1CDM Smith, 6000 Uptown Blvd, Suite 200, Albuquerque, NM, 87110, US, collinska@cdmsmith.com
2John Shomaker and Associates, Inc., 2611 Broadbent Parkway, Albuquerque, NM, 87107, US
Los Alamos County has a contract for San Juan-Chama Project (SJCP) water and is currently evaluating alternatives for accessing their SJCP water from the Rio Grande. They are evaluating four alternatives that involve different methods for diversion, transmission route and treatment. The preliminary capital costs for these alternatives range from $7 million to $40 million. The four alternatives are:
1) Collector wells adjacent to the Rio Grande on San Ildefonso Pueblo with conveyance to the Guaje well field;
2) Utilizing Santa Fe’s Buckman Direct Diversion Project infrastructure and conveyance to White Rock;
3) Collector wells at the river connected to a tunnel and shaft that allows water to be pumped to the mesa top at White Rock; and
4) Groundwater wells on White Rock Overlook that would intercept river water.
Alternatives 1, 3, and 4 have hydrologic constraints. Alternative 1 relies on diverting water through an existing collector well. However, the results from collector well pumping test indicate that the aquifer limits the rate at which the collector well can sustain pumping and the Rio Grande is not close enough to offset aquifer dewatering. The collector well may be able to sustain pumping rates less than 500 gpm and establish equilibrium between removal of aquifer storage and recharge from the Rio Grande.
Alternative 3 anticipates diverting water through collector wells or raised bores at Site A, located downstream of San Ildefonso Pueblo and the Buckman Direct diversion. A groundwater-flow model was constructed to represent Site “A” and the Rio Grande and was calibrated to pumping test data from shallow wells installed in the alluvium adjacent to the Rio Grande. Model results indicated that a single collector well located on the north side of Site “A” would be capable of producing 1,200 AFY if a paleo-channel consisting of coarse-grained sediments underlies the Rio Grande.
Alternative 4 would divert groundwater through vertical water supply wells. The groundwater that would be diverted using supply wells is groundwater that naturally contributes to the Rio Grande. The reduction in stream flow from groundwater pumping and stream depletion would be offset by SJC Project water releases. Data from regional hydrogeologic studies by LANL were evaluated and the upper 300-ft of the regional aquifer below the White Rock Overlook appears to have adequate hydraulic properties for developing water for supply wells that would intercept stream flow.