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New Federal Stormwater Management Rules for Construction Sites: How They Work and How to Cope
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August 2, 2010
By Kristin R. Robrock, Ph.D. and Peter Mesard, P.E.
Exponent, Inc.
and Christopher Marraro
The Environmental Protection Agency has issued regulations that, for the first time, impose performance-based standards and numerical effluent limits on stormwater discharges from construction sites (“Construction Rule”). 1/
This new rule, promulgated under authority of the Clean Water Act, is intended to control dispersed sources of pollution such as sediment and nutrients at sites that, although individually small, can cumulatively affect the quality of receiving waters.
EPA contends that uncontrolled runoff can greatly affect water bodies by decreasing water clarity, conveying toxic chemicals into waterways, increasing pathogen concentrations, increasing the need for dredging, and raising the cost of drinking-water treatment.
Previously, EPA’s stormwater rules controlled runoff that contained toxic chemicals such as metals and pesticides as well as oils and fuels. Now, EPA has determined that water quality is reduced by suspended sediments in stormwater runoff, negatively affecting ecosystems and beneficial uses. For this reason, EPA has promulgated the new regulations to reduce sediment releases to water bodies by an estimated 4 billion pounds a year. 2/
The Construction Rule took effect on February 1, 2010. After that date, all permits issued by EPA or authorized states must incorporate the final rule requirements.
The Construction Rule will affect more than 82,000 construction and engineering firms involved in heavy construction and commercial and residential development. The Construction Rule is complex and imposes detailed requirements on an industry that has been largely unregulated with regard to stormwater discharges. Those affected should review the regulation with their counsel and experts because, as with any new regulation, many practical compliance issues will arise. The balance of this article describes the rule and some practical methods for complying with it.
Why is Stormwater Runoff Important?
EPA contends that stormwater is a major concern on construction sites where soil is exposed, excavated, moved, graded and/or stockpiled. Rainwater collects particles of soil as it runs off these unvegetated and sometimes unstable areas, causing erosion and transporting sediment and/or nutrients into the stormwater system or open bodies of water.
If unmitigated, this sediment can clog storm sewers, fill lakes and river channels, and increase turbidity. With more than 80,000 sites undergoing construction activity each year, the effect of stormwater runoff on natural water bodies can be substantial. 3/
Much of the impact of this sediment is aesthetic -- muddy water is unsightly and can decrease property values. However, turbid water also can decrease the quantity of sunlight that penetrates to submerged plants in lakes and oceans, thereby potentially harming entire ecosystems. Drinking-water treatment is more difficult and expensive if the source water is turbid. Sediment can contain metals, toxic chemicals or pathogenic microorganisms, depending on the location of the construction site. Nutrients such as organics, nitrogen and phosphorus also are frequently carried by runoff and can cause excess algae growth and resulting loss of dissolved oxygen in the water, potentially resulting in fish kills.
EPA estimates that sediment loss from unvegetated construction sites can range up to 200 tons per acre per year. Suspended sediment concentrations in construction-site runoff can be as high as 160,000 mg/L (ppm). 4/ Poorly managed construction-site stormwater can produce serious environmental consequences. Frame 2, below, shows how a lake in Missouri was damaged by sediment runoff from a construction site, killing much of the aquatic life in the lake.
Deleterious effects of uncontrolled stormwater runoff from construction sites on receiving waters. Frame 1: Undisturbed lake waters. Frame 2: Subsequent impact of stormwater runoff from a nearby construction site. Frame 3: Fish kill resulting from runoff shown in Frame 2. Frame 4: Uncontrolled erosion at a recently graded site. (Sources: David Cozad, EPA Region 7; soilerosion.net/; Katharina Helming, ZALF; Exponent) Click on photos to enlarge
Regulatory History
To address impacts on water quality and ecosystems from stormwater runoff, the Clean Water Act was amended in 1987 to create the National Pollutant Discharge Elimination System (NPDES), which requires permits for stormwater discharges. In 1990, construction sites larger than 5 acres were added to the Industrial Activities category and were required to obtain NPDES permits. In 1999, the act again was modified to include construction sites larger than 1 acre.
NPDES requirements for construction sites include development and implementation of stormwater pollution prevention plans (SWPPPs). These stormwater management plans allow the operators to use their discretion in implementing best management practices (BMPs) that are most suitable to the particular site. These BMPs reduce erosion and prevent entrained sediment from being transported into storm sewers or into adjacent streams, rivers or lakes by using a variety of engineering controls.
