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HomeMy WebLinkAboutTract Map 3883 Lot 147 Soils Report '., . . ..~~ ":..--- " < Los Angeles County Office: 155 West Avenue J-5 Lancaster, California 93534 (805)942-09911 Fax: (805) 723-3685 Orange County Office; 2615 Orange Avenue Santa Ana, California 92707 (714) 54&40511 Fax: (714)5464052 SOiL TEC:H, INC:. Geotechnical Engineering Special Material Environmental Engineering Geology Inspection Testing Assessments \\2-~5 L.d\" \~ 1 City of Temecula Department of Public Works 43174 Business Park Drive Temecula, CA 92590 May 14, 1996 Attn: Mr. Jim Faul, P.E. Re: Soils Report Single Family Residence 40285 Paseo Del Cielo LD 96-061 GR Dear Mr. Faul: Soil Tech Inc. has been retained by Bratene Construction to perform the Geotechnical Engineering for the proposed grading on the refereced 1/2 acre lot, located in the Meadowview area of Temecula_ It is our opinion that a Preliminary Soils Investigation is not necessary for the work proposed on this site. The history of the Meadowview area is one of well known, fairly consistent geotechnical characteristics, to the degree that an investigation would provide no new data and no recommendations for changes in the proposed grading procedures, or the design of the structure's foundation system, from the recommendations made in this letter. The earth materials underlying the area are known to consist of stable units of Pauba Formation sandstones and siltstones. The regional geology has been thoroughly mapped by Michael Kennedy, and presented in his "Special Report 131, Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, California", 1977, California Division of Mines and Geology. As clearly documented by Kennedy, the entire Meadowview area is underlain by units of the Pauba Formation, an interbedded succession of Late Pleistocene sandstone, siltstone and conglomerate. The results of geologic mapping by Kennedy are plotted on Plate 1 of the report, and a section covering the Meadowview area is attached for documentation. The presentation is one of nearly flatlying bedding with a low angle of dip[, ranging from 2 to 5 degrees, generally in the northwest direction. Jointing is generally vertical or near-vertical. Corporate Office Post Office Box 1568 . 41607 Enterprise Circle North . Temecula, California 92593 . (909) 676-2745 . FAX (909) 699-1757 \- . . These earth materials have historically been considered stable, and as evidenced by the absence of geotechnical instability problems in Meadowview, have performed with consistent reliability. Prior to the formation of the City of Temecula, the County of Riverside, then the controlling agency, recognized the documented stability of the area and did not require preliminary soils investigations for single home development in the Meadowview area. Based on the relatively simple grading proposed for the site, no unusual conditions are anticipated which cannot be mitigated during grading. The following grading recommendations are presented based on our familiarity with the area and the earth materials expected to be encountered: 1. All loose surface soils shall be removed to a minimum depth of 12 inches, or to a deeper depth if cosidered necessary in the field, prior to scarifying and placing fill materials. 2. A 1 O-foot wide key shall be excavated at the toe of the proposed fill slope. The key shall be excavated to a minimum depth of 2 feet and shall slope into the hillside. 3. Benches shall be cut into firm natural ground such that all fill is placed on level ground. 4. All exposed natural ground shall be scarified to a minimum depth of 6 inches, moisture conditioned as necessary, and recompaced prior to placement of fill. 5. All fill shall be brought to within 2% of optimum moisture content and shall be compacted to at least 90 percent of maximum density. Our representatives will be on the site to perform density testing and inspection to assure that the above recommendations are adhered to and to verify that the grading is being performed in an acceptable manner. A report of Rough Grading will be prepared upon completion of the grading and, if any design or construction recommendations are in order, they will be made in that report, and will be presented together with the results of density testing. The opportunity to address this matter, and your consideration of this request is greatly appreciated. If you have any questions regarding these issues, please don't hesitate to call. Respectfully Submitted, \ 2- . " ~ <( I- ill o I.- offi Za. illttJ co I- CJ) Ocr :Zo ,<( w a. >-0 ,ill 03 ,::S::: ..- ,~ LO ,<( ...... o ,- :0.. >- I- \ \ \ , \ \ \ \ \ \ \ \ \ \ ..../ -' U. '" % 2 ~ o Ww ..,..../ 0", 0:< ll.~ ::E::> ::>'" ::Eo..../ - < . x ~ c: <%w ::E>=~ -0< ';':o:E . o , w a: " '" ;;; ll. >- ~ ::EO 0:% -::> u.o 00: ~Cl %..../ -< :I: 0: 0::> %~ w< "'% J .. < w 0'" w< -,0 .... '" ...., gc >- o .. ww , oJ 0< II: 0 .." W ll. o ..../ en ..../ ..../ U. U. o W o ~ c .w enz en- w::E ..../0: o:~ Ow _0 U:;w '" en , -..../ ~..../ z< w:I: -en o <Cl o:z Cli wO c..zc:: OWW ..../"'w "'o:z WOe; :I:II-z ~>-w WI-en c:a;...J wCl'Jo :I:w., >=0 ww "%:1: W I- I-w O:I:> %~'" rl = '" 3> . . ATTACHMENTS FROM SPECIAL REPORT 131 Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, California Michael Kennedy 1977 California Division of Mines and Geology 4, 1977 . . ELSINORE FAULT ZONE-KENNEDY 5 Ilr30' *-:\-L 34000' , ,,-"- ...-.- \ r.J- ,I R..e"lde Counl, '- c~co'ono A~ , -9-9 '. <"~ ".s- >"~ " '11'~ \ " ' 4\---" "lA, ", r ' '~-4 .) ,cJSlnor~ 6. '41. '';<>v ~O~.... SECTION I I OVA. ~(l' Murriela \./1 I ..~ 0 ......----SECTION 2 33030'+"-'-" .q/1'.s- ~~g'~I~~~;O ",,~SECTION 3 . -. . Temeculo 0:-- Rodee " "". ':.e.c~r:'~ .1~!O!! .I!<!servalion ~~OI1 A~uTibio ,~~ Mounlains "'" 117" 00' + 10 0 20 40 50 Kilometers 10 30 .. . ~igure 3. Index map and columnar sections showing fossