[Federal Register: November 28, 2008 (Volume 73, Number 230)]
[Proposed Rules]
[Page 72561-72614]
[DOCID:fr28no08-29]

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Part II

Environmental Protection Agency

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40 CFR Part 450

Effluent Limitations Guidelines and Standards for the Construction and
Development Point Source Category; Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 450

[EPA-HQ-OW-2008-0465; FRL-8744-1]
RIN 2040-AE91

Effluent Limitations Guidelines and Standards for the
Construction and Development Point Source Category

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency is proposing a regulation
that would strengthen the existing regulatory program for discharges
from construction sites by establishing technology-based Effluent
Limitations Guidelines and New Source Performance Standards for the
Construction and Development (C&D) point source category. This
proposal, if implemented, would significantly reduce the amount of
sediment and other pollutants discharged from construction sites. EPA
estimates that this proposed rule would cost $1.9 billion dollars per
year with annual monetized benefits of $332.9 million. This proposed
rule requests comment and information on the proposed regulation and an
alternate option with a different numeric limit based on different
technologies, as well as specific aspects of the proposal such as
technologies, costs, loading reductions, and economic achievability.

DATES: Comments must be received on or before February 26, 2009.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2008-0465, by one of the following methods:
     http://www.regulations.gov: This is EPA's preferred
approach, although you may use the alternatives presented below. Follow
the on-line instructions for submitting comments.
     E-mail<EMAIL_ADDRESS>     Mail: USEPA Docket Center, Environmental Protection
Agency, Docket Number EPA-HQ-OW-2008-0465, Mailcode 2822T, 1200
Pennsylvania Ave., NW., Washington, DC 20460.
     Hand Delivery: USEPA Docket Center, Public Reading Room,
1301 Constitution Ave., NW., Room 3334, EPA West Building, Washington
DC 20004. Such deliveries are only accepted during the Docket's normal
hours of operation, and special arrangements should be made for
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2008-
0465. EPA's policy is that all comments received will be included in
the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://
www.regulations.gov or e-mail. The http://www.regulations.gov Web site
is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov, your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket visit the EPA Docket Center homepage at http://www.epa.gov/
epahome/dockets.htm.
    Docket: All documents in the docket are listed in the http://
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the USEPA Docket
Center, Public Reading Room, Room 3334, EPA West Building, 1301
Constitution Ave., NW., Washington DC. The Public Reading Room is open
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays. The telephone number for the Public Reading Room is (202)
566-1744, and the telephone number for the EPA Docket Center is (202)
566-2426. Please note that several of the support documents are
available at no charge on EPA's Web site; see Supporting Documentation
below.

FOR FURTHER INFORMATION CONTACT: For technical information concerning
today's proposed rule, contact Mr. Jesse W. Pritts at<PHONE_NUMBER>
(pritts.jesse@epa.gov). For economic information contact Mr. Todd Doley
at<PHONE_NUMBER> (doley.todd@epa.gov).

SUPPLEMENTARY INFORMATION:

Regulated Entities

    Entities potentially regulated by this action include:

------------------------------------------------------------------------
                                                         North American
                                                            Industry
          Category             Examples of regulated     Classification
                                      entities           System (NAICS)
                                                              code
------------------------------------------------------------------------
Industry                      Construction activities required to obtain
                                NPDES permit coverage and performing the
                                         following activities:
                             -------------------------------------------
                                Construction of                      236
                                 buildings, including
                                 building, developing
                                 and general
                                 contracting.
                                Heavy and civil                      237
                                 engineering
                                 construction,
                                 including land
                                 subdivision.
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    EPA does not intend the preceding table to be exhaustive, but
provides it as a guide for readers regarding entities likely to be
regulated by this action. This table lists the types of entities that
EPA is now aware could potentially be regulated by this action. Other
types of entities not listed in the table could also be regulated. To
determine whether your facility is regulated by this action, you should
carefully examine the applicability criteria in Sec.  450.10 of today's
proposed rule and the definition of ``construction activity'' and
``small construction activity'' in existing EPA regulations at 40 CFR
122.26(b)(14)(x) and 122.26(b)(15), respectively. If you have questions
regarding the

applicability of this action to a particular entity, consult one of the
persons listed for technical information in the preceding FOR FURTHER
INFORMATION CONTACT section.

Supporting Documentation

    Several key documents support the proposed regulation:
    1. ``Development Document for Proposed Effluent Guidelines and
Standards for the Construction and Development Category,'' EPA-821-R-
08-007. (``Development Document'') This document presents EPA's
methodology and technical conclusions concerning the C&D category.
    2. ``Economic Analysis for Proposed Effluent Guidelines and
Standards for the Construction and Development Category,'' EPA-821-R-
08-008. (``Economic Analysis'') This document presents the methodology
employed to assess economic impacts of the proposed rule and the
results of the analysis.
    3. ``Environmental Impact and Benefits Assessment for Proposed
Effluent Guidelines and Standards for the Construction and Development
Category,'' EPA-821-R-08-009 (``Environmental Assessment''). This
document presents the methodology to assess environmental impacts and
benefits of the proposed rule and the results of the analysis.
    Major supporting documents are available in hard copy from the
National Service Center for Environmental Publications (NSCEP), U.S.
EPA/NSCEP, P.O. Box 42419, Cincinnati, Ohio, USA 45242-2419, telephone
800-490-9198, http://www.epa.gov/ncepihom/. You can obtain electronic
copies of this preamble and proposed rule as well as the technical and
economic support documents for today's proposal at EPA's Web site for
the C&D rule, http://www.epa.gov/waterscience/guide/construction.

Overview

    This preamble describes the terms, acronyms, and abbreviations used
in this document; the background documents that support these proposed
regulations; the legal authority of this proposed rule; a summary of
the proposal; background information; and the technical and economic
methodologies used by the Agency to develop this proposed regulation.
While EPA solicits comments on this entire proposal, EPA emphasizes
specific areas of interest where we would particularly like comments,
information and data.

Table of Contents

I. Legal Authority
II. Purpose & Summary of the Proposed Rule
III. Background on Existing Regulatory Program
    A. Clean Water Act
    B. NPDES Stormwater Permit Program
    C. Other State and Local Stormwater Requirements
    D. Technology-Based Effluent Limitations Guidelines and
Standards
IV. Scope of the Proposal
V. Overview of the Construction and Development Industry and
Construction Activities
VI. Summary of Data Collection Activities
    A. State Data
    B. National Land Cover Dataset (NLCD)
    C. Enhanced River Reach File 1.2 (ERF1)
    D. NPDES Notice of Intent (NOI) Data
    E. Soils Data
    F. NOAA Rainfall Data
    G. Parameter Elevation Regressions on Independent Slopes Model
(PRISM)
    H. Revised Universal Soil Loss Equation (RUSLE) R Factors
    I. Economic Data
VII. Characteristics of Discharges From Construction Activity
VIII. Description of Available Technologies
    A. Introduction
    B. Erosion Control Measures
    C. Sediment Control Measures
    D. Other Construction and Development Site Management Practices
IX. Development of Effluent Limitations Guidelines and Standards
    A. Description of the Regulatory Options Considered
    B. Effluent Limitations Included in All Regulatory Options
    C. Options for BPT, BCT, BAT and NSPS
    D. Option Selection Rationale for BPT
    E. Option Selection Rationale for BAT and NSPS
    F. Option Selection Rationale for BCT
X. Methodology for Estimating Costs to the Construction and
Development Industry
XI. Economic Impact and Social Cost Analysis
    A. Introduction
    B. Description of Economic Activity
    C. Method for Estimating Economic Impacts
    D. Results
XII. Cost-Effectiveness Analysis
XIII. Non Water-Quality Environmental Impacts
    A. Air Pollution
    B. Solid Waste Generation
    C. Energy Usage
XIV. Environmental Assessment
    A. Introduction
    B. Methodology for Estimating Environmental Impacts and
Pollutant Reductions
XV. Benefit Analysis
    A. Benefits Categories Estimated
    B. Quantification of Benefits
XVI. Monetized Benefit-Cost Comparison
XVII. Approach to Determining Long-Term Averages, Variability
Factors, and Effluent Limitations and Standards
    A. Definitions
    B. Data Selection
    C. Statistical Percentile Basis for Limitations
    D. Daily Maximum Limitations
    E. Engineering Review of Limitations
    F. Monthly Average Limitations
XVIII. Regulatory Implementation
    A. Relationship of Effluent Guidelines to NPDES Permits and ELG
Compliance Dates
    B. Upset and Bypass Provisions
    C. Variances and Waivers
    D. Other Clean Water Act Requirements
XIX. Related Acts of Congress, Executive Orders, and Agency
Initiatives
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175 (Consultation and Coordination With
Indian Tribal Governments)
    G. Executive Order 13045: Protection of Children from
Environmental Health Risks and Safety Risks
    H. Executive Order 13211 (Energy Effects)
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations.
XX. Solicitation of Data and Comments
    A. General Solicitation of Comment
    B. Specific Solicitation of Comments and Data
    C. Guidelines for Submission of Analytical Data

I. Legal Authority

    EPA is proposing this regulation under the authorities of sections
301, 304, 306, 308, 402, 501 and 510 of the Clean Water Act (CWA), 33
U.S.C. 1311, 1314, 1316, 1318, 1342, 1361 and 1370 and pursuant to the
Pollution Prevention Act of 1990, 42 U.S.C. 13101 et seq.

II. Purpose & Summary of the Proposed Rule

    Despite substantial improvements in the nation's water quality
since the inception of the Clean Water Act, 45 percent of assessed
river and stream miles, 47 percent of assessed lake acres, and 32
percent of assessed square miles of estuaries show impairments from a
wide range of sources. Improper control of stormwater discharges from
construction activity is among the many contributors of sediment which
is one of the major remaining water quality problems throughout the
United States. Sediment is the leading cause of water quality
impairment for streams and rivers. It is also one of the leading causes
of lake and reservoir water quality impairment and wetland degradation.
Turbidity and suspended solids are also major sources of water quality
impairment nationwide. Turbidity or suspended solids impair 695,133
miles of streams nationwide. In

addition, 376,832 acres of lakes and reservoirs have been documented as
impaired by turbidity or suspended solids nationwide. The sediment and
turbidity entrained in stormwater discharges from construction activity
contributes to harm in aquatic ecosystems, increases drinking water
treatment costs, and contributes to impairment to recreational uses of
impacted waters. Sediment can also accumulate in rivers, lakes, and
reservoirs, leading to the need for dredging or other mitigation.
    Construction activity typically involves site selection and
planning, and land-disturbing tasks such as clearing, excavating and
grading. Disturbed soil, if not managed properly, can be easily washed
off-site during storm events. Stormwater discharges generated during
construction activities can cause an array of physical, chemical and
biological impacts. Sediment discharges can cause an array of physical
and biological impacts on receiving waters. In addition to sediment, a
number of other pollutants (e.g., metals and nutrients) are
preferentially absorbed or adsorbed onto mineral or organic particles
found in fine sediment. These pollutants can cause an array of chemical
and biological water quality impairments. The interconnected processes
of erosion (i.e., detachment of soil particles by water), sediment
transport, and delivery to receiving waters are the primary pathways
for the addition of pollutants from construction and development (C&D)
sites into aquatic systems.
    A primary concern at most C&D sites is the erosion and transport
process related to fine sediment because rain splash, rills (small
channels typically less than one foot deep) and sheetwash (thin sheets
of water flowing across a surface) encourage the detachment and
transport of sediment to water bodies. Although streams and rivers
naturally carry sediment loads, discharges from construction activity
can elevate these loads to levels above those in undisturbed
watersheds.
    Existing national stormwater regulations at 40 CFR 122.26 require
permittees to implement control measures to manage discharges
associated with construction activity. Today's proposal would establish
a technology-based ``floor'' or minimum requirements on a national
basis. This rule would constitute the nationally applicable,
technology-based effluent limitations guidelines (ELGs) and new source
performance standards (NSPS) (referred to collectively in this notice
as ``ELGs'' or ``effluent limitations guidelines,'' unless specifically
referencing NSPS), applicable to all dischargers currently required to
obtain a National Pollutant Discharge Elimination System (NPDES) permit
pursuant to 40 CFR 122.26(b)(14)(x) and 122.26(b)(15). The proposed
ELGs would require stormwater discharges from certain C&D sites to meet
effluent limitations designed to reduce the amount of sediment,
turbidity, Total Suspended Solids (TSS) and other pollutants in
stormwater discharges from the site. EPA acknowledges that many state
and local governments have existing effluent limitations and standards
for controlling stormwater and wastewater discharges from construction
sites. Today's proposed ELGs are intended to work in concert with these
existing state and local programs. Today's proposed regulation would
establish a numeric effluent limit for turbidity in discharges from
some C&D sites. EPA envisions these turbidity effluent limits as
requiring an additional layer of management practices and/or treatment
above what most state and local programs are currently requiring.
Permitting authorities would be required to incorporate these turbidity
limitations into their permits and permittees would be required to
implement control measures to meet a numeric turbidity limit in
discharges of stormwater from their C&D sites. EPA is not dictating
that a specific technology be used to meet the numeric limit, but is
specifying the maximum turbidity level that can be present in
discharges from C&D sites. However, EPA's proposed limits are based on
its assessment of what specific technologies can reliably achieve.
Permittees would have the flexibility to select management practices
that are best suited to site-specific conditions present on each
individual C&D site if they are able to consistently meet the limits.

