A septic system is only as good as the hole it sits in. We dig the test holes, tank pit and drainfield trenches or bed to the depth, slope and layout your permit calls for, then backfill and grade the site.
Septic System Excavation in the Treasure Valley
Septic work has a lot of moving parts: a health district, a designer, a tank, a drainfield and the digging that ties them together. Some owners hire one company to do everything. Others bring in a designer or installer and want a good excavator for the dirt work. This page is for the second group, though we're glad to talk through either.
We dig septic excavations around Boise, Kuna, Star, Middleton, Nampa, Caldwell, Parma and Homedale. If you'd like us to install the system as well, see our septic system installation page.
Test Holes for the Site Evaluation
Before a system gets designed, the health district needs to see the soil. We dig test holes, sometimes called soil pits, where the drainfield is planned. That lets the evaluator check soil layers and how deep groundwater sits. Holes are cut so they can be looked at safely from the surface, and we mark and close them up afterward.
The Tank Excavation
The tank hole has to match the permit for depth and location. We check the staked layout against the permit's setbacks from the well, the house and the property lines before we dig. The bottom is dug level and clean so the tank sits evenly, and any soft spot gets dug out and replaced with compacted base. Caliche or rock in the hole adds time, and we'll tell you if we hit either. See our rock excavation page for how that's handled.
Drainfield Trenches and Beds
Drainfields are either trenches or a wide bed, depending on the design. The depth, width and slope all come from the permit. We keep our machines off the area where possible, since driving on it packs the soil that has to drain. Where the soil is wet or the lot is tight, we work from the edge and plan the digging to avoid running back and forth across it.
Some lots need a raised system, like a sand mound, because the groundwater is high or the soil drains poorly. That means stripping and preparing the ground, then bringing in sand and building up the mound to the designer's drawings. It's a bigger job, so it helps to know early.
Pipe Runs Between the House, Tank and Field
The line from the house to the tank, and from the tank to the drainfield, needs steady fall. We dig these trenches to the grade shown on the plan, and we bed the pipe so it doesn't settle. Where the line crosses a driveway, a ditch or a utility, we plan the crossing before we dig. Our utility excavation page covers other lines on the lot.
Excavating Around an Existing System
Not every septic job is a new one. We dig down to existing tanks to set risers, replace lids or expose a tank for service. We can also dig out an old tank that's being replaced or abandoned. Rules apply to taking a tank out of service, so check with the health district about what it requires. If your system is failing, see our septic repair page.
Inspections and Backfill
The health district inspects before anything gets covered. We plan the digging so the open excavation doesn't sit longer than it has to, and we leave everything open until the inspector has signed off. Then we backfill in layers and grade the site so water runs away from the tank and the field. Drainfield cover is not packed like a driveway, since the soil needs to drain. We leave the area ready for seed.
Digging Septic Excavations Safely
Open holes are a hazard for kids, pets and anyone walking through at night. We keep the excavation open for as short a time as we can, and we'll talk with you about fencing or marking it if it has to sit overnight. Deeper pits get sloped sides so the walls stay put.
Why Call Ultimate Excavation LLC
We're an Idaho registered contractor (RCE-65836) based in Caldwell, with a 5.0 rating on Google. Call (208) 697-2429 or request a free estimate. Send us your permit or site evaluation if you have it, and we'll price the dig from there.
