3 Reasons to Require Standardized Testing for Sediment Barrier BMPs
Just how effective are silt fence, straw wattle, and alternative sediment barriers in sediment retention? This is an important question that we feel is not being answered completely by manufacturing companies. Additionally, we find that many contractors or stormwater professionals do not look into the effectiveness claims on the products that they are purchasing. Ultimately, that can cost time and money when a sediment control BMP doesn’t live up to claims or expectations.
Possible problems with existing field test claims
Why is there so little test data to support the effectiveness of sediment retention devices (SRDs)? Unfortunately, the claims that you hear are often unstandardized or inaccurate. Most companies selling these SRDs offer limited or no documentation to support the effectiveness of their products. When there is test data provided, these problems often arise:
- The test data that is made available can be developed using widely different protocols and sometimes incomplete data. For example, some tests are performed on a small flume rather than larger scale testing that incorporates the recommended installation for the product.
- Some testing only provides a snapshot of time rather representing the whole rain event.
- Some companies have even made claims using test data that was taken part way through the test, rather than the results after the test was finished.
We believe that the answer to these problems is standardized field testing.
Before choosing a sediment barrier, consider these 3 reasons to require standardized testing:
Don’t just take the manufacturer’s word for it. Require standardized field testing before choosing a sediment barrier.
- Get the results you expected.
You should be able to compare the expected effectiveness of your sediment barrier with actual sampling from your site. The total suspended solids (TSS) being discharged should not be a surprise.
- Get your money’s worth.
Your stormwater pollution prevention plan (SWPPP) is put in place to keep your site in compliance. If you are paying money for a product that is supposed to keep you compliant, it should perform well.
- You shouldn’t have to settle.
We encourage you to develop standards for minimum effectiveness. What is the lowest percentage that you will allow? Check into the product’s field testing and make sure it meets your requirements.
Standardized Test Solution – ASTM D7351
There is currently a standard test method for determination of sediment retention device effectiveness in sheet flow applications: ASTM D7351. The American Society for Testing and Materials (ASTM) describes it best: “This test method quantifies the ability of a sediment retention device (SRD) to retain eroded sediments caused by sheet flowing water under full-scale conditions. The effectiveness of SRDs is installation dependent. Thus, replicating field installation techniques is an important aspect of this test method. This test method is full-scale and therefore, appropriate as an indication of product performance, for general comparison of product capabilities, and for assessment of product installation techniques.”
This ASTM D7351 is the most thorough and complete test option specifically for sediment barriers. ASTM offers other related tests, for example D5141, that some manufacturers might use. Tests like this give good statistics and sound impressive, but are not the best category for sediment barriers as they do not fully encompass the entire situation of sediment retention. The D5141 by example only measures the filtering power of the material used for filtration. It does not test the entire product in its installation “habitat.” The ASTM website even notes that the D5141 is only optimum “if it is not necessary to simulate field installation conditions.” This is why we are confident that the ASTM D7351 is the best standard test method for sediment barriers and other SRDs, and we would encourage you to look for it.
In the end, we find:
- Manufacturers are often not providing data to support their sediment filtration claims.
- The data that some provide is flawed.
- It is important to require documentation for the products you are purchasing.
- There is a standardized test that you can require for sediment barriers.
With these truths lined up, why shouldn’t you expect the manufacturers of SRDs to publish ASTM D7351 test results? At what point should the industry develop minimum baseline standards for installed sediment barriers? We can’t answer all of these questions for you, but we hope we have provided you with enough concrete information to do your own deciding.
Here at WTB, Inc., we opted to have our Heavyweight DuraWattle™ field tested with ASTM D7351. If you would like to see the full report, click here. We tested at 96.6% sediment filtration and 58% turbidity reduction. When installed correctly, our customers have found consistency with the DuraWattle™ as an effective sediment barrier. If you would like to request a quote, click here.