III. Background on Existing Regulatory Program

A. Clean Water Act

    Congress passed the Federal Water Pollution Control Act of 1972
(Pub. L. 92-500, October 18, 1972) (hereinafter the Clean Water Act or
CWA), 33 U.S.C. 1251 et seq., with the stated objectives to ``restore
and maintain the chemical, physical, and biological integrity of the
Nation's waters.'' Section 101(a), 33 U.S.C. 1251(a). To achieve this
goal, the CWA provides that ``the discharge of any pollutant by any
person shall be unlawful'' except in compliance with other provisions
of the statute. CWA section 301(a). U.S.C. 1311. The CWA defines
``discharge of a pollutant'' broadly to include ``any addition of any
pollutant to navigable waters from any point source.'' CWA section
502(12). 33 U.S.C. 1362(12). EPA is authorized under CWA section 402(a)
to issue a National Pollutant Discharge Elimination System (NPDES)
permit for the discharge of any pollutant from a point source
notwithstanding Section 301(a). These NPDES permits are issued by EPA
regional offices or NPDES authorized state or tribal agencies. Since
1972, EPA and the states have issued NPDES permits to thousands of
dischargers, both industrial (e.g., manufacturing, energy and mining
facilities) and municipal (e.g., sewage treatment plants). As required
under Title III of the CWA, EPA has promulgated ELGs and standards for
many industrial point source categories, and these requirements are
incorporated into the permits.
    The Water Quality Act of 1987 (Pub. L. 100-4, February 4, 1987)
amended the CWA, adding CWA section 402(p) to require implementation of
a comprehensive program for addressing stormwater discharges. 33 U.S.C.
1342(p). The NPDES program was expanded by requiring EPA or NPDES
authorized states or tribes to issue NPDES permits for stormwater
discharges listed under Section 402(p)(2), which include municipal and
industrial stormwater discharges. Industrial stormwater dischargers,
municipal separate storm sewer systems and other stormwater dischargers
designated by EPA must obtain NPDES permits pursuant to CWA section
402(p). Stormwater discharges associated with industrial activity must
meet all applicable provisions of CWA sections 301 and 402, including
meeting technology-based effluent limitations.

B. NPDES Stormwater Permit Program

    EPA's Phase I stormwater regulations promulgated in 1990 identified
stormwater discharges associated with construction activity as one of
several types of industrial activity requiring an NPDES permit.
Dischargers must apply for and obtain authorization to discharge (or
``permit coverage'') (40 CFR 122.26(b)(14)(x) and (c)(1)). As described
in the Phase I regulations, a permit is required for discharges
associated with construction activity, including clearing, grading, and
excavation, if the construction activity:
     Will disturb five acres or greater; or
     Will disturb less than five acres but is part of a larger
common plan of development or sale whose total land disturbing
activities total five acres or greater.

EPA defines these ``large'' construction sites as one of the eleven
categories of stormwater dischargers associated with industrial
activity. (See 40 CFR 122.26(b)(14)).
    The Phase II stormwater regulations, promulgated in 1999, extended
permit coverage to construction activity that results in land
disturbance of one acre or greater (40 CFR 122.26(b)(15)), including
sites less than one acre that are part of a larger common plan of
development or sale whose total land disturbing activities total more
than an acre. EPA's NPDES regulations define these sites, i.e., sites
disturbing between one and five acres, as ``small'' construction sites.
    In addition to requiring permits for discharges associated with
construction activity, the NPDES regulations require permits for
certain municipal separate storm sewer systems (MS4s). Operators of
these MS4s, typically local governments, must develop and implement a
stormwater management program, including a requirement to address
stormwater discharges from construction activity. More details on the
requirements of MS4 programs are described in section III.B.2.
1. Stormwater Permits for Construction Activity
    The NPDES regulations provide two options for obtaining
authorization to discharge or ``permit coverage'': General permits and
individual permits. A brief description of these types of permits as
they apply to construction sites follows.
a. General NPDES Permits
    The vast majority of discharges from construction activity are
covered under NPDES general permits. EPA, states and tribes use general
permits to cover a group of similar dischargers under one permit. See
40 CFR 122.28. General permits simplify the process for dischargers to
obtain authorization to discharge, provide permit requirements for any
discharger that files a notice of intent to be covered, and reduce the
administrative workload for NPDES permitting authorities. General
permits, including a fact sheet describing the rationale for permit
conditions, are issued by NPDES permitting authorities through public
notice. Typically, to obtain authorization to discharge under a
construction general permit, a discharger (typically, a developer,
builder, or contractor) submits to the permitting authority a Notice of
Intent (NOI) to be covered under the general permit. By submitting the
NOI, the discharger acknowledges that it is eligible for coverage under
the general permit and agrees to the conditions in the published
general permit. Discharges from the construction activity are
authorized consistent with the terms and conditions established in the
general permit.
    EPA regulations allow NPDES permitting authorities to regulate
discharges from small C&D sites under a general permit without the
discharger submitting an NOI if the permitting authority determines an
NOI is inappropriate and the general permit includes language
acknowledging that an NOI is unnecessary (40 CFR 122.28(b)(2)(v)). To
implement such a requirement, the permitting authority must specify in
the public notice of the general permit any reasons why an NOI is not
required. In these instances, any stormwater discharges associated with
small construction activity are automatically covered under an
applicable general permit and the discharger is required to comply with
the terms, conditions and effluent limitations of such permit.
    Similarly, EPA, states and tribes have the authority to notify a
C&D site operator that it is covered by a general permit, even if that
operator has not submitted an NOI (40 CFR 122.28(b)(2)(vi)). In these
instances, the operator is given the opportunity to request coverage
under an individual permit. Individual permits are discussed in section
III.B.1.d.
b. EPA Construction General Permit
    Since 1992, EPA has issued a series of ``national'' Construction
General Permits (CGP) that cover areas where EPA is the NPDES
permitting authority. At present, EPA is the permitting authority in
five states (Alaska, Idaho, Massachusetts, New Hampshire, and New
Mexico), the District of Columbia, Puerto Rico, all other U.S.
territories with the exception of the Virgin Islands, federal
facilities in four states (Colorado, Delaware, Vermont, and
Washington), most Indian lands and a couple of other specifically
designated activities in specific states (e.g., oil and gas activities
in Texas and Oklahoma). EPA issued a final ``national'' CGP on July 1,
2003 (63 FR 7898), modified on November 22, 2004 (changes effective
January 21, 2005). EPA's current CGP became effective on June 30, 2008
(see 74 FR 40338). Following promulgation of the effluent limitations
guidelines, EPA will issue a revised CGP incorporating the new ELGs.
    The key component of EPA's CGP is the requirement to minimize
discharges of pollutants in stormwater discharges using control
measures that reflect best engineering practices. Dischargers must
minimize their discharge of pollutants in stormwater using appropriate
erosion and sediment control ``best management practices'' (BMPs) and
control measures for other pollutants such as litter, construction
debris, and construction chemicals that could be exposed to stormwater
and other wastewater. The 2008 CGP requires dischargers to develop and
implement a stormwater pollution prevention plan (SWPPP) to document
the steps they will take to comply with the terms, conditions and
effluent limitations of the permit. EPA's guidance manual, ``Developing
Your Stormwater Pollution Prevention Plan: A Guide for Construction
Sites,'' (EPA 833/R-060-04, May 2007; available on EPA's Web site at
http://www.epa.gov/npdes/stormwater) describes the SWPPP process in
detail. As detailed in EPA's CGP, the SWPPP must include a description
of the C&D site with maps showing drainage patterns, discharge points,
and locations of runoff controls; a description of the control measures
used; and inspection procedures. A copy of the SWPPP must be kept on
the construction site from the date of project initiation to the date
of final stabilization. The CGP does not require permittees to submit a
SWPPP to the permitting authority; however a copy must be readily
available to authorized inspectors during normal business hours.
    Other requirements in the CGP include conducting regular
inspections and reporting releases of reportable quantities of
hazardous substances.
    To discontinue permit coverage, a discharger must either complete
final stabilization of the site, transfer responsibility to another
party (e.g., a developer transferring land to a home builder), or for a
residential property, complete temporary stabilization and transfer the
property to the homeowner. The permittee submits a Notice of
Termination (NOT) Form to the permitting authority upon satisfying the
appropriate permit termination conditions described in the CGP.
c. State Construction General Permits
    Whether EPA, a state or a tribe issues the general permit, the CWA
requires that NPDES permits must include technology-based effluent
limitations. In addition, where technology-based effluent limitations
are insufficient for the discharge to meet applicable water quality
standards, the permit must contain water quality-based effluent
limitations as necessary to meet those standards. See sections 301,
304, 303, 306, and 402 of the CWA. PUD No. 1 of Jefferson County v.
Washington Department of Ecology, 511 U.S. 700, 704-705 (1994).

