Large-Scale Slope Erosion Testing ... - AASHTO - …

1 Large-Scale Slope Erosion Testing (ASTM D 6459) of Ero-Guard, Inc. EG-2S, Double Net Straw Blanket over Sandy Loam June 2010 Submitted to: AASHTO / ntpep 444 North Capitol Street, NW, Suite 249 Washington, 20001 Attn: Keith Platte, ntpep Submitted by: TRI/Environmental, Inc. 9063 Bee Caves Road Austin, TX 78733 C. Joel Sprague Project Manager June 25, 2010 Mr. Keith Platte AASHTO / ntpep 444 North Capitol Street, NW, Suite 249 Washington, 20001 E-mail: Subject: Large-Scale Slope Testing over Sandy Loam of Ero-Guard EG-2S, Double Net Straw Blanket, manufactured in Mapleton, MN. Dear Mr. Platte: This letter report presents the results for Large-Scale Slope Erosion tests performed on EG-2S, Double Net Straw Blanket, rolled Erosion control product (RECP), over sandy loam. Included are data developed for target rainfall intensities from 2 to 6 in/hr (5 to 15 cm/hr). All Testing work was performed in general accordance with the ASTM D 6459, Standard Test Method for Determination of Rolled Erosion control Product (RECP) Performance in Protecting Hillslopes from Rainfall-Induced Erosion .

2 Generated results were used to develop the following general cover factor (C-Factor) for the tested material: C-Factor EG-2S & staples/sy = for cumulative R-Factor < 231; Eqn: C = TRI is pleased to present this final report. Please feel free to call if we can answer any questions or provide any additional information. Sincerely, C. Joel Sprague, Senior Engineer Geosynthetics Services Division Cc: Sam Allen, Jarrett Nelson - TRI EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 2 Slope Testing REPORT EG-2S, Double Net Straw Blanket, over Sandy Loam Testing EQUIPMENT AND PROCEDURES Overview of Test and Apparatus TRI/Environmental, Inc.'s (TRI's) Large-Scale Slope Erosion Testing facility is located at the Denver Downs Research Farm in Anderson, SC. Testing oversight is provided by C. Joel Sprague, The Large-Scale Testing reported herein was performed in accordance with ASTM D 6459, on 3:1 slopes using loamy soil test plots measuring 40 ft long x 8 ft wide.

3 The simulated rainfall was produced by ten rain trees arranged around the perimeter of each test Slope . Each rain tree has four sprinkler heads atop a 15 ft riser pipe. The rainfall system has been calibrated prior to Testing to determine the number of sprinkler heads and associated pressure settings necessary to achieve target rainfall intensities and drop sizes. The target rainfall intensities are 2, 4, and 6 in/hr and are applied in sequence for 20 minutes each. Three replicate test slopes covered by the same rolled Erosion control product (RECP) submitted were tested. The Erosion resistance provided by the product tested is obtained by comparing the protected Slope results to control (bare soil) results. Tables and graphs of rainfall versus soil loss are generated from the accumulated data. Rolled Erosion control Product (RECP) The following information and index properties were determined from the supplied products.

4 Table 1. Tested Product Information & Index Properties Product Information and Index Property / Test Units Sampled Product Product Identification - EG-2S Manufacturer - Ero-Guard, Inc Manufacturing Plant Location - Mapleton, MN Lot number of sample - 31010 Fiber - Straw Netting Openings in x (approx) Stitching Spacing in (approx) Tensile Strength MD x XD (ASTM D 6818) lb/in x Tensile Elongation MD x XD (ASTM D 6818) % x Thickness (ASTM D 6525) mils 332 Light Penetration (ASTM D 6567) % cover Water Absorption (ASTM D 1117 & ECTC-TASC 00197) % Wt Change 218 Mass / Unit Area (ASTM D 6475) oz/sy Test Soil The test soil used in the test plots had the following characteristics. EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 3 Table 2. TRI-Loam Characteristics Soil Characteristic Test Method Value % Gravel ASTM D 422 0 % Sand 45 % Silt 35 % Clay 20 Liquid Limit, % ASTM D 4318 41 Plasticity Index, % 8 Soil Classification USDA Sandy Loam Soil Classification USCS Sandy silty clay (ML-CL) Preparation of the Test Slopes The test slopes undergo a standard preparation procedure prior to each Slope test.

5 First, any rills or depressions resulting from previous Testing are filled in with test soil and subject to heavy compaction. The entire test plot is then tilled to a depth not less than four inches. The test Slope is then raked to create a Slope that is smooth both side-to-side and top-to-bottom. Finally, a steel drum roller is rolled down-and-up the Slope 3 times proceeding from one side of the plot to the other. The submitted Erosion control product is then installed as directed by the client. Installation of Erosion control Product on Test Slopes As noted, the submitted Erosion control product was installed as directed by the client. For the tests reported herein, the RECP was anchored with staples per square yard. Specific Test Procedure Immediately prior to Testing , rain gauges are placed at the quarter points ( 10, 20, 30 ft) on the Slope . The Slope is then exposed to sequential 20-minute rainfalls having target intensities of 2, 4, and 6 inches per hour.

