Due to increased development in the Anchorage, Alaska, area, the existing Municipal Light & Power (ML&P) plant initiated an expansion in order to meet the additional demand for electrical energy. Because of prolonged cold winters, the expansion required the storm water management systems be placed underground.
Engineering design firm Stantec originally specified concrete vaults due to the climate constraints. Because of the cost of the concrete vaults, ML&P wanted to look at less expensive alternatives. The onsite contracting company, Roger Hickel Contracting, suggested installing an underground plastic storm water chamber system. Although such a system would be significantly less expensive, ML&P feared plastic chambers could become brittle and crack with a mean low winter temperature of 0°F to 5°F and a frost line that was typically 4 to 6 ft deep, occasionally reaching 10 ft deep.
The problem was solved with the selection of two StormChamber systems. They were less expensive than the concrete vaults and were suited to the harsh climatic conditions because they were made from high-molecular-weight polyethylene (HMWPE). Storm water chambers made from HMWPE are less susceptible to cracking in low-temperature environments. The systems also were selected due to their performance under these conditions in single and stacked configurations in northern states with cold winters and many parts of Canada, including the Yukon Territory.