    For the most part, state-issued general permits for stormwater
discharges from construction activity have followed EPA's CGP format
and content, starting with EPA's first CGP issued in 1992 (57 FR 41176;
September 9, 1992). Over time, some states have changed components of
their permits to better address the specific conditions encountered at
construction sites within their jurisdiction (e.g., soil types,
topographic or climatic characteristics, or other relevant factors).
For example, Washington, Oregon and Vermont's CGPs include turbidity
action levels and discharge monitoring requirements for C&D sites
applicable to all or a subset of construction sites.
d. Individual NPDES Permits
    A permitting authority may require any C&D site to apply for an
individual permit rather than using the general permit. Likewise, any
discharger may request to be covered under an individual permit rather
than seek coverage under an otherwise applicable general permit (40 CFR
122.28(b)(3)). Unlike a general permit, an individual permit is
intended to be issued to one permittee, or a few co-permittees.
Individual permits for stormwater discharges from construction sites
are rarely used, but when done so, are most often used for very large
projects or projects located in sensitive watersheds. EPA estimates
that fewer than one half of one percent (< 0.5%) of all construction
sites are covered under individual permits.
2. Municipal Stormwater Permits and Local Government Regulation of
Stormwater Discharges Associated With Construction Activity
    Many local governments, as MS4 permittees, have a role to play in
the regulation of construction activities. This section provides an
overview of MS4 responsibilities associated with controlling stormwater
discharges from construction activity.
a. NPDES Requirements
    A municipal separate storm sewer system (MS4) is a conveyance or
system of conveyances designed or used for collecting or conveying
stormwater. These systems are not combined sewers and not part of a
Publicly Owned Treatment Works (POTW). See 40 CFR 122.26(b)(8). A
municipal separate storm sewer system (MS4) is all large, medium, and
small municipal storm sewers or those designated as such under the
regulations. See 40 CFR 122.26(b)) (18). The NPDES stormwater
regulations require many MS4s to apply for permits. In general, the
1990 Phase I rule requires MS4s serving populations of 100,000 or more
to obtain coverage under an MS4 individual permit. See 40 CFR
122.26(a)(3). The 1999 Phase II rule requires most small MS4s located
in urbanized areas also to obtain coverage. See 40 CFR 122.33. The
Phase II regulations also provide permitting authorities with the
authority to designate any additional MS4s located outside of urbanized
areas for permit coverage where the permitting authority determines
that storm water controls are needed for the discharge based on
wasteload allocations that are part of total maximum daily loads that
address pollutants of concern or the permitting authority or the EPA
Regional Administrator determines that the discharge, or category of
discharges within a geographic area, contributes to a violation of a
water quality standard or is a significant contributor of pollutants to
waters of the United States. 40 CFR 122.26(9)(i)(C) and (D). Regardless
of the type of permit, MS4s are required to develop stormwater
management programs that detail the procedures they will use to control
discharges of pollutants in stormwater from the MS4.
    Both the Phase I and II rules require regulated municipalities to
develop comprehensive stormwater management programs which include,
among other elements, the regulation of discharges from construction
sites. The Phase I regulations require medium and large MS4s to
implement and maintain a program to reduce pollutants in stormwater
runoff from construction sites, including procedures for site planning,
requirements for structural and non-structural BMPs, procedures for
identifying priorities for inspecting sites and enforcing control
measures, and development and dissemination of appropriate educational
and training materials. In general, the Phase II regulations require
small MS4s to develop, implement, and enforce a program to control
pollutants in stormwater runoff from construction activities which
includes developing an ordinance to require implementation of erosion
and sediment control practices, to control waste and to have procedures
for site plan review and site inspections. Thus, as described above,
both the Phase I and Phase II regulations specifically anticipate a
local program for regulating stormwater discharges from construction
activity. See 40 CFR 122.26(d)(2)(iv)(D) for Phase I MS4s and 40 CFR
122.34(b)(4) for Phase II MS4s. EPA has provided many guidance
materials to the NPDES permitting authorities and MS4s that recommend
components and activities for a well-operated local stormwater
management program.
    EPA promulgated two provisions intended to minimize potential
duplication of requirements or inconsistencies between requirements.
First, 40 CFR 122.35 provides that a small MS4 is allowed to rely on
another entity to satisfy its NPDES permit obligations, including
construction site control, provided the other entity implements a
program that is at least as stringent as the corresponding NPDES permit
requirements and the other entity agrees to implement the control
measures on the small MS4's behalf. Thus, for example, where a county
implements a construction site stormwater control program already, and
that program is at least as stringent as the controls required by a
small MS4's NPDES permit, the MS4 may reference that program in the
Notice of Intent to be covered by a general permit, or in its permit
application, rather than developing and implementing a new program to
require control of construction site stormwater within its
jurisdiction.
    Similarly, EPA or the state permitting authority may substitute
certain aspects of the requirements of the EPA or state permit by
incorporating by reference the requirements of a ``qualifying local
program'' in the EPA or state CGP. A ``qualifying local program'' is an
existing sediment and erosion control program that meets the minimum
requirements as established in 40 CFR 122.44(s). By incorporating a
qualifying local, state or tribal program into the EPA or state CGP,
construction sites covered by the qualifying program in that
jurisdiction would simply follow the incorporated local requirements in
order to meet the corresponding requirements of the EPA or state CGP.
b. EPA Guidance to Municipalities
    EPA developed several guidance documents for municipalities to
implement the NPDES Phase II rule.
     National Menu of BMPs (http://www.epa.gov/npdes/
menuofbmps/menu.htm). This document provides guidance to regulated MS4s
as to the types of practices they could use to develop and implement
their stormwater management programs. The menu includes descriptions of
practices that local programs can implement to reduce impacts of
stormwater discharges from construction activities.
     Measurable Goals Guidance for Phase II MS4s (http://
www.epa.gov/npdes/stormwater/measurablegoals). This document assists
small MS4s in defining performance targets and

includes examples of goals for practices to control stormwater
discharges from construction activities.
     Storm Water Phase II Compliance Assistance Guide (EPA 833-
R-00-002, March 2000, http://cfpub.epa.gov/npdes/stormwater/
smms4.cfm?program_id=6). The guide provides an overview of compliance
responsibilities for MS4s, small construction sites, and certain other
industrial stormwater discharges affected by the Phase II rule.
     Fact Sheets on various stormwater control technologies,
including hydrodynamic separators (EPA 832-F-99-017), infiltrative
practices (EPA 832-F-99-018 and EPA 832-F-99-019), modular treatment
systems (EPA 832-F-99-044), porous pavement (EPA 832-F-99-023), sand
filters (EPA 832-F-99-007), turf reinforcement mats (EPA 832-F-99-002),
vegetative covers (EPA 832-F-99-027), swales (EPA 832-F-99-006) and wet
detention ponds (EPA 832-F-99-048). (Available at http://www.epa.gov/
npdes/stormwater/; click on ``Publications.'')

C. Other State and Local Stormwater Requirements

    States and municipalities may have other requirements for flood
control, erosion and sediment control, and in many cases, stormwater
management. Many of these provisions were enacted before the
promulgation of the EPA Phase I stormwater rule although many have been
updated since. An EPA analysis found that all states have laws for
erosion and sediment control measures, with these laws implemented by
state, county, or local governments. A summary of existing state
requirements is provided in the Development Document.

D. Technology-Based Effluent Limitations Guidelines and Standards

    Effluent limitation guidelines and new source performance standards
are technology-based effluent limitations required by CWA sections 301
and 306 for categories or subcategories of point source dischargers.
These limitations, which can be either numeric or non-numeric, along
with water quality-based effluent limitations, if necessary, are
incorporated into NPDES permits. ELGs and NSPS are based on the degree
of control that can be achieved using various levels of pollutant
control technology, as defined in Title III of the CWA and outlined
below.
1. Best Practicable Control Technology Currently Available (BPT)
    In establishing effluent guidelines for a point source category,
the CWA requires EPA to specify BPT effluent limits for conventional,
toxic, and nonconventional pollutants. In doing so, EPA is required to
determine what level of control is technologically available and
economically practicable. CWA section 301(b)(1)(A). In specifying BPT,
the CWA requires EPA to look at a number of factors. EPA considers the
cost of achieving effluent reductions in relation to the effluent
reduction benefits. The Agency also considers the age of the equipment
and facilities, the processes employed and any required process
changes, engineering aspects of the control technologies, non-water
quality environmental impacts (including energy requirements), and such
other factors as the Administrator deems appropriate. CWA section
304(b)(1)(B). Traditionally, EPA establishes BPT effluent limitations
based on the average of the best performance of facilities within the
category of various ages, sizes, processes or other common
characteristics. Where existing performance is uniformly inadequate,
EPA may require higher levels of control than currently in place in a
category if the Agency determines that the technology can be
practicably applied. See e.g., American Frozen Foods Inst. v. Train,
539 F.2d 107, 117 (D.C. Cir. 1976).
    EPA assesses cost-reasonableness of BPT limitations by considering
the cost of treatment technologies in relation to the effluent
reduction benefits achieved. This inquiry does not limit EPA's broad
discretion to adopt BPT limitations that are achievable with available
technology unless the required additional reductions are ``wholly out
of proportion to the costs of achieving such marginal level of
reduction.'' Moreover, the inquiry does not require the Agency to
quantify benefits in monetary terms. See, e.g., American Iron and Steel
Institute v. EPA, 526 F. 2d 1027, 1051 (3rd Cir. 1975).
    In balancing costs against the effluent reduction, EPA considers
the volume and nature of expected discharges after application of BPT,
the general environmental effects of pollutants, and the cost and
economic impacts of the required level of pollution control. In past
effluent limitation guidelines, BPT cost-reasonableness comparisons
ranged from $0.26 to $41.44 per pound removed in year 2008 dollars.
This range is not inclusive of all categories regulated by BPT, but
nonetheless represents a very broad range of cost-reasonableness
values. About half of the cost-reasonableness values represented by
this range are less than $2.50 per pound (in 2001 dollars). In
developing guidelines, the Act does not require consideration of water
quality problems attributable to particular point sources, nor does it
require consideration of water quality improvements in particular
bodies of water. See American Frozen Foods Inst. v. Train, 539 F.2d
107, 117 (D.C. Cir. 1976); Weyerhaeuser Company v. Costle, 590 F. 2d
1011, 1036, 1041-44 (D.C. Cir. 1978).
2. Best Available Technology Economically Achievable (BAT)
    BAT effluent guidelines are applicable to toxic (priority) and
nonconventional pollutants. EPA has identified 65 pollutants and
classes of pollutants as toxic pollutants, of which 126 specific
substances have been designated priority toxic pollutants. 40 CFR
401.15 and 40 CFR part 423, Appendix A. In general, BAT represents the
best available performance of direct discharging facilities in the
subcategory or category. CWA section 304(b)(2)(A). The factors
considered in assessing BAT include the cost of achieving BAT effluent
reductions, the age of equipment and facilities involved, the processes
employed, engineering aspects of the control technology, potential
process changes, non-water quality environmental impacts (including
energy requirements), and such factors as the Administrator deems
appropriate. CWA section 304(b)(2). The Agency retains considerable
discretion in assigning the weight to be accorded to these factors.
Natural Resources Defense Council v. EPA, 863 F.2d 1420, 1426 (9th Cir.
1988). An additional statutory factor considered in setting BAT is
``economic achievability.'' EPA may determine the economic
achievability of an option on the basis of the total cost to the
subcategory and the overall effect of the rule on the industry's
financial health. The Agency may base BAT limitations upon effluent
reductions attainable through changes in a facility's processes and
operations. See Texas Oil & Gas Ass'n v. EPA, 161 F.3d 923, 928 (5th
Cir. 1998) (citing ``process changes'' as one factor EPA must consider
in determining BAT); see also, American Meat Institute v. EPA, 526 F.2d
442, 464 (7th Cir. 1975). As with BPT, where existing performance is
uniformly inadequate, EPA may base BAT upon technology transferred from
a different subcategory or from another category. See CPC International
Inc. v. Train, 515 F.2d 1032, 1048 (8th Cir. 1975) (established
criteria EPA must consider in determining whether technology from one
industry can be applied to another); see also, Tanners' Council of
America, Inc. v. Train, 540 F.2d 1188 (4th Cir. 1976). In addition,

