Proper development can help reduce pollutant discharge from construction sites.
A Stormwater Pollution Prevention Plan (SWPPP) is required by all National Pollutant Discharge Elimination System (NPDES) Construction General Permits (CGPs) as a means to minimize the ecological and economic impacts associated with sediment and other pollutants entering our nation’s waterways. But before you can prepare a SWPPP, you have to know what one is, how it works, and how it should be implemented.
A SWPPP is a plan developed before a construction activity that is covered by a CGP. When implemented, it helps reduce or eliminate pollutants discharged during the construction project. What most people do not understand is that a SWPPP is not totally written and complete until the Notice of Termination is filed, the site is stabilized with perennial vegetation and the permit coverage for the site is terminated
Stage 1: Initial preparation—When a project requires an NPDES-CGP, a SWPPP must be developed. The U.S. Environmental Protection Agency (EPA) has no requirements about who can prepare a SWPPP, but many states require a professional engineer or other such professional. At a minimum, a professional engineer should be involved in the design of all stormwater control structures such as ponds, diversions, or other stormwater conveyance devices.
The plan is put together using information within the CGP, location of the construction project, description of the construction activity, site description before construction and how it will change after construction, site plans, necessary forms, and any other elements required for creation of a compliant SWPPP. A complete SWPPP includes text, all necessary forms, a copy of the CGP and other related documents, site plans, and details for each control measure discussed in the SWPPP.
Stage 2: Contractor review and modifications—The SWPPP should be part of the bid documents because contractors need to understand all elements of the SWPPP, including frequency of inspections and maintenance of BMPs, to provide an accurate bid. Another important element to review is the limit of disturbance, which should be shown as a bold line around the disturbed area of construction on the site plan. The contractor must verify that the limits are reasonable to construct the project, realizing that neither equipment nor construction materials can go beyond these limits at any time during construction without amending the plan and permit first. It is much easier to amend the plan and permit before construction begins than to stop during construction to submit amendments and obtain permit coverage.
Stage 3: Pre-construction perimeter controls installation—Once the SWPPP is delivered to the site, the first activity is to install the perimeter controls before any clearing and grading activity begins. While some disturbance and clearing may be needed to install the controls, it is permissible as long as you disturb only the minimum area required. Any low areas that may discharge stormwater during initial clearing and grubbing of the site must have controls in place before the clearing activity begins. Other controls to be used during construction are installed before the soil disturbing work.
Stage 4: Modifications and updates during construction—Immediately after Stage 3 and the installation of any controls, the clock starts ticking for inspections. How often inspections are performed is determined by the CGP and is discussed in the SWPPP. Additional SWPPP modifications and updates will include providing in the SWPPP a written Delegation of Authority letter providing the person who is performing the inspections the right to sign each one if they are not the same signature person on the Notice of Intent.
Other updates include marking up the site plan with dates and locations of grading and other soil disturbance activities, as well as a site soil disturbance activity log to record when each activity starts and ends. Inspections of the SWPPP and site, as well as documenting deficiencies and when they were corrected, are recorded on inspection forms and kept in the SWPPP.
Stage 5: Filing the Notice of Termination and storing the SWPPP—When all construction activities are complete and all disturbed soil is stabilized per the requirements of the CGP, the Notice of Termination may be submitted to the appropriate agency. At this time, the SWPPP, including all inspection and other forms, site plans, detail sheets, public posting papers, consultation letters, updates, activity logs, and anything else created as a requirement of the CGP, are gathered together and stored at the permitted company’s office for three years, beginning when the Notice of Termination is filed. The SWPPP is now complete.
A SWPPP is a complex document that needs constant updates and modifications to control pollutants discharging from construction sites. Below are four actions that could help the construction industry achieve more successful SWPPPs and compliance with the CGP:
- The SWPPP preparer needs to make sure the SWPPP is totally in compliance with all CGP requirements noted in the SWPPP before construction starts.
- The SWPPP preparer should be involved throughout the construction activity to help redesign or develop changes that may be necessary if controls are ineffective or sediment or other pollutants are leaving the construction site.
- The contractor needs to understand the elements within the SWPPP and properly install, implement, and inspect all aspects of the SWPPP during construction.
- Contractors and sub-contractors should receive onsite training about the requirements of the CGP and SWPPP and who they should inform if they see an issue of non-compliance at the construction site.
Training programs are available that provide certification for inspectors and SWPPP preparers, as well as courses for subcontractors. One such provider, Stormwater USA, additionally maintains a library of the CGPs for each state and the EPA, along with all necessary forms and guidance documents such as BMP manuals and specifications to aid preparers’ design and selection of controls.
