Synopsis_GLEN 12-1027_Repair by Replacing Domestic Water Pumps B420

Rather than having two large domestic pumps, a combination of small and medium domestic pumps operating on Variable Frequency Drives (VFDs) shall cover a wider flow range. During normal operation, three pumps will cover a range of flow between about 100 GPM and 600 GPM. The Maximum Day Demand (MDD) plus fire flow demand shall be met with three medium pumps running in parallel. To provide a reliable water supply, a fourth identical medium pump shall be installed as a standby pump. Since the diesel fire pump is new as of 2012, this pump shall remain in service, as is, as a backup for firm capacity. Table 1 of the Design Analysis (pg 11, attached) lists the major pump and VFD equipment.  Additionally, all steel water piping infrastructure in and around Building 420 requires replacement, with pipes resized for the flows from the new pumps, and equipped with new valves and fittings to provide simplicity of maintenance and repairs. Pipe replacement is detailed in the design drawings.

The water distribution system shall supply water demands with sufficient service pressure and water quality over a range of fluctuating conditions that vary throughout the day and over the course of a year. AECOM created a hydraulic model using AFT Fathom software to verify and complete the final hydraulics. This included calculating the required head and pump turndown for each of the three pump types (Medium Pump, Small Pump, and Jockey Pump) at the required flow conditions, taking into account the frictional losses in the pipe system due to the recommended change in pipe sizes within the building. AECOM targeted a distribution pressure of 84 psi for normal water flow and 110 psi for fire flow.

Refer to “Design Analysis_Redacted - GLEN12-1027” (attached) for more details on demand and pump operating points.

The Contractor shall install a new fire department connection where easily accessed from the roadway. Exact location is to be determined by installer and approved by the SAFB fire department. Connection shall consist of two 2 ½ inch connections with NH internal threaded swivel fitting(s). Threading shall be 2.5 – 7.5 NH standard thread as specified in NFPA 1963.