North Davis Wastewater Treatment Plant Upgrades and Expansion
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On this award-winning, design-build project, MWH increased the average daily wastewater treatment capacity from 25- to 34-mgd with peak flow capacity of 65 mgd, and an allowance to pass a storm flow of 102 mgd. These improvements doubled the daily biochemical oxygen demand and total suspended solids treatment capacity, while providing a better quality effluent than the existing process. MWH sequenced 10 task orders and supplied a guaranteed maximum price (GMP) for each one. This phased approach to project execution distributed the District’s capital expenditures over a five-year period while considering the plant’s operational and governmental requirements for discharges into the Great Salt Lake.
The facility used solar drying beds to dewater biosolids, which caused periodic seasonal solids backup and contributed to effluent quality problems. Through a series of value engineering workshops with the District, MWH incorporated solutions to this challenge and others.
Some of the construction task orders for the project included:
Headworks Improvements
Digester Mixing Improvements - Installed four external draft tube mixers on each of two existing 85-ft diameter primary digesters.
Solids Processing Facility - Constructed a new 25,000-sf building to house biosolids thickening and dewatering equipment.
Primary Clarifier Improvements - Added a fourth 150-ft diameter primary clarifier and installed additional air diaphragm pumps and sludge grinders in the primary sludge pump station.
Biotower/Solids Contact Process - Converted the existing two-stage trickling filter process to a single stage process. Built two 120-ft diameter by 30-ft high biotowers, 90-mgd biotower/trickling filter recirculation pump station. Added a solids contact process with eight aeration basins; blower building; return and waste sludge pump station; and three new 160-ft diameter final clarifiers. Added four 20-mgd pumps to the plant’s influent pump station and constructing a central warehouse building.
Disinfection System Expansion
Plant Power System Improvements - Replaced a 480-volt plant electrical power distribution system with a 12.7-kV distribution system that Included new substations, transformers and switchgear. Also added a 2-MW diesel emergency power generation system.
Site grading and Demolition
Laboratory and Staff Facilities- Expanded the lab and additional locker room and facilities.
Headworks Improvements
Digester Mixing Improvements
Solids Processing Facility
Primary Clarifier Improvements
Biotower/Solids Contact Process
Disinfection System Expansion
Plant Power System Improvements
Lab Upgrades
MWH sequenced 10 construction task orders and supplied a guaranteed maximum price (GMP) for each one.
Phased approach to project execution distributed the District’s capital expenditures over a five-year period while considering the plant’s operational and governmental requirements for discharges into the Great Salt Lake.
Intermountain Contractor awarded MWH two prestigious awards for this project:
