On November 23, 2009, the U.S. Environmental Protection Agency (EPA) finalized new rules intended to control stormwater pollution from construction sites.  The rule takes effect on February 2010 and will be phased in over four years. 

The most significant new requirement is the imposition of numeric discharge limits from larger construction sites.  In the past, U.S. EPA required construction site owners/operators to implement best management practices (BMPs) to control stormwater runoff without monitoring or discharge limits.  Once the new standards are phased in, owners/operators will be required to sample stormwater discharges and comply with a numeric standard for the pollutant turbidity in discharges according to the following schedule:

• In 18 months (August 2011), construction sites 20 acres or larger will be required to monitor and meet numeric discharge limits
• In four years, construction sites 10 acres or larger will be required to monitor and meet numeric discharge limits

From the EPA press release:

Owners and operators of sites that impact 10 or more acres of land at one time will be required to monitor discharges and ensure they comply with specific limits on discharges to minimize the impact on nearby water bodies. This is the first time that EPA has imposed national monitoring requirements and enforceable numeric limitations on construction site stormwater discharges.

There are also impacts to smaller construction sites ranging from 1 acre to 10 acres in size.  The rule will impose a series of mandatory Best Management Practices (BMPs) relating to: Erosion and Sediment Controls; Soil Stabilization BMPs; Dewatering BMPs; Pollution Prevention Measures; and Prohibited Discharges.  Previously, owners/operators were allowed to pick and choose their BMPs as long as they met specified engineering requirements.

Stringency of the Numeric Limits

Dirt particles in storm water discharges typically cannot be effectively removed by conventional BMPs (such as sediment basins). In November 2008, U.S. EPA had proposed a numeric limit of 13 nephelometric turbidity units (NTU). To meet the proposed numeric turbidity limit, sites may have been forced to actively treat stormwater.  Active treatment could have included use of chemical treatment and filtration of their storm water discharges.

However, U.S. EPA backed off the stringent 13 NTU proposed limit.  The final rule has a far more relaxed standard of 280 NTU.  EPA decided to increase the limits based upon a flood of comments suggesting the 13 NTU limit would represent less than background levels at some sites and would be nearly impossible to meet.

Even with the high numeric standard, Industry is concerned with the implications of the new rules.  The construction industry is simply not accustomed to being required to take samples and meet specific permit limits.  As detailed on the Associated General Contractors of America, the following could be implications for contractors at larger construction sites:

On all jobsites where the numeric limit applies, the rule requires contractors to collect numerous stormwater runoff samples from all discharge points during every rain event and calculate the NTU level(s). (This may entail taking "grab" samples by hand and performing measurements with a field turbidimeter; however the rule doesn’t specify any sort of monitoring protocol or methods – instead EPA is leaving it up to that states to spell that out in their permits.) If the average NTU level of the samples taken over the course of a day exceeds the "daily maximum limit" of 280 NTU on any given calendar day, then the site is in violation of the federal limitation requirement. EPA is also leaving it up to the states to specify applicable requirements for contractors to report on the samples they take of their construction site discharges…

AGC is deeply concerned about the potential impact this rule will have on the construction industry and will provide more information in the near term as we continue to analyze EPA’s C&D ELG rulemaking

No doubt the final rule represents a significant increase in the stringency of regulations applicable to the construction industry.