Image
The new EPA effluent limitation guidelines have transformed not only the way in which sediment control plans are designed, but also the way construction sites are managed altogether. Photo: iStock.com
Image

Owners are now expected to be able to prove that their plans for limiting stormwater turbidity work. Though expected to reduce the amount of sediment flowing from the nation's construction sites by 4 billion pounds each year, this requirement will cost owners and contractors about $953 million.

Since 1991, construction sites have been considered industrial activity with pollutant discharges that are regulated under the Clean Water Act's NPDES stormwater permit program. Previously, permittees relied on local programs and best management practices to control sediment, nutrients, and turbidity.

EPA's recent effluent limitations guidelines (ELG) and new source performance standards (NSPS), however, require permittees to report the effectiveness of total site pollution controls. The requirements don't dictate specific technologies but instead limit the maximum daily turbidity level in discharges from sites 10 acres and larger to 280 nephelometric turbidity units (NTU).

Although EPA issued a temporary stay of the sampling and a 280-NTU numeric limit Jan. 4 while it revisits analysis of the data that led to the 280 NTU standard, the agency intends to make the revised limitation effective by June 29.

Compliance will require additional effluent sampling. For some projects, particularly those in areas with fine-grained silt and clay soils, compliance may require rethinking the overall approach to erosion and sediment control.

Owners who exceed the limit will be required to provide a detailed assessment of site conditions as well as a plan for immediate remediation. If noncompliance continues, state or local sediment control inspectors (such as the local permitting authority) will impose penalties. Fines for violation of the Clean Water Act and related environmental regulations vary by state; in Maryland penalties range from $2,500 to $25,000 per day of violation; Utah reports penalties of $32,500/day.

During the summer of 2008, our firm developed the erosion and sediment control plan for the Maryland Transportation Authority's I-95 express toll lane project, which began in 2006 and is slated to run through 2014. The agency contacted us when summer thunderstorms resulted in public outcry over sediment runoff upstream. The community assumed the project was the source, but we demonstrated that our sediment controls were functioning and were not the source of the discharge — proof that managing sediment onsite and inspecting and maintaining pollution controls is time well spent.

Using our experience with community watershed groups and large-scale public works construction projects, we've developed strategies that can help you prepare for increased community and federal attention to sediment pollution, including how to:

  • Evaluate how the project can be built within the existing landform with minimal clearing and grading. Vegetation that doesn't need to be cleared to accommodate the new construction, particularly at the project perimeter, provides an important vegetative filter to prevent offsite discharges of sediment-laden water.
  • Stabilize bare soil areas daily and convert them to permanent vegetative cover.
  • Specify best management practices, such as chitosan- and polymer-enhanced filtration, that are most effective at removing fine-grained materials.
  • Increase the capacity of onsite controls by using more than one.
  • Stay abreast of weather forecasts and manage the volume in sediment basins to maintain a minimum capacity for incoming sediment and storm-water. You can do this by fitting the outfall with a floating outlet and filter bag that takes water from the surface rather than from the bottom of the basin and/or passing discharges through a series of basins, which improves water clarity progressively. (You may have to use flocculating agents to settle the finest particles.)
  • You have the flexibility to select management practices and technologies best suited to site-specific conditions. Focus first on combining both best management technologies and site management practices to prevent fine-grained sediment from entering stormwater, then implement measures that remove it once it is entrained in stormwater.

    The standard set by the ELG is 280 nephelometric turbidity units (NTU), a level that is very difficult to achieve in silty and clay-like soil areas. With the new effluent limitation guideline, contractors and owners face being cited for violation of the Clean Water Act, a far more costly consequence.

    — Eileen Straughan (estraughan@straughanenvironmental.com) is founder of Straughan Environmental, a consulting firm that provides environmental planning, permitting, and mitigation design services throughout the mid-Atlantic region.