LKB is currently providing design services to NYSOPRHP for work at Hempstead Lake State Park. The Hempstead Lake Dam project requires an Engineering Assessment of the current conditions at the historic Hempstead Lake Dam, and the smaller upstream Northwest Pond Dam, to determine how to bring these structures into compliance with current NYSDEC dam safety regulations. The Engineering Assessment Report includes hydraulic and hydrological analyses of the 12.85 square mile Mill River Watershed that empties into Hempstead Lake and surrounding ponds, ultimately emptying into Mill River. We are currently designing improvements to the gatehouse outlet structure to bring it into compliance with state and federal regulations.
As part of the Engineering Assessment, the hydrological analysis was performed using the HEC-HMS program to determine peak flows through the watershed for variously designed storms. Hydraulic analysis was performed using WMS and the HEC-RAS program to determine the resultant water surface elevations and limits of flooding. The hydraulic analysis includes models of existing and alternative proposed conditions. A safety inspection of the dam was also performed leading to development of a tree removal plan.
LKB also developed an Inspection and Maintenance Plan for the dam, as well as an Emergency Action Plan, which will be updated once the proposed conditions have been established. The scope of this project has expanded to coordinate modeling efforts with GOSR’s Living With The Bay project. Since LKB has already studied the watershed and developed the watershed model for this area they will use it to assist the LWTB Team to develop design improvements in the northern portion of the watershed and to check compliance of the LWTB designs with dam safety requirements within Hempstead Lake State Park.