The Texas A&M Transportation Institute (TTI) has more than three decades of evaluating the performance of erosion control products. These products include rolled erosion control products (RECPs) and hydraulically applied products (HECPs). The results provide the data for the Texas Department of Transportation (TxDOT) Approved Product List for erosion control products. While this program has ensured the use of the most appropriate erosion control products, sediment control devices (SCDs) have not been included in the process. However, beginning in fall 2023, an approval process for SCDs will be initiated for TxDOT.
Background
The Environmental Protection Agency guidance document “National Management Measure to Control Nonpoint Source Pollution from Urban Areas” requires all construction site activities to reduce the amount of sediment generated and reduce the off-site transport of sediment and construction-related chemicals.1 While there are several pollutants of concern (oils, gasoline, degreasers, paints, etc.), sediment from construction sites is by far the largest pollutant source. Eroded sediment from construction sites causes many problems, including traffic safety issues, adverse impacts on water quality as well as decreased capacity of reservoirs and streams, resulting in possible flooding.
SCDs are used on construction sites to retain sediment and prevent stormwater from adversely affecting adjacent waterways. SCDs include wattles, sediment logs, filter dams and inlet protection devices. These products are designed to be installed for specific applications such as curb inlets, drop inlets, perimeter protection, etc. However, there is not a scientifically sound, repeatable testing methodology that replicates field conditions to test and determine SCD performance.
Researchers at TTI’s Sediment and Erosion Control Laboratory (Figures 1 and 2) are in the process of developing a formal testing protocol/facility, test apparatus and future thresholds for a performance based SCD testing program that will assist the designer/engineer in selecting the most effective sediment control best management practice. The test apparatus and test protocol will include, but is not limited to drop inlets, curb/gutter, dewatering bags, and turbidity barriers.
Implementation
TxDOT construction projects are required by state and federal regulations to implement sediment control measures called best management practices (BMPs) to protect water quality during construction. Currently, however, there are no TxDOT-established minimum performance requirements for sediment control BMPs. No guidance exists to provide quantitative information to TxDOT personnel on the efficacy of these SCDs or information documenting under what conditions they will perform adequately.
To meet federal guidelines and assist the TxDOT’s environmental quality requirements, TTI is working to develop a formal testing protocol for the evaluation of SCDs that can be implemented as an SCD performance evaluation program. An SCD performance evaluation program will allow TxDOT division and district planners and engineers to select the most effective sediment control devices specific to site conditions and project needs. TTI will also produce an Approved Product List for all SCDs used by TxDOT on Texas roadsides. TTI recommends incorporating the SCD APL in the current process for listing approved erosion control products.
Research Plan
TTI has assembled a multi-disciplinary team with extensive experience in erosion and sediment control and storm water management. The group assembled to complete this two-year project is also skilled in planning, developing and managing test protocols and product testing. The work plan of the project is divided into six tasks — with the findings of each task providing input to the next task.
The tasks include:
- Project management: TTI is documenting all research findings from this project, consolidating data, submitting required reports, and attending project progress meetings as scheduled by and in conjunction with TxDOT.
- Document state-of-the-practice: TTI is assessing the state-of-the-practice and identifying key metrics in the performance evaluation of SCDs through a detailed review of the literature and structured interviews with TxDOT well as other DOTs and other stakeholders.
- Assess existing SCD testing protocol: In conjunction with task 2, TTI is evaluating existing SCD test methodology. Components that meet the testing goals of TXDOT and are effective for gathering data and developing an effective test method will be used to enhance the development of the TTI/TxDOT test apparatus and testing protocol.
- Enhance TxDOT/TTI SCD testing system: TTI has performed previous work with sediment control devices installed in high flow channels and is now placing specific focus on expanding and formalizing its SCD testing system to evaluate additional SCDs used in different applications, including, but not limited to drop inlets, curb/gutter, dewatering bags and turbidity barriers to the proposed test protocol.
- Develop test protocol, calibrate SCD testing system, test SCDs: TTI is developing an SCD data testing and collection plan. Once this plan is finalized, the system will be calibrated, and product testing will begin. TxDOT approval of the test protocol and test methods, including evaluating calibration and preliminary data results will be conducted prior to the start of any formal SCD testing.
- Incorporate SCD testing results in an Approved Product List for erosion control products: TTI is revising and updating TxDOT’s process for listing approved erosion control products to include approved SCDs.
Formal proprietary testing and approved products listing of SCD products that meet minimum performance thresholds will begin once this project is complete in August 2023.
Reference
- National Management Measures to Control Nonpoint Source Pollution from Urban Areas, November 2005, EPA-841-B-05-004.
For more information, contact:
- Jett McFalls, project supervisor, Texas A&M Transportation Institute, Environment & Planning. j-mcfalls@tti.tamu.edu or 1.979.317.2801.
- Derrold Foster, SEC lab manager, Texas A&M Transportation Institute, Environment & Planning. d-foster@tti.tamu.edu or 1.979.317.2242
