turbidity reduction at a significantly lower cost than active treatment
systems. Details on PTS used as a basis for developing the numeric
effluent limitation are contained in the Development Document as well
as in the administrative record. Several studies and data sources are
also summarized here.

    For example, McLaughlin (see DCN 41005) evaluated several
modifications to standard sediment trap designs at the North Carolina
State University Sediment and Erosion Control Research and Education
Facility (SECREF). He evaluated standard trap designs as contained in
the North Carolina Erosion and Sediment Control Manual utilizing a
stone outlet structure as well as alternative designs utilizing a
skimmer outlet and various types of porous baffles. Baffle materials
tested included silt fence, jute/coconut and tree protection fence
tripled over. Tests were conducted using simulated storm events in
which sediment was added to stormwater at flows of 10 to 30 liters per
second. McLaughlin found that a standard gravel outlet did not
significantly reduce turbidity values. Average turbidity values in the
basin were 843 NTUs, while average turbidity in the effluent was 758
NTUs using the standard outlet. Use of a skimmer instead of a standard
gravel outlet reduced turbidity to an average of 353 NTUs. Additional
tests were conducted to evaluate the addition of polyacrylamide (PAM)
through the use of floc-blocks. Floc-blocks are a solid form of PAM
which are designed to be placed in flowing water. They are typically
anchored by a rope or by placing them in a mesh bag or cage either in
open channels or in pipes. As the water flows over the floc-blocks, the
PAM dissolves somewhat proportional to flow. The floc-blocks typically
have substantial amounts of non-PAM components, which are intended to
improve PAM release, maintain the physical integrity of the blocks and
enhance PAM performance (McLaughlin--Soil Facts; Chemical Treatments to
Control Turbidity on Construction Sites). McLaughlin found that
addition of PAM to sediment traps resulted in average effluent
turbidities of 152 NTUs using a rock outlet and 162 NTUs using a
skimmer outlet. For one set of tests, use of a standard stone outlet
along with PAM was able to attain an average effluent turbidity of 51
NTUs, while tests with jute/coconut mesh baffles with PAM were only
slightly higher, at 71 NTUs.
    Warner and Collins-Camargo (see DCN 43071) evaluated several
innovative erosion and sediment controls at a full-scale demonstration
site in Georgia as part of the Erosion and Sedimentation Control
Technical Study Committee (known as ``Dirt II''). The Dirt II project
consisted, among other things, of field monitoring as well as modeling
of erosion and sediment control effectiveness at construction sites.
The demonstration site was a 50-acre lot in a suburban area near
Atlanta where a school was being constructed. In total, 22.5 acres of
the site was disturbed. A comprehensive system of erosion and sediment
controls were designed and implemented to mimic pre-developed peak flow
and runoff volumes with respect to both quantity and duration. The
system included perimeter controls that were designed to discharge
through multiple outlets to a riparian buffer, elongated sediment
controls (called seep berms) designed to contain runoff volume from 3-
to 4-inch storms and slowly discharge to down-gradient areas, multi-
chambered sediment basins designed with a siphon outlet that discharged
to a sand filter, and various other controls. Extensive monitoring was
conducted at the site. For one particularly intense storm event of 1.04
inches (0.7 inches of which occurred during one 27-minute period), the
peak sediment concentration monitored prior to the basin was 160,000
mg/L while the peak concentration discharged from the passive sand
filter after the basin was 168 mg/L. Effluent turbidity values ranged
from approximately 30 to 80 NTUs. Using computer modeling, it was shown
that discharge from the sand filter, which flowed to a riparian buffer,
was completely infiltrated for this event. Thus, no sediment was
discharged to waters of the state from the sand filter for this event.
For another storm event, a 25-hour rainfall event of 3.7 inches
occurred over a 2-day period. Effluent turbidity from one passive sand
filter during this storm ranged from approximately 50 to 375 NTU, with
20 of the 24 data points below 200 NTU. For a second passive sand
filter, effluent turbidity ranged from approximately 50 to 330 NTU,
with nine of 11 data points below 200 NTU. In estimating compliance
costs for the rule, EPA assumed that most operators would use sediment
basins or check dams with polymer addition to enhance settling, rather
than a passive sand filter. The Warner study indicates that using a
comprehensive suite of erosion and sediment controls, including a basin
with a surface outlet coupled with an in-ground passive sand filter may
be able to achieve comparable turbidity control to the technologies
that EPA costed without relying upon the use of polymers or
flocculants. EPA has not costed this approach for the rule, nor
included this data in calculation of the numeric limitation.
    There are other references in the literature describing the various
types of PTS and the efficacy of these systems. One application of a
PTS is to add liquid polymer, such as PAM, to the influent of a
conventional sediment basin. This can be accomplished by using a small
metering pump to introduce a pre-established dose of polymer in the
influent pipe or channel. If the polymer is added in a channel far
enough above the basin, then turbulent mixing in the channel can aid in
the flocculation process. Otherwise, some sort of provision may need to
be made to provide mixing in the basin to produce flocs. Polymers
typically used in this particular application include PAM, chitosan,
polyaluminum chloride (PAC), aluminum sulfate (alum) and gypsum.
    The Auckland (New Zealand) Regional Council conducted several
trials to evaluate the effectiveness of chemical flocculants and
coagulants in improving settling of suspended sediment contained in
sediment laden runoff from earthworks sites (DCN 42112). Trials were
conducted using both liquid and solid forms of flocculants. Trials were
initially conducted on two projects: a highway project and residential
development. A follow-on study evaluated passive basin dosing at an
additional site (see DCN 42102).
    The highway project (ALPURT) evaluated both a liquid polymer system
and solid polymers. Liquid polymers evaluated were alum and PAC and
solid polymers evaluated were all polyacrylamide products (Percol AN1,
Percol AN2 and Percol CN1). Bench tests indicated that AN2 performed
best among the solid polymers and that both PAC and alum were effective
in flocculating the soils present on the site.
    Following bench testing of the polymers, liquid and solid dosing
systems were developed. For the liquid dosing system, initial
consideration was given to a runoff proportional dosing system which
would include a weir or flume for flow measurement, an ultrasonic
sensor and signal generating unit, and a battery-driven dosing pump.
These components, together with costs for necessary site preparatory
work, chemical storage tanks and a secure housing, were estimated to
cost approximately $12,000 (1999 NZ $) per installation. An alternative
system was developed that provided a chemical dose proportional to
rainfall. This rainfall-driven system, which did not require either a
runoff flow measurement system or a dosing pump, had a total cost of
$2,400 (1999 NZ $) per installation.
    The rainfall-driven system operated by collecting rainfall in a
rainfall catchment tray that was designed

proportional to the watershed area. Rainfall into this tray was used to
displace the liquid treatment chemical from a storage tank into the
stormwater diversion channel prior to entering the sediment basin. The
size of the catchment tray was determined based on the size of the
catchment draining to the basin, taking into consideration the desired
chemical dosage rate obtained from the bench tests. Accumulated
rainfall from the catchment tray fills a displacement tank that floats
in the chemical storage tank. As the displacement tank fills with
rainfall and sinks, liquid chemical is displaced from the chemical
storage tank and flows via gravity to the dosing point.
    Field trials of the liquid treatment system using alum were
conducted at the ALPURT site. The authors report that the system
performed ``satisfactorily in terms of reduction of suspended solids
under a range of rainfall conditions varying from light rain to a very
high intensity, short duration storm, where 24mm of rainfall fell over
a period of 25 minutes.'' Suspended solids removal for the intense
storm conditions was 92% with alum treatment. For a similar storm on
the same catchment with the same retention pond without alum treatment,
suspended solids removal was about 10%.
    Field trials at the ALPURT site were also conducted using PAC. In
total, 21 systems were used with contributing catchments ranging
between 0.5 and 15 hectares (approximately 1 to 37 acres). The overall
treatment efficiency of the PAC-treated basins in terms of suspended
sediment reduction were reported to be between 90% and 99% for ponds
with good physical designs. The authors noted that some systems did not
perform as well due to mechanical problems with the system or physical
problems such as high inflow energy (which likely caused erosion or
sediment resuspension) or poor separation of basin inlets and outlets.
The suspended solids removal for all ponds incorporating PAC ranged
from 77% to 99.9%, while the removal in a pond not incorporating PAC
ranged from 4% to 12%. Influent suspended solids concentrations for the
systems incorporating PAC ranged from 128 to 28,845 mg/L while effluent
concentrations ranged from 3 to 966 mg/L. In comparison, influent
suspended solids concentrations for the untreated ponds were
approximately 1,500 mg/L while effluent concentrations were
approximately 1,400 mg/L. The authors also noted that dissolved
aluminum concentrations in the outflow from the basins treated with
PAC, in most cases, were actually less than the inflow concentrations,
and were also less than the outflow concentrations from the untreated
ponds. Outflow aluminum concentrations in the PAC treated ponds ranged
from 0.01 to 0.072 mg/L. The ALPURT trials indicate that a relatively
simple PTS using liquid polymers can result in significant reductions
in suspended sediment concentrations, even with influent concentrations
in excess of 25,000 mg/L. Although some effluent concentrations were as
high as several hundred mg/L, the majority were below 100 mg/L. This
indicates that a passive liquid polymer system can be used to meet a
numeric effluent limitation for turbidity at a capital cost on the
order of several thousand dollars per sediment basin. Coupling a system
such as this with a gravity sand filter or distributed discharge to a
vegetated buffer (as described by Warner and Collins-Camargo, DCN
43071) or dispersion would reduce discharge turbidity levels even
further, and for certain storm events would eliminate the discharge
altogether.
    Field trials of polymer treatment using solid forms of PAM by the
Auckland Regional Council were conducted at the ALPURT site as well as
a residential project (Greenhithe). Trials at the ALPURT site were
conducted by placing the floc-blocks in plastic mesh bags in plywood
flumes through which the runoff from the site was directed. Initial
trials encountered problems due to the high bedload of granular
material, which accumulated against and stuck to the floc-blocks
inhibiting solubility of the polymer. The system was reconfigured to
incorporate a forebay before the flumes in order to facilitate removal
of the bedload fraction. The authors noted that while this system was
generally effective at low flow rates, it was difficult to control
dosage rates and sediment accumulation in the flumes continued to be a
problem. The authors concluded that ``Floc Block treatment has a high
potential for removal of suspended solids from stormwater with
consistent quality, particularly for small catchments; when flow
balancing can be achieved prior to treatment.''
    Field trials were also conducted at the Greenhithe site, which was
a 4-hectare (approximately 10-acre) residential project. As with the
ALPURT trial, a flume was constructed and placed in the flow path
immediately before the sediment basin. Results of the trials were
mixed. The authors noted several problems with the floc-blocks, such as
drying and breakdown of the blocks due to prolonged exposure to the air
and softening and breakdown during periods of prolonged submergence.
Sediment accumulation around the blocks and breakdown continued to be a
problem. Incorporating an effective sediment forebay and limiting
bedload are suggestions for increasing performance. In addition, the
authors recommended soaking the floc-blocks in water to allow hydration
before use and periodic spraying with water as ways to limit drying of
the floc-blocks. EPA notes that similar problems with floc-blocks have
been noted by some construction site field inspectors (see DCN 41109)
and by McLaughlin (see DCN 43082). Because of the additional operation
and maintenance requirements associated with the use of floc-blocks, a
field inspection and maintenance program should be part of proper
application of this technology.
    Results of the PAC studies at the ALPURT sites have led the
Auckland regional council to require chemical treatment for any site
that produces more than 1.5 metric tons of (net) sediment as determined
by the Universal Soil Loss Equation. Sites that exceed this threshold
require chemical treatment in accordance with a site chemical treatment
plan. Exceptions include projects of less than one month duration and
sites with granular volcanic soils and sand areas. Chemical treatment
may also not be required if bench testing indicates that chemical
treatment will provide no improvement in sediment removal efficiency
(see DCN 41111).
    In addition to (or in place of) adding polymers to sediment basins,
polymers can be introduced on other areas of the site as a soil
stabilization measure or as components of other BMPs. For example,
McLaughlin (DCN 41005) evaluated adding polymer to check dams on
highway projects. McLaughlin noted significant reductions in turbidity
from the use of fiber check dams coupled with PAM application.
Significant reductions were even noted when PAM was added to rock check
dams. Other research done by McLaughlin with other researchers includes
studying the effectiveness of using PAM dosing systems for turbidity
reduction in stilling basins (EPA-HQ-OW-2008-0465-0984.4), and using
polymer blocks for turbidity control (EPA-HQ-OW-2008-0465-0984.7 and
0984.10). McLaughlin, Hayes et al. also studied modified sediment
control practices including polymer dosing at a transportation
construction site (EPA-HQ-OW-2008-0465-0984.3)
    Various other researchers evaluated PAM as a soil stabilization
agent. There are a number of documents in the administrative record for
this

rulemaking describing the use of PAM in this manner.
    The data from these sources, as well as other data in the record,
indicate that various types of PTS that utilize both solid and liquid
forms of polymers have been reported to be effective in reducing
turbidity levels in discharges from construction and development sites.
    EPA also considered the results of a three-year study conducted in
Georgia (Warner & Collins-Comargo, DCN 43071) which developed and
demonstrated cost-effective erosion prevention and sediment control
systems. These controls did not rely on the use of polymer, instead
they demonstrate the effectiveness of ponds, passive sand filters and
seep berms.

