9 9 CITY OF EVERETT PARCEL 2023-12-27

Landau Associates Once existing extraction well EGW192 has been disconnected from the main conveyance line, the existing lateral line to the primary force main (along with existing electrical and communications lines) will be excavated and capped. The new conveyance line to EGW192R will be constructed in engineered trenches. Piping will be placed on top of at least 6 inches of bedding material and covered with at least 3.5 ft of select fill. Trench details are shown on the Construction Drawings (Attachment 1). Extraction Well Monitoring, Controls, and Power Extraction well EGW192R will be equipped with a pressure transducer to monitor groundwater levels within the well.The central control system will be programmed to read and monitor the level and alter the pumping rate of the extraction pump, as necessary, to maintain the desired groundwater elevation drawdown in the well for hydraulic control of the groundwater plume. Pressure indicators and transmitters will be installed at the top of the extraction well riser piping within the well vault to monitor for excess or sudden declines in water pressure that might indicate a blockage or a leak in the conveyance system. The central control system will be programmed to signal an alarm in the event of potential blockage or failure in the conveyance piping and will shut down the system (and send an alarm) if a leak is detected. A flow meter and transmitter will also be installed on the piping within the well vault to monitor flow rates and total extracted volume from the well.The flow meter at the end of the conveyance piping (in the treatment building) will perform the same function. By data comparison, the programmable logic controller (PLC) is programed to detect the potential presence of leaks or other failures in the conveyance piping. Consistent with the rest of the GET system monitoring, the sum of the individual flow rates from each well versus total combined flow into the treatment system, within a given tolerance, will be used to determine potential water loss between the extraction wells and treatment system. A local control panel proximate to existing well EGW192 has hand-off-auto pump controls, power disconnects, and lighted displays for pump-on and system alarm indication. New well EGW192R will connect into the existing control panel for EGW192. Control panel labels and electrical drawings stored in the control panel will be updated to reflect the new well and its connections. Power to the well will be run from the Snohomish County Public Utilities District No. 1 (PUD)transformer installed for the Phase 1 IA north of Seaway Boulevard. Power lines will be run in underground conduits to the new extraction well. Water lines will be separated from power lines on the primary side of transformers by at least 3 ft in accordance with the PUD requirements. EGW192 Relocation Work Plan Powder Mill Gulch—Boeing Everett Plant 6 October 1, 2020