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The Del Puerto Water District entirely ignored threats to wildlife and Del Puerto Creek that would be caused by their proposed project.

Over the holidays, the Del Puerto Water District quietly released environmental reports for a massive, ridiculous reservoir that would flood the first five miles of Stanislaus County’s Del Puerto Canyon, one of the most biologically rich landscapes in the Diablo Range.

After a site visit to the downstream portions of Del Puerto Creek, Shawn Smallwood, Save Mount Diablo’s contracted wildlife biologist, found the reports

• dramatically underestimated wildlife presence,
• ignored cascading ecological damage, and
• failed to explain how a living creek corridor could survive with just a fraction of its water flowing because of project impacts.

Dozens of species including rare and imperiled wildlife and actively nesting raptors were documented during our survey where the district report suggested little concern or ignored the facts entirely.

On a larger scale, the project as a whole would inundate Native American cultural resources; completely alter Del Puerto Creek; and destroy critical habitat for species like mountain lions, tule elk, and golden eagles.

The Diablo Range, including Del Puerto Canyon, has the largest population of nesting golden eagles in the world.

The project costs have also skyrocketed from $400–$500 million in 2019 to $1.2 billion today, not even accounting for what will be an overly expensive road relocation project.

All this combined with no meaningful biological mitigation has resulted in a project with disastrous implications for the public and the environment.

The public had little notice and little time to respond, given the holidays. The state report, a partially recirculated draft environmental impact report (PRDEIR, or the “draft EIR”), allowed just 45 days for comment, from December 15 to January 30.

A second federally required draft environmental impact statement (EIS) allowed only 30 days, from December 12 to January 12.

The timing of the release for the two draft reviews in the middle of the holidays was a clear attempt to avoid pushback and limit any public input.

Del Puerto Water District’s Absurd Environmental Review

With an extremely short timeline, Save Mount Diablo made brief comments on the EIS—expecting little attention from the strapped federal agencies, and concentrated more on the draft EIR, because California’s environmental laws are more likely to be effective.

The new draft EIR incorporates information from the 2019 draft and 2020 final EIRs and was modified to supposedly evaluate potential impacts on terrestrial species in the downstream portions of Del Puerto Creek.

The water district made little attempt to follow the law, however.

The new draft EIR comes after a lawsuit from the Sierra Club and other organizations argued that the original final EIR from 2020 insufficiently analyzed the project’s environmental impacts.

An appeals court ruling agreed, saying Del Puerto Water District failed to analyze the project’s potential impacts to terrestrial species living in or around Del Puerto Creek downstream of the proposed reservoir.

The water district claimed in the draft EIR that no project impacts would be significant to downstream terrestrial biological resources and therefore no mitigation is required. This evaluation was ridiculous and entirely false.

Field Visit Exposes the False Claims Stated in the Environmental Review

Save Mount Diablo contracted an expert biologist, Dr. Shawn Smallwood, to conduct an in-person analysis of the downstream locations of Del Puerto Creek.

The findings were staggering.

Dr. Smallwood detected 60 different vertebrate species, 13 of which he determined were  “special status” species. These included species such as northern harrier, Nuttall’s woodpecker, and double-crested cormorant.

The water district’s draft EIR makes only brief references to American beaver, American bullfrog, Botta’s pocket gopher, and California ground squirrel but does not mention whether any other species were observed.

In contrast to those four species noted in the draft EIR, Dr. Smallwood detected 15 times as many species in just a small portion of the study area in less than 4.5 hours.

The draft EIR also relied heavily on online wildlife databases like the California Natural Diversity Database, eBird, and iNaturalist to decide which species could occur in the downstream site.

But these online tools only confirm when a species has been seen somewhere, they cannot prove a species isn’t there.

Many rare or imperiled species are underreported simply because nobody has looked carefully, or because those species only recently received protection under federal or state law. Absence of data does not mean absence of wildlife.

Using those databases and his own field work, Dr. Smallwood identified 132 special status species near the project area that should have been analyzed.

These wildlife included species like California tiger salamander, northwestern pond turtle, and western spadefoot.

The draft EIR evaluated just 22 (barely 17 percent of the species) and screened out 110 species from review, even though half have been documented within 1.5 miles of the site.

The report claimed the white-tailed kite was only moderately likely to occur. Dr. Smallwood observed a mating pair during a single visit.

Dr. Smallwood said, “At least a year’s worth of surveys would be needed to more accurately report the number of vertebrate species that occur at the project site.”

He predicted that with more time, 213 species of vertebrate wildlife, including 46 special status species, could be identified. He noted that the downstream portions of Del Puerto Creek are “a relatively species-rich wildlife community that warrants a serious survey effort.”

The district’s contracted biologist only conducted one survey in July 2025. Surveys are required to be much more extensive and occur over several years, while a mid-summer survey is one of the worst times to do biological review.

From their one, ridiculous site visit, the district’s draft EIR failed to provide any clear details about how their own biological survey was conducted and which species were observed.