X. Development of Effluent Limitations Guidelines and Standards and
Options Selection Rationale

    In developing this final rule, EPA considered all the available
information, including information, data and analyses conducted in
support of the proposed rule, public comments received and additional
information and data collected by EPA following proposal which is
contained in the record. EPA evaluated a range of options for reducing
pollutant discharges associated with construction activity. The options
evaluated by EPA are intended to control the discharge of turbidity,
sediment and other pollutants in stormwater and other wastewater from
C&D sites.

A. Description of the Regulatory Options Considered

1. Options Considered in the Proposal
    In developing today's final rule, EPA evaluated several regulatory
options. The proposal discussed a wide range of options and presented a
detailed analysis for several options. As discussed earlier, Option 1
would have required implementation of erosion and sediment controls and
pollution prevention measures for all sites and the installation of a
sediment basin with a surface outlet for certain sites and other non-
numeric effluent limitations or BMPs; Option 2, would have added to the
requirements of Option 1 by establishing a requirement to monitor for a
numeric limitation for turbidity (13 NTU) based on the application of
ATS at sites of 30 or more acres with soil clay content of 10 percent
or more and an R-factor of 50 or larger; Option 3 would have expanded
the application of the turbidity limitation based on ATS to all sites
which disturb 10 or more acres. The proposal also presented and
solicited comment on another option that would require compliance with
a higher numeric turbidity effluent limitation (e.g., 50 to 150 NTU, or
some other value) based on passive treatment technologies (see 73 FR
72562, 72580-72582, 72610-72611). At proposal, EPA sought additional
data on the performance of PTS, and the cost and pollutant loading
reductions that would be attainable from such an option.
2. Regulatory Options Considered for the Final Rule and Rationale for
Consideration of Revisions to Options in the Proposed Rule
    In developing the final rule, EPA considered the wide range of
options considered in the proposed rule, and some revisions to those
options, based on comments received and additional information obtained
by EPA. EPA considered a revision to Option 1 to remove the requirement
for a sediment basin in response to concerns raised by commenters about
the appropriateness and availability of a basin at all construction
sites with 10 or more disturbed acres draining to one location. An
example includes areas where excavation is precluded due to the
presence of shallow bedrock. In addition to the sediment basin
requirements, EPA also considered modifying some of the erosion and
sediment control and pollution prevention requirements to make them
broadly applicable and compatible with all types of potentially
regulated construction activity, and considered deleting certain
proposed requirements. These changes to the non-numeric effluent
limitations are detailed in Section X.B of this notice.
    EPA considered a revision to Option 2 to remove the soil clay
content criteria as part of the basis for determining if a site would
be subject to the numeric limitation. Numerous commenters expressed
concern about difficulties associated with implementation of this soil
clay content criterion. Commenters raised questions, for example, about
how sites would measure soil content and to what depth would the soil
have to be sampled to determine the clay content (e.g., to a depth to
which excavation will occur, or only the top several inches). Also,
questions were raised as to the number of soil samples that would be
required of sites of different size. Also, commenters raised the
question of how to account for fill brought onto the site and the
variation in soil types present at different depths and at different
areas within the site. EPA also considered that adding complexity to
the applicability section generally makes it more difficult to comply
with, implement and enforce a rule. EPA agrees that the implementation
of a soil clay content criterion for determining whether a site would
be subject to a numeric limitation would be difficult to implement and
therefore considered removing this criterion from Option 2.
    EPA similarly considered modifying Option 2 to remove the RUSLE R-
factor criterion as part of the basis for determining if a site would
be subject to the numeric limitation. EPA received numerous comments
about the potential practical difficulties associated with this
criterion. Particularly, R-factor data is not readily available for all
areas of the country, including the entire state of Alaska. Also, in
certain areas of the country, the annual R-factor may be low, but soil
erosion rates may still be very high during certain time periods (such
as during spring thawing). Therefore, EPA determined that an annual R-
factor criterion, as proposed, would not be easily implementable, nor
necessarily target those sites with greater potential for soil erosion.
    EPA also considered revising Options 2 and 3 so that the monitoring
requirements and turbidity limitation would not apply to interstate
natural gas pipeline construction activity (see discussion in Section
VI).
    EPA also considered changing Option 2 so that the applicability of
the turbidity limitation would be a function of disturbed area of the
site, as opposed to the total size of the site. In addition, EPA
considered revising the non-numeric effluent limitations of Option 2
(as well as Option 3) to be consistent with the Option 1 requirements
discussed above.
    EPA also considered the option discussed in the proposal (Option 4)
that would establish a numeric limitation for turbidity based on the
application of PTS for the final rule. This option would require all
construction sites to implement the non-numeric effluent limitations
described for Option 1, as well as requiring sites equal to or greater
than a specified number of acres disturbed at one time to meet a
numeric limitation to control turbidity and other pollutants in
stormwater discharges from C&D sites. EPA considered thresholds of 1, 5
and 10 acres disturbed at one time for this option. The technology
basis for Option 4 consists of a suite of passive treatment
technologies and erosion and sediment controls that are currently used
at construction sites across the United States and abroad, as well as
in other industries, such as drinking water treatment and mining.
Examples of passive treatment technologies include sediment basins,
sediment traps and

other impoundments (with and without polymer or flocculant dosing),
polymer addition to fiber check dams, sand filtration, and dispersion
of stormwater to vegetated areas. PTS can substantially reduce the
amount of turbidity, sediment and other pollutants discharged from
construction sites. See Section IX for additional discussion of passive
treatment approaches.

B. Non-Numeric Effluent Limitations Included in All Regulatory Options

    Today's final rule, as well as the other options EPA considered,
includes a suite of non-numeric effluent limitations that apply to all
permitted C&D sites. This suite of non-numeric effluent limitations
makes up Option 1 and is also a component of Options 2, 3 and 4. These
non-numeric effluent limitations are structured to require permittees
to first prevent the discharges of sediment and other pollutants
through the use of effective planning and erosion control measures; and
second, to control discharges that do occur through the use of
effective sediment control measures. Permittees are also required to
implement a range of pollution prevention measures to limit or prevent
discharges of pollutants including those from dry weather discharges.
    The non-numeric effluent limitations that are included in all
options are designed to prevent the mobilization and discharge of
sediment and sediment-bound pollutants, such as metals and nutrients,
and to prevent or minimize exposure of stormwater to construction
materials, debris and other sources of pollutants on construction
sites. In addition, these non-numeric effluent limitations limit the
generation of dissolved pollutants. Soil on construction sites can
contain a variety of pollutants such as nutrients, organics,
pesticides, herbicides and metals. These pollutants may be present
naturally in the soil, such as arsenic or selenium, or they may have
been contributed by previous activities on the site such as agriculture
or industrial activities. These pollutants, once mobilized by rainfall
and stormwater, can detach from the soil particles and become dissolved
pollutants. Once dissolved, these pollutants would not be removed by
down-slope sediment controls. Source control through minimization of
soil erosion is therefore the most effective way of controlling the
discharge of these pollutants. Therefore, the non-numeric effluent
limitations are important components of the final rule not only for the
purposes of limiting sediment generation and discharge, but also to
minimize the discharge of dissolved pollutants.
    The non-numeric effluent limitations in the final rule apply to all
permitted C&D sites including the sites that are subject to the numeric
effluent limitation and monitoring requirements at 40 CFR 450.22. (See
Section X.G.) EPA has the authority under the CWA to establish non-
numeric effluent limitations as supplemental to a numeric effluent
limitation or in place of a numeric effluent limitation. See Citizens
Coal Council v. EPA, 447 F.3d 879, 896 (6th Cir. 2006). The non-numeric
effluent limitations in this rule are necessary for those sites that
are also subject to the numeric effluent limitation for turbidity
because the non-numeric effluent limitations may address different
pollutants or the same pollutants differently, the numeric effluent
limitation is not applicable on days when total precipitation on that
day is greater than the local 2-year, 24-hour storm event (See Section
XIX.A), and the fact that sites may fluctuate above and below ten acres
of disturbed land. Thus there will be times when sites are discharging
pollutants in excess of the numeric effluent limitation and the non-
numeric effluent limitations will be the only applicable effluent
limitation and are thus essential to the control of discharges from the
site. Also, some of the non-numeric effluent limitations are addressing
discharges unrelated to the discharge of turbidity, for example, 40 CFR
450.21(e)(1) which prohibits the discharge of ``wastewater from washout
of concrete, unless managed by an appropriate control'' addresses
pollutants such as pH and can occur during precipitation related events
or dry weather discharges. The structure of the final rule, including
the requirement that the non-numeric effluent limitations apply to all
sites, was supported by state permitting authorities and is similar to
the structure of the newly issued California CGP (see DCN 42104).
    The final rule contains non-numeric effluent limitations that
require the permittee to minimize the discharge of pollutants. Under
the regulatory structure of the final rule the permitee can minimize
the discharge of pollutants from construction sites by utilizing non-
numeric effluent limitations or BMPs such as the erosion and sediment
controls listed below at (i) through (vii) and at 40 CFR 450.21(a)(1)
through (7). The erosion and sediment controls at (i) through (vii)
below are what EPA has determined are the required non-numeric effluent
limitations that are necessary for owners or operators of construction
sites to utilize in order to minimize the discharge of pollutants from
the site. This is true for the other non-numeric effluent limitations
at 40 CFR 450.21 as they are what EPA has determined are the required
controls necessary to minimize, control or prohibit discharges of
pollutants from construction sites. The permitting authority may
determine that additional non-numeric effluent limitations or specific
BMPs are necessary in order to minimize the discharge of pollutants and
EPA has structured 40 CFR 450.21 to allow the permitting authority that
discretion. Due to geographic differences or other variable factors a
permitting authority may choose to require additional or more stringent
non-numeric effluent limitations in its individual or general NPDES
permits for discharges associated with construction activity. For
example, the permitting authority may determine that it is necessary
for permitees to initiate soil stabilization measures when construction
activity has permanently or temporarily ceased and will not resume for
a period exceeding 7 calendar days, as opposed to 14 calendar days at
X.B.1.b below or that additional erosion and sediment controls are
necessary. EPA purposefully drafted the non-numeric effluent
limitations to allow for flexibility in how the permitting authority
implements the requirement in NPDES permits. For example, in the
erosion and sediment control section below at section X.B.1.a.iv EPA
simply required that permitees ``minimize the disturbance of steep
slopes'' leaving it up to the permitting authority to determine the
specific requirements applicable to owners or operators of C&D sites to
minimize disturbance of steep slopes in order to minimize the discharge
of pollutants from the site. This flexibility built into the final rule
will also benefit permittees by allowing the owners or operators of
construction sites discretion to choose BMPs that will minimize the
discharge of pollutants based on the unique nature of the particular
site. For example, at 40 CFR 450.21(a)(5), the final rule states that
construction sites must design, install and maintain controls to
``minimize sediment discharges from the site.'' Absent specific
requirements from the permitting authority the final rule gives the
permittee discretion to choose what practices and controls to use to
minimize the discharge of sediment from the site based on the site
specific nature of the construction activity.
    The non-numeric effluent limitations are required for all sites,
but there are

