The City of Tioga found itself in the heart of the recent oil boom in western North Dakota. Being a hub of activity had its many advantages for the small town of 1,100 people however it also posed serious issues and unprecedented growth swelling the population to over 1,600 people and taxing City facilities with as many as an additional 800-900 transient workers based out of the community.
The City embarked on a flurry of activity including significant expansion of the incorporated city limits, expansion of city water and sanitary sewer services, expansion of the city’s lagoon system, implementation of a waste water treatment plant, construction of a new water tower, several blocks of water and sewer replacements, and multiple street improvement projects including the commercial sector of Main Street. Throughout all of this, the City’s aged Master Lift Station continued to deteriorate under the increasing demand on the City’s waste water system.
Originally constructed more than 50-years ago, the City’s Master Lift Station has remained largely unchanged. The Lift Station has received pump and control upgrades over the course of time but even those improvements had become obsolete over the course of more than 20-years. Over-cycling of the pumps due to limited wet well capacity, continuous maintenance of pumps due to foreign debris, obsolete equipment that could no longer be rebuilt, and regular overflow of the station due to down times and mechanical failures proved an imminent need to replace and upgrade the station.
As the City’s Engineer, Ackerman-Estvold reviewed the current facility and began planning and design of a new Master Lift Station early in 2017. With the oil boom removed and in a bust period, sizing the new facility became an important factor. Ensuring proper operation during lower periods of use while maintaining the ability to accommodate high flows and population growth provided a challenge in design and function. Ultimately, a wet well/dry well layout and building with a triplex pump system was settled on as the basis of design providing both redundancy and the ability to strategically increase flows under high or increased demand.
Once the capacity hurdle was accommodated in the preliminary design, the focus became operations and maintenance. Ackerman-Estvold worked hand in hand with the City’s Public Works Director of water and sewer facilities to outline and identify daily operations and hurdles. One of those parameters was accommodation of a grinder and screen system at the lift station to aid in the operations of the waste water treatment plant. This allowed the removal of foreign debris and non-organic objects through the use of an inline grinder, rotating screen assembly, and washed auger system. This system grinds and removes the debris, isolates the contaminants, and allows hygienic disposal of the reject material. This also proves beneficial for the pumps and downstream components. A FLYGT mixer was also incorporated into the wet well to ensure solids and other particles stay suspended until pumped and to help limit deposits within the wet well.
Three 30 HP FLYGT Model N3171 pumps were selected based on several factors. One of those factors being the ease of maintenance. With the motors horizontal to the pump and assembled atop a sliding rail system allows for easy separation and unparalleled access to the pump impellers and volute simply by loosening a few bolts and rolling the motors along the slide rail for separation. Additionally, a chain hoist system was design for removal of pumps and or motors.
Other elements were designed into the lift station to aid in maintenance and operations including a hot water pressure washer system plumbed throughout the building, a compressed air system also plumbed throughout the building, quick connection saddles at each pump for connection to the hot water pressure washer for flushing and sanitizing prior to maintenance, a tear down island and counter on the main floor, full stainless hardware and grating within the wet well for corrosion resistance, and separated rooms with the building section allowing the area above the dry well to be declassified saving money by eliminating explosion proof requirements of electrical equipment within this space.
With the lift station situated on a tight site with significant elevation relief, a rather unique opportunity presented itself for the overall layout of the facility. Essentially, it allows for a drive-up main floor where the controls, tear-down table and prominent maintenance accessories are located, and where the screenings from the wet well can be picked up for disposal. It also allowed for lower level access much like a walkout style basement for the dry well pump room. A garage door access was situated at the basement floor and an access was provided to that level allowing unparalleled access to the pumps, valves, and meter assemblies. With the incorporated chain hoist system, a maintenance truck could be backed into the dry well and pump or motor set directly into the truck for transport.
The Tioga Master Lift Station was bid in May of 2017 and was completed in June of 2018.