City considering contract for updated stormwater master plan

During their Oct. 18 meeting, City Commissioners will consider awarding a $450,327.57 professional services agreement with Great West Engineering Inc. for the city’s stormwater master plan update project.

Staff is recommending approval of the agreement.

The city is looking to hire Great West to prepare a master plan including an in-depth summary of the existing drainage basins and drainage patterns, system layout, system capacities, system issues, analysis of alternative, cost estimates for improvements, recommendations for improvement and a comprehensive rate study, according to the city staff report.

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The utility rate study would look at the rates needed to support the operation, maintenance and capital financial requirements for the city’s stormwater system and will be based on the utility finance methodologies used in the industry and meet the city’s needs, according to the staff report.

City Commissioners adopted the current storm drainage master plan in 1989. At that time, the plan analyzed and identified drainage deficiencies and provided concepts for construction of future facilities needed to serve the city and prioritized system maintenance and improvement projects. Since then, updates and additions have been done with smaller studies and projects, according to the staff report.

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The 1989 plan recommended the creation of a storm drain fee to pay for upgrades and maintenance and that fee was created that year. The first rate increase was in 2002 and the last rate increase was in 2019, made by commission resolution, according to the staff report.

The study process will include public outreach and input, according to the staff report.

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The project will update the outdated master plan and generate a hydraulic model of the city’s storm sewer network using the city’s existing storm drain utility mapping, as-built plans and Lidar data, according to staff. Supplemental surveying will be done where existing information doesn’t exist.

The storm drain model will be run and refined for various storm events to analyze the capacity of the existing system and identify areas of surcharging and overtopping, according to staff, and provide a range of drainage concepts for construction of future facilities needed to serve the city as it grows and prioritize system maintenance and improvement projects.

The plan will analyze possible locations for city-owned regional storm water detention/retention ponds that will be included in the modeling to identify whether they could help alleviate downstream flooding issues, according to the staff report.

The plan will also include information on industry practices used by other Montana municipalities and industry standards for stormwater rate structures, present alternative structures for the city’s consideration and recommend a course of action, according to staff.

The rate study will determine the revenue needed to meet the stormwater system’s financial obligations, including capital, operating and policy-driven commitments; it will also summarize key assumptions, methodology, results, considerations and provide recommendations, according to staff.

The project was selected and prioritized under the public works capital improvement plan; and budgeted with storm sewer funds, unassigned capital improvement funds and enterprise fund, according to staff.