site-specific considerations that may make one or more of the
provisions infeasible on a particular site. EPA has specifically
qualified some of the requirements to state that the requirement must
be implemented unless infeasible. By infeasible, EPA means that there
is a site-specific constraint that makes it technically infeasible to
implement the requirement, or that implementing the requirement would
be cost-prohibitive. The burden is on the permittee to demonstrate to
the permitting authority that the requirement is infeasible.
    With respect to the soil stabilization language at Sec.  450.21(b),
EPA has qualified the soil stabilization requirements such that
vegetative stabilization may be delayed in arid or semi-arid areas, or
if an area is experiencing a drought such that vegetative stabilization
practices cannot be initiated. In such cases, the permittee should
consider non-vegetative stabilization practices. In addition, EPA would
generally not expect permitting authorities to require vegetative
stabilization in areas that are excessively rocky or infertile, that
have non-erodible soils (such as sands), certain coastal areas, or
during periods when snow or ice are covering the ground and generally
in areas where vegetative stabilization would not be appropriate.
Permitting authorities should incorporate this requirement into permits
with consideration of appropriate stabilization measures for various
areas within their jurisdiction.
    EPA made several revisions to the non-numeric effluent limitation
since proposal. Some of these revisions were made in response to
comments, while others were made as a result of EPA re-evaluating the
feasibility and appropriateness of some of the proposed requirements.
Section X.B.1 describes the non-numeric effluent limitations contained
in the final rule while Section X.B.2 describes how the non-numeric
effluent limitations in final rule differ from those in the proposal.
1. Non-Numeric Effluent Limitations Contained in the Final Rule
    The non-numeric effluent limitations contained in the final rule
are as follows:
a. Erosion and Sediment Controls
    Permittees are required to design, install and maintain effective
erosion controls and sediment controls to minimize the discharge of
pollutants. At a minimum, such controls must be designed, installed and
maintained to:
    i. Control stormwater volume and velocity within the site to
minimize soil erosion;
    ii. Control stormwater discharges, including both peak flowrates
and total stormwater volume, to minimize erosion at outlets and to
minimize downstream channel and streambank erosion;
    iii. Minimize the amount of soil exposed during construction
activity;
    iv. Minimize the disturbance of steep slopes;
    v. Minimize sediment discharges from the site. The design,
installation and maintenance of erosion and sediment controls must
address factors such as the amount, frequency, intensity and duration
of precipitation, the nature of resulting stormwater runoff, and soil
characteristics, including the range of soil particle sizes expected to
be present on the site;
    vi. Provide and maintain natural buffers around surface waters,
direct stormwater to vegetated areas to increase sediment removal and
maximize stormwater infiltration, unless infeasible; and
    vii. Minimize soil compaction and, unless infeasible, preserve
topsoil.
b. Soil Stabilization Requirements
    Permittees are required to, at a minimum, initiate soil
stabilization measures immediately whenever any clearing, grading,
excavating or other earth disturbing activities have permanently ceased
on any portion of the site, or temporarily ceased on any portion of the
site and will not resume for a period exceeding 14 calendar days.
Stabilization must be completed within a period of time determined by
the permitting authority. In arid, semiarid, and drought-stricken areas
where initiating vegetative stabilization measures immediately is
infeasible, vegetative stabilization measures must be initiated as soon
as practicable.
c. Dewatering Requirements
    Permittees are required to minimize the discharge of pollutants
from dewatering trenches and excavations. Discharges are prohibited
unless managed by appropriate controls.
d. Pollution Prevention Measures
    Permittees are required to design, install, implement, and maintain
effective pollution prevention measures to minimize the discharge of
pollutants. At a minimum, such measures must be designed, installed,
implemented and maintained to:
    i. Minimize the discharge of pollutants from equipment and vehicle
washing, wheel wash water, and other wash waters. Wash waters must be
treated in a sediment basin or alternative control that provides
equivalent or better treatment prior to discharge;
    ii. Minimize the exposure of building materials, building products,
construction wastes, trash, landscape materials, fertilizers,
pesticides, herbicides, detergents, sanitary waste and other materials
present on the site to precipitation and to stormwater; and
    iii. Minimize the discharge of pollutants from spills and leaks and
implement chemical spill and leak prevention and response procedures.
e. Prohibited Discharges
    The following discharges from C&D sites are prohibited:
    i. Wastewater from washout of concrete, unless managed by an
appropriate control;
    ii. Wastewater from washout and cleanout of stucco, paint, form
release oils, curing compounds and other construction materials;
    iii. Fuels, oils, or other pollutants used in vehicle and equipment
operation and maintenance; and
    iv. Soaps or solvents used in vehicle and equipment washing.
f. Surface Outlets
    When discharging from basins and impoundments, permittees are
required to utilize outlet structures that withdraw water from the
surface, unless infeasible.
2. Changes to the Non-Numeric Effluent Limitations Since Proposal
    EPA made a number of changes to the non-numeric effluent
limitations for the final rule. EPA does not view these changes as
making the final rule requirements less stringent than those contained
in the proposal, but rather views these changes as necessary
adjustments that make the requirements applicable to all types of
construction activities. EPA has determined that many of the
requirements, as proposed, could not be implemented on every
construction site due to technical reasons. In general, some
requirements were eliminated, while others were revised to include
``unless infeasible'' language, recognizing that not every site will be
able to implement every one of the proposed requirements. Also, the
requirements were re-arranged to separate erosion and sediment control
requirements from soil stabilization and pollution prevention
requirements. However, EPA believes that most practices can be
implemented on most sites, and where a practice is feasible and
necessary for effective control of pollutant discharges from stormwater

runoff, this rule requires that it be implemented. The changes made, by
section of the proposed rule text, along with the rationale for the
changes are as follows:
    Section 450.21(a): The definition of when erosion controls are
considered effective has been deleted since effectiveness varies based
on site-specific parameters. In addition, the proposed language was
limiting in that there may be other objective measures of effectiveness
that were not described by EPA. The requirement to stabilize exposed
soils has been incorporated into a ``Soil Stabilization'' section in
the final rule at Sec.  450.21(b).
    Section 450.21(a)(4): The requirement to minimize the amount of
soil exposed at any one time has been removed as the soil stabilization
language at Sec.  450.21(b) requires immediate stabilization.
    Section 450.21(a)(5): The requirement to preserve natural
vegetation was removed as there are cases where preserving the natural
vegetation may not be compatible with the ultimate land use. The
requirement to preserve topsoil was changed to include ``unless
infeasible,'' recognizing that it may not always be feasible to
preserve topsoil depending on the ultimate land use.
    Section 450.21(a)(6): The language regarding minimizing soil
compaction was simplified and now includes ``unless infeasible,'' and
the requirements for deep ripping and decompaction and incorporation of
organic matter to restore infiltrative capacity were deleted because
the use of these techniques is dependent upon the ultimate land use.
    Section 450.21(a)(7): The requirement for providing and maintaining
natural buffers around surface waters was combined with the requirement
to direct discharges to vegetated areas found in Sec.  450.21(b)(9) and
now includes ``unless infeasible.''
    Section 450.21(a)(8): The requirement to minimize the construction
of stream crossings was deleted as the construction of stream crossings
on a particular project is determined by consideration of a number of
factors, and simply minimizing the number based on erosion and sediment
control considerations may conflict with other considerations. EPA has
determined that this requirement is best left to the discretion of the
permitting authority.
    Section 450.21(a)(9): The requirement to sequence/phase
construction activities was deleted. EPA believes that permittees
should consider sequencing or phasing for projects, particularly for
larger or longer-duration projects. Phasing construction so that less
than 10 acres of land are disturbed at any one time is one way for
owners or operators of construction sites to comply with the rule
without having to sample discharges and meet the numeric limitation in
Option 4. EPA believes that this is appropriate because of the
environmental benefits of such sequencing. However, EPA has determined
that this is a site-specific consideration best addressed by the
permitting authority.
    Section 450.21(a)(11): The requirement to implement erosion
controls on slopes was deleted as the soil stabilization requirements
encompasses all types of stabilization, not just on slopes.
    Section 450.21(a)(12): The requirement to establish temporary or
permanent vegetation to stabilize exposed soils was deleted as
vegetative controls may not always be the most appropriate
stabilization measures. The selection of appropriate stabilization
techniques is best left to the discretion of the permitting authority.
    Section 450.21(a)(13): The requirement to divert stormwater that
runs onto the site away from disturbed areas of the site was deleted as
this may not always be feasible, or, in certain instances, may increase
off-site erosion.
    Section 450.21(b): The sediment control requirements were combined
with the erosion control requirements into a new section titled
``Erosion and Sediment Controls'' at Sec.  450.21(a) in the final rule
regulatory text. The requirement to install sediment controls prior to
commencement of construction and to maintain during all phases of
construction activity was deleted as the timing of implementation of
controls is site-specific. Maintenance of controls is inherent in
permits and it is not necessary to include this requirement in the
national rule.
    Section 450.21(b)(1): The requirement to establish and maintain
perimeter controls was deleted, as the need for perimeter controls is
dictated by site topography. The requirement to discharge stormwater
from perimeter controls through vegetated buffers and functioning
stream buffers was deleted. This requirement now applies to all
discharges, unless infeasible, as described at Sec.  450.21(a)(6).
    Section 450.21(b)(2): The requirement to control discharges from
silt fences using a vegetated buffer or filter strip was deleted as
this may not always be feasible, depending on the site location or
climate.
    Section 450.21(b)(3): The requirement to minimize slope length and
to install linear sediment controls and slope breaks on erodible slopes
was deleted as the need for these controls is dictated by site-specific
considerations and is best left to the discretion of the permitting
authority.
    Section 450.21(b)(4): The requirements to establish construction
entrances and exits and to utilize wheel wash stations were deleted as
it may not always be feasible to utilize wheel wash stations (for
example, in remote areas). The need for construction entrances and
exits are dependent on site configuration.
    Section 450.21(b)(5): The requirement to remove sediment from paved
surfaces daily and the prohibition on washing sediment and other
pollutants into storm drains were deleted. The need for these
requirements depend on site configuration (i.e., if storm drains
discharge to a sediment control or discharge off-site).
    Section 450.21(b)(6): The requirement to implement controls to
minimize the introduction of sediment and other pollutants to storm
drain inlets was deleted (for the same reason as Sec.  450.21(b)(5)
above).
    Section 450.21(b)(7): The language regarding dewatering was changed
to be specific to dewatering trenches and excavations. This language is
now found at Sec.  450.21(c).
    Section 450.21(b)(8): All language regarding sediment basins was
deleted (see Section VII.A).
    Section 450.21(b)(9): The requirement to direct discharges from
sediment controls to seep berms and level spreaders and to utilize
spray or drip irrigation systems was changed. This requirement now
applies to all discharges, but is more general in that it does not
specify techniques, but rather requires all discharges to be directed
to vegetated areas, unless infeasible (now found at Sec.
450.21(a)(6)). This provides more flexibility for permittees to select
appropriate techniques.
    Section 450.21(c): The language describing examples of effective
pollution prevention measures was deleted and instead the new
requirement at Sec.  450.21(d) is to ``design, install, implement and
maintain effective pollution prevention measures'' as this language is
not limiting to those measures described in the proposal. In addition,
pollution prevention requirements in the final rule are presented
separately from a series of ``prohibited discharges''. At proposal,
these two concepts were presented together.
    Section 450.21(c)(1): Discharges of construction waste, trash and
sanitary wastes are not prohibited in the final rule, but rather the
requirement is to minimize the exposure of a variety of

materials to precipitation and stormwater (now found at Sec.
450.21(d)(2)). EPA has determined that a requirement to minimize
exposure to precipitation and stormwater, rather than a strict
prohibition on the discharge of these materials, is a more appropriate
requirement as it may not always be feasible to prevent these materials
from being discharged from the site.
    Section 450.21(c)(2): Concrete washout is now addressed separately
at Sec.  450.21(d)(1), and discharges are allowed if managed by
appropriate controls. The concrete washout provision is not a
prohibition, as are discharges from other sources, because there are
technologies available to treat concrete washout. Therefore, discharges
of wastewaters from concrete washout are allowed if managed by
appropriate controls. Wastewater from washout of form release oils and
curing compounds have been added to the list of prohibited discharges
at Sec.  450.21(d)(2).
    Section 450.21(c)(4): The requirement was changed to clarify that
the prohibition is on the discharge of soaps and solvents.
    Section 450.21(c)(5): The requirement was changed so as not to
prohibit the discharge of wash waters but rather to control discharges
from equipment and vehicle washing and wheel wash, recognizing that
wash waters can be managed using appropriate controls.
    Section 450.21(c)(6): ``Building products'' were added to the list
of materials, and spills and leaks are addressed in a separate
requirement (Sec.  450.21(d)(3)).
    Section 450.21(c)(7): The requirement to prevent runoff from
contacting areas with uncured concrete was deleted, as this may not be
feasible on some sites (such as bridges, roads, etc.).

