Site: Natural Gas Wellhead Site (Colorado)
Contaminant: BTEX (LNAPL/free product present)
Soil Type: Well-sorted sand and gravel
Injection Cost: $13,000 (material & labor):
Size of Trenches: Approximately 5 feet by 55 feet
No. of Trenches: 5 (4 at size above, 1 added in the field - ~5 feet by 21 feet
Depth of Trench: ~7 feet below ground surface
A release occurred from a tank near the “levee.” The area between the levee and the river is a sand bar composed of well-sorted sand and gravel. The contamination from the spill was pushed by strong groundwater current along levee toward the river. The trenches were constructed to make a set of bio-reactor cells for groundwater to travel through so that the water entering the river will be clean. Since treatment, the groundwater entering the river appears to be clean, and contaminant levels in the upgradient monitor wells are trending down.