Member Article

Many construction site operators take for granted permits for stormwater discharge. Operators file Notices of Intent for general permits, needing only to provide plans for sedimentation and erosion control at the construction site.

Total Maximum Daily Load (TMDL) is a calculation of the maximum amount of a pollutant loading that a water body can receive in a day and still safely meet water quality standards. A stream may be impaired if numerical concentrations are exceeded or if narrative standards are not attained. For example, the biological integrity of the stream segment may be impaired because of nutrients in the water column, causing persistent turbidity, algae blooms or drops in dissolved oxygen.

A TMDL allocates contributions of the offending pollutants among point source dischargers and nonpoint source contributors. Point sources would include any contribution of nutrients to the stream segment which are delivered through a discrete conveyance such as a pipe or ditch. A nonpoint source contributor of nutrients could be an agricultural operation, a golf course or even a forest.

Most construction sites do a reasonable job of controlling sediment leaving the site, but what about controlling nitrogen and phosphorus discharges? Sources of nitrogen and phosphorus can include chemicals applied to landscaped features on a construction site, or even droppings from birds and other wildlife which have been attracted to the grassed swales utilized as part of the sedimentation and erosion control plan for a site.

What about pollutants other than nutrients? Mercury in the water column and stream bed is absorbed by fish and creatures that inhabit the stream bottoms which are a food source for these fish. The fish can accumulate unsafe levels of mercury in their bodies making them unfit for consumption by humans.

The source of the mercury may be, in part, industrial and municipal wastewater treatment facility point source dischargers. However, mercury also gets into the air as particulate matter and finds its way onto construction sites or other land via atmospheric deposition. From there, it is conveyed to streams and lakes by stormwater, which is collected and channeled to the streams by municipalities and construction sites.

Here’s the rub for operators of construction sites. If levels of mercury are found in fish in the stream segment or lake to which the site drains, then the stream or lake may be considered impaired because it fails to meet the narrative water quality standard for biological integrity or secondary recreation. If the water body is impaired, a TMDL may be the next step. The TMDL will assign an allocation of mercury to all point source and nonpoint source contributions. One of those will be the stormwater discharges from construction sites.

Contractors and landowners need to be aware of the condition of the water bodies to which their sites drain. If impaired, there will be consequences including effluent limits or management measures incorporated into the stormwater permit that operators will have to undertake – potentially at significant cost and with the risk of enforcement.

Craig A. Bromby is a partner in the Raleigh, N.C., office of Hunton & Williams LLP and a leader within the firm’s environmental law group. His practice focuses on administrative law and environmental compliance, particularly matters involving water quality, wetlands, stormwater, industrial wastewater and development-related regulations.