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On-site sewage design application, process flow, and directions
Learn how a licensed on-site sewage system designer can submit a design application online.
You must complete an application in its entirety. Make sure that you have all the necessary information and application documents before you start an application. You can review:
Application document checklist
| No. | Type of document | Additional instructions | Conditions that initiate requirement |
|---|---|---|---|
| 1 | Vicinity Map | Must include gate code, presence of dogs, and details needed for the inspector to locate the proposed/existing well and on-site sewage system site | Required for all applications |
| 2 |
Detailed Site Plans and specifications |
Maximum paper size is 11” x 17” (Detailed site plan: 1” to 20’ or the largest scale that will allow; Overall site plan may be scaled as needed for example, 1” to 50’ or 100’; Sewage Tank Invert & Plumbing Stub Elevations; and Details of proposal per Title 13 Code requirements – remember to check neighboring properties for wells, on-site sewage system, and storm water systems |
Required for all applications |
| 3 |
Hydraulic Calculations |
Should include clear calculations, preferably on a single page |
Required for all applications |
| 4 |
Soil Log Data |
Minimum of 5 soil logs - 2 each drain field & reserve area + 1 for tank(s) (Remember to document the soil log for the septic tank). If a treatment device, such as a sand filter or ATU unit, is greater than thirty feet from the wastewater tanks, then one soil log shall be located in the area of the treatment device. |
Required for all applications |
| 5 |
Treatment Product Specifications |
Document only what is needed for design and installation – documentation that is available in the design manual does not need to be included |
Required for all applications |
| 6 |
Critical Area Designation |
Required for new on-site sewage design | |
| 7 | Sewer Letter |
Sewer letter should state what the distance from property line to nearest sewer is greater or less than 200 feet |
Required for on-site sewage system in urban area |
| 8 |
Valid (one year) water Availability Letter |
Required if property is in public water system area | |
| 9 |
Current Bacteria test |
If Applicable | |
| 10 |
Nitrate test and Arsenic Result |
If Applicable | |
| 11 |
Draft well covenant(s) |
Required if water source is “Proposed Private Individual Well” | |
| 12 | Copies of covenants | Required if water source is “Existing Private Individual Well” | |
| 13 | Proof of lot segregation date |
Required if water source is “Proposed Private Individual Well” and property is less than 5 acres. Or If Drainfield Easement |
|
| 14 | Well construction log | Required if water source is “Existing Private Individual Well” | |
| 15 | Easement survey | If Applicable | |
| 16 | Draft Drainfield easement language | Required If Drainfield Easement | |
| 17 | Draft easement language | If Applicable | |
| 18 | Other_1 | Optional for any type of applications | |
| 19 | Other_2 | Optional for any type of applications |
Instructions for submitting on-site design application
- Go to Environmental Health's online services portal.
- If you are a new user, click on "First-time users register here".
- If you previously created an account, click on "Registered users log in here".
- Once you are logged in, from the left side menu, click on "OSS plan review".
- Click on "Add OSS Plan Review" and complete the application process and attach your application document.
- After you have completed the application and paid your fee, you will be able to print the application for your records, you will receive a confirmation email, and you can check the status of your application at www.kingcounty.gov/oss/status