Combinations of sediment and erosion control were often needed during peak construction activity. Slope stabilization was not always possible during these times. Temporary measures included stabilization and sandbag check dams or silt fence, especially needed during the rainy season.

City Challenges

There ensued a dispute between the grading contractor and developer over responsibility for the city requirement to install 1,700 linear feet of silt fence along the site perimeter adjacent to a dry arroyo. It became a brutal, expensive lesson. During a site meeting with the parties the city engineer declared all work suspended pending installation of the silt fencing to his satisfaction.

ABOVE & BELOW: As graded slopes were finished, several methods of stabilization were used. Erosion blankets and hydroseeding with a quick cover of annual rye grass and native seed blends for longer termed protection were used.

The grading contractor directed us to install the silt fencing. The city engineer said additional areas requiring silt fencing and that he would not release the site to start work until these areas also were complete. One week and over 35,000 lf of silt fence later, the city engineer gave the OK for grading to continue. Some of the silt fence was usefully, but the majority served no purpose and was removed within days and weeks after the grader started operations again.

We developed the SWPPP manuals and an erosion control plan and a laminated (for ease of updating) site overview BMP plan. After training by our company, the annual certification of the SWPPP and routine inspections are performed by the developer. The developer also has a NPDES compliance person. The BMP plan, routinely updated, and the SWPPP manual are prominently displayed in the main construction trailer on the project. SWPPP records should be kept for three years after completion of a project.

Logs

Keeping inspection and maintenance logs current and performing regular inspections and maintenance demonstrate an active SWPPP compliance effort. A pre-storm inspection is done whenever the National Weather Service declares a 40 percent chance or better for rain. Interim inspections are needed for every 24-hour period that rain continues and an inspection within 24 hours after the rain stops.

(ABOVE) Lots were then sprayed with a quick cover hydroseed. After several months of rains, the lots were covered with native grasses (BELOW) that stabilized the soil and helped filter the water prior to leaving the lot pad. Once this system was in place and functioning the rainwater coming off the lots was nearly clear and as clean as a mountain stream. A bonded fiber matrix (BFM) was often sprayed as a short term (up to six months) stabilization method.

Storm Water Pollution Prevention Plan (SWPPP)

All construction projects over one acre required a SWPPP, per the Clean Water Act. The vehicle created out of this law is the National Pollution Distribution Elimination System (NPDES). NPDES requires municipalities with a storm water system to prepare a SWPPP.

BMPs

The most prominent element of SWPPP is best management practices (BMPs). These are the methods employed to prevent common construction pollutants, including soil, from leaving the site. BMPs employed include: proper handling of concrete products and waste via a wash-out containment area; contained mixing areas and liquid storage areas (on pallets) with secondary containment (e.g., a pit lined with poly sheeting with a perimeter berm; stockpile containment (e.g., fill soil covered with poly sheeting); erosion blankets and planting for slope stabilization; sandbag lines along curbs to prevent other excavation spoils from entering storm water drains; gravelbags for lot perimeters and street run-off controls; lot silt fences and blankets; hydromulch (straw blanket held in place with a hydrospray of wood mulch and organic binder); tackifiers (soil stabilizers); contained areas for heavy equipment parking, with booms placed across outlet points to absorb any oil; stabilized construction entrances; sandbag chevrons in newly graded roads and at toes of slopes; sandbag check dams or silt fences for temporary slope stabilization, especially during the rainy season.

Silt fencing was installed and maintained during all construction to keep pollutants from running off the lot. Disputes over responsibility for silt fencing in an arroyo proved to be a costly lesson.

A Rewarding Project

This has been a challenging and rewarding project. A key factor is the willingness of the developer to understand the law and commitment to doing the right thing. Quality companies recognize the long-term effects and impacts of development. It is essential to approach development with viable, real world programs and costs. Too many fly-by-night operators exist.

With the increased impact of erosion control and SWPPP compliance on construction sites, many new players have arrived on the scene. Often they do not understand the concepts of soil loss and hydrology. This results too many times in failed efforts and extreme costs to the builders, developers and environment. It is so very important to research and find seasoned and knowledgeable professionals to help design, implement, monitor and maintain NPDES compliant programs on all construction sites. Bringing these professionals in during preliminary planning and engineering will result in huge cost savings over the life of a large project. It will also bring the owners, engineers and project managers on these large investments a sense of security and peace of mind.

A lot of soil will migrate off the lots during heavy rainfall. We developed a run-off control and stabilization program. Each flat lot received a graded swale along one side and across the front of the lot. This swale was graded with gradual fall to the front of the lot. A gravel bag check dam, outlet pipe, and poly sheet scour protection were then installed.

I know for a fact that doing it right the first time does save money and headaches. The resulting satisfaction from doing the right thing for your client, Mother Nature and future generations is also a great feeling.

In longer-term landscape areas, erosion blanket and planting (or bark and tackifier) were used for slope stabilization.

About the author and company:

Eric Woodhouse, CPESC ( ewoodhouse@landscapedevelopment.com) is a certified professional in erosion and sediment control. He is the division president of earth services for Landscape Development, Inc. Landscape Development, Inc. ( landscapedevelopment.com) is located in Southern Calif., with office and yard locations in L.A., Ventura, Inland Empire, San Diego and Bakersfield. The company has provided erosion control and storm water pollution prevention plan (SWPPP) compliance designs and installations since 1991.