GEOLOGY IN LAND USE PLANNING

By

ERNEST R. ARTIM

Prepared cooperatively by the

UNITED STATES GEOLOGICAL SURVEY

DEPARTMENT OF NATURAL RESOURCES

DIVISION OF MINES AND GEOLOGY

INFORMATION CIRCULAR 47

1973

STATE OF WASHINGTON

DEPARTMENT OF NATURAL RESOURCES

BERT L. COLE, Commissioner of Public Lands

DON LEE FRASER, Supervisor

DIVISION OF MINES AND GEOLOGY

VAUGHN E. LIVINGSTON, JR., State Geologist

Information Circular No. 47

GEOLOGY IN LAND USE PLANNING Some Guidelines for the Puget Lowland

By

ERNEST R. ARTIM

Prepared in cooperation with

UNITED ST ATES GEOLOGICAL SURVEY

1973

COVER DRAWING

This dramatic picture shows several houses in the process of being destroyed by a

landslide. The original photograph was furnished by the Oakland Tribune and

appeared in the Association of Engineering Geologists, Special Publication- 1969,

"Urban environmental geology in the San Francisco Bay region, 11 page 73.

ERRATA SHEET

Washington State Division of Mines and Geology Information Circular 47

"Geology and Land Use Planning; Some Guidelines for the Puget Lowland"

Plate r ...... correlation chart--Quaternary deposits of the Puget Lowland

Under Northern Puget Lowland, Geologic Climate Units

Whidbey Glaciation should read---~Whidbey Interglaciation

CONTENTS

Introduction ................................................................ Explanation of terms ......................................................... Geologic setting

Geologic hazards

............................................................

............................................................

1

2 4

8

Land subsidence and settlement • • • . • . . . • . • . • • • • . . • . • • • . • • • . . • • • • • • • • • • • 8

Landslides • • • • . . • . . . . • • . . . . . . . . . • . . . . . . . . • . • . . • • . • • . . . • . . . . . • • • • • • • • 8

Earthquakes • . . • . . . . . . . . . . . . • . . . . . . . . . . . • . • . . . . • . • • • . • . . . . • • • • • • . • • • • 11

Critical resources and land use planning • . • . • • • • • • . . . • • . . • . • • . . • • • • • • • • • • • • • • • • • l 1

How fo use the tabf e • . . . . . • . • . . . . . • . . • • . . . . . . . . . . • . . • . . . . . . . . . . . . . . . . • . • • • • • • 12

Limitations ................................................................. Selected references ..........................................................

ILLUSTRATIONS

14

16

Plate 1. Correlation-Quaternary deposits of the Puget Lowland ............ Page

In envelope

2. Generalized description of engineering properties of Quaternary geologic name units (Puget Lowland) •••••••••••••••• In envelope

Figure 1. Location of Puget Lowland and major population centers · in Washington • . . . . . . . . . . . . . . . . • . • . . . . . . . . . . . . . . . . • . . . . • . . • . • • . • • 3

2. Advance of the Cordillera rt ice sheet • • • • • • • • • • • • • . • • • . • • • • • . • • • • • • • • • • 5

3. Maximum extent of the Cordilleran ice sheet ........................... 6

4. Simplified ii lustration of sedimentation during glaciation of the Puget Lowland • • • . • . . • . • . . . • . • . . . . • • . . . . . • • • . . . . • . . . . • • . • • • • • • 7

5. Location of epicenters and magnitudes of strong-motion earthquakes in southern Puget Lowland area since 1870

6. Index of geologic mapping in the Puget Lowland for use

................ 10

with this report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • • . . . • • 15

III

"Woe unto them that join house to house, that 'lay field to field, tiU there be no place, that thEy nny be pfoced alone in th.e earth."

(Isaiah 5: 8)

GEOLOGY IN LAND USE PLANNING Some Guidelines for the Puget lowland

By

ERNEST R. ARTIM

INTRODUCTION

The State of Washington has a popula­

tion of 3.4 million people, of which 60

percent live in the Puget Lowland on approx­

imately 8 percent of the state 1s land surface

(fig. 1). As in other metropolitan regions of

the United States, increased urbanization is

causing human activity to sprawl over previ­

ously bypassed areas of hazardous geologic

conditions.

Inadequate building and slope designs

and the resulting construction fa i I ures suggest

that planning capabilities are hampered by an

incomplete understanding of the geologic

environment. Municipal and county govern­

ments, critically in need of detailed urban

geologic mops and information, have seldom

established direct sources for geologic guid­

ance, much less employ a staff geologist.

Thus, the application of geology to planning

and local affairs is often a do-it-yourself

operation, with planners and local authorities

not utilizing any ge~logic knowledge, or else

trying to apply highly technical research-type

geologic mapping to purposes for which it was

never intended. Unfortunately, the present

geologic maps, with very few exceptions,

have been basic data-gathering efforts of a

research nature. Emphasis has been primarily

on the age and history of the various geologic

units rather than on how the units would per­

form under a given land use. Some of the

engineering properties of geologic units to

various land use applications can be estimated

in retrospect merely by becoming acquainted

with the basic units; however, this is no sub­

stitute for remapping. The State of Washing­

ton has begun a more detailed environmental

geologic mapping of the Puget Lowland.

Until this remapping is completed, we must

incorporate the existing data the best way we

can into current planning. It is hoped that

the accompanying tables wil I be of assistance

in this effort.

The purpose of this report is to summarize

in tabular form descriptions of the Quaternary

sedimentary deposits that make up the Puget

2 GEOLOGY IN LAND USE PLANNING

Lowland, to discuss briefly some of the im­

portant geologic processes that affect the

land, and to emphasize the significance of

geology in land use plclnning. Specifically,

this report has been prepared for use by land­

planning individuals and agencies.

EXPLANATION OF TERMS

In order to better understand the context

of this report, the following definition of

terms is included:

Alluvium

Clay, silt, sand, gravel, or other material

that has been transported by water ahd then

left along stream channels, river banks,

valleys, or other places.

Aquiclude

A body of underground rock that absorbs

and transmits water very slowly. Springs

usually result at the top of the aquiclude

if it is located on a hillside.

Aquifer

A body of underground rock that absorbs

and transmits water rapidly enough to

supply significant quantities of water for

wells and springs.

Consolidated material

Consolidation is the process whereby un­

consolidated sediments become more firm,

dense, and compact. Mud and sand and

gravel are origi na I ly unconso Ii dated

sediments. There are several ways in

which consolidation can occur: natural

processes include chemical, organic, or

mechanical means, while manmade

processes include pressure and mechanics.

Deltaic deposit

An alluvial deposit at the mouth of a

river. Genera Hy, the Pf eistocene deltaic

deposits of the Puget Lowland ore composed

of sand and gravel.

Glacial maximum

Position or time of greatest advance of a

glacier.

Glaciomarine

Refers to the interaction of glaciers and

ocean waters-glacial debris, marine

organisms, and marine sediments ore

deposited together at the same time.

Impermeable

Capacity of material to resist penetration by

water.

lnterstade

A relatively short period of decreased

glacial activity during a longer period of

glaciation.

Moraine

An accumulation of glacial sediment that

is deposited chiefly by direct glacial con­

tact or action.

