Elk River Waste Water Treatment Plant Wet Weather Improvements 2025

Elk River Waste Water Treatment Plant Wet Weather Improvements 2025

The proposed project requires a new Trickling Filter wet well and pump station to be constructed to handle the peak wet weather flow for 24 MGD, including three (two duty and one standby) new pumps with Variable Frequency Drives. To accommodate peak wet weather flow of 24 MGD through secondary treatment requires upgrading the return secondary solids pumps to handle increased flows. For two secondary clarifiers, the return secondary solids pumps need a combined capacity of 7,500 Gallons per Minute (GPM) with both clarifiers and all four pumps in service, with each pump delivering 1 ,875 GPM. Redundancy would be provided by having redundant units in storage, available to be installed as needed. Up to 8 MGD of excess primary treated flows can be transferred to the newly converted lined equalization basin. This requires a primary effluent transfer station with a capacity of 5,600 GPM (8 MGD), an equalization basin Lift Station with a capacity of 5,600 GPM (8 MGD), and yard piping ranging in size between 14 and 20- inch diameters to transfer the excess flow to the equalization basin and back to secondary treatment. All construction will be within the footprint of the existing plant. Excavated material will be temporality stockpiled on-site, then hauled off-site to a permitted disposal site, to be approved by the City prior to the start of construction. The bottom 10 inches will be backfilled with compacted Class 2 aggregate base material and paved to match the existing grade. The contractor’s staging areas are located next to the secondary clarifiers, behind the sludge holding tanks, and in front of the administration building, see attached site plan. The staging area behind the sludge holding tanks will allow for items needed for day-to-day operations, while the area near the secondary clarifiers will be for larger materials and storage. The area in front of the administration building will be a backup for any additional material storage. The proposed staging area is less than one acre, but if the contractor’s staging area expands in total project disturbance of more than one acre, the contractor will be required to prepare and comply with a Stormwater Pollution Prevention Plan in accordance with Construction General Permit Order 2009-0009- DWQ. All staging areas will be restored to original conditions once the project is completed. This project has milestones based on when work can be completed in the wet and dry seasons. The Summer/Fall 2024 (dry season) will consist of dredging the sludge, dewatering, and haul off sludge in facultative sludge lagoon, trickling filter pump station structure construction, secondary pump station improvements, yarding piping and electrical conduits. The winter of 2025/Spring of 2026 will consist of installing pumps, fittings, and motor controls. Summer/Fall 2026 will consist of equalization regrading, installing basin liner, pumps and piping. Winter of 2026 will consist of testing, training and start up. Typical working hours will be Monday through Friday, 8:00 am to 4:30 pm; if additional time is needed the contractor will coordinate with City staff to schedule working on Saturdays from 8 am to 4:30 pm. No work or use of equipment will be allowed at night.

Eureka

Humboldt

Northern California

Humboldt