Streams and Wetlands: Construction Best Practices

Staging areas are short- or long-term sites within a construction or development area where equipment and materials are stored. These areas are accessed frequently; and when fuel and oil are stored here, the potential for runoff and erosion in these areas may be high.

• Erosion and sediment controls should be installed and maintained to prevent discharge from the site.
• Staging areas for crew, equipment, and materials should be established well away from streams and rivers or highly erodible soils.
• Stationary fuel and oil storage containers should remain within a staging area or another confined area to avoid accidental spills into the stream systems.
• Excess concrete and wash water from trucks and other concrete mixing equipment should be disposed of where this material cannot enter the stream systems.
• If temporary roadways must be built, ensure that roadways are of low gradient with sufficient roadbed and storm water runoff drains and outlets. Containment basins, silt fences, filter strips, etc. should be included for retention of storm water runoff for reducing sediment introduction into natural waterways.
• Avoid stream crossings. If unavoidable, temporary crossings should be used. Temporary crossings should not restrict or interrupt natural stream flow. If temporary in-channel fill is necessary, culverts of sufficient size should be employed to avoid water impoundment and allow for fish passage.

The riparian corridor is the vegetation adjacent to a stream or river. This area is critical to the health and quality of the aquatic environment because of its ability to slow and reduce sediment and chemical runoff into the stream or river channel. Maintain a riparian corridor with a minimum width of 100 feet from the edge of the stream or river along both sides of streams and rivers.

• Limit clearing of vegetation, including both standing and downed timber, to that which is absolutely necessary for construction purposes.
• Heavy equipment use within the riparian corridor should be restricted to minimize vegetation destruction and compaction of soils. Flagging or fencing areas that are not to be disturbed is helpful in alerting construction personnel.
• General application of pesticides, herbicides, or fertilizers within the riparian corridor should be prohibited to avoid water contamination due to over- spray or runoff. Fertilizer use or spot application of pesticides and herbicides is acceptable if appropriate non-restricted chemicals are used.
• Riparian areas located down slope of construction zones should be physically screened with sediment controls, such as silt fences or filter strips. Sediment controls should be monitored after rain and maintained for the duration of the project.
• All riparian corridors disturbed by the project should be revegetated immediately following or concurrent with project implementation. Appropriate native bottomland or riparian trees, shrubs, and grasses should be planted to ensure long-term stability in areas where the soil erosion threat is not critical. Annual nonnative grasses such as rye or wheat may be planted in conjunction with native species to provide short-term erosion control. Areas judged to be subject to immediate soil loss due to steep slopes or other factors causing critical erosion conditions may be planted with nonnative mixtures to assure rapid establishment and erosion control.
• Post-construction evaluation of vegetation establishment should be conducted at one month intervals for at least three months after completion of the project. Any recommended sediment controls should be inspected at these times. If determined beneficial to soil stability and not adversely impacting site function and/or aesthetics, recommended sediment controls should remain permanent.
• All temporary erosion and sediment controls should be removed (unless removal would cause further disturbance) and properly disposed of within 30 days after final site stabilization is achieved or after temporary practices are no longer needed.

The structure of a bank is an important feature of a stream or river. It defines and provides stability for the channel.

• Bank stability will vary depending on height, slope, and soil conditions. Project engineers and hydrologists should thoroughly investigate the physical properties and hydrologic record of the proposed site before construction begins.
• Limit clearing of vegetation, including both standing and downed timber, to that which is absolutely necessary for construction purposes.
• Projects in which bank alteration is necessary should employ, to the highest degree possible, erosion prevention measures before actual excavation activities begin. These preventative measures should be monitored regularly and maintained for the duration of the project.
• Use of riprap for stream bank stabilization should be limited to those areas that could experience substantial erosion before adequate vegetation becomes established. The material for the rock blanket should consist of durable stone or broken concrete that is well graded. It is preferable that 40–60 percent of the material be as large as the thickness of the blanket, with enough smaller pieces of various sizes to fill the larger voids. It should not contain more than 10 percent of earth, sand, shale, and non-durable rock. Bank stabilization materials should allow for continuous passage of fish and other aquatic species.
• No permanent fill materials, other than design- approved structures and related bank stabilization materials, should be placed in the stream channel. Avoid channelization. Excavated materials should not be stored or stockpiled below the high bank.
• Work should be conducted during low flow periods when possible.
• Care should be taken to keep machinery out of the waterway as much as possible.
• Do not alter or remove natural stream features, such as riffles and pools.
• Large woody debris is an important habitat component of a stream and should not be removed unless absolutely necessary for construction and maintenance purposes.