Nov 2009 - Colorado State Univ. Ft. Collins, Co.
Fully Vegetated ScourStop Research Project
Colorado State University in Fort Collins, CO, is a 50 year leader in hydraulic testing, does full-scale, flume testing. CSU was the prime research lab for the federal highway hydraulics specifications guidelines – HEC 13, 14, and 15.
After a year for vegetative growth beginning in late 2009, Colorado State University under the supervision of Dr. Christopher Thornton, Director of the Hydraulics Cab, began hydraulics testing on ScourStop Transition Mats. The research was done on the CSU steep flume (2:1 Slope) with high volume water flows(110cts) from Horsetooth Reservoir.
Fully-vegetated ScourStop transition mats prior to insertion into steep flume
Profile View of test facility and planter box
Colorado State University staff performed 6 - 30 min. duration progressive flow tests, as they ramped up to the maximum flow capacity of the facility. On the final 7th test, CSU ran a 1 hr duration, 110 cfs flow test, schieving performance levels of more than 31ft per second. Test #6 actually incurred the greatest shear stress of more than 16 lbs per sq. ft. These numbers are equivilant to many Articulated Concrete Block (ACB) performance levels.
First, we did not design the product-testing procedure to obtain specific results. Most TRMs tested are fully-vegetated - the root system is dense and there is 8-12 inches of vegetative growth on top. Those results are then used as the basis for performance criteria and design specifications.
- The potential problem arises in the 6-10 weeks, or more, between the installation date and the fully-vegetated date. How will the TRM perform in an unvegetated or thinly vegetated state?
CSU set up the test same construction conditions you have on your project sites. They purchased plain field sod at 9 in the morning. It was installed by noon and the testing was started under the same construction conditions encountered in a normal field installation.
- They utilized one of our installation modes: a sod and ScourStop combination for the testing. Sod protects the soil particles and provides instant vegetation, with no risk of poor seed germination. We are pioneering this installation mode as a paradigm shift in design to minimize failures and maximize effectiveness of the investment and protection of the environment.
Second, CSU utilized the highest level test parameter – a mere half inch soil erosion – as the critical measure.
The first test started at 8 feet per second where 600,000 gallons were discharged in 30 minutes over the test site. They stopped and measured the test site: no erosion.
- Next, they brought the test up to 12 feet per second, 900,000 gallons in 30 minutes. Stopped the test, measured the test site; no erosion.
- And finally, they ramped it up to 16 feet per second, 1.2 million gallons of water in 30 minutes…and still no erosion.
All-told, a total of 2.7 million gallons of water passed over ScourStop with no erosion. Remember the ½ inch soil erosion criteria! 2.7 Million gallons is the equivalent of over 9 feet of water on a football field, discharged out of a 33 inch pipe in 90 minutes. 16 feet per second is more than twice the stress you would design in the real world.
Local tests are not necessary
One of the main points we hoped to achieve working with CSU and performing extreme stress applications was to emphasize that local tests are not necessary. Science is necessary. With a local test you don’t know what the flow was, how many events there were, nor what the volume was. There is no science with a local test. Additionally, civil engineers rarely design more than 8 feet per second. CSU more than doubled that standard. CSU provided a very reasonable test that mimics real life; instead of some gimmicked up test that you can’t trust!
Rip Rap Comparison at 16 feet per second.
To demonstrate the forces of 16 feet per second works in the real world, CSU also tested rip rap under the same conditions. They used 8 to 18 inch rip rap; up to 70 lb rocks, property installed per specification. They marked the rocks with white paint so we could see where they moved.
They ran the first test at 8 feet per second, and at that rate a scour area phalange pool was developing.
Next, they attempted to ramp the flow up to 12 feet per second and ran into slight mechanical problem, so they ran 10 feet per second for 30 minutes; causing a scour hole 8-10 inches deep – a failure by testing standards.
CSU then ramped the test up to 16 feet per second; resulting in a 4 foot high hydraulic jump, and erosive action for 30 minutes.
They ended up with a 3-foot deep scour hole surrounded a 3 foot high crater, moving all of the 70 lb rocks out of that scour area. 16 feet per second was a real world test that failed miserably by rock rip rap.
Additional Testing at Colorado State University
Many applications do not support using sod in the installation procedure. CSU also tested a ScourStop and high-strength TRM (rated at 5.5 fps unvegetated under the ˝ inch performance criteria) under their high stress conditions.
ScourStop was able to double this TRMs' performance rating to 11.8 feet per second – again at the ˝ inch soil erosion criteria! This unvegetated performance relates directly to construction site conditions – not some 'pie-in-the-sky' criteria increasing designer and client risk of failure.
Click here to see both a 4 page summary of the CSU research , and the full report .
Landmark is committed to providing defensible research and dependable fiels results prior to mass-marketing to out valued customers.
Landmark has invested in state-of-the-art technology and research for protecting shorelines from erosive wind and boat driven waves with ScourStop and appropriate soil covers.
Flume : 100 feet long, 8 feet wide, 8 feet tall
Sand Foundation Bed
Runnin 6inch waves
Mid-Size waves Crashing Slope
3ft wave crashing slope
3ft wave (side view)
Colorado State University Full Report Listing