Some shellfish lease areas in Tomales Bay near the mouth of Walker Creek are facing shifting management rules from the California Department of Public Health because of water quality issues following very heavy rains, despite ranchers’ efforts to improve water quality in the watershed.

The Department of Public Health recommended tightening rainfall closure rules for one area leased by Hog Island Oyster Company because of high fecal coliform levels. Now, the company will have to wait longer before it can harvest shellfish following substantial rains that bring runoff into the bay. 

Another nearby shellfish lease closer to the mouth of Walker Creek, which has faced closures since late 2014, will be opened—good news for Hog Island, though under new rules the area can only be harvested during the dry season, according to an annual shellfish report released by the California Department of Public Health in August.

John Finger, who owns Hog Island with Terry Sawyer, expressed disappointment in the high coliform levels, given that ranches have worked with groups like the Marin Resource Conservation District to implement practices to curb runoff. Those projects can cost tens of thousands of dollars or more. 

“It’s not great,” he said of the high levels. “We’d hoped it would be going in the other direction.”

No one can say for sure why this is the case, though at a Lagunitas Creek Technical Advisory Committee meeting in July, Mr. Sawyer theorized that the sand bar in the area becoming more pronounced could be a factor. Still, he wondered “why we are seeing trends continue to not improve” given the work of the R.C.D., of which he is a board member.

Nancy Scolari, the R.C.D.’s executive director, said in the past five years the district has completed 11 projects in the Walker Creek watershed, and by this time next year another three will be finished. She said those numbers don’t include projects that the National Resources Conservation Service, a branch of the United States Department of Agriculture, has undertaken in the watershed. The R.C.D. also helps ranches and dairies in the area with water quality plans.

The health department’s new report says that heavy rainfall in particular has a deleterious effect on water quality in the area near Walker Creek, more so than other regions of the bay. 

In late 2014, the health department closed off an area of harvest near Walker Creek. At the time, Mr. Sawyer told the Light it was a small portion of acreage, but still, the farm harvested roughly six million clams annually from it. 

Although the health department allowed the oyster farm some harvest from the area in the dry season in 2015, it has been closed off since last October.  

Hog Island has conducted extensive testing and set up new testing stations near the creek since 2014, efforts that take time and money. In areas that were deemed inaccessible to harvest, the business collected over 200 water samples between December 2014 and June 2016, according to Vanessa Zubkousky-White, an environmental scientist with the health department. 

In fact, many years ago the area operated under seasonal closure, but that ceased in 2012 because of a lack of monitoring manpower from the California Department of Fish and Wildlife, a requirement for such management rules. 

Now there is a new memorandum of understanding in place with Fish and Wildlife so the area can be harvested, Mr. Finger said.

In addition to the formerly closed off area, the report also singles out a portion of the bay just to the east of this region, a different management region, that is also suffering from the impacts of heavy rain. One testing station in the area was almost out of compliance with water quality standards in the past year, the report said. 

Typically, rainfall means that growers stop harvesting for four to six days after the rain ends, though sometimes if rains are significant—over 2 inches—a closure will last an extra day. Now this area will be closed for an extra five days on top of the normal closures, meaning that a heavy rain could stop harvest for 12 days after a storm. 

He said the water quality issues and new rainfall closure rules would have a moderate impact on the business financially, “mainly because we have other leases in the bay.  If not, the impact would be huge.”

Yet perhaps one of the greatest concerns is that heavy rains could be part of the new normal of climate change. “This could be the pattern of climate change,” Mr. Finger said. “We could be seeing bigger events. Which isn’t good for a lot of things, including us.”