In 2000, EPA began to investigate whether stormwater control measures were sufficiently protecting ecosystems and water supplies. EPA estimates that construction activities release an average of 5 billion pounds of sediment a year from a total of 853,000 acres. 5/
Because construction is not evenly distributed throughout the country, half of these activities from 1992 to 2001 occurred in only 5 percent of the watersheds, causing disproportionate impact. Interestingly, some of the fastest developing watersheds during that timeframe were not located in megacities but were in smaller cities such as Manchester, New Hampshire; Albany, New York; and Kansas City, Missouri. 6/
In 2002, EPA developed a series of proposals for stormwater management at construction sites that included more stringent effluent limits and performance standards, but in 2004 EPA decided that the then-current regulations still were sufficient. In 2006, the Natural Resources Defense Council, the Waterkeeper Alliance, and the States of Connecticut and New York sued EPA in the U.S. District Court for the Central District of California, claiming a violation of the Clean Water Act for not establishing discharge standards at construction sites. In September 2008, the U.S. Court of Appeals for the 9th Circuit affirmed the District Curt’s ruling and ordered EPA to issue new regulations that established discharge limits by December 1, 2009. Natural Resources Defense Council v. Environmental Protection Agency, 542 F.3d 1235 (9th Cir. 2008).
The New Construction Rule
The Construction Rule requires construction site owners and operators that disturb 1 or more acres to use best management practices (BMPs) to ensure that soil disturbed during construction does not pollute nearby water bodies.
For larger sites, the final rule establishes monitoring requirements, technology-based effluent limitations, and new source performance standards for the construction and development point-source category. In particular, the rule creates a minimum technology-based “floor” for turbidity values in stormwater runoff discharged to storm sewers and natural bodies of water for all states to meet.
Turbidity in water typically is measured as a function of the light scattering caused by suspended particles and is reported in units called nephelometric turbidity units (NTUs). Sediment concentrations in water also can be measured by filtering a water sample and weighing the collected sediment, but turbidity is much more readily and easily measured in the field with portable instruments.
The new regulations divide construction and development sites into two categories: Those in which fewer than 10 acres will be disturbed at a time, and those with more than 10 acres of disturbance. For sites smaller than 10 acres, the best practicable technology (BPT) currently available is required to mitigate stormwater runoff. Essentially, this requirement maintains the status quo because BPTs represent available and economically feasible technologies already in use to control stormwater runoff at the best performing construction sites around the country.
For sites larger than 10 acres, however, there is a substantial change in stormwater management requirements. In these cases, the best available technology economically achievable (BAT) is required, meaning that sediment concentrations in stormwater runoff now must be monitored and must meet new water quality numerical standards. Stormwater effluent may not exceed 280 NTUs on a daily basis on sites where 10 or more acres will be disturbed at a time.
This is a substantial change from the proposed rule in which EPA had proposed a limit of 13 NTUs for sites of 30 acres or more. For comparison, turbidity values of runoff from construction sites before the new regulation had ranged to more than 1,000 NTUs while runoff from undisturbed areas rarely exceeds 100 NTUs.
Currently, the California Environmental Protection Agency requires that stormwater runoff from construction sites larger than 1 acre not exceed 500 NTUs in most parts of the state. Limits down to 20 NTUs can be imposed for discharges to the Lake Tahoe Basin to protect the exceptional clarity of the lake water. Oregon limits stormwater effluent from construction sites to 160 NTUs. 7/
Permittees will have flexibility in meeting the numerical effluent limits. They can select management practices or technologies at each site so long as the practice or technology consistently meets the limitations and requirements of the permitting authority. In the next section, we describe some management methods and technologies that can be used to meet the permit requirements.
These monitoring and numeric effluent requirements are phased in under the rule. Sites that will disturb 20 acres or more will have 18 months from the effective date of February 1, 2010, to be brought into compliance (August 1, 2011). Sites of 10 to 20 acres will have four years to be brought into compliance with the rule (February 2, 2014). In determining the size of the disturbed area for compliance purposes, all land within the construction site is considered, whether or not such land is contiguous.
Besides numerical standards that must be met, the Construction Rule also prohibits certain types of runoff completely. These include washout from concrete trucks and other containers; washout from containers of paints and stuccos; and fuels, oils and curing compounds that contain toxic chemicals.
The final rule narrowed the requirements for linear construction sites (pipelines, underground cable installation, tunnels). Unlike the proposed rule, the final rule contains no requirements for sediment basins at linear construction sites. One other noteworthy issue regarding linear construction is that interstate natural gas pipeline projects that are under the jurisdiction of the Federal Energy Regulatory Commission are exempt from the monitoring requirements and numeric effluent limitations of the Construction Rule.
The Construction Rule requirements constitute a regulatory “floor” and not a “ceiling.” Most states have their own NPDES permit systems, and the state program can apply more stringent standards. The States of California, Georgia and Oregon already require monitoring and impose limits on numerical effluent concentrations for certain construction sites. On the other hand, EPA issues NPDES permits for several states (Idaho, Massachusetts, New Hampshire and New Mexico), the District of Columbia, several territories, federal facilities and Indian lands, and EPA will control the permit program for the Construction Rule in these jurisdictions.
