Carver County, MN Environmental Rules: Stormwater Management (2026)
Key Facts
- Governing section
- Carver County Code § 153.56
- TP/TSS removal standard
- 90% of both, developed conditions
- Volume control standard
- 1 inch impervious runoff (0.5 constrained)
- Peak rate standard
- No increase for 2-, 10-, 100-yr storms
- Enforcing agency
- Carver County Water Management Organization
- Maintenance agreement
- Required before plan approval
Summary
Carver County requires stormwater management plans for new development to control both the rate and quality of runoff before it reaches lakes, streams, and wetlands. Under County Code § 153.56, projects must remove 90% of total phosphorus and 90% of total suspended solids generated on-site, hold peak runoff rates at pre-development levels, and route treatment through the county's Water Resource Management program.
(E) Rate control standard. (1) Peak rates. The peak rates shall not increase from existing conditions for the two-, ten-, 100-year storm events, and the 100-year, ten-day snowmelt event. Peak rates shall be calculated using Atlas 14 precipitation depths and storm distributions. (2) Conveyance system. At a minimum, the storm sewer conveyance system shall be designed for a ten-year, 24-hour storm event. The pond and pond outlet structure shall handle the 100-year, 24-hour storm event. (F) Water quality standard. (1) Total Phosphorus (TP) removal standards. The stormwater management plan must remove 90% of the TP generated by the site under developed conditions. (2) Total Suspended Solids (TSS) removal standards. The stormwater management plan must remove 90% of the TSS generated by the site under developed conditions.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2025 S-20: Supplement contains: Local legislation current through Ord. 111-2025, passed 7-25-25).
Full Breakdown
70. 56 sets the technical standards an applicant must meet before the Carver County Water Management Organization (CCWMO) approves a stormwater plan. Peak discharge rates cannot exceed existing conditions for the two-year, ten-year, and 100-year storm events, plus the 100-year, ten-day snowmelt event, calculated with Atlas 14 precipitation data. The storm sewer conveyance system itself must be sized for at least a ten-year, 24-hour storm, while ponds and outlet structures must handle the full 100-year, 24-hour event. 56(G) requires volume control equal to one inch of runoff from impervious surfaces on unconstrained sites (one-half inch on sites the county designates 'constrained,' such as those with contaminated soils or shallow bedrock).
56(I)(2). Applicants who cannot meet these numbers on-site may pursue offsite treatment, purchase banked credit within the CCWMO, or pay into the county's Stormwater Treatment In-Lieu Fund calculated from the Carver County fee schedule. 73, secures the work until the site reaches 90% vegetated cover (100% in concentrated-flow areas) and a final inspection is complete.
Violations & Fines
Building without an approved plan, or failing to maintain required BMPs, lets the county issue a stop-work order, a notice of violation, or an order for correction under § 153.71. The county can withhold inspections or a certificate of occupancy, revoke prior approvals, and sue for injunctive relief; costs of any county-performed corrective work may be certified to the County Auditor as a special assessment against the property.
Frequently Asked Questions
Does Carver County's stormwater rule apply inside cities like Chaska?
What happens if my site can't hit the 90% removal numbers on-site?
How does the county size the conveyance system for a new subdivision?
Sources & Official References
Other rules in Carver County
Compare Carver County to another location·View the Minnesota environmental rules overview
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