CONCLUSION: Gator Guard Wattles Have 20-Times Less Soil Loss
Than Straw Wattles
About the Tests: Tests were performed at San Diego State University - Soil Erosion Research Laboratory SDSU-SERL in 2001 and 2008 using the same basic equipment, but different rainfall intensities.
The straw wattle tests performed in 2001 were adapted from portions of the testing protocols developed for Slope Stabilization for Temporary Slopes - SSTS study (Caltrans 1999) and the Erosion Control Pilot Study - ECPS (Caltrans 2000). Simulated Rainfall was applied at 0.2-in/hr for 30-min, 1.6-in/hr for 40-min, and 0.2-in/hr for 30-min, for a total precipitation of 1.2-inches in 100-minutes. This rainfall represents a 10-yr storm event as modeled from L.A. Basin hydrologic data.
The Gator Guard wattle tests performed in 2008 are based on rainfall intensities currently under review by ASTM for slope interrupter type BMP’s. Simulated Rainfall was applied at 2-in/hr for 20-min, 4-in/hr for 30-min, and 6-in/hr for 30-min, for a total precipitation of 5.7-inches in 80-minutes. This rainfall is much more intense than the 2001 experiments, with 4.5 times the rainfall applied and 15 times the sediment eroded from the slope. THESE EXTREME TEST INTENSITIES TAKE PRODUCTS BEYOND PRACTICAL LIMITS to fully evaluate performance and limitations of each product tested.
Although the above tests are not directly comparable, the results can be evaluated for an L.A. Basin 10-yr storm equivalent based on soil loss for the no-treatment experiments. The 2001 no-treatment tests had a 45kg soil loss in 100-minutes, while the 2008 no-treatment tests had a 45-kg soil loss in 16-minutes. Corresponding results for the 2001 straw wattle test was 20-kg soil loss in 100-minutes compared to 1-kg of soil loss in 16-minutes for the 2008 Gator Guard test. Each of the above test results represents the mean values for three separate test runs. Differences in storm intensity tend to skew the results in favor of the 2001 straw wattle tests, suggesting that Gator Guard wattle soil loss could be even less than 1-kg using actual 2001 test rainfall intensities and durations.
The complete SDSU report for Gator Guard tests is available in pdf format at www.gatorguard.com. A 19-second must-see time-lapse test video and test photos are also available.
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