Serious Risks Are Created By The Council’s Proposed Sewage Treatment Plant - Coronado Eagle & Journal | Coronado News | Coronado Island News: Opinion

Serious Risks Are Created By The Council’s Proposed Sewage Treatment Plant

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Posted: Thursday, January 16, 2020 10:22 am

Coronado residents should understand that the City Council’s proposed golf course sewage treatment plant, although well intentioned, would create serious risks for them. The City Council has spent a considerable amount of money pursuing a project to pump 1 million gallons per day of raw sewage through buried pipes running from the City’s trans-bay sewage pumping station near the ferry landing, across the city along Tidelands Park, tunnel under Third and Fourth streets, then along the bike path at the bridge entrance, to a new sewage treatment plant to be constructed on the golf course near the Bay. The facility would separate and treat some of the liquid for irrigation use, and then return the rest of the sewage through a pipe back the same route.

The City Council sought to minimize public attention on this $30 million project, including it as a component of the “Golf Course Modernization Project.” But a review of the City’s “2018 Final Feasibility Study Report” makes it clear that the driving force behind the project is the sewage treatment facility, which is proposed to develop a supply of water reclaimed from sewage to be used for irrigation. The objective is commendable, but there are significant natural obstacles that are rather obvious with the project. The City is further attempting to avoid public scrutiny of these risks by refusing to conduct a full environmental review of the proposal, as required by California law.

Geologic Risks

One of the inexcusable failures of this project is that its planners failed to deal with their own conclusions. The Feasibility Study (p. 1-2) states: “Active earthquake faults cross the City. Soils are susceptible to liquefaction and a high water table.” Yet the Study dismisses this issue as a “Less than significant impact” requiring no listed mitigation measures other than complying with building codes.

The CA Division of Mines and Geology lists three separate geologic faults in Coronado, two of which would be crossed by the proposed location for the pipelines and the treatment facility. These faults are described as part of “a major strike-slip fault zone and a member of the San Andreas fault system.” The Scripps Institute of Oceanography conducted a multi-year exploration of this fault system, and concluded that the faults could produce an earthquake with a Magnitude of up to 7.3 to 7.4.

Greatly exacerbating that threat, as acknowledged by the Study, is that “The project site includes areas that may be prone to liquefaction because the SWRF and Turf Maintenance facilities would be constructed on the golf course that was built on dredged material fill.” (App. H) That is, when subjected to an earthquake, the fill material can lose its structural integrity, behaving as though it is liquid, and causing structures in it such as buried pipes, to rupture, and facilities on it, to fail.

When asked at the recent City public meeting how the Study accommodated these geologic risk forces in determining the feasibility and estimated cost of the project, the Council’s contractor conceded that they did not consider these factors. Yet the Study concludes that somehow some unidentified mitigation measures, not yet developed, will reduce the environmental impact to “less than significant.”

The catastrophic impacts of earthquakes in a filled land area on buried sewage and water pipes are well documented in California. Roughly half the pipe breaks in the 1906 San Francisco event occurred within the area of filled land near the water where liquefaction occurred. More recently, buried pipelines were subject to sloshing action due to liquefaction resulting in 69 breaks in water mains within the Marina District during the 1989 Loma Prieta earthquake. The 1971 San Fernando earthquake resulted in 1,400 breaks in various piping systems, where soil liquefaction caused water, gas and petroleum pipelines to fail. The published seismic engineering studies are consistent in their conclusions: to mitigate impacts when designing, do not run pipelines across faults, and particularly avoid creating pipes and sewage treatment facilities in filled land areas subject to liquefaction. Compliance with building codes will not prevent such pipes from breaking.

One can barely imagine the taxpayer financial risk from hundreds of thousands of gallons of raw sewage from the Cays, the Amphib Base, the Navy Coastal Campus, and the Village, all pouring from this facility and its pipelines onto the golf course or anywhere along the route through the city, if they were ruptured by a predictable seismic event. The City has done no engineering analysis to determine whether it is even possible to design sewage pipes and a treatment facility to withstand such substantial natural forces and if so, at what monumental cost.

Another significant siting factor completely ignored by the Feasibility Study is the vulnerability of the waste treatment plant and its piping to being flooded by sea level rise, particularly when in conjunction with high tides and storms. The June 2019 Port of San Diego Sea Level Rise (SLR) Vulnerability Assessment concluded that by 2050, the Coronado Golf Course, since it is located near sea level, is vulnerable to potential inundation and temporary coastal flooding from a major storm event. At 2.5 ft of projected sea level rise, large portions of the golf course are projected to be inundated especially during high tides and storms, including the proposed location of the sewage treatment facility (p. 116). If the facility operated beyond its 30 year projected life, the situation would become even more dire. By 2100, there is a 1 in 20 chance of sea level rising 4.5 ft, or above the likely elevation of the proposed site of the project. And that is before any consideration of impacts from high tides and storms. Climate Central states there is a 100% chance of at least one flooding event of 3 ft or more before 2050 and there is a 100% chance of at least one flooding of 6 ft. or more before 2100.

There is no consideration of these impacts on the proposed location of the project contained in the Study, simply that the geologic and hydrology considerations do not present any significant impacts that cannot be mitigated. They City simply ignores very real threats and wishes that the problems will go away. We the taxpayers of course will be the ones to pay for these mistakes in judgment if events occur, including cleanup from major ruptures of the sewage pipelines and the treatment facility.

Environmental

Compliance

At this point we may wonder why the City would vote to support a conclusion of less than significant impact for the categories of geology and hydrology, when the potential for extreme impacts are obvious. The answer is that the City is attempting to avoid having to prepare an Environmental Impact Report (EIR) as required by California law whenever a municipal project has a potential for significant impacts. A key requirement that must be addressed when an EIR is prepared is the consideration of alternatives to the proposed project in order to assess whether alternate options should be pursued, including the option of not proceeding at all.

Various alternatives that were not seriously pursued by the City and its contractor include: negotiating with the Port and Cal America to use the Tidelands Park for a reclamation facility (thereby avoiding crossing one or both faults, at a higher elevation, with no residential visual impacts); drilling an exploratory deep test well to the San Diego Formation under Coronado as recommended in its 2011 Feasibility Study for a potential desalination facility as San Diego is doing with its reclamation project; contracting with the City of San Diego for its excess reclaimed water; and re-attempting to partner with the Navy now that North Island has been identified as a facility facing water shortages. We simply do not know without investigation, whether any of these or any other alternatives might prove to be a much more prudent option for our city, and for us as taxpayers.

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