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ON -CALL ENGINEEMING SERVICE$ ,A
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<br />Following the initial steps In the rehabilitation of the well, then there are additional preliminary
<br />well rehabilitation operations that could be performed in the well, However, final well
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<br />rehabilitation operations need to be determined following a more complete review of the newly-
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<br />generated data and Information from the above listed Initial approach tasks, Fallowing this, a set
<br />of Technical Specifications can be developed to provide the final well rehabilitation operations,
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<br />f These operations may and will likely include the following rehabilitation options;:"
<br />1, Installation of a full, stainless -steel w1re-wrapped well screen casing liner and a new
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<br />gravel pack,
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<br />2. Mechanical cleaning, including wire brushing and using the AlrBuretiog(V, Bore
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<br />BiastingO, or Sonar•Je* methods,
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<br />3. Dual swab airlifting and swabbing (La., mechanical development), including chemical
<br />treatment, using appropriate available solutions or acids determined necessary by earlier.ii
<br />findings (i.e., performing a video survey).
<br />4. Re -developing and re -testing the well with a temporary test pump to determine the new
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<br />post -rehabilitation specific capacity of the well (i,e„ to check for possible improvements
<br />in specific capacity)._f
<br />Based on the results of new testing of the well following liner installation, it may be necessary
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<br />for the City to install a now pump and motor. A memorandum will be prepared discussing the
<br />findings and conclusions regarding the new pumping rates and specific capacities in the well.
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<br />Important to the preparation of the Technical Specifications is to evaluate options for the
<br />discharge of fluids generated from the well, via the National Pollutant Discharge Elimination
<br />System (NPDES) permit, and to provide a program for having the Contractor treat the discharge
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<br />so that Contractor-oompllancewith the City's NPDES permit is achievedatthe well site, It will
<br />also be possible to have the Contractor obtain a discharge permit for the site. In this way, the
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<br />burden of the permitting, sampling, and reporting Is shifted from the City to the Contractor,
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<br />Well Modifications
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<br />The sample project has a well approximately 30 years old that pumps to an existing onsite
<br />reservoir, and has a maximum yield of 2,000 gpm and a 250 hp motor. Based on the summary
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<br />of the City's existing wells, none of the existing wells match these conditions, The only wells that
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<br />have a design capacity of 2,000 gpm that pump to a reservoir are Well No. 16 (pump,; to
<br />Walnut) and Well No, 18 (pumps to John Garthe). However, both of these wells have 150 hp
<br />motors,
<br />As noted above, the Installation of a stainless steel liner casing will impact the well flow capacity
<br />as well as the well's specific capacity. In addition, pumping directly into the distribution system
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<br />instead of adjacent reservoir will greatly impact the pump capacity as it will increase the design
<br />head required by additional 180 to 200 feet. If assume a reduced well production by the liner of
<br />80%, the pump will need to Imeot the following conditions; 1,600 gpm at 420 feet lift which would
<br />require a 250 hp motor. For the sample project, the City has stated the well has a 260 hp motor
<br />so the motor will not be required to be upsized. However, the pump will need to be changed due
<br />to the liner as well as the now well design conditions,
<br />The sample project did not mention where the existing sodium hypochlorite generation facilities
<br />are located (at'the well or at the reservoir). If the existing chlorination facilities treat the water at
<br />the reservoirs and not at well, a new chlorination facility will be required if the well pumps
<br />directly Into the distribution system. In addition, changing the well operation to pump directly to
<br />City of Santa Ana f 10» ...�....�.„».��^^ TETRA TECH
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