Outwash material

An accumulation of silt, sand, and gravel

that is deposited by water from melting

ice in front of glaciers.

Permeable

Capacity of rocks or sediments to allow

water to enter or pass through.

Pleistocene

A period of time in the history of the

earth usually referred to as the ice age.

The time interval is approximately 10,000

years ago to 2! mi Ilion years ago.

I'

~' Mt.Olympus

~ A ( "I

(

A

l \ ,)

I \" ,,,, ... "' .. '

I I I .. ' \ ...... /

1Glocier Peak I

(

', '1 Stevens Poss

' ,,)

, Sn_!)quolmie Poss \ ... ,!

\ ,.J

' I I

~Chinook Poss

Area covered by fiaures 2 and 3 -

Mt. Rainier ' r

' f (

... > "' I

......!._Mt.Adams \

Mt. St. Helens \

R

\ \ \

\ \ I

D A

D

• IA SPOKANE

H

0

5 0 5 10 15 20 25 MILES

FIGURE 1.- Location of Puget Lowland and major population centers in Washington.

m >< "'O

> z ~ -0 z 0 'Tl

-I

~ V,

w

4 GEOLOGY IN LAND USE PLANNING

Porous

A term which refers to the amount of open

spaces in rocks or sediments that contain

air and(or) water. Generally, unconsoli­

dated sediments ore more porous than con ..

solidated sediments.

Quaternary

A period of time in the history of the

earth that is considered to extend from the

present to~ million years ago. The

Quaternary is subdivided into two times­

Pleistocene and Recent.

Recent

The period of time in the history of the

earth following the ice ages. It also

roughly corresponds to the earliest recorded

history of civilizations. It generally ex­

tends from the present time to approximately

10,000 years ago.

Richter magniture (scale)

A measure of the strength of an earthquake

or the energy released by an earthquake

as determined by monitoring devices

(seismographs). This scale was introduced

by C. F. Richter in 1935 and is in use

today.

Seismic

The rate or flow of energy through rocks

or sediments. Usually pertaining to the

earth vibrations resulting from an earth­

quake or vibrations artifically induced

through explosions or other sound waves.

Stade

A relatively short period of increased

glacial activity during a longer period

of glaciation.

Stratigraphic unit

An assemblage of rocks or sediments that

has been grouped into a unit for con­

venience in describing or mapping.

Topographic

The physical features of a region as shown

on a map.

GEOLOGIC SETTING

The Puget lowland is an elongate

topographic depression bounded on the east

by the Cascade Mountains and on the west

by the Olympic Mountains and Vancouver

Island. Approximately 10,000 to 2.5

million years ago glacial ice invaded the

Puget Lowland at least four times, leaving

a complex series of sediments up to 2,000

feet thick. As the continental ice moved

, southward from the north, it was split into

, two fronts by the Olympic Mountains; one

· front turned west into the Strait of Juan de

Fuca and the other moved into the southern

part of the Puget Lowland. At this stage

the ice front spanned the lowland between

the Olympic and Cascade Mountains, and

formed a dam across the lowland. This dam

impounded the drainage of al I the rivers

that flowed into the southern Puget Lowland

and formed a large lake (fig. 2). The lake,

which covered large parts of what are now

Kitsap, King, Pierce, and Thurston Counties,

was where the familiar "blue clays" of the

Puget Lowland were deposited.

As each of the four or more successive

ice sheets moved southward (fig. 3), water

from the melting ice deposited thick layers

GEOLOGIC SETTING

A glacial lake occupied the Puget Lowland to

an elevation of about 200 feet above present sea

level, draining out the Black River channel in

Thurston County to the Chehalis River. The

glacial Black River was comparable in size to

the present Columbia River.

5 0

PASS

! t

5 10 IS 20 MILES

FIGURE 2.-Advance of the Cordilleran ice sheet.

5

6 .. G.EOLOGY lN LAND USE PLANNlNG

MT. ST. HELENS At the time of the greatest extent of the

glaciers, ice was about 5,000 feet thick at Bellingham, 3,500 feet thick at Seattle, and 2,000 feet »tick at Tacoma. Direction of ice movement indicated by lines of medial moraines on the ice sur-face. VANCOUVER

Marginal drainage from the Puget Lobe and the flanking Cascade Mountains flowed in the trough between the ice and the mountain front from lake to lake, gathering all the drainage southward to Mount Rainier into a stream near Eatonville about the size of the Columbia River at Grand Coulee Dam. The Columbia River has an average gradient of about 1 foot per mile; this stream had an average gradient of about 9 feet per mi le.

5

i t

0 2 IO

FlGURE 3.-Maximum e.xtent of the Cordille.ran ice sheet.

MIS

, y,uii..rs

GEOLOGIC SETTING 7

GLACIER ICE

GLACIER ADVANCE

... C:

----------------------~ .:-:..:-__:-_-_-_-_-:_-_-_-__:--_-_-_-_-_-_-_-_-_-__ -_-_-_-_------=-----_-_-_-_-_-_-_-_-_-_-_-_-__:--_-_-_-_-_-_-_-_-_-_-.:.._-_-_---:­____________________________________ GLACIER RETREAT

FIGURE 4.- Simplified illustration of sedimentation during glaciation of the Puget Lowland.

8 GEOLOGY IN LAND USE PLANNING

of sediments known as outwash deposits in

front of the glacier. The outwash material,

generally composed of sand and gravel, is

the rock debris that was washed out of the

glacier as the ice melted. The outwash

materials were later overriden by the

glacier, which in turn deposited a con­

crete like material called 11 tilf 11 on top of

the outwash. As the ice melted during

glacial retreat, new layers of outwash

material were deposited over the top of the 11 till 11 (fig. 4).

Interglacial periods in the Puget Low­

land refer to times when the continental ice

was completely absent from the lowland and

the climate was much like that of today.

GEOLOGIC HAZARDS

The definition of a geologic hazard is

a naturally occurring or manmade geologic

condition or phenomenon that presents a

risk or a potential danger to life and property

( Gary and others, 1972, p. 292).

There are many types of geologic hazards

that could affect a community or region.

The greatest hazards are in areas of large

population concentrations, not always

because of the geologic setting but because

of people. Without people there are no

geologic hazards.

The types of geologic hazards that can

be expected to occur with some regularity

in the Puget lowland are land subsidence

or settlement, landslides, and seismic shocks

from earthquakes.

---------- ---

LAND SUBSIDENCE AND SETTLEMENT

The most subtle and evasive geologic

hazards ore those related to the reaction a

structural foundation undergoes when it is

built on a compressible type of earth

material. The damages caused by settlement

often go unnoticed because of the slowness

with which it occurs. This type of hazard

is usually amplified by other geologic haz­

ards such as the seismic shocks from earth­

quakes. Land subsidence in the Puget Low­

land is usually related to differential settle­

ment, which is the uneven gradual downward

movement of different parts of an engineer­

ing structure due to compression of the soil

below the foundation and often results in

damage to the structure. Porous, permeable,

unconsolidated sediments such as lake de­

posited si It and peat may be compressed

when subjected to loading. In the Puget

Lowland, alluvial and lake deposits,

especially peat bogs, are the most subject

to differential settlement.

