division of mines and geology -...

.. ~ -...-fr:_ -.• ; STATE OF CALIFORNIA-THE RESOURCES AGENCY

DEPARTMENT OF CONSERVATION

DIVISION OF MINES AND GEOLOGY BAY AREA REGIONAL 9FFICE 380 CIVIC DRIVE, SUITE 100 PLEASANT Hill, CA 9.4523· l 997 PHONE, (415) 671-4920

Mr. John Bowman county of San Bernardino Environmental Public works Agency Land Management Department 385 N. Arrowhead Avenue San Bernardino, CA 92415

Dear John:

i c- GEORGE DEUKMEJIAN, Governor

June 26, 1986

This is to acknowledge receipt of the following reports submitted with your letter of June 20, 1986:

Engineering geology investigation, First Southern Baptist Church, Joshua Tree, CA; by Rasmussen & Associates; March 20, 1975 (Project No. 1095).

Engineering geology investigation, Sunset Village, Joshua Tree, CA; By Rasmussen & Assoc.; Nov. 1, 1977 (Project No. 1265); with update of March 20, 1986.

These reports will be filed informally, as we have not yet established Special studies zones for the Pinto Mountain fault. However, it is our intention to zone this fault, based on the work of Bill Bryant whose data are summarized in our Fault Evaluation Report 181. A copy of a portion of Figure 3C from this report is enclosed for your reference, although the report is not yet approved for general release. You will note that our mapped trace is in close agreement with Rasmussen's trench exposure (his report of No_v. 1, 1977).

Sincerely yours,

Earl w. Hart Senior Geologist &

Program Manager

KENNElll C. TOPPING Deputy Administrator Development Services

June 20, 1986

ENVIRONMENTAL PUBLIC WORKS AGENCY

LAND MANAGEMENT DEPARTMENT 385 N. Arrowhead Avenue, San Bernardino, CA 92415

Mr. Earl W. Hart, CEG 935 Senior Geologist & Program Manager Division of Mines & Geology 380 Civic Drive, Suite 100 Pleasant Hill, Ca 94523-1997

JOHN N. JAQUESS Land Management Director

OFFICE OF PLANNING County Planning Officer

OFFICE OF SURVEYOR Claude D. Tomlinson, LS.

County Surveyor

OFFICE OF BUILDING AND SAFETY Larry L. Schoelkopf, P.E. County Building Official

SUBJECT: ALQUIST-PRIOLO SPECIAL STUDIES ZONE REPORT SUBMITTAL

1. In compliance with the policies of the State Mining and Geology Board, please find enclosed one copy of geologic report entitled:

ENGINEERING GEOLOGY INVESTIGATION, SUNSET VILLAGE, JOSHUA TREE, CALIFORNIA, DATED NOVEMBER 1, 1977, PROJECT NO. 1265 BY GARY RASMUSSEN & ASSOC.

GEOLOGIC UPDA'I'E & GEOLOGIC REIVEW OF GRADING PLAN DATED 12/85 BY GARY RASMUSSEN & ASSOC.

2. I have reviewed and approved this report finding that it meets the policies and criteria of the State Mining and Geology Board and satisfies the requirements of the Alquist-Priolo Special Studies Zone Act.

Sincerely,

JCB/jlo

enclosure

!lO!l;:RT I!. Rlf;~EV County Adn11ni:.1rati\e Officer

,J.l\C'.( F. Pl·1>UV. Admini<itra1or I nvn0•11n\:ntal Public \Voi k<: Ag~ncy

3ourd of Supcrvl'lur ...

.JOJ-L'\ JOY~.ER .... .......... . !·'i;..,t Dhtrict B/\ft4:AR<\ ('rt.Ai\'i H:IORDA~ .... Third Dislri('t CAL McEI,\VAl:\ . . . . ..... . Second Hbtricl R-OllEH:T (). TO\\';..iS.E'\!f) ..... . f'ourth lli<:trkl

!J.:(}!11·~~.r, llA.\ii:!vl(}!:.:t( .......... . .Fifth Dislricl

UNITED STATES DEPARTMENT OF AGRICULTURE F"ARMERS HOME ADMINISTRATION

459 Cleveland Street Woodland, California 95695

• Mr. Stephen M. Kerpen Peoples Housing Incorporated Post Office Box 516 Topanga, California 90290

• March ll, 1977

Subject: Morongo Basin Retirement Housing Association - Sunset Village Joshua Tree, California

•

Dear Mr. Kerpen:

According to a registered geologist report by Gary S. RaBllIUssen and Associates, dated March 20, 1975, there are two earth quake faults

5 r>;;.. ,,-- through the 10 acre site just south of the Baptist Church along c C?-'1- Sunset Road, selected for your project. Because o·f this, the site

does not meet the requirements of FmHA for building purposes.

The next 10 acre parcel, south of a more perferable building site. FmHA requirements.

the parcel in question, would be It could be approved as meeting

Sincerely,

~~-~----/--:;, DOUGLAS W. YOUNG State Director

Far1ners Ho1ne Ad1ninistration i1 an Etjual Opportunity Lender. Co111plaints of racial or ethnic di1cri111ination should bt sent to:

Secrttary of Agriculture, IVarhington, D.C. 20250

/

/

. . ilt ·oY~.'1 ·.PEOPLES ~-. HOUSING

ARCHITECTURE · PLANNING RESEARCH

INCORPORATED 1424 OLD TOPANGA CANYON ROAD P.O. BOX 516 TOPANGA, CALIFORNIA 90290 TEL. 213 4!15-1348

April 4, 1977

Mr! John C. Rosebraugh Chief Building Inspector San Bernardino County Deparhnent of Building and Safety 1111 E. Mill Street San Bernardino, California 92415

REF: Sunset Vi II age tv'\orongo Basin Retirement Housing Association Joshua Tree, California

• Number 615-62

Dear Mr. Rosebraugh:

As we discussed on the telephone, and in answer to Item no. 5 of your inter-office memo dated March 8, 1977 (No. 615-62), I am enclosing the following documents:

An Engineering Geology Investigation of the First Southern Baptist Church in Joshua Tree located north of our proposed parcel and indicating two earthquake faults also north of our parcel and in the parcel south of the church.

2. A letter from the Farmers Home Administration stating that the parcel with the earthquake faults would not be acceptable, but that the parcel south of that one, which is our proposed parcel, would be acceptable.

3. A property location plat showing the location of these parcels.

If you have any questions, please call us.

