Critical Area – Area Requiring Protection – Operations

Introduction

A critical area is a land or water zone that requires special protection because of its environmental, geological, or hydrological significance. The concept is fundamental in Washington State land use and environmental law, where statutes and local ordinances mandate identification, classification, and stewardship of these sensitive areas. The primary goal is to preserve vital ecosystem functions, minimize risks to public health and safety, and support sustainable development.

Typical critical areas, as defined in the Revised Code of Washington (RCW 36.70A.030) and municipal codes, include:

• Wetlands (natural or restored)
• Critical aquifer recharge areas
• Frequently flooded areas (100-year floodplains)
• Geologically hazardous areas (landslide, seismic, or erosion-prone)
• Fish and wildlife habitat conservation areas

Their boundaries are determined using best available science—such as site surveys, soil and hydrological analysis, and mapping—and codified in local ordinances. Management of operations in or near critical areas is governed by a robust regulatory framework, requiring site-specific assessments, adaptive management, and ongoing monitoring.

Key Concepts and Definitions

Adaptive Management

Adaptive management is a process that allows for ongoing improvement of critical area protection strategies. It involves implementing actions, monitoring outcomes, and refining approaches based on what works best, ensuring policies remain responsive to new scientific findings and changing environmental conditions. This is especially important for dynamic systems like wetlands and floodplains, where unforeseen impacts may require regulatory adjustment.

Reference: RCW 36.70A.172; WAC 365-195-900 through 925

Adjacent

An adjacent area is land or water lying directly next to a critical area, or within a defined distance (often specified in feet or meters in local ordinances). Activities in adjacent areas can influence the health and function of the critical area, which is why regulatory buffers are commonly imposed.

Reference: RCW 36.70A.030(5); Prosser Municipal Code 16.10.010

Advance Mitigation

Advance mitigation means that compensatory actions (such as wetland restoration) are completed before the environmental impacts of a project occur. This helps ensure that ecological functions are maintained with minimal temporal loss, and can expedite permitting.

Reference: 33 CFR Part 332; RCW 36.70A.172

Alteration

Alteration refers to any human-induced change to a critical area or its buffer, whether intentional or incidental. Examples include grading, filling, excavation, vegetation removal, or hydrologic modification. Permits are required for most alterations to ensure that impacts are avoided, minimized, or mitigated.

Reference: WAC 365-190-080; Prosser Municipal Code 16.10.010

Anadromous Fish

Anadromous fish are species that hatch in freshwater, migrate to saltwater to mature, and return to freshwater to spawn (e.g., salmon, steelhead). Their presence often triggers stricter protections for streams and riparian zones.

Reference: Endangered Species Act (ESA); Washington Hydraulic Code

Applicant

The applicant is the person or entity (landowner, developer, agency) seeking approval for a project that could affect a critical area. The applicant is responsible for submitting required documents, such as site plans and critical area reports, and for complying with all relevant regulations.

Reference: Prosser Municipal Code 16.10.010; WAC 365-190-080

Aquifer

An aquifer is a subsurface layer of rock or sediment capable of storing and transmitting groundwater. Aquifers are classified as confined (protected by impermeable layers) or unconfined (directly recharged from the surface), and are vital for drinking water supply.

Reference: Safe Drinking Water Act; RCW 36.70A.030(5)

Aquifer Recharge Area

A recharge area is land where water infiltrates to replenish an underlying aquifer. Protecting these zones maintains groundwater supplies and prevents contamination.

Reference: WAC 365-190-080(2); Safe Drinking Water Act, Section 1424(e)

Confined Aquifer

A confined aquifer is bounded by layers of impermeable material, resulting in groundwater under pressure. These aquifers are less vulnerable to surface contamination.

Reference: Safe Drinking Water Act

Sole Source Aquifer

A sole source aquifer provides at least 50% of a region’s drinking water. EPA designation triggers additional federal review for projects that could threaten water quality.

Reference: Safe Drinking Water Act, Section 1424(e)

Aquifer Susceptibility

This is a measure of how easily contaminants can reach an aquifer from the surface. High-susceptibility areas require more stringent land use controls.

Reference: WAC 365-190-080

Unconfined Aquifer

An unconfined aquifer is not protected by an overlying impermeable layer and is directly recharged by surface water, making it more susceptible to contamination.

Regulatory Framework and Operations

Statutory and Code References

• Growth Management Act (RCW 36.70A): Requires local governments to identify and protect critical areas using best available science.
• Washington Administrative Code (WAC 365-190, 365-195): Provides technical guidelines for classifying and managing critical areas.
• Municipal Codes: Cities and counties adopt ordinances (e.g., Prosser Municipal Code 16.10) that specify procedures, buffer widths, and mitigation requirements.
• Federal Laws: The Clean Water Act, Safe Drinking Water Act, and Endangered Species Act play key roles, particularly for wetlands, waters, and listed species.

Identification and Classification

• Site Assessment: Qualified professionals perform field surveys, mapping, and analysis.
• Critical Area Report: Required documentation includes delineation maps, impact assessment, and mitigation plans.
• Public Notice and Review: Neighboring landowners and agencies may be notified, and public comment may be solicited.

Permitting and Compliance

• Avoidance and Minimization: Projects must avoid critical areas where feasible; otherwise, impacts must be minimized and mitigated.
• Buffer Requirements: Defined zones of undisturbed vegetation or restricted activity adjacent to the critical area.
• Mitigation: May include on-site restoration, off-site compensation, or use of mitigation banks.
• Monitoring and Maintenance: Long-term monitoring ensures that mitigation measures are successful and that ecological functions are maintained or restored.

Best Practices for Operations in Critical Areas

• Early Consultation: Engage with local planning departments and environmental professionals early in project design.
• Use Qualified Experts: Hire certified wetland scientists, hydrogeologists, or biologists as appropriate.
• Document Thoroughly: Maintain complete records of site assessments, permit applications, and monitoring.
• Adaptive Management: Be prepared to adjust operations or mitigation strategies if monitoring reveals unforeseen impacts.
• Community Engagement: Inform and involve stakeholders, particularly when projects are near sensitive habitats or drinking water sources.

Conclusion

Critical areas are integral to the health and resilience of Washington State’s natural and built environments. Their identification and protection are required by law and supported by a wealth of technical guidance. Compliance ensures not only environmental stewardship, but also reduces legal and financial risks for landowners, developers, and agencies.

Expert support is available for navigating complex permitting, planning, and compliance requirements—contact our team for help with site assessments, mitigation planning, and regulatory strategy.