LANDSLIDES

The process of landsliding is essentially

a continuous series of events from cause to

effect. Landslides usually take ploce under

the influence of geologic, topographic, and

climatic conditions that are common to the

Puget Lowland. These factors or causes

must be understood if slides are to be avoided,

controlled, or prevented.

A phenomenon known as I iquefaction-

GEOLOGIC HAZARDS 9

the temporary transformation of material into

a fluid mass- may occur when porous al I u­

vial type sediments, containing a high per­

centage of water, are subjected to strong

vibrations or seismic shocks. When liquefied,

the sediment flows in a fluidlike manner.

The I iquefoction can be initiated by an

earthquake shock or by vibrations from mov­

ing heavy machinery and equipment.

Lands I ides occur when the pul I of

gravity on earth materials on a slope over­

comes their frictlonal resistance to downslope

movement. The diversity of factors that

affect slope stability are briefly described

as follows:

1. ~ of earth materials- surficial

deposits or unconsolidated, soft sediments

will move downslope easier than consolidated

or partly consolidated sediments.

2. Ground shaking- strong shaking

during earthquakes, from large-scale

explosions, or vibrations of heavy machinery

can jar and loosen surface materials and

consolidated or unconsolidated sediments,

thus making them less stable.

3. Water - landsliding is generally

more frequent in areas of seasonally high

rainfal I because the addition of water to

earth materials commonly de:reases their

resi stem ce to sliding.

4. Steepness of slope~ - new landslides

occur more readily on steeper slopes; however,

low natural slopes may also be indicative

of existing landslides.

5. Proximity t~ areas undergoing

active erosion - rapid undercutting and

downcutting along stream courses and

shorelines makes slopes in these areas

particularly susceptible to landsliding.

6. ~ of vegetation - trees with

deep penetrating roots tend to maintain the

stability of slopes by mechanical effects and

contribute to the drying of slopes by absorb­

ing part of the ground water.

All the natural factors that promote

landsliding are present in the Puget Lowland.

In addition, man has increased the potential

for slope failures by increasing slope angles

through road construction and site prepara­

tion for building construction; adding water

to marginally stable slopes by watering

lawns, improperly handling rainwater runoff

and choosing poor sites for septic tank

drainfields; adding to the weight of stable

and marginally stable slopes by building

structures as well as by adding fill for

foundations; and removing the natural

vegetation, especially by deforestation.

A definite correlation has been estab­

! ished between time and place of major

landslides and a combination of climatic

and geologic conditions. Nearly all land­

slides can be related to periods of intense

precipitation, during a general period of

inferred high ground-water table. Future

episodes of widespread landsliding might

be expected during the late-winter period

of high ground-water table if a daily rain­

fol I of about l. 5 inches or more occurs.

The major lands I ides generally have occurred

at or near the contact between an overlying

permeable stratigraphic unit, such as sand or

grovel, and an underlying impermeable unit,

such as till or clay, and at or near the con-

10 GEOLOGY IN LAND USE PLANNING

.... 5.1 . 5.1

1934A 1934B

• 5.2 1960

5.9 A. 1939 ...

EXPLANATION

~ M > 6 ( FROM INTENSITY)

• M > 6 (RECORDED}

A M 5-6(FROM INTENSITY)

5.3 .a. .a. 1932A_.. _..

A 5.2 1903

EATTLE

' •

6.5 1965 5.2

A1961

A5.3 1916

TACOMA

A 5.3 1962

5.0 1932B

5.7 .a. 1945 ...

s.oA 1928

5.2 A 19408

FIGURE 5.- Location of epicenters and magnitudes of strong-motion earthquakes in southern Puget Lowland area since 1870.

CRITICAL RESOURCES AND LAND USE PLANNING 11

tact between glacial and nonglacial sedi­

ments.

EARTHQUAKES

Over 900 earthquakes have occurred

in Washington between 1840 and 1972. The

largest earthquake (Richter magnitude 7. 1),

as well as most of the damaging ones, has

been in the Puget Lowland area (fig. 5).

An analysis of the seismic history of the area

shows that small magnitude earthquakes occur

regularly, and that moderately intense shocks,

capable of producing severe damage to poorly

designed or poorly constructed engineering

works near the center of the effected area,

are frequent. Large magnitude events are

characterized by widespread intense shaking,

involving much of the Puget lowland area.

Apparently, none of the quakes during

historic times have been accompanied by

ground breakage at the surface; however,

it must be pointed out that the location of

faults within the Puget Lowland are poorly

known.

If the historic record persists in the

future, bui I dings, structures, and property

in the Puget Lowland are potentially sus­

ceptible to damage during earthquakes from

ground shaking but not from surficial fault

rupture. Most of the older glacial deposits

in the Puget Lowland have been compacted

by the weight of an ice sheet, 3,000 feet

or more thick, and are reasonably good

foundation material during an earthquake.

Locally, environmental conditions and the

nature of the earth material may create a

potential for slides. Potential for damage

from ground shaking is highest in areas of

artificial fill, areas underlain by peat,

existing landslides, and on valley floors

underlain by unconsolidated alluvial

sediments.

The estimated recurrence intervals of

seismic events for the Puget Lowland Region

are listed below (from University of Wash­

ington, The Nisqual ly Delta, 1970):

Recurrence Intervals Richter Magnitude (years)

3.5 - 4.0 0.25 - 0.5

4. 1 - 4.5 0.5 - 2

4.6 - 5.0 2 5

5. l - 5.5 5 - 10

5.6 - 6.0 10 - 30

6. l - 6.5 30 - 60

6.6 - 7.0 60 - 150

7.1+ 150+

CRITICAL RESOURCES AND

LAND USE PLANNING

The most valuable mineral commodity

produced and consumed in the Puget Lowland

is the material used for construction such as

sand and gravel. The principal, and also

the largest, source of sand and gravel is

the Vashon Recessional deposits, especially

the Vashon deltaic deposits. The Vashon

Recessional deposits are the single most

important mineral revenue source in the

. Puget Lowland.

12 GEOLOGY IN LAND USE PLANNING

In the Puget Lowland only 3 percent of

the land is considered to be "prime" agri­

cultural land, although other land is under

cultivation. Of the total pdme agricultural

fond, approximctety 60 percent is under

cultivation, 5 percent has been urbanized,

and the balance is used for pasture. The

principal use of the cultivated lands, which

are situated almost entirely on river valley

alluvium, is for the production of specialty

truck crops. Hay and grain are also pro­

duced on the cultivated land in support of

beef production and dairying~ which are

the major uses of the pastures.

These lands and their products are

critical resources that are vital to the grow­

ing and sustaining needs of an urbanized

area. Careful planning can result in wise

land use and conservation of our mineral

and land resources. The diverse uses of

Jand for agriculture, recreation, residential

or industrial urban development, and mining

can be integrated with enough foresight and

determination to serve everyone's purposes.

HOW TO USE THE TABLE

At the back of this report is a I ist of

geologic investigations "related to" the

Puget Lowland. Reports that contain geo­

logic maps are numbered, and indicate

either in the title of the report or at the end

of each reference, the county where the

work was done. The most complete and

most receht series of works are the Water

Supply bulletins published by the Washington

Division of Water Resources and available

from the Washington State Department of

Ecology. Many of the works listed are no

longer in print but are available from the

larger public libraries and are on file for

use in the library of the Division of Mines

and Geo logy.

