A. 
The city of Mill Creek is required to comply with the Washington State Growth Management Act (Chapter 36.70A RCW) to designate natural resource lands and environmentally critical areas and to adopt development regulations to assure the conservation of such areas. In compliance with this mandate, the city finds that environmentally critical areas characterize certain portions of Mill Creek and its urban growth area. These critical areas include wetlands, fish and wildlife habitat conservation areas, critical aquifer recharge areas, geologically hazardous areas, and frequently flooded areas.
B. 
The purpose of this chapter is to designate and classify environmentally critical areas and to protect these areas and their functions and values, while also allowing for reasonable use of private property.
C. 
By limiting development and alteration of critical areas, the city seeks to:
1. 
Protect members of the public and public resources and facilities from injury, loss of life, or property damage due to landslides, steep slope failures, erosion, seismic events, or flooding;
2. 
Protect citizens and the unique, fragile, and valuable elements of the environment, including ground and surface waters, wetlands, anadromous fish species, and other fish and wildlife and their habitats;
3. 
Prevent adverse and cumulative environmental impacts to critical areas, direct activities not dependent on critical area resources to less ecologically sensitive sites, and mitigate unavoidable impacts to critical areas by regulating alterations in and adjacent to critical areas and requiring specific mitigation measures to compensate for unavoidable impacts;
4. 
Protect species and habitats listed as sensitive, threatened, or endangered by the state or federal government by prohibiting activities that kill, harass, harm, trap, collect, wound, hunt, or pursue such species/habitats.
(Ord. 2004-603 § 2; Ord. 2026-945 § 2 (Att. A))
A. 
The intent of this chapter is to avoid impacts from alteration of critical areas where such avoidance is feasible and reasonable. In appropriate circumstances, and consistent with the requirements of this chapter, unavoidable impacts to critical areas shall be minimized, rectified, restored and/or compensated for through appropriate levels of study and analysis, application of best available science, engineering, and planning principles, and regulation and limitation of land uses.
B. 
It is the further intent of this chapter to:
1. 
Implement the goals, objectives, and policies of the city of Mill Creek comprehensive plan;
2. 
Serve as a basis for exercise of the city’s substantive authority under the State Environmental Policy Act (SEPA) and the city’s SEPA regulations (Chapter 18.04 MCMC);
3. 
Comply with the requirements of the Growth Management Act (Chapter 36.70A RCW) and implementing rules and guidelines and through the application of best available science, as determined according to WAC 365-195-900 through 365-195-925, and in consultation with state and federal agencies and other qualified professionals;
4. 
Coordinate Mill Creek’s critical area protection activity and programs with those of other jurisdictions;
5. 
Coordinate environmental review and permitting of development proposals to avoid duplication and delay; and
6. 
Use flexibility permitted by this chapter in establishing buffer width and area standards and reasonable use on a case-by-case basis, considering the functions and values of the critical area and particular constraints on a parcel of land that make compliance with the strictest standards of this chapter unreasonable.
C. 
The city’s enactment or enforcement of this chapter shall not be construed for the benefit of any individual person or group of persons but only for the general public.
(Ord. 2004-603 § 2)
The city finds that critical areas contain valuable natural resources, provide natural scenic qualities important to the character of the community, perform important ecological functions and processes, and/or present a hazard to life and property. Identification, management, and protection of these areas is, therefore, necessary to protect the public health, safety and general welfare of Mill Creek’s citizens and comprise a public purpose. Beneficial biological and physical functions that critical areas provide include, but are not limited to, water quality protection and enhancement; fish and wildlife habitat; food chain support; flood storage; stormwater conveyance and attenuation; ground water recharge and discharge; erosion control; protection from hazards; historical and archaeological and aesthetic value protection; and recreation. These beneficial functions are not listed in order of priority. With respect to particular critical areas, the city finds as follows:
A. 
Wetlands.
1. 
Wetlands perform numerous important functions, including but not limited to provision of wildlife and fish habitat, water quality enhancement, flood and erosion control, ground water recharge and discharge, shoreline stabilization, research and education opportunity, and recreation. Protection of these systems is necessary to protect the public health, safety, and general welfare.
2. 
To achieve the goal of “no net loss” of wetland functions and values within the city, the regulations of this chapter are intended to discourage or prohibit:
a. 
Activities that block water flows, or damage or destroy flood storage areas or storm barriers, thereby resulting in greater potential flood damages;
b. 
Disposal of wastewater or solid wastes, or creation of unstable fills inappropriate to the function of wetlands, which may result in water pollution;
c. 
Application of pesticides, herbicides and algaecides on wetlands unless warranted to protect the ecological functions of the wetland;
d. 
Activities that limit the function of a wetland to control erosion or runoff; provide water storage; or provide wildlife breeding, spawning, nesting, wintering, or feeding grounds; and
e. 
Activities that detract from a wetland’s value in providing educational experiences, recreational uses, and/or open space.
B. 
Fish and Wildlife Habitat Conservation Areas.
1. 
Streams and other fish and wildlife habitats perform many important biological and physical functions that benefit the fish and wildlife species inhabiting the region. These functions include, but are not limited to: providing cover, breeding/spawning habitat, and food for fish and wildlife species; maintaining water quality; storing and conveying storm and flood water; and recharging ground water.