the Agency may base BAT upon manufacturing process changes or internal
controls, even when these technologies are not common industry
practice. See American Frozen Foods Inst. v. Train, 539 F.2d 107, 132
(D.C. Cir. 1976).
3. Best Conventional Pollutant Control Technology (BCT)
    The 1977 amendments to the CWA required EPA to identify effluent
reduction levels for conventional pollutants associated with BCT
technology for discharges from existing point sources. BCT is not an
additional limitation, but replaces Best Available Technology (BAT) for
control of conventional pollutants. In addition to other factors
specified in CWA section 304(b)(4)(B), the Act requires that EPA
establish BCT limitations after consideration of a two-part ``cost-
reasonableness'' test. EPA explained its methodology for the
development of BCT limitations in July 1986 (51 FR 24974).
    Section 304(a)(4) designates the following as conventional
pollutants: Biochemical oxygen demand (BOD5), total suspended solids
(TSS), fecal coliform, pH, and any additional pollutants defined by the
Administrator as conventional. 40 CFR 401.16. The Administrator
designated oil and grease as an additional conventional pollutant on
July 30, 1979 (44 FR 44501).
4. New Source Performance Standards (NSPS)
    NSPS reflect effluent reductions that are achievable based on the
best available demonstrated control technology. New sources, as defined
in CWA section 306, have the opportunity to install the best and most
efficient production processes and wastewater treatment technologies.
As a result, NSPS should represent the greatest degree of effluent
reduction attainable through the application of the best available
demonstrated control technology for all pollutants (i.e., conventional,
nonconventional, and priority pollutants). In establishing NSPS, CWA
section 306 directs EPA to take into consideration the cost of
achieving the effluent reduction and any non-water quality
environmental impacts and energy requirements.
5. Pretreatment Standards
    The CWA also defines standards for indirect discharges, i.e.,
discharges into publicly owned treatment works (POTWs). These standards
are known as Pretreatment Standards for Existing Sources (PSES) and
Pretreatment Standards for New Sources (PSNS), and are promulgated
under CWA section 307(b). EPA has no data indicating that construction
sites typically discharge directly to POTWs. Therefore, EPA is not
proposing PSES or PSNS for the C&D category. EPA determined that the
majority of construction sites discharge either directly to waters of
the U.S. or through MS4s. In some urban areas, construction sites may
discharge to combined sewer systems (i.e., sewers carrying both
stormwater and domestic sewage through a single pipe) which lead to
POTWs. Sediment and turbidity, which are the primary pollutants
associated with construction site discharges, are susceptible to
treatment in POTWs, using technologies commonly employed such as
primary clarification. EPA has no evidence that construction site
discharges to POTWs would cause interference, pollutant pass-through or
sludge contamination.
6. EPA Authority to Promulgate Non-Numeric Effluent Limitations
    The regulatory options proposed today include non-numeric effluent
limitations that will control the discharge of pollutants from C&D
sites. It is well established that EPA has the authority to promulgate
non-numeric effluent limitations in addition to or in lieu of numeric
limits. The CWA does not mandate the use of numeric limitations only
and EPA's position finds support in the language of the CWA. The
definition of ``effluent limitation'' means ``any restriction * * * on
quantities, rates, and concentrations of chemical, physical,
biological, and other constituents * * *'' CWA section 502(11).
    Federal courts have recognized the CWA does not mandate that EPA
use numeric effluent limitations. In Citizens Coal Council v. U.S. EPA,
447 F3d 879, 895-96 (6th Cir. 2006), the Sixth Circuit, in upholding
EPA's use of non-numeric effluent limitations, agreed with EPA that it
derives authority under CWA sections 402(a), 304(b) and 502(11) to
incorporate non-numeric effluent limitations for conventional and non-
conventional pollutants. The Sixth Circuit further held as reasonable
the Agency position that CWA sections 304(b), 304(e) and 502(11), read
together, allow non-numeric effluent limitations to supplement CWA
section 304(b), or can stand as effluent limitations themselves. See
also, Waterkeeper Alliance, Inc. v. U.S. EPA, 399 F.3d 486, 496-97, 502
(2d Cir. 2005) (EPA use of non-numerical effluent limitations in the
form of best management practices are effluent limitations under the
CWA); Natural Res. Def. Council, Inc. v. EPA, 673 F.2d 400, 403 (D.C.
Cir. 1982) (``section 502(11) [of the CWA] defines 'effluent
limitation' as 'any restriction' on the amounts of pollutants
discharged, not just a numerical restriction.''); Natural Res. Def.
Council, Inc. v. Costle, 568 F.2d 1369 (D.C. Cir. 1977) (in determining
EPA did not have the authority to exclude a particular point source
from the NPDES program, the Court held ``when numerical effluent
limitations are infeasible, EPA may issue permits with conditions
designed to reduce the level of effluent discharges to acceptable
levels. This may well mean opting for a gross reduction in pollutant
discharge rather than fine-tuning suggested by numerical
limitations.'')
    EPA's NPDES regulations reflect EPA's long standing interpretation,
as supported by federal court decisions, that the CWA allows for non-
numeric effluent limitations. 40 CFR 122.44(k).
7. 2002 Construction and Development Proposal and Subsequent Litigation
    EPA identified the C&D industry in its CWA section 304(m) plan in
2000 as an industrial point source category for which EPA intended to
conduct rulemaking. 65 FR at 53,008 and 53,011 (August 31, 2000). On
June 24, 2002, EPA published a proposed rule that contained several
options for the control of stormwater discharges from construction
sites, including ELGs and NSPS. (67 FR 42644; June 24, 2002).
    On April 26, 2004, EPA determined that national effluent
limitations guidelines would not be the most effective way to control
discharges from construction sites, and instead chose to rely on the
range of existing programs, regulations, and initiatives that already
existed at the federal, state and local level. (69 FR 22472; April 26,
2004).
    On October 6, 2004, the Natural Resources Defense Council, Inc. and
additional plaintiffs filed a complaint in district court alleging that
EPA's decision not to promulgate ELGs and NSPSs for the C&D industry
violated a mandatory duty under the CWA. The district court, in NRDC v.
EPA, 437 F.Supp.2d 1137, 1139 (C.D. Cal. 2006), held that CWA section
304(m) imposes on EPA a mandatory duty to promulgate ELGs and NSPSs for
new industrial point source categories named in a CWA section 304(m)
plan. The district court enjoined EPA to propose ELGs and NSPSs for the
C&D industry by December 1, 2008 and to promulgate ELGs and NSPSs as
soon as practicable, but in no event later than December 1, 2009. On
appeal, the Ninth Circuit in NRDC v. EPA, 2008 WL 4253944 (9th Cir.
2008) affirmed the district court's

decision holding that ``* * * the CWA is unambiguous that the EPA must
promulgate ELGs and NSPSs for the point-source categories listed in a
plan pursuant to [section] 304(m) * * *'' The deadline to seek re-
hearing in the Ninth Circuit was November 3, 2008. The Agency requested
a 30-day extension of the re-hearing deadline, which was granted, thus
the new deadline for EPA to seek re-hearing is December 3, 2008.

IV. Scope of the Proposal

    EPA is proposing a regulation that would strengthen the existing
controls on discharges from construction activity by establishing
technology-based effluent limitations guidelines and new source
performance standards for the C&D point source category. This proposal,
if implemented, would significantly reduce the amount of sediment, TSS,
turbidity and other pollutants discharged from construction sites due
to construction activities. EPA estimates that today's proposed rule
would cost $1.9 billion dollars per year. These estimates do not
include costs for Alaska, Hawaii and the U.S. territories because EPA
lacked data on the amount of construction occurring in these areas.
However, EPA does expect that some construction sites in these areas
would incur compliance costs as a result of today's proposal. EPA
solicits data that can be used to estimate the number of acres of
construction activity that occurs annually in these areas.
    The proposed rule would establish a set of non-numeric effluent
limitations requiring dischargers to provide and maintain effective
erosion control measures, sediment control measures, and other
pollution prevention measures to minimize and control the discharge of
pollutants in stormwater and other wastewater from construction sites.
The rule would specify particular minimum BMPs to meet the effluent
limitations requiring effective erosion control and pollution
prevention.
    In addition, reflecting current requirements in the EPA CGP, sites
disturbing 10 or more acres at one time would be required to install a
sediment basin to contain and settle sediment from stormwater runoff.
The proposed rule would require minimum standards of design for
sediment basins; however, alternatives that control sediment discharges
in a manner equivalent to sediment basins would be authorized where
approved by the permitting authority.
    Finally, reflecting the BAT and NSPS levels of control, for certain
large sites located in areas of high rainfall energy and with soils
with significant clay content, discharges of stormwater from the site
would be required to meet a numeric effluent limit on the allowable
level of turbidity. The numeric turbidity limit is 13 nephelometric
turbidity units (NTUs). The turbidity limit is intended to remove fine-
grained and slowly settling or non-settleable particles contained in
stormwater. Particles such as clays and fine silts contained in
stormwater discharges from C&D sites typically cannot be effectively
removed by conventional stormwater BMPs (such as sediment basins and
sediment traps) that rely solely on settling unless sufficient
detention time or additives are implemented. The technology basis for
the turbidity limit is active treatment systems (ATS), which consists
of polymer-assisted clarification followed by filtration.
    In addition to this proposed option, EPA is specifically soliciting
comment on setting a turbidity limit in the range of 50 to 150 NTUs (or
some other number) based on passive treatment, instead of ATS. See
section IX.A.5.a of today's proposal for additional discussion of this
alternative approach.
    EPA considered several other regulatory approaches while developing
this proposed rule, such as specifying certain design criteria for
sediment basins, or using different site size, rainfall, or soil type
thresholds for determining which sites would be required to comply with
a turbidity limit. EPA also considered setting BAT and NSPS equal to
the proposed BPT level of control, based on non-numeric BMP-based
effluent limitations, as well as an expanded version of today's
proposed rule. EPA requests comment on these alternative regulatory
approaches. Details of the proposed rule and alternative approaches
considered are described in this notice, the Development Document,
Economic Analysis, and Environmental Assessment (see the Supporting
Documentation section of this notice) and additional documentation is
contained in the record.

V. Overview of the Construction and Development Industry and
Construction Activities

    The C&D point source category covers firms classified by the Census
Bureau into two North American Industry Classification System (NAICS)
codes.
     Construction of Buildings (NAICS 236) includes
residential, nonresidential, industrial, commercial and institutional
building construction.
     Heavy and Civil Engineering Construction (NAICS 237)
includes utility systems construction (water and sewer lines, oil and
gas pipelines, power and communication lines); land subdivision;
highway, street, and bridge construction; and other heavy and civil
engineering construction.

Other types of entities not included in this list could also be
regulated.
    A single construction project may involve many firms from both
subsectors. The number of firms involved and their financial and
operational relationships may vary greatly from project to project. In
typical construction projects, the firms identifying themselves as
``operators'' under a construction general permit are usually general
building contractors or developers. While the projects often engage the
services of specialty contractors such as excavation companies, these
specialty firms are typically subcontractors to the general building
contractor and are not separately identified as operators in stormwater
permits. Other classes of subcontractors such as carpentry, painting,
plumbing and electrical services typically do not apply for, nor
receive, NPDES permits. The types and numbers of firms in the
construction industry are described in more detail in the Development
Document and the Economic Analysis.
    Construction on any size parcel of land almost always calls for a
remodeling of the earth. Therefore, actual site construction typically
begins with site clearing and grading. Earthwork activities are
important in site preparation because they ensure that a sufficient
layer of organic material (ground cover and other vegetation,
especially roots) is removed. The size of the site, extent of water
present, the types of soils, topography and weather determine the types
of equipment that will be needed during site clearing and grading.
Material that will not be used on the site may be hauled away. Clearing
activities involve the movement of materials from one area of the site
to another or complete removal from the site. When grading a site,
builders typically take measures to ensure that new grades are as close
to the original grade as possible to reduce erosion and stormwater
runoff. Proper grade also ensures a flat surface for development and is
designed to attain proper drainage away from the constructed buildings.
A wide variety of equipment is often used during excavation and
grading. The type of equipment used generally depends on the functions
to be performed and on specific site conditions. Shaping and compacting
the earth is an important part of site preparation. Earthwork
activities might require that fill material be used on the site. In
such cases, the

fill must be spread in uniform, thick layers and compacted to a
specific density. An optimum moisture content must also be reached.
Graders and bulldozers are the most common earth-spreading machines,
and compaction is often accomplished with various types of rollers. If
rock is to be removed from the site, the contractor must first loosen
and break the rock into small pieces using various types of drilling
equipment or explosives. (Adapted from Peurifoy, Robert L. and
Oberlender, Garold D. (1989). Estimating Construction Costs (4th ed.).
New York: McGraw Hill Book Company.)
    Once materials have been excavated and removed and the ground has
been cleared and graded, the site is ready for construction of
buildings, roads, and/or other structures. During construction
activity, the disturbed land can remain exposed without vegetative
cover for a substantial period of time. Where the soil surface is
unprotected, soil particles and other pollutants are particularly
susceptible to erosion and may be easily washed away by rain or snow
melt and discharged from the site. Permittees typically use a
combination of erosion and sediment control measures designed to
prevent mobilization of the soil particles and capture of those
particles that do mobilize and become entrained in stormwater from the
C&D site. In most cases these control measures take the form of BMPs,
but in some cases construction sites actively treat a portion of the
discharge using filtration or other treatment technologies. Erosion and
sediment control measures are described further in the Development
Document.

VI. Summary of Data Collection Activities

    In developing today's proposal, EPA gathered and evaluated
technical and economic data from various sources. EPA also used data
collected previously to develop the 2002 proposed C&D rule and the 2004
withdrawal of the proposed rule.
    EPA used these data to estimate costs, pollutant loading
reductions, environmental benefits and economic impacts of various
regulatory options. This section summarizes EPA's data collection
efforts.

A. State Data

    EPA compiled and evaluated existing state program information about
the control of construction site stormwater. EPA collected data by
reviewing state construction general permits, Web sites, summary
references, state regulations, and erosion and sediment control design
and guidance manuals. A summary of criteria and standards for
construction site stormwater erosion and sediment control that are
implemented by states are presented in Appendix A of the Development
Document for this proposed rulemaking. EPA did not collect information
from counties or municipalities regarding current construction site
stormwater requirements. EPA relied on state-level requirements to
characterize requirements in all areas of the state. So, if county or
municipal requirements are more stringent than state-level requirements
for control of construction site stormwater discharges, EPA's baseline
estimates of costs and pollutant reductions would not reflect these
more stringent requirements currently in place. Therefore, certain
components of EPA's cost and loadings estimates for the regulatory
options may be overestimates. In addition, EPA did not account for
those sites that would already be required to meet a turbidity limit.
For example, some construction sites around the country are already
required to meet numeric effluent limits for turbidity that are
comparable to EPA's proposed turbidity limit. EPA has not accounted for
these sites in its analysis of costs and loading reductions, although
the number of these sites is likely to be only a small fraction of
construction sites nationwide.

