Radon Mitigation in Hillyard and Northeast Spokane

Hillyard sits over the Hillyard Trough, a deep, sediment-filled arm of the Spokane aquifer under northeast Spokane. Its fill is finer than the Spokane Valley's boulder gravel, yet the state's test records here are among the highest in Spokane: in 8 of 10 census tracts within ZIPs 99207 and 99217, half or more of tests reached 4.0 pCi/L.

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48-hour test from $195 · Systems from $1,295 · Post-mitigation test included

How it works in Hillyard

1. STEP 1
   Test

   A 48-hour continuous monitor in your lowest living level, under closed-house conditions. Report the same day it comes out.

2. STEP 2
   Look and quote

   We check the foundation, run a suction test and plan the pipe route for Hillyard winters. You get a fixed price in writing.

3. STEP 3
   Install

   Most systems take one day: suction point, sealing, fan, manometer and the electrical permit.

4. STEP 4
   Re-test

   A post-mitigation test at least 24 hours after the fan starts shows the new number. The guarantee is below 4.0 pCi/L.

Radon mitigation cost in Hillyard

Sand and gravel in the trough usually let suction reach well under a slab, though silty layers can shorten its reach, so the quote follows a pressure-field test. A house with both a basement and a crawl space can usually run them on one fan. Inside the city, Avista supplies the power that runs it.

Starting prices include the electrical permit and the post-mitigation test. Bold: systems common in Hillyard homes. Estimate your system →

for a typical 60-watt fan running around the clock. Energy charge only, at 2026 residential rates.

A 20-watt fan costs about a third of that, a 90-watt fan half again as much.

Permits and local rules in Hillyard

Hillyard at a glance

Area figures describe the neighborhood, not your home. Only a test tells you your number. Sources are listed at the end of this page.

Finer ground in the Hillyard Trough, high numbers anyway

The Hillyard Trough is an arm of the Spokane Valley–Rathdrum Prairie aquifer. Before the Ice Age floods, the Spokane River probably flowed through it, along the east side of the Five Mile Prairie plateau and then west down today's Little Spokane valley. The trough now holds the aquifer's greatest known thickness: a 780-foot well never reached the bottom of the glacial and flood deposits, and bedrock is estimated at about 860 feet down.

What fills it is finer than the Valley's. USGS describes sand with some gravel, silt and boulders, where the center of the Spokane Valley has coarse, bouldery gravel. Silt and clay beds, probably laid down in glacial Lake Columbia, run through the trough's gravels; the main one averages 215 feet thick. USGS reads that as a slack-water setting, where fine material settled instead of being swept away by the floods.

You might expect finer ground to hold radon back. The test data don't show it. In census tracts within ZIP codes 99207 and 99217, between 34% and 68.3% of reported tests came in at or above 4.0 pCi/L, and 8 of the 10 reach half or more. Across the city's other ZIP codes, fewer than a third of tracts do. Back in 1993, the U.S. Geological Survey flagged the permeable glacial outwash under Spokane and its eastern suburbs as radon ground.

estimated depth to bedrock in the Hillyard Trough, the aquifer's thickest known point⁶

Hillyard questions