Sincerely,

~L Wl. \(~...._" _ Stephen M. Kerpen

SMK/sc Enclosures

/

I cc: Rev. Robert G. O' Kane, President, Morongo Basin Retirement Housing Assn. STEPHEN M. KERPEN DAVID MARSHALL SHARLENE BELANGER

I I I I I I I I I I I I I I I I I I

GARY S. RASMUSSEN & ASSOCIATES /ENGINEERING GEOLOGY

1811 SO. COMMERCENTER WEST • SAN BERNARDINO, CALIFORNIA 92408 • l714) 888·2422 ° C714l 825-9052

ENGINEERING GEOLOGY INVESTIGATION SUNSET VILLAGE

JOSHUA TREE, CALIFORNIA

November 1, 1977

Project No. 1265

Prepared for

Morongo Basin Retirement Housing Association P.O. Box 458

Joshua Tree, California 92252

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Sunset Village Joshua Tree, California

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Geology after Dibblee, 1967 !"~approx. 1 mile Project No. 1265

-2-·- ~ . ,

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. Gary s: Rasmussen & Assoc:'iates, Inc.·

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I I I I I I I I I I I I I I I I I I I

GARY S. RASMUSSEN & ASSOCIATES /ENGINEERING GEOLOGI'

!560 NO. ARROWHEAD AVENUE. SUJTE 7 • SAN BERNARDINO. CA 92401

November 1, 1977

Morongo Basin Retirement Housing Association P.O. Box 458 Joshua Tree, California 92252

Attention: Reverend Robert G. O'Kane

• TELEPHONE ( 714 > 888·2422

Project No. 1265

Subject: Engineering Geology Investigation, Sunset Village, ElO Acres of 5~ of NE ~. Sec. 26, TIN, R6E, Joshua Tree, California.

An engineering geology investigation of a 10-acre parcel located 1320 feet

north of the centerline of Twentynine Palms Highway has been conducted at

your request. The 660' X 660' parcel is located on the west side of Sunset

Road, west of the intersection of Sunset Road and Morningside Road, in Joshua

Tree, California. The approximate location of the site is shown on the

geologic index map on page 2. We understand the site will be developed as

a retirement housing project for the elderly and will include apartments

of single-story, wood-frame construction. In addition, numerous parking

areas and landscaping are proposed. The southerly portion of the site is

not to be utilized as it is within a lower elevation that may be subject

to flooding. A 30-scale plot plan showing the proposed development of the

site and the proposed grading was prepared by Peoples Housing, Inc., Architects,

and dated August 19, 1977. The project dimensions and location of our sub

surface trench are shown on the 100-scale plot plan (Enclosure 1).

The site does not lie in an Alquist-Priolo Special Studies Zone and has

not previously been specially designated as a major geologic hazard zone

by the State. However, we understand the Pinto Mountain fault, which crosses

in the immediate vicinity, may eventually be included within the Special

Studies Zone, depending upon man power and budgeting by the State. The

Pinto Mountain fault is shown on the Seismic Safety Element to the San

Bernardino County General Plan as a potentially hazardous feature, and it

has previously been considered a hazardous fault in investigations for

nuclear reactor sites in the eastern Mojave Desert. The location of the


Morongo Basin Retirement Housing-Sunset Village-Joshua Tree Project No. 1265 November 1, 1977

Pinto Mountain fault was previously identified by us based on topographic

features, in our report dated March 20, 1975 for the First Southern Baptist

Church, located north of the proposed Sunset Village. In addition, the

Pinto Mountain fault was identified in our report dated June 24, 1975.

We understand, as a result of our investigation for the church north of

the site, the Sunset Village project was subsequently moved farther south

in order to avoid the Pinto Mountain fault. When contacted by Peoples

Housing with regard to the location of the Pinto Mountain fault, we

recommended that the northwest corner of the project be trenched as there

was a reasonable possibility that the Pinto Mountain fault passed through

the northwest corner of the site due to the trend of the fault and based

on the surficial expression of the fault in the vicinity as identified

in the March 20, 1975 report. Therefore, in accordance with our verbal

recommendations, we proceeded with a subsurface geologic investigation of

the site in order to precisely locate the Pinto Mountain fault and to

determine the maximum extent of previous surface rupture along the fault

in this vicinity so that human occupancy structures would not be placed

across any active traces of the Pinto Mountain fault.

SITE INVESTIGATION

A geologic field reconnaissance of the site and surrounding area was con

ducted during October, 1977. In addition, a single backhoe trench was

excavated in a north-south direction from the northwest corner to deter-

mine if any· traces of the Pinto Mountain fault passed through the site and

to precisely locate it so that human occupancy structures would not be

placed across any active fault traces. Our initial investigation indicated

the Pinto Mountain fault passed very near or just north of the northwest

corner of the site. No evidence of any active faulting through the remain

der of the site was found in the field or mentioned in the literature,

therefore, only the northwesterly portion of the site was investigated by

subsurface trenching. The trench was excavated in a manner that would

-3-

GARY S. RASMUSSEN & ASSOCIATES



intercept any east-west-northeast trending faults passing through that

portion of the site where other geologic and geophysical data indicated

the presence of a fault may exist. The trench walls were examined in

detail for evidence of faulting, and a major trace of the Pinto Mountain

fault was encountered at the extreme northwest corner. In addition to the

subsurface trench and geologic reconnaissance, our investigation included

review of stereoscopic aerial photographs flown in 1952, 1964, and 1971;

review of pertinent geologic literature and maps; and review of significant

seismic information. A list of references is enclosed.

The site was free of man-made structures at the time of our investigation.

Numerous mature Joshua Trees and cactus were growing on the site. The site

was essentially in its native state and had not previously been disturbed

by man, except for the dirt road along the south property line.

SITE GEOLOGY

The site is located in the east 10 acres of the south ~ of the northeast ~

of Section 26, TlN, R6E, San Bernardino County, California. The site is

located within an east-west valley with igneous and metamorphic bedrock

highs located to the north and south. The northerly three-fourths of

the site slopes downward toward the southeast at a rate of approximately

5 percent while the southerly one-fourth of the site slopes downward

toward the east at.a rate of approximately 3 percent. The northerly

portion of the site is characterized by a broad east-west ridge classified

as older alluvium. Holocene or younger alluvium occupies the major

drainages within the valley and occurs in the extreme southerly portion of

the s~te, where the east flowing drainage exists.

The older alluvium is probably late Pleistocene to early Holocene in age

and is a poorly consolidated, fine to coarse sand with occasional cobbles.

This unit was well exposed in our trenches and observation of the trench

walls indicate the materials on the north side of the Pinto Mountain fault

-4-GARY S. RASMUSSEN & ASSOCIATES



are significantly older than the materials on the south side of the fault

on this site. The older alluvium north of the Pinto Mountain fault has

been deformed and tilted, probably as a result of continued tectonic

movement along the Pinto Mountain fault, whereas the sands south of the

fault were not deformed or tilted. The sands were moderately well bedded

and it was relatively easy to identify bedding and separate units.

