Juneau's water story

Water pressure, an underground reservoir and flooded mine tunnels

Posted: Friday, April 26, 2002

Lack of rain this spring hasn't made a dent in the water supplied to downtown Juneau by a giant underground river.

Downtown Juneau consumes 1.8 million to 2.2 million gallons of water a day. The wells in Last Chance Basin, just off Basin Road, tap into that underground river, and the water is pumped to town.

"About 80 million gallons of water moves through the aquifer every day," said Grant Ritter, Juneau's water operations and maintenance supervisor. "The basin is a big sieve, and a lot of the water you see coming down those hills doesn't end up in the creek. It's underground."

Ritter said Juneau as a whole consumes about 4 million to 5.5 million gallons of water a day. About half comes from the Gold Creek wells and half from Salmon Creek Reservoir.

"We coshare with AEL&P and DIPAC," Ritter said of Salmon Creek. "We grab some and treat it and pump it into water system. What we don't grab, DIPAC uses for raising fish."

Demand for water peaks in the summer when the city water system also supplies thousands of visitors aboard cruise ships.

"We might consume 7 million gallons a day in the summer - we saw that once or twice last year," Ritter said.

The ships are served by an underground reservoir carved inside Mount Roberts. Three million gallons are stored in an old tunnel once used to run ore from Last Chance Basin to the Alaska Juneau gold mine's mill above Thane Road.

"The train tracks are still in it," Ritter said.

Water is pumped from the basin wells into that flooded tunnel. The reservoir helps sustain pressure through one of two supply networks serving downtown Juneau and Thane Road. It's also a reserve in case a fire emergency creates a demand for water.

About 10 years ago the city removed the other reservoir that served downtown, which sat atop Eighth Street. Water is still pumped to the top of Eighth Street but it goes to a pressure-reducing vault.

"It's there so we don't blow out stuff at the harbor," Ritter said.

The harbor is at the bottom of the system - with the greatest amount of pressure behind it. Conversely, folks in the top of the Mendenhall Apartments, the lower reaches of Starr Hill and in the highlands area above Behrends Avenue have the least amount of pressure.

Pressure is set so if there's a minus-4 tide - such as the one this weekend, there will be 104 pounds of pressure at the downtown harbors. The average water pressure downtown is about 88 pounds per square inch.

The lowest water pressure in town is at the top of the Fourth Street stairs.

"We can't give them more pressure without blowing out the people down below," Ritter said.

A separate system pumps water to the upper reaches of Starr Hill.

Douglas and West Juneau are served by water from the Gold Creek wells running through a pipe under the Douglas Bridge. In case of an emergency demand in Douglas, a million gallons of water is stored in a reservoir tank behind Crow Hill. West Juneau has water storage above Blueberry Hill.



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