B. National Land Cover Dataset (NLCD)

    The NLCD provides a national source of data on land cover. EPA used
these data to estimate the amount of land across the U.S. that was
converted to development (e.g., from forest or farmland to residential
communities), which in turn was used to estimate the amount of acreage
that may be subject to the requirements of the C&D rule.
    The Multi-Resolution Land Characteristics Consortium (MRLC) has
produced the NLCD datasets that created a 30-meter resolution land
cover data layer over the conterminous United States using remote
sensing data. There are approximately 24 billion data points from
remote sensing data that comprise the NLCD database. NLCD data is
publicly available for the years 1992 and 2001.
    Due to new developments in mapping methodology, new sources of
input data, and changes in the mapping legend for the 2001 National
Land Cover Database (NLCD 2001), direct comparison between NLCD 2001
and the 1992 National Land Cover Dataset (NLCD 1992) is difficult.
Thus, MRLC prepared the NLCD 1992/2001 Land Cover Change Product (see
http://www.mrlc.gov/change_detection.asp). The NLCD 1992/2001 Land
Cover Change Product was developed to offer more accurate direct change
analysis between the two products. This land cover change map and all
documents pertaining to it are considered ``provisional'' until a
formal accuracy assessment can be conducted. Detailed definitions and
discussion of the NLCD 1992/2001 Land Cover Change Product is
summarized in the Development Document.
    EPA estimated the annual number of acres of land converted to
development in the U.S. and used that estimate as a surrogate measure
of the acres of construction activities subject to national effluent
guidelines regulations, since no national database of the number and
size of construction activities exists. EPA used estimates of the
amount of construction activity occurring in each state based on NLCD
data as a basis for calculating state-level compliance costs. NLCD data
was also used to estimate the amount of construction activity occurring
in each of the watersheds in the U.S. based on the EPA Reach File
cataloging system (discussed below). Watershed level data (along with
other data sources) was used to estimate the quantity of construction
activities and the associated pollutant loads occurring in each
watershed and to link these loads to stream reaches for modeling of
water quality improvements and benefits estimates.

C. Enhanced River Reach File 1.2 (ERF1)

    EPA used the EPA Reach File 1.2 dataset (ERF1) to summarize land
cover change in drainage area units (or watersheds). ERF1 for the
Conterminous United States is a vector database of approximately
700,000 miles of streams and open waters in the conterminous United
States. ERF1 was prepared by EPA in 1982 from National Oceanographic
and Atmospheric Administration (NOAA) aeronautical charts having a
scale of 1:500,000. ERF1 contains 67,171 watersheds with a minimum size
of 247 acres (1 km\2\) and an average size of 30,182 acres (122 km\2\).
ERF1 serves as the foundation for SPARROW (Spatially Referenced
Regressions [of nutrient transport] on Watershed) modeling (see Section
XIV of this proposal for a discussion of SPARROW).

D. NPDES Notice of Intent (NOI) Data

    As stated above, when a discharger wishes to be authorized to
discharge under a general permit, it files a NOI to be covered under
the general permit. EPA used NOI data to estimate the distribution of
construction activity by site size and development type. Using NOI
data, EPA broadly characterized the

construction industry into three land use types (residential
construction, non-residential construction and road/highway
construction). Differentiation of construction activities by site size
and project type was also done for EPA's technical and economic
analyses. EPA used NOI data from approximately 138,000 permit
applications, containing data from 38 States for construction
activities occurring primarily between the mid-1990s and 2006.
Depending on the state, the number of NOI records available ranged from
fewer than 10 to more than 10,000. The data are available either from a
database of permits processed directly by EPA (referred to as the EPA
NOI database) or from per-state databases obtained independently.

E. Soils Data

    EPA used the State Soil Geographic (STATSGO) data compiled by Penn
State University (http://www.soilinfo.psu.edu/) in order to estimate
variation in soil types nationwide. The variation in soil types found
within the United States is a significant factor in estimating sediment
discharges, pollutant load reductions, and stormwater pollution
prevention costs for construction sites. EPA used the STATSGO soils
data in support of the loadings and removal estimates for this
proposal. EPA used the Revised Universal Soil Loss Equation (RUSLE) in
combination with the soils data to determine soil erosion rates from
model construction sites in different areas of the country. EPA used
these estimates, in combination with estimates of pollutant removal
efficiencies for the various technologies evaluated, to estimate
sediment discharges from C&D sites under baseline conditions and under
each regulatory option evaluated. Although EPA was not able to find a
national database of measured sediment concentrations in treated and
untreated construction site stormwater runoff, EPA did find monitoring
data from several states and compared these measured concentrations to
the estimate concentration based on RUSLE. A discussion of this
comparison is provided below in section IX. F. Additional details on
the soil data collected can be found in the Development Document.

F. NOAA Rainfall Data

    Variations in rainfall depth and intensity are also important
factors in determining erosion rates, sediment discharges, pollutant
load reductions and control technology costs for construction sites. In
order to account for variations in rainfall patterns, EPA collected
rainfall data for one indicator city within each of the 48 conterminous
states. Data for each of these indicator cities were used as point
estimates for estimating rainfall depths and intensities for
construction activities for the entire state. A major urban area was
chosen as the indicator city in each state; which in most cases was the
capital city.
    For each indicator city, precipitation data was gathered and
analyzed using the National Oceanic and Atmospheric Administration
(NOAA) National Weather Service (NWS) Precipitation Frequency Data
Server (PFDS), NOAA Atlas 14, a series of maps presented in older NWS
publications, and NOAA Atlas 2 (Precipitation Frequency Atlas of the
Western United States (1973)). Alaska and Hawaii, as well as the U.S.
territories, were not included in this analysis because EPA lacked
sufficient data on the annual amount of construction occurring in these
areas. More details on EPA's analysis can be found in the Development
Document.

G. Parameter Elevation Regressions on Independent Slopes Model (PRISM)

    PRISM is a climate mapping system that was used to estimate the
annual acres that would be subject to the regulatory options given
various annual rainfall cutoffs. Using PRISM GIS layers of average
annual precipitation along with RF1-level estimates of annual acres of
new construction, EPA was able to estimate acres that would be subject
to various regulatory options given various average annual
precipitation cutoffs.

H. Revised Universal Soil Loss Equation (RUSLE) R Factors

    EPA used maps of rainfall-runoff erosivity factors (or R factors)
contained in the RUSLE documentation. These maps, in GIS form, along
with RF1-level estimates of annual acres of new construction, were used
to estimate acres that would be subject to regulations given various R
factor values.

I. Economic Data

    EPA utilized various economic data sources in developing today's
proposal. The primary data source is the 2002 Economic Census,
conducted every five years by the U.S. Census Bureau. The U.S. Small
Business Administration (SBA) and Census Bureau also provide important
information in Statistics of U.S. Business (SUSB). SUSB provides firm-
level data that is particularly important for the firm and industry
impact assessment and for the small entity analysis. An important
source of project level data is Reed Construction, a commercial
construction industry data service that collects and reports
information on multifamily, commercial/institutional, and industrial
construction projects undertaken nationally. EPA assigned baseline
financial characteristics--balance sheet, income statement, and metrics
of financial performance and condition--to each of the model firms as
defined by NAICS sector and revenue size range, from financial
statement information reported by Risk Management Association's (RMA)
publication, Annual Statement Studies. The Census Bureau's 2006
American Community Survey (ACS) was used to characterize new home
prices and lot sizes (2006 was chosen because it is the most recent
year for which the required Metropolitan Statistical Area (MSA)-level
data are available from the Census).

VII. Characteristics of Discharges From Construction Activity

    The nature of construction activity is that it changes, often
significantly, many elements of the natural environment. Typically,
construction activities involve clearing the land of vegetation,
digging, earth moving and grading, followed by the active construction
period when the affected land is usually left denuded and the soil
compacted, often leading to an increase in the peak discharge rate and
the total volume of stormwater discharged and higher rates of erosion.
During the land disturbance period, affected land is generally exposed
after removal of grass, rocks, pavement and other protective ground
covers. Where the soil surface is unprotected, soil and sand particles
may be easily picked up by wind and/or washed away by rain or snow
melt. Typically, the water carrying these particles eventually reaches
a water body.
    Discharges from construction activity have been documented to
increase the loadings of several pollutants in the receiving
waterbodies. The most prominent and most widespread pollutant
discharged from C&D sites is sediment. The level of sediment is often
identified through the measurement of the pollutants' turbidity,
suspended solids, total suspended solids (TSS), suspended sediment
concentration (SSC), and/or settleable solids. CWA section 304(a)(4)
identified suspended solids as a conventional pollutant and in 1978 EPA
defined ``suspended solids'' as ``total suspended solids (non-
filterable) (TSS)'' and stated that TSS ``is a laboratory measure of
the organic and inorganic particulate matter in wastewater which does
not pass through a specified glass filter disk.'' See 40 CFR

401.16; 43 FR 32857, 32858 (July 28, 1978). Turbidity and settleable
solids are non-conventional pollutants. See CWA section 301(b)(2)(F);
304(a)(4); Rybachek v. EPA, 904 F.2d 1276, 1291-92 (9th Cir. 1990). The
Agency defined ``turbidity'' as ``an expression of the optical property
that causes light to be scattered and absorbed rather than transmitted
with no change in direction of flux level through the sample * * *
caused by suspended and colloidal matter such as clay, silt, finely
divided organic and inorganic matter and plankton and other microscopic
organisms.'' 40 CFR 136.3; 72 FR 11200, 11247 (March 12, 2007). (See
Section IX for a discussion of why EPA proposes turbidity as the
desired pollutant to control in determining the appropriate
technology).
    Stormwater discharges can have highly variable levels of
pollutants. Available data show that turbidity levels range from as low
as 10-50 NTU to several thousand NTU. When the denuded and exposed
areas contain nutrients, pathogens, metals or organic compounds, these
other pollutants are likely to be carried at increased rates (relative
to discharges from undisturbed areas) to surrounding waterbodies via
stormwater and other discharges (e.g., inadequately controlled
construction equipment wash water). Discharges of these pollutants from
construction activities can cause changes in the physical
characteristics of waterbodies, such as pH, water temperature, or
stream flow velocity, as well as changes in biological characteristics
such as aquatic species abundance and composition.
    Actions taken to stabilize disturbed areas of the C&D site can
include seeding to restore vegetative cover. When fertilizers or
herbicides are applied to these areas, a portion of the chemicals
applied may become entrained in stormwater and will be discharged from
the site. Fertilizers contribute nutrients such as nitrogen and
phosphorus to the wastestream.
    Discharges from construction activity are expected to contain
varying concentrations of metals, some of which may be contributed by
equipment used onsite for grading and other construction activities.
Metals are also naturally present in soils and, by removing vegetative
cover and increasing erosion and sediment loss, there will likely be an
increase in the amount of metals discharged from the C&D site. Metals
present as a contaminant or additive in fertilizers and other soil
amendments may serve as another source of pollutants in the stormwater
discharge.
    Fuels and lubricants are maintained onsite to refuel and maintain
vehicles and equipment used during construction activities. These
products, should they come in contact with stormwater and other site
discharges, would contribute toxic organic pollutants. Pathogenic
pollutants can be present in stormwater that comes into contact with
sanitary wastes where portable sanitation facilities are poorly located
or maintained.
    The environmental impacts associated with discharges from
construction sites are described in section XIV.

VIII. Description of Available Technologies

A. Introduction

    As described in Section VII, construction activity results in the
discharge of pollutants to waters of the U.S. These discharges can be
controlled by applying site design techniques that preserve or avoid
areas prone to erosion and through the effective use of a combination
of erosion and sediment control measures. Construction activities
should be managed to reduce erosion and retain sediment on the C&D
site. Erosion and sedimentation are two separate processes and the
practices to control them differ. Erosion is the process of wearing
away of the land surface by water, wind, ice, gravity, or other
geologic agents. Sedimentation is the deposition of soil particles,
both mineral and organic, which have been transported by water, wind,
air, gravity or ice (adapted from North Carolina Erosion and Sediment
Control Planning and Design Manual, September 1, 1988).
    Erosion control measures are intended to minimize dislodging and
mobilizing of sediment particles. Sediment control measures are
controls that serve to capture particles that have mobilized and are
entrained in stormwater, with the objective of removing sediment and
other pollutants from the stormwater discharge. An overview of
available technologies and practices is presented below; see the
Development Document for more complete descriptions. Many states and
local governments and other entities have also published detailed
manuals for erosion and sediment control measures, and other stormwater
management practices.

