Plugging and abandonment of Interceptor Trench System (French drain system) located on the former Farmland Industries Nitrogen Fertilizer Plant. The perched groundwater interceptor trenches/sumps consist of a series of trenches installed into shallow aquitard composed of low-permeability terrace deposits. The Northeast Ponds trench system consists of an estimated 6,280 linear feet of 4” diameter perforated pipe installed in trenches connecting to five sumps (North, Northwest, Northeast, South, and Southeast). The five sumps and associated cleanouts range in depth from 18 feet to 21 feet below ground surface with a total estimated vertical footage of 120 feet. The Central Ponds (CP) interceptor trench system consists of an estimated 1,325 linear feet of 6” diameter perforated HDPE pipe connecting to a 24” sump that is 31 feet below ground surface. The CP interceptor trench contains twelve 6” diameter cleanouts with a combined estimated vertical footage of 180 feet. The City of Lawrence will contract a Kansas-licensed water well contractor, or other qualified vendor, to plug and abandon the sumps and interceptor trench piping in-place. The contractor will remove pumps and drop-piping from the sumps to prepare the trenches for abandonment. The contractor will fill the lateral piping and sumps by pumping a KDHE-approved grout into the piping and sumps. All sumps and clean outs will be filled with grout to a minimum of 3 feet below ground surface. The nitrogen-impacted water in the piping and sumps that is displaced by grout will be captured and transferred to the Farmland Overflow Pond. The contractor will allow the grout to settle for 24 hours and top off with grout to a minimum of three (3) feet below ground surface. The remaining exposed sump casings and clean-out casings will be cut off three (3) feet below ground surface and disposed of as solid waste in an approved landfill. The remaining voids will be filled with borrow soils located on the facility property.
