Environmental Rules in Arapahoe County, CO (2026)
6 county-level rules, plus city-specific rules for 2 cities in Arapahoe County, Colorado.
Verified from official government sources
Stormwater Management
In unincorporated Arapahoe County, every detention pond, bioretention facility, sand filter, grass swale and major drainageway built as part of a development must be designed, planted and maintained to the County's Stormwater Management Manual and approved by the Engineering Services Division. Regional and sub-regional detention facilities are exempt unless the Board of County Commissioners orders otherwise.
Arapahoe County Stormwater Drainage Standards
Some RestrictionsArapahoe County Land Development Code § 4-1.4.E.7
g. Stormwater Facilities i. Detention and Water Quality Areas. All improvements within a detention area shall be approved by the Engineering Service Division to ensure compliance with approved drainage plans. Regional and sub-regional detention facilities are exempt from these requirements unless otherwise determined by the Board of County Commissioners... 2. Detention ponds with earthen sides ...
Erosion Control
Unincorporated Arapahoe County requires a Grading, Erosion and Sediment Control (GESC) permit before any regulated land disturbance begins. The permit, issued under the county's GESC Manual, applies countywide outside incorporated cities and must be secured before or alongside your building permit: skipping it is a zoning violation.
Arapahoe County Erosion & Sediment Control Permit
Some RestrictionsArapahoe County Land Development Code § 5-4.2
b. Applicability i. These Regulations shall apply to all property within the unincorporated areas of Arapahoe County. ii. No land disturbance shall occur on any property, unless otherwise exempted via provisions in the GESC Manual without first obtaining a GESC permit from the County. Such permit is subject to all applicable fees. iii. Persons proposing to conduct regulated land disturbance act...
Flood Zones
Unincorporated Arapahoe County bars new construction, fill and other development inside an adopted regulatory floodway under LDC § 4-3.5.D unless a Colorado-licensed engineer certifies no rise in flood levels or the county approves a Floodplain Modification Study, keeping mapped floodways clear for flood conveyance.
Arapahoe County Floodway Development Ban
Significant RestrictionsArapahoe County Land Development Code § 4-3.5.D
The floodway as defined in Section 7-2 is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and has erosion potential. Floodways are located within special flood hazard areas established in Section 4-3.4.B. The County has adopted a one-half foot floodway requirement. For special flood hazard areas which have a designated floodway, the fol...
Defensible Space
Every structure in unincorporated Arapahoe County must keep a noncombustible buffer: gravel or crushed rock at least two inches thick beneath decks and around the foundation, extending three feet past exterior walls and five feet past eave and deck driplines. Walls, fences and retaining walls within five feet of a building must be noncombustible, and grass near structures must stay mowed to four inches or less.
Arapahoe County Wildfire Defensible Space Rules
Some RestrictionsArapahoe County Land Development Code § 4-1.4.E.10
j. Wildfire Defensible Space Colorado's population is growing, its urban and rural areas are rapidly expanding, and landowners need to know how to correctly landscape their property to reduce wildfire hazards. The following standards apply to all structures. i. Gravel or crushed rock not less than ¾-inch in diameter or other non-combustible material applied at least two inches thick must be ins...
Vehicle Idling Restrictions
In unincorporated Arapahoe County, engine idling at a permitted Oil and Gas Facility must be minimized at all times, and between 7:00 p.m. and 7:00 a.m. it is hard-capped at 10 minutes. The limit sits inside the Noise Mitigation Requirements every well pad approved by Use by Special Review must follow under Land Development Code § 5-3.6.
Arapahoe County Oil & Gas Idling Limits
Some RestrictionsArapahoe County Land Development Code § 5-3.6, Standards Required for Oil and Gas Facilities — Noise Mitigation Requirements, ¶ l.xiii
xiii. Engine idling shall be minimized. Between the hours of 7:00 p.m. and 7:00 a.m., engine idling is limited to 10 minutes.
Flood Elevation Requirements
Unincorporated Arapahoe County requires a minimum two feet of freeboard above the 100-year base flood elevation for the lowest floor of substantially improved structures in a floodplain under LDC § 4-3.5.C, with a lighter one-foot minimum for non-structural facilities like roadways and trails.
Arapahoe County Freeboard Elevation Standard
Some RestrictionsArapahoe County Land Development Code § 4-3.5.C
A minimum clearance, or freeboard, shall be provided between the floodplain or special flood hazard area and structures, and other applicable facilities, which may be impacted by or adjacent to the floodplain... a. The County requires a minimum of two-feet of freeboard between the 100-year water surface elevation and the lowest floor elevation (including basement) of all substantially improved ...
Environmental Rules by City in Arapahoe County
2 cities in Arapahoe County have their own environmental rules rules. Each link goes to that city's dedicated page with code citations.
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