Horizon View No. 3 BPS Rehabilitation

Client: City of Bellevue

Horizon View No. 3 BPS Rehabilitation 2017-06-28T13:31:19+00:00

Project Description

RH2 evaluated the City of Bellevue’s Horizon View No. 3 Water Pump Station to stabilize pressures to a closed zone within the Summit neighborhood by evaluating the existing conditions, performing a hydraulic and pump station capacity analysis, and recommending mechanical and electrical improvements, and a standby generator for the pump station. Customers were experiencing pressure fluctuations of 20 psi because the pump station was controlled by a hydropneumatic tank. A combination of economic, social, and environmental issues were considered as part of a triple bottom line analysis to evaluate various pumping alternatives and generator systems.

Preliminary Design
Our team performed a detailed hydraulic analysis as part of the preliminary design to evaluate pumping alternatives, determine improvements needed to meet fire flow demands, and guide the design of a temporary pump station to supply the zone while the existing BPS was offline. We started by reviewing existing data, including the hydraulic model and construction records, and performed a site visits to confirm existing utilities and pump station appurtenances and take inventory of the electrical and control systems and connections.

RH2 analyzed more than 12 pumping schemes to optimize the selection of pumps given the space constraints of the BPS footprint and the hydraulic challenges inherent in the Summit zone. We prepared detailed charts to show the flow range for each alternative, including specific recirculation needs within specific flow ranges. Our analysis also included estimated annual pump runtimes for selected alternatives to show which option would cause the least amount of wear on the pumps each year. From this detailed analysis, the City was able to select the most energy efficient alternative, providing confidence that the drinking water supply and fire suppression for the Summit residents is maintained.

Our team also evaluated several locations both around the site and within the building footprint for locating the proposed standby generator. As part of the preliminary design RH2 reviewed City and King County noise requirements, diesel fuel storage and supply requirements, performed generator sizing and electrical load calculations, took inventory of all electrical conduits and wiring, and identified how exhaust from the generator would affect nearby property owners.

Rehabilitation Design
RH2 prepared the design to replace all of the existing mechanical and electrical components of the pump station and to remove the hydropneumatic tank to make way for a more efficient system. This included replacing the existing pumping equipment, generator, and electrical equipment, and separating a shared electrical service with the Eastside Public Safety Communications Agency’s (EPSCA) equipment located within the same building.

RH2 configured the pumps, suction, and discharge piping so that they are all laid out for easy access, maintenance, while still maintaining the design requirements. Bellevue decided to locate the emergency generator inside. We designed the room and roof extensions from the existing building to house the emergency generator. HVAC improvements to the existing system were also needed to accommodate the generator room addition.

The existing building, which included the EPSCA equipment on the upper level and the booster pump station on the lower level, was served by two electrical services with electrical loads shared between the two areas. The existing booster pump station was equipped with a small single-phase generator to power lighting and control loads and a diesel-engine fire pump. RH2’s design provided with City with complete electrical service separation between EPSCA and the booster pump station. This separation included reuse of an existing generator for EPSCA and a proposed generator for the booster pump station. As part of the pump and mechanical upgrade, the existing diesel-engine fire pump was replaced with electric motor driven pumps. In addition to a complete replacement of the electrical and mechanical systems, the telemetry equipment and instrumentation at the pump station was also replaced.

To maintain domestic and fire flow service to the customers in the Summit zone while the existing pump station was rehabilitated, RH2 prepared customized specifications for the temporary pumping system to maintain drinking water supply and fire suppression for the Summit residents throughout the duration of construction.

Construction Support and Additional Services
RH2 provided contractor submittal review, responses to RFIs, MCC testing, as well as other startup and testing support, and O&M manual review. In addition, along with preparing the construction plans, specifications, and estimate, Bellevue requested an arc flash analysis to provide operating recommendations for the proper function of the protective devices within the pump station’s electrical system. Our team prepared this analysis so Bellevue can be confident that they are providing their operations staff with the most current safety information on the new equipment.