Sycamore Pool on July 4th, 2003
How is Sycamore Pool cleaned?
As with all dams, silt and gravel accumulate behind the dam at Sycamore Pool. Because the dam isn’t completely removed in the winter, a large accumulation of gravel builds up behind it. In late May, the pool area is prepared for summer swimming. The water is diverted under the pool and many, many truckloads of gravel (about 90 in 2003) are removed. This gravel is dumped in the Horseshoe Pit area.
From Memorial Day to Labor Day, every Thursday morning starting at 7 a.m., park maintenance workers drain the water from the pool, scrub the week’s accumulated mud and silt from the concrete pool bottom, and wash off the algae. Since the pool is in Big Chico Creek, you may wonder how this is accomplished.
The workers start by slowly opening gates to a large underground drain in the middle of the upstream (east) end of the pool. This diverts creek water into the drain and discharges downstream (west) below the dam. At the west end, the dam gate is raised slightly to slowly release the remaining pool water. Then the workers insert boards across the rest of the east end of the pool, creating another dam and forcing all the incoming creek water into the under-pool pipe. The dam gate is lowered again at this point.
It’s important to not stir up the silt on the bottom during this process because that would increase the turbidity of the water, decreasing the breathing capacity of downstream fish.
It takes about an hour to drain the pool. A loader with brushes on a bucket is driven in from the children’s pool to scrub the bottom of the pool. A pressure washer removes algae from the sides and about the first 3 feet of the bottom of the pool (to make it less slippery for people entering and exiting the water). All of this remaining water, silt, mud and algae is sucked out of the pool using a truck- mounted pump and a large diameter collapsible drain hose. This sludge is pumped to the same area as the gravel. It takes about 4 hours to clean the pool and another 2-3 (depending on the water flow rates) for the pool to refill. Swimmers are not allowed back in the pool until it’s full, which may be as late as 3 p.m.
An inflatable dam replaced the old wood and steel one during the summer of 2008. It can be raised and lowered using air pumps in a nearby control room, thus avoiding the labor-intensive and hazardous work that the old dam required when doing pool maintenance. It can be lowered during the winter to allow gravel to clear the pool and to minimize impacts on migrating fish.
The Polar Bear Swim
An informally organized Polar Bear Swim is an annual New Year’s Day event at the pool.
Fecal Coliform Monitoring at Sycamore Pool
Samples shown here are taken on Fridays on the north side of the pool. In the summer, samples are taken every day.
Parts per 100 milliliter