Town of Lake George – Caldwell Sewer District Pump Station Improvements

The Town of Lake George sanitary sewer system, known as the Caldwell Sewer District (CSD), consists of approximately 198 sanitary manholes, 40,000 feet of sewer collection mains, two pump stations, and 6,200 feet of force main.

The Lower Pump Station (LPS), located on Beach Road near Lake George, receives gravity flows of sanitary sewer collected from lower portions of the CSD. The LPS pumps up to the Upper Pump Station (UPS), located on Fort George Road, via a 12-inch force main. These flows are then combined at the UPS with gravity sanitary sewer flows collected in upper portions of the CSD and pumped from the UPS to the wastewater treatment plant via a 16-inch force main.

Each pump station has three dry-pit submersible pumps, each with a suction line into the wet well, discharging into a common header that leads into the force main outside the pump station. The LPS pumps are rated at 50 HP each, and the UPS pumps are rated at 70 HP each.

A continuous decrease in pump performance at both pump stations prompted a comprehensive evaluation of the existing conditions, capacities, and operation. Based on the findings from this evaluation, replacement of all six pumps was recommended. Other needed improvements included replacing faulty valves, sections of deteriorated pipe headers, sump pumps, and older variable frequency drives (VFD); installing flow meters and float alarms; and upgrading the SCADA system.

Additionally, the existing pump stations lacked a way to isolate the pump station and bypass flows around the pump stations in the event of an emergency or maintenance situation where the pumps are out of service. This capability is a requirement of the Ten State Standards and needed to be addressed.

At the Town’s direction, LaBella prepared a project scope to address the necessary improvements. Central to the design was the replacement of the existing pumps with new pumps capable of meeting or exceeding the existing pumping capacities. The new pumps were selected based on the following criteria: certified performance curves; durable construction materials, including hardened impellers; hazard classification (Class 1, Div 1); reliable track record; and the ability to fit into the layout of the existing pumps being replaced. A combination of funding for the project was received from NYSDEC’s Water Quality Improvement (WQIP) program and the Town.

The design was advanced to the 60% level and reviewed with the Town along with an estimated cost of construction. After the Town’s review and acceptance, 95% of the design was completed, reviewed, and approved by the Town, and subsequently submitted to the necessary regulatory agencies for approval. Upon receipt of comments from the regulatory agencies, contract documents were finalized, and the project was publicly bid.

Trinity Construction, Inc. was selected as the general contractor, and Stilsing Electric, Inc. was selected to perform the electrical work. LaBella performed construction administration and observation services during construction. The new pumps, bypasses, and other improvements resulted in a sanitary sewer system with improved service reliability, resiliency, and capacity.

The Town sees a high seasonal population influx (high flows) from Memorial Day through Labor Day. The Town requested that critical work be performed outside of the high flow period, and as a result, the contractor developed a schedule that would accommodate the Town’s requirement. The pumps were ordered early in the year, which meant they would be installed in the fall.

The bypass work involved extensive coordination with the Town, shutting down the force main as the bypasses were cut into the force main, along with continuous hauling of the incoming sewage up to the wastewater treatment plant. Trinity Construction commenced work on the bypasses prior to Memorial Day and preplanned the work so the shutdown was only one day at each pump station.

Another critical sequencing concern was related to the installation of the pumps. Since the pump stations needed to remain in service during construction, a replacement sequencing plan was developed by Trinity Construction in coordination with Stilsing Electric, the pump representative, town operators, and LaBella.

As each existing pump was removed, two other pumps remained in service. Once a new pump was installed, the pump was performance tested, commissioned, and placed in service before the next pump was removed. This sequencing plan was implemented successfully and resulted in no issues at the pump stations.