The Spokane Valley – Rathdrum Prairie Aquifer Atlas

T H E S P O K A N E VA L L E Y – R AT H D R U M P R A I R I E

Aquifer Atlas

EDITION

Welcome!

Welcome to the 2022 edition of the Spokane Valley – Rathdrum Prairie (SVRP) Aquifer Atlas. The original SVRP Aquifer Atlas was published in 2000 and updates were issued in 2004, 2009 and 2015.

As in past versions of this atlas, the purpose is to present a comprehensive summary of the region’s most precious groundwater resource. The intent is to provide a basic reference of the geographic, geologic, and hydrologic characteristics of this aquifer. It is intended for regional use in education, in planning, and as a source for general technical information.

The SVRP aquifer spans two states, Washington and Idaho.

Natural resources that cross political boundaries are often subject to different and sometimes conflicting standards, protections, and uses. All SVRP Aquifer Atlas editions are a joint effort by agencies in both states to create a holistic representation of the SVRP aquifer as both a geologic feature and a natural resource used daily by more than half a million people.

Political boundaries and objects made by people are absent from the front cover map to show the aquifer as a natural feature. The SVRP aquifer area is not blue to differentiate the aquifer area from surface water bodies. The authors’ goal in this SVRP Aquifer Atlas edition is to include issues that are currently facing our region.

Our hope is to educate the public, and through greater understanding of this precious resource, to become good stewards who will protect and preserve this finite aquifer.

What’s new?!

Many new issues face our region since the 2015 edition of the SVRP Aquifer Atlas. These issues have been the subject of media reports and the source of much public discussion.

These issues include the amount of interaction between the Spokane River and the SVRP aquifer, stormwater and wastewater discharge to the river and minimum flow rates of the Spokane River in late summer and fall. These interactions have the ability to impact the water quantity and quality of the SVRP aquifer and the Spokane River. These issues have also raised public concerns related to the health of the fi sheries and general aquaculture of the Spokane River.

It is not the authors’ intent to describe or suggest potential solutions regarding the issues of the region in this publication but to provide a tool to educate the public allowing constructive and productive dialogue for future solutions.

T H E S P O K A N E VA L L E Y – R AT H D R U M P R A I R I E AQ U I F E R AT L A S

Contents Introduction

2 5 5 5 6 7 9 11 12 13 14 15 16 17 18 19 20 21 22 23 25 27 28

Introduction.....................................................................................

Geology...............................................................................................

Geology

Geologic Map................................................................................

Geology...............................................................................................

Ice Age Floods..............................................................................

History | Culture

SVRP Aquifer Timeline..........................................................

History of Water Use...............................................................

Hydrogeology............................................................................

Aquifer-River Interchange.............................................

Details

Water Cycle................................................................................

Water Budget.............................................................................

Water Use.....................................................................................

Future Water Use..................................................................

SVRP Aquifer Monitoring................................................

SVRP Aquifer Monitoring...............................................

Storm Drains & The Aquifer.........................................

Protection | Stewardship

Stormwater Swales & The Aquifer.........................

75 Years of Sewer.................................................................

Sewering Effects...................................................................

Aquifer Protection - Business...................................

Aquifer Protection - Home............................................

General reference

SVRP Aquifer Tour................................................................

Acknowledgements............................................................

T H E S P O K A N E VA L L E Y – R AT H D R U M P R A I R I E AQ U I F E R AT L A S

PAG E 1

Introduction The Water Beneath Us

The sole source of water for most people

in Spokane County, Washington, and Kootenai County, Idaho, is a large deposit of gravel, cobbles, and boulders containing high-quality water called the Spokane Valley – Rathdrum Prairie (SVRP) aquifer, also commonly known as the “Rathdrum-Spokane aquifer.”

Discovered in 1895, this aquifer has become one of the most important resources in the region, supplying drinking water to more than 500,000 people. The SVRP aquifer has been studied in considerable detail since 1977, and the results of these investigations have produced programs and regulations designed to ensure this aquifer will remain a valued and protected resource for future generations.

The geology and hydrogeology of the Spokane Valley and Rathdrum Prairie have, over millions of years, been formed by various geologic events and shaped by water flowing from the western slopes of the Rocky Mountains to the Pacifi c Ocean. During the last Glacial Age (18,000 to 12,000 years ago), and possibly in multiple previous Ice Ages, cataclysmic floods inundated northern Idaho and Washington as a result of the rapid draining of Glacial Lake Missoula when ice dams broke (see pages 5 and 6). These floods deposited thick layers of gravels, cobbles, and boulders that form the aquifer of today.

Water from adjacent lakes, mountain streams, the Spokane River, and precipitation flows through these flood deposits supplying the SVRP aquifer.

In the 1970s area residents recognized that their unconfined aquifer could easily become contaminated. The highly permeable flood deposits, together with very thin topsoil layers in many locations, make the SVRP aquifer highly susceptible to pollution. Area residents took the fi rst important step to protect the SVRP aquifer by petitioning the US Environmental Protection Agency (EPA) to designate the SVRP aquifer as a “sole source aquifer”. The EPA agreed and granted this designation in 1978. It was the second aquifer in the nation to receive this special designation.

The sole source designation increased public awareness for SVRP aquifer and supported the development of special management practices (such as eliminating septic systems and pretreating stormwater over the SVRP aquifer) by local agencies. Presently, SVRP aquifer protection efforts are managed cooperatively by Spokane County, local cities, the Department of Ecology and utilities in Washington, and by the Department of Environmental Quality, Panhandle Health District, and local cities and counties in Idaho.

PAG E 2

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T H E S P O K A N E VA L L E Y – R AT H D R U M P R A I R I E AQ U I F E R AT L A S

PAG E 3

INTRODUCTION CONTINUED

THAT CITY WATER Had the right thing

SPOKANE’S WATER PUREST IN WORLD City bacteriologist Frank Rose reports results No Colon Bacilli Found

[E. V. Van Osdel, the city chemist:] “It was said that when the workmen were digging the channel above the water works [in 1895] at a point 50 feet above the power house they encountered the water in larger quantities than it could be pumped out. If that is so, why didn’t they stop there, and we would have had good fi ltered water”

Showing the Spokane water supply purer than the average of American cities, Frank Rose, city bacteriologist, has made a report of tests from the city well made monthly since last October.

The tests are simply counts of the number of bacteria found in a cubic centimeter of water.

The average count shows only seven or eight germs in that amount of water. The test was made from water taken from the drinking fountain at Howard street and Riverside avenue or from water from a faucet in the Rookery building. Speaking of his tests, Dr. Rose said: “It can be said that there is no city in the world that has a better water supply than Spokane. Water which shows 100 germs in a cubic centimeter is considered comparatively pure and drinkable. I made from four to eight counts monthly since last October, and the counts in any one month was 17 bacteria, while the tests last month showed 15 bacteria in eight tests, less than two each.”

MAY 6, 1909

Spokesman-Review

PAG E 4

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OCTOBER 17, 1898

Spokane Daily Chronicle

Geology

T H E S P O K A N E VA L L E Y – R AT H D R U M P R A I R I E AQ U I F E R AT L A S

PAG E 5

GEOLOGY CONTINUED

PAG E 6

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T H E S P O K A N E VA L L E Y – R AT H D R U M P R A I R I E AQ U I F E R AT L A S

PAG E 7