C. Numeric Effluent Limitations and Standards Considered

    EPA considered numeric effluent limitations based on primarily two
suites of technologies for the final rule. The first, advanced
treatment systems or ATS, were described in the proposed rule under
Options 2 and 3. For the final rule, EPA considered effluent
limitations for turbidity based on ATS for site size thresholds of 10
acres and 30 acres of disturbed land. As described earlier, these
options are similar to those contained in the proposal, except the soil
clay content and R-factor criteria have been removed from Option 2. In
addition, Option 2 would apply to sites of 30 or more disturbed acres.
At proposal, Option 2 would have applied if the site was 30 or more
acres, regardless of the amount of land disturbed on the project
    The second technology suite, passive treatment systems or PTS,
constitutes the technology basis for today's final rule. In the
proposal, EPA considered the establishment of numeric turbidity
limitations based on PTS and solicited comment and additional
information and data on this option. For the final rule, EPA considered
numeric limitations for turbidity based on PTS for a site size
threshold of 10 or more acres disturbed at one time (Option 4). EPA
also evaluated site size thresholds of 1 and 5 acres disturbed at one
time.
    Additional information on both PTS and ATS is presented in Section
IX of today's notice, the development document and in the
administrative record. The nomenclature presented in Table X-1 is used
to describe these options throughout today's notice.

 Table X-1--Main Options Considered for Numeric Effluent Limitations and
                                Standards
------------------------------------------------------------------------
                                                           Site size
             Option                Technology basis    threshold  (acres
                                                          disturbed)
------------------------------------------------------------------------
2..............................  Active Treatment...  30 or more.
3..............................  Active Treatment...  10 or more.
4..............................  Passive Treatment..  10 or more.
------------------------------------------------------------------------

    For all of these options, the numeric turbidity limitation would
apply to all discharges from the site except on days when total
precipitation during the day exceeded the local 2-year, 24-hour storm.
If the total precipitation in any one day is greater than the local 2-
year, 24-hour storm event, then permittees would still need to sample
(because they wouldn't know in advance whether the precipitation on
that day was going to exceed the storm size threshold) but the numeric
effluent limitation would not apply to discharges for that day.
However, the numeric effluent limitation is applicable to all
discharges from the site on subsequent days if there is no 2-year, 24-
hour storm event during those days. Even when total precipitation
during the day exceeds the local 2-year, 24-hour storm permittees must
comply with the non-numeric effluent limitations Sec.  450.22(c)
through Sec.  450.22(h). (See Section XIX.A for EPA's rationale for
selecting the 2-year, 24-hour storm event).
    Under all the options considered that contain a numeric limitation,
the limitation applies so long as the total amount of disturbed area on
the project, at any one time, is at or above the specified acreage
threshold (i.e., 10, 20 or 30 acres). For example, under Option 4, if a
project initially disturbs 10 or more acres of land at one time during
construction activity, but after completion of clearing and grading and
infrastructure installation the site is stabilized prior to or during
commencement of vertical construction, then the sampling requirements
and turbidity limitation would cease to apply at the point where the
total disturbed land area at the site is less than 10 acres at one
time. So long as the total disturbed land area at one time remains
below 10 acres for the remainder of the construction activity, the
sampling requirements and turbidity limitation would not apply. If,
however, at some point during the remainder of the project 10 or more
acres were to be disturbed at one time, then the sampling requirements
and turbidity limitation would again apply to all discharges from the
C&D site. This 10 acre threshold also applies to projects that are part
of a larger common plan of development. If an individual portion of a
project disturbs less than 10 acres at one time, but the amount of land
disturbed at one time under the larger common plan of development is 10
or more acres, then sampling of discharges from the entire project is
required during the period when the total disturbed land for the whole
project is 10 or more acres.
    EPA has also found it is reasonable to allow time for permitting
authorities to develop monitoring requirements and to allow the
regulated community time to prepare for compliance with a numeric
limitation. Compliance with the numeric limitation and the associated
monitoring requirements are not required until 18 months after the
effective date of this rule for sites with 20 or more acres of land
disturbed at one time and four years after the

effective date for sites with 10 or more acres of land disturbed at one
time. EPA's rationale for this decision is described in Section XIX.B.
    In addition to the issue discussed above regarding EPA's
determination that turbidity is the appropriate end point for today's
rule because of its applicability to more than simply conventional
pollutants, EPA evaluated the advantages and disadvantages of
establishing a limitation on turbidity rather than total suspended
solids (TSS). Turbidity is more appropriate because turbidity can be
easily measured in the field while TSS requires collection of a sample
and analysis in a laboratory. Demonstrating compliance with a turbidity
limitation is relatively easy and inexpensive for construction site
owners or operators 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 measurements reducing labor
requirements associated with sampling. Since most controls and
treatment systems are flow-through systems, the use of TSS would not
allow permittees to gauge performance in the field and take any
correction action if they are in danger of violating the limitation.
With the limitation based on the pollutant turbidity, permittees can
measure turbidity levels in discharges continuously, with immediate,
real-time information on the efficacy of their controls, and take
immediate action if they are in danger of exceeding the turbidity
limitation. For these reasons, EPA has determined that turbidity is a
more appropriate measure of the effectiveness of the PTS and the
technology can be implemented more easily by utilizing turbidity rather
than TSS.

D. Selected Options for BPT, BCT, BAT and BADT for NSPS

    EPA has selected Option 1 as the basis for BPT and BCT and EPA has
selected Option 4 as the basis for BAT and BADT for NSPS. Option 1
requires all C&D sites to implement a range of non-numeric effluent
limitations. Option 4 requires all C&D sites to implement the same
range of non-numeric effluent limitations as in Option 1 and requires
sites with 10 or more acres of disturbed land at one time to meet a
numeric limitation based on PTS to control pollutants in stormwater
discharges.

E. Selection Rationale for BPT

    EPA is establishing BPT effluent limitations on the basis of the
technologies described under Option 1. EPA has determined that the non-
numeric effluent limitations in Option 1 represent a level of control
that is technologically available and economically practicable and
represents the average of the best performance of construction sites in
the C&D point source category considering the factors in CWA section
304(b)(1)(B). The requirements established by Option 1 are well-
established for construction activities in all parts of the country.
The Option 1 requirements are generally consistent with the
requirements currently in place under the existing Construction General
Permits issued by EPA and most states. Many of these types of effluent
limitations have been in place in NPDES permits for discharges
associated with construction activity since at least the early 1990s.
Prior to the issuance of the 1990 NPDES Phase I regulations, many
existing state laws and regulations required the implementation of
erosion and sediment controls. Many of these controls were first used
beginning in the 1960s and 1970s, and they are well-established
industry practices. In Option 1, EPA has taken this established
approach to controlling stormwater discharges from construction sites
and established minimum requirements for owners or operators of the
site. In some cases the narrative limitations of Option 1 are more
stringent than past EPA general permit requirements, e.g., the soil
stabilization requirements are more stringent than the 2008 EPA CGP.
These requirements represent the average of the best performance of the
industry because they are being used effectively by construction
operators and/or EPA's analysis indicates that the costs are small in
relation to the effluent reduction benefits to be achieved from such
requirements, traditionally measured in terms of cost per pound of
pollutant removed. As stated in Section III.D., EPA assesses cost-
reasonableness of BPT effluent limitations by considering the cost of
treatment in relation to the effluent reduction benefits achieved,
typically in dollars/pounds of pollutants reduced. EPA has determined
that the costs in relation to the pollutant reduction benefits of the
selected option for BPT are reasonable. The costs per pound of sediment
removed expressed as TSS for Option 1 is $0.10 per pound ($ 2008). The
range of costs per pound removed for other industrial categories is
$0.26 to $41.44 per pound in year 2008 dollars.
    EPA considered the non-water quality environmental impacts of
Option 1 including energy usage, air emissions and solid waste handling
associated with the non-numeric effluent limitations. Energy usage
associated with the non-numeric effluent limitations includes fuel
consumption for construction equipment to excavate and install erosion
and sediment controls and excavation and placement or disposal of
accumulated sediment (see Section XIV.C). Air emissions associated with
the non-numeric effluent limitations would be emissions generated from
the burning of fuel by construction equipment (see Section XIC.A).
Solid waste generated from stormwater treatment includes the polymer-
laden sediment settled out during treatment, if polymers or flocculant
are utilized, though they are not part of the technology-basis for BPT
(see Section XIV.B). EPA found the non-water quality environmental
impacts associated with Option 1 to be minimal and acceptable. The non-
water quality environmental impacts associated with the BPT effluent
limitations are negligible as there is little incremental energy
expended in the implementation of the erosion and sediment controls,
since these types of controls are already being implemented by the
majority of construction sites nationwide. 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 point
source category. See Weyerhauser Co. v. Costle, 590 F. 2d 1011, 1053-54
(D.C. Cir. 1978).
    EPA rejected Options 2, 3 and 4 as the basis for BPT because EPA
views BPT as the first level of technology-based control representing
the average of the best performance on a national basis. Although
meeting a numeric limitation represents BAT and BADT for NSPS, as
discussed below, meeting a numeric effluent limitation is a substantial
change for most owners or operators engaged in construction activity
nationwide. EPA's record does not indicate that meeting a numeric
turbidity limitation, even for the subset of facilities identified in
Option 4, represents today's average of the best performance and
therefore it does not represent the BPT level of control for this point
source category.

F. Selection Rationale for BCT

    EPA is establishing BCT equivalent to BPT, based on Option 1. BCT
represents the best control technology for conventional pollutants
which is primarily TSS for the construction and development point
source category. As discussed in X.E above, the

requirements of Option 1have been demonstrated to be technologically
available and EPA's analyses show that the requirements are
economically practicable. Establishing BCT effluent limitations for a
point source category begins by identifying technology options that
provide additional conventional pollutant control beyond that provided
by application of BPT effluent limitations. Conventional pollutants
under the CWA are biochemical oxygen demand (BOD5), TSS,
fecal coliform, pH, and oil and grease. CWA section 304(a); 40 CFR
401.16. Stormwater discharges, if not adequately controlled, can
contain very high levels of TSS. In addition, many of the construction
materials used at the site can contribute BOD or oil and grease. Fecal
coliform can also be present at elevated levels, due to natural sources
(contributed by animal wastes) or if stormwater is not segregated from
sanitary waste facilities. See Section VIII for additional discussion
of pollutant sources.
    EPA evaluates the candidate BCT options by applying the two-part
BCT cost test. The first part of the BCT cost test is the POTW test. To
``pass'' the POTW test, the cost per pound of conventional pollutant
discharges removed in upgrading from BPT to the candidate BCT must be
less than the cost per pound of conventional pollutant removed in
upgrading POTWs from secondary treatment to advanced secondary
treatment. Using the RS Means Historical Cost Indices, the inflation-
adjusted POTW benchmark (originally calculated to be $0.25 in 1976
dollars) is $0.92 (2008 $). To examine whether an option passes this
first test, EPA calculates incremental values of the candidate option
relative to the selected BPT (Option 1). EPA calculated the incremental
cost per pound of conventional pollutants removed ($/lb TSS) for Option
2 to be $2.50. Since this result is more than the POTW benchmark,
Option 2 fails the first part of the two-part BCT cost test. EPA also
calculated the incremental cost per pound of conventional pollutants
removed for Option 3, which is $3.22. Therefore, Option 3 also fails
the first part of the BCT cost test. EPA also calculated the
incremental cost per pound of conventional pollutants removed for
Option 4, which is $0.35. Therefore, Option 4 passes the first part of
the BCT cost test.
    To pass the second part of the BCT cost test, the industry cost
effectiveness test, EPA computes a ratio of two incremental costs. The
numerator is the cost per pound of conventional pollutants removed by
the BCT candidate technology relative to BPT. The denominator is the
cost per pound of conventional pollutants removed by BPT relative to no
treatment (i.e., raw wasteload). As in the POTW test, the ratio of the
numerator divided by the denominator is compared to an industry cost
benchmark. The industry cost benchmark is the ratio of two incremental
costs: The cost per pound to upgrade a POTW from secondary treatment to
advanced secondary treatment, divided by the cost per pound to
initially achieve secondary treatment from raw wasteload. If the
calculated ratio is lower than the industry cost benchmark of 1.29
(i.e., the normalized cost increase must be less than 29 percent), then
the candidate technology passes the industry cost test. Since both
Option 2 and 3 fail the first part of the BCT cost test, it is not
necessary to compute the ratio for the second part. The calculated
ratio for Option 4 is 5.47; therefore, Option 4 fails the second part
of the BCT cost test. Therefore, EPA is setting BCT equal to Option 1.