The younger alluvium occupies the east flowing drainage located in the

southerly portion of the site. The younger alluvium is Holocene to historic

and contains loose, fine to coarse sands. These sands have been deposited

by flooding and heavy runoff along the drainages which drain the nearby

mountains to the south. Most of the area covered by the younger alluvium

has been subject to flooding in the not-too-distant past.

The exact depth to bedrock on the site is not known. Wells in the vicinity

have encountered older alluvium to their maximum depth of approximately 800

feet. Wells exist on the south side of the Pinto Mountain fault and the

depth to bedrock south of the Pinto Mountain fault is expected to be

significantly deeper than the depth to bedrock north of the fault. However,

several hundred feet of alluvium very likely exists on the north side of

the Pinto Mountain fault.

SEISMIC SETTING

The east-west trending Pinto Mountain fault zone is the most significant

tectonic feature in the area. Prior to this investigation, there was

some question as to the exact location of the Pinto Mountain fault in the

Joshua Tree area. Six miles east of the site, the Pinto Mountain fault

location is marked by prominent alignments of vegetation and linear ridges

of older alluvium. From that point east, the Pinto Mountain fault can be

followed continuously as it disrupts older alluvium and younger alluvium

to its eastern terminus, east of Twentynine Palms. The fault has been




observed by us in older alluvium and younger alluvium for an investigation

on the proposed Junior College. The evidence for the exact fault location

from the site to Copper Mountain, 6 miles east of the site, is scarce to

non-existent.

Previous geologic mapping by others in the vicinity has placed the Pinto

Mountain fault along the south base of the mountains approximately !2 mile

north of the site (Dibblee, 1967, CDMG, 1966). Some ground water investi

gations have placed the Pinto Mountain fault farther to the south and, in

some older reports, it has been referred to as the Baseline fault. The

Pinto Mountain fault was identified at the approximate location shown on

the index map on page 2 as a ground water barrier (Bader, 1958). Subsequent

reports have placed the Pinto Mountain fault farther north along the base

of the bedrock hills.

Previous mapping of the Pinto Mountain fault for the referenced reports by

this firm. together with geophysical data, indicated the Pinto Mountain

fault was located at approximately the northwest corner of the site with

a nearly east-west trend. The Pinto Mountain fault has not been previously

trenched in this vicinity and the age of most recent faulting or offset

bedding is not known. However, Holocene alluvium has been offset or

disrupted by the Pinto Mountain fault in the Twentynine Palms area and has

had historic seismic activity along it. In addition, a recent investigation

by this firm at the juncture of the Pinto Mountain fault with the Mission

Creek fault (branch of the San Andreas fault) indicates the Pinto Mountain

fault at that point exhibited more evidence of Holocene movement than did

the Mission Creek fault. Because of the obvious location of the Pinto

Mountain fault in Holocene alluvium to the east, the ground water barrier

effect in Holocene alluvium in the Yucca Valley area, and the historic

seismic activity, it is considered to be an active fault.

The exact age of sediments trenched for this investigation is not known

as no datable material was found. The sediments are shown as older alluvium

-6-




of probable Pleistocene age by Dibblee. The deformation of the bedding ' north of the fault and amount of caliche-filled cracks suggest the sediments

immediately north of the Pinto Mountain fault are probably of late Pleisto

cene age. The sediments south of the fault were not noticeably deformed

and the bedding generally followed the slope of the existing ground surface.

Therefore, these sediments are probably significantly younger than the

sediments immediately north of the fault. These sediments south of the fault ·--·---......... '~~~:_to be Holocene in age (11,000 years or younger).

Numerous other active and potentially active faults are located in the

general region. The Mission Creek fault, a branch of the San Andreas

fault zone, is approximately 17 miles to the southwest. The northwest

trending Johnson Valley, Camprock-Emmerson, and Calico-Mesquite faults are

all located within 20 miles of the site. All of these northwest trending

faults are considered potentially active or active and terminate at or

near the Pinto Mountain fault on the southeast (except the Mission Creek

fault). The termination of these active northwest trending faults by the

east-west Pinto Mountain fault is further indication that the Pinto

Mountain fault is an active and major through-going fault.

PINTO MOUNTAIN FAULT

The Pinto Mountain fault is generally considered to be a strike slip fault

with left-lateral movement. Some dip slip movement has also taken place,

but to a lesser degree than the strike slip movement. T.W. Dibblee shows

the Pinto Mountain fault at the base of the bedrock mountain, north of

Hilltop Drive in Joshua Tree, California. However, a close field recon

naissance of that area and review of the aerial photographs for this inves

tigation failed to find any evidence or suggestion of faulting at that

location. Magnetometer surveys have been conducted by this firm at both

the location of the Pinto Mountain fault, as proven by trenching for this

investigation,and at the location of the fault shown by Dibblee. No anomaly




was recorded at the base of the mountains where Dibblee shows the fault,

however, an anomaly was encountered at the location of the Pinto Mountain

fault where it offsets the older alluvium. Unfortunately, topography has

a major impact on the magnetic readings and the anomaly recorded at the

location of the Pinto Mountain fault could also be attributed to the topo

graphic change, which was rather large at that location, rather than

faulting. In light of our current investigation, which exposed the Pinto

Mountain fault at the location where the magnetic anomaly occurred, it

seems likely that the magnetic anomaly is due to faulting with possibly

some influence from the topography.

A strong lineation can be followed for several miles in the older alluvium

west of the site. This lineation is, in fact, the actual location of the

Pinto Mountain fault, based on trenching for this investigation, ground

water data, fracturing of the older alluvium observed parallel to the linea

tion as observed in the north-south drainages in the immediate vicinity,

and a magnetic anomaly at the exact location of the. lineation. The Pinto

Mountain fault is only shown at this location in one previous report by

J.S. Bader in his ground water study of the area in 1958. Subsequent

reports failed to show the Pinto Mountain fault at this location.

The Pinto Mountain fault offsets the ground water table in the Joshua

Tree area with the water table being 100 to 170 feet higher on the south

side of the fault (Lewis, 1972). Ground water information in the area

was diligently searched for another investigation by this firm to try and

pinpoint the location of the fault in the Joshua Tree area. Unfortunately,

only one well was found in a narrow strip of land between the fault shown

in this report and the location shown by Dibblee to the north. That well,

1N6E, 25Cl, was abandoned and capped. No information was found in the

literature on this well other than a listing in the 1958 ground water

study. The abandoned well was sounded by a technique, described by Stewart,

1970. This crude sounding method indicated the well is currently dry,

-8-




with a total depth of approximately 350 feet.

of the fault should be approximately 400 feet

The ground water table south

deep and it should be deeper

to ground water north of the fault. Therefore, the well may have been

dry originally.

Ground water information found for wells approximately 2~ miles west of

the site proved useful in further identifying the barrier effects of the

Pinto Mountain fault. The Pinto Mountain fault can be followed as a linea

tion to a point just east of those wells. The linear ridge of older

alluvium where those wells are, lines up exactly with the lineation observed

for the Pinto Mountain fault for this investigation. An apparent offset

of the water table of 81 feet exists between wells 1N6E, 28Ll, and 28Nl.

An apparent offset of 153 feet exists between wells 1N6E, 29J2 and 29RW.

This suggests that the fault lies between those points and is at the

location of the lineation where the linear ridge occurs in older alluvium

west of the site, and passes through or just northwest of the northwest

corner of the site. Based on the results of previous investigations

conducted in the area by this firm and obvious faulting observed within

the trench at the extreme northwest corner of the_ site, the exact location

of the Pinto Mountain fault has been conclusively proven to exist approxi

mately ~ mile farther south than shown on most of the published geologic

literature. Although another paratlel fault may exist along the base of

the mountains~ mile north of the site, it does not seem likely, as no

evidence for a fault at that location has been found.

The total width of the fault zone is not known as our trenching was

confined to the property owned by the Morongo Basin Retirement Housing

Association. The southerly limits of the fault zone have been adequately

defined by our trench, as numerous parallel fault traces were observed in

the trench. What appeared to be the major or largest offset along a

single trace was staked in the field so that the precise location of the

fault could be recovered for placement on the final development map. The

trench log (Enclosure 5) shows the details of the deformed bedding and fault

-9-

G.ARY S. RASMUSSEN & ASSOCIATES



traces observed in the trench. The major fault trace, as measured in the

trench, has a strike or trend of approximately north 82 to 87 degrees

east. The strike or trend of the lineation observed on the aerial photo

graphs is approximately north 82 to 86 degrees east. The main fault plane

observed in our trench dips or is inclined approximately 75 degrees to the

north. The sediments north of the fault were generally deformed and folded

with their strikes approximately parallel to the Pinto Mountain fault and

generally dipping to the south approximately 32 degrees. South of the fault

zone the bedding was generally parallel to the existing ground surface,

and the sediments were not deformed.

Of critical importance to siting human occupancy structures on or near

a fault is the fault's state of activity. A clearly inactive fault can

be built across with very little chance the fault will move significantly

during the life of the structure. An active fault, on the other hand,

has a relatively high chance of undergoing surface rupture within the

life of a human occupancy structure. In order to more precisely define

fault rupture hazards, the State has defined three states of activity for

faults. The following definitions are excerpted from the California

Division of Mines and Geology Special Publication 42 (see enclosure).

"For purposes of delineating Special Studies Zones, any fault considered

to have been active during Quaternary time (last 2 to 3 million years)-

on the basis of evidence of surface displacement--is considered by the

State Geologist to be potentially active. An exception is a Quaternary

fault which is determined, from direct evidence, to have become inactive

before Holocene time (approximately the last 11,000 years). Such faults

are presumed to be essentially inactive and most have been omitted from

the map. The State Mining and Geology Board, in their Policies and

Criteria (adopted 21, November 1973), defined only those faults which

have had surface displacement within Holocene time as 'active and hence

as constituting a potential hazard'."

-10-

GA.RYS. RASMUSSEN & ASSOCIATES


Morongo Basin Retirement Housing-Sunset Village-Joshua Tree Project Na. 1265 November 1, 1977

SEISMIC HISTORY

Numerous earthquakes with Richter magnitudes up to 5.0 have occurred within

a 20-mile radius of the site during historic time, Many of these appear

to be related ta the Pinto Mountain fault, others appear ta be related ta

the northwest trending faults of the Mojave Desert. The largest historic

earthquake in the area was the Desert Hat Springs earthquake in 1948.

This Richter magnitude 6.5 earthquake occurred along the Mission Creek

fault, a branch of the San Andreas fault zone, and had an epicenter less

than 20 miles from the site.

Numerous earthquakes have been associated with the Pinta Mountain fault

historically. The accuracy of assigning earthquake epicenters is not always

sufficient to determine what fault, if any, they are associated with.

The largest historic earthquake that may have been associated with the

Pinta Mountain fault had a Richter magnitude of 5.9 and was located more

than 30 miles to the east.

SEISMIC ANALYSIS

Significant earthquakes affecting the site may occur on any of the faults

that have been mapped in the general area. However, because of its close

proximity to mast of the site and through it, and its active classification,

the Pinto Mountain fault is probably the mast significant ta the site from

a ground shaking standpoint. Although a larger maximum probable earthquake

is expected along the San Andreas fault zone, the effects on the site should

be no mare severe than from an earthquake along the Pinto Mountain fault

because of the much greater distance ta the San Andreas fault zone.

Recorded information an ground accelerations caused by earthquakes and

maximum probable earthquakes has not been available in sufficient quantity

ta precisely predict earthquake magnitudes or ground accelerations from

a statistical standpoint. However, based o.n the information available




at this time, a Richter magnitude 6.5 earthquake originating along the

Pinto Mountain fault should be expected (at least 50 percent chance of

occurrence in the next 100 years). An earthquake of this magnitude and

distance from the site (on-site) can be expected to produce maximum peak

ground accelerations in bedrock under the site of approximately 0. 7g.

This acceleration should not necessarily be used as a design value as it

is a peak acceleration and is estimated for bedrock, which is more than

800 feet deep. The peak acceleration should be considered an aid in the

evaluation of the structural design of structures. Additional information

on the site response during shaking can be provided if requested.

We have discussed the seismic shaking aspect of the site with David Chavez,

Structural Engineer for the project. In accordance with the results of

this discussion of the geology with respect to the type of structures

proposed for the site, we concur that a design acceleration of 0.20g is

appropriate for the proposed single-family, wood-frame structures to be

placed on the site.

FLOODING

Flooding is expected on the major east flowing drainage located in the

extreme southerly portion of the site. No structures are currently planned

in this area. The amount of peak flow during a flood should be deter

mined and the proposed structures protected from normal flood hazard.

This has apparently already been done as no structures are proposed within

the lower elevations of the site.

