John Hines, the city's renewable energy utility manager, said the 1,880-square-foot facility will go through public review for final approval starting next month. If it's approved by the Aspen City Council, construction could begin as early as the spring.
It will probably be Christmas time before we know if it's a go, he said. We are hoping to have it commissioned next fall.
That will have been three years after the majority of Aspen residents voted for the facility and issued $5.5 million in bonds to pay for it.
There has been minimal opposition to the facility, but some people are concerned about a decreased flow in the nearby stream because water will be drained out of it to generate power.
Hines said the city will host a neighborhood meeting after Labor Day in which a hydrologist and an engineer will address water-flow concerns.
He added that neighbors are generally in favor of the facility but are watching the design of it closely.
They are in favor of the hydro facility, but they want it done right; I don't blame them, Hines said.
A new water line is being built to replace the old one, as well as to accommodate the new plant, which will generate renewable energy for the city and increase its supplies by 8 percent over its current level of about 75 percent.
The project would utilize existing water rights, head gates, and water storage of the original Castle Creek hydroelectric plant, which met all of Aspen's electric power needs from 1892 through 1958, when the plant was decommissioned.
When completed, the 1.05 mega-watt facility is expected to increase electric production by 5.5 million kilowatt hours annually.
City officials say that switching from primarily coal-fired energy purchases to hydroelectric power production would eliminate an estimated 5,167 tons of CO2 emissions representing a 0.6 percent community-wide reduction in carbon emissions based on the 2004 greenhouse gas emission inventory.
The facility's turbine and generator will be designed to convert the force of falling water into electric power. The water comes from the Thomas Reservoir, which is located at the top of Doolittle Drive and is the home of the water treatment facility.
The water will travel down a 42-inch pipe, supplying the hydro plant with approximately 52 cubic feet per second. There are nearly 4.9 million gallons of water sitting above some residential areas and the hospital. The pipe would allow the city to quickly evacuate the water should the walls of the reservoir ever be breached.
The electricity will be placed on the city's grid and taken up to the water treatment campus to power those facilities, and to potentially produce hydrogen for hydrogen fuel cells and hydrogen vehicles.
The City Council reviewed the feasibility study for the Castle Creek hydroelectric plan in April 2007 and approved a contract with Smart Mahoney Associates for project planning.
The system and building design for the proposed Castle Creek Energy Center was complete last fall. The bid for the turbine design and generator was awarded to Canyon Industries, Inc. of Deming, Wash., and is being built with a delivery date of spring 2010.
The city is in the process of designing the facility and the permit process with the Federal Energy Regulatory Commission.