Published
In St. Anthony, storm water is your problem to study before it is the city's problem to pipe
The city’s own description of its system starts with the word “minimal”
Most people assume a town the size of St. Anthony has storm sewer the way it has water and sewer. The city’s 2023 comprehensive plan, in its public services chapter, says otherwise in one sentence — and the sentence tells you what every new development inside city limits is expected to do about it:
“A minimal stormwater system is provided and maintained by the City of St. within the city’s boundaries. New developments will need to address storm water by preparing a storm water study preferably to identify how to maintain storm water on site, or to connect to the city’s storm water system.”
— City of St. Anthony 2023 Comprehensive Plan, public services chapter, “Storm Water”. The dropped “Anthony” after “City of St.” is the document’s own truncation, reproduced exactly. Retrieved 23 September 2026
Read the order of preference. On-site first, city pipes second. A developer inside St. Anthony is expected to study how to keep the water where it falls — retention, grading, infiltration — and connecting to the city’s system is the alternative, not the default. If you are buying a lot in a new subdivision, that order of preference explains the pond in the corner of the plat and the swales along the road: they are the storm water study, built — and they will show up on the recorded plat, where you can read them before you buy.
The one-acre line that brings in the federal rules
Below one acre of disturbance this is a city conversation. Cross it and a second rulebook opens:
“Generally, all developments that would disturb more than one acre of land or are part of a larger project are subject to the requirements of The Environmental Protection Agency’s Storm Water Pollution Prevention planning process (SWPPP).”
— City of St. Anthony 2023 Comprehensive Plan, public services chapter. Retrieved 23 September 2026
The trigger is one disturbed acre — or any smaller piece of a larger common plan. That second clause is the one that catches people:
- A half-acre lot inside a subdivision that will eventually disturb three acres in total carries the same federal requirement as the whole project.
- An SWPPP is a documented set of erosion and sediment controls — silt fence, stabilized entrances, inlet protection — kept current through construction.
- It is federal permitting that runs alongside the city’s local expectations, not instead of them.
The plan closes its storm water section with a sentence a buyer should hold onto: “As of present the City’s storm drainage is mapped but no study has been conducted.” Two facts live in that sentence:
- The map exists — held at the city office, it is the only drawn record of the system.
- Nobody has modelled it — no study of what the minimal system does in a big storm had been conducted, on the city’s own account in its own plan.
What this means at each stage
| You are… | What the city’s rules expect |
|---|---|
| Buying a lot in a new subdivision | The developer’s storm water study already happened — ask to see it, and ask which parts of the plat exist because of it |
| Building on an infill lot inside city limits | Expect to address runoff on site by grading and retention before anyone talks about connecting to city pipes |
| Disturbing more than an acre (or part of a bigger project) | An SWPPP applies — budget for it as its own line item, not a city fee |
| Building outside the city, in the belt | County ground, county rules — the Area of City Impact page explains which desk; storm water there is not the city’s minimal system |
Questions worth asking before you build
- Ask the city for the storm drainage map — the comprehensive plan says one exists and is held at the city office.
- Ask whether the storm water study the 2023 plan called for has been conducted since; the plan itself said none had been.
- If your project sits inside a larger common plan of development, ask who holds the SWPPP and what your lot’s share of it is.
- Walk the lot in rain, or find someone who has. On a system nobody has modelled, the water’s actual habits are the best study available.
- Then call (208) 656-1745 and pressure-test what you learned before the driveway is graded.
Common questions
Does St. Anthony have a city storm sewer system?
A minimal one. The city's own 2023 comprehensive plan describes 'a minimal stormwater system' maintained by the city within its boundaries, and expects new developments to prepare a storm water study identifying how to keep water on site, with connection to the city system as the alternative.
When does a storm water study get required in St. Anthony?
The comprehensive plan's language applies to new developments generally: they 'will need to address storm water by preparing a storm water study,' preferably one showing how water is retained on site. The city frames the study as the default expectation, with connection to city pipes as the fallback.
What is an SWPPP and when does it apply?
A Storm Water Pollution Prevention Plan - the federal EPA planning process for construction-site runoff. Per the city's plan, it applies to developments disturbing more than one acre of land, or that are part of a larger project, so a small lot inside a big subdivision can inherit the requirement.
Has the city ever studied its storm drainage?
Not as of its 2023 comprehensive plan, which states the city's storm drainage 'is mapped but no study has been conducted.' The map is held at the city office; ask whether a study has been completed since.
Do these rules apply outside city limits?
No - inside the city is city ground. Outside the limits, including in the Area of City Impact belt, the county's rules govern and the city's minimal storm system does not extend there.
Why does my small lot need erosion controls when it is under an acre?
Because the EPA trigger reads 'more than one acre of land or are part of a larger project.' Regulators treat a subdivision or phased project as one common plan of development, so each small piece carries the obligation attached to the whole.
Does an SWPPP replace the city's storm water study?
No - they run alongside each other. The storm water study is the city's comprehensive-plan expectation for new developments, focused on keeping water on site; the SWPPP is the federal EPA planning process for construction-site runoff, triggered at more than one disturbed acre or any piece of a larger common plan. A project inside city limits can owe both.
Where can I see the city's storm drainage map?
Ask at the city office. The 2023 comprehensive plan states the city's storm drainage is mapped, and the plan identifies the city office as where the map is held - it is the only drawn record of the minimal system.