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

1 40 CFR 450.21(b) Soil Stabilization. Stabilization of disturbed areas must, at a minimum, be initiated immediately whenever any clearing, grading, excavating or other earth disturbing activities have permanently ceased on any portion of the site, or temporarily ceased on any portion of the s ite 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 vegetative stabilization measu res immediately is infeasible, alternative stabilization measures must be employed as specified by the permitting authority.

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(1) T his non

- numeric effluent limitation controls or m inimiz es the discharge of

stormwater from the site

.

Exposed soils erode at a much higher rate than stabilized soils. Erosion is caused by detachment of soil particles by rainfall, by flowing water and by wind. Stabilization measures, including mulches, vegetation and rolled erosion control products

, will reduce raindrop impact energy and reduce soil detachment and transport. This is because the raindrops will hit the cover material, as opposed to the soil particles. When the raindrop hits the cover mater ial, the energy of the falling raindrop is dispersed. If the cover material were not there, then the raindrop would strike the soil particles and may cause detachment. Flowing water would then transport the soil particles downslope. Stabilization also redu ces erosion because the plant root material anchors the soil particles in

- place. This reduces detachment by raindrops as well as transport by flowing water. Stabilization also reduces erosion by wind. Soil eroded by wind can be transported and deposited to other areas of the site (or off

- site), where rainfall and flowing water can mobilize the deposited soil and transport it to receiving waters

. Stabilization of exposed soil areas is the most important and effective means of reducing erosion and discharge o f sediment from construction sites. Allowing disturbed areas that have r eached final grade or that will not be disturbed in the near future to stay disturbed for 14 additional days would significantly increase

the amount of time available for erosion to oc cur. While mobilized sediment can be removed, to some extent, in downslope sediment controls, these controls will not remove all sediment, turbidity and other pollutants because their performance is variable. See example of sediment basin provided in Supp lemental Explanation in Support of 450.21(a)(1). Therefore, a pollution

prevention approach will reduce the amount of sediment mobilized in the first place and reduce the quantity of pollutants discharged from construction sites.

Both vegetative and non

- v egetative stabilization measures may be used as both temporary and permanent stabilization measures in all areas, depending on the nature of the construction activity. In arid, semi

- arid or drought

- stricken areas, vegetative stabilization may not be feasib le. In these cases, the use of non

- vegetative stabilization, both as temporary or permanent measures, may be appropriate.

(2) What EPA does not mean by this requirement

.

EPA acknowledges that some portions of some projects are intended 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. EPA also notes that re

- disturbance of some stabilized areas may be necessary during construction projects. For example, equipment may need to drive over

stabilized areas to access portions of the site. In addition, some portion s of a site that may not be undergoing clearing, grading, excavating or other earth disturbing activities may need toSupplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

2 remain disturbed. An example might be a dirt access road that has reached final grad e, but may not be paved until later in the project. In these cases, compaction of the soil, covering with gravel and/or application of a soil binder may be considered adequate temporary stabilization

measures.

( 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 s election 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 environmen tal progress made to date by ensuring that all construction sites meet a minimum standard of excellence by adopting those erosion and sediment controls that have evolved and are now accepted across the country.” Id. NAHB urged EPA to broaden “best manage ment 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 a t 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 relying on BMP

- based approaches to achieve environmental objectives. EPA also should rely on a BMP

- based approach for the C&D ELG rulemaking.” I d. 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)( 1 ) to make that provision read as
follows: “Stabilize disturbed soils when earth disturbing work has been stopped on that portion of the site and will not resume for a period exceeding 14 calendar days, weather permitting.” EPA had proposed “Stabilize disturbed soils immediately when earth disturbing work has
tempora rily or permanently ceased. Stabilization measures must be implemented immediately on any portion of the site whenever final grade is reached or when earth disturbing work has been stopped on that portion of the site and will not resume for a period excee ding 14 calendar days.” Thus, while NAHB suggested changes to EPA’s proposed provision, it did not suggest deleting the provision, thereby acknowledging, consistent with its overall comments in support of

a BMP

- only ELG, that stabilizing disturbed soils i s key to 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

- 1 360.

( 4 ) Implementation 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 t he ELG verbatim into its draft proposed NPDES permit as the technology

- based effluent limitation, dischargersSupplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

3 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 un fairly 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 requ irement 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.

