25I - AGMT - OCWD ASSESSMENT - Laserfiche WebLink

Home Browse Search

CITY OF SANTA ANA Well No, 32 Nitrate Mitigation and Rehabilitation Study • Residential area but no residences front street • Decorative brick cross -walks at Westwood intersection • Concrete intersection at Flower Intersection Westwood: Two travel lanes, one in each direction • Overhead utilities Provisions for maintaining access to a church and a public park need to be provided Summarized below are the design issues that will need to be considered for utilizing the Memory Lane Pressure Reducing Facility as a blending site: 1. The pressure reducing facility will need to be reconstructed. The facility will need flow control capability in order to deliver the water required to blend the water. The flow at the Pressure Reducing Facility should be a set flow rate. 2. Well pump horsepower of 150 hp with a design flow rate of 1,400 gpm assuming 3,600 gpm of blending water is available from the higher zone. 3. Pressure surges will be created as the ground water discharge is diverted from waste to discharge to the distribution system. In order to mitigate pressure surges the following will need to be considered: Type of valve used for transitions valve: — A valve made to throttle such as a ball or plug type valve — Motor operated valve electric actuator with valve opening and closing speed control slow enough to minimize pressure spikes • A surge tank if the pressure fluctuations are so severe that throttling valves do not satisfactorily mitigate the fluctuations 4. The well pump will also need a flow meter and a variable frequency drive to control flow. The well pump will need to be able to vary should the pressure of the upper zone begin to decline and the pressure sustaining feature of the pressure reducing valves begin to engage to prevent lowering of the pressure in the upper zone. 5. Provide an in -line static mixer to agitate and mix the two water sources. 6. This option from a control standpoint is more complex as the following parameters have to be met: • Half the MCL for nitrate entering the system • Flow control of Well No. 32 and the PRS • Monitoring of nitrates after the static mixer, if half the MCL is not met, then the well will need to be shut down while the pressure reducing station remains live. The pressure reducing station will then have to operate as normal based on meeting demands rather than a flow control station The City will need to confirm that flow can be restricted at the flow control facility to ensure mixing and still meet system demands P:\P00599\0086\E nxering \05\ Well -32 -Nit rate- MitigationOmfl ReVoit \02teztdocx - lo- TETRA TECH 251 -28