(Photo by Tom Barrett)

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.

pool2From 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.

pool1It 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.


Inflatable Dam

dsc09781-1An 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

Year [pdf]


Earlier results:

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




Monitor Location Jan Feb Mar Apr May Sep Oct Nov Dec
Upstream 17 170 110 220 900
Downstream 23 300 110 50 500 240 23 1600 110


Monitor Location June July August
Week1 Week2 Week3 Week4 Week5 Week1 Week2 Week3 Week4 Week1 Week2 Week3 Week4
Upstream 102 56 55 212 96 160 100 150 134 160 143 198 154
Downstream 105 78 105 171 75 185 198 114 178 148 243 190 223





Monitor Location Jan Feb Mar Apr May Sep Oct Nov Dec
Downstream 170 17 500 80 70 140 80


Monitor Location June July August
Week1 Week2 Week3 Week4 Week1 Week2 Week3 Week4 Week1 Week2 Week3 Week4 Week5
Upstream 275 356 152 203 245 223 231 215 100 330 120 112 112
Downstream 542 343 230 120 354 239 224 240 192 330 132 128 177