B. Erosion Control Measures

    The use of erosion control measures is widely recognized as the
most important means of limiting soil detachment and mobilization of
sediment. The controls described in this notice are designed to reduce
mobilization of soil particles and minimize the amount of sediment and
other pollutants entrained in discharges from construction activity.
Erosion can be minimized by a variety of practices. The selection of
control measures that will be most effective for a particular site is
dictated by site-specific conditions (e.g., topography, soil type,
rainfall patterns). The main strategies used to reduce erosion include
minimizing the time bare soil is exposed, preventing the detachment of
soil and reducing the mobilization and transportation of soil particles
off-site.
    Decreasing the amount of land disturbed can significantly reduce
sediment detachment and mobilization, as well as overall erosion and
sediment control costs. This can be accomplished by reducing the
overall area of disturbed land or by phasing construction so that only
a portion of the site is disturbed at a time. Another effective
approach is to schedule clearing and grading events to reduce the
probability that bare soils will be exposed to rainfall.
    Managing stormwater flows on the site can be highly effective at
reducing erosion. Typical practices include actively managing off-site
and on-site stormwater using diversion berms, conveyance channels and
slope drains to avoid stormwater contact with disturbed areas. In
addition, stormwater should be managed using energy dissipation
approaches to prevent high runoff velocities and concentrated flows
that are erosive. Vegetative filter strips are often considered as
sediment controls, but they can also be quite effective at dissipating
energy and reducing the velocity (and thus erosive power) of
stormwater.
    After land has been disturbed and construction activity has ceased
on any portion of the site, exposed soils should be covered and
stabilized immediately. Vegetative stabilization using annual grasses
is a common practice used to control erosion. Polymers, physical
barriers such as geotextiles, straw, rolled erosion control products
and mulch are other common methods of controlling erosion. These
materials and methods are intended to reduce erosion where soil
particles can be initially dislodged on a C&D site, either from
rainfall, snow melt or up-slope runoff.
    The effectiveness of erosion control measures is dependent on
periodic inspection and identification and correction of deficiencies
(e.g., after each storm event). Erosion control measures alone will not
eliminate the mobilization of soil particles and such controls must be
used in conjunction with sediment control measures.

C. Sediment Control Measures

    Despite the proper use of erosion control measures, some sediment
detachment and movement is inevitable. Sediment control measures are
used to control and trap sediment that is entrained in stormwater
runoff. Typical sediment controls include perimeter controls such as
silt fences constructed with filter fabric, straw bale dikes, berms or
swales. Trapping devices such as sediment traps and basins and inlet
protectors are examples of in-line sediment controls. Sediment traps
and basins are commonly used approaches for settling out sediment
eroded from small and large disturbed areas. Their performance can be
enhanced using baffles and skimmers and active treatment processes such
as electrocoagulation, filtration, and chemically enhanced settling
(e.g., polymer addition).
    Active treatment systems are typically used in conjunction with
other sediment controls to improve pollutant removals, especially to
improve removals of fine-grained and slowly settling or non-settleable
particles and turbidity contained in stormwater. Unless sufficient
detention time is provided or additives are implemented, particles such
as clays and fine silts contained in stormwater discharges from
construction sites typically cannot be effectively removed by
conventional stormwater BMPs (such as sediment basins and sediment
traps) that rely solely on gravity settling. EPA has identified several
demonstrated technologies capable of achieving significant reductions
of these particles. Based on the information in the record,
electrocoagulation, polymer clarification, and chitosan-enhanced
filtration treatment technologies are demonstrated as being capable of
achieving low levels of turbidity in stormwater discharges.
    The active treatment systems EPA has evaluated operate by
destabilizing the suspended particles by various mechanisms,
aggregating them into larger particles that are easier to remove
through settling or filtering. In addition to physical characteristics
(e.g., particle surface area, density) that impede timely settling by
gravity, these small particles (often clay particles) typically are
substantially influenced by net electrical repulsive forces at particle
surfaces that prevent the particles from joining together. Coagulation
refers to the process whereby these repulsive electrical forces are
reduced, allowing particles to come into contact with one another.
Flocculation refers to the agglomeration of the destabilized particles
by joining and bridging to form larger particles. Following
coagulation/flocculation, the densified floc can more easily and
effectively be removed via gravitational settling or media filtration
(e.g., sand, gravel, bag, or cartridge filters).
    Electrocoagulation treatment uses an electrical field to disturb
the natural electrical charges of the colloidal particles suspended in
stormwater, enabling the particles to coagulate and flocculate, and
facilitating gravity settling. This settling may be followed by
filtration prior to discharge of the stormwater.
    Polymer clarification can operate as a batch process whereby a
polymer is added to stormwater contained in a basin. The polymer causes
clays and other fine particles to flocculate and gravity settle. Once
the turbidity reaches the necessary value and other permit requirements
are met, the stormwater is discharged from the basin. Polymer
clarification can also be used in flow-through systems. In this
application, liquid polymer is injected into the influent to the
sediment basin or gel or solid polymer is added by placing polymer-
filled socks or ``floc logs'' in channels or pipes carrying sediment-
laded runoff into the basin. Stormwater flowing over the socks or logs
dissolves the solid polymer, and turbulence at the basin inflow point
facilitates mixing and aids in the coagulation/flocculation process.
    Chitosan-enhanced filtration is a process that adds a polymer (in
this instance, a polymer produced from the chitin in crab shells) to
the stormwater to promote flocculation. The flocculated stormwater is
then passed through one or more filtration steps and, if permit
conditions are met, can be discharged.
    These active treatment systems are often equipped with automated
instrumentation to monitor stormwater quality, flow rate, and dosage
control for both influent and effluent flows.
    It has been suggested that, while operating active treatment
systems that use polymers to reduce the turbidity of stormwater,
construction site dischargers may overuse polymers and, in doing so,
introduce toxicity or cause other adverse effects. EPA believes toxic
effects from discharges treated to meet a turbidity limit should not be
occurring and such events would be indicative of a poorly operated
treatment system. Polymers are widely used at a variety of wastewater
treatment systems and facilities throughout the country, and EPA is not
aware of any studies indicating that polymer addition to treat
stormwater from construction sites using ATS has been found to pose a
significant risk to water quality at those facilities. There are ample
regulatory (i.e., enforcement actions) and financial (e.g., chemical
costs) disincentives for dischargers to willfully overuse polymers in
their treatment systems. In addition, vendors have indicated that
dosages of polymers are carefully metered in ATS systems. Upon closer
review of the matter, it appears that this concern has been raised due
to anecdotal suggestions, rather than documented evidence of actual
discharge events causing toxic effects. To date, EPA has not identified
any documented cases where the use of a polymer to treat C&D stormwater
discharges caused an adverse effect in the receiving waters. Also,
Washington and other States have researched toxicity of some polymers
and established a sound basis for testing and significant controls on
dosage and usage. For example, Washington State has established
protocols for residual chemical and toxicity testing for ATS systems
and has required vendors to receive state approval. However,
California, in a draft permit fact sheet describing chemical treatment,
states the following:

    ``These systems can be very effective in reducing the sediment
in storm water runoff, but the systems that use additives/polymers
to enhance sedimentation also pose a potential risk to water quality
(e.g., operational failure, equipment failure, additive/polymer
release, etc.). We are concerned about the potential acute and
chronic impacts that the polymers and other chemical additives may
have on fish and aquatic organisms if released in sufficient
quantities or concentrations. In addition to anecdotal evidence of
polymer releases causing aquatic toxicity in California, the
literature supports this concern. For example, cationic polymers
have been shown to bind with the negatively charged gills of fish,
resulting in mechanical suffocation. Due to potential toxicity
impacts, which may be caused by the release of additives/polymers
into receiving waters, residual polymer monitoring and toxicity
requirements have been established in this General Permit for
discharges from construction sites that utilize an ATS in order to
protect receiving water quality and beneficial uses.'' (see DCN
41137).

    Therefore, EPA recognizes the merits of ensuring that chemical
additives are properly used. EPA solicits information and data that
quantify the number of instances where overuse of polymers occurred,
the circumstances resulting in such overuse, and the actual or
potential environmental impacts associated with such events. In
addition, EPA solicits comments on the need for approaches (either
voluntary or regulatory) to prevent or minimize the potential for such
instances and the need for EPA to

develop guidance on use of polymers at construction sites.
    More detailed descriptions of sediment and erosion control measures
can be found in the Development Document.

D. Other Construction and Development Site Management Practices

    Construction activity generates a variety of wastes and wastewater,
including concrete truck rinsate, municipal solid waste (MSW), trash,
and other pollutants. Construction materials and chemicals should be
handled, stored and disposed of properly to avoid contamination of
runoff. Dischargers utilize various practices to manage these wastes
and minimize discharges to surface waters, including:
     Protecting construction materials, chemicals and fuels and
lubricants from exposure to rainfall;
     Limiting exposure of freshly placed concrete to rainfall;
     Segregating stormwater and other wastewaters from fuels,
lubricants, sanitary wastes, and chemicals such as fertilizers,
pesticides and herbicides;
     Neat and orderly storage of chemicals, pesticides,
fertilizers, and fuels that are being stored on the site;
     Prompt collection and management of trash and sanitary
waste;
     Prompt cleanup of spills of liquid or dry materials.

IX. Development of Effluent Limitations Guidelines and Standards

A. Description of the Regulatory Options Considered

    In developing today's proposal, EPA evaluated several different
options for reducing pollutant discharges from construction activity.
The options evaluated by EPA are intended to control the discharge of
sediment, turbidity and other pollutants in stormwater and other
wastewater from C&D sites. Construction activity typically involves
clearing, grading and excavating of land areas. Prior to construction,
these land areas may have been agricultural, forested or other
undeveloped lands. Construction can also occur as redevelopment of
existing rural or urban areas, or infill development on open space
within existing developed areas. During the C&D process, vegetation or
surface cover is typically removed and underlying soils become more
susceptible to detachment by rainfall and erosion by stormwater runoff.
Soil is often compacted by construction equipment, reducing the
infiltration capacity of underlying soils and increasing stormwater
discharge rates. Sediments and other pollutants contained in stormwater
can and often are transported off-site and discharged from construction
sites. Today's proposal provides regulatory tools to improve erosion
and sediment control measures and pollution prevention measures on C&D
sites to minimize and control stormwater and other discharges from
construction activity.
    Certain limitations being proposed today are common to each
regulatory option. These common requirements consist of a set of non-
numeric effluent limitations that require dischargers to provide and
maintain effective erosion control measures, sediment control measures,
and other pollution prevention measures to minimize the discharge of
pollutants in stormwater and other wastewater from construction sites.
These non-numeric effluent limitations included in each regulatory
option are described in Section IX.B below.

B. Effluent Limitations Included in All Regulatory Options

    EPA's preferred approach is twofold: First, prevent the discharges
of sediment and other pollutants from occurring through the use of
effective site-specific planning, erosion control measures and
pollution prevention measures; and second, control discharges that do
occur through the use of effective sediment control measures. Under
each regulatory option, dischargers would be required to meet non-
numeric effluent limitations requiring them to minimize and control
discharges from the site by providing and maintaining effective erosion
and sediment control measures and pollution prevention measures.
    Dischargers would be required to prevent soil erosion and minimize
the discharge of sediment from all areas of the site by providing and
maintaining effective erosion control measures. Erosion controls are
considered effective when bare soil is uniformly and evenly covered
with vegetation or other suitable materials, stormwater is controlled
so that rills and gullies are not visible, and channels and streambanks
are not eroding. Dischargers would be required to provide and maintain
recognized and accepted erosion control measures, including stabilizing
disturbed soils immediately after clearing, grading, or excavating
activities have permanently or temporarily ceased (i.e., when such
activities have been stopped on a portion of the site and will not
resume for a period exceeding 14 calendar days). In addition,
dischargers would be required to minimize the amount of soil exposed
and control stormwater within the site to prevent soil erosion by using
effective erosion control measures. Stormwater discharges leaving the
site would also need to be controlled to prevent channel and streambank
erosion and erosion at outlets.
    The following list of principles and practices are generally
recognized and accepted as effective erosion controls and would be
provided in the rule to help guide the selection, design, and
implementation of control measures to meet the effluent limitations on
individual construction sites.
     Preserve topsoil and natural vegetation.
     Minimize soil compaction.
     Sequence or phase construction activities to minimize the
areas disturbed at any one time.
     Stabilize disturbed areas using temporary or permanent
vegetation, and controls such as mulch, geotextiles, or sod.
     Minimize the disturbance of steep slopes, and where such
slopes are disturbed implement erosion controls designed to control
soil erosion on slopes.
     Establish and maintain natural buffers around surface
waters.
     Minimize the construction of stream crossings.
     Divert stormwater that may run onto the site away from any
disturbed areas of the site.
    Dischargers would also be required to meet non-numeric effluent
limits requiring that they provide and maintain effective sediment
controls to minimize the discharge of sediment and other pollutants
from C&D sites. Sediment control measures implemented at the site would
include, at a minimum, the following:
     Establishing perimeter controls for any portion of the
down-slope and side-slope perimeter where stormwater will be discharged
from disturbed areas of the site.
     Establishing and using stabilized construction entrances
and exits that control sediment discharges from the site. Ensuring that
vehicles entering and exiting the site use such access points to
prevent tracking of sediment onto roads or other areas that convey
sediment to surface waters. Removing any sediment or other pollutants,
including construction materials, from paved surfaces daily. Washing
sediment or other pollutants off paved surfaces into storm drains would
be prohibited.
     Establishing and using controls and practices to minimize
the introduction of sediment and other pollutants to storm drain inlets
that receive stormwater discharges from the site.

