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

1 Responses specific to UWAG concerns in EPA’s Responses to Comments Document

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1. Not feasible or desirable to channelize flow in all situations, so control of stormwater volume and velocity within the site is not appropriate.

Pg. 25 Comments Response:

“ EPA acknowledges one commenter’s concern about regulating peak flow rates. In the non

numeric minimum controls, the following control measure addresses this issue as follows,

“control stormwater dis charges, including both peak flowrates and total stormwater volume, to

minimize erosion at outlets and to minimize downstream channel and streambank erosion (Section X.B. of the preamble).” EPA notes that while this requirement applies to all regulated

sit es, EPA understands that for some projects, such as linear utility projects, it is common practice to avoid channelizing flow and to instead utilize dispersion or other techniques to manage construction stormwater. It is EPA’s expectation that projects tha t do not channelize flow through the construction of conveyances such as channels, ditches, slope drains, etc., would not need to implement specific controls, such as stabilized outlets, to manage peak

flowrates and stormwater volumes to minimize erosion a nd outlets and to minimize downstream channel and streambank erosion. EPA considers the use of dispersion or diffuse discharge through perimeter controls as adequate controls for this requirement. The regulation of discharges that occur after construction activity is outside the scope of the final rule. No further

response necessary. ” (emphasis added)

Pg. 148 Comment Response:

“ EPA does not fully understand commenter’s concern about the need for discharge rate control
in areas where there are no water courses. In such areas, this condition would not exist and the need to control the rate of discharge would not exist. With respect to linear projects, the need for discharge rate control would not be needed if water were not being impounded or concentrated or conveyed in channels, ditches, etc. In general, this requirement is linked to the need to control discharges from basins and i mpoundments so that large volumes of water are not causing scouring of the receiving stream. It seems that this would not occur at many linear projects and EPA would not expect these types of controls to be required in these instances. ” (emphasis added)

2. Minimizing soil compaction should not be a requirement in areas where soil is intended to be compac ted, e.g., stabilized pads and access roads

.

Pg. 541 Comment Response:

“ The rule language at 450.21(a)(7) regarding soil compaction now states that perm ittees should “Minimize soil compaction and, unless infeasible, preserve topsoil.” 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 concer ns. For example, EPA would not expect permittees to minimize compaction in areas, such as where roads, foundations, utility tower pads, footings or other structures are to be built, or on embankments, where soilSupplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

2 compaction is necessary by design. Rather, t his requirement is intended to apply to other areas of the site, such as those where vegetation is to be preserved. Minimizing soil compaction reduces the amount of runoff and erosion that occurs, thereby reducing the amount of pollutants in the discharge. ” (emphasis added)

3. Minimizing exposure of stormwater to building materials is not appropriate for materials that are intended to be exposed, e.g., poles and towers

.

Pg. 541 Comment Response:

“ In terms of minimizing exposure of building materials, building products, construction wastes, trash, landscape matarials, fertilizers, pesticides, herbicides, detergents, sanitary waste and other materials present on the site to stormwater, EPA acknowledges that this will not be

feasible for some materials an d on some projects. For example, some building materials are intended to be exposed to precipitation following construction. An example would be steel used to construct an electric utility tower or a pre

- cast concrete bridge segment. In these cases, EPA

wo uld not expect that controls would be implemented to minimize exposure to precipitation since this would likely be infeasible since these materials, due to their size, could not be placed under cover. Another example would be pipeline sections that are sto red on

- site or near a site prior to placement in the ground. Providing cover for these materials would likely be infeasible due to their size. Some materials, such as stone and brick, are inert and are likely not to produce pollutants if exposed to precipi tation. EPA expects that permitting authorities will apply discretion in applying this provision of the regulation to require minimizing exposure only to those materials for which it is feasible and for those materials that are likely to be pollutant

sourc es

. ” (emphasis added)

4. Soil stabilization is not appropriate for some areas, such as dirt access roads, that are

intended to remain un

- vegetated.

Pg. 135 Comment Response:

“ The requirement to stabilize has been revised for the final rule. The final ru le states that permittees are required to, at a minimum, initiate soil stabilization measures immediately whenever any clearing, grading, excavating or other earth disturbing activities have permanently ceased on any portion of the site, or temporarily cea sed on any portion of the site and will not resume for a period exceeding 14 calendar days. Stabilization must be completed within a period of time determined by the permitting authority. In arid, semiarid, and drought

- stricken areas where initiating veget ative stabilization measures immediately is infeasible, vegetative stabilization measures must be initiated as soon as practicable. EPA disagrees that stabilization should not be required until the overall project is complete as that would leave the soil e xposed for an open ended period of time when construction activity is not ongoing. EPA acknowledges that some portions of some projects are inten d ed to be left unvegetated or unstabilized following construction. An example would be a dirt access road or a utility pole pad where the final plan calls for the area to remain a dirt road or an unstabilized pad. EPA does not expect temporary or permanent stabilization measures to be applied to these areas unless required by the permitting authority. ” (emphasis a dded)