Not only is the West Seattle reservoir going to be covered with a 1-foot-thick concrete lid planted with grass, the 68 million-gallon drinking reservoir in Highland Park is being reduced in size by half.

West Seattle reservoir is one of six reservoirs in the city being "buried." Work is underway on the lid for the Myrtle Street reservoir on 35th Avenue. Other reservoirs due for caps are Maple Leaf in the north end and Beacon on Beacon Hill. The lids will all have the same design.

Meanwhile the Roosevelt reservoir was decommissioned and perhaps the reservoir in Volunteer Park will be shut down too.

"It's a federal rule," said Tony Brown, a spokesman for the U.S. Environmental Protection Agency's regional office in Seattle. "The surface water treatment rule requires water reservoirs be covered."

The U.S. Environmental Protection Agency gave public water utilities throughout the country a choice. Either cover reservoirs or filter out flowing water to keep pathogens from getting into the rest of the drinking water supply. It's cheaper to install lids so most utilities in the United States are capping their reservoirs, said Bill Wells, water quality and treatment manager for Seattle Public Utilities.

Water systems that have installed lids on their reservoirs report better water quality, Wells said. With less sunlight penetrating the water, there's less algae in it to affect taste.

Design of the project is about complete and Seattle Public Utilities has applied for a building permit. The project is scheduled to go out to bid and start construction next spring and take about two years to complete.

The West Seattle reservoir was built in 1932 and is the largest in the city's system. Before then West Seattle received its water from, first a half dozen, and later nine wooden tanks on Charlestown Hill.

The West Seattle reservoir doesn't have to be so big anymore because Seattle's water supply is much bigger now.

Back when the West Seattle reservoir was constructed, the water system didn't include 11-billion-gallon Lake Youngs, nor the Tolt River, nor the many wells near Riverton Heights that feed into the Seattle water system today, Wells said. With all that additional water available now, the West Seattle reservoir's capacity will drop from 68 million gallons to 30 million gallons.

The new West Seattle reservoir is expected to cost about $30 million, Wells said.

Seattle Public Utilities reassessed its water-storage needs and decided to reduce its overall capacity by about a third, Wells said.

The Myrtle Street reservoir is being reduced from 7 million to 5 million gallons. Work on that project is scheduled to finish in January.

In urban places such as West Seattle, capping large reservoirs means new places to play. Seattle Public Utilities controls what happens below ground but it is working with Seattle Parks and Recreation to figure out how the public can best use the upcoming new surface.

The surface of the West Seattle reservoir takes up about 21 acres. When they halve the reservoir, that will leave roughly 10 acres of capped reservoir and about 11 acres of reclaimed public land.

No money has yet been appropriated to develop any recreational facilities on the new open space. For now, there is money only for grass.

Seattle Parks and Recreation cautions that the new turf on the lid won't support trees. Nor will it be able to handle intense sports such as soccer. More passive sports such as flying- disk golf would be welcome.

Among the interested parties is the Samoan Cricket League, which is interested in moving its cricket pitch away from Jefferson Park on Beacon Hill.

The reservoir is next to the Westcrest Park off-leash dog area. There's a gentle slope down from the reservoir with a fence separating it from the dog park. The fence along the dog park will remain in place but other sections of fence will be taken down.

Future public meetings are planned to gather ideas from people about what facilities to include atop the West Seattle reservoir site,

Tim St. Clair can be contacted at timstc@robinsonnews.com or 932-0300.