2. 
Habitat areas also serve as a valuable resource for city residents by providing areas for recreation, education, scientific study, and aesthetic appreciation. Protection of these systems is necessary to protect the public health, safety, and general welfare.
C. 
Critical Aquifer Recharge Areas.
1. 
Areas that have a critical recharging effect on ground water are essential for maintaining public water supplies including supplies of potable drinking water. These areas are susceptible to contamination from certain land use activities. Protection of these systems is necessary to protect the public health, safety, and general welfare.
2. 
Critical aquifer recharge areas have prevailing geologic conditions associated with infiltration rates that create or contribute significantly to the replenishment of ground water.
D. 
Geologically Hazardous Areas.
1. 
Geologically hazardous areas pose a risk to public property, welfare, and to the natural systems that make up the environment of the city. Natural processes make these areas susceptible to landslides, erosion, and seismic events. Regulation of these areas to avoid or minimize geologic hazards is necessary to protect the public health, safety, and welfare.
2. 
Areas subject to topographic variation – such as hillsides and ravines – provide natural scenic qualities, aesthetic resources, and community character as well as important ecological functions and values. Removal of vegetation and development in such areas can result in loss of soil and slope stability, increased erosion, increased surface water runoff, and reduced aesthetic value. These areas should be protected and enhanced consistent with their natural functions, visual qualities, and inherent development limitations.
E. 
Frequently Flooded Areas. Areas subject to frequent flooding provide valuable habitat for many fish and wildlife species and also pose a risk to public health and safety. Protection of floodplains and areas subject to frequent flooding is necessary to protect human life and property. The provisions of this chapter seek to prevent damage to public facilities, minimize the need for flood relief or flood control projects, and protect the natural resource functions and values provided by frequently flooded areas. Protection and management of frequently flooded areas shall be in accordance with the provisions of Chapter 15.20 MCMC and shall protect the public health, safety, and welfare.
(Ord. 2004-603 § 2; Ord. 2026-945 § 2 (Att. A))
A. 
The city has identified portions of the Mill Creek planning area, based on studies and field investigations, where critical areas, or the conditions under which critical areas typically occur, are believed to exist. The approximate location and extent of critical areas within the city’s UGA are shown on the Mill Creek comprehensive plan environmental element (as amended) maps adopted by reference as part of this chapter. These maps are intended to be used as a general guide for the assistance of property owners and as information for the public. Critical area locations and boundaries are approximate; field investigation and analysis by a qualified professional are required to confirm the existence and boundaries of a critical area. In the event of any conflict between the location, designation, or classification of a critical area shown on the city’s maps and the criteria or standards of this chapter, the criteria and standards and the determination of any field investigation shall prevail. All areas within the city meeting the definition of one or more critical areas, regardless of any formal identification, are hereby designated critical areas and are subject to the provisions of this chapter.
B. 
Areas adjacent to critical areas shall be considered to be within the jurisdiction of these requirements and regulations to support the intent of this chapter and ensure protection of the functions and values of critical areas. Adjacent shall mean any activity located:
1. 
On a site immediately adjoining a critical area;
2. 
A distance equal to or less than the required critical area buffer width plus building setback;
3. 
Within the floodway, floodplain, or channel migration zone; or
4. 
A distance equal to or less than 200 feet from a critical aquifer recharge area or geologically hazardous area.
(Ord. 2004-603 § 2; Ord. 2026-945 § 2 (Att. A))
A. 
Any action taken pursuant to this chapter shall result in equivalent or greater functions and values of the critical areas associated with the proposed action, as determined by the best available science. All actions and developments shall be designed and constructed to avoid and/or minimize all adverse impacts. Applicants must first demonstrate the inability to avoid or minimize impacts before restoration and compensation of impacts will be allowed in accordance with MCMC § 18.06.625. No activity or use shall be allowed that results in a net loss of the functions or values of critical areas within the city and its UGA.
B. 
These critical area regulations shall apply as an overlay and in addition to zoning and other development regulations adopted by the city, and/or other agencies that may have jurisdiction over an area or activity. In the event of an irreconcilable conflict between these regulations and any other regulations of the city, the regulations that provide greater protection for critical areas shall apply.
C. 
Compliance with the provisions of this chapter does not necessarily constitute compliance with other federal, state, and local regulations and permit requirements. The applicant is responsible for complying with all applicable regulations and requirements.
D. 
Areas characterized by a particular critical area may also be subject to other regulations established by this chapter due to the overlap or multiple functions of some critical areas. Any individual critical area adjoined by another type of critical area shall have the buffer and meet the requirements that provide the most protection to the critical areas involved.
E. 
The provisions of this chapter shall be minimum requirements in their interpretation and application and shall be liberally construed to serve the purposes of this chapter.
(Ord. 2004-603 § 2; Ord. 2026-945 § 2 (Att. A))
On-site density transfers are permitted for critical area buffers and Category IV wetlands. The density may be transferred to the noncritical area/buffer portion of the site, (a) subject to applicable policies, setbacks and other standards of the city, (b) if it is compatible with the character of the area and adjacent uses, and (c) the area to which density is transferred is not constrained by other critical areas.
(Ord. 2004-603 § 2)