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

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40 CFR 450.21(d) Pollution Prevention Measures. Design, install, implement, and 

maintain effective pollution prevention measures to minimize the discharge of pollutants. 

At a minimum, such measures must be designed, installed, implemented and maintained 

to (2) Minimize the exposure of building materials, building products, construction 

wastes, trash, landscape materials, fertilizers, pesticides, herbicides, detergents, sanitary 

waste and other materials present on the site to precipitation and to stormwater. 

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(1) This BMP controls or minimizes the discharge of stormwater from the site. 

Materials stored on site, such as building materials, building products, construction wastes, 

trash, landscape materials, fertilizers, pesticides, herbicides, detergents, sanitary waste and 

other materials constitute or can generate pollutants that can be discharged from the site if 

these materials are exposed to precipitation or to stormwater. For some materials, such as 

paints, solvents, pesticides/herbicides, etc., it is appropriate to prevent exposure of these 

materials to precipitation or to stormwater until they are to be used on the site. This can be 

accomplished by storing these materials in rain-proof containers, inside vehicles or in other 

covered areas to prevent their exposure. Trash and other construction debris can be collected 

and placed in dumpsters or hoppers until these materials can be hauled off-site for disposal. 

Tarps or other covers can be placed over materials until they are to be used. The specific 

controls will depend on the material, its intended use, and the nature of the material. Therefore, 

EPA believes that permitting authorities should exercise discretion when determining what 

materials should be prevented from being exposed to precipitation or to stormwater (and should 

therefore be covered, etc.) and what materials do not need to be prevented from being exposed 

to precipitation or stormwater since a material-by-material enumeration by EPA is not 

appropriate.

(2) What EPA does not mean by this requirement.

For some materials, such as construction materials, minimizing the exposure to stormwater and 

precipitation may not be feasible or necessary. For some materials that are designed to be 

exposed to stormwater after construction, such as pre-cast concrete bridge components, steel 

for transmission towers, power poles, tower components, insulators, conductors, pipes, 

electrical and other equipment, minimization of exposure to stormwater would be infeasible 

and/or inappropriate. Also, it would be infeasible to prevent exposure of some materials to 

precipitation and stormwater. For example, pipe sections for a pipeline construction project are 

often stored outside in staging areas. Due to the number and size of these materials, covering 

these materials would be infeasible and inappropriate. Inert materials, such as stone, bricks, 

etc., and other materials that are also not expected to contribute pollutants to stormwater, would 

also likely not be appropriate to mandate no-exposure to stormwater. Obviously, these materials 

should be stored in areas where they will not be exposed to flowing stormwater, but precipitation 

falling on these materials and then mixing with stormwater on the site would likely not be of 

concern. 

(3) In its comments on the proposed C&D ELG/NSPS, NAHB expressed support for nonnumeric 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, 
Supplemental Explanation in Support of BMPs in C&D ELG and NSPS February 15, 2012

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“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 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 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 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.” Id. at 46 (emphasis in original).

In addition, in its redline/strikeout “precisely crafted edits” of EPA’s proposed Option 1, the BMPonly ELG, NAHB suggested revisions to proposed 450.21(c)(6) to make that provision read as 

follows: “Minimize the exposure of stormwater to building materials, landscape materials, 

fertilizers, pesticides, herbicides, detergents, and other liquid or dry products. Implement 

appropriate chemical spill prevention and response procedures. Permittees should ensure that 

any significant spills and leaks are addressed appropriately and actions are taken before the 

next storm event to help prevent the discharge of any related pollutants.” EPA had proposed 

“Implement measures to minimize the exposure of stormwater to building materials, landscape 

materials, fertilizers, pesticides, herbicides, detergents, and other liquid or dry products. 

Implement appropriate chemical spill prevention and response procedures. Any spills and leaks 

that do occur shall be immediately addressed in a manner that prevents the discharge of any 

pollutants.” Thus, while NAHB suggested changes to the provision, it did not suggest deleting 

the provision, thereby acknowledging, consistent with its overall comments in support of a BMPonly ELG, that taking such measures as detailed, at a minimum, in this BMP provision as edited 

by NAHB, is 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-

1360. 

(4) Implementation 

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 

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

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

their effluent limitations. 

In the 2012 CGP, EPA has implemented this provision by including specific requirements 

regarding the storage of construction products, wastes, and materials; specific requirements 

regarding the clean-up of spills; and specific requirements regarding the disposal of certain 

materials. 

(5) Appropriate time for implementation of this BMP in the construction process.

Materials should be prevented from exposure to precipitation and stormwater as they are 

brought onto the site. If precipitation is forecast, then it may be appropriate to move or provide 

cover for materials so as to limit their exposure to precipitation and stormwater. Trash and other 

debris should be frequently collected and removed so as not to become a source of pollution.