minutes

South Bay Irrigation District

AUGUST 16, 2004

The Board of Directors of South Bay Irrigation District held a regular meeting on Monday, August 16, 2004, at the Sweetwater Authority Administrative Office, 505 Garrett Avenue, Chula Vista, California. President Welsh called the meeting to order at 3:30 p.m.

· ROLL CALL

Directors Present: Alkire, Doud, Pocklington, Reynolds, and Welsh.

Directors Absent: None.

Others Present: General Manager Dennis Bostad, Operations Manager Mark Rogers, Legal Counsel Paula de Sousa, and Board Secretary Marisa Farpón. Sweetwater Authority staff Hank Gaus, Mary Ann Mann, Mark Molsberry, and George Silva. Also present was Sweetwater Authority Director Mitch Beauchamp.

· PLEDGE OF ALLEGIANCE TO THE FLAG

Director Doud conducted the pledge of allegiance to the flag.

· OPPORTUNITY FOR PUBLIC COMMENT (Government Code Section (54954.3)

There was no comment from the public.

· PRESIDENT'S PRESENTATION

ACTION AGENDA

1. PRESENTATION BY MARK HATCHER, CHEMIST, SWEETWATER AUTHORITY
Monitoring and Modeling of the Sweetwater Authority Distribution System to Assess Water Quality.

Operations Manager Rogers introduced Mark Hatcher, one of the chemists in the Water Quality Department of Sweetwater Authority. He said that Mark had come up with a rather novel way of testing for nitrification in the tanks, and that he had given a presentation at the AWWA National Conference in Orlando last May.

Mark Hatcher said he was very pleased to be able to present to the board the results of the nitrification study performed on the Sweetwater Authority Distribution System. He acknowledged the two consultants who did the bulk of the modeling associated with the project, Charlotte Smith and Walter Grayman, as well as other staff members of Sweetwater Authority.

He said that nitrification degrades water quality. The chlorine residual gets lowered to the point where there is no protection against bacteria or water-borne pathogens that may be in the water. During nitrification coliform bacteria, for which we are regulated by the state of California, can potentially regrow in the system.

The goal of this project was to perform a comprehensive assessment of nitrification factors in the Sweetwater Authority distribution system to solve specific water quality problems and come up with recommendations to prevent and control nitrification. Nitrification occurs when ammonia oxidizing bacteria convert ammonia to nitrite. During this scenario, heterotrophic bacteria counts increase, which provides opportunity for coliform regrowth. As nitrification proceeds, the chlorine residual decreases, the nitrite concentration increases, and the ammonia concentration drops as it is converted to nitrite. The causes of nitrification in distribution system tanks are caused potentially by poor mixing, high water age, or low chlorine residual. In distribution system water mains, the causes include low water demand, treated water blends, dead-end lines, and low chlorine residual.

The nitrification study tools include a comprehensive water quality data review. The team reviewed data from the past and focused on those areas in the distribution system and its tanks that had a history of nitrification in the past. They used tank Thermistor data to determine if there were layers of water in the distribution system tanks stratified by temperature. They performed chloramine decay studies because as chloramine decays it releases ammonia, which is food for the nitrifying bacteria. They used hydraulic modeling extensively focusing on tank mixing and water age especially. They found that there was a very high chloramine decay rate due to organic content in the water and the chemical feed practices.

They found that the water age in the pipe network in the distribution system was less than four days at most locations, and the highest water age occurs in the storage tanks areas, such as the McMillin, Starr, Wheeler, Lynwood, and Hillcrest.

They performed a tracer study to determine if the findings on the system water age were accurate and reflect reality. When they switched from Sweetwater Lake water to aqueduct water, they could follow the aqueduct water through the system by using UV-254, which is a surrogate measurement organic matter. The organic matter in the aqueduct is so much lower that they could see at any point in the distribution system whether the water they were looking at was primarily aqueduct water or still treated lake water that had started out in the system. No chemicals were added during this tracer study.

The tracer study was performed over a five-day period. They sampled from the existing total coliform rule sampling sites spread throughout the system. Tracer study results showed that monitored and modeled UV-254 results matched up very well. The sampling was done at the Bonita Mesa and Mesa Vista and Orange and Sweetwater locations.

In addition to distribution system water age, they also studied the storage tank water age, as there have been problems in the past with nitrification occurring in the distribution storage tanks. The study showed that approximately three days is the average water age throughout that year, except for a couple of spikes that probably correspond to lower demand times. This average water age is very good. The conclusion is that tank water age is not a contributing factor for the nitrification problems experienced at Sweetwater Authority distribution system.

In order to determine if the tanks were well mixed or whether thermal stratification was a problem, temperature probes were installed into the tanks. A data logger is hung from the hatch of the tank, which continuously logs the temperature at different depths in the tank. The results of the Wheeler Tank showed that the tank is well mixed because the difference between the probes that were placed at the bottom of the tank and the top of the tank is only 0.2 degrees Celcius. The same trend was found in the other distribution system tanks. The conclusion is that there is no problem with the tank design in the Sweetwater Authority distribution system.

They used the hydraulic modeling to solve a problem at 28th and Tidelands area where they were having difficulty keeping the chlorine residual up in the wintertime when nitrite problems occur. That area has much higher nitrite levels than the surrounding sampling points. They wanted to confirm what parts of the distribution system received treated water from which plants. Most of the water is from the Perdue Plan, but they also get water from the Reynolds Desalination Plant and the National City Wells. The 28th and Tidelands area is a mixed water area where free chlorinated water is mixing with chloraminated water from the other two treatment facilities. They think that the free chlorinated water is degrading the chlorine residual and as the chlorine residual drops, the protection against bacteria is lost enabling nitrifying bacteria to get a foothold and start the process.

