Project: Oak Hill Stormwater Environmental Impact
Client: Oak Hill Cemetery
Location: Nyack, New York
Services: Stormwater; Environmental Advocacy
In 2014, Oak Hill Cemetery (Oak Hill) began experiencing flooding caused by stormwater discharges from an improperly designed stormwater detention basin (basin) installed at a neighboring apartment complex. Overflows from the basin traveled overland onto Oak Hill’s property, flooding grave sites, making routine maintenance impossible, and prohibiting access for visitors. Oak Hill turned to CEA Engineers for technical expertise to remedy the flooding. CEA Engineers analyzed the cause of the flooding, identified the design flaws in the basin, and coordinated redesign of the basin with the apartment complex’s engineering firm to eliminate the risk of flooding.
In 2018, Oak Hill again turned to CEA Engineers for assistance, when the apartment complex planned an expansion consisting of a new building, roadways, and landscaped areas. The expansion required installation of a new stormwater management system, including drywells and a redesigned basin. While the project was before the local planning board, CEA Engineers analyzed the adequacy of the proposed stormwater management system and construction erosion and sediment control (E&SC) plan and identified the potential for adverse impacts to Oak Hill caused by stormwater discharges from the proposed expansion. CEA Engineer’s review included analysis of the Hydrocad model runs used to design the stormwater management system. Our review identified numerous flaws in the E&SC Plan and design of the proposed stormwater management system:
- Failures to follow New York State Department of Environmental Conservation (NYSDEC) design standards for the proposed drywell system
- Errors in the model runs
- Baseless design assumptions
- Direction of overflow discharges from the drywell system and basin toward Oak Hill’s property, creating future risks of flooding and property damage
- Failure to perform necessary soil infiltration/percolation tests
- Improperly designed and located E&SC practices
- Improper collection and conveyance of off-site stormwater flows that entered the construction area
CEA Engineers submitted a technical report to the local Planning Board on behalf of Oak Hill in support of their opposition to the apartment complex’s proposed expansion. The technical report discussed the numerous flaws and inadequacies CEA Engineers identified in its analysis. CEA Engineers then participated in negotiations with the apartment complex’s engineering firm. CEA Engineers successfully achieved the redesign of the proposed stormwater management system to redirect overflows from the drywell system and basin that eliminated the potential for any future stormwater discharges from the apartment complex to impact Oak Hill. Errors in the E&SC identified by CEA Engineers were also successfully corrected.