The Correlation Chart, Plate 1, is a

convenient reference table, necessary to

distinguish subtle relationships both within

and between various stratigraphic uni ts

throughout the Puget Lowland. The purpose

of the Correlation Chart is to show the

approximate age and stratigraphic position

of the geologic deposits for a specific

county in relation to other counties in the

Puget Lowland.

The chart has been divided into

columns by counties (Thurston, Mason,

Pierce, Kitsap, King, Snohomish, Island,

and Whatcom) and regions (Southern Puget

Lowland and Northern Puget Lowland). The

chart has also been divided into an approx­

imate south-north direction; the columns

for the more southerly counties being

located to the I eft on the chart, and the

columns for the more northerly counties

being located to the right on the chart.

Each column is set up with younger

deposits listed toward the top of the column

and older deposits listed toward the bottom

of the column. For instance, in the Mason

County column, "Alluvium" is listed at the

top of the column and is therefore the

youngest deposit, while "Salmon Springs

Drift" is at the bottom of the column and is

the oldest deposit. The names for the de­

posits are separated by either horizontal

HOW TO USE THE TABLE 13

and(or) slanted lines. The slanted lines are

meant to indicate some question or doubt

as to the age and stratigraphic position of

the deposit, usually indicating that the

materials above and below the slanted I ine

were being deposited at or about the same

time. The relationship of deposits between

counties can be determined by selecting the

name of a deposit in the column for a cer­

tain county, tracing horizontally to the

column for another county and reading the

name of that deposit. For instance, trace

down the Thurston County column to the 11 Kitsap Formation, 11 then trace horizontally

to Whatcom County and to "Cherry Point

Clay. 11 The name II Kitsap Formation"

corresponds to the name "Cherry Point Clay, 11

or in other words the "Kitsap Formation"

of Thurston County and the "Cherry Point

Clay" of Whatcom County were deposited

at about the same time.

Plate 2 is a compi lotion of general

engineering properties of Quaternary

geologic units within the Puget Lowland and

was prepared as a guide for land use plan­

ning purposes. A geologic map can be

obtained for a specific county or area by

referring to the list of geologic investiga­

tions at the back of this report. The general

engineering properties of the table can then

be applied to the units used on the geologic

map.

As an example, use the map (Plate 1)

from "Geology and related groundwater

occurrence, southeastern Mason County,

Washington, 11 by Molenaar and Noble ( 1970).

The areas noted on the map by the symbol

Qk are identified in the map explanation as

Kitsap Formation. Use Plate 2 of this paper

and trace down the second column, which is

identified as Rock Stratigraphic Unit, to

Kitsap Formation. The physical and engineer­

ing properties listed in the row to the right of

the Kitsap Formation can then be applied to

those areas noted as Qk on the map. For

instance, under the Ground Water column

the listing is "Poor permeability, except for

a few gravel layers; serves as an aquiclude

to underlying confined ground water along

shoreline areas. Ground water seeps common."

Under the Slope Stability column, the listing

is "Variable, but generally unstable on

slopes steeper than 26°. Dependent on

local conditions of slope, drainage and

ground water." The areas noted on the map

by the symbol Qal are identified in the map

explanation as Alluvium. Trace down the

second column to Alluvium and apply the

properties listed in the row to the right of

Alluvium to those areas noted as Qal on the

map. For instance, under the Seismic

Stability column the listing is "Very poor.

Maximum destruction during April 1949

earthquake occurred on alluvium and

artificial fill." Under the Planning Signifi­

cance-Major Uses column the listing is

"Critical resource-prime agricultural land;

fi 11, topso i I for lawns and gardens. 11 Areas

on the map noted as Qal such as Skokomish

Valley, Egypt Valley, Shelton Valley,

Isabella Valley, and Kamilche Valley are

prime agricultural land and therefore

critical resources. These areas would also

potentially be most subject to severe damage

14 GEOLOGY IN LAND USE PLANNING

during intense shaking from an earthquake.

LIMITATIONS

The use of the table fn evaluation of

geologic oonditions is limited by the state

of the art, available information in litera­

ture, and practical field investigations.

The conclusions, data, and opinions

made in .this report are based on the presentfy

available information and are made for land

use planning purposes only. This report is

not intended to be, nor should it be used as

an engineering geology report for any given

site. ln all cases, a detailed engineering,..

and geology report is recommended for indi­

vidual site evaluations and investigations.

Field work for this report has been limited

to visual inspections, no laboratory testing

or subsurface exploration h,ls been mad,e.

INDEX OF GEOLOGIC MAPPING

I

- - -- - - ~1!',LLAM __ __J

JEFFERSON

---,__ ______ ,-MASON-

' I

I ,,

L-...-

( .. ~ \

_ WHATCOM __ _,--r'' ']

C ,-""",_

,'

_,,_ ______ =SK=-AQ!T_ ~ ' 5 '

SNOHOMISH ')

,/')

I \ """"---,.....-- -----~

1 .

/' !~-' I '"'""I

_(

~~ ~ , ,- 1 Liesch and others, 1963

, I

PIERCE --~ ----,_/ "J • ' /

2 Luzier, 1969 3 Molenaar, 1965 4 Molenaar and Noble, 1970 5 Newcomb, 1952 6 Noble and Wallace, 1966 7 Waldron, 1967 8 Walters and Kimmel, 1968

PACIFIC ,- ~-~ -----------,-- LEWIS __ 1_j 9 Washington Division of Water

Resources Staff, 1960 I I

'COWLl~~-----(1

/..._/' :

I I I

SKAMANIA

I

I I I

I_J t I

L. I

t t

0 6 12 18 24 ~ILES

FIGURE 6.- Index of geologic mapping in the Puget Lowland for use with this report. Numbers on map correspond to those in Selected References.

15

16 GEOLOGY IN LAND USE PLAN NI NG

S E LE C T E D R E F E RE N C E S*

Crandell, D.R., 1961, Surficial geology of the Orting, Sumner and Witkeson quadrangles,

Washington: U.S. Geological Survey open-file maps, 4 sheets. [Pierce County]

Crandell, D. R., 1963, Surficial geology and geomorphology of the Lake Topps quadrangle,

Washington: U.S. Geological Survey Professional Paper 388-A, 84 p. [Pierce

and King Counties]

Crandell, D. R.; and others, 1958, Pleistocene sequence in southeastern part of the Puget

Sound Lowland, Washington: American Journal of Science, v. 256, no. 6,

p. 384-397.

Crandell, D. R.; Gard, L. M., Jr., 1960, Geology of the Buckley quadrangle, Wash­

ington: U.S. Geological Survey Geologic Quadrangle Map GQ-125. [Pierce

and King Counties]

Easterbrook, D. J., 1963, Late Pleistocene glacial event and relative sea-level changes

in the northern Puget Lowland, Washington: Geological Society of America

Bulletin, v. 74, no. 12, p. 1465-1483. [Whatcom County]

Easterbrook, D. J ., 1966, Glaciomarine environments and the Fraser glaciation in north­

west Washington: Guidebook for First Annual Field Conference,· September 24-25,

Pacific Coast Section, Friends of the Pleistocene, 52 p.

Easterbrook, D. J., 1969, Pleistocene chronology of the Puget Lowland and San Juan

Islands, Washington: Geological Society of America Bulletin, v. 80, no. II,

p. 2273- 2286.

