ENMAN ENGINEERING
Since 1982

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Hydraulic Systems Case Studies

Alpine Effluent Pump - Killington

Alpine Effluent Pump, Killington Vermont with its mountainous terrain and world class ski slopes is composed geologically of shallow depths to bedrock and shallow high water tables, and these make for difficult times for large land based sanitary wastewater disposal systems. Killington Ski Area has operated for many years on two spray irrigation fields with a total sanitary capacity of 260,000 gpd.

As Killington's plans for the Village Center and the Killington Grand Hotel moved forward, the need for additional wastewater capacity became essential. And another large land based disposal system was out of the question. Capacity existed in the City of Rutland plant for the immediate need of 40,000 gpd and the eventual 600,000 gpd projection, but the Alpine Pipeline at Pico Ski Area was over 6 miles away by roadway. And special authorization was required to build a private pipeline within the State of Vermont highway making this solution nearly impossible, if not already cost prohibitive.

The proposed solution was to build a pipeline from the base of Killington Ski Area up Rams Head Mountain, around Little Pico Mountain and nearly over the summit of Pico Mountain and then down the Pike Ski Trail to the Pico Ski Area base lodge and to the Alpine Pipeline Company's sewer. The route at 13,000 feet long was less than half the distance of going over the roadway. However, over 1,800 vertical feet of elevation needed to be overcome pushing operating pressures to near 850 psi.

This would be perhaps the highest pressure wastewater pumping facility in the northeast, if not the country. However, two other problems needed to be resolved, the 740 psi at the entry into the Alpine Pipeline had to be reduced to 0 psi before being discharge into the gravity sewer and there could be no wired electric or telephone communications between the pump station and the pressure reduction station three miles away.

The pumping station houses two Floway® Vertical Turbine Pumps, with a spare location for a third pump, three General Dynamic variable speed frequency motor drivers, and a Consolidated DSI 6200 control panel. At the Pressure reduction station two parallel pressure (redundant) series of butterfly valves, a fixed plate orifice and a rock filled concrete stilling well reduce the pressure from 740 psi to 0 psi in a lineal distance of 30 feet. Conventional PVC or Ductile Iron piping could not withstand pressures of over 800 psi. Pipe specified was 0.625 wall epoxy coated (inside and out) with an epoxy joint, field assembled. At pressures less than 250 psi, the pipe material is Drisco Pipe HDPE, 255 wall thickness was specified.

Pipe was assembled in lengths of 200 to 500 feet and then dragged from a staging area to an open trench where the pipe was bedded and backfilled. To allow for air introduction at shutdown and startup, high capacity air release valves were installed.

While the system operates today at a capacity of around 30,000 gpd, 400 gpm discharge rate and dynamic pressures of 840 psi with peak spike pressures of near 900 psi, the system has the capacity to expand to 600,000 gpd, with three 800 gpm vertical turbine pumps with 400 HP variable frequency drive motors.

Enman Engineering, P.C. is proud to have worked with Killington Ski Area on their extensive water and wastewater systems