1.12 BMP C125 - Compost
The purpose of compost is to help establish vegetation and filter stormwater thus removing fine sediment and other contaminants. Compost can be used alone as a compost blanket, as a berm, or inside a sock.
Do not use if stormwater will discharge to a nutrient sensitive waterbody.
Do not use as a stormwater system inlet protection measure.
1.12.3 Design and Installation Specifications
Meet the definition for “composted material” per WAC 173-350-100 and comply with standards in WAC 173-350-220, except the feedstock may contain biosolids or manure feedstocks.
Be coarse compost meeting the following size gradations (by dry weight) when tested in accordance with the U.S. Composting Council “Test Methods for the Examination of Compost and Composting” (TMECC) Test Method 02.02-B.
Have no visible water or dust during handling.
Have soil organic matter content of 40% to 65%.
Have a carbon to nitrogen ratio below 25:1. Carbon to nitrogen ratio may be as high as 35:1 for plantings composed entirely of plants native to the Puget Sound Lowlands region.
Do not use near wetlands or phosphorus impaired waterbodies.
Compost can be later tilled into soils to help meet the requirements of BMP L613 - Post-Construction Soil Quality and Depth as required per Minimum Requirement 5 - Onsite Stormwater Management
City of Tacoma TAGRO Potting Soil can be used as an alternative to the compost component in BMP C125 - Compost.
Compost specifications are also contained in A900 - Compost.
Compost blankets are simply compost blanketed over an area.
Compost can be blown onto slopes up to 2:1 or spread by hand on shallower slopes.
Compost can be mixed with a seed mix to ensure rapid vegetation.
Compost does not need to be removed after construction phase unless required by the Erosion and Sediment Control Lead.
Compost berms are a perimeter sediment control that can be used instead of silt fence.
Do not use compost berms on steep slopes.
Berm width shall be a minimum of 2 feet.
Berm height shall be a minimum of 12 inches.
Berm width shall be twice the berm height.
Compost can be blown in place or placed by front-end loader.
Compost should be spread over proposed landscaped section when construction is complete to aid in revegetation.
Compost socks are similar to straw wattles.
Sock material that is biodegradable will last up to 6 months and can be used for soil amendment after 6 months.
Sock material that is non-biodegradable must be removed after construction is complete.
Place socks perpendicular to flow.
Walk socks in place to ensure good soil contact.
Install wooden stakes every 12” on steep slopes or every 24” on shallow slopes
Inspect compost berm regularly.
Ensure vehicular traffic does not cross berm and track compost offsite. If this occurs, sweep compost immediately.
Do not allow erosion or concentrated runoff under or around the barrier.
Inspect the socks after each rainfall and repair any socks that tear or are not abutting the ground.