Gary, Margaret; and others (editors), 1972, Glossary of Geology: American Geological

Institute, Washington, D. C., p. 292.

Gower, H. D.; Wanek, A. A., 1963, Preliminary geologic map of the Cumberland

quadrangle, King County, Washington: Washington Division of Mines and

Geology Geologic Map GM-2.

* Numbers opposite bibliographic entries correspond to numbers on Figure 6.

' '

. ' ,.

SELECTED REFERENCES 17

l. Liesch, B. A.; and others, 1963, Geology and ground-water resources of northwestern

King County, Washington: Washington Division of Water Resources Water Supply

Bulletin 20, 241 p. Plate 1

Livingston, V. E., Jr., 1971, Geology and mineral resources of King County, Washington:

' Washington Division of Mines and Geology Bulletin 63, 200 p.

2. Luzier, J. E., 1969, Geology and ground-water resources of southwestern King County,

Washington: Washington Department of Water Resources Water Supply

Bulletin 28, 260 p. Plate 1

3. Mo I enaar, Dee, 1965, Geo logy and ground-water resources. In Water resources and

geology of the Kitsap Peninsula and certain adjacent islands: Washington

Division of Water Resources Water Supply Bulletin 18, p. 24-50. Plate 1, 2

sheets. [Kitsap County and parts of Mason, Pierce and King Counties]

4. Molenaar, Dee; Noble, J. B., 1970, Geology and related ground-water occurrence,

southeastern Mason County, Washington: Washington Department of Water

Resources Water Supply Bulletin 29, 145 p. Plate 1

Mullineaux, D. R., 1965, Geologic map of the Auburn quadrangle, King and Pierce

Counties, Washington: U.S. Geological Survey Geologic Quadrangle Map

GQ-406.

Mullineaux, D. R., 1965, Geologic map of the Black Diamond quadrangle, King County,

Washington: U.S. Geological Survey Geologic Quadrangle Map GQ-407.

Mullineaux, D. R. 1965, Geologic map of the Renton quadrangle, King County,

Washington: U.S. Geological Survey Geologic Quadrangle Map GQ-405.

Mullineaux, D. R.; and others, 1965, Stratigraphy and chronology of late interglacial

and early Vashon glacial time in the Seattle area, Washington: U.S. Geological

Survey Bui let in 1194-0, p. 1-10.

Mullineaux, D. R., no date, Northeast quarter of the Tacoma quadrangle: U.S.

Geological Survey unpublished map. [Pierce County]

5. Newcomb, R. C., 1952, Ground-water resources of Snohomish County, Washington:

U.S. Geological Survey Water Supply Paper 1135, 133 p. Plate 2

18

6.

GEOLOGY IN LAND USE PLANNING

Noble, J.B.; Wallace, E. F., 1966, Geology and ground-water resources of Thurston

County, Washington, V. 2: Washington Division of Water Resources Water

Supply Bui letin 10, 141 p. Plates 1 and 2

Ric:hGJrdson, Donald; GJnd others, 1968, Water Resources of King County, Washington:

U.S. Geological Survey Water Supply Paper 1852, 74 p.

.. . ~

Robinson, J. W.; Piper, A. M., 1942, Geology of parts of the Anderson Island, Tacoma

South, and Ohop Valley quadrangles: U.S. Geological Survey unpublished

maps, 3 sheets. [Pierce County]

University of Washington, 1970, The Nisqually Delta: University of Washington

Department of Geological Sciences, Environmental Geology seminar, 88 p.

Vine, J. D., 1962, Preliminary geologic map of the Hobart and Maple Valley

quadrangles, King County, Washington: Washington Division of Mines

and Geology Geologic Map GM-1.

Waldron, H. H., 1961, Geology of the Des Moines quadrangle; Washington:

U.S. Geological Survey Geologic Quadrangle Map GQ-159. [King County]

Waldron, H. H., 1961, Geology of the Poverty Bay quadrangle, Washington:

U.S. Geological Survey Geologic Quadrangle Map GQ-158. [King and

Pierce Counties]

Waldron, H. H.; and others, 1962, Preliminary geologic map of Seattle and vicinity:

U. S. Geological Survey Miscellaneous Geologic Investigations Map 1-354.

[King County]

Z Waldron, H. H., 1967, Geologic map of the Duwamish Head quadrangle, King and

Kitsap Counties, Washington: U.S. Geological Survey Geologic Quadrangle

Map GQ-706.

8. Walters, K. L.; Kimmel, G. E., 1968, Ground-water occurrence and stratigraphy

of unconsolidated deposits, central Pierce County, Washington:

Washington Department of Water Resources Water Supply Bulletin 22,

428 p. Plate l

9. Washington Division of Water Resources Staff, 1960, Water resources of the Nooksack

River Basin and certain adjacent streams: Washington Division of Water

Resources Water Supply Bulletin 12, 187 p. Plate l [Whatcom County]

TIME

UNITS

RECENT

LATE PLEISTOCENE

AGE

(years}

10,000

12,500

obout

15,000

GEOLOGIC

CLIMATE UNITS

Recent

Interglacial

Fraser

Glaciation

41 "O .E V'l

"' 0

§ V'l

41 "O E V'l

C

~ 0

>

THURSTON COUNTY

Noble and Wallace

(1966)!/

Alluvium

...........

Lake Russell.........._ -...........

sediments ----- ---Recessional outwa sh

--- --Moraine deposits

- -~ --Advance outwash

-- ---Colvos Sand

--------- - - - -

Olympia

lnterglaciation

Kitwp Formation

PLATE 1.- CORRELATION CHART- QUATERNARY DEPOSITS OF THE PUGET LOWLAND

MASON COUNTY

Molenaor and Noble (1970)

Alluvium

...........

' "

PIERCE COUNTY

Wa lters and Kimmel (1968)

Alluvium

with

mudflows

/ /

/ Lake sediments ". -- -- / Steilacoom ------

Recessional outwash

--- -Moraine deposits

- -- Till -

Advance outwash

Skokomish Grovel/

/ /

Kitwp Formation

". grovels

" " Recessional "-.

outwash

Till

Advance gravel

----Colvos Sand

Kitwp Formation

SOUTHERN PUGET LOWLAND

SOUTHERN PUGET

LOWLAND

Crandell and others

/

(1958)

Alluvium

with

mudflows

/ /

/

/

Recessional outwash

Till

Advance outwash

KITSAP PENINSULA

Molenaar (1965)

Alluvium

........... ...........

Lake Russe ll .........._ .........._

sediments ---_.-~ Gravels

"' Recessional "-.

outwash "-.

Till

Advance outwash - -- --Colvos Sand

Unnamed grovels ----------Kitsap Formation

SOUTHWESTERN KING

COUNTY

Luzier (1969)

Alluvh.m

with

mudflows

Lake sediments --- - -- -Recessional outwash

...._ Ice...._...__

contact depasit;--- --

Till

Advance outwash

-

KING COUNTY

Mullineaux and others

(1965)

NORTHWESTERN KING

COUNTY

Liesch and others

, ­...........

(1963)

Alluvh.m

- - -Delta gravels

...........

