if used, should be prevented from eroding, which can be accomplished by using various cover materials. Use of temporary vegetative stabilization measures for topsoil areas may also be considered if the stockpiles are to remain on

- site for an extended period of time before being used.

(2) What EPA does not mean by this requirement

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EPA notes that the “minimize soil compaction” language is meant to apply to those areas of the site where soil compaction is not necessary for structural or stability concerns. For example,

EPA would not e xpect permittees to minimize compaction in areas, such as where roads, foundations, footings or other structures are to be built, or on embankments, where soil compaction is necessary by design. Rather, this requirement is intended to apply to other areas of the site, such as those where vegetation is to be preserved. EPA notes that some projects may be designed to be highly impervious after construction, and therefore little or no vegetationSupp lemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

2 is intended to remain. In these cases (and perhaps others), prese rving topsoil at the site would not be feasible since the topsoil would not be necessary for establishing vegetation. Another case where it may not be feasible to preserve topsoil would be if the topsoil is of poor quality or

contaminated such that it woul d not be beneficial for establishing vegetation. Although poor topsoil may be improved through addition of soil amendments, there may be cases where this is not feasible or where keeping the topsoil on

- site would conflict with other regulations or

programs with respect to contaminated soils. Although not a requirement of this rule, minimizing soil compaction may be necessary in areas of the site where post

- construction controls are to be designed to infiltrate stormwater. Examples of these areas would be ar eas underneath porous pavement systems or areas where infiltration basins are to be installed. Consideration of soil compaction during the construction phase would be critical to ensuring proper operation of these types of practices.

For some projects w here the construction envelope may encompass the entire land area, there may not be space available on

- site to stockpile topsoil that is removed. In these cases, the use of off

- site borrow or storage areas may be appropriate. In addition, topsoil may be so ld for use on other projects where more topsoil is available than needed on

- site. EPA considers diversion

to other uses where not needed on site to be a situation where it is not feasible to preserve all topsoil. NAHB comment ed on page 147 of their detaile d comment letter that EPA should add desirable topsoil to this requirement . While EPA has not changed the language of the rule, the term “unless infeasible” should provide sufficient flexibility for the permitting authority to require only preservation of topsoil that will foster vegetative stabilization.

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

numeric effluent limitati ons 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 a dopting those erosion and sediment controls that 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 cons truction 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

remov e 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 stormwater 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 rel ying on BMP

- based approaches to achieve environmental 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 suggest ed a revision to proposed 450.21(a)( 5 ) and (6) to make those provisions read as follows: “Preserve desirable topsoil and natural vegetation consistent withSupp lemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

3 project goals” and “Minimize soil compaction as ap propriate and consistent with other applicable building codes and requirements.” EPA had proposed “Preserve topsoil and natural vegetation” and “Minimize soil compaction by construction equipment in areas that will not contain permanent structures or wher e compaction is not necessary for structural integrity. In disturbed areas that will not contain structures or where compaction is not necessary for structural integrity, utilize deep ripping and decompaction of soils and incorporate organic matter to

res tore infiltrative capacity.” Thus, while NAHB suggested some chang es to EPA’s proposed provisions , it did not suggest deleting the provisions , thereby acknowledging, consistent with its overall comments in support of a BMP

- only ELG, that minimizing soil c ompaction and preserving desirable topsoil and natural vegetation are key to control ling 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 p roposed ELG/NSPS, as well as the

attachment to EPA

- HQ

- OW

- 2008

- 0465

- 1360.

Note also that, on page 14 7 of its detailed comment letter

, NAHB suggest ed that “EPA’s soil compaction BMP should be removed because there are other regulatory requirements that may address compaction associated with the type of construction, and this truly is a local issue related to land use planning and the natural hydrology of the area.” This comment is inconsistent with NAHB’s suggested edit in its redline/strikeout “precisely crafted edits” to the soil compaction BMP, where NAHB suggested edits to it but did not suggest removing it from the regulation

. However, NAHB state d on page 146 of its detailed comment letter that “NAHB believes that its redlined submission [i.e., redline/strikeout “precisely crafted edits”] speaks for

itself and does not wish to be bound by issues raised in this section of the comments. ” (emphasis a dded) Thus, NAHB’s redline/strikeout “precisely crafted edits”, in which it merely suggested edits to this provision, take precedence over what NAHB stated in its detailed comment letter, in which it suggested deleting the soil compaction provision.

In any event, EPA included the “minimize soil compaction” provision in the final ELG/NSPS to ensure that permitting authorities consider the issue, but are provided with flexibility in implementing the requirement by the use of the term “minimize”

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(4 ) Im plementation of this provision in NPDES permits.

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

- 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 limitation, dischargers will have an opportunity to provide comment on the need for more specificity if they are

con cerned 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 constru ction 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 provisions requiring permittees to preserv e native topsoil on their site, unless infeasible

. The permit also requires that in areas of the site where final vegetative stabilization will occur or where infiltration practices will be installed, permittees must

either:Supp lemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

4 Restrict vehicle / equipment u se. Restrict vehicle and equipment use in these locations to avoid soil compaction; or

Use soil conditioning techniques. Prior to seeding or planting areas of exposed soil that have been compacted, use techniques that condition the soils to support vegetative growth, if necessary and feasible.

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

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This requirement is applicable during all phases of construction. During the initial clearing and grading phase, permittees should generally avoid the use of equipment and compaction of soils in those areas where soil compaction is not necessary for s tructural stability of design reasons. Compaction of soil in areas adjacent to structures is likely inevitable, due to the action of equipment. However, permittees can consider decompaction techniques, such as deep ripping, as a means of restoring infiltra tive capacity in these areas. EPA notes that this concept is consistent with the concepts of Low Impact Development (LID), and minimization of soil compaction during construction will facilitate use of LID and stormwater retention practices in the post

- dev eloped condition.

(6 ) When preservation of topsoil would be infeasible

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Preserving topsoil may be infeasible in certain situations. For example, if a site is to be highly developed in the post

- developed condition such that a majority of the site will be covered with structures or paved, then preserving topsoil for use at this site may be infeasible. In addition, some sites may not have space to stockpile topsoil on s ite for later use. EPA is aware that stockpiling of topsoil in off

- site locations or transfer of topsoil to other locations is frequently

used in these situation s and EPA would view this as acceptable practice. If off

- site areas are not readily available, then this would be an example of where this requirement could be considered

infeasible. Permitteees should consult permitting authorities for site

- specific considerations such

as these.