FULL PACKET_2018-06-19 (INCLUDES 25E EXHIBITS)

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ON -CALL ENGINEERING SERVICES M� Following the Initial slope In the rehabilitation of the well, then there are additional preliminary well rehabilitation operations that could be performed In the well, Howevot,fibal Wall rehabilitation oparAtloria need to N determined following a more complete. review of the newly - generated date and Information from the above listed Initial approach tasks. Following this, a Sol of Tochnioal Specifications can be developed to provide the final wall rehabilitation operations. Thessoperations may and.wIll likely Include the following rehabilitation options: 1. Installation of a full, staInlass-stoolw1re-wrapped well Screen easing liner and a new gravol' pack, 2. Mechanical cleaning, Including wire brushing and using the A1rBur6tIng9,.BOrG Slastinge, or Sonawet6 methods. I Pool Swab Alrfifting and swabbing (Let, mochonloal development), Including chemical treatment, using approprIateaVallablo solutions or Aolds determined nsoos.sary by earlier findings (i.e., performing a video survey). 4. Re�developing and to-lostinU the wall with a temporary lost pump to clotormIne the now p6st-rohabilitation specific Capacity of the well (Le., to Check for possible Improvements In specific !capacity). Based on the results of new tooting of the well. following liner Installation, it may be necessary for the City to Install a now pump and motor. A memorandum will be prepared discuSSM0 the findings and 6onclutions regarding the hewpUmping rates and specific capacities In the well. Important to the preparation of the Technical SpoolficationA Is to evaluate options for the: discharge of fluids generated from the wall, via the National Pollutant Discharge Elimination System (NPQES) permit, and to provide p program for having the Contractor treat the discharge so that Contractor-oompliance, With the City's NPDES permit is achieved at the well site, It will also be possible to have the Contractor obtain a discharge permit for the site. In this way, the burden of the permitting, sampling, and reporting Is shifted from the City to the Contractor, Well Modifications The sample project has a well approximately 30 years old that pumps to an existing onsito reservoir, and has a maximum yield of 2,000 gpm and a P50 hp motor, Based on the summary of the City's existing wells, none of the existing wells match these conditions. The only wells that have a design capacity of 2,000 gpm that pump to a reservoir are Well No. 16 (pumps to Walnut) and Wall No. 18 (Pump$ to John Oarthe). However, both of these wells have 160 hp motors. As noted above, the Installation of a stainless steel liner casing will Impact the well flow capacity as well as the well's specific capacity. In addition, pumping directly Into the distribution system instead of a4aoent reservoir will greatly impact the pump capacity as It will increase the design head required by additional 180 to 200 feet. If assume a reduced well production by the liner of 60%, thepurnp will need to meet the following conditions; 1,600 gpm at 420 feet lift which would require a 260 hp motor. For the sample project, the City has stated the well hat a 260 hp motor so the motor will not be required to be upolzed. However, the pump will need to be changed due to the liner as well as the now well design conditions, The sample project did not mention where the existing sodium hypochlorite generation facilities ate located (at'the well or at the reservoir). If the existing chlorination facilities treat the water at the reservoirs and not at the -well, a new chlorination facility will be required If the well pumps directly Into the distribution system, in addition, changing the well operation to pump directly to Cifyof8anteAnn .10- TETRA TECH 25E-1 75 0 P rif 01 G C) 01 0, �J