Recessional drift

Till

Advance drift -- ---Esperance Sand Member Unnamed sand - -- - -

Lawton Clay Member

Nonglacia l sediments

Upper

clay

unit

--------- - - - - - - - - Unnamed grovels

Salmon Springs

G laciation

Salmon Springs Drift?

--------- - - - -

EARLY

PLEISTOCENE?

Puyallup

lnterglaciation

Stuck

Glaciation

Alderton

lnterglaciation

Orting

Glaciation

!/ See text for list of selected references.

Pre-Salmon Springs

deposits

Undifferentiated

Logan Hill Formation

Salmon Springs Drift Salmon Springs Drift Salmon Springs Drift

Puyallup Formation Puyallup Formation

Stuck Drift Stuck Dri ft

Alderton Formation Alderton Formation

Orting Drift Orting Drift

Salmon Springs Drift

Pre-Salmon Springs

deposits

Undifferentiated

Salmon Springs Drift

Puyallup Formation

Intermediate drift

Orting Drift

Lower

clay

unit

SNOHOMISH COUNTY

Newcomb (1952)

Alluvil.m

t older

Recessional outwash

--. ...._ Marysv1 I le ........._

> / Sand

Member / / / Arlington

/ Gravel Member -- ---

Stillaguamish Sand Member

--

l'ill

Advance outwash - - - -Esperance Sand

Member ----Pilchuck Clay Member

Admiralty Clay

NORTHERN PUGET LOW LAND

NORTHERN PUGET

LOWLAND

Easterbrook (1969)

Alluvium

- - -Sunas Drift

Everson Glaciomarine

Drift

Ti II

~dvance outwash - --Esperance Sand

Quadra Sediments

Possession Ori ft

Whidbey Formation

Double Bluff Drift

ISLAND COUNTY

Easterbrook (1966)

Alluvium

-- --Sunas Drift

Everson G lacioma rine

Drift

Gravels /

/

/ /

/

Till

Esperance Sand

Quadra Forma tion

Possession Ori ft

Whidbey Formation

Double Bluff Drift

WHATCOM COUNTY

-

Easterbrook (1963)

Alluvium

l older

Abbotsford outwash

Sumas Drift

Bellingham

Glaciomarine Drift ----- Deming Sand - ---Kulshan

Glacioma rine Drift

--·---Ti ll

Mountain View Sand

and Grovel

Cherry Point Clay

GEOLOGIC

C LIMATE UNITS

41 "O .E V'l

C _g 0 >

Recent

Interglacial

Fraser

Glaciation

O lympia

lnterglaciation

Possession

Glaciation

Whidbey

Glaciation

Double Bluff

Glaciation

I PLATE 2.-GENERALIZED DESCRIPTION OF ENGINEERING PROPERTl r OF QUATERNARY GEOLOGIC NAME UNITS (PUGET LOWLAND )

I GEOLOGIC CLIMATE ROCK STRATIGRAPHIC COMMENTS AND SPECIAL DESCRIPTI ON DRAINAGE GROUND1WATER EASE OF EXCAVATION FOUNDATION STABI LITY SLOPE STABILITY SEIS,\A.IC STABILITY PLANNING SIGNIFICANCE

UNITS UNITS FEATURES (Mojor Uses)

Includes beaches, deltos, Mostly unconsolidated silt, Runoff variab le but generally Water table ne,J surfoce . Generally easy to excovote Foir; may settle excessively Genera lly poor because of Very poor. Maximum de- Criticol resource-prime og-

ond ortif1ciol fi ll. sond, and 9rovel, wi th poor because of low slopes . Permeobil ityr orioble . with hond or power equip- and irregularly because saturation . Moy stand in struction during April 1949 riculturol land. Fi l l, Alluvium , Contains interbedded peat some cloy and oeot . lnflllration moderate to men! . Con genero l ly be of layers of compressible steep cuts for short earthquake occurred on lopsoi I for !owns ond

and muck locolly. very slow. Subject to dredged. orgonic moteriol . periods where above olluvium ond ort;ftcio l go rd ens . flood ing .

I water toble. fill .

Deformed deposits ond debris Intimately mixed material Ruooff poor . Slide movement Water table ge! rol!y close Generally easy to excovote Mostly unsuitable. Correc- Both natural ond cut slopes Very poor . Seismic shocks /'<O n-select fill .

o f mo .. flowoge ond block from vorious units, ond produces depressions that to surface. Permeability with hond or power tive measures needed. generally unstable. moy set c mcss into landslide deposih

slide,. discrete blocks of catch ond hold water . generally lo"t• equipment . movement ogoin ,

various units. Infiltration slow .

I

Includes O.ceolo ond Electron Nonsorted till-like mixture Runoff poor becou5e of flat I

Usually saturated, but not o Difficult to excavate with Generally good, no settl;ng Stands in 5teep r.aturo I ond Good . Non-select fll I.

mudflows. of gra nule- to cobble- topography ond high cloy source of gn::und wc ter hcnd or light power e xpected. cut slopes, Rcvels and Recent lnterglociotion

Mudflows ;;ze rock fragments in content. lnfil t rotion becouse of le;w permecbili- equ;pment, Fcirly com- spalls with wetting cnd cloy, silt, and sond slow. ~-Orgonic debris and pact, locks bedding . drying, ond freezing and motr;x , pyr ite moy c;, ~ect quality thawing.

of ground wor r.

Includes peat deposits. Mostly mixtures of si It, cloy, Runoff poor, mc;,ledol usuo !ly Water table ot ~r near sur- Generally easy to excavate Very poor; wil l settle excess- No t generol ly found on notu- Very poor to fair, Seismic Peat bogs ore source of or-Water content mc;,y be os and fine sond with varying occumulotes in closed de- face . Permoobility with hand or light power ively under locd , low rol slopes . Will stand shocks wil l cause consoli- gonic moteriol for top-much as 10 times dry quantities of organic mo- pressions. lnflltrotion usuol ly very low. equipment . Con generol ly bearing capacity . for long periods if dry, dction of sediments. soi/ beneficiotion . Lake deposits weight . teriol . Peat is chiefly moderate when dry, but be dredged. Moy contoin but deposHs generally ore

decomposed vegetol generally saturated. large logs and locally be M>turoted ond will stand molter. Seasonal flooding commcn. cohesive. for only short periods .

Mopped only in western port Consists of stratified sand c;,nd Ruooff poor to foir on r,oturol Presence depends on topography Generally eo5y to excovote Fair to exce llent, best on Generally stcble in slopes up Good. Rocd metal, concrete ond of Whatcom County , grovel, mostly horizontclly surfaces, poor where vege- cnd underlying material . w;th hand or power oreos of li ttle or no slope. to 26°, sand foc i es subject ospholt cggregote, drain-

Abbotsford outwc,h bedded . lo tion ond soil hcve been Contains perched ground equipment. to severe rcin wosh cnd fleld grovel, fill.

removed , lnflltrolion woter in lower port in many gulley;ng , moderate on naturcl sur- areas. Permeobi li ty high.

faces, fost on cut surfaces. Springs oom,.l,n near bcse. I • ~

2 - Mopped only in Whatcom Consists of t i ll , ice contcct Runoff vorioble . Undrained Water toble depends on lopo- Usually very difficu lt to Excellent. Generally wil l stand in Good . Fill.