The conclusions of the study are that UV-254 proved to be a valuable tool for distribution system tracer studies; the design and operation or cycling of the tanks provide good mixing; and the nitrification problems at 28th and Tidelands were caused primarily by mixing free chlorinated National City Well water with chloraminated water from the Perdue and the Reynolds plants.

The primary goals of the nitrification control plan should be to reduce free ammonia-N in the Perdue Plant effluent and to decrease the monochloramine decay rate. The main potential cause of the nitrification in the Sweetwater Authority system was the ammonia in the water leaving the Perdue plant. There is always a slight excess of ammonia when free chlorine is added to ammonia to form chloramines. The other source of ammonia is the decay of the monochloramine residual. Also, the primary disinfectant procedures should be modified to balance CT requirements with disinfection byproduct and nitrification control. The distribution system nitrification-monitoring plan should focus on areas of historic problems and trend data for earlier response. Also, the National City Wells should be converted from free chlorine disinfection to chloramines.

Historically, the chloramines are formed early in the treatment process with the flash mix and, at that point, there is still organic matter in the water. There is also organic matter than can react with the chloramines residual and decay it pretty rapidly. A benefit of chlorine dioxide is that chlorine can be added after coagulation, flocculation, and sedimentation. Basically the conclusion is that a more stable chloramines residual will be formed that will not decay as rapidly and will not liberate the free ammonia, which is food for nitrifying bacteria, into the system. Another benefit of chlorine dioxide is that having a small chloride residual in a distribution system seems to be very effective in providing nitrification. A couple or recommendations resulting from the study were to trend data as soon as possible and focus on areas of historic problems and convert the National City Wells from free chlorine disinfection to chloramination. When that process is completed, the nitrification issue at 28th and Tidelands should be eliminated.

Mr. Hatcher thanked all who worked on the project for doing a great job and expressed his appreciation for the support received from all different parts of the company.

2. ITEMS TO BE ADDED, WITHDRAWN OR REORDERED TO THE AGENDA
(Government Code Section 54956.5)

There were none.

3. APPROVAL OF MINUTES

Director Doud made a motion, seconded by Director Pocklington, that the Board approve the minutes of the regular meeting of July 19, 2004. The motion carried.

4. APPROVAL OF DEMANDS AND WARRANTS

Director Alkire made a motion, seconded by Director Doud, that warrant numbers 10144 through 10155 be approved. The motion carried.

5. APPROVAL OF FINAL BUDGET FOR FISCAL YEAR 2004-2005

Director Pocklington said that he was very pleased with the work done for the budget and he appreciated the support that Board Secretary Farpón and Finance Director Gaus are providing by working together.

Upon a motion made by Director Pocklington, seconded by Director Doud, the Governing Board moved to approve the Final Budget for Fiscal Year 2004-2005. The motion carried.

6. NEW BUSINESS

Special District Public Education Program developed by California Special Districts Association (CSDA) and Association of California Water Agencies (ACWA) - Request for contribution. Director Pocklington made a motion, seconded by Director Doud, that the Governing Board approve a $50 contribution and that this request be forwarded to the Sweetwater Authority Board for consideration. The motion carried.

7. REPORT OF TREASURER

Treasurer Avery was absent.

8. REPORT OF LAFCO SPECIAL DISTRICTS REGULAR MEMBER

Director Pocklington said that the major item discussed at the LAFCO meeting was the dissolution of the Tia Juana Valley County Water District, and that all eight commissioners had voted in favor of the dissolution. The recommendation was to designate the City of San Diego as successor agency to the Tia Juana Valley County Water District for the purpose of winding up the District's affairs. The District will be given 95 days to circulate protest petitions and gather signatures.

9. REPORT OF SAN DIEGO COUNTY WATER AUTHORITY REPRESENTATIVE

Director Pocklington commented that the CWA is reconsidering the issue of seawater desalination with Carlsbad and Poseidon. The 50 million-gallon-per day plant needs to be in full production by 2010, and if that is not accomplished, the CWA will end up having to build Pipeline 6 earlier than anticipated. He noted that the Carlsbad plant was going to be a 25 million-gallon-per-day plant, but a 50-million gallons per day plant would be most efficient. His understanding is that the cost for 25 million-gallons-per-day would be about $60 an acre-foot more. Given the current drought situation, he said, we better maximize seawater desalination or we will be in deep trouble.

10. DIRECTORS' COMMENTS

Director Reynolds congratulated Director Pocklington for his appointment to the MWD Board. He added that it has been over twenty years since Sweetwater has had a representative at MWD and he is sure that he will do Sweetwater a lot of good.

Director Alkire said that on the first two-hour shift yesterday at the Lemon Festival, there were four low-pressure complaints.
Director Welsh said that the Lemon Festival was a nice event and people seemed to be happy. She was impressed with the tour that took place last Friday. The person that she was most happy to see on the tour was Paul Lanspery from the CWA, as he was able to see just what Sweetwater Authority does. The aid to Councilman Rindone was also present, as well as Leslie Wolf Branscom, who writes for the Union Tribune. Ms. Branscom commented on what a treat it is to come to see something that Sweetwater/ South Bay does because she has covered situations at other water agencies and can see the difference. Director Welsh added that this is a press person who is able to see those differences and writes objectively.

11. CLOSED SESSION

There was none.

12. ADJOURNMENT

With no further business before the Board, President Welsh adjourned the meeting at 4:22 p.m., to the hour of 3:30 p.m., on September 20, 2004.