Sycamore Pool Operations

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.

Sycamore pool gets a weekly cleaning

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.

To drain the pool, the creek is diverted into an undergound channel.

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.

Summer and Winter Dams at Sycamore Pool

The pool has a "summer" dam that's in use three months of the year. The rest of the year, the "winter" dam of about 4 feet is in place. You might ask why the Park Dept. doesn't just totally remove the dam at the end of summer. Here's the answer:

When this area of the creek was widened in 1923-24 to create the swimming pool, one result was that the water just upstream of the newly created dam area spread out to create a shallow streambed, instead of the deep, but narrow streambed that exists upstream from the pool and below the dam. Before the winter rains start, without a dam to raise the water level in Sycamore Pool, the water in the pool area would be so dispersed and shallow that fish couldn't swim upstream past the point of the fish ladder. As an aside, when you see those intrepid swimmers plunging into Sycamore Pool on New Year's Day, remember that the flow rate of the water at that time of year can be more than 100 cubic feet per second so not only are they battling the cold water but also a very strong current.

Inflatable Dam

An inflatable dam has been proposed to replace the existing dam at One Mile. It would offer several benefits. First, because it could be collapsed totally during major winter storms, gravel would be able to flow past the dam, producing the gravel recruitment that's necessary for a healthy creek downstream. Winter tree debris wouldn't catch on the dam as happens now. It would be safer for park workers to operate and would also speed up the weekly cleaning process. The Park Department applied for a CalFed grant several times for this project, but was not successful. They now plan to use $240,000 of Proposition 40 money and apply for a matching-fund CalFed grant for the rest.

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

2002

2003