The Texas A&M Transportation Institute’s Sediment and Erosion Control Laboratory (SEC Lab) provides the transportation industry with a research and performance evaluation program for roadside environmental management. The program includes storm water quality improvement, erosion and sediment control, and vegetation establishment and management.
TTI’s Environment and Planning Program operates this 19-acre, full scale, indoor/outdoor facility. Demand for the facility has steadily grown for over 20 years, necessitating the recent expansion to meet the industry’s research needs. With funding from the Texas Department of Transportation (TxDOT), TTI produces and maintains the TxDOT Approved Products List (APL) for all sediment and erosion control products used by TxDOT on Texas roadsides. Three major aspects of the lab are the indoor rain simulators, sediment retention device flume, and variable slope channel flume. In addition to this equipment, the SEC Lab also houses a 2,800-square-foot climate-controlled greenhouse, small footprint stormwater quality structure, index testing laboratory, bench-scale testing capabilities, 65-foot concrete flume, 1,000 linear feet of 25-feet tall soil embankment built with 2:1 and 3:1 slopes per highway specifications, and 10 at-grade channels 85-feet in length.
2013 Lab Expansion
To expedite product and device performance evaluations and to enable additional research and development, the SEC Lab was expanded in 2013. The expansion included a new rainfall simulator building that houses three 8-feet by 40-feet variable slope soil fill test beds that accommodate any slope up to 2:1 (50%).
Adjacent to the new rainfall simulator building is a 1,500-foot covered sediment bed preparation area. This area creates a dry work space for storage of the new larger test beds during inclement weather. The expansion also includes a 40-foot by 60-foot soil storage building that allows for test bed preparation during rain events without affecting antecedent soil moisture, a critical factor in the indoor testing procedure.
The existing rainfall building was also being modified to expedite testing. The building was originally designed for manual sediment collection. In fall 2012, the existing sediment collection pits were expanded to enable the use of larger collection devices to reduce the amount of testing time required. To handle the larger loads, a 4-ton overhead bridge crane also was installed.
These 10 soil channels are 85 ft long with a trapezoidal shape and 1:1 side slopes – four with a centerline gradient of 3% and six with a 7% gradient.
Bench Scale Testing Equipment
Bench scale capabilities of the lab include bench scale slope testing and bench scale channel erosion testing equipment. This bench scale equipment is useful to evaluate performance of erosion control materials and compare bench scale results to full scale and large scale testing data.
Climate Controlled Greenhouse
A 2,800-square-foot climate-controlled greenhouse is used for growing approved seed mixes free from outside contaminants such as weeds. The climate control characteristics of the greenhouse also provide the SEC lab with the ability to test vegetation establishment on a year-round basis. The erosion and sediment control materials are tested in the greenhouse to determine their ability to establish perennial vegetative cover. The purpose is to understand how materials foster establishment of vegetative cover and how vegetation contributes to the control of surface erosion on slopes and in channels.
Overland/Sheet Flow Test Flume
The 65 ft concrete channel has a potable water reservoir and weir designed to simulate overland sheet flow for water quality testing. The channel can be filled with specified soil type and gradient.
Potable Water Tank
This 5000 gallon potable water tank can be used for water quality testing.
Sediment Retention Device Test Flume
The sediment retention device testing flume has a 12 ft upper flume and a 2 ft lower flume. A 4 ft wide soil-filled area is used to install the material according to manufacturer’s specifications. The reservoir continually mixes a slurry of well-graded artificial sediment. Turbidity meters monitor influent and effluent concentrations. Flowmeters are also used to monitor influent and effluent flow rates.
Small Footprint Stormwater Quality Structure
This concrete structure is designed to hold one acre inch of water and is designed to capture and treat sediment laden water for various time periods. Samplers and flowmeters used in conjunction with this device, monitor settlement rates of sediment and also allow water to be slowly released, skimmed off the surface, or held for a designated time period and then released. One key feature of this device is a solar powered electronic butterfly valve that allows for precise capture and release of water in the structure.
The 25-foot-tall, L-shaped embankment of 1,000 linear feet has both clay and sand soil sections built with 2:1 and 3:1 slopes per highway specifications.
Variable Slope Channel Flume
The 30 ft outdoor, variable slope channel flume is used for testing the performance capabilities of flexible channel liner materials at a range of stress flows. The current protocol tests products and materials up to a maximun stress flow of 12 psf (575 Pa).