Opinion ID: 47918
Heading Depth: 3
Heading Rank: 1

Heading: Adverse Effects on Soils and Flood Capacity

Text: 23 The Corps's EA predicts that the project will have substantial, long-term, adverse effects on project site soils, including: 1) creation of anoxic and anaerobic conditions 5 due to clearing, grading, excavation, and filling; 2) possible impairment of subsurface drainage due to substrate compaction; 6 and 3) decreased aquifer recharge capability due to an increase in impervious surfaces. 7 All of the above work could contribute to a possible reduction in the site's flood control functions, including increased surface runoff volume and rate; reduced subsurface lateral flow, storage, and recharge; and reduced filtration. 24 In discussing the role of mitigation in reducing these problems, the EA states that the drainage plan incorporated into the development relies on a 100-foot vegetated buffer zone for flood water storage as well as creating detention areas. Additionally, the plan would raise the elevation of the major road. The EA also notes that the drainage plan meets St. Tammany Parish requirements. The EA asserts, without data or analysis, that the project as mitigated should have minimal [e]ffect on flooding within the scope of a 25-year storm, although storms in categories above a 25-year event could flood the development. 8 25