     Controlling sediment and other contaminants from
dewatering activities. Discharges of dewatering wastes are prohibited
unless treated in a sediment basin or similar control measure.
    Each regulatory option includes pollution prevention measures that
would minimize or prohibit the discharge of pollutants from a variety
of sources and activities at C&D sites. Each option would prohibit
discharges of construction wastes, trash, sanitary wastes, and
wastewater from washout of concrete, paint, and other such materials.
The regulatory options would also prohibit the discharge of fuels,
oils, and other materials used in vehicle and equipment operation and
maintenance. The discharge of wastewater from washing vehicles and
equipment where soaps or solvents are used would be prohibited. The
discharge of pollutants resulting from the washing of equipment and
vehicles using only water would also be prohibited, unless wash waters
were treated in a sediment basin or alternative control that provides
equivalent or better treatment. Dischargers would be required to
implement measures to minimize the exposure of stormwater to building
materials, landscape materials, fertilizers, pesticides, herbicides,
detergents, and other liquid or dry products. In addition, dischargers
would be required to implement appropriate spill prevention and
response procedures for these materials.

C. Options for BPT, BCT, BAT and NSPS

    EPA considered the following three regulatory options for today's
proposal.
     Option 1
    Each C&D site subject to the rule would be required to implement
the limitations described above in Section IX.B. In addition, certain
larger sites would be required to install and maintain sediment basins
or equivalent sediment controls. Specifically, for portions of sites
that drain to one location and will have 10 or more acres disturbed at
one time, dischargers would be required to install a sediment basin to
control and treat the stormwater discharges. The proposed rule would
impose minimum standards of design and performance for sediment basins.
The basin would be required to provide storage for a calculated volume
of stormwater (called the water storage volume) from a 2-year, 24-hour
storm from each disturbed acre drained plus a sediment storage volume
of at least an additional 1,000 cubic feet, until final stabilization
of the disturbed area. Alternatively, a sediment basin providing a
water storage volume of 3,600 cubic feet per acre drained plus the
sediment storage volume would be required. To ensure adequate retention
time to facilitate settling of sediment particles, the proposed rule
would require that the effective length of the basin must be at least
four times the width of the basin and that the water storage volume be
designed to drain over a period of at least 72 hours using a surface
outlet (such as a skimmer), unless otherwise designated by the
permitting authority. The size of the basin that would be required is
based on the size of the drainage area that will have vegetation
removed and soils disturbed (i.e., if the total drainage area is 15
acres, but only 13 acres of this area will have vegetation removed and
soils disturbed during the course of the project and the remaining 2
acres will remain vegetated and stormwater is directed around both the
disturbed area and the sediment basin, then the storage volume can be
sized based on 13 acres).
    In addition, the design of the sediment basin would be required to
address site-specific factors such as amount, frequency, intensity and
duration of stormwater runoff; soil types; and other factors affecting
pollutant removal efficacy. For example, particle settling
characteristics, and thus pollutant removal efficacy, can be affected
by physical parameters of the basin such as inlet and outlet
velocities, basin surface area, and basin depth and volume necessary to
provide sufficient storage for sediment load and stormwater runoff.
Effective erosion and sediment controls are generally recognized as
including actions to divert stormwater away from disturbed areas of the
site, so that sediment erosion is reduced and sediment controls, such
as basins, are not overwhelmed by stormwater volumes.
    To minimize carryover and discharge of suspended particles from the
sediment basin, the basins would be required to incorporate an outlet
device designed to remove water from the top of the water column in
order to minimize the amount of sediment and other pollutants entrained
in the discharge. This can be accomplished by using technologies such
as a siphoning outlet, surface skimmer or floating weir.
    Recognizing that there may be impediments to using sediment basins
in some instances or that alternative approaches may provide better
controls depending on site-specific conditions, the proposed rule would
authorize dischargers to use alternative controls equivalent to
sediment basins where approved by the permitting authority.
    EPA encourages dischargers to use improved sediment basin designs
that incorporate features such as baffles and to increase the length to
width ratio of the basin to maximize detention time and settling. The
use of these practices may significantly improve the performance of
sediment basins in certain cases. The North Carolina Department of
Transportation (NCDOT) has developed draft specifications for baffles
in sediment basins (see DCN 43083). EPA solicits comments on whether
porous baffles, as described in the draft NCDOT specifications, should
be minimum requirements for all sediment basins nationwide. EPA also
requests comments on the costs and effectiveness of baffles used in
sediment basins, either alone or in combination with skimmers and
polymer addition. EPA also solicits comments on the detention time
requirements for sediment basins contained in today's proposal, and
whether the proposed rule should include other specific detention time,
overflow rate or other design or performance requirements for sediment
basins. EPA also solicits comments on whether the regulation should
require that sediment basins be designed to remove a specified particle
size. EPA also requests comments on whether sediment basin designs
should be required to address downstream channel erosion by requiring
peak or discharge rates to match predevelopment conditions, and for
what storm events such a standard should apply.
    Option 1 is estimated to cost approximately $132 million per year
(2008 $), not including costs for Alaska, Hawaii and the U.S.
territories, and reduce discharges of pollutants by 670 million pounds
annually. Monetized benefits of Option 1 are estimated to be $18
million per year. The cost estimates for Option 1 only include costs
for larger sediment basins in those states whose sizing requirements
are less stringent than those contained in the proposal. These cost
estimates do not include any additional costs for implementing skimmers
or the additional volume for sediment storage. EPA assumed that these
costs would not impact sediment basin costs significantly. Skimmers can
be purchased from commercial suppliers, or fabricated on-site. Also not
included are costs for deep ripping and decompaction of soils, and
several other required BMPs that are not currently part of the CGP or
most state permits. EPA solicits comments on the cost assumptions of
Option 1. The efficacy of Option 1 (percent of raw stormwater

sediment load removed) may be underestimated because only the basins
are modeled in the loading analysis. Removals due to other on-site BMPs
have not been modeled or included in the analysis.
    While developing and evaluating Option 1, EPA considered several
possible variations for sediment basin requirements. One approach would
have eliminated flexibility for dischargers to use a 3600 cf/acre basin
in lieu of the 2-year, 24-hour basin. In effect, all sites required to
install a sediment basin under Option 1 would have been required to
construct a basin sized to treat runoff from the 2-year, 24-hour storm
(or use equivalent control measures). EPA estimated that this variation
of Option 1 would cost approximately $1.09 billion per year. EPA also
considered an approach that, in addition to specifying a particular
size of basin, would require that the sediment basin be sized and
constructed to enable settling of a specified-size particle--e.g., 10-
micron particles. This approach would be a design standard rather than
a numeric limitation on the sediment basin effluent. For example, the
California Stormwater Quality Association Construction Handbook (see
DCN 43017) contains an example of designing a sediment basin to remove
a specified particle size standard based on wet sieve analysis for the
10 micron particle for a 10-year, 6-hour storm event. EPA estimates,
using this approach, that sediment basins required to remove particles
greater than 10 microns nationwide would cost approximately $1.7
billion per year. More information about these potential sediment basin
approaches is presented in the Development Document. EPA solicits
comment on whether Option 1 or other variations described here would be
appropriate regulatory approaches and, if so, why, based on the
statutory requirements of CWA section 304, they should be considered to
represent BPT, BCT, BAT, or NSPS level of control for this industry.
     Option 2
    The requirements that would be established under Option 2
incorporate all of the Option 1 requirements. In addition, a numeric
limit on turbidity of stormwater discharges would apply to sites that
meet certain criteria for size of the site, average clay content of the
soil (with clay content being defined as soil particles less than 2
microns in diameter), and rainfall erosivity factor (``R factor'') as
defined by the Revised Universal Soil Loss Equation (see Predicting
Soil Erosion by Water: A Guide to Conservation Planning With the
Revised Universal Soil Loss Equation (RUSLE), United States Department
of Agriculture, Agriculture Handbook Number 703, January 1997). Option
2 would establish a numeric effluent limit on the turbidity of
stormwater discharges for any site that meets all three of the
following criteria: (1) Average soil clay content of more than 10
percent; (2) annual R factor of 50 or more; and (3) has a size of 30 or
more acres. The numeric turbidity standard would apply to discharges
produced from rainfall events up to the local 2-year, 24-hour storm.
Any volume in excess of the 2-year, 24-hour storm would be exempt from
the turbidity standard. The turbidity limitation would apply to these
sites in addition to the Option 1 requirements (i.e., such sites would
also be required to implement the non-numeric erosion and sediment
control measures described under Option 1). Under Option 2, dischargers
would be required to monitor stormwater discharges for turbidity, which
can be done either by using automated instrumentation or with a
portable, hand-held turbidimeter or similar device. Sites with a common
drainage location that serves an area with 10 or more acres of land
disturbed land at one time that are not required to meet the turbidity
requirement, either because the total size of the site is less than 30
acres, the R factor is less than 50 or the average clay content of
soils is less than 10 percent, would be required to install sediment
basins as described under Option 1. Site size for sites subject to the
proposed turbidity limit is based on the total size of the site, not
the amount of disturbed acres or some other subset of the site. Any
site which is 30 acres or larger regardless of how much of the site
will be disturbed would be subject to the turbidity limit if they also
meet the R factor and soil clay content thresholds.
    By considering the construction site's soil clay content, this
option takes into account the pollutant reductions that are achievable
using the erosion control measures and traditional sediment control
measures (i.e., those other than active treatment systems) included in
the proposed rule. These more traditional approaches to controlling
stormwater discharges can be very effective in soils with low clay
content where the entrained sediment is amenable to gravity settling.
However, as the amount of clay in the soil rises, gravity settling
processes are less effective and processes to enhance the removal of
pollutants from stormwater are necessary. By applying the proposed
turbidity limit in Option 2 to sites with 10% or more clay content, the
proposed rule would achieve significant reductions of the slowly
settling or non-settleable particles and turbidity contained in
stormwater. In order to remove these fine-grained particles from
stormwater discharges, active treatment technologies, such as those
described in Section VIII, typically would need to be employed. The
information in the record shows that these systems can achieve low
levels of turbidity in the stormwater discharges.
    While it is impossible to predict the weather several months in
advance of construction, for many areas of the country, there are
definite optimal periods for conducting construction activities in
order to limit soil erosion, such as a dry season when rain tends to
fall less frequently and with less force. When feasible, this is the
time to disturb the earth, so that the site is stabilized by the time
the seasonal wet weather returns. The R factor is intended to reflect
consideration of the amount and intensity of precipitation expected
during the time the earth will be exposed.
    The method for determining a site's R factor is based on the
Universal Soil Loss Equation (USLE) developed by the U.S. Department of
Agriculture (USDA) in the 1950s to help farmers conserve topsoil. The
USLE has been updated to the Revised USLE (RUSLE). Using a computer
model supported by decades worth of rainfall data, USDA established
estimates of rainfall erosivity factors (R) for locations throughout
the country. These R factors are used as surrogate measures of the
impact that rainfall has on erosion from a particular site. The R
factor represents the driving force for erosion, taking into
consideration total rainfall, intensity and seasonal distribution of
the rain. Isoerodent maps depicting the R factor in various parts of
the country have been created by USDA and are included in Chapter 2 of
Agriculture Handbook Number 703.
    While developing and evaluating Option 2, EPA considered several
possible variations for the applicability of a limitation on turbidity
of stormwater discharges. One approach would replace the R factor
criteria with one based on total annual rainfall for the site location.
Under this approach, EPA preliminarily considered values of 20 inches
and 40 inches of total annual rainfall. EPA considers the R factor
approach better than total annual rainfall at addressing stormwater
discharges because the R factor captures both rainfall energy (a
function of the volume of rainfall and runoff) and intensity (which has
direct bearing on the erosive power of a rainfall event). EPA has
structured the regulatory

