This silt fence was installed when a storage facility was constructed behind my house. My kids were preschoolers; now they are college age. Why was this installed since everything is level? Why was it never removed? Was this the right choice for a perimeter control BMP? Silt fence is the “go-to” perimeter control. Should it be? There are so many options available other than silt fence: Forest duff and vegetation berm, burlap silt fence with wooden stakes, compost berm, straw wattles, all of which could be left in place to biodegrade after the project is completed.
It doesn’t matter where I go, I always see some type of construction
erosion issue. I went to visit relatives in Portland, Maine, flying in and out
of Boston Logan International. In the terminal, waiting for my flight back
home, I saw a construction project on the ramp; it had rained a few says before,
hard. Obviously, the stockpile had not been covered before the storm and
sediment washed off the pile into the drain.
I work at an airport that operates under strict turbidity
effluent limits; here is how we do this kind of work:
(1) rarely do we allow stockpiles on the ramp because we rarely
reuse the excavated material (it is either contaminated, unsuitable or doesn’t
meet current FAA requirements); it is direct loaded into trucks and hauled off.
When we do stockpile, we place dirt on plastic and cover it with plastic, using
lots of sand bags to secure it from jet blast and wind.
(2) work areas are always isolated so there is no runoff from
the site. Normally, we use four-inch extruded asphalt curbing along the base of
the jersey barriers. Rolled hot mix asphalt (HMA) is used at the entrance point
so water is contained but vehicles can access the site. Water that builds up inside the curbing is
pumped back into the excavation if clean, or a tank if contaminated.
I should have
mentioned that we also have strict sediment trackout requirements: no visible
sediment leaves the site at any time.
This is both because of the effluent limits and for safety reasons; dirt
and debris that gets sucked up into a jet engine is damaging and possibly
deadly.
Lastly, I am
not casting aspersions on the folks at Logan; I don’t know their situation,
permits, drainage system, or tolerance for risk. Because of my situation, I have low risk tolerance
for potential non-compliance with our permit and I notice when something would
cause me grief at my airport.
I’m not a big fan of the “Grizzly” method of trackout prevention. My standard is “No visible trackout” and these have never met that standard. Preventing tires from getting dirty in the first place is still the best BMP!
I am always looking for products and materials that achieve the goal of environmentally friendly erosion controls, such as this reusable best management practice.
Specification Materials A. Berm shall be a minimum 6 inches high and 10 feet long and made of 10 mil polyurethane or 22 oz. PVC.
Construction Requirements Water Filled Diversion Berms a. Water filled diversion berms shall be installed such that offsite water is prevented from entering the job site and site water is kept within the project boundary. b. Berms may be used to prevent contaminants and water from entering catch basins. c. Berms may be used on impervious surfaces.
Payment O. Payment for “TESC – Water Filled Diversion Berms” will be made at the contract unit price per each per month as stated in the Schedule of Unit Prices, and shall be full compensation for furnishing the specified diversion berms. The unit price per each shall include the cost of mobilization/demobilization, cleaning, hauling and all incidentals for the number of diversion berms required by the Engineer for the duration of the contract.
I am trying to get to 100% biodegradable, recycled, reusable, recyclable, low impact best management practices. I have used burlap fabric fence several times, anytime it makes sense, really. I use it whenever I can leave it in place to degrade, like on habitat or wetland work. In one of the photos, plastic zip ties are used to attach the fabric to the wooden stakes; this is a mistake and has been changed to staples in the specification.
Biofence Specification
Materials U. BIOFENCE A. Biofence shall consist of 7 ounce or heavier uncoated burlap fabric at least 36 inches wide and 100 feet long. Wood stakes dimensions shall be a minimum 1 1/8 x 11/8 inches by 42 inches high.
Construction Requirements 18. Biofence a. Stakes shall be driven into the ground a minimum of 12 inches and be spaced no more than 6 feet apart. b. Fence ends shall be joined by wrapping ends together around a post 3 times and driven into the ground. c. Burlap fabric shall be attached to the post in at least 3 places using staples or other method approved by the Engineer. d. When used as a barrier fence, fabric shall not be trenched into the ground. When used as a silt fence, a minimum 8 inch flap shall be left at the bottom and held in place with straw wattles staked in as detailed in item 9 above.
Payment C. Payment for “TESC – Biofence” will be made at the contract unit price per linear foot as stated in the Schedule of Unit Prices and shall be full compensation for furnishing all labor, equipment, materials and tools necessary to complete the installation of the biofence as detailed on the drawings or as directed by the Engineer and specified herein. The unit price shall include all maintenance, the removal of biofence, and restoration of the area at the completion of the work
Walking around South Congress district south of downtown Austin, I discovered a new best management practice-horizontal silt fence. This makes access to the work area so much easier than if vertical silt fence was used. Fortunately no rain in the near future.
One of the most difficult things to manage on a construction project, especially a road project, is preventing mud from being tracked off the job. This video illustrates the use of a water-filled tire bath along with a rock entrance road and rock and asphalt exit onto existing road surface. Tire baths are useful when the there is a minimal amount of traffic leaving the project. Tire baths require a lot of maintenance including water changes and sediment removal.
Check dams need to be installed so that the center point of the dam is at least 8 inches lower than the outside edges; 12 inches in areas where intense rainfall occurs. If the center point is higher than the outer edges, water will run around the dam and erode the side slopes of the ditch, causing erosion. See Video.
