In an effort to replenish local groundwater supplies and reduce potential pollutant discharges to the municipal storm sewer system, CASC Engineering & Consulting retrofitted a 1.7 acre commercial development office site to capture and infiltrate runoff.
Despite the low permeability of the top soil, low impact development (LID) BMPs were implemented to cover more than 100% of the site. The LID BMPs include two infiltration basins, two infiltration trenches, two areas of pervious paving, one area of pervious interlocking pavers, one roof-runoff diversion system and three areas of turf conversion. These practices reduced the site’s storm water discharges, increased infiltration and reduce potable water.
Through the project, employees gained a better understanding of runoff reduction by creating drainage management areas and using the rational equation to compare pre- and post-improvement drainage conditions.
Before the retrofit, 100% of the site drained directly into the street or adjacent creek. Now, only 14,983 sq ft drain to those areas, which is a 79.6% reduction. There has been an 11% reduction in runoff capture design volume. The project also reduced water usage by removing 10,877 sq ft of turf and installed drought tolerant landscaping.
“We eliminated over 11,850 sq ft out of the total 21,200 sq ft of water-loving turf and converted it into a system that virtually eliminated storm water discharges from the site and will contribute to the recharge of the local groundwater basin,” said Chris Sidor, project engineer with CASC.