6 All runoff is collected during the Testing . Additionally, periodic sediment concentration grab samples are taken and runoff rate measurements are made. Between rainfall intensities, the rainfall is stopped and rainfall depth is read in the three rain gauges, valves are adjusted to facilitate the subsequent rainfall intensity, and empty collection vessels are positioned to collect subsequent runoff. After allowing for sediments to settle, water is decanted from the collected runoff. The remaining solids are used to determine bulk soil loss. Bulk soil loss is measured by drying all collected sediments. EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 4 Figure 1. Rainfall Testing Facility (set up for a control run) Figure 2. Typical Sampling Figure 3. Typical control Result Pictures of slopes prepared for Testing are shown in Figure 4.

7 Figure 4. Typical Prepared Soil Slope & RECP Installation Pictures of the eroded slopes are shown in Figures 5 thru 7. EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 5 Figure 5a. Test Slope #1 Start of the 2 in/hr Event Figure 5b. Test Slope #1 Start of the 4 in/hr Event Figure 5c. Test Slope #1 Nearing End of 6 in/hr Event Figure 5d. Test Slope #1 After 6 in/hr Event - RECP Removed Figure 6a. Test Slope #2 Start of the 2 in/hr Event Figure 6b. Test Slope #2 4 minutes into the 6 in/hr Event EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 6 Figure 6c. Test Slope #2 During 6 in/hr Event Figure 6d. Test Slope #2 After 6 in/hr Event - RECP Removed Figure 7a. Test Slope #3 Prior to start of 6 in/hr Event Figure 7b. Test Slope #3 13 minutes into the 6 in/hr Event Figure 7c. Test Slope #3 After 6 in/hr Event Figure 7d.

8 Test Slope #3 After 6 in/hr Event RECP Removed EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 7 TEST RESULTS Total soil loss and the associated actual rainfall depth measured during the Testing are the principle data used to determine the performance of the product tested. This data is entered into a spreadsheet that transforms the rainfall depth into an R-Factor and the total soil loss into soil loss per acre as typically used in the Revised Universal Soil Loss Equation. In accordance with the test procedure, a test is stopped in the event of catastrophic soil loss, as determined by the lab. In such a case, an assumed end-of-test worst-case soil loss based on the control runs is used in lieu of the soil loss just prior to failure. The tests reported herein experienced no catastrophic Slope failure. In all cases, the soil loss and associated rainfall data for both protected and control conditions are used to develop a normalized cumulative graph of R-Factor versus C-Factor (R factor = total kinetic energy of the storm (E) times its maximum 30-minute Intensity (I)).

9 The normalized cumulative R-Factor calculated for the target test events: 2 in/hr for 20 minutes + 4 in/hr for 20 minutes + 6 in/hr for 20 minutes, is R = 231. This normalized result facilitates product-to-product comparison of test results at a common point of the storm event. Graphs of R-Factor versus C-Factor for the protected condition and Soil Loss versus C-Factor for the control condition are shown in Figures 8 and 9, respectively. Figure 8 includes the best regression line fit to the test data to facilitate the determination of the C-factor. Linear (R2= ), power (R2= ), and exponential (R2= ) fits were evaluated. Table 3. Summary Data Table Protected Slopes Slope # & Product Test # (run # - target intensity) Intensity (in/hr) Runoff (gallons) Cumm. R-Factor Soil Loss (lbs/plot/event) Cumm. Soil Loss (Tons/Acre) control Soil Loss at Cumm. R-Factor (Tons/Acre) Cumm. C-Factor 1 EG-2S 1-2 1-4 1-6 2 EG-2S 2-2 2-4 2-6 3 EG-2S 3-2 3-4 3-6 Using the test procedure and data evaluation technique described herein, the C-Factor shown in Table 4 was determined using the following equation: C = mC / K where mC = Slope of the protected soil loss regression line; and K = the soil erosivity determined from bare soil Testing = mK / LSCP Where mK = Slope of the bare soil loss regression line; LS = topographic factor = for 8 x 40 ft Slope ; C = cover factor = for bare soil; P = management practice factor = for bare soil.

10 Table 4. Overall C-Factor Product C-Factor Calculation EG-2S & staples / sy C = EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 8 y = = vs. R-Factor(EG-2S on TRI-Loam; 3:1 Slope ; Anchorage: pins / sy)2 + 4 + 6 in/hr: R = 231C = all 2, 4, and 6 in/hr C-Factors from all slopes. Figure 8. R-Factor vs. C-Factor Tested Product y = = Loss (Tons/Acre)R-FactorSoil Loss vs R-Factor ( control Testing of TRI-Loam; 3:1 Slope ) Slope 1 -21 Apr10 Slope 2 -23 Apr10 Slope 3 -23 Apr10 Slope 1 -10/29/09 Slope 2 -8/17/09 Slope 3 -10/29/09 Slope 1 -16 Apr10 Slope 2 -16 Apr10 Slope 3 -8 Apr10 AllLinear (All)C= m / ( *K)K= m / (C* )K= / ( * ) = cummulative R-Factor calculated for the following events: 2 in/hr for 20 min + 4 in/hr for 20 min + 6 in/hr for 20 min, is R = 231and the associated soil loss is tons/acre Figure 9. R-Factor vs. Soil Loss control Tests EG-2S, Double Net Straw Blanket, over Sandy Loam - Slope Erosion Testing for ntpep June 25, 2010 Appendix APPENDIX A RECORDED DATA Test Record Sheets Sediment Concentration Data Runoff Data Soil Moisture Content Soil Loss Tables #TimeStart Rain:10:59 AM111:02 Sampling interval:0:03211:05 Rain Time (min) Time (min) :08 Descr.