Low impact development sand filter media replacement: Costs and effect on pollutant removal efficiencies

Sand filter basins are widely utilized as a Best Management Practice (BMP) in Texas and other regions for stormwater mitigation. Efficient operation of these systems depends on routine inspections and maintenance. The performance of the sand filter's contaminant removal before and after media maintenance was evaluated along with cost variations for the maintenance activities. Maintenance concerns were also identified in inspection records from 2017 to 2022 for sand filter and sedimentation basins treating areas over the contributing zone of Edwards Aquifer (within Bexar County, TX). The results indicated minimal change in the removal ability for suspended solids after a replacement of the top media layer. A decline in removal for parameters including total coliforms, total nickel and total lead suggests disruption of biofilm layer on the media surface (schmutzdecke) during maintenance. Media replacement costs are rarely documented for sand filter BMPs but must be incurred to satisfy regulatory guidelines. The average total cost of media replacement by private firms or government entities in the local area was $18,462 ± 6325 which included removal and replacement of the top layer of sand and disposal of the removed sand off site.