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

.

The provision, as stated, requires initiation immediately whenever any clearing, grading, excavating or other earth disturbing activities have permanently ceased on any portion of the site, or temporarily ceased on any portion of the site and will not resume for a period exceeding 14 calendar days. S tabilization must be completed within a period of time determined by the permitting authority. Additional flexibility is provide d in arid, semi

- arid and drought

- stricken

areas.

( 6 ) What EPA means by terms “initiated”, “immediately”, and “period of time”

.

The term “ i nitiated” in this context of this requirement means that the permittee must

take some action towards stabilization. The rule provides some flexibility in terms of what constitutes initiation of stabilization that may be further defined by the permitting authority. EPA intends that o ptimally, the actions taken to initiate stabiliza tion include

those that involve changes to the disturbed land area , such as the physical preparation of the exposed area for seeding

, planting, or the installation of other erosion control products . However, EPA acknowledges that other types of actions may be considered

as having initiated sta bilization as well , such as finalizing arrangements to have stabilization product fully installed by the deadline for completing stabilization. The permitting authority has flexibility to specify in the permit what series of actions it

considers to constit ute the initiation of stabilization.

The term “ i mmediately” in the context of this requirement means that the permittee must, as soon as possible and generally not later than the same day, take some action

towards stabilization as soon as any clearing, grading, excavating or other earth disturbing activities have ceased. The use of the term “ immediately ” is not meant to create a liability for a violation because stabilization is not initiated the second, the

min ute or hour after disturbance. The term is used to define a reasonable deadline for initiating stabilization measures . In this context, the provision requires construction operators to initiate stabilization measures immediately whenever earth

- disturbing activities on any portion of the site have t emporarily ceased and will not resume for a period of 14 or more days, or whenever such activities have permanently ceased. Therefore, where construction activities have temporarily or permanently ceased in an

area of the site

, initiation of stabilization generally must begin on the same day as the work has stopped so that the period of soil exposure is minimized

. If an operator completes grading of an area at the end of a work day, then “immediately” could

reasonabl y be interpreted to mean that the operato r must initiate stabilization activities on the next work day.Supplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

4 In most instances, the operator should know when construction is scheduled to cease in an area, and therefore the requirement to initiate stabilization work immediately is something that should fit within the construction project’s overall sc hedule of activities on

the site

. EPA acknowledges , however, that there may be some instances in which it is not possible to know at first whether work has temporarily ceased for a pe riod of 14 or more days, and therefore whether the requirement to stabilize applies. For instance,

where an operator experiences an unplanned or unanticipated delay in construction due to circumstances beyond its control (e.g., sudden work stoppage due to unanticipated problems associated with construction labor, funding, or other issues related to the ability to work on the site, weather conditions rendering the site unsuitable for the continuation of construction work)

, and it is not known at first how lo ng the work will be delayed, the permitting authority may find that it is reasonable to allow for the immediate initiation of stabilization as soon as the operator knows with reasonable certainty that work will be stopped for 14 or more days.

The phrase “period of t ime” as used in the provision means the amount or duration of time (for example, a number of days) that the permittee has from the initiation of stabilization activities until the stabilization activities must be complete. This gives t he permi tting authority the discretion to define what period of time it considers appropriate for requiring the construction operator to complete stabilization activities after having

initiated them. EPA believes the permitting authority is in the best position t o define this period of time based on such factors as prevalent soil conditions, vegetative types, precipitation patterns, etc.

(7 ) Whether t

emporary cessation that exceed s 14 calendar days through no fault of the operator would trigger a permit violatio n

.

EPA acknowledges that there may be some instances in which it is not possible to know at first whether work has temporarily ceased for a period of 14 or more days, and therefore whether the requirement to stabilize applies. For instance, and as mentioned above, where an operator experiences an unplanned or unanticipated delay in construction due to circumstances beyond its control (e.g., sudden work stoppage due to unanticipated problems associated with construction labor, funding, or oth er issues related to the ability to work on the site, weather conditions rendering the site unsuitable for the continuation of construction work)

, and it is not known at first how long the work will be delayed, the permitting authority may reasonably

deter mine that it is allowable for the operator to immediately initiate stabilization as soon as the
operator kno w s with reasonable certainty that work w il l be stopped for 14 or more days.