CONCLUSIONS

The southerly portion of the active east-west trending Pinto Mountain fault

passes through the extreme northwest corner of the site as shown on the

enclosed 100 and 130-scale maps (Enclosures 1 and 2). Holocene alluvial

-12-0ARY S. RASMUSSEN & ASSOCIATES



sediments (estimated to be of Holocene age on the south side of the Pinto

Mountain fault) have been offset by faulting, therefore, the Pinto Mountain

fault is considered to be a potential hazard to human occupancy structures

and capable of surface rupture in the near future. Human occupancy

structures should not be placed across the fault zone and should be setback

a minimum distance of SO feet from the locations of previous fault rupture

as determined in our subsurface trench.

Severe seismic shaking of the site can be expected within the next 100

years.

Earthquake induced flooding of the site is not likely as no significant

reservoirs are located at higher elevations and as the site is generally

situated above two major east flowing drainages, to the north and to the

south.

The sandy materials encountered on the site are considered to be highly

susceptible to erosion.

The site is subject to occasional windblown sand and dust storms.

Liquefaction and other shallow ground water related hazards are not

expected due to the depth to ground water under the site.

RECOMMENDATIONS

Human occupancy structures should not be placed across any of the traces

of the Pinto Mountain fault and should be setback a minimum distance of

50 feet south of the fault, as shown on the enclosed 100 and 130-scale

maps (Enclosures 1 and 2). This results in a minimum recommended setback

to the south of 86 feet from the stake placed in the field by our firm

and as surveyed by Warner Engineering. The proposed plans, as shown by




by Peoples Housing on their plot plan dated August 19, 1977, show the

northerly most building for human occupancy to be just south of the minimum

recommended setback zone, therefore, no changes in building locations are

proposed as a result of the Pinto Mountain fault passing through the

extreme northwest corner of the site.

The effects of expected seismic shaking as developed in the section on

Seismic Analysis should be taken into consideration during design and

construction of the proposed human occupancy structures. A design

acceleration of 0.20g seems appropriate for the proposed structures as

discussed with the structural engineer.

Maximum cut slope inclinations should be no steeper than 2 horizontal to

1 vertical as the materials are highly susceptible to erosion. Positive

drainage of all building pads should be provided and runoff should not be

allowed to flow over cut slopes.

Respectfully submitted,

GARY S. RASMUSSEN & ASSOCIATES, INC.

//tUy/~ Gary S. Rasmussen Engineering Geologist, EG 925

GSR/mt

Enclosure 1: 100-scale map Enclosure 2: 30-scale map Enclosure 3: Alquist-Priolo data Enclosure 4: References Enclosure 5: Trench logs

Distribution: Peoples Housing, Steve Kerpen (3) Morongo Basin Retirement Housing Association, Robert G. O'Kane (3)

-14-


0

- - -Gary S. Rasmussen Blue flagged

lath

ENCLOSURE 1 Sunset Village ..

- - -& Associates Orange flagged lath showing

fault trac

4c"

Joshua Tree, Californi<

so 100

Scale 1"=100'

200 feet

_._Prope..-ty boundary

- - - - - - - - - - ••1 South extreme of fault surface rupture Note: North extreme was not determined

NB3E

. . f Restricted south Limits o ded in this use zone Recommen

Report

PINTO !1)1.fill\lN Fl\Ull ZONE

Property __ _.. boundary

"" "' 0 c: .... Q)

"' § Ul

- N-

~

1320' to centerline Twenty-Nine Palms Highway Route 62

- -,- - - - - - .. - -property corner

of fault h extreme __.,.

sout ~

- 1· ---·

. d use , ,- f restr:i.cte south iimi~s i~ this r~ort .. recommende /

t ?.i(.,2,; \

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~ '2.?r,,o .... ......

:::--- ture surface ruP

----·-.. ..-

~\,, --- 1 :....~--~ '

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P-· 1---~ _,,..- .


REFERENCES

Bader, J.S., 1958, Data on water wells and springs in the Yucca ValleyTwentynine Palms area, San Bernardino and Riverside Counties, Califonlia, Calif. Dept. Water Resources, Bull. 91-2.

Dibblee, T.W., Jr., 1967, Geologic map of the Joshua Tree quadrangle, San Benlardino and Riverside Counties, Califonlia: U.S. Geol. Survey Misc. Geol. Investigations Map I-516.

Dibblee, T.W., Jr., 1968, Geologic map of the Twentynine Palms quadrangle, San Bernardino and Riverside Counties, Califonlia: U.S. Geol. Survey Misc. Geol. Investigation Map I-561.

Greensfelder, R.W., 1972, Crustal movement investigations in Califonlia: Their history, data, and significance: Calif. Div. Mines and Geology, Special Publication 37.

Hart, E.W., 1976, Fault hazard zones in Califonlia: Califonlia Div. of Mines and Geology, Special Publication 42.

Hart, E.W., 1976, Active fault mapping and evaluation progress, ten year program to implement Alquist-Priolo Special Studies Zone Act: Calif. Div. of Mines & Geology, Special Publication 47.

Hatheway, A.W., 1975, Terminus of the Pinto Mountain fault, near Twentynine Palms, California in Geol. Soc. of America Abstracts with Programs, Cordilleran Sectio"i'i"7lst Annual Meeting.

Hileman, J.A., Allen, C.R., and Nordquist, J.M., 1973, Seismicity of the southern California region, 1 Jan 1932 to 31 Dec 1972: Seismal. Lab., Calif. Inst. of Tech., Pasadena, California.

Jennings, C.W., 1975, Fault map of Califonlia with locations of volcanoes, thermal springs and thermal wells: Calif. Div. of Mines and Geol., 1:750,000.

Lamar, D.L., Merifield, P.M. and Proctor, R.J., 1973, Earthquake recurrence intervals on major faults in southenl California, in Moran, D.E. and others, eds., 1973, Geology, seismicity and environmental impact: Assoc. Eng. Geol., Special Publication, pp. 265-276.

Lewis, R.E., 1972, Ground water resources area, San Benlardino County, Califonlia: Division, Open-file report, 51 p.

of the Yucca Valley-Joshua Tree U.S. Geol. Survey, Water Resources

Proctor, R.J., 1968, Geology of the Desert Hot Springs-Upper Coachella Valley area, California: Calif. Div. Mines and Geology, Special Report 94.

i GARY S. RASMUSSEN & ASSOCIATES


Gary S. Rasmussen & Associates, March 20, 1975, Engineering geology investigation of proposed First Southern Baptist Church parcel, Sunset Road and Scenic Road, Joshua Tree, California, Project No. 1095.

Gary S. Rasmussen & Associates, June 24, 1975, Preliminary engineering geology investigation, Joshua Tree Development, a portion of the E~, Sec. 25, TIN, R6E, Joshua Tree, California, Project No. 1110.

