14 - Laserfiche WebLink

casings were originally 1/4-inch to 5/16-inch thick steel, 12-inches to 18-inches in diameter, approximately 650 feet deep, and are 58 and 56 years old, respectively. Historical video footage showed scaling accumulation, minor structural defects, and some potential corrosion. As part of the basis of design report, Carollo Engineers was also tasked with doing an up-to-date video inspection of the casing that included inserting a camera into the casing while the pump remained in place. However, this work could not be completed as the "dummy tool" used as a test run on the out of service Well 8, unexpectedly became stuck between the casing and well pump. As a result, staff cancelled these activities at Well 5 and 6 to avoid operational risks to the active wells. Carollo Engineers has indicated that the "typical" life of a well casing of this construction and material is approximately 50 years (actual life will vary based on site specific conditions). Considering the goal of the Project is to extend the life of the well facilities by approximately 20 to 30 years, staff recommends evaluating the feasibility of rehabilitating and/or replacing the Well 5 and 6 casings as part of the basis of design report. Advanced condition assessment inspections of the well casings can be performed, but due to the extensive time, costs, and operational risks associated with those inspections, and the unlikelihood that results would support extending the life another 20 to 30 years, staff recommends performing the rehabilitation and/or replacement feasibility study as a first step. The casing for Well 8 is 28 years old and based on review of video inspection from 2013 appears to be structurally sound. Historical operational records do show that Well 8 has previously experienced water quality issues at higher pumping rates (above current operational pumping rates), which will be investigated as needed during final design once the desired pumping rate is confirmed. Potential mitigation measures are not anticipated to require replacement of Well 8 casing. CONCLUSION Staff recommends approving this first amendment with Carollo Engineers to perform additional services related to the Project's basis of design report. Additional services include: • CrVI Treatment- Perform a treatment evaluation that includes reduction coagulation filtration (RCF) and strong base ion exchange (SBA IX) technologies. For each alternative, the evaluation will determine treatment performance, estimate life cycle costs, summarize qualitative pros/cons, and identify provisions for inclusion into the Project. • Well 5 and 6 Casing Rehabilitation and Replacement— Perform an evaluation of the constructability and feasibility of casing rehabilitation or replacement, potential impacts to water yield and water quality, regulatory and permitting requirements, estimated construction costs, and how such improvements could coordinate with the overall Project schedule. • Optional Services— Include an allowance of approximately $25,000 for optional services that may be desired by the City after further development of the basis of design report. Anticipated optional services may include increased water sampling Page 3 of 4