' County within Smiles of deposits of poorly sorted ond poorly drained de- grcphy. Permeability excavate with hcnd or steep s lopes up lo 33°; ' > - Sumo, Drift the town of Sumos at the grovel, ond strotifled pressions common , Run- very low except in con- power equipment. locks slope foi lures usuol ly Concdion border. grovel contoining leraes off good on steep slopes. toined lensefaof sand cnd bedding or ex tensive extend to c;, depth, of only

of t ill. lnflltrotion very slow . grovel. l fractures . o few feet . I I

• Includes Bellingham ond Consish of poorly sorted, Runoff voricb!e, but gener- Permeability vatic;,ble, '" Moy be difficul t to excavate Foir to good . Clcy fccies Moy stond in steep slopes Good • Non-select fill . ~

I Kul,hc;,n Glcciomorine fossiliferous sediments, clly p:,or; infiltration usuol ly low , with hond or light power may require corrective greater thon 33° for long

Everson Glociomorine Drift Drifts and Deming Sand. vorying from pebbly silt usually poor. equipment, locally moy measures, periods. -Mopped in the northern c;,nd cloy with scattered be cohesive, C

! Puget lowland, pebbles to till-like • > w glociomorine deposits.

limited to southern Puget Consists mostly of silt ond Runoff vorioble; inflltrotion Permeability vi low. Generally easy to excavate Poor to fair- corrective Generally unstable on slopes Usually good, except where Clcy products . Lowland geM"ro lly below cloy . ""'. with hand or light power measures needed. steeper thctn 26° . conditions may crecte c Loke Russell sediments elevotions of 200 feet; equipment-may be potential for slides,

I recessional lake beds . cohesive .

Includes Steilccoom gmvels, Consists mostly of light- gray Runoff poor on naturo l sur- Very high permL bility. Generally easy to excavate Fcir to excel len t, but may be Generally stable in slopes up Good , Critical Resource . and other recessiona l grovel ond sond deposited foces. lnf11trction mod- Springs common near base. with hand or power poor on slopes that op- to 26°; may slcnd tn

deltoic grovels. by recessional outwosh in erote on natural surfoces, equipment . prooch the angle of re- steeper cu ts for short Lcrgest grovel pits in the Vashon delto grovels glacial lakes . Up to 200+ fost on cut surfaces . pose of the moteriol. periods of time . stole operate in these

' feet thick; upper sur-motericls.

face is generc lly o

terrace .

Mcrysville ond Stilloguomish Consists usuolly of poorly Runoff poor to fa ir on no t- Presence depeitls on topo- Mcy be excovoted with hcnd Fair lo excellent, but mcy be Generally stoble in slopes Good , Rood metal, concre te ond Sand Members. Recession:- sorted, ungraded, ond un- urol surfaces; infiltration grophy and 1nderlying or light power equipment , poor on slopes that up to 26°. Where unit asphalt oggregote, drain-0 1 strotifled drift cnd cemented stratified drift moderate on slopes with motericl . Contoins Mcy be poorly cemented cppracch the ongle of overl;es impermeable field grovel, fill ,

Voshon recessional outwosh ice contact deposits. ond ossocicted deposits no turo l soil ond vege- perched groJ..d water in locally. repose. Little settli ng moteriol, springs near

Fraser Glociotion mode up ptimorily of silt, totion cover, but fast lower port in many areas . mcy occur locol ly. base cause erosion and

sand, ond grovel . where these hove been High permeability. sliding of sond focies. removed . Springs common neor base .

Probcbly the only name unit, Nonsorted, blue-gray to gray Runoff voriob!e . Undrained Height of water toble de- Very difficult to excovcte Excellent . Stands in steep nctu ro l ond Good . Fi 11 when properly excovoted which is used exclusively concretelike mixture of ond poorly droined de- pends on topography . with hand or light power cut slopes for long periods. cnd placed . throughout the Lowlc;,nd, cloy, sil t , sand , cnd pres.ions common . Runoff Permecb i Ii ty very low equipment. Dense, tough, Moy ravel cnd spoil by • v;,shon till ~ Also referred to cs ground grovel . Moy contain good on steep slopes. except in con tained ond general ly locks bedding wetting ond dry;ng, ond 2 - moraine . loco I lcyers of sand, lnfi ltrotion very slow . layers of sand ond grovel. or extensive fracturing. freezing and thawing . C

' ' grovel, cnd lorge > boulders.

Proglocic;,I oulwo.h. Consists generally of light Runoff poor. lnflltrotion Permecbility high. Yields Moy be excavated with hand Good to excellent; may be Mcy stand in steep slopes Good, Fill, cnd sand for concrete gray sond and grcve l in moderate on natural sur- smal l to lcrge quantities or !ight power equipment , poor on slopes thct greater thon 26° for short oggregote. disconti nuous stroto with foces . Fcst on cut (2~800 gpm), depending Mcy be port ly cemented approach the cngle of periods, slope failures

Vashon odvcnce oulwosh some thin silt bed, . surfaces. upon thickness of coorser locally. repose of the mcteriol. usuolly e xtend too depth material below regional of only o few feet. water table, Springs

common nec r base.

- 1- Runoff poor to fair on no t- Penneobility hi~h . Contains Fair to excel lent; best on Generally unstable on slopes Generally good . Proglociol outwosh olso Consists chiefly of sand Generally very ecsy to Fill ond sand for concrete. mopped os Colvos Sand, opporently deposited in urol surfaces, poor where perched ground woter in excovote with hcnd or oreos of little or no steeper thcn 29°. Subject Mountoin View Sand ond o lake. locally, the unit vegetation and soil hcve lower port , Springs very power equipment . Noo- slope-little settlement to severe rcin-wosh ero-

Esperence Sand Grove!, and 5Clnd phose contoi ns some layers of been removed. lnfi ltrc- common M'Or base cnd cohesive , expected. sion ond gullying. Moy

of the LoWton Forma tion. grovel. tion modercte on nohxo! above silty or peat layers . stand in steep cuts for

surfaces, fost on newly short period of time .

cut surface,.

Praglccio! lake deposits also Thinly lcminated silt and Run:>ff vcrioble, usually Permecbility very low- Generally eosy to excovcte Poor to fair, usua lly requires Both ncturol ond cut slopes Poor lo good depending upon Cloy products, mcpped os port of the cloy -interpreted cs poo, . Infiltration slow locolized perched wcler wjth hond or power equip- corrective mecsures, generally umtob!e. The local condttions of slope, Lawton Formction . Moy having been deposited to very slow . tob!e often loca ted above men!, but mcy be difficult majority of lcndslides in drainage, ond contained

Lawton Cloy be included in the Kitsap rapid ly in o lcke. this unit. Springs ore becouse of oohesivenes , Seat tle jn the spring of ground wa ter . Formation ;n Kitscp very common obove this 1972 hove been attributed County. unit. to failure clang this unit .

