Although San Franciscans love to talk about our pristine tap water — siphoned directly from Yosemite National Park and into our increasingly expensive apartments — things could get a little murkier in the near future. And you probably won't even notice.

By 2016, San Francisco is expected to open four new wells on the Western side of the city, as well as convert two Golden Gate Park irrigation wells into wells for drinking water. All six of the wells will draw from an aquifer that runs from Golden Gate Park to San Mateo County. The problem with that is our groundwater is, well, not so good. The Examiner reports:

Thanks to leaks from sewer mains and runoff from fertilized parks, local groundwater contains levels of nitrate and coliform bacteria “that exceed U.S. Environmental Protection Agency’s drinking-water standards,” according to a review conducted by the U.S. Geological Survey in 1990.

Groundwater tests have shown nitrate levels of up to 55 milligrams per liter in wells near Lake Merced and Golden Gate Park, which is well above the 10 mg per liter cutoff where water is no longer considered safe to drink. But before the thought of Golden Gate Park runoff coming out of our taps sends you screaming for bottles of Fiji, remember we've still got that 100% pure Hetch Hetchy with which to cut it. For most customers, they probably won't be able to tell the good stuff from what's been cut with a cheaper product anyway. The Examiner continues:

Untreated and unblended, the local groundwater is “suitable for irrigation and other nonpotable uses,” but not for drinking, the USGS wrote.

However, when blended with Hetch Hetchy water — at about a 10 percent groundwater to 90 percent Hetch Hetchy ratio — the water meets national safety standards, according to Steven Ritchie, the SFPUC’s assistant general manager for water.

“This is perfectly safe water,” he recently told a Board of Supervisors committee, adding that in preliminary taste tests, most residents could not tell the difference.

While other Bay Area cities also use Hetch Hetchy water, albeit at a slightly different mix, those other cities also filter their water beforehand — something the SFPUC is not planning to do. They will, however, add a hint of chlorination, so at least we won't have to worry about Coliform.

Finally, the groundwater-Hetch Hetchy blend will mostly be heading to faucets and showerheads on the western side of the city, in case you needed another reason to talk yourself out of moving to the Avenues.

Previously: All Hetch Hetchy coverage on SFist