Chelsea, MA Environmental Rules: Stormwater Management (2026)

Sec. 30-223, Stormwater management, sits in the storm drains division of chapter 30 and applies to every existing property in the city. Subsection (a) requires owners to implement industry-standard structural and nonstructural best management practices, or BMPs, that minimize the pollutants stormwater runoff carries off their land into a public drain or natural outlet. Subsection (b) layers on additional duties whenever an owner establishes a new connection to the public drain, combined sewer or natural outlet, reconstructs or modifies an existing connection for an expanding facility, or when the director otherwise requires it: the owner must prepare and implement a stormwater management plan built around low impact development principles, prepare an erosion and sedimentation control plan for construction, monitor discharges for compliance with federal and state water quality standards, and design on-site measures to control both the rate, volume and characteristics of stormwater reaching the public system.

Paragraph (b)(5) sets a concrete minimum: oil and particle separators are required on all newly constructed private storm drains serving existing or new outdoor parking and paved areas that connect, directly or indirectly, to the public storm drain or a natural outlet, and the director may extend that requirement to existing private storm drains serving expanded parking areas. Subsection (d) ties the design standards to the Massachusetts Stormwater Handbook, requiring compliance with Handbook Standards 1, 2, 3, 5, 6 and 9 covering untreated discharge, peak runoff control, groundwater recharge, pollutant load reduction, wellhead protection and long-term maintenance, plus a numeric performance test of retaining one inch of runoff over the post-construction impervious area or removing 90 percent of average annual TSS load and 60 percent of TP load. Subsection (e) requires an operation and maintenance plan and as-built drawings before any required system starts up, at the owner's expense.