Conjunctive use is being touted by the city’s advisory committee as the last great hope for Santa Cruz’s water supply. But will it work, and at what cost?
Somewhere between the rolling foothills of Soquel and the famous surf spots along East Cliff Drive lies what might be Santa Cruz County’s biggest reservoir. It isn’t as awe-inspiring as Loch Lomond, which reflects towering evergreens of the San Lorenzo Valley, nor as well understood.
The Purisima Aquifer, which stretches from Seabright to Corralitos, has the capacity to store a few billion gallons, according to latest estimates, all of it lying beneath the streets of Mid-County.
But this groundwater basin has been depleted faster than it could be replenished by rainfall. A lesson in the dangers of over-pumping, the aquifer is Soquel Creek Water District’s only source of potable water, and the threat of drinking-water contamination looms as seawater intrusion creeps slowly in from the shores around Pleasure Point. Once a well has been contaminated, it’s basically ruined.
The aquifer has also become a symbol of hope, however, for water activists from groups like Desal Alternatives. They’re enthusiastic about plans to pump winter water from nearby rivers, like the San Lorenzo, and store it underground in this “virtual reservoir,” as it’s been called, so that it can be pumped back out for use in droughts and dry summers.
The roots of this idea, known in policy circles as “conjunctive use,” stretch back more than three decades. Over that time, politicians and residents have watched the excess river water flow out to the ocean each winter through the city of Santa Cruz without getting stored, as the massive underground basin dwindles just a couple of miles south. Now, in the midst of a crippling drought, many believe they can both be part of one big solution.
When the city of Santa Cruz put plans for a controversial regional desalination plant with the Soquel Creek Water District on hold, it created the Water Supply Advisory Committee (WSAC) to further investigate ideas like this one. Now conjunctive use is a core part of the WSAC’s recommendations to the City Council. They’re proposing to take the water that would be stored in the Purisima Aquifer and inject it into the ground around Soquel or Capitola—a process called aquifer storage and recharge (ASR). The numbers have fluctuated over the years, but the latest estimates project that Santa Cruz might be able to store 500 million gallons a year this way.
The Cost of Dewing Business
Rick Longinotti, the leader of Desal Alternatives and one of 14 members on the committee, says he’s excited about the possibilities of this new approach, and relatively confident it will solve the city’s water shortage problems—even eliminating some of Soquel Creek Water District’s issues, too.
Sarah Mansergh, who represented the Surfrider Foundation on the WSAC, cites several reasons why she considers the option top-tier, including the possibility of it reducing saltwater intrusion, its significance as a regional solution, and its seemingly clear path to political acceptance. “The beauty of this aquifer approach is that it offers a lot more value in the end, and provides the scalability where we can deal with the uncertainty of the future,” she says.
Conjunctive use sounds simple enough, but there are a few unknowns in the process, and some experts have reservations about a plan that, with most recent estimates hovering around $159 million, could easily end up costing more than desal, which was lampooned as an overly expensive boondoggle by many of the same activists who now support conjunctive use.
Longinotti insists that some of the upgrades being attached to the cost of conjunctive use aren’t essential, and that the plan may end up costing closer to $70 million. “Those numbers have been jumping around a lot,” he says.
Others aren’t so sure.
“Great. Show me. If it only costs half, I’m 100 percent in,” says Mark Mesiti-Miller, who also served on the WSAC. “I’m an engineer, and I know that whenever engineers put together cost estimates they’re always higher. It’s impossible to project what the cost of this is going to be.”
“ASR is not as simple as storing water in a bathtub.”
That is how a team of water consultants qualified underground water storage in a memo about recharge projects around the nation, successful and otherwise, to the committee this past summer.
“Some projects have been successful at meeting anticipated goals,” the consultants wrote, “whereas others prove marginal or wholly unsuccessful at different stages in the planning process, and even after implementation.”
The WSAC has presented a three-pronged set of recommendations, including ASR, to ensure reliability and a variety of options. The City Council will take action on their recommendations next month.
The first piece is increased conservation, which will save 200 million to 250 million gallons a year by 2035 on top of what the city is already rolling out. That’s more than just puddle water, but still less than a quarter of the projected shortfall in a worst-case scenario drought year of 1.2 to 1.4 billion gallons. The estimate takes into account the uncertainties posed by global warming and the changes coming down the pipe requiring the city to take less water from its rivers and streams to protect endangered salmon.
The second piece is ASR and what the committee is calling “in-lieu recharge,” a plan to pump excess winter flows, sharing them with nearby districts’ customers. In theory, Santa Cruz would be able to reclaim some of this water if needed.
The city will be trying out a small-scale version of this plan as early as this winter. The city water director has worked out an agreement with Soquel Creek Water District’s interim director to send excess flows from North Coast streams to the neighboring district.
The final prong of the strategy is further consideration of recycled wastewater, with desal as a backup.
State health officials are currently studying the feasibility and safety of recycled water for potable use. With the drought as an imperative, many experts expect them to OK a practice that’s commonplace in the Middle East and parts of Texas. Still, even cautious supporters of recycled water are worried about the “yuck” factor and how it will be received in Santa Cruz. Activists like Longinotti want it to only be used as a “last resort,” partly because of its higher energy cost.
That leaves conjunctive use and aquifer recharge front-and-center in discussions, but some questions about its feasibility remain. For instance, the city’s treated water could foul and undergo chemical reactions in the basins of either Scotts Valley or Soquel Creek water districts. The t
reated water could be rejected by the ground itself. There could also be roadblocks to drafting long-term agreements with neighboring districts for how much water the city would be able to get back and when. Huge portions of the injected water could seep deep into the aquifer and basically disappear, although proponents argue that isn’t a bad problem to have. In theory, if the water isn’t available to withdraw, that means it has leaked into nearby creeks or is preventing saltwater intrusion.
“In a way, those are all good reasons,” says Doug Engfer, a retired software developer who sat on the WSAC.
But the goal at the end of the day is to have a couple billion gallons stored away for use in droughts. And engineer Mesiti-Miller says that with so many unknowns, conjunctive use will be hard to bet on going forward. But if the community really wants to do this, he says, there are ways to make it happen.
“The only building material that matters is money. You can make anything,” says Mesiti-Miller. “We went to the moon. It cost us 10 years and I don’t know how many millions of dollars. You can make this groundwater solution work. How much are you willing to spend to do it?”
The estimates for its cost have jumped around, going as high as $200 million in June, according to some consultants.
Jan Bentley, the city’s former water production superintendent, agrees with Longinotti that even the more recent estimates around $159 million are probably high.
More than a third of the projected cost is for improvements to the Graham Hill Water Treatment Plant, which might require upgrades to increase its capacity up to 14 million gallons per day. As far as anyone knows for sure, the current capacity of the plant is about 10 million gallons a day—only enough to send one or two million gallons daily to Soquel or Scotts Valley after meeting Santa Cruz’s needs. (The plan calls for five million gallons per day to Soquel Creek Water District.)
A longtime supporter of Desal Alternatives, Bentley says the 10-million-gallon estimate is way too low and that 12 million gallons daily “would be a fairer, conservative number.”
Terry McKinney, the department’s current production superintendent, says that he too thinks “this water transfer thing is going to work,” and that the cost estimates sound to him like they’re on the high side.
“They might be overestimating some costs. If you tell everyone it’s going to cost $80 million, and it ends up costing $120 million, then there’s an argument,” he says. “If you tell them it’s going to cost $120 million, and it costs $80 million, you look good.”
Either way, the plant will likely need some upgrades to treat dirtier, more “turbid” river water. Normally, the city switches to reservoir water whenever turbidity is high. But under conjunctive use, water officials would harness that water so that it can be used and shared. Longinotti says that regional partners could share in costs for a solution to problems like this.
The process of the WSAC itself cost about $2 million, with most of the money going to outside consultants.
One thing Engfer, the software engineer, has learned this past year and a half on the committee is that water isn’t a cheap commodity—at least not when it comes to planning for the future.
“It was amusing. When we started out, Rosemary [Menard, the city’s water director] joked that all water projects are $100 million. And we kind of laughed about it,” Engfer says. “All water projects are kind of $100 million. I mean, it’s a lot of money. The good news is that these kinds of improvements generally have long, effective lives, so you can finance them and spread the cost over 20 or 30 years. And we spread the cost over all of our customer base, and it ends up being relatively affordable, certainly more affordable to deal with it now than it would be to wait another generation. And in this way, I think we are solving the problem for generations to come, which is good work from a societal perspective.”
From the Ground Up
Engfer, a longtime skeptic of desal, came into the first WSAC meeting over 18 months ago practically overflowing with big ideas.
“My favorite solution coming into the whole process was off-stream storage in the old played-out quarries,” Engfer says of proposals to use abandoned lime quarries as reservoirs. “It seemed a natural way to be able to take advantage and in essence remediate or approve some land that has been disturbed.”
Committee members looked at four or five quarries, and they soon learned they all had problems. For starters, limestone dissolves in water, so engineers would have to find some way to cover and seal the entire pits. Even after that, the quarries would not have been seismically sturdy enough to support the water’s weight.
But when it comes to fixing water shortfall of over a billion gallons, there will always be uncertainties, pros and cons.
It would be unfair, for instance, to characterize conjunctive use as the only proposal with question marks this early in the process. Recycled water has its unknowns, too, even aside from the pending decision of state health officials. At this point, no one can say where a treatment plant would go—for instance, whether or not it could fit into the current wastewater treatment facility on California Avenue and Bay Street, assuming that the current location has a big enough footprint to accommodate more operations, which may or may not be the case.
“There have been some discussions talking about ideas, but there’s not been anything I’m aware of that’s been concrete,” says Dan Seidel, the superintendent of wastewater collection, which is in the city’s public works department.
Under the WSAC’s recommendations, water department staff will work on a couple of different ideas at the same time. Staff can begin building pilot wells to test the feasibility of aquifer recharge, and meanwhile do preliminary studying on recycled water—the “plan B” option, as committee members call it. Experts should know more about each of these plans this time next year.
“There’s work to do that won’t cost a gazillion dollars, but will help get us in a better situation to really understand what those options are, and to evaluate how they would fit here,” says Menard.
The council might provide direction on the best way to prioritize the different options.
The WSAC’s document outlines a few triggers spread out over the next 10 years to indicate how long the city should pursue the aquifer recharge strategy before changing gears.
Some of the triggers have to do with how much customers would be paying per unit of water under the various plans. Others have to do with the amount of water production that the different options could provide and how quickly.
Metrics aside, there is still some subjectivity and wiggle room left in the WSAC’s report.
The question remains: Once Santa Cruzans have pinned their hopes on aquifer recharge and begun to investigate, how or when will we know if it’s time to switch over to a plan B, like recycled water?
“The performance measurement—the ‘threshold,’ it’s called—is enormous,” says Greg Pepping, who represented the Coastal Watershed Council on the WSAC. “Everybody agrees that at some point, we’re going to have to do a climate-independent option if something doesn’t work. What’s the ‘if?’ The rest of it wasn’t easy, but eventually it was clear. The ‘if’ part for the threshold, some people wanted to invest in those backup plans right now, robustly. Not really anybody wanted to put them first, but we had different approaches for when to do the climate-independent option. For sure, that could be a sticking point on the implementation of that threshold. But we’re optimistic that we’ve dialed that in. It’s a policy document. It’s a guiding document with enough detail to be usefu
l, but not too prescribed. We tried to really strike that balance.”
The WSAC process, although gratifying in the end, was no easy task. David Baskin, a retired attorney, says it was “like reading War and Peace every month.” Engfer compares it to a part-time job.
Pepping says he “knew it would be time-consuming,” but it was “more demanding” than he thought. “And honestly, it’s more satisfying than I thought,” he says.
At the end of the day, Pepping says the portfolio’s “solutions honor the values of Santa Cruz” with a mix of creative, environmental solutions, like aquifer recharge, with some pragmatic fallbacks, if needed.
These projects are bigger than the engineering plans, themselves. The city already has an intertie with Soquel Creek Water District, but it doesn’t have one with Scotts Valley. “Part of the conversation with Scotts Valley will be, ‘Are they serious enough about that that [Santa Cruz] should go ahead and build that infrastructure?” Menard says.
It’s too early to say what role, if any, Soquel Creek Water District would play in a conjunctive use strategy, and officials don’t care to elaborate a whole lot at this point.
“We’re interested in solving the problem, you know,” says Ron Duncan, interim water director for the Soquel Creek Water District. “We’re interested in the fact that seawater intrusion has occurred in 60 to 70 percent of the world’s communities that use groundwater.”
Soquel Creek Water District isn’t the only group stressing the aquifer beneath its feet.
The district pulls only 50 to 60 percent of the total water out of the Purisima basin each year. The rest of the water in the basin supplies Central Water District in Aptos, a couple of private pumpers, including Cabrillo College and Seascape Golf Club, and even the city of Santa Cruz. Still, because the aquifer is Soquel Creek’s only water source and because of its proximity to the ocean, the Mid-County district doesn’t want to find itself between a rock and a hard place.
At the same time, staff and board members alike are reluctant to commit to anything with the city after Santa Cruz pulled the plug two years ago on a desal plant that both districts would have shared. So, Soquel Creek Water District staff are looking into other options, including deep-water desal and a recycling plant of their own.
Soquel Creek Water District board president Bruce Daniels says they owe it to their customers to keep those options open.
“We cannot risk getting at another deal and letting that fail. We have to be careful so we can solve our water supply problems in relatively short order,” Daniels says. “That’s another thing about doing a deal with the city, it can’t be just a handshake agreement. It has to be firm.”