Energy and Environment Monitor November 28, 2008, EPA proposed technology-based Effluent Limitations Guidelines and New Source Performance Standards1 for the Construction and Development (C&D) point source category (73 FR 72561-72614; 40 CFR Part 450). The C&D point source category covers: Construction of Buildings (NAICS 236) including residential, nonresidential, industrial, commercial and institutional building construction; Heavy and Civil Engineering Construction (NAICS 237) includes utility systems construction (water and sewer lines, oil and gas pipelines, power and communication lines); land subdivision; highway, street, and bridge construction; and other civil engineering construction.
The proposed ELG requires construction sites to implement a range of erosion and sediment control measures to control pollutants in stormwater discharges. In addition, for sites of 30 acres or larger located in areas of the country with high rainfall intensity2 and soils with high clay content3, stormwater discharges from the construction site would be required to meet a numeric limit on the allowable level of turbidity, which is a measure of sediment in the water . EPA requests comments by February 26, 2009 on the proposed rule addressing alternate options with a different numeric limit based on different technologies, as well as treatment technologies, costs, loading reductions, and economic achievability.
The proposed rule is intended to work in concert with existing state and local programs - usually via the NPDES General Permit Program -- adding a technology-based "floor" that establishes minimum requirements that would apply nationally. EPA estimates that this proposed rule would cost $1.9 billion per year with annual monetized benefits of $332.9 million.
The proposed rule would require all construction sites disturbing one acre or greater [40 CFR §122.26(b) (15)], including sites less than one acre that are part of a larger common plan of development or sale whose total land disturbing activities total more than an acre, to implement a range of erosion and sediment control best management practices (BMPs) and pollution prevention practices to reduce pollutants in stormwater discharges. [Same scope of coverage as existing rule 40 CFR 122.26(b)(14) (x) and (15)].
Erosion BMPs are to minimize dislodging and mobilizing of sediment particles and require stabilization of disturbed soils immediately when earth disturbing work has permanently or temporarily (earth disturbing work has been stopped on that portion of the site and will not resume for a period exceeding 14 calendar days) ceased ; control stormwater volume and velocity to prevent channel, stream bank and outlet erosion; minimize the amount of soil exposed and minimize soil compaction by construction equipment in areas that will not contain permanent structures or where compaction is not necessary for structural integrity; provide natural buffers around surface waters; minimize stream crossings, minimize disturbance of steep slopes and use erosion controls on slopes; preserve topsoil and natural vegetation; establish temporary or permanent vegetation, such as grass or sod, or use non-vegetative controls such as mulch, compost, geotextiles, rolled erosion control products, polymers or soil tackifiers to stabilize exposed soils; divert stormwater that runs onto the site away from disturbed areas of the site.
Sediment BMPs are to capture particles that have mobilized and are entrained in stormwater, with the objective of removing sediment and other pollutants from the stormwater discharge and include silt fences, sediment traps and basins and inlet protectors. Performance of trapping devices can be enhanced by using baffles and skimmers and active treatment processes such as electro-coagulation, filtration, and chemically enhanced settling. Perimeter controls -- diversion dikes, storm rain inlet protection, filter berms, and silt fencing --- are required for down-slopes and side-slope perimeters. Discharges from silt fences must be controlled with vegetated filter strips or vegetated buffers at least six feet in width. Sites must maintain stabilized construction entrances and exits, including wheel wash stations to remove sediment from construction vehicles leaving the site. Sediment and other pollutants, including construction materials, must be removed daily from paved surfaces with washing directed to a sediment basin or control device. Sediments and pollutants discharged to storm drain inlets and sediment from dewatering must be minimized.
Sediment Basin Specifications: Construction projects disturbing 10 or more acres at one time are required to install a sediment basin meeting minimum standards of design, including capacity to contain 2-year, 24-hour storm for the entire watershed area draining to the basin until final stabilization of the disturbed area. Alternatively, a sediment basin with storage volume of 3,600 cubic feet per acre of total watershed area draining to the basin must be provided. If water will be flowing onto the construction site from up-slope and into the basin, the calculation of sediment basin volume must also account for this volume of off-site water. In addition to the water storage volume, a sediment storage volume of at least an additional 1,000 cubic feet per acre of disturbed area plus any sediment from up-slope of the construction site must be added. The effective length of the basin must be at least four times the width of the basin. Alternatives to these specifications with equivalent sediment control may be authorized by the permitting authority.
Pollution prevention practices prohibit discharge of construction wastes, trash, and sanitary waste; wastewater from washout of concrete, stucco, paint, and cleanout of other construction materials; discharge of fuels, oils, or other pollutants used in vehicle and equipment operation and maintenance; discharge of pollutants resulting from the washing of equipment and vehicles where soaps or solvents are used; or from water washing unless washwater treated in sediment basin or better treatment. Exposure of stormwater to building materials, landscape materials, fertilizers, pesticides, herbicides, detergents, and other liquid or dry products must be minimized and the site must implement appropriate chemical spill prevention and response procedures. The site must also prevent stormwater runoff from contacting areas with uncured concrete to minimize changes in stormwater pH.
Turbidity Effluent Limitation: In addition, if sites 30 acres or larger are located in areas of the country with high rainfall intensity and soils with a high clay content, stormwater discharges would be required to meet a numeric limit for turbidity intended to remove fine-grained and slowly-settling or non-settleable particles which typically cannot be effectively removed by conventional stormwater BMPs, such as sediment basins. Turbidity effluent limits require an additional layer of management practices and/or treatment above what most state and local programs are currently requiring4. Many sites would need to use active treatment systems, such as electro-coagulation, polymer clarification, and chitosan-enhanced filtration treatment technologies.
The proposed turbidity effluent limit is 13 NTU (nephelometricturbidity units) as a nonconventional pollutant and an indicator pollutant for the control of other pollutants, such as metals and nutrients associated with sediment and materials on construction sites that can become entrained in stormwater discharges. Hand-held turbidity meters (turbidimeters) can be used to measure turbidity in discharges, or data loggers coupled with in-line turbidity meters can be used to automatically measure and log turbidity measurement reducing labor requirements associated with sampling and provide real-time assessment. Permitting authorities would be required to incorporate these turbidity limitations into their permits for stormwater discharges from C&D sites.
This article was authored by Barbara D. Little, Jackson Kelly PLLC. For more information on the author see here.
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[1] EPA has proposed the same standards for the effluent limitations and the NSPS. EPA interprets the definition of "new source" at CWA § 306(a)(2) as not including discharges associated with construction activity because a construction site cannot itself be constructed. However since the NRDC v.EPA, 437 F.Supp.2d 1137, 1139 (C.D. Cal. 2006), requires EPA to promulgate NSPS, EPA proposes to define “new source” for purposes of Part 450 as any source of stormwater discharge associated with construction activity resulting in an industrial source from which there will be a discharge of pollutants regulated by another NSPS in Subchapter N, e.g., construction activity that builds a new cement manufacturing plant covered by 40 CFR 411.10 would be subject to NSPS under 40 CFR 450.24.
[3] 10 % > by mass of soils < 2 microns in diameter (down to the graded and excavated level of the site).
[4] Oregon requires sites to meet a 160 NTU benchmark if the site is discharging to a waterbody not meeting applicable water quality standards under section 303(d) or a waterbody with a TMDL for sediment and turbidity.
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