A pair of engineers laid out the design and estimated cost of a new sewage treatment plant to the Belgrade City Council Tuesday that is estimated to satisfy the city needs until 2038.
The current sewage lagoon is bumping up against its state-mandated capacity with only a smattering of available space left after current and proposed developments are accounted for, according to city engineer Keith Waring and consulting engineer Scott Buecker, of Advanced Engineering and Environmental Services. The pair complied a Preliminary Engineering Report, or PER, that outlines options and costs associated with a new treatment plant. The report is necessary to secure government loans and grants.
Unlike other municipalities in the Gallatin Valley, Belgrade treats wastewater through groundwater dilution instead of a surface waterway, according to city records. To meet state thresholds, a mechanical facility is needed rather than expanding the current lagoons. Belgrade has the largest lagoon system in the state and was only able to boost discharge flows last year from 903,000 gallons per day to 1.25 million gpd “with the exception that the city takes measurable steps to upgrade the treatment system,” engineers wrote.
With everything all in, current and future uses, engineers estimate a flow of 1.12 million gpd, according to the report. City officials have stressed that number will not be realized until all of the currently approved residential and commercial construction projects are completed many years down the road. But the kicker is the city has to show it can accommodate growth before approving new projects.
What it costs
The engineers’ and city staff’s recommended project is estimated to cost $23,542,720. The total includes a $2.3 million contingency and $4 million in design and administrative costs. The recommended choice, officials said, is the best economic and design fit for the city. The facility can be expanded and uses many parts of the current lagoon system.
The cost will be covered through a variety of methods. Loans from the Montana State Revolving Fund will be the most likely way the bulk of the system will be covered. The 30-year loan has a 2.5 percent interest rate.
The city will also apply for a loan and possible grant from U.S. Department of Agriculture Rural Development. The program focuses on smaller communities and is one of the few grant opportunities available.
Also on tap is using impact fees from developers that contribute to infrastructure projects outlined by the city capital improvements list. The new water and sewer rates put into effect in November will also pay back any loan. City Manager Ted Barkley said the Airport Authority that governs Bozeman Yellowstone International Airport will chip in, too.
How it works
The mechanical plant will use three methods to treat effluent compared to the single method employed by the current lagoons, engineers said. In a nutshell, the process is as follows:
• Wastewater will enter a headworks building that removes large solids like rags, wipes, and vegetative matter via a drum screen. A grit separator will remove large particles like sand. Both byproducts will be dewatered and deposited in dumpsters to be hauled away.
• An oxidation ditch will move wastewater in a long continuous ring or oval basin for an extended aeration period that removes biodegradable organics.
• The last treatment moves the wastewater into a clarification tank that separates the solids. The solids are piped into a dumpster to be hauled away.
• The remaining process is similar to the current lagoon system where wastewater will be piped into the IP beds to percolate into the soil and/or used to irrigate land at Gallatin Field.
Engineers used a 3.5 percent growth rate for the next 20 years to come up with 19,360 residents by 2038, which is about double the current population of Belgrade. The facility can be expanded to for future growth.
The goal is to advertise for bids in March 2020, start construction in April 2020 and complete the project around Thanksgiving in 2021.