Infiltration Practices

Infiltration practices return runoff to the ground instead of a pipe: stone-filled trenches, excavated basins and porous pavement that store a storm in void space and let it percolate into the subsoil. When soils cooperate, nothing else matches them — median monitored removal sits near 95 percent for sediment and 80 percent for phosphorus, recharge obligations are met automatically, and there is no surface footprint to mow. The catch is that soils rarely cooperate: these practices demand measured infiltration rates of at least half an inch per hour, several feet of separation to the seasonal water table, and strict exclusion of stormwater hotspot runoff because whatever goes in reaches groundwater. They also clog without disciplined pretreatment and construction-phase protection — the historic failure rates trace almost entirely to sediment let in too early. The sheets in this group cover feasibility screening, sizing, pretreatment chains and the observation-well monitoring that proves a trench is still alive.