SWUTC Research Project Description
Preparing for EPA Effluent Limitation Guidelines
University: Texas A&M University
Principal Investigator:
Jett McFalls
Texas Transportation Institute
(979) 847-8709
Funding Source: SPR Program
Total Project Cost: $113,869
Project Number: 0-6638
Date Started: 9/1/12
Estimated Completion Date: 8/31/13
Project Summary
Project Abstract:
On December 1, 2009, the US Environmental Protection Agency (EPA) finalized and published a rule in the Federal Register establishing non-numeric and, for the first time, numeric effluent limitation guidelines (ELGs). The numeric ELGs include turbidity limits and sampling requirements for stormwater discharges from construction sites. All sites that disturb 20 or more acres of land at one time are required to comply with a turbidity limit of 280 NTUs. The EPA is requiring Texas to implement these new requirements when the Texas Commission on Environmental Quality (TCEQ) renews the Texas Construction General Permit (CGP) in 2013. On February 2, 2014 the new limits will apply to all construction sites disturbing 10 or more acres of land at one time.
In this project, monitoring and testing experiments will be conducted to 1) determine “typical turbidity” representative of TxDOT’s construction site discharges, 2) collect performance data on innovative erosion and sediment control measures that might be expected to achieve the discharge standard, and 3) produce Guidance Measures and Sampling Protocols for TxDOT to negotiate with TCEQ in the development of statewide monitoring/sampling procedures. Three research institutes (Texas Transportation Institute, The University of Texas at Austin and Texas Tech University) will collaborate on this project to cover the statewide differences in climate, soil types, slopes, and other factors that affect the performance of erosion control measures.
Project Objectives:
The results of this study will provide TxDOT with guidance and recommendations on identifying representative outfalls on TxDOT projects and how should those outfalls be monitored. This guidance will identify cost effective erosion and sediment control strategies which can be used to meet the 280 NTU limit.
Task Descriptions:
Task 1: Literature Review and Current DOT Practices
Task 2: Controlled Testing of Coagulants
Task 3: Construction Site Field Monitoring
Task 4: Development of Monitoring/Sampling Protocols
Task 5: Statewide Field Testing to Determine Effectiveness of Recommended Practices and Sampling Protocols
Task 6: Revision and Submittal of Monitoring/Sampling Protocols
Task 7a: Provide Material for Revision of TxDOT Stormwater Management Guidelines for Construction Activities
Task 7b: Develop and Conduct Training Workshop
Task 8: Preparation of Reports
Implementation of Research Outcomes:
The polyacrylamide (PAM) application evaluated in the study was not effective in significantly reducing turbidity or soil loss on clay soils with 1:3 slopes. Due to the high range of turbidity (3,450 to 9,037 NTUs), the efficiency of PAM could not be determined. To compare the sediment removal efficiency of treated and untreated sediment retention devices, wood fiber wattles were installed in sediment retention device (SRD) test flumes. Testing showed that PAM-treated SRDs were 8 to 18 percent more successful at reducing sediment from sediment-laden water than untreated SRDs.
Researchers performed flocculation tests to understand soil and polymer characteristics, as well as to determine what doses of coagulants are necessary to promote flocculation. Colloidal clay suspensions were mixed, or clumped together using coagulants, such as PAM, chitosan, alum, or gypsum, to promote the clustering of these stabilized particles. The suspensions then settled, reducing the amount of contamination in the runoff. Testing showed that the higher the molecular weight of the application, the more likely it was to reduce turbidity. Conversely, when the influence of charge density on flocculation was tested, researchers found that as charge density increased, PAM effectiveness decreased. As a result, non-ionic PAMs are expected to be the most effective at promoting flocculation.
Impacts/Benefits of Implementation:
When this project terminated, EPA was reevaluating its ruling regarding effluent limitation guidelines (ELGs). Having this research in place means that when the Texas Commission on Environmental Quality (TCEQ) renews its Texas Construction General Permit—which requires compliance with EPA regulations—TCEQ will be better able to make informed decisions regarding the monitoring, sampling, and site management requirements levied by EPA regarding stormwater runoff from construction sites.
Web Links:
Final Technical Report