Civil Engineering and Building Design Project Related Experiences

Shongum Lake Property Owner's Association, Shongum Lake Dam is located in the Township of Randolph, Morris County, New Jersey. The dam is situated at the southwesterly side of Shongum Road, immediately southeast of Radtke Road and southwest of Waterview Lane and crosses Den Brook to impound Shongum Lake. The subject dam is currently classified as a Class II dam structure by the New Jersey Department of Environmental Protection (NJDEP). The Entech Group, Inc., on behalf of the Shongum Lake Property Owner's Association prepared and submitted to the NJDEP an Emergency Action Plan, Operation and Maintenance Manual, Dam Breach Analysis and Inundation Mapping to comply with the requirements of the New Jersey Dam Safety Standards, N.J.A.C. 7:20-1.1 et. seq. Standards (Standards). Results of the aforementioned Dam Breach Analysis revealed the need to conduct additional studies to evaluate and classify downstream hazards associated with the Shongum Lake Dam.

These additional studies (the results of which are the subject of this report), include, among other things, the further refinement of previously prepared hydrologic/hydraulic data, along with computer models and evaluation of downstream hazards that demonstrate why Shongum Lake Dam should be re-classified to a Class I - High Hazard Potential dam. The Standards further require at N.J.A.C 7:20-1.9(a) that all Class I dams have sufficient spillway capacity to safely pass the Probable Maximum Precipitation (PMP) storm event. However, due to existing features and constraints surrounding Shongum Lake Dam there is a limited reasonable area to reconstruct a spillway to accommodate the Probable Maximum Precipitation (PMP) storm event. Therefore, various storm events between the 1/2 PMP and the PMP were modeled until it was determined that there was no significant change in the Depth of Velocity Flood Danger Level Relationship from the breach to no-breach conditions, as presented in the Depth versus Velocity Charts in the Bureau of Reclamation "Downstream Hazard Classification Guidelines", dated 1988. The eighteen and three-quarter (18 3/4) inch twenty-four (24) hour storm was determined to be the appropriate Spillway Design Storm, based on the aforementioned criteria.

Additional documents and materials were prepared and submitted to NJDEP detailing the process for determining the reclassification of Shongum Lake Dam to a Class I - High Hazard Potential dam and to support a proposed reduction in the requirement Spillway Design Storm to an eighteen and three-quarter inch (18 3/4) storm in 24-hour period. The studies performed for the preparation of this report, the revised inundation mapping and the Hazard Classification determination were performed in general accordance with the New Jersey Dam Safety Standards, N.J.A.C. 7:20-1.1 et. seq., the Bureau of Reclamation "Downstream Hazard Classification Guidelines" (dated 1988) and prevailing professional standards of care.

Documentation and materials were also prepared for future submission to the New Jersey Department of Environmental Protection (NJDEP), Land Use Regulation Program (LURP) for the determination of Wetlands and State Open Water limits. Entech also prepared the Biannual Dam Inspections Reports, as well as the Construction Plans, Details and Specifications for the proposed Dam Structure Improvements to include specifications associated with the proper transportation and disposal of dredge materials.