The Chester County Technical College Highschool (Brandywine Campus) has been experiencing sink holes within one of the basins. During rain events, two stormwater pipes drain into the basin which allows the water to percolate into the soils below and cause sinkholes. To reduce the occurrence of sinkholes within Basin #4, EEI designed the lining for the basin. The impervious liner extended to the 3 existing concrete retaining walls and underneath the berm adjacent to the roadway. The design allowed for the existing to stormwater structures to be removed and reinstalled at the same location and inverts. The impervious liner will keep the water from infiltrating the subgrade. EEI was also on site to ensure the lining system and basin components were installed accordingly to specifications.