G. Selection Rationale for BAT and BADT for NSPS

1. Selection Rationale
    EPA is selecting Option 4 as the basis for BAT and BADT for NSPS.
The requirements of the selected Option have been demonstrated to be
technologically available, economically achievable, pose no barrier to
entry and have acceptable non-water quality environmental impacts (see
section XIV) and thus represent BAT and BADT for NSPS. As described
above in Section III.D of this notice, the CWA requires EPA to consider
several of the same factors when establishing BAT and NSPS. Both levels
of control are based on the best technology, considering the cost of
achieving such effluent reduction and any non-water quality
environmental impacts (including energy requirements). See CWA sections
304(b)(2)(B) and 306(b)(1)(B). The principle difference between the two
technology standards is the potential for new sources under NSPS to
install the best available demonstrated control technology without the
cost to retrofit new technology into an existing site. In both cases,
the Agency must determine that the requirement will not cause
unacceptable economic impacts to the industry as a whole or by
presenting a barrier to entry to new facilities.
    The construction industry is different from other industries when
considering closures and barriers to entry. For this industry, the
permitted activity is a temporary project rather than ongoing
operations at a permanent facility. This is an important distinction,
in that it provides construction firms with greater flexibility in how
they respond to the rule. Not only can they elect to use one or more
technologies to ensure compliance with the rule for a project they can
also plan the dimensions and timing of the project in such a way as to
minimize the effects of the rule on project profitability. As all new
construction projects are new and impermanent, there is no meaningful
distinction between new and existing sources, from the standpoint of
economic affordability. As such, EPA is discussing the basis for both
BAT and NSPS together.
    EPA has determined that a numeric limitation as well as non-numeric
effluent limitations for sites with 10 or more acres disturbed at one
time is technically available as that term is used in the CWA. The
technologies used to meet the limitation in Option 4 are non-numeric
effluent limitations or BMPs, the use of polymer-aided settling, and
site planning techniques such as limiting the amount of land disturbed
at any one time or phasing construction activities. These technologies
are currently being utilized throughout the country and EPA has
determined that the use of these technologies will result in stormwater
discharges from C&D sites consistently meeting the requirements of
Option 4. EPA has determined that a numeric effluent limitation is
achievable based on the performance of these technologies measured by
the information and data described in Section IX.E and by information
concerning similar treatment systems used in the placer mining
industrial point source category.
    Passive treatment systems are currently used at a range of
construction sites as evidenced by the information contained in the
record. EPA has determined that a numeric limitation is achievable
based on the performance of PTS measured by the data described in
Section IX.E and in the Development Document and the record. Multiple
studies performed by McLaughlin in North Carolina have demonstrated the
effectiveness of passive approaches in reducing turbidity in stormwater
discharges from construction sites. Many of McLaughlin's studies were
performed on linear transportation projects for the North Carolina
Department of Transportation in piedmont areas of the State. Another
researcher, Warner, evaluated several erosion and sediment controls at
a full-scale demonstration construction site in Georgia. Additionally,
there were several studies conducted in New

Zealand on the effectiveness of flocculants and coagulants at improving
settling at transportation and residential projects. See Section IX.E
for a more detailed discussion of these studies. Adding flocculants or
polymers to aid in sediment removal are also routinely used a drinking
water plants to treat their source water. Polymer aided settling has
also been used in placer mining to treat effluent.
    In the proposal, EPA provided data on PTS and solicited comments on
the pollutant removal effectiveness, effluent quality attainable and
the technical basis for establishing a particular numeric turbidity
limitation for C&D sites based on passive treatment. See 73 FR 72562,
72580-82, 72610-11. Commenters provided additional data and papers on
PTS and EPA identified additional data on PTS (see the chapter 6 of the
TDD for a description of the data EPA has used as a basis for the
numeric limitation). EPA also obtained additional data from vendors on
ATS, the first component of which, namely polymer-assisted settling,
has been used, in combination with data available at the time of
proposal, as a basis for the numeric limitation (see Chapter 6 of the
TDD). A technology is ``available'' even if it is not widely or
routinely used as long as the technology is used at some facilities, a
pilot plant or is adequately available. See e.g., American Frozen Foods
v. Train, 539 F.2d 109 (D.C. Cir. 1976) (BAT was based on two exemplary
plants); Ass'n of Pacific Fisheries v. EPA, 615 F.2d 794, 816 (9th Cir.
1980) (legislative history indicates BAT can be established based on
statistics from one plant); FMC Corp v. Train, 539 F.2d 973 (4th Cir.
1976) (BAT limitations based on single pilot plant and a few exemplary
plants); Kennecott v. EPA, 780 F.2d at 458 (Congress required EPA to
search out BAT and to strive for zero discharge. BAT was based on two
plants). The data and information in the record on the use of these
technologies to control stormwater discharges support EPA's
determination that a well designed and maintained PTS on varying types
of construction sites in several areas of the country will consistently
achieve a numeric limitation and is thus technologically available. The
data and studies in the record show that these technologies have been
used in areas of the country with different rainfall patterns and soil
types. Locations of the studies include the Pacific Northwest, North
Carolina, and Georgia, as well as outside the U.S. (including New
Zealand). In addition, these technologies have been implemented on
different project types, including transportation, institutional and
residential construction.
    The Agency also examined the use of these technologies to control
sediment, turbidity and other pollutants in other industries. At least
six federal circuit courts have upheld EPA's use of transfer of
technology in the context of the CWA when promulgating ELGs and NSPSs,
concluding that effluent limitations may be based on a technology which
has been demonstrated outside the industry, if that technology is
transferable to it. See e.g., CPC International v. Train, 515 F.2d
1032, 1048 (8th Cir. 1975); Kennecott v. EPA, 780 F.2d 445, 453 (4th
Cir. 1986); CHS v. EPA, 553 F.2d 280, 285-287 (2d. Cir. 1977); Ass'n.
of Pacific Fisheries v. EPA, 615 F.2d 794, 817 (9th Cir. 1980).
    EPA examined the use of polymer-aided settling that is used in the
placer mining industry to treat effluent from the mining facilities.
Placer mining extracts gold from alluvial deposits. Excavation often
uses water as the means to disturb the sediments allowing the gold to
be extracted. The wastewater generated with placer mining contains the
sediment that has been separated from the gold. Though the water used
during the gold extraction process is not ``stormwater,'' the water
during the mining process acts in a similar manner as stormwater as it
detaches, erodes and dislodges the soil and discharges sediment,
turbidity and other pollutants from the facility. The placer mining
effluent guidelines (40 CFR part 440 subpart M) established limitations
for settleable solids based on simple settling for a minimum of 4
hours. While developing the placer mining effluent limitations
guidelines, EPA conducted treatability studies on the effectiveness of
simple settling and chemically-aided settling (polyethylene oxide (PEO)
and PEO with polyelectrolyte). Settleable solids, TSS and turbidity
were measured in these studies. EPA has examined the data from these
studies to evaluate the effectiveness of settling and polymer aided
settling applicable to the C&D point source category. EPA considers
this treatment performance data to be appropriate because both placer
mining and C&D involve significant disturbance of soils and placer
mining process wastewater has similar characteristics to stormwater
from construction sites. Untreated wastewater in the tests contained
concentrations of TSS ranging from 3,585 mg/L to 161,700 mg/L with
turbidity ranging from 2,450 to >80,000 NTU. After simple settling for
6 hours the concentrations of TSS dropped to between 28 mg/L and 26,235
mg/L while turbidity decreased to between 35 to 35,000 NTU. In the
tests where polyelectrolyte was added, initial TSS concentrations
ranged from 869 to 55,340 mg/L while turbidity ranged from 1,680 to
42,500 NTU. After 6 hours of settling, the TSS in the polyelectrolyte
samples ranged from 2 to 23 mg/L while turbidity ranged from 5 to 78
NTU. Notable also was that turbidity had decreased to between 13 and 97
NTU after only one hour of settling in these samples. Similar results
were reported for PEO with initial turbidity ranging from 1,235 to
39,500 and results after 6 hours ranging from 51 to 140 NTU (See DCN
42103, 1986 Alaskan Placer Mining Study Field Testing Program Report).
    EPA acknowledges that the placer mining treatment data was specific
to that industry. There may be other distinctions between the treatment
evaluated there and the technology in today's rule (e.g., the placer
mining data is based on enhanced settling using a polyelectrolyte and a
polyelectrolyte with a polymer only, as opposed to a full range of
passive treatment techniques relied upon in today's rule). Nonetheless,
the technology (chemically-enhanced settling) and the materials (water
containing dirt, rock, sand and similar materials) are fundamentally
similar and support EPA's conclusion that this type of well-
demonstrated treatment technique can reliably achieve low turbidity
levels in sediment bearing waste streams. This data demonstrates that
simple settling or enhanced settling is capable of achieving the
limitation.
    The data in the record on the use of PTS at construction sites
supports EPA's determination that a well designed and maintained
passive treatment system will consistently achieve the limitation and
is thus technologically available. The data in the record on the use of
enhanced settling at placer mining facilities supports EPA's
determination that PTS will consistently achieve the limitation in
discharges associated with construction activity and supports PTS being
technologically available.
    Besides the use of PTS, owners and operators will often times be
able to rely on non-numeric effluent limitations or BMPs, without the
use of polymers of flocculants, to meet the limitation. For example,
Horner et al. (see NRC at pg. 445 and DCN 01350) showed that a
turbidity limitation of 25 to 75 NTUs can be consistently met on
highway construction sites in Washington. See also discussion of Warner
and Collins-Camargo earlier (DCN 43071). Owners or operators can also
choose to modify their site planning, construction

operations or the processes in which the construction activity occurs,
such as changing the way the site is graded so that stormwater is
directed to areas where it can infiltrate. Also, if a vegetated area is
available, owners or operators can choose to utilize this area for
dispersion of the stormwater. The Agency may base BAT and NSPS
limitations and standards upon effluent reductions attainable through
changes in a facility's processes and operations, as are available to
owners and operators of construction sites. See Texas Oil & Gas Ass'n
v. EPA, 161 F.3d 923, 928 (5th Cir.1998). In addition, owners or
operators have the option to phase their construction activity or limit
the amount of land disturbed at one time in a manner such that the
numeric limitation would not apply to their construction activity.
Construction site owners or operators can avoid the application of the
numeric limitation in Option 4 to their discharges altogether if they
limit construction activity so that less than 10 acres are disturbed at
any one time.
    EPA's analysis shows that the technologies that form the basis of
Option 4 can consistently meet the limitation.
    In addition, the non-numeric effluent limitations of Option 4 are
technically available. These non-numeric effluent limitations represent
the average of the best performance of construction sites across the
country. See discussion of BPT in section III.D.1. As BAT represents
best available technology, they are also technologically available.
    In considering economic impacts, EPA's analyses show that the
requirements of Option 4 are economically achievable (BAT) and will not
pose a barrier to entry (NSPS). Under the CWA, in the effluent
guidelines program, EPA traditionally assesses the economic impact on
the industry as a whole, by looking at what percentage of facilities
would close or face a barrier to entry as a result of the costs of the
regulatory requirements and any resulting loss of employment.
    EPA estimates that out of the 82,000 firms expected to be affected
by this regulation, 147 firms or 0.2 percent, may close as a result of
the requirements. This closure estimate is based on the assumption that
some of the costs associated with this regulation will be passed on to
the customers of these firms. Based on the typical number of employees
working for these firms, EPA estimates 7,257 job losses associated with
these closures, out of total in-scope employment of 1.85 million. As
discussed in section XII.D, construction firms routinely expand and
contract their workforce in response to work load and as a result many
workers laid off when a firm closes are rehired by new and other
existing more financially healthy firms. Therefore, job losses due to
firm closures are in many cases a temporary displacement of the
workforce as compared to other industrial point source categories. The
construction industry is a highly dynamic industry that is
characterized by many small firms with a relatively high turnover that
expand and contract their level of activity readily in response to
changes in market conditions.
    The relatively high rate of entry and exit in the construction
industry, compared to other industries, suggests barriers to entry are
normally low. Option 4 is not likely to put new firms at a disadvantage
as both existing and new firms will need to meet the same requirements
for each new project begun. Existing firms are likely to have more
assets than new firms and therefore may be able to use more of their
own financial resources to finance a new project. The greater the
compliance costs in comparison to baseline assets the more likely the
rule would pose a barrier to new entrants. EPA assessed the increase in
financing requirements in relation to typical baseline assets for the
different firm revenue categories, and under Option 4 no firm category
would face financing requirements greater than 4.1% of baseline assets.
EPA does not consider Option 4 to pose a barrier to entry for new firms
into the marketplace. For a more detailed discussion see Section XII
below.
    Option 4 is projected to have a total industry compliance cost,
once fully implemented in NPDES permits and the industry has returned
to normal levels of construction activity, of $953 million per year
(2008 $). Most C&D sites are permitted under general permits, so this
rule will not be fully implemented until all state and EPA general
permits have expired and new general permits are issued that
incorporate the Option 4 requirements, which will take approximately 5
years after the effective date of this rule. Costs in the first year
(2010) are estimated to be approximately $8 million, and annualized
costs for the first 10 years after promulgation are estimated to be
$577 million (see Table X-2). Given the size of the industry and the
current annual value of construction activity of $960 billion (July,
2009), EPA has determined that this cost, which represents less than
one tenth of one percent of the current total value of annual
construction activity, can be reasonably borne by the industry.