With more education for all those involved in making construction sites control stormwater discharges, we will achieve cleaner, healthier waters and reduce the costs of dredging waterways. We can provide clean, safe drinking water and increase healthy fish and aquatic life habitat, so we all can enjoy the nation’s waterways. Stormwater compliance is a win for everyone.
Shirley D. Morrow, CPESC, CISEC, is vice president and director of technical content for Stormwater USA. She has written hundreds of SWPPPs during her 16-year career in the erosion and sediment control industry. She can be reached via e-mail at firstname.lastname@example.org.
Extreme situations may call for hydroseeding measures,
By Tom Wedegaertner
Ragsdale says hydraulically applied erosion control blankets can be a cost-effective tool for such extreme conditions.
Weighted sediment tubes used as temporary check dams
By Kevin B. Wolfe, Ph.D., P.E., DWRE
A new weighted sediment-control and stormwater diversion device has been developed by Friendly Environment of Shelbyville, Tenn. The new sediment-tube product, the Erosion Eel, can be used to replace traditional silt fence, rock check dams, wattles, and temporary diversion berms. The product is a 3-D tubular, sediment-retention device with internal filter media comprised of recycled, shredded, rubber tires encased by a woven geotextile fabric. The rubber is washed and the metal reinforcing belts are removed during the shredding process. The primary sources of tires used for this product are landfills, where the tires have been "mined" and removed from the buried debris for beneficial reuse as a stormwater treatment device. Like silt fence, the tubes can be applied to intercept sheet-flow runoff perpendicular to the direction of flow along sloped surfaces. But unlike silt fence, the product can also be placed within concentrated flow paths to act as a check dam.
Various sized Erosion Eels were used on this site at Norris Creek: 9.5-inch-diameter tubes were used as perimeter controls to intercept inter-rill (sheet) flow from the construction site; 0.5-inch-diameter tubes were stacked and used as check dams in roadside ditches; 20-inch-diameter Eels, 10 feet long, were placed within ditches conveying heavier flows.
The product is relatively easy and quick to install. No trenching is required to seat the tubes in place, and staking is only required when the tubes are placed to intercept concentrated flows and when placed on steep side slopes. The 9.5-inch tubes weigh 140 pounds per 10-foot tube and are equipped with four handles for ease of mobility. The outer fabric is a tough woven monofilament geotextile; therefore, the Eels can be dragged along the ground with no damage to the tubes. The tubes are also designed to be reused from project to project.
The Erosion Eel has been the subject of a series of long-term field performance studies and laboratory flume performance trials performed by Civil & Environmental Consultants, Inc. (CEC), of Nashville, Tenn. The primary attenuating mechanisms for the tubes involve two processes: sedimentation and filtration. Mass balance flume testing of the Eels have revealed that approximately 80 percent to 90 percent of the total solids removal attributed to the tubes is via sedimentation, with the remainder of the solids removal via filtration within the rubber porous media within the tube.
As part of the testing to demonstrate the effectiveness of this new best management practice (BMP), comparative flume performance tests have been carried out by CEC, examining the performance of both standard rock checks and the Erosion Eel. The flume tests were conducted by CEC for water quality and hydraulic performance in 2007 and 2008. Silty clay soil was used as the suspended material in order to determine suspended solids removal effectiveness for each BMP. The test set-up for the rock check dam incorporated a single rock check built per Tennessee Department of Transportation (TDOT) specifications. For a comparative assessment of the tube’s capabilities, a single 100-percent rubber Eel was used in separate flume tests under the same protocol. Single pass-through runs of 50 liters per run were used along with an inflow suspended slurry concentration of 3,000 mg/L. In summary, the average soil retention efficiency (in percent) for the rock check dam was 53.9 percent based on total suspended solids, while the Eel removed an average of 85.6 percent of the soil. Relative to hydraulics, there was no significant difference in flow-through velocities for the two measures.
The product has also been used on numerous construction sites as a primary construction BMP. One example is the TDOT’s Norris Creek Bridge project in Fayetteville, Tenn. The TDOT project site was under construction in 2007-2008 and involved the construction of a bridge with the associated approach sections. A combination of Erosion Eels was used on this site. The 9.5-inch-diameter tubes were used as perimeter controls to intercept inter-rill (sheet) flow from the construction site. In addition, the 0.5-inch-diameter Eels were stacked and used as check dams in roadside ditches. Larger size Eels, consisting of tubes 20 inches in diameter and 10 feet in length, were placed within ditches conveying heavier flows to function as check dams. The tubes’ performance on this project was highly effective, and the used tubes have been relocated to other sites.
Kevin B. Wolfe, Ph.D., P.E., DWRE, is a principal engineer with Civil & Environmental Consultants, Inc. He can be reached via e-mail at email@example.com.