Environmental Rules in Costa Mesa, CA (2026)
4 verified environmental rules for Costa Mesa, California, sourced directly from the municipal code and official government pages.
Verified from official government sources
Stormwater Management
Costa Mesa bans any illicit connection to the storm drain system and any prohibited discharge of pollutants into it, gutters, or the Pacific Ocean under Municipal Code § 8-31. New development and significant redevelopment must also follow the county's Drainage Area Management Plan before the city will issue a grading, building, or plumbing permit.
Costa Mesa Stormwater Discharge Prohibition
Significant RestrictionsCosta Mesa, CA, Municipal Code § 8-31
§ 8-31. Prohibition on illicit connections and prohibited discharges. (a) No person shall: (1) Construct, maintain, operate and/or utilize any illicit connection. (2) Cause, allow or facilitate any prohibited discharge. (3) Act, cause, permit or suffer any agent, employee, or independent contractor, to construct, maintain, operate or utilize any illicit connection, or cause, allow or facilitate...
Erosion Control
Costa Mesa requires grading and excavation work to comply with the Orange County Grading and Excavation Code, adopted under Municipal Code Section 5-1.4, in addition to Appendix J of the 2025 California Building Code, with the more restrictive of the two controlling. Only minor fills under specific volume and depth limits are exempt, and even those still need a compaction report.
Costa Mesa Grading Erosion Control Requirements
Some RestrictionsCosta Mesa, CA, Municipal Code Sec. 5-1.4.1
Article 8 of Title 7, Division 1 of the Codified Ordinances of the County of Orange, including the Grading Manual, is adopted in its entirety, except that section 7-1-805(i) and 7-1-805(l) are modified as follows: Section 7-1-805(i). A fill less than one (1) foot in depth which: (1) is placed on a natural grade with a slope less steep than five horizontal to one vertical (5:1); (2) does not exc...
Flood Zones
Costa Mesa applies extra floodway and floodplain rules to any property within a FEMA-mapped flood hazard area on the Orange County Flood Insurance Rate Map. Inside the regulatory floodway itself, dwelling units and most permanent structures are flatly prohibited, and only flood-control, utility and open-space uses are allowed by right.
Costa Mesa Floodway & Floodplain Development Rules
Significant RestrictionsCosta Mesa, CA, Municipal Code §§ 13-79(a), 13-80(b)(1)-(2)
(a) In any base flood district, when the property is included within a designated flood hazard area shown on the adopted Orange County (countywide) Flood Insurance Rate Map (FIRM) dated August 9, 2002, or a subsequent FIRM, of flood boundary and floodway maps as published by the Federal Emergency Management Agency (FEMA), the additional requirements, limitations and standards contained in this ...
Flood Elevation Requirements
Every new home or substantially improved structure in a Costa Mesa flood hazard area must have its lowest floor, including any basement, elevated to or above the base flood elevation, certified by a registered engineer or surveyor. In Zone AO or AH without a mapped depth number, the code sets a two-foot minimum above the highest adjacent grade.
Costa Mesa Base Flood Elevation Requirements
Some RestrictionsCosta Mesa, CA, Municipal Code § 13-82(d)(3)-(4)
(3) New construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated to or above the base flood elevation. Nonresidential structures may meet the standards in subsection (d)(5). Upon completion of the structure, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor and prov...
Looking for Orange County county-wide rules?
County ordinances apply to unincorporated areas and may supplement Costa Mesa city rules.
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