Weld County, CO Environmental Rules: Stormwater Management (2026)

Chapter 8, Article IX of the Weld County Code establishes the county's Municipal Separate Storm Sewer System (MS4) program, administered by the Department of Public Works under the Public Works Director's authority. Section 8-9-70(A) makes it 'unlawful for any person to discharge or cause to be discharged into the MS4 any pollutants that cause or contribute to a violation of applicable water quality standards,' and further declares that 'only stormwater may be discharged into the MS4' outside the exceptions the article allows; pollutants left where they threaten to reach the system are themselves treated as a discharge unless actively being cleaned up, and any illicit connection to the MS4 is a separate violation even if it predates this article.

Construction sites face their own pre-construction, construction-activity and post-construction control requirements under Sections 8-9-80 through 8-9-100, and any site disturbing an acre or more must install permanent control measures. Enforcement escalates from an informal notice, through compliance inspections, to a formal notice of violation if the problem isn't fixed within 14 days; a formal notice can be appealed to the Board of County Commissioners within 15 days, with a hearing held within 15 days of that appeal. S. Section 30-15-401(11), and abatement costs plus 5% for inspection become a lien against the property, collected with a 10% penalty if unpaid within 60 days of notice, per Sections 8-9-130 and 8-9-140.