Excavation Before Septic Installation

Where excavation fits in the county's process

Flathead County's own permitting checklist spells out the division of labor: the owner hires an excavator to dig test holes so soils, groundwater, and bedrock can be analyzed, the sanitarian observes those pits being dug, and the county then produces the Site Evaluation and Design Report. The soil profile is examined to a depth of eight feet — a real excavation, not a posthole.

That's the front of the project. At the back, site preparation — access, clearing over the drainfield area, rough grading — is excavation work again. The system construction in between belongs to a Flathead County licensed installer, full stop.

Groundwater monitoring sets the schedule

The Flathead Valley's high water table changed the rules here: groundwater monitoring has replaced the percolation test as the way drainfield suitability is determined. If the county requires monitoring, a pipe goes into the test hole and is read through the following spring when groundwater peaks — meaning a project evaluated in summer may not permit until the next year. Owners planning a build should dig test pits as early in the property's life as possible, precisely because of this timeline.

The setbacks that decide where pits get dug

Test pits go where the drainfield could actually be, so the county's setback table drives the dig locations:

• 100 feet from any well to the drainfield (50 feet from a private well to the tank).
• 100 feet from surface water, measured horizontally from the high water mark.
• 100 feet from the 100-year floodplain — often the binding constraint on river parcels.
• 4 feet of vertical separation between the drainfield's infiltrative surface and seasonal high groundwater, bedrock, or an impermeable layer.
• Water-related drainfield setbacks are non-waivable — the county says so explicitly.

What Boaz does and doesn't do here

Plainly: Boaz digs evaluation test pits, clears and preps drainfield and tank areas, cuts access, and handles the grading around a septic project. Boaz does not construct, alter, or repair the system itself — Flathead County law reserves that for licensed installers, and the county's final inspection happens before anything is backfilled. The value of one contractor doing the dirt work at both ends is coordination: pits dug when the sanitarian is scheduled, site prepped when the installer is ready, and grading closed out after inspection instead of weeks later.