Richter, C.F., Allen, C.R., and Nordquist, J.M., 1958, Desert Hot Springs earthquakes and their tectonic environment: Seismal. Soc. America Bull., v 48, no. 4, pp 315-337.

Rogers, T.H., 1966, Geologic map of California, Olaf P. Jenkins edition, Santa Ana Sheet: Calif. Div. Mines and Geology.

Rogers, T.H., 1967, Geologic map of California, Olaf P. Jenkins edition, San Bernardino Sheet: Calif. Div. Mines and Geology, scale 1:250,000.

Schnabel, P.B., and Seed, H.B., 1973, Accelerations in rock for earthquakes in the western United States: Seismal. Soc. America Bull., v 63, no. 2.

Stewart, D.M., 1970, The rock and bong techniques of measuring water levels in wells: Ground Water, v. 8, no. 6, pp. 14-18.

ii GARY S. RASMUSSEN & ASSOCIATES

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GARY s. RASl·llJSSEN & ASSOCIATES - Sunset Village _.: -Project No; 1265

Logged by ELB

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Horizontal scale 1"=10' Vertical scale 1"=5'

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4 CALIFORNIA DIVISION OF MINES AND GEOLOGY SP 42

I CALIFORNIA DIVISION OF MINES AND GEOLOGY

PROGRAM FOR ZONING POTENTIALLY ACTIVE FAUL TS

/Requirements of the Act

The Alquist-Priolo Special S1udies Zones Act of 1972 (codified as Chapter 7.5, Division 2, of the California Public Resources Code) requires the State Geologist to

1 .. "Delineate, by December 31, 19~3. appropriately wide special studies zones to encompass all potentially and recently active traces of the San Andreas, Calaveras, Hayward. and San Jacinto Faults, and such other faults ... that ... constitute a potential hazard to structures from surface faulting or fault creep"'.

2. Compile maps of special sludies zones and submit such maps to affected cities, counties, and slate agencies by 31 December 1973, for their review and comment. Following appropriate reviews, lhe State Geologist must provide "official maps" to the affected cities, counties, and state agencies.

The State Geologist also is required to "continually review new geologic and seismic data .. in order to revise the special s1udies zones or delineale additional zones.

The Act also requires Cities and Counties to exercise specified approval authority with respect to real estate development or structures for human occupancy v.•ithin lhe special studies zones. Further it requires specific Policies and Criteria to assist local jurisdictions in administering the Act from the State Mining and Geology . Board.

Program for Zoning Potentially Active Faults

As required under the Act, the State Geologist (Chief of the California Division of Mines and Geology) established a program starting early in 1973 to delineale special studies zones to encompass traces of potentially and recently active faults in California and to compile and distribute maps of 1hese zones. A project team, headed by this writer, was established wilhin the Division to develop a program for delineation of the zones. ·

Initially, 175 maps of special studies zones were compiled for the San Andreas, Calaveras, Hayward, and San Jacinto faults. These zone. maps, issued as Preliminary Review Maps, were distributed for review by local and State government agencies on December 31, 1973. Following needed revisions as prescribed by l~w. Official Maps were issued on July I, 1974. At thal time, the special studies zones became effective and im. plementation was required by the affected Cities and Counties,

A_ second set of zone maps v.·as issued subsequently to delineate new and revised zones-Preliminary Review Maps on July I, 1975, and Official Maps on January I, 1976. Zones delinea1ed as part of this second issue.are sho_:.vn on about 81 maps of new zones and 5 maps of revised zones. It is expecled that additional Official

Maps of new and revised zones will be bsued each year on January I following issuance of a Preliminary Review Map on July I of 1he preceding year.

As of January I, 1976, approximately 256 Official Maps of special studies zones have been issued and presenlly are in effect. These maps are iden1ified by name on the Index to Maps of Special Studies Zones. The maps delineate zones for 1hose faults identified in figure I. Approximately 23 Counties and 58 Cities are affected by the existing special studies zones. These Counties and Cities are listed elsewhere in this report.

Faults zoned to dale by the State Geologist are identified on figure I. Addilional faults to be zoned in the near future include the Sierra Madre, Cucamonga, Raymond Hill, and Elsinore faults in southern California. There are many other faults in California that are potentially active (Jennings, 1973). and some of these may be zoned if delermined 10 be '"sufficiently active and well-defined as to constitute a hazard" (Chapter 2622 of 1he Act). As in the past, future zoning will be done on a priority basis depending on the availability of boih data and funds. ·

Delineating the Special Studies Zones

Special s\udks zones are delineated on topographic base maps at a scale of I :24,000 (I inch equals 2000 feet). The zone boundaries are straight-line segments defined by turning points. Most of the turning points are intended to coincide with locatable features on the ground (e.g., bench marks, roads, streams). but neither these points nor the zone boundary lines between them have been surveyed in the field to verify their mapped locations. . · · · ·

The intent of the Alquist,Priolo Act is to provide for public safety from the hazard of fault rupture by avoiding, to the extent possible, the construction of structures for human_ occupancy astride hazardous faults. The faults shown on the special siudies zone maps are not precisely located on the maps, nor were 1hey surveyed in the field during this study. Their locations were laken from the best geologic maps and reports available, and plotted according to the best judgment and skill of the California Division of Mines and Geology's slaff geologist-compilers. The precise location and identification of hazardous faults within or near a zone of poientially active faults can be determined only 1hrough deiailed geologic site invesiigations. Thus, this Act es1ablishes the concept of a special studies zone-an area of limited extent centered on recognized faults-within which the danger of polential fault rupture is presumed to exist until shown otherwise by direct investigation. Potentially active faults other than those depicted on 1he maps, including branches. and spurs of the named faults, may be present within the special studies zones. The zone boundaries delimit

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6 CALIFORNIA DIVISION OF MINES AND GEOLOGY SP 42

the area believed by the State Geologist to warrant. special geologic investigations to confirm the presence or absence of hazardous faults. ·

Locations of special studies zone boundaries are con~ trolled by the position of the known traces of potentially active faults (defined below). However, the faults shown on ~e special studies zones maps were not field checked during the compilation of these maps. Because available fault data range widely in quality, and the locations of some faults are known imprecisely, the zone bqundaries are positioned at a reasonable distance (about 660 feet, or 1/8 mile) on both sides of the trace of the nearest potentially active fault. However, zone boundaries generally are more or less than 660 feet away from mapped faults because of I) curved or multiple fault traces. 2) the practical advantage in keeping the number of turning points .to a reasonable minimum, and 3) the quality of the data dictates a narrower or wider zone.

