Carollo completed a major study to replace the existing Sheffield Reservoir constructed in the 1930s, which provided storage for more than half the City’s service area. The original reservoir was a concrete-lined earthen, open reservoir and was subject to contamination and loss of chlorine residual. These conditions resulted in a water quality violation and the Department of Health Services issued a “boil water” advisory in 1998. The original reservoir had an impoundment capacity of 45 million gallons, but the City operated it at a volume of only 20 million gallons due to water quality problems. Carollo provided design and construction services for the award-wining permanent reservoir facility. The reservoir was sized for a storage volume of 13 million gallons with a capacity to expand to a total 19.5 million gallons with a third tank. Two 6.5 million gallon tanks were sited within the footprint of the original reservoir with an associated valve vault. A new chemical control building was included for storing and metering sodium hypochlorite to disinfect the potable water.
The two prestressed concrete tanks were 189 feet in diameter by 36 feet high conforming to AWWA standards. The prestressing procedure consisted of exterior wrapping the tank core wall with one to four layers of strand wires placed under tension to induce a compressive load on the concrete wall. The strand wrapped tank walls were then coated with a layer of shotcrete for corrosion protection. The two tanks and associated valve vault were buried as part of the new open space park.
Carollo is providing construction administration services for two 6.5-million gallon reservoirs. This includes attending meetings, reviewing submittals, responding to Requests for Information, conducting special field inspections, and coordinating with City staff. The 22-acre former reservoir site was developed as a passive open space park for public use. Carollo conducted a vulnerability analysis to address security features needed for open-space use. The old, defunct filtration building at the reservoir site was mothballed as part of a historical preservation program. Carollo provided primary design and construction services for the architectural landscaping design of the park, and architectural preservation design of the filtration building. Carollo provided design and construction services for rehabilitating a 75-year-old Zone Feed pipeline. The 18-inch cast iron pipeline routed underneath the filtration building and needed to be returned to service. Approximately 430 feet of an existing HDPE liner and annular grout needed to be removed from a previous rehabilitation. The pipeline was initially designed to be upsized to 24 inches using pipe bursting as a trenchless method of construction. This method of replacement could not be completed due to unforeseen geotechnical conditions. The pipeline was subsequently rehabilitated by sliplining 570 feet of thin-walled HDPE liner. The liner was rolled down to temporarily reduce its diameter to allow its insertion into the cast iron pipe while it was pulled into place.