Mopped clang eastern side Generally coarse reddish Runoff foir lo good on ncl- Yields smcll to large supplies Moy be excovcted with hand Good to e xcellent . Generally will stcnd in slopes Good, Fill, oggregotes, ond other of O lympic Peninsula . grovel with thin stro to of uro! surfaces; foir to with increcsing depth or light power equipment . up to 33° . construction motericls. Appears to thin cnd inter- sand, silt, cloy . poor where natura l vege- (30 lo over 500 gprn); moy

bed with Kitsap? Fm . tction cnd soi I hove been be major producer for deep

removed . Infiltration industrial wells in orec, Skokomish Grovels

mcderc te on slopes with Springs common above

' noturol cover of soi l silty lcyers .

ond vegetotion, but

Fast where these hcve

Olympia lnterglcciotion been removed.

Equivalent? to the Ouodro Consists of sil t, sond, c;,nd Runoff vcrioble . lnfl!trotion Poor permeobi lity except for Highly voricble. Mcy be Poor to good , Corrective Voriob le, but generally un- Usually good, except where Cloy products? Formation in the northern cloy, thin to massive slow . o few grovel layers; serves difficult to excavate wj th measures usuo I ly needed . stoble on slope, sleeper condition moy creole c Pugel Lowland . Previous- bedded. Shows evidence <JS on oquic lude to under- hand equipment. Dense, than 26° . Dependent on potenHol for sl ides .

Kitsap Formation ly mopped os Kitsap Cloy, of having been deposited lying confined ground compact, and cohesive. loco I conditions of slope, Lawton Formction, P;I- in o nongloc io l environment water a long shore line drcinoge, cnd ground chuck Cloy, Cherry Point of flood plains ond sha llow orecs . Ground-wcter seeps wc ter. Cloy ond Ouodrc Sedi- la kes. common.

ments .

Equivalen t to the P..,ssesion Consists of oxidized sond ond Ruooff fair to good on not- Generally high permeability. Genero lly difficult to exco- Good to excel lent . Generally wil! slcnd in steep Good. Genera lly suitable for fill, Drift in the northern grovel of pebble to cobble uro! surfaces; poor where Properly constructed wel Is vote with hand or light slopes up to 33°, slope concrete and osphol t Puge t Lowlcnd , Previous- size; contotns thin discon- natural vege tation and hove yielded 300 to 1200 power equipment . Til I failures usuclly extend lo oggregote, drain-field

Sclmon Springs Glaciation Solman Spring• Drift ly mcpped o, Kltnker Till tinucus horizons of till, '50il hove been remcved . ,pm. layers lcck bedding or depth of only o few feet. grove l , rood metal, and cnd lower member of the peat, silt, cloy, cnd lnfiltro tion moderate on frnctures . o ther structural mcleriol . Orting Grovel. mudflows , slopes with noturol cover

of soi I ond vegetation .

Equivalent to the Whidbey Consists of sand, volcanic Runoff vcricble. Infiltration Relctively impermeable- Vorioble, but generally dif- Poor to good. Corrective Subject ta lcndsliding . Fair to good , Cloy products , Formotion in the northern mudf lows, peat, pecty slow . grcvel ond sand lenses will ficult to excovote with measures mcy be needed . Highly variable, may Pugel Lowlcnd. Previous- si lt cnd c loy with discon- yield smoll amounts of hcnd or light .oower equip- Rebound reported in the stond in steep cuts; how-

Puycllup lnlerglociotion Puyallup Formclion ly mopped os Duwomish tinuous grcvel. wcter . Ground wcter ment. Usually compoct silt cnd clcy . ever, contained ground Formation and Am1irclty seeps common along sand cnd cohesive. water under high hy-Cloy. ond grovel layers .

dro,totic hecd mcy result

in low nclurol slopes .

Equivalent to the Double Composed of gray clayey Runoff voricble; usually foir Poor permeability . Fine- Highly voriob!e-generolly Generally excellent, but Generally will stond in steep Good . Non-select flll, cloy Bluff Drift in the northern till within o sequence of to moderate on noturcl groined lc;,ke beds will difficult to excovote may be poor on slope• slopes up to 33°, slope products? Puget lowland. Prevj- sand, silt, c;,nd clc;,y. surfaces . Infiltration yield very little water. with ha,d or light power thct cpprooch the cngle fotlures usually extend to

Stuck Glcciction Stuck Drift ously mcpped os Beacon slow to moderate on slopes, Sand cnd grove! !ayers equipment . Compact, of repose of the materials. o depth of only c;, few feel. Till, Admiralty Cloy, with noturol cover of soil will sometimes contcin dense . Till layer, lock and intermediate drift. ond vegelc;,tion . smc;,II quantities o f bedding or fracture, .

water.

Mcpped only in centrol Consists of fine to medium Runoff vorioble-usuolly Generally poor permeability . Variable, but generclly dif- Poor to good . Dependent Subject to landsliding . Highly Foir to good. Cloy products? Pierce County in con- sand, silt, cnd thin moderately fost . lnfil- Grovel layers will yield ficult to excovote with on loca l condi tions of vorioble. Moy stcnd in junction with the Stuck loyers of peat . Contains trotion slow . water . Seeps common hand or light power equip- slope, drainage, ond steep cuts; howe ver, Drift, elongate layers of grovels, olong sand cnd grovel men! . Usually dense, ground wo ter conditions. contoined water under

Alderton lnterg lcciction Alderton Forma tion which apparen tl y were lcyers. com po ct , cnd cohesive . Corrective m'!'Osures may high hydrostatic hecd deposited in streom chon- be needed. results in low natural nels; volcanic mudflows slopes. also cbundont.

Mopped only in central Consists mostly of oxidized Runoff fair on na tural sur- Fairly high permeability and Generc \ly difflcul t lo excovcte Generally excellent; moy be Generally wil l stcnd in steep Good , Fill, concrete and osphclt p;erce County. '50nd cnd grove l of pebble faces; poor where vegeto- ccpob!e of yielding with hcnd or l_ight power poor on slopes thct slopes up to 33°, slope oggregcte .

to boulder size; oontcins lion and soil hcve been moderately large quon~ equipment. Locol ly cpprooch the ongle of failures usually exte nd to thin discontinuous horizons removed. lnfl ltrotion tities of water. Up to cemented . repose of mcteriols. o depth of only a few feet .

Orting Glcciotion Orting Drift of highly oxidized stony modercle on slopes with 500 gpm could be possible

till. ncturol cover of soil cnd from properly constructed

vegetotion. wet!s. Springs common

near the base cnd cbove

silty layers .

Mopped only in the southern Portly consoljdoted, Runoff good on noturol sur- Poor permecbility in upper Generally may be excovoted Poor to good-usually Moy stand in moderately steep Reasonab ly good, except Unwecthered motericls mcy be Puget lowlcnd . wecthered, iron-stained foces-ropid runoff where 30 to 50 feet; moderate to with hond or light power corrective meosures ore slopes; many londsl ides where envjrorvnentcl con- used for fill but generally

grovel cnd M>nd . The vegetotion ho, been re- high permeability with equipment, Upper 30 to needed . where the unit 1, deeply ditions ond nature of the ore not well suited for con-upper 30 to 50 feet is so moved. depth. 50 feet may be cohesive. incised by strecms . Physi- geclogic ma terial may struction moleriol.

Ecrly Pleistocene? logon Hill Formction weothered that grovels co l conditions ore pcrticu- creole c potential for slides . Weathered material mcy be

hove been a ltered to lorly favorable for the suitcble for structural wore .

cloy. development of landslides

clang the contac t between

this unit cnd o lder un its.