                                                   Table X-2--Option 4 Annual Compliance Cost by Year
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Compliance year
---------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  2010     2011     2012     2013     2014     2015     2016     2017     2018     2019
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annual Compliance Cost (Millions).............................       $8      $63     $204     $538     $810     $834     $859     $885     $911     $938
--------------------------------------------------------------------------------------------------------------------------------------------------------

    These economic impacts are well within the range of impacts EPA has
imposed on other industries subject to ELG and NSPS rulemakings.
Congress expressly considered BAT and NSPS to be technology-forcing and
that in striving towards the ambitious goals of the CWA either BAT or
NSPS may, and likely will, result in some economic impacts to a portion
of an industry. See e.g., American Iron & Steel v. EPA, 526 F.2d 1027,
1052 (3d. Cir. 1975); Weyerhaeuser v. Costle, 590 F.2d 1011, 1026 (D.C.
Cir. 1978). Based on the traditional factors EPA considers under the
CWA when promulgating effluent limitations guidelines and standards the
Agency determined that Option 4 is economically achievable and will not
pose a barrier to entry. For a more complete discussion of EPA's
economic impact analysis see Section XII of this notice.
    Under the Regulatory Flexibility Act (RFA), EPA also considered the
impact to firm revenues for Option 4, at full implementation under
normal levels of construction activity. EPA evaluated impacts of the
rule on small firms. EPA considers the number of firms where the costs
to those firms exceed 1 percent and 3 percent of revenue. Under Option
4, there are no firms, either small or large, that are expected to
incur compliance costs exceeding 3 percent of their revenues, while
only 230 small firms (0.03% of in-scope firms and 0.84% of those
incurring costs) are expected to incur costs exceeding 1

percent of their revenues. Another measure of economic stress
considered by EPA is the estimated change in important firm financial
metrics, such as the ratio of pretax income to total assets. For this
option, a total of 169 out of 82,000 firms expected to be affected by
this regulation are estimated to incur financial stress as a result of
regulatory requirements, which represents 0.2 percent of in-scope
firms. These impacts are not necessarily additive with estimated 147
firm closures, mentioned previously, as they evaluate different aspects
of a firm's financial viability, and the same firm may experience more
than one measure.
    EPA found the non-water quality environmental impacts associated
with Option 4 to be minimal and acceptable. The non-water quality
environmental impacts associated with the BPT effluent limitations are
negligible as there is little incremental energy expended in the
implementation of the erosion and sediment controls, since these types
of controls are already being implemented by the majority of
construction sites nationwide. Depending on the particular polymer or
flocculant used, these solids are typically utilized as fill material
on the construction site. If they cannot be used as fill, then they
would be treated as municipal solid waste. However, EPA would expect
permittees to choose polymers or flocculants that would allow for use
of removed solids on-site
    EPA considered site size thresholds smaller than 10 acres for the
applicability of passive treatment systems and a numeric effluent
limitation and associated monitoring requirements. While EPA does not
have information to indicate a numeric effluent limitation for
stormwater discharges is not feasible for smaller construction sites,
EPA has determined that a site size threshold below 10 acres disturbed
at one time does not at this time represent BAT and NSPS in recognition
of other relevant factors, such as the fact that this is the first time
EPA has required an enforceable numeric effluent limitation for
stormwater discharges from construction sites nationwide, the increased
burden on the permitting authorities, and that construction sites less
than 10 acres are more likely to be operated by small businesses.
    EPA recognizes that meeting a numeric limitation is a significant
change for this industry. A 10-acre threshold of land disturbed at one
time will result in the numeric effluent limitation for turbidity and
the associated monitoring requirements applying to a very substantial
number of constructed acres of land per year. EPA has estimated that at
a threshold of 10 acres disturbed at one time, 623 thousand acres and
more than 21,000 projects annually will be subject to the numeric
effluent limitation. Thus, EPA has determined the final rule would
result in the numeric effluent limitation and monitoring requirements
applying to an estimated 73% of the constructed acres per year. If EPA
were to lower the threshold of land disturbed at one time to below 10
acres, the final rule would significantly increase the number of
projects subject to the numeric effluent limitation. As stated above,
at a 10-acre threshold, about 21,000 projects are subject to the
numeric effluent limitation; however, if the Agency were to lower the
threshold to, for example, 5 acres, the number of construction projects
climbs to 37,000 projects; and at 1 acre, the number of construction
projects would jump to 84,000 projects, a four-fold increase in covered
projects compared to a 10-acre threshold. EPA received comments from
state permitting authorities concerned about the potential increased
burden a numeric effluent limitation may have if it were applied to all
construction sites. State permitting authorities must oversee
incorporation of the final rule into their NPDES permits, in addition
to providing logistical and technical support to permittees subject to
the new requirements. While the final rule is not mandating specific
reporting requirements, EPA expects permitting authorities to develop
requirements in their NPDES permits for frequent reporting to assist in
compliance monitoring and program development. The permitting authority
will have to manage the reported effluent data and discharge monitoring
reports. EPA considered the significant further progress that applying
a numeric effluent limitation based on passive treatment systems to 73%
of the constructed acres would have in meeting the goals of the CWA in
combination with the likely increased workload to permitting
authorities, especially during a unique period of time when resources
may be an issue for permitting authorities.
    Additionally, EPA considered that construction sites less than 10
acres are more likely to be operated by small businesses. Larger
construction firms, who tend to operate on larger sites, will likely
have in-house expertise, while smaller construction firms may need to
rely on hiring consultants to implement the passive treatment systems
in order to meet the numeric effluent limitation. Based on comments EPA
received, the Agency has some concerns regarding the expertise at the
small construction firm level and, given the size of the construction
industry, the availability of the support industries for small
construction sites. The concern is that the support industries for
small construction sites, such as consulting firms and erosion and
sediment control service providers, will not be available, especially
as the entire industry adjusts to the new requirements, to provide the
level of support needed for these smaller sites to effectively
implement passive treatment systems to meet the numeric effluent
limitation. If the threshold was below 10 acres disturbed at one time,
an additional 63,000 sites, under a 1-acre threshold, or an additional
15,000 sites, under a 5-acre threshold, may need outside support for
passive treatment systems. EPA considered the issue of small
businesses' operation of small sites, the availability of expertise for
small sites that is necessary to meet a numeric effluent limitation and
the resulting questions raised as to whether passive treatment systems
are available for construction sites with less than 10 acres disturbed
at one time.
    In sum, after consideration of all the relevant factors in CWA
sections 304(b) and 306(b), EPA has determined that the selected option
is technologically available, economically achievable for the industry
as a whole, poses no barrier to entry, has acceptable non-water quality
environmental impacts and is BAT and NSPS for this point source
category. The selected option accommodates the concerns of the
regulated community and permitting authorities about the practicalities
of meeting a numeric effluent limitation. This rule reflects a new
generation of controls and approach to managing stormwater discharges
from C&D sites, with objective and enforceable limitations based upon
demonstrated technologies that this industry as a whole can achieve and
afford.
2. Numeric Limitations
    Numeric effluent limitations are feasible for discharges associated
with construction activity. Numeric effluent limitations are
appropriate on a nationwide basis for some construction sites and in
this case are the best way to quantifiably ensure industry compliance
and to make reasonable further progress toward the CWA goal of
eliminating pollutants into the nation's waters. Numeric effluent
limitations are an objective and effective way for the permitting
authority to implement, and the regulated industry to comply with, the
technology based requirements for

this point source category. Numeric limitations put the owner and
operator, the permitting authority and the public on notice as to what
is required, thereby facilitating effective permit development and
management of stormwater discharges associated with construction
activity, in order to further the objectives of the CWA.
    EPA has in the past indicated that numeric limitations for
discharges from C&D sites might not be feasible. Over the last several
years, additional data and information has become available indicating
that a numeric limitation is technically available and is appropriate
for some sites. Several states have recognized that current BMPs used
at construction sites are not always able to meet water quality
objectives. Therefore, several researchers (such as McLaughlin, Warner
and Horner) have investigated improved approaches to managing
construction site stormwater. Their research has demonstrated that the
performance of current BMPs can be improved and that effluent quality
can be substantially improved. In addition, several states have
incorporated action levels into their permits, so owners and operators
of construction sites have experience with sampling stormwater
discharges and analyzing for turbidity. In addition, California has
recently established effluent limitations for some sites within the
State, and dischargers within the Lake Tahoe basin have been subject to
numeric limitations for some time. The industry in general has become
more aware of the importance of turbidity control and has developed a
number of innovative approaches to improve turbidity removal. Also, a
substantial vendor base has developed in recent years that offer a
range of expertise and approaches for controlling turbidity. In
addition, permittees have many choices regarding when land disturbing
activities take place and how they decide to conduct land disturbing
activities on a particular site that have a pronounced effect on the
amount of sediment generated, and subsequently the amount of sediment
and other pollutants requiring management. Consideration of these
factors during the planning phases of projects will significantly
influence the level of control needed, and the feasibility of meeting a
limitation.
    Not withstanding a heavy reliance on non-numeric limitations in the
past, the use of numeric effluent limitations by EPA in national
rulemakings to control stormwater discharges has precedent in a number
of contexts. Industries that have exposed areas devoted to production
or material storage often have numeric limitations that apply to
stormwater discharges from these areas. EPA has promulgated at least
eight different effluent limitations guidelines for industrial point
source categories that address stormwater or a combination of
stormwater and process wastewater with numeric effluent limitations.\1\
---------------------------------------------------------------------------

    \1\ See 40 CFR part 411 (Cement Manufacturing); 40 CFR part 418
(Fertilizer Manufacturing); 40 CFR part 419 (Petroleum Refining); 40
CFR part 422 (Phosphate Manufacturing); 40 CFR part 423 (Steam
Electric); 40 CFR part 434 (Coal Mining); 40 CFR part 440 (Ore
Mining and Dressing); and 40 CFR part 443 (Asphalt Emulsion).
---------------------------------------------------------------------------

