It's no secret that the clearing, excavating, and grading involved in construction disrupts the natural functions of landscapes, but what many people may not completely understand is the impact such environmental upset can have on the quality of nearby bodies of water.

Construction activities contribute to increased stormwater runoff and site erosion, allowing sediments to pollute surface waters such as lakes and streams, and they also can unearth more toxic pollutants embedded in a site or introduce new pollutants from construction equipment. All this degrades the quality of the water that humans and animals alike depend on. There are methods for managing construction site soils that minimize damaging runoff and discharges, but while every state and local government establishes requirements for managing stormwater discharges, some are more stringent than others and water quality varies widely around the country.

As a way to improve water quality throughout the United States, the U.S. Environmental Protection Agency recently issued a new national rule that aims to significantly reduce the discharge of pollutants—in the form of sediment, turbidity (suspended particles), nutrients, metals, and organic compounds—from construction sites. The rule, "Effluent Guidelines for Discharges from the Construction and Development Industry," will be phased in over four years beginning in February 2010.

Under the new rule, construction site owners and operators who disturb one or more acres must implement a range of best management practices for controlling soils and sediment and reducing erosion, thereby abating water pollution. They also will be required to use methods that control discharges from activities such as dewatering and concrete washout from the cleaning of concrete mixing containers and equipment. Site owners and operators that disturb 10 or more acres of land at one time must also monitor site discharges through sampling and testing to ensure compliance with a set of new limitations on turbidity in discharge. The EPA says this is the first time it has imposed national monitoring requirements and enforceable limitations on stormwater discharges from construction sites.

According to EPA, the new regulations will reduce sediment discharges from construction sites by about four billion pounds each year, once they have been fully implemented. Such reductions will improve water clarity, help improve aquatic environments and protect drinking water supplies, and reduce the need for dredging in navigation channels and reservoirs, the agency notes.

While the new rule establishes minimum national requirements, it was designed to work with existing state and local stormwater management regulations and won't replace those that exceed it. The way will still be clear for state and local governments for developing new, more stringent regulations, as well.

The EPA's notice on the new effluent guidelines for construction sites have been published in the Federal Register and is available for download here. The document details the agency's process and reasoning in arriving at its final rule, including the potential impact on mortgages for new single-family homes.

Stephani L. Miller is Associate Web Editor for Custom Home and residential architect.