Control of Stormwater Runoff
Engineering controls can be implemented to help meet these new standards. For starters, the simplest measure is to prevent sediment transport by controlling erosion. This can be done by minimizing earthmoving, grading and stockpiling of soils through appropriate design and scheduling.
Earthwork can be conducted in such a way as to minimize the area or volume of soils being disturbed at a time, and in some cases, many of these activities can be done during times of year when there is less precipitation. These disturbed areas can be quickly revegetated or covered with geotextiles, which substantially decreases the amount of sediment in runoff. In addition, the local topography and hydrology of the site can used to advantage by placing stockpiles in areas of the site where they are less susceptible to runoff or by rerouting stormwater runoff.
Where bare soils are exposed, it is critical to control erosion by minimizing stormwater velocities because fast-flowing water scours soil, picking up soil particles and forming gullies. Wattles or bales of hay can be placed across slopes to slow runoff. Certain chemicals, such as tackifiers, can act as a glue to hold soil particles together and reduce the potential for displacement by stormwater. Once sediment has been mobilized by runoff, it is important to prevent release of this sediment into adjacent storm drains or natural bodies of water. This can easily be accomplished by placing sand bags around storm drain inlets and installing silt fences and compost berms along receiving waters to induce deposition of the transported sediment on-site.
With the new numerical standards for larger construction sites, new control methods may needed if upstream methods are not sufficient to limit turbidity to less than the 280 NTU limit. Sediment traps and detention basins can be installed to collect stormwater and allow sufficient time for sediment particles to settle.
If runoff velocities still are too high for sediment to settle out, baffles and skimmers can be used to lengthen retention times in traps and basins. Coagulation and settling of soil particles in detention basins can be enhanced by addition of chemicals such as flocculants or by electrocoagulation, in which an electrical charge destabilizes particles, allowing them to stick together. Runoff also can be discharged into vegetated areas or sand berms, which act as natural sediment filters.
In implementing these new regulations, EPA created exceptions for large storm events, establishing that runoff from rainfall events that exceed the 2-year, 24-hour storm need not meet numerical effluent standards. The rationale is that these events are unlikely to occur during the duration of an average construction project and that most stormwater management systems are designed for the 2-year storm.
Frame 1: Examples of accumulated sediment in a storm sewer. Frame 2: Wattles placed on a slope to control erosion. Frame 3: Sand bags to protect a storm drain inlet (Source: Exponent). Click on photos to enlarge
Costs to Industry and the General Public
These new regulations do not come without additional costs to the construction industry for stormwater runoff mitigation and to the general public, which ultimately will bear the higher cost of development. EPA estimates that the construction industry will sustain, on average, an additional $42,000 in costs per project for monitoring effluent turbidity levels and implementing more effective stormwater management controls. EPA has estimated that the median home will increase in cost by $415. 8/
EPA is cracking down on violators. Although the new regulations do not estimate the fines likely to result from non-compliance with new standards, in past years many developers and construction projects have been fined for violating permit conditions or not having NPDES permits, with fines of up to $27,500 per day. 9/ A developer in St. Louis, Missouri, who violated stormwater management protocols at a variety of sites, polluting lakes and causing fish kills, was fined $590,000.
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For more information about the issues covered in this report, please contact Kristin R. Robrock of Exponent’s Oakland, California, office at 510-268-5003 or krobrock@exponent.com or Peter M. Mesard of Exponent’s Oakland, California, office at 510-268-5009 or pmesard@exponent.com.
ENDNOTES
| 1/ | U.S. Environmental Protection Agency, “Effluent Limitation Guidelines and Standards for the Construction and Development Point Source Category; Final Rule,” 74 Fed. Reg. 62,996 (Dec. 1, 2009), codified at 40 CFR Part 450.
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| 2/ | Id.
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| 3/ | U.S. Environmental Protection Agency, “Economic Analysis of Final Effluent Limitation Guidelines and Standards for the Construction and Development Industry,” November 23, 2009.
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| 4/ | U.S. Environmental Protection Agency, “Environmental Impact and Benefits Assessment for Final Effluent Guidelines and Standards for the Construction and Development Category,” November 2009.
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| 5/ | U.S. Environmental Protection Agency, “Development Document for Final Effluent Guidelines and Standards for the Construction and Development Category, Appendix E,” November 2009.
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| 6/ | Endnotes 3, 5, supra.
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| 7/ | Endnote 1, supra; California Regional Water Quality Control Board, Board Order No. R6T-2005-0007, Updated Waste Discharge Requirements and National Pollutant Discharge Elimination System General Permit No. CAG616002 for Discharges of Storm Water Runoff Associated with Construction Activity Involving Land Disturbance in the Lake Tahoe Hydrologic Unit, 2005.
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| 8/ | Endnote 3, supra.
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| 9/ | U.S. Environmental Protection Agency, Office of Enforcement and Compliance Assurance 2001, “Enforcement Alert,” January 2001.
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