Underground Transmission Line

Dewatering System

H2M is currently providing Public Service Enterprise Group Long Island (PSEG LI) with groundwater sampling, dewatering design, permitting, and environmental monitoring for the construction of a new 5-mile, 33kV underground electric transmission circuit within the rights-of-way of the Far Rockaway peninsula in Queens, NY.

The new underground electric transmission circuit is intended to relieve contingency overload conditions on the existing transmission circuits currently serving the project area. A portion of the work is being completed within substations that must comply with New York State Department of Environmental Conservation (NYSDEC) approved Site Management Plans and associated Excavation Work Plans to ensure appropriate  management of remaining soil and groundwater contamination. The project is being completed within a dense urban landscape and 95% of the work is being completed within the New York City rights-of-way.

H2M’s goal was to design a dewatering system sufficient to provide a dry setting for the contractors to install underground cable and splice vaults and secure the appropriate permits from the City and State to discharge the water generated during construction into the New York City sewer system.

To understand the groundwater quality and aquifer parameters in the project area, H2M installed permanent groundwater monitoring wells and provided well sampling along the alignment for chemical quality and aquifer parameters. H2M also utilized Geographical Information System (GIS) data investigated to identify the locations of the underground utilities in the project area. Sampling and site reconnaissance were performed within busy rights-of-way and required appropriate maintenance and protection of traffic.

H2M designed a dewatering system for the entire alignment and provided PSEG LI with a construction dewatering drawing set with over 50 different points of discharge and more than 30 separate dewatering systems. A full-scale radius of influence determination was required for this permit, to demonstrate to the State that design parameters would not cause movement of groundwater from local spill and remediation sites. Due to the flow rates and quantity of water needed to discharge, approvals were also required from both the Bureau of Wastewater Treatment and the Bureau of Water & Sewer Operations, as well as the Metropolitan Transit Authority to ensure impact to the A Train line was minimized.

H2M is currently involved in the final phase of the project, providing environmental oversight and ensuring that all permit approval stipulations and dewatering plans are followed by the contractor.