Plastic may be discouraged at the grocery store these days, but it’s still sometimes used for sandbags by San Mateo County. Paper obviously won’t cut it as an alternative, but the San Mateo County Department of Public Works will be investigating other possibilities, said director Jim Porter.

The plastic bags currently in use were donated to the county for use as sandbags to help control erosion, weigh down hazard signs and to fulfill other requests.

“We take what we can, given the budget we have these days,” said Diana Shu, a senior civil engineer and road manager for the county.

Some of the sandbags used on the coast are labeled “selenium,” which can be toxic to humans and the environment. But Shu said the bags have been repurposed and now contain only clean sand.

Few materials have a tight enough mesh to hold such fine grains, according to Porter, and the old selenium bags seemed like a reasonable bet.

But Lisa Ketcham, the secretary of the Midcoast Community Council, has observed that the plastic bags degrade in the sunlight and flake, blowing into sensitive watersheds like the Fitzgerald Marine Reserve. Flaky sandbags have also been spotted on Ocean Boulevard and at the Sunshine Valley watershed outlet in Moss Beach, and they tend not to go away.

“It’s still the same stuff, but it’s broken into smaller pieces, like a slurry,” Ketcham said. When a marine animal consumes it, she said “it’s like eating a plastic bag.”

Most disconcerting is that plastic contains toxins that affect humans, she added, and that the plastic could collect in a colossal gyre of garbage in the ocean known as the “Great Pacific Garbage Patch.”

There, debris, including plastic, gets caught in the currents — sometimes for years — and is difficult to clean up.

Porter said that the only alternative may be burlap, which is a cloth material that breaks down within three months.

“What happens is your (burlap) sandbags turn into sand,” Porter said. He said his roads crews were considering other potential materials this week.

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