Lake Water Improvement Project Update
Since our last Lake Water Improvement Project update in March and the ongoing State of the Lake series in the June 2021 newsletter, the Lake Mission Viejo Association Board of Directors, Management and Water Project team have been moving forward towards defining the best way to achieve our goal of providing a premier recreational lake that our membership can enjoy – be it for swimming, sailing, fishing or simply enjoying a vista of sparkling blue water.
For the last seven years, the Association and its Water Project team – staff members and a scientific and engineering team working under the direction of the LMVA Board of Directors – have been seeking solutions to two challenges: The declining clarity of the lake’s water and the toxicity of golden algae blooms that plague our lake and many other lakes across the country and all over the world – with no known solution. These matters are complex and challenging, especially considering the volume of water requiring treatment is so large and the work must be done within the Association’s available fiscal resources.
The Water Project team is tasked with developing a plan that would, first, use the scientific knowledge we have gained to identify a “sweet spot” for lake water chemistry, and second, present financially feasible and responsible approaches that could be used to attain that sweet spot so the Association’s Members can enjoy the recreational and aesthetic benefits they expect of the lake.
With this research and study now wrapping up, the Board will consider the recommended approach as part of its 2022 budget discussions at its meeting on October 13, 2021.
Actions Already Taken
Efforts to reduce the lake’s pH and salinity (measured as Total Dissolved Solids, or TDS) began in 2017 with the replacement of Santa Margarita Water District’s potable (drinking) water for lake refill with highly refined Advanced Purified Water (APW) from a plant SMWD built for Lake refill. APW is produced by running recycled water through several additional filtering systems, until its pH and TDS level drops to levels approaching the purity of rainwater. Initially, we were adding about 200 acre-feet of APW a year to the lake, which had an immediate but small positive effect on TDS levels.
TDS dropped further with the elimination of the use of well water for lake refill, which required the purchase of an additional 200 acre-feet a year of APW. Well water is much less expensive than APW, but is considerably higher in pH and TDS than APW. This change has already proved beneficial, with TDS numbers now on a long-term decline. After achieving our water chemistry goals for the lake, we may be able to use well water again in order to reduce the Association’s lake water refill expenses.
With 400 acre-feet per year of APW currently going into the lake, the plant is running near its maximum capacity, and its low-TDS water has dropped the lake’s TDS level from nearly 2,400 ppm to approximately 2,200 ppm.
The “Sweet Spot”
While conditions are improving, the current pace of improvement does not meet the Board’s desired timeframe for the project, so the Board’s scientific and engineering team got to work. Dr. David Caron, Chief Science Officer for Aquatic EcoTechnologies, LLC and a professor in the Department of Marine Sciences at USC, is heading up the science team, building on research he started with the initial golden algae bloom in 2014. The Association’s long-time lake water resource consultant, Dave Roohk, is assisting Dr. Caron’s team. Roohk specializes in water resources planning and water recycling. Determining the cost and engineering feasibility of proposed treatment solutions fell to Douglas Brown of Brown Horse Engineering.
Through laboratory work and additional experiments conducted in isolated pools in the lake, the science team determined that what appears to be the most effective way to lower the toxicity of golden algae blooms – reducing the lake’s TDS and pH levels – may also improve the lake’s clarity. Clarity plunged following the devastation of the lake’s aquatic plant and plankton populations by golden algae, and the research indicates that changing the lake’s water chemistry may help to restore the lake’s earlier ecosystem, leading to improved water clarity.
These many years of research have led to the identification of the sweet spot for improving Lake Mission Viejo water conditions: a TDS level between 1,000 and 1,250 parts per million (ppm) and a pH level of 7.0. Currently, the lake water TDS is approximately 2,200 ppm and its pH is 8.3. Lake pH, although not as easily controlled as TDS, should drop as the lake’s salinity drops and as lower pH APW continues to be added to the Lake.
Preliminary Design Report
Now that the sweet spot has been identified, the challenge before the Board is to determine how to change the chemistry of 1.2 billion gallons of water in a satisfactory timeframe and within the Association’s budget. Finding the answer to those questions fell to Brown Horse Engineering, which was commissioned by the Board to develop a Preliminary Design Report that would explore various solutions.
It quickly became evident that a two-year goal would not be feasible. Reaching this goal would require more than doubling the size of the APW plant, and there is not enough land available at the site for that. Instead, Brown’s draft Preliminary Design Report recommends an option that would increase the APW plant’s capacity by 50 percent, which could be done on the land available. This would make it possible for the plant to produce enough water to allow salt-flushing to be added as a lake water chemistry improvement strategy. An analysis by Roohk showed that with the addition of 50 percent more APW and salt-flushing, in four years a TDS level of 1,250 is achievable, with a level of 1,000 attainable two years later, six years after the plant expansion.
The Preliminary Design Report, which was prepared in cooperation with SMWD, shows that a combination of more efficient filters and an increase in the number of reverse osmosis units will support the desired expanded output. The salt-flushing program also will require new pipes and pumps that will draw in lake water and carry it to the APW plant, which is located across Alicia Parkway from the lake, where it will be treated and returned to the lake.
The estimated cost of the project is $1.6 million. The APW plant is owned and operated by Santa Margarita Water District, but the Association would pay for the expansion. The original agreement for the construction and operation of the plant, formed between LMVA and SMWD in 2016, was funded through a combination of Association funds and financing via a low-interest loan from Santa Margarita Water District. With this expansion, the Board may consider a similar agreement with SMWD. Following the 2016 APW construction, SMWD reached an agreement for funding and financing for a portion of the plant with the City of Mission Viejo in consideration for the City’s water needs.
What’s Next
With the approval of the 2022 Annual Budget, the Board of Directors has taken the first steps needed to approve funding for the first phase of this project,
Even after all these years of study, the lake’s dynamics make it difficult to predict with certainty how golden algae will respond to what we do, or to know exactly how long it will take to achieve the desired improvements. We have learned that we cannot expect to eliminate golden algae blooms since no one has figured out how to do that, but it appears we can limit their toxicity, to the benefit of the lake’s ecosystem. Still, the Lake Water Improvement Plan will be based on the best science-based predictions of what will happen, and ongoing management and monitoring should result in clearer water and a healthier fish, plant and plankton ecosystem in Lake Mission Viejo.
The Association remains committed to doing what’s scientifically indicated and financially feasible to do to improve our Members’ enjoyment of Lake Mission Viejo, and to continuing to update you as we move forward. If you have any questions, please ask your Delegate or call General Manager Andrew Comeau at 949/770-1313 extension 201.
Also, please visit the Communication section on our website at lakemissionviejo.org to review this and other Lake updates as well as an electronic version of the Lake newsletter.