Lake Water Improvement Project Update
The Lake Mission Viejo Association Board of Directors is pleased to share this update to the State of the Lake series, featuring news on the progress of the Preliminary Design Report (PDR) for the Lake Water Improvement Project. This and earlier Lake Updates are available online at lakemissionviejo.org.
Project Goals
After a time of thorough study and evaluation, 2022 is bringing steady progress in the planning effort and the beginning of implementation of a long-term plan to improve the Lake’s current water clarity and chemistry balance. Backed by scientific research, the Lake Water Improvement Project’s goals are to reduce the Lake’s pH and natural accumulation of total dissolved solids (TDS, i.e., the lake’s salt content) to create an environment that is less friendly to the growth and bloom frequency of golden algae. Because there is no viable method for eradicating golden algae, the Association has focused on how best to control and manage the algae in a sustainable and fiscally responsible way. While golden algae poses no threat to humans and has no impact on swimming or water activities, the Board desires to restore recreational fishing and improve water clarity, which golden algae has diminished over the past eight years.
Technical goals for the Lake, covered in detail in previous updates, defined the potential “sweet spot” of Lake chemistry that would be best suited for gaining control over golden algae. The sweet spot has been identified as a pH of 7.0 and a TDS of between 1,000 and 1,250 parts per million (ppm). Currently, the Lake has a TDS of around 2,300 ppm and a pH of 8.3.
Water Models
Previous action taken by the Board has already pointed TDS numbers towards a long-term decline, but water chemistry computer models show that more significant action is needed to reach the sweet spot goals in a shorter timeframe.
The water models used to determine estimated TDS numbers over time are based on the current chemistry of the Lake, the average amount of water lost naturally through evaporation and seepage, and the composition of the water used to refill the Lake, either from the Advanced Purified Water (APW) plant or from rainfall. These models show while the Lake is on track for a slow but steady reduction of TDS, it would take over 10 years with current weather conditions to reach the upper limit of the desired “sweet spot” range. While it is good news that TDS numbers in the Lake are on track to decline, the Board understands that more than 10 years for a possible but not guaranteed resolution of the Lake’s fishery and ecosystem challenges is not ideal.
Preliminary Design Report
When the Board initiated the Lake Water Improvement Project, it sought to research viable options for accelerating the process of attaining the stated optimal goals for Lake water. Coming to the forefront of that research were ways to use the existing APW plant to provide even more of its highly treated water to the lake. Because APW is low in both TDS and pH, getting more of it into the lake can speed progress towards both the TDS and pH sweet spot goals. The initial plan and cost estimates for this project were shared in the previous update.
With further refinement and an additional review conducted by a third-party engineering firm, the Preliminary Design Report (PDR) for the Lake Water Improvement Project is nearly complete. This peer-reviewed PDR will provide the details of the project and the processes needed to move to construction. The PDR will also provide critical information on project cost, time and impact that will be used to guide the Board in their decision process.
Within the Lake Water Project as a whole, there are two major project components which may be treated as independent project phases with a collaborative goal.
Component 1: Lake Water Flushing and Treatment
Currently, the APW plant cannot draw water from the lake. This portion of the project would allow for lake flushing by establishing the infrastructure needed to bring water from the Lake to the plant, so it can be treated and returned to the lake with lower TDS and pH. This will require construction of a new system of pipes, pumps and valves, along with modifications to the APW plant itself, to allow for the new inbound water source. Flushing creates more room for the plant’s highly treated water to be added to the lake year-round, a significant improvement over its current operations. The APW plant does not operate during much of the low-evaporation winter months because there is not enough available capacity in the Lake for more water. When the APW plant can provide lake fill year-round, progress towards the plan’s goals will be accelerated.
Estimated Project cost: $850,000.
Component 2: Advanced Purified Water Plant Expansion
The second portion of the project would involve expanding the capacity of the existing APW plant. When done in combination with the flushing and treatment project, the expanded plant capacity will accelerate the timeline for reaching TDS and pH goals.
Estimated Project cost: $1.95 million.
The estimated cost for completing both projects is approximately $2.8 million.
Timeline Projections
Using the water models, it is possible to predict the timeline for reaching TDS goals, assuming average weather conditions. The number of years needed to reach the beginning sweet spot goal of 1,250 TDS in the Lake is expected to be:
Flushing and Treatment project only: 8 years
Flushing and Treatment project with APW Expansion: 4 years
Progress towards the pH goal is expected as the Lake’s TDS is reduced.
Will it Work?
Research data suggests, but does not guarantee, that reaching the sweet spot of water chemistry will reduce both the toxicity and the frequency of golden algae blooms. If golden algae can be subdued, the Lake may be able to re-establish the ecosystem necessary for a thriving fishery, bringing back recreational fishing activities.
The Board understands that the scientific research undertaken here and elsewhere establishes that there is a risk that this project may not have the intended impact on golden algae. It has therefore also been careful to consider other positive impacts of the project, including adding the capability of filtering the Lake’s water over time to address other types of water issues, and the potential for other uses for additional APW from the expanded plant when not needed for Lake fill. The Board’s process for approval of the project will include an analysis of these long-term benefits in the years beyond achieving the Lake Water Improvement Project goals for the Lake.
What Happens Next?
With the Preliminary Design Report peer review now complete and final revisions of the document underway, the Board will outline a plan and schedule for moving ahead with the project. When that plan is approved, the next steps will include the creation of engineering and design plans, coordination with Santa Margarita Water District and the invitation of construction bids.
The Lake Mission Viejo Board of Directors is eager to see this project through and is hopeful for the future of the Lake’s fishery and water clarity. Understanding this project will take time, the Board is pleased to be able to offer to its members now the many benefits of the Lake which are not impacted by golden algae, including swimming, sailing, boating, programs, events, concerts and the iconic scenic vistas and incredible sunsets that make Lake Mission Viejo a priceless asset to this community.
This update is a continuation of an ongoing series appearing in the LMVA Newsletter and online at https://lakemissionviejo.org/news_letter.php. For more information about Lake Mission Viejo, contact the Lake offices at [email protected] 949-770-1313.