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A Guide for Home Builders

Thurston County Application-Review Processapplication review

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Zoning Review

Your site plan will be reviewed to make sure that it meets all zoning requirements. Your building site must be in a zone that allows the proposed residential structure. The site plan also must meet building set-back requirements that specify the distance of the proposed home from the property lines. A county reviewer also will check to see if the building site is within 500 feet of any lands designated for long-term agriculture, long-term forestry or mining. You will be notified if your property is near any of these resource lands. Before receiving a building permit, applicants must sign a Resource Notification form. This form states that you are aware of possible negative impacts to your property resulting from the activities allowed on these resource lands.

Critical area review

Critical areas include shorelines, flood plains, streams, wetlands, important wildlife habitat areas, frequently flooded areas, special aquifer recharge areas and geologically hazardous areas (such as steep slopes and marine bluffs). If the initial review of your application shows a critical area on your property, an environmental planner will review your site plan and application. The planner may need to visit your site (please have all flags in place) to decide whether a buffer zone is required between the critical area and any proposed structures. You will be notified if your property includes a critical area and if a buffer is required.

Site Visit and Soils Evaluation

A county environmental health specialist will visit your building site to do a soils evaluation. Typically, your sewage system designer will need to dig two test holes in the proposed primary drainfield area and one hole in the proposed reserve drainfield area before the inspection. The holes should be at least 6 feet deep (unless the water table or a restrictive layer are shallower than 6 feet), at least 2 feet wide, and sloped to allow access into the hole. The designer should clearly flag each hole.

Other county reviewers may verify other information that you or your agent submitted as part of your site plan. They may check major topographic features, vegetation coverage, location of critical areas (shorelines, flood plains, wetlands, steep slopes, etc.), and proposed access to the site. To help the reviewers find your lot and compare your site plan with the actual site, please make sure that you clearly flag the property corners and the location of proposed access point(s) to the project site.

On-Site Sewage (Septic) System Design Review

Washington State and Thurston County codes require each residence to have a functioning approved on-site sewage (septic) system for treating and disposing of human waste and waste-water. A poorly designed or failing system may allow sewage to leak into your water supply or contaminate nearby wells, streams, lakes or underlying ground water. Most Thurston County single-residence sewage systems include a septic tank and drainfield, professionally designed to meet minimum state and local regulations for preventing pollution.

Your sewage system designer usually will submit detailed information about the soils, topography, critical setbacks and elevations at your site. The design will include calculations to find the appropriate size for your system based on the number of bedrooms in the proposed home. Environmental Health will check this design information for compliance with state and local regulations and technical requirements.

The environmental health specialist will tell you and your designer if any changes to the initial sewage system design are necessary. Your designer is responsible for submitting revised design information to Thurston County Environmental Health.

When your on-site sewage (septic) system design has been approved, the reviewer will notify your case manager in the Building Development Center. The case manager will add this approval to your project file. You will receive a Conditional Site Approval letter approving an on-site sewage (septic) system design for your property and establishing written conditions for further site development.

After meeting any requirements explained in the Conditional Site Approval letter and paying the permit fee, you will receive an On-site Sewage (Septic) Installation Permit to construct your system. When the system is installed, the sewage system designer must call Thurston County Environmental Health for a final inspection and submit “as-built” drawings (drawings that show how your system is actually constructed).

After Environmental Health accepts the as-built drawings, you will receive an Operational Certificate with conditions for ongoing operation and maintenance of your system. You may now begin using the system. You must follow the conditions listed in your certificate to stay in compliance. Most Operational Certificates must be renewed every four years or before the expiration date.

If your building site is served by a public sewer system...

To meet sewage disposal requirements, obtain the signature of the sewer provider confirming the availability of sanitary sewer prior to applying for your building 0ermit. The project application for your building permit has a space provided for this signature.

Drinking Water Review

Washington state law requires the assurance of an adequate supply of drinking water prior to the issuance of a Building Permit. If you are proposing a single-family or two-party water source for your new home, complete a single-family Certificate of Water Availability form. If you are proposing connection to a water source serving more than two homes (public water system), obtain the signature from the water provider confirming assignment of a service connection prior to applying for your Building Permit. The project application for your Building Permit has a space provided for this signature. Requirements for approval of each type are as follows:

  • Connection to single-family or two-party source: (Additional standards apply to springs and surface-water sources.)
  • Completed Certificate of Water Availability.
  • Well site approval - Drawings of your well site must be included on your site plan and are approved during the site-plan review process.
  • Well driller’s report - This report, also commonly called a “well log,” provides details about how your well is constructed.
  • Water right permit (if required) - This permit is required if you will be drawing from a surface-water source. It also may be required if you will use the water for irrigation purposes.
  • Access easement (if required) - An easement is required if you must cross public right of way or another person’s property to access your well, or if your well is on another person’s property.
  • Isolation covenant (two-party well only) - This form gives property owners the legal ability to control activities within 100 feet of their well that could affect their water quality.
  • Quantity test (pump test, air test, bailer test) - Your quantity test must demonstrate a minimum 400-gallon-per-day flow for single-family wells and a minimum 800-gallon-per-day flow for two-party wells.
  • Satisfactory bacteria and nitrate tests -These water quality tests ensure that your water meets drinking-water standards. If your building site is in a known or suspected contamination area, additional water quality tests may be required.
  • No contamination source within 100 feet of the well

If Connecting to a Public Water System...

Provide the signature of the water provider on the project application for a building permit. The signature confirms assignment of a service connection. Local or state health officials will review your application to make sure that the proposed water system complies with all applicable laws and standards.

Public Right of Way Access Review

Thurston County Public Works reviews all proposals for new driveway access to county roads and unopened county right of way, and issues Encroachment Permits. A county engineering technician will review your access proposal based on the following safety requirements:

  • Sight distance - Drivers and pedestrians entering and exiting your property must be able to see oncoming vehicles from a safe distance. This distance increases proportionately to traffic speeds.
  • Intersections - Access must be constructed at a minimum distance from any intersection. Again the safe distance is determined based on traffic volumes and speed.
  • Drainage - Frequently the proposed access route will cross a roadside drainage ditch. A county engineering technician will decide if a culvert is needed to maintain proper drainage and will notify you of any installation requirements. When your access proposal has been approved, the reviewer will prepare an Encroachment Permit and notify your case manager in the Permit Assistance Center. The case manager will add this approval to your project file. You must purchase the Encroachment Permit before constructing the driveway.

When your access proposal has been approved, the reviewer will prepare an Encroachment Permit and notify your case manager in the Permit Assistance Center. The case manager will add this approval to your project file. You must purchase the Encroachment Permit before constructing the driveway.

Stormwater Treatment and Erosion Control Review

Thurston County Public Works also reviews all site plans to make sure that they meet storm-water treatment and erosion control requirements. It is against the law to direct storm-water from your site onto a neighboring property or county right of way. During construction, the county also requires measures to prevent soil erosion caused by rainfall on the exposed building site. Thurston County allows several methods for handling residential storm-water. Your project site plan must include your proposal for storm-water treatment and erosion control.

Building Plan Review

A certified plans examiner in the Community Planning & Economic Department will review your site plan, construction drawings, specifications and other information related to your project for compliance with the state Building Code and other construction and operation regulations. The examiner will point out any changes required to comply with state and local code. When these changes are made, the plans examiner will approve your drawings. Additional code-related information may be attached to your approved plans for easy reference during construction. If you have any questions about specific code requirements for residential construction, please contact the Building Development Center.


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