    In addition to numeric limitations being utilized for stormwater
discharges in other industrial categories, several states have effluent
limitations or action levels or benchmarks (hereinafter, benchmarks)
for stormwater discharges associated with construction activity. A
benchmark is a numeric monitoring requirement where discharges must be
sampled to determine whether they meet a certain level of pollutant(s)
in the discharge. For example, the State of Oregon requires
construction sites to monitor, and the permit contains a 160 NTU
benchmark for sites discharging to a CWA section 303(d) listed
waterbody or a waterbody with a TMDL for sediment and turbidity. The
State of Georgia has turbidity benchmarks that are a function of the
construction site size in relationship to the watershed size.
    The only practical difference between a numeric effluent limitation
and a benchmark is that a violation of a benchmark, in and of itself,
is not a violation of a NPDES permit. If a benchmark is exceeded,
generally, the enforceable requirement is for the discharger to contact
the permitting authority, examine its BMPs, and implement additional
controls, if necessary. A benchmark requires similar types of site
planning, employee education, firm resources, monitoring and sampling,
design, installation and maintenance of erosion and sediment controls
and compliance with other non-numeric effluent limitations, and
application of other passive treatment technologies as are necessary to
meet a numeric limitation.
    Some commenters argued for a benchmark as opposed to a numeric
turbidity limitation due to the variable nature of stormwater and after
the comment period industry stakeholders stated that they were
supportive of a benchmark approach, albeit at a higher NTU level. EPA
believes that benchmarks can be an important tool for permitting
authorities and for permittees. However, numeric limitations are
feasible and appropriate for larger C&D sites on a nationwide basis and
the feasibility of using a benchmark approach is comparable to the
feasibility of meeting a numeric effluent limitation. EPA does not
believe that a benchmark approach would represent BAT and NSPS at the
national level. Technologies and practices that can achieve numeric
effluent limitations for stormwater discharges are technologically
available and the Agency finds no reason to rely on benchmarks as
opposed to numeric effluent limitations in this case. EPA recognizes
and has considered the issue of variability of stormwater discharges at
C&D sites and has included several provisions in the rule to address
this issue. First, today's numeric limitation does not apply on days
when total precipitation in that day is greater than the local 2-year,
24-hour storm event. As stated below in Section XIX.A, the reasoning
behind this exemption is that for larger storm events, controls may be
overwhelmed by the large amount of stormwater and a numeric limitation
may be more difficult to meet. Additionally, as discussed below, the
numeric turbidity limitation is a daily maximum, meaning an owner or
operator will not be in violation of the limitation if individual
samples of their discharges exceed the limitation, as long as the
average of the samples taken over the course of a day are below the
limitation.
    In addition to the use of benchmarks, at least one state has state-
wide numeric effluent limitations for discharges associated with
construction activity. The State of California has an enforceable
numeric effluent limitation of 500 NTU in its construction general
permit for high risk sites. Also, states have set numeric turbidity
limitations for specific areas (such as the Lake Tahoe Basin), or for
specific projects.
3. Rationale for Rejecting Options 1, 2 and 3 as the Technology-Basis
for BAT and BADT for NSPS
    EPA rejected Option 1 as the basis for BAT and BADT for NSPS
because there are technologies that remove greater levels of pollutants
from stormwater discharges from C&D sites than Option 1 that are
technologically available, economically achievable, pose no barrier to
entry and have acceptable non-water quality environmental impacts, thus
Option 1 is not BAT and BADT for NSPS.
    EPA rejected Options 2 and 3 for numerous reasons. For Option 2 and
3 EPA believes that the use of ATS is likely to influence the ability
of site planners to select stormwater management controls that can
infiltrate

and manage stormwater on-site through green infrastructure practices
because ATS typically requires the use of a centralized drainage system
and large stormwater basins. Option 3 would present an even larger
disincentive to the use of infiltration and retention practices because
of the larger number of sites that may need to use larger basins.
    EPA is concerned that basing a numeric limitation on ATS is likely
to present a disincentive for site planners to select controls that may
be more effective from a hydrologic standpoint to maintain the
predevelopment hydrology of the site. In particular, ATS would require
larger basins than what may be required under existing state permits.
For example, EPA estimates that a construction project on a 17-acre
site in Alabama would need a basin providing approximately 200,000
cubic feet of storage to support application of ATS. This is almost
three times larger than the sediment basin that EPA estimates may be
required on this same project under the Alabama CGP. Since it would be
much more expensive to decommission this larger basin, this presents an
incentive for the developer to retain this basin as part of the
permanent stormwater management controls because the cost of
retrofitting this basin would likely be cheaper than installing
distributed runoff controls, such as rain gardens, which EPA views as
significantly more effective at managing stormwater on the development
after construction activity has ceased. As discussed at length in the
NRC report noted above, the use of retention, infiltration and other
low-impact development techniques is preferable from a hydrologic
standpoint to maintain predevelopment hydrology than detention through
the use of a sediment basin. Passive treatment systems do not have
these same limitations as ATS, since there is more flexibility in the
selection of controls. By utilizing passive treatment systems, a
sediment basin may not be required, and the site planner may be more
inclined to use distributed runoff controls, such as rain gardens,
instead of converting the sediment basin into a permanent stormwater
management pond. Even where a basin is needed, it may be a smaller
basin than would be needed for a full ATS. As discussed in Section
VII.A, there is also a concern that was raised by commenters on the
reliance on ATS due to the unique characteristics of linear projects.
Similar to what was discussed above, passive treatment systems will
provide owners and operators of construction sites the flexibility in
the selection of controls to include site specific conditions,
including right-of-way constraints.
    Many states and municipalities are moving in the direction of
requiring stormwater discharges from newly developed and redeveloped
sites to mimic the hydrology that would have occurred on the site prior
to the site being developed. These techniques not only eliminate or
reduce stormwater discharges from newly developed or redeveloped sites,
they can be designed to prevent stream bank and bed erosion, help
recharge groundwater, conserve energy, and mitigate urban heat island
impacts. As these practices can provide various environmental benefits,
these important environmental outcomes have been factored into EPA's
options selection process. As discussed in Section VI, EPA recognizes,
as the NRC report concluded, that the current regulatory approach by
EPA under the CWA is not adequately controlling all sources of
stormwater discharges that are contributing to waterbody impairment. As
a result, EPA has committed to and begun a rulemaking addressing
stormwater discharges from newly developed and redeveloped sites under
CWA section 402(p). EPA has published a draft Information Collection
Request, 74 FR 56191 (October 30, 2009) for public comment seeking
information and data to support the rulemaking.
    Passive treatment systems are able to provide a high level of
pollutant reduction at a significantly lower cost than active treatment
systems. In particular, Option 2 would have cost about $4.9 billion and
removed 70% of the sediment discharged from construction sites. This is
in contrast with a $0.95 billion cost with 77% sediment removals for
Option 4. While Option 3 achieves somewhat greater removals (87%) it
comes at a very high cost ($9 billion).
    In rejecting ATS as BAT and NSPS in the final rule, EPA also
considered the fact that as discussed above EPA is conducting a
rulemaking to address stormwater discharges from development that is
likely to impose additional costs on the construction industry. EPA has
just begun the rulemaking process for that rule, thus the Agency has
not quantified the costs, but the Agency is concerned about the
potential additive costs of choosing ATS as BAT and NSPS in this final
rule in combination with the potential costs of this new stormwater
rule. This was a similar consideration by EPA in the Offshore Oil & Gas
ELG where EPA rejected the most stringent option in part because of the
potential for the same industry to be required to bear additional costs
in a subsequent rule. See 58 FR 12454, 12483 (March 4, 1993).
    Although EPA is rejecting ATS as a basis for BAT and NSPS
nationally, ATS is an effective and important technology that has broad
applicability for construction sites. ATS was applied to construction
site discharges initially as a means of addressing water-quality
concerns, such as discharging stormwater to high-quality receiving
waters with low background turbidity. Indeed, in many areas where ATS
use has been most prevalent (such as in the States of California,
Washington and Oregon), construction activities are taking place in
areas where the receiving waters have background turbidity of only a
few NTUs and where sensitive or endangered species are present. In
these cases, the use of ATS has allowed construction activity to occur
so that discharges are at or below the background turbidity levels in
the receiving waters. If not for ATS, it is unlikely that many of these
projects would have met water quality requirements if forced to rely on
conventional erosion and sediment controls.
    As stated above, EPA acknowledges that many state and local
governments have existing programs for controlling stormwater and
wastewater discharges from construction sites. Today's rule is intended
to work in concert with these existing state and local programs and in
no way does EPA intend for this regulation to interfere with existing
state and local requirements that are more stringent than this rule or
with the ability of state and local governments to promulgate new and
more stringent requirements. Today's rule is a floor, not a ceiling. To
make this point clear EPA included ``at a minimum'' language in the
regulation to highlight the fact that EPA does not want to prevent more
stringent state technology-based or other effluent limitations from
serving as CWA requirements in NPDES permits. This rule is establishing
the minimum technology required by construction operators. States and
EPA can also require more stringent limitations that are necessary to
meet water quality standards. CWA section 301(b)(1)(C). Where TMDLs for
sediment or turbidity are established, the use of ATS may be an
important tool to ensure water quality standards are met. States also
have the authority to require more stringent requirements under state
law under CWA section 510. Permitting authorities may establish more
stringent effluent limitations subsequent to promulgation of today's
regulation

based on the application of ATS, or other technologies, where
appropriate.
4. Definition of ``New Source'' for the C&D Point Source Category
    As stated above, EPA is selecting Option 4 as the best available
demonstrated control technology (BADT) for NSPS under section 306. At
proposal, EPA stated that it interpreted ``new source'' at CWA section
306 to not include stormwater discharges associated with construction
activity from C&D sites. EPA stated that it is a reasonable
interpretation of section 306 to exclude C&D sites from the definition
of ``new source'' because a construction site cannot itself be
constructed. The Agency found that if construction sites were intended
to be ``new sources'' it is illogical that there would be a separate
definition for ``construction'' or that there would be a requirement in
section 306 that ``sources'' be constructed prior to becoming ``new
sources.'' See 73 FR 72583. The result of this interpretation is that
no C&D sites would ever be new sources. However, the 2006 district
court order enjoins EPA to promulgate ELGs and NSPSs.
    In order to comply with the district court order, EPA proposed a
specialized definition of ``new source'' for purposes of part 450 as
any source of stormwater discharge associated with construction
activity that itself will result in an industrial source from which
there will be a discharge of pollutants regulated by a new source
performance standard in subchapter N. (All new source performance
standards promulgated by EPA for categories of point sources are
codified in subchapter N.) See 73 FR 72583. The definition of new
source would mean that the land-disturbing activity associated with
constructing a particular facility would itself constitute a ``new
source'' when the facility being constructed would be a ``new source''
regulated by NSPSs under section 306 of the CWA. For example,
construction activity that builds a new pharmaceutical plant whose
process wastewater is covered by 40 CFR 439.15 would be subject to the
NSPS under 40 CFR 450.24, as proposed, for its stormwater discharges
associated with the construction activity.
    Commenters raised numerous objections to the proposed ``new
source'' definition, arguing that the proposed definition is overly
narrow and there is no rational explanation for treating a C&D site for
a commercial facility as an existing source, while treating a C&D site
for a new iron and steel facility that happens to have NSPSs for its
process wastewater as a new source. EPA's proposed definition of ``new
source'' was the result of the difficult application of section 306 to
the unique nature of the C&D point source category compared to other
industrial categories. Section 306 was part of the 1972 amendments to
the CWA, when the focus was on industrial facilities that are
traditionally considered ``plants'' or ``factories,'' such as petroleum
refineries, power plants and heavy manufacturing. See e.g., 118 Cong.
Rec. 10201, 10208, 33747, 33760, 33763 (1972); A Legislative History of
the Water Pollution Control Act Amendments of 1972, 93d Cong., 1st
Sess. (Comm. Print 1973). However, the CWA has evolved since 1972, most
notably through the WQA of 1987 and the addition of a comprehensive
program to address stormwater discharges under section 402(p). As a
result, the nature and characteristics of the sources that EPA now
regulates under the NPDES program may not, and in the case of C&D
sites, do not, necessarily align themselves plainly with the provisions
of section 306: however EPA does not believe that this results in C&D
sites not being subject to section 306.
    After a careful review, based on comments received, EPA has decided
to reconsider its proposed definition of ``new source.'' EPA agrees
with commenters that it is not the best reading of section 306 for the
definition of ``new source'' for C&D sites to be dependent upon the
result of the construction activity or the activity that occurs on the
developed site. EPA recognizes there is difficulty in treating a C&D
site for a commercial facility not as a new source, while treating a
C&D site for a new iron and steel facility that happens to have NSPSs
for its process wastewater as a new source. Even within similarly
situated industrial categories, there may be facilities that have NSPSs
for their process wastewater and other facilities that do not, and that
fact is removed from the concerns of this rule regarding discharges of
turbidity, sediment and other pollutants associated with construction
activity. The concerns of this rulemaking and the nature of C&D sites
exist notwithstanding and independently of the nature of the developed
site and the activity on that site that leads to discharges of
pollutants after completion of construction activity.
    While EPA believes it is a reasonable interpretation of the CWA to
exclude C&D sites from the definition of ``new source'' based on the
text of section 306, the Agency has determined the better reading of
the statute is that C&D sites may be new sources. The term ``source''
is defined in 306(a)(3) of the CWA to mean ``any building, structure,
facility, or installation from which there is or may be the discharge
of pollutants.'' While it is not clear that a C&D site would be a
``building,'' ``structure,'' or ``installation,'' the regulatory
definition of ``facility'' means ``any NPDES `point source' or any
other facility * * * (including land or appurtenances thereto) that is
subject to regulation under the NPDES program.'' 40 CFR 122.2. Based on
the WQA of 1987, EPA promulgated the Phase I and Phase II stormwater
regulations which required NPDES permits for stormwater discharges
associated with construction activity. See 40 CFR 122.26(b)(14)(x) and
122.26(b)(15). C&D sites are point sources and subject to regulation
under the NPDES program due to their discharge of pollutants. Based on
EPA's regulatory definition, C&D sites are ``facilities,'' thus EPA
interprets them to be ``sources,'' as that term is defined under
section 306. The term ``construction'' is defined as any ``placement,
assembly, or installation of facilities or equipment (including
contractual obligations to purchase such facilities and equipment) at
premises where such equipment will be used, including preparation work
at such premises.'' CWA section 306(a)(5). The definition of
``construction'' is broad to include activities that occur, including
preparation work, placement of equipment and signing of contracts,
before actual construction activity, such as clearing, grading and
excavation occurs on the site. This broad, encompassing definition,
would allow an owner or operator to begin ``construction'' of the C&D
site without actually beginning construction activity. While it is
reasonable, based on a common sense understanding of the term, that an
owner or operator cannot construct a construction site as that term is
commonly used, ``construction'' is specifically defined in the CWA and
based on that broad definition it is a better interpretation of
``construction,'' that owners or operators of a C&D site can
``construct'' a C&D site within the meaning of the CWA as interpreted
by EPA. See 40 CFR 122.29(a)(4). Given the evolution of the CWA, as
discussed above and the focus of the CWA in 1972, it is not illogical
that there would be a separate definition for ``construction'' or that
there would be a requirement in section 306 that ``sources'' be
constructed'' prior to becoming ``new sources.'' EPA did not regulate
discharges associated with construction activity at that time, thus
there would be nothing illogical with including a separate definition
of