option accordingly. However, since R factors have not been calculated
for all areas of Alaska and the U.S. territories, a criterion of 20-
inches total annual rainfall (30-year average using National Weather
Service records) has been retained as a substitute for R factor for
construction sites in those locations unless an R factor applicable to
the construction site is calculated.
    EPA also considered approaches that would apply the turbidity
effluent limitation to larger sites (e.g., 50 acres instead of 30
acres) or with higher clay content of the soil (e.g., 20 percent
instead of 10 percent clay). More information about these potential
approaches is presented in the Development Document. EPA solicits
comment on whether Option 2 or other combinations of rainfall, clay
content and acreage limitations like those described above would be
more appropriate regulatory approaches and, if so, why, based on the
statutory requirements of CWA section 304, they should be considered to
represent BPT, BCT, BAT, or NSPS level of control for this industry.
Another option would be to base Option 2 on disturbed acres, instead of
the total site size. EPA solicits comments on this approach.
    EPA evaluated the advantages and disadvantages of establishing a
limitation on turbidity vs. total suspended solids (TSS) in stormwater
discharges from construction sites. EPA selected turbidity for two
reasons. First, EPA is specifically targeting fine silt, clay and
colloidal particles in stormwater runoff. These particles have small
diameters and frequently contain a surface charge that prevents
agglomeration. As a result, these particles typically do not settle in
sediment basins and are not effectively removed by conventional BMPs
such as silt fences, which have a large pore diameter. Consequently,
discharges from sites with appreciable clay soils may have low TSS
concentrations but may still have high turbidity levels. Second,
turbidity can be easily measured in the field while TSS requires
collection of a sample and analysis in a laboratory. Since most BMPs
and treatment systems are flow-through systems, TSS would not be a
practical means of estimating compliance because permittees would not
be able to verify whether or not they had met the standard before
discharging. With turbidity, permittees can measure turbidity levels in
discharges continuously and adjust treatment parameters accordingly or
recycle effluent if they are in danger of exceeding the turbidity
limit. For these reasons, EPA believes that turbidity is a more
appropriate measure of effectiveness and can be implemented more easily
than TSS. EPA requests comments on this approach.
    Option 2 is estimated to cost $1.9 billion per year (2008 $), not
including costs for Alaska, Hawaii and the U.S. territories, and reduce
discharges of pollutants by 27 billion pounds annually, with a
sensitivity analysis estimate of 6.2 billion pounds annually. Monetized
benefits of Option 2 are estimated to be $333 million annually.
     Option 3
    Under Option 3, all sites with common drainage locations that serve
an area with 10 or more acres disturbed at one time would be required
to comply with the turbidity effluent limitation (in addition to the
non-numeric effluent limitations in Option 1). This option does not
establish thresholds for R factor (or total annual rainfall) or soil
type (i.e., clay content). Under this option, all other sites (i.e.,
sites with less than 10 acres disturbed at one time) would be required
to implement the requirements described under Option 1 (for sites with
common drainage locations that serve an area of less than 10 acres
disturbed at one time).
    Option 3 is estimated to cost $3.8 billion per year (2008 $), not
including costs for Alaska, Hawaii and the U.S. territories, and reduce
discharges of pollutants by 50 billion pounds annually, with a
sensitivity analysis estimate of 11.1 billion pounds annually.
Monetized benefits of Option 3 are $470 million annually. EPA notes
that its modeling of acres subject to the options evaluated is based on
total site size instead of amount of disturbed area on a site. EPA does
not have data that can be used to estimate the percentage of a site
that is typically disturbed. For example, if a site is 15 acres, but
only 7 acres were to be disturbed, then under Option 3 this site would
not be subject to the turbidity standard. However, EPA has estimated
costs for Option 3 for all sites that, in total, are more than 10
acres. Therefore, to the extent that EPA has overestimated the quantity
of acres that would be subject to Option 3, EPA's estimates of costs,
benefits and loadings reductions for turbidity controls under Option 3
would also be overestimated.
    With regard to Option 3, depending on the location of the
construction site and time of year, it is possible that relatively
little rain would be expected during construction (based on historical
average rainfall patterns) and perhaps dischargers could opt to not
install active treatment systems. However, such an approach would
expose permittees to the risk of discharging stormwater that exceeds
the turbidity limit. On the other hand, taking an overly precautionary
approach could result in sites installing treatment equipment that sees
little or no use. EPA seeks comment on this issue.
    Also with regard to Option 3, EPA has also considered the
availability of treatment systems capable of achieving the turbidity
effluent limit, as well as whether there is sufficient vendor capacity
to meet the demand that would be presented by extending the turbidity
effluent limit to all construction sites disturbing more that 10 acres
at a time. Option 3 means that substantial numbers of active treatment
systems would need to be manufactured and mobilized, along with
sizeable levels of vendor support, in a relatively short period of time
as NPDES permits incorporating the ELGs and NSPS are issued.
    EPA solicits comments on this issue.

D. Option Selection Rationale for BPT

    EPA proposes to select Option 1 as the basis for establishing BPT
effluent limitations. The requirements established by Option 1 are
well-established for construction activities in all parts of the
country and are generally consistent with and in some cases more
stringent than the control measures currently in place under EPA's
Construction General Permit. Some requirements of Option 1 are more
stringent than many state general permits, while other requirements are
less stringent than some state general permits. EPA has determined that
Option 1 represents a level of control that is technologically
available and economically practicable. EPA considered the non-water
quality environmental impacts of this option and found them to be
minimal and thus acceptable. Selecting Option 1 as BPT for this point
source category is consistent with the CWA and regulatory
determinations made for other point source categories, in that the
Option 1 requirements represent limitations based on the average of the
best performance of facilities within the C&D industry. See Weyerhauser
Co. v. Costle, 590 F.2d 1011, 1053-54 (D.C. Cir. 1978). As stated in
Section III, EPA assesses cost-reasonableness of BPT effluent
limitations by considering the cost of treatment in relation to the
effluent reduction benefits achieved. EPA has determined that the
pollutant reduction benefits achieved by Option 1 justify the costs. We
have typically described this as dollars/pound and compare the results
with other rules. The incremental costs of Option 1 are approximately
$132 million per year

(2008 $). EPA anticipates that construction sites in approximately 11
states would incur costs to comply with the proposed Option 1 BPT
requirements requiring sediment basins generally consistent with the
EPA CGP. As noted above, the efficacy of this option may be
underestimated.
    EPA rejected Options 2 and 3 because EPA views BPT performance as
the first level of technology-based control representing the average of
the best performance. EPA's record does not indicate that meeting a
turbidity limit, even for the subset of facilities identified in Option
2 would represent today's average of the best performance and it would
not represent the BPT level of control for this point source category.
EPA requests comment on what should be considered BPT for this
category.

E. Option Selection Rationale for BAT and NSPS

1. Selection Rationale
    EPA proposes to select Option 2 as the basis for BAT and NSPS. This
option would require all C&D sites to implement the non-numeric
effluent limitations described for Option 1, as well as requiring
certain sites to meet a numeric limitation of 13 NTU (nephelometric
turbidity units) to control turbidity for stormwater discharges.
Turbidity is being regulated in this proposed rule as a nonconventional
pollutant and an indicator pollutant for the control of other
pollutants associated with sediment and materials on construction sites
that can become entrained in stormwater discharges from construction
sites, including metals and nutrients. Turbidity, measured as NTU,
which in construction site runoff primarily reflects sediment, is a
nonconventional pollutant because it is not identified as either a
toxic or conventional pollutant under the CWA. See CWA section
301(b)(2)(F); 304(a)(4); 40 CFR 401.16; Rybachek v. EPA, 904 F.2d 1276,
1291-92 (9th Cir. 1990). Turbidity is ``an expression of the optical
property that causes light to be scattered and absorbed rather than
transmitted with no change in direction of flux level through the
sample * * * caused by suspended and colloidal matter such as clay,
silt, finely divided organic and inorganic matter and plankton and
other microscopic organisms.'' 40 CFR 136.3; 72 FR 11200, 11247 (March
12, 2007). In this rulemaking, EPA is identifying turbidity as a
pollutant of concern in construction site discharges. By providing a
measure of the sediment entrained in stormwater discharges, turbidity
is an indicator of the degree to which sediment and other pollutants
associated with sediment and found in stormwater discharges are
reduced. Turbidity is also a more effective measure of the presence of
fine silts, clays and colloids, which are the particles in stormwater
discharges that EPA is specifically targeting in today's proposal.
    Metals, nutrients, and other toxic and nonconventional pollutants
are naturally present in soils, and can also be contributed by
equipment/materials used during construction or by activities that
occurred at the site prior to the construction activity. Many of these
pollutants are present as particulates and will be removed with other
particles. Dissolved forms of pollutants are often absorbed or adsorbed
to particulate matter and can also be removed along with the
particulates (i.e., sediment). EPA has determined that effluent
limitations that reduce turbidity in the stormwater discharge will also
achieve reductions of the other pollutants of concern. Demonstrating
compliance with a turbidity limit would be relatively easy and
inexpensive for construction site dischargers to implement. Hand-held
turbidity meters (turbidimeters) can be used to measure turbidity in
discharges, or data loggers coupled with in-line turbidity meters can
be used to automatically measure and log turbidity measurement reducing
labor requirements associated with sampling. In addition, the use of
turbidity meters will provide dischargers with immediate, real-time
information on the efficacy of their treatment systems and sediment
control measures to facilitate timely adjustments of system operation
where necessary.
    The requirements of Option 2 have been demonstrated to be
technologically available. Active treatment systems have been used and
are currently being used at several hundred construction sites
throughout the country. Construction sites where these active treatment
systems have been used are primarily located in California, Oregon and
Washington, with some in Florida, Maryland, Vermont and other states.
Oregon requires sites to meet a 160 NTU benchmark if the site is
discharging to a waterbody listed as not meeting applicable water
quality standards under section 303(d) or a waterbody with a total
maximum daily load (TMDL) for sediment and turbidity. Washington has
turbidity benchmark limits that are set at values relative to the
turbidity in the receiving steam. Benchmark requirements (e.g., in the
context of the Oregon and Washington permits), as opposed to numeric
effluent limits, require the facility to take some action to address
the potential water quality issue such as additional monitoring or BMP
review and do not result in a permit violation. Vermont requires what
it defines as ``moderate risk'' projects to take corrective action if
turbidity exceeds 25 NTUs. Also, several other states have turbidity
limitations or standards that are either in draft permits (such as
California), are set relative to background levels (Georgia), or are
set only for specific regions or specific waterbodies within the state
(such as the Lake Tahoe Basin of California) or for specific
construction projects (such as construction of a new runway at the Sea-
Tac airport). To comply with these turbidity-based requirements,
dischargers have used the active treatment systems described
previously--electrocoagulation, polymer clarification, and chitosan-
enhanced sand filtration, as well as other approaches. The information
in the record demonstrates the efficacy of these treatment systems,
showing that they consistently achieve very low levels of turbidity in
stormwater discharges. A summary of existing state requirements are
contained in the TDD.
    EPA also considered the recommendations of the National Research
Council (NRC). EPA commissioned the NRC to evaluate the NPDES
stormwater program and make recommendations for improvement of the
program. The Water Sciences and Technology Board released the report
Urban Stormwater Management in the United States (Committee on Reducing
Stormwater Discharge Contributions to Water Pollution, National
Research Council, National Academies Press) in October of 2008. The
report is the product of a 2-year process undertaken by a 15-member
committee of national experts.
    While the report did not specifically endorse numeric effluent
limits for construction sites, the report did contain several
recommendations, including that ``Numeric enforcement criteria can be
used to define what constitutes an egregious water quality violation at
construction sites and provide a technical criterion to measure the
effectiveness of erosion and sediment control practices.'' The study
continues to report that ``A maximum turbidity limit would establish
definitive criteria as to what constitutes a direct sediment control
violation and trigger an assessment for remediation and prevention
actions. For example, local erosion and sediment control ordinances
could establish a numeric turbidity limit of 75 Nephelometric

Turbidity Units (NTU) as an instantaneous maximum for rainfall events
less than an inch (or a 25 NTU monthly average) and would prohibit
visible sediment in water discharged from upland construction sites.
While the exact turbidity limit would need to be derived on a regional
basis to reflect geology, soils, and receiving water sensitivity,
research conducted in the Puget Sound of Washington indicates that
turbidity limits in the 25 to 75 NTU can be consistently achieved at