Beltz 10 Aquifer Storage and Recovery & Beltz 11 Well Injection Pilot Tests

The City of Santa Cruz Water Department is seeking to pilot test aquifer storage and recovery and well injection at its existing Beltz 10 well facility, which has two wells on site, Beltz 10 and Beltz 11, as part of a feasibility study to assess the viability of diverting excess surface water to the Santa Cruz Mid County Groundwater Basin. The Beltz 10 pilot test requires installing a monitoring well at the City's existing Beltz 10 well facility. The pilot testing is expected to last up to 150 days from 2026 to 2027. The City of Santa Cruz Water Department is seeking to pilot test aquifer storage and recovery (ASR) and well injection at its existing Beltz 10 well facility, which has two wells on site, Beltz 10 and Beltz 11 , as part of a feasibility study to assess the viability of diverting excess surface water to the Santa Cruz Mid County Groundwater Basin. The Beltz 10 well facility is shown on figure one. The ASR pilot testing of the Beltz 10 well seeks to field demonstrate the potential application of ASR in the in the A/AA unit Purisima Aquifer system. A new monitoring well will be installed as part of this work. The injection pilot testing of the Beltz 11 well seeks to investigate the potential to raise water levels in the Tu aquifer. The pilot testing results will be used to assess viability of the storage of drinking water underground at the Beltz 10 well facility and will provide the basis for the design and permitting for a long-term full-scale ASR and/or well.injection project. Preparation of Beltz 10 and Beltz 11 wells for pilot testing will include downhole cleaning procedures and modifications to the wells to establish a connection to the distribution system, retain or exchange pumps and add appurtenances. The ASR pilot test at Beltz 10 requires installing a monitoring well at the City's existing Beltz 10 well facility. This new monitoring well will be used to collect water level and water quality data. The monitoring well will be 2.5 inches in diameter. Drilling will be performed using the direct rotary method with bentonite-based fluid, which will be hauled offsite for disposal. Higher turbidity discharges from well development will be routed to the to the Beltz Water Treatment Plant (Beltz WTP) reclaim tank, which drains to the sanitary sewer system. Lower turbidity discharges from well development will be routed via the existing raw water pipeline to the unnamed creek at 30th Ave, a tributary to Moran Lake. A monitoring well vault and manhole will be installed to provide access for instrumentation, monitoring, or sampling. All construction activities will occur during working hours Monday through Friday 8am to 5pm consistent with County noise ordinance requirements. Construction of the monitoring well will require 12 working days. Some tree limbs will be required to be removed to allow the drill rig to access the site. The ASR pilot test at Beltz 10 will involve three repeated injection storage and recovery cycles with increasing quantities of water. Cycle 1 is expected to recover about 0.44 million gallons (mg). Cycle 2 is expected to recover about 3 mg. Water from Cycles 1 and 2 will be routed via the existing raw water pipeline to the unnamed creek at 30th Ave, a tributary to Moran Lake. Cycle 3 injection operations, if water quality pilot testing results from Cycles 1 and 2 are favorable, will result in the recovery of 13 mg that will be treated at the Beltz WTP will go into the distribution system. Water levels will be monitored after recovery. The injection pilot test at Beltz 11 will involve two repeated injection storage and recovery cycles at with increasing quantities of water extracted after injection. Cycle 1 is expected to recover about 0.1 million gallons (mg). Cycle 2 is expected to recover about 1 mg. Cycle 3 injection operations, if water quality pilot testing results from Cycles 1 and 2 are favorable, will result in the storage of 10 mg. Water levels at an existing monitoring well will be monitored to assess the response to injection at Beltz 11. Noise typical of existing operation noise will occur during pilot testing. The pilot testing is expected to last up to 150 days from 2026 to 2027.