``construction.'' While section 306 and EPA's regulations on new source
determinations appear to emphasize permanent facilities as opposed to
relatively temporary sources like C&D sites, EPA is taking into
consideration this evolution of the CWA and viewing the statute as
whole in determining a reasonable and appropriate reading of section
306 and EPA regulations. ``New source'' means ``any source, the
construction of which is commenced after publication of proposed
regulations prescribing a standard of performance under this section
which will be applicable to such source * * *'' CWA section 306(a)(2);
40 CFR 122.2. As outlined above, C&D sites are ``sources'' and owners
and operators can construct C&D sites given the broad definition of
``construction,'' thus a C&D site may be a ``new source'' under section
306 and subject to NSPS.
    For purposes of this rule, EPA has defined ``new source'' as ``any
source, whose discharges are defined in 40 CFR 122.26(b)(14)(x) and
(b)(15), that commences construction activity after the effective date
of this rule.'' Under this definition, the only construction sites that
will not be ``new sources'' are those sites that commenced construction
activity before the effective date of this rule. The definition aligns
itself with the nature of construction sites, the opportunities to
utilize the most effective control technologies and Congress'
``recognition of the significantly lower expense of attaining a given
level of effluent control in a new facility as compared to the future
cost of retrofitting a facility.'' A Legislative History of the Water
Pollution Control Act Amendments of 1972, 93d Cong., 1st Sess. (Comm.
Print 1973) at 797. Congress ``recognized that new sources could attain
discharge levels more easily and at less cost than existing sources
which must be retrofitted * * * [and Congress] clearly expressed [a]
belief that it would be easier for new sources to attain a particular
level of effluent control than it would be for existing sources.''
American Iron & Steel v. EPA, 526 F.2d 1027, 1058 (3d Cir. 1975).
    EPA has the authority to provide specialized definitions of ``new
source'' to particular point source categories. See 40 CFR 122.29(b);
401.10. As stated above, the substantive standards for BAT and NSPS are
based on the best available technology or best available demonstrated
control technology which consider both the cost of achieving such
effluent reduction and any non-water quality environmental impacts and
energy requirements. See CWA sections 304(b)(2)(B) and 306(b)(1)(B).
For this final rule BAT is equal to NSPS.
    Some commenters raised the issue of the National Environmental
Policy Act of 1969 (NEPA) 33 U.S.C. section 4321 et seq. and its
relationship to ``new sources.'' Pursuant to CWA section 511(c) the
issuance of a NPDES permit under section 402 for the discharge of any
pollutant by a ``new source'' as defined under section 306 may be
deemed a major Federal action significantly affecting the quality of
the human environment within the meaning of NEPA and would be subject
to the environmental review provisions of NEPA. The issuance of a NPDES
permit to a new source by an NPDES-approved state is not a federal
action; therefore, issuance of these permits is not subject to NEPA.
Forty-six (46) states have NPDES authorization. For the remaining four
states, tribal lands, territories, and other areas where EPA is the
permitting authority the issuance of any NPDES permit to a new source
is subject to the environmental review provisions of NEPA as set out in
40 CFR part 6. The vast majority construction sites in these remaining
jurisdictions obtain NPDES permit coverage for discharges associated
with construction activity under the EPA CGP. EPA intends to comply
with NEPA, as necessary, pursuant to the issuance of the EPA CGP.

XI. Methodology for Estimating Costs to the Construction and
Development Industry

    In developing today's final rule, EPA used numeric models to
estimate the costs of compliance with various regulatory options. This
approach was used to estimate the incremental costs associated with the
regulatory options at the state and national level. This approach is
the same as that used at proposal; however, EPA has updated various
models and estimates of costs as well as estimates of annual
construction activity, based on comments received as well as other
factors.
    For the proposal, EPA developed a series of nine model projects (3
site size categories and 3 project types). EPA estimated incremental
compliance costs for each of these model projects under the various
regulatory options and scaled costs to the national level. EPA used a
fixed project duration of nine months for each of the model projects as
a basis for estimating compliance costs. The annual amount of
construction activity was estimated based on the 1992 and 2001 National
Land Cover Dataset (NLCD) available at the time of proposal.
    For the final rule analysis, EPA also estimated project-level costs
for a series of model projects. The models vary by size (disturbed
acres), duration, and type of construction to establish the baseline
conditions for factors that can directly influence compliance costs and
firm impacts. EPA developed a set of model projects that includes 12
size categories and 12 duration categories. For costing purposes, EPA
made a distinction between building and transportation projects. The
linear configuration of many transportation projects requires
additional considerations for managing stormwater. However, EPA did not
consider residential and nonresidential projects of the same size and
duration to have appreciably different costs. These two project types
(building and transportation) were combined with the size and duration
categories to create 288 different model projects. These model projects
were then combined with a set of geographic conditions unique to each
state, based on a representative metropolitan area within the state,
resulting in 14,688 model projects (288 x 51). There were many factors
affecting model project cost for each option. The primary factor was
the set of applicable technologies and practices considered necessary
for meeting each option's regulatory requirements. The costs associated
with each set of technologies and practices varied by project size, but
they also vary by duration, state, and construction sector. For all
four options, the costs for projects under 10 acres were based on non-
numeric effluent limitations or BMPs and only varied by size. For
Option 1, projects above 10 acres were also assumed to rely upon non-
numeric effluent limitations or BMPs and costs only varied by size. For
Options 2, 3, and 4, projects that were required to meet numeric
limitations had costs that also varied by duration to reflect either
the application of PTS or ATS, as well as O&M costs and costs for
monitoring.
    In developing unit costs for each model project, EPA refined the
approach used at proposal. At proposal, EPA estimated annual rainfall
and runoff volumes on a per-acre basis for one indicator city in each
state. EPA estimated ATS treatment costs using an estimate of $0.02 per
gallon. For the final rule analysis, EPA again used rainfall data from
one indicator city in each state to estimate annual rainfall and runoff
volumes and determined ATS treatment system sizes (based on a design
flowrate) needed in each state for each of the model project site
sizes. Using data supplied from vendors on the unit cost of various ATS
treatment system components contained in the proposed rule record (see
DCNs 41130

and 41131), as well as the Development Document EPA estimated the one-
time and monthly recurring costs for deploying ATS in each state.
Monthly recurring costs included costs for operator labor, treatment
chemicals and fuel usage. Using the distribution of projects by site
size and duration in each state, EPA was then able to estimate the
costs to implement ATS for Options 2 and 3. EPA also estimated
incremental storage requirements to impound runoff prior to treatment
from the 2-year, 24-hour storm for each indicator city and added
additional storage costs if existing state sediment basin sizing
requirements were smaller than these volumes. EPA intended to use this
analysis at the time of proposal in order to compare results with the
$0.02 per gallon approach, but was unable to complete this analysis
prior to publication of the proposed rule. The information that EPA
used for this approach was, however, included in the docket (see DCN
51201) and commenters provided comment on this approach (See EPA-HQ-OW-
2008-0465-1360 in the rulemaking record).
    In developing costs for Option 4, EPA estimated the costs for
deploying liquid polymer dosing systems and for implementing fiber
check dams with PAM addition on sites. EPA also estimated monthly labor
needs for sampling personnel, as well as monthly operation and
maintenance costs for polymer dosing systems and for fiber check dam
replacement and PAM application. EPA then scaled costs to the state and
national level. EPA also estimated costs for firms to purchase
turbidity meters. Detailed results of this analysis are presented in
the Development Document.
    From Table XI-1 it is apparent that there was a wide range of
project costs. The $490 project cost reflects the use of BMPs on the
smallest model project, estimated to be 1.9 acres in size. The model
project with the highest cost, for options 2, 3, and 4 are all based on
the largest model project with the longest duration, 145 acres over
three years. The $390 thousand, under Option 4, represents a 145 acre
transportation project in Florida lasting three years, and the $5.5
million project, under Options 2 and 3, represents a three year 145
acre project in Louisiana.

                             Table XI-1--Range of Project Costs for the Four Options
----------------------------------------------------------------------------------------------------------------
                                                   Average cost     Median cost    Minimum cost    Maximum cost
----------------------------------------------------------------------------------------------------------------
Option 1........................................          $8,026          $5,296            $490         $44,832
Option 2........................................         328,322           5,296             490       5,501,864
Option 3........................................         399,371         224,541             490       5,501,864
Option 4........................................          42,207          28,330             490         389,786
----------------------------------------------------------------------------------------------------------------

    For estimating the total annual construction acreage in-scope, EPA
relied on industry economic data rather than the NLCD because recent
NLCD data is not yet available. EPA used historical construction
spending data to derive a long-term trend for construction activity.
This allowed EPA to base its estimates on normal industry conditions
rather than large fluctuations in activity seen in recent years. Next
EPA used data from the U.S. Housing Census, Reed Construction, and the
Federal Highway Administration to estimate the relationship between
construction spending levels and the average annual quantity of acres
developed. This relationship was then combined with the long-term trend
to project expected construction acreage for 2008 under normal
conditions (see Section XII for additional discussion of this
analysis).

XII. Economic Impact and Social Cost Analysis

A. Introduction

    EPA's Economic Analysis (see ``Supporting Documentation'')
describes the impacts of today's final rule in terms of firm closures
and employment losses, in addition to firm financial performance and
market changes. In addition, the report provides information on the
impacts of the rule on sales and prices for residential construction.
The results from the small business impact screening analysis support
EPA's implementation of the Regulatory Flexibility Act (RFA), as
amended by the Small Business Regulatory Enforcement Fairness Act
(SBREFA). Results from the government costs analysis support the
implementation of the Unfunded Mandate Reform Act (UMRA). The report
also presents identified, quantified, and monetized benefits of the
rule as described in Executive Order 12866.
    This notice includes related sections such as the cost-
effectiveness analysis in Section XIII, benefits analysis in Section
XVI, and benefit-cost analysis in Section XVII. In their entirety,
these sections comprise the economic analysis (referred to collectively
as the ``C&D economic analysis'') for the final rule. EPA's
Environmental Assessment provides the framework for the monetized
benefits analysis. See the complete set of supporting documents for
additional information on the environmental impacts, social costs,
economic impact analysis, and benefit analyses.
    The C&D economic analysis, covering subsectors that disturb land
(NAICS 236 and 237), uses information from, and builds upon, the 2002
final rule (67 FR 42644; June 24, 2002), the 2004 withdrawal of the
final rule (69 FR 22472; April 26, 2004), and the 2008 proposed rule
(73 FR 72562). In addition to CWA requirements, EPA has followed OMB
guidance on the preparation of the economic analyses for Federal