Septic Tank & Drainfield Digs in Vancouver, WA

Septic tank and drainfield digs are the excavation for onsite sewage systems on properties outside sewer service. Much of rural Clark County, from Brush Prairie and Hockinson to Yacolt and Amboy, relies on septic. We dig test pits for soil evaluation, excavate tank holes and drainfield trenches to the approved design, and backfill after inspection.

Soil changes everything

A septic drainfield depends on soil that accepts water at the right rate. Very gravelly soils, like the Lauren and Sifton series mapped around Vancouver, take water fast, sometimes too fast for treatment. Clay soils on the high terraces, like the Hesson series with 35 to 50 percent clay, take it slowly. Seasonal wet conditions in winter matter too. The designer and health department use the test pits to choose the right system.

Who designs it

Systems are designed by licensed designers or engineers and approved by the health department before installation. We do not design systems; we excavate to the approved plan and coordinate with the installer.

Costs

HomeAdvisor puts a typical new septic system at $3,590 to $12,463, with conventional systems at $3,000 to $8,000 and mound systems at $10,000 to $20,000. Drainfields run $5,000 to $12,000. Excavation contractors on a septic job are listed at $1,500 to $6,300.

Wet-season limits

Working drainfield trenches in saturated soil smears the trench walls and can reduce absorption. Drainfield installation is best done when the soil is dry enough, and we schedule accordingly.

Replacements and repairs

Older systems fail as drainfields clog or tanks deteriorate. We excavate for replacement fields, dig up tanks and lids, and decommission old tanks as required.

Protecting the drainfield area

Before and after installation, the drainfield area should stay free of vehicles, stockpiles and grading. Compaction ruins the soil's ability to absorb water. We fence it off during construction and plan access routes around it.

Access for pumping

Risers and lids at grade make routine pumping easier and cheaper. We can add them during installation or dig up existing tanks to install them.

Test pit timing

Soil evaluations often need to show seasonal wetness, so test pits may be scheduled for the wet season even though installation happens later in the dry months. We dig them when the designer needs them.

Abandoning old systems

When a property connects to public sewer, the old tank must be pumped and decommissioned as required. We do the excavation and fill.