The conclusions listed in their draft EIR about impacts simply can’t be trusted because of this.

Expert Analysis Shows Creek Hydrology Would Completely Change

Just as troubling, the draft EIR admits the reservoir will dramatically change Del Puerto Creek’s flows, altering water volume, timing, temperature, sediment, and oxygen, but never explains what that means for wildlife living along the creek.

Those changes will affect plants, insects, and fish, which in turn support bats, birds, and mammals. Ignoring that chain reaction leaves out major ecological consequences.

The district even tried to argue the project would mimic existing conditions of creek flows. Its own earlier data says otherwise: annual flow in lower Del Puerto Creek would drop by about 81 percent, with winter months seeing reductions of roughly 70 to 86 percent.

Less water means shrinking riparian forest, fewer cottonwoods, reduced habitat, and lower food availability for species that depend on the creek corridor.

Riparian habitat is some of the most valuable and most endangered habitat in California, and in an area surrounded by intensive agriculture, this creek is a lifeline for wildlife movement and survival.

What remains in lower Del Puerto Canyon is irreplaceable.

Yet the environmental report never analyzes how drastically reducing the creek flow would impact the animals that rely on it, leaving the public without a clear picture of the damage the reservoir would cause.

The Original Environmental Review Was Incomplete in the First Place

Del Puerto Water District certified their original final environmental impact report in 2020, correctly stating that the project would cause significant impacts to biological resources. However, they inaccurately claim that these impacts could be less than significant with their completely unmeaningful mitigation measures.

The final EIR include sections for rare and endangered species like San Joaquin kit fox, American badger, and western pond turtle.

The reports analyzed the project impacts on riparian vegetation and state or federally protected wetlands, as well as wildlife corridors in the Diablo Range.

Some mitigation measures were proposed to compensate for the loss of habitat or disruptions to species.

For example, the final EIR proposed compensation for loss of California tiger salamander habitat, California red-legged frog habitat, and foothill yellow-legged frog habitat.

It also required avoidance and minimization measures for burrowing owl and nesting birds during activities like construction.

Compensation for impacts on riparian habitat and protected wetlands was likewise required. Most habitat compensation was determined to only require a 1:1 ratio, meaning for each acre destroyed, an acre would be protected elsewhere.

Not only does this absurd mitigation ratio fall short of compensating for the destruction of one of the most biodiverse areas of the Diablo Range, but also, the district claimed it would reduce most biological impacts to “less than significant after mitigation.”

That conclusion depends entirely on the assumption that the biological baseline was accurate in the first place.

The Fifth District Court of Appeals ruled that the final EIR failed to analyze impacts to downstream terrestrial species. In other words, even before the current partially recirculated draft EIR, the biological review had an obvious blind spot.

With our new field surveys showing dozens of additional species present and over 100 special status species that should have been evaluated, the original biological analysis likely underestimated both species’ presence and habitat function throughout all of the project footprint.

If the wildlife community was undercounted or the surveys conducted were insufficient, then the mitigation ratios and “less-than-significant” findings rest on shaky ground.

Compensation acreage does not replace a functioning canyon ecosystem and buying land elsewhere does not re-create one of the most intact wildlife corridors in the Diablo Range.

Mitigation only works if you know what you’re mitigating.

Save Mount Diablo Submits Comments Challenging False Claims

Our organization submitted comment letters with our expert analysis of terrestrial wildlife impacts in downstream portions of Del Puerto Creek, but we also built on the administrative record by commenting on the project as a whole.

California condors have been seen roosting near the canyon, something not discussed at all in the 2020 final EIR. Native American burial grounds and cultural resources would be inundated— also downplayed by the district.

The district’s lack of any meaningful proposal for mitigation of the project impacts, especially biological ones, was also a focal point of our letter.

Save Mount Diablo submitted our comment letters and signed on to similar comment letters submitted by Friends of the River, another nonprofit deeply involved in the Del Puerto fight, along with the local grassroots group, Save Del Puerto Canyon.

What Comes Next?

Now that the comment period is closed, the water district must respond to every substantive comment and decide whether to revise the environmental report.

They can change the project, add mitigation, or move toward certifying the environmental impact report and approving the reservoir. If the analysis still fails to disclose or address the project’s impacts, that decision can be challenged in court.

A long list of environmental regulators will also have a say, such as the California Department of Fish and Wildlife, whose new Director, Meghan Hertel, was recently California Natural Resources Agency’s Deputy Secretary of Biodiversity and Habitat.

Her efforts to conserve biodiversity and improve habitat across the state through the implementation of California’s 30×30 strategy and associated efforts will be a focus point for the Del Puerto effort.

Given that the water district is ignoring biological impacts, we hope the California Department of Fish and Wildlife will demand much better environmental review and mitigations.

Save Mount Diablo will closely review the district’s responses and continue advocating for Del Puerto Canyon’s protection against this terrible reservoir proposal.