/

Definitions

Fault and Fault Zone

A fault is defined as a fracture or zone of closely associated fractures along which rocks on one side have been displaced with respect to those on the other side. Most faults are the result of repeated displacement which may have taken place suddenly and/or by slow creep. A fault zone is a zone of related faults which commonly are braided and subparallel, but may be branching and divergent. A fault zone has sjg_nificant width (with respect to the scale at which the fault is being considered, portrayed, or investigated), ranging from a few feet to several miles.

Fault Trace I

A fault trace is the line formed by the intersection of a fa tilt and the earth\ surface. It is the representation ofa fau~t as depicted on a map, including maps of the special studies zones. .

Potentially Active Fault

For the purposes of delineating special studies zones, any fault considered to have been active during Quaternary time (last 2 to 3 million years, figure 2}-on the baslS of evidence of surface displacement-is considered by the State Geologist to be potentially active. An exception is a Quaternary fault which is determined, from direct evidence, to have become inactive before Holocene time (approximately the last 11,000 years). Such faults are presumed lo be essentially inactive and most have been omitted from the maps. Although potentially active faults shown on .the maps may have been active during any part of, or throughout, Quaternary time, evidence for their recency of displacement commonly is incompletely preserved or equivocal.I Jn contrast, the State Mining and Geology Board, in their Policies and Criteria (adopted 21 November 1973), defined only those faults which have had surface displacement within Holocene time as "active and hence as constituting a potential hazard." :. ·

I In those cases where data arc available from field and aerial photographic investigations spccificaJJy directed at the problem of potential surface faulting, the po1en1ially active faults shown on the special studies zones maps may not be directly rclatable to the entire Quaternary Period. For example, the "recently active" rauh traces depicted on some U.S. Geological Survey maps arc believed to be predominantly of late Quaternary age and may exclude most rauhs that have become inactive during or prior to early Quaternary time.

'

GEOLOGIC AGE YEA.RS BEFORE

e,.

·u 0 ... 0 z 1l

Period Epoch

. -Hiuoric·

Holocene

QUATERNARY

Pkiuoce11e

Pliocene TERTIARY

pre.Pliocene

pre-CENOZOIC time

Btginnin1 of 1culugic 1imc 1

PRESENT (estimated)

200.

11.000

2.000.000 - 3.000.000-

7.000.000 - 10.000.000-

b~.000.000

I 4,tiOQ,000,000 t--

.,

}

Faults along which movement has occurred during this interval are defined as .cti111e ~ Policies and Criteria ol lhe Slale Miniog and Geology Board,

Faults defined as potentially active b the purpose of delineating special studies zones.

Figure 2. Geologic time scale

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1971> FAULT HAZARD ZONES IN CALIFORNIA 7 i

Uses and Limitations of Special Studies Zones Maps

The special studies zones arc delineated to define those areas within which special studies are required prior to building structures for human occupancy. Traces of potentially active faults are shown on the n1aps 1nainly to justify the locations of zone boundaries. These fault traces are plotted as accurately as the sources of data permit; yet the plots are not sufficiently accurate to be used as the .bases for set-back requirements, and they should not be so used.

The State Geologist has identified potentially active faults in a broad sense, and the evidence for potential activity of some faults may be only weak or indirect .

The fault information shown on the maps is not sufficient to meet the requirement for special studies. Local govern111ental units n1ust require the developer to evaluate specific sites within the special studies zones to determine if a potential hazard from any fault, whether

heretofore recognized or not, exists \vith regard to pro. posed structures and their occupants.

The surface fault ruptures associated with historic earthquake and creep events are identified where known. However, no degree of relative potential for future surface disp1ace1ncnt or degree of hazard is in1-plicd for the faults shown. Surface ruptures resulting from the secondary effects of seismic shaking during historic ti1ne are on1ittc<l fron1 the 111ap and do not serve as a basis for zoning.

Model Ordinance and Code

In order to assist the cities an<l the counties to in1plement the Alquist-Priolo Act, a suggested Model Ordinance and Code was written by James E. Slosson, former State Geologist. This publication is available from the Division of Min es and Geology, P.O. Box 2980, Sacramento CA 95812, for 25 cents plus tax.

SUMMARY OF POLICIES AND CRITERIA PURSUANT TO. THE ACT

Policies mid Criteria, called for in the Alquist-Priolo Act, were intially adopted on November 21, 1973, by the State Mining and Geology Board following. a review by all counties and incorporated cities in California. The Policies and Criteria were subsequently expanded and slightly revised July I, 1974, and June 26, 1975. Future revisions may be anticipated in order to assist the cities and counties in i111plc111cnting the Act.

Table 2. A summary of policies and criteria adopled by the State Mining and Geology Board. Complete text is in Appendix 8.

Pt>l.ICIES

I. Spccilics lhal 1h1.• Act is 11111 n..·1ru;u:ti\·c,

:!. SU!,'.s,csts llh.'thulls n.:foting 10 r1.•\-i\.'\\' of l1rcli111i11:1ry Maps prior In issua11..:c nf ()flici;1l Moips.

3. Pulkics anJ crih:ri:.a ;ippl) 11111) 111 :1n::i "ithin tlh.' spcci;1I SIUllics i'llUCS.

.i. l>cf'incs 1u·rin·_lj,,,/1 (1..·~u;1ls 111111.·111i;d ho1'01n.IJ ;i.s a fauh 1h;11 hi!.;, h;u.I surf;u:c lli..,placcnh,.'111 during ftulucl.'nl' 1in11." (l;ist 11.0tlO )"l'ilfS).

Sl'ECIFIC ("IUTl·.RtA

I. Nu s1ru1:1ur .. ·s rur hun1an 11ccup:incy arl.' p..:rn1i11 .. ·tl un th..: tract.: uf an ;n:th·c fault. (llnl..-ss pr11v..:11 11\hcn' isc. thl.' ;1rc;i within ~O rc .. ·1 uf <111 ac1iv..: f<1ult is prcsu1111.·1.l 111 h..: underlain h) ;111 :u:1ivc

1":1uh) .

H .. ·4uircs gc11l11gi..- r..-pun dirl·c11.·d ;11 th .. · pr11hl1.·n1 uf p111c111i:1I surfal.'l" f;1ulting fur ;ill projects dclincLI h) 1hc Acl (Scctiun ZtiZ 1.hJ .

3. l( .. ·4uir..:s th:it g'"·ul11gic r..:pons h'"• placcd on 11p..:n lilc hy the S1:1t1.· C i1.•• 1l1•i;is1.

-1. Kl·quir'-'' citi'"·s' ;111J cuuntic" tu re\ j._.,, :1dcqu;11.:) 11f g..:ulugk rcp••rts suh1nillctl ''ith r..:4uc-'1' f11r Lll·\·t•l••p111i:111 pi:rinit,.

'.\. P .. ·rinih ciiit·, ;uni l'.1tU1llic' lu c'tahli'h st:1nd;1nl' n11•fl.' r1.",tric· li\C 1'h:111 th'-' llnlicics ;111Ll 1.:ri11.·ri<1.

h. l>di111..·, (;1) ··11r11j1..·c1··. lhJ struc1ur1.· fur hu111;111 111.:cup;1ncy. ;111d (1.:l lh:'' r..-al '"·s1a1..: 1.l"''"'l••p1111..·nt.

GARY S. RASMUSSEN & ASSOCIATES /ENGINEERING GEOLOGY

1811 SO. COMMERCENTER WEST SAN BERNARDINO, CALIFORNIA 92408 • <714J 888-2422 • t714J 825-9052

March 20, 1986

Coup & Smith Architects Project No. 1265.l 400 Mary Avenue, Suite A Calexico, California 92231

Attention:

Subject:

Reference:

David A. Coup

Geologic Update and Geologic Review of Grading Plan Dated December, 1985 for Sunset Village Senior Housing, Joshua Tree, California.

Engineering Geology Investigation, Sunset Village, SE 10 Acres of NE 1/4 of SE 1/4, Sec. 26, TlN, R6E, Joshua Tree, California, November 1, 1977, Our Project No. 1265.

In accordance with your request, we have updated the referenced engineering geology investigation and reviewed the grading plans dated December, 1985 for the Sunset Village in Joshua Tree, California. As indicated in the r.eferenced engineering geology investigation, traces of the active Pinto Mountain fault traverse the extreme northwest portion of the property. The purpose of the geologic update was to address the potential significance of any new geologic information which may have become available since the date of the original investigation in 1977, particularly regarding the location and/or state of activity of the Pinto Mountain fault. The purpose of the grading plan review was to ensure that the recommendations made in the referenced engineering geology investigation of the site have been incorporated into the grading plan. The grading plan dated December, 1985, prepared by Warner Engineering at a scale of one inch equals 20 feet was used in our investigation. No field work was done for this investigation.

It is our understanding that the original site development plans used in the referenced engineering geology investigation have been dropped, and the proposed development shown on the grading plan dated December, 1985 is completely new. However, the boundaries of the site remain essentially the same with the exception of the extreme southeastern portion of the site. A wedge-shaped area in that portion of the site that was formerly included on the site has now been dropped and is not included in the grading plan dated December, 1985. A minor change has also

Warner Engineering March 20, 1986

GPR & Update Project No. 1265.1

occurred along the eastern property boundary associated with an easement for Sunset Drive. We understand that the site has not been developed in any significant way since the referenced engineering geology investigation of the site was conducted in 1977.

As indicated in the referenced engineering geology investigation, several apparently active traces of the Pinto Mountain fault were encountered in a trench placed in the northwestern portion of the property. Based on the results of that investigation, a restricted.use zone was placed in the northwest portion of the site (shown on Enclosure 2 of that investigation). Subsurface coverage of the entire site was not provided because t.here was no evidence observed in the field, on aerial photographs or in available literature that would suggest active faulting existed anywhere on the site except in the extreme northeast portion of the site. Subsequent geologic reports by this firm in the general area of the site (Rasmussen, June 5, 1980; December 7, 1981; February 17, 1982; February 7, 1985) and review of aerial photographs flown in 1952 have not revealed any evidence that would suggest active faulting exists on the site anywhere except where it was previously delineated in the referenced engineering geology investigation. Therefore, the boundary of the reconunended restricted use zone as indicated in the referenced investigation remains valid. Surface fault rupture on the site south of the reconunended restricted use zone, as shown on Enclosure 2 of the referenced investigation, is not expected during the lifetime of the proposed structures.

The referenced engineering geology investigation recommended that no human occupancy structures be placed on the site north of the restricted use zone as shown in that report. The grading plan dated December, 1985 indicates that all proposed structures will be south of, and outside the recommended restricted use zone.

The referenced engineering geology investigation indicated that flooding is expected in the major east-flowing drainage located in the extreme southerly portion of the site. Much of this area is no longer included within the site as shown on the grading plan dated December, 1985, and no development is currently scheduled for the southerly portion of the site; therefore, significant flooding of the site is not expected.

The grading plans for Sunset Village Senior Housing, dated

- 2 -GARY S. RASMUSSEN & ASSOCIATES

Warner Engineering March 20, 1986

GPR & Update Project No. 1265.l

December, 1985, as submitted, incorporate the geologic recommendations for site development as outlined in our initial investigation (Project No. 1265).

All of the other conclusions and reconunendations as indicated in the referenced engineering geology investigation remain valid and should be adhered to.

Please contact us if you have any questions.

JJM:GSR/rnn

Respectively submitted,

GARY S. RASMUSSEN & ASSOCIATES, INC.

h J· Ht.;L:... Jay J. Martin Staff Geologist

~.u;/4-..__ Gary s. Rasmussen Engineering Geologist, EG 925

Enclosure l: References

Distribution: Coup & Smith Architects (5) Warner Engineering (l)

- 3 -GARY S. RASMUSSEN & ASSOCIATES

Rasmussen, Preliminary 1/2, Sec. Bernardino

REFERENCES

Gary S. & Associates, Inc., June 5, 1980, Engineering Geology Investigation, 320 Acres, N 27, TlN, R6E, SBB&M, Near Joshua Tree, San

County, California, Project No. 1619.

Rasmussen, Gary s. & Associates, Inc., December 7, 1981, Preliminary Engineering Geology Investigation, 2 1/2 Acres, Southeast Corner of Cummings Way and Sunburst Street, Joshua Tree, California, TlN, R6E, Sec. 24, SBB&M, Project No. 1783.

Rasmussen, Gary S. & Associates, Inc., February 1 7, 1982, Preliminary Engineering Geology Investigation to satisfy the soils and geology requirements for Joshua Tree Properties Planned Unit Development, Joshua Tree, California, TlN, R6E, Sec. 33 SBB&M, Project No. 1796.

Rasmussen, Gary S. & Associates, Inc., February 7, 1985, Engineering Geology Investigation of the Proposed Faith Lutheran Church, Approximately 5 Acres, Located Immediately West of the Intersection of Chollita Street and Hallee Road, E 1/2 of the NW 1/4 of the SW 1/4 of the SE 1/4, Sec. 26, TlN, R6E, SBB&M, Joshua Tree, California, Project No. 2126.

United States Department of Agriculture, November 18, 1952, Black and white aerial photographs, Flight No. AXL-9K, photograph numbers 32, 33, 34, 56, 57 and 58, Scale: .

GA::RY S. RASMUSSEN & ASSOCIATES

division of mines and geology -...

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