Sourced from OAR chapter 340 divisions 071 and 073 as amended effective January 1, 2026 (including OAR 340-071-0130 and 340-071-0400), ORS 454.755, and published county fee schedules — last checked August 2026.
What the evaluation is actually deciding
An evaluator examines the soil profile, depth to groundwater or bedrock, slope, drainage and available area. The question is not simply pass or fail. It is which of several system types your site can support, and the answer moves your project cost substantially.
A site that takes a standard gravity system and a site that needs a sand filter or an advanced treatment unit are different projects. The county fee schedules show the gap plainly: in every schedule we retrieved, the sand filter permit costs roughly double the standard system permit — and that is only the paperwork, before the difference in the system itself.
The 90-day re-inspection entitlement
If your evaluation does not go the way you hoped — a test pit in the wrong place, a wet season reading, an area you had not offered for consideration — you have already paid for further inspections, provided they happen inside 90 days. The clock runs from the first inspection, not from the decision. Raise it with the agent immediately rather than waiting for better weather.
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What it costs
| Office | Site evaluation | Schedule dated |
|---|---|---|
| North Central Public Health (Sherman, Wasco) | $913 | FY2026–27 |
| Marion County | $1,098 | July 1, 2026 |
| Washington County | $1,184 | expired June 30, 2026 |
| Deschutes County | $1,264 | FY2026 |
| Clackamas County | $1,696 | undated |
| Multnomah County (via Portland) | $2,198 | July 10, 2026 |
Add the statewide DEQ surcharge of $159 for applications on or after July 1, 2026. Full detail on the fees page, including the counties whose schedules we could not obtain.
If the agent asks for more than the minimum
Under OAR 340-071-0130(1), if the agent judges the minimum standards inadequate for your particular site, they must require something more protective — and they “must provide the applicant with a written statement of the specific reasons why more stringent requirements are necessary.”
This is per-site discretion, not a county rule. Two neighboring properties can be treated differently, and the written statement is how you find out why yours was. Request it in writing and keep it. It explains your cost, and if you disagree it is the document any challenge would start from.
Six places in Oregon where extra rules apply
OAR 340-071-0400 names six specific geographic areas with their own requirements. If your property is in one, your evaluation is working to a different standard and you should expect it.
| Area | What is different |
|---|---|
| River Road–Santa Clara, Lane County | A system may not contribute more than 16.7 lb of nitrate-nitrogen per acre per year |
| North Florence Dunal Aquifer, Lane County | 58 lb per year per acre owned or controlled by the applicant; the Clear Lake watershed is excluded by metes and bounds |
| Alsea Dunal Aquifer | Turns on whether the lot was a lot of record before January 1, 1981. Pre-1981 lots get options unavailable elsewhere, including bottomless sand filters at one foot of separation |
| Christmas Valley Townsite, Lake County | Shallow groundwater may be treated “in the same manner as a temporary water table” — a reclassification that makes one platted townsite buildable |
| Clatsop Plains Aquifer, Clatsop County | The rule incorporates a private consultant’s report as the governing standard |
| East of the Cascades, 20 inches of rainfall or less | A standard system is allowed on 10 acres or more — and on 80 acres or more the site evaluation can be waived entirely with a quarter-mile separation. The only route in Oregon to a permitted system with no site evaluation |
These six are the complete list in 0400. “Groundwater limited area” and “geographic area of special concern” are not Oregon terms — if you have read them on another site, they were borrowed from a different state. Oregon’s separate Groundwater Management Areas under ORS 468B.175–188 number three (Northern Malheur, Lower Umatilla Basin, Southern Willamette Valley), and a Groundwater Management Area declaration imposes no direct duty on septic owners.
Setbacks, and the one that can be halved
Separation distances are part of what the evaluation measures — how far your drainfield must sit from wells, surface water, property lines and structures. They are set statewide, so they do not change between counties.
The standard separation between a drainfield and a well is 100 feet. That is the number most people know, and for most properties it is the binding constraint on where a system can go.
On a constrained lot that single provision can be the difference between a permitted system and no system at all — or between a standard drainfield and an expensive engineered alternative. If your evaluation fails on well separation, ask specifically about the special-standards well construction before accepting that the site will not work.
We are not reproducing the full setback table here. Distances vary by feature and by system type, and the version we can machine-read reliably does not extend to every row — publishing a partial table as though it were complete would be worse than pointing you at your agent, who works from the current one.
Book an evaluation and get a realistic quote
The evaluation goes through your county’s agent. For the work that follows, we can connect you with licensed local installers at no cost.
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Frequently Asked Questions
What is a septic site evaluation in Oregon?
An examination of soil profile, depth to groundwater or bedrock, slope, drainage and available area, to decide whether your property can support an onsite system and which type. It is not simply pass or fail — the system type it permits largely sets your project cost.
How much does a site evaluation cost in Oregon?
From about $913 at North Central Public Health to $2,198 in Multnomah County, plus the statewide DEQ surcharge of $159 for applications on or after July 1, 2026. Fees are set county by county.
What if my site evaluation fails?
Under ORS 454.755(2) your fee entitles you to as many site inspections as necessary within 90 days of the first one, so you may be able to have further inspections without paying again. Ask the agent inside that 90-day window.
How close can a drainfield be to a well in Oregon?
The standard separation is 100 feet. A footnote to the setback table provides that a well constructed to Water Resources Department special standards reduces the required drainfield separation to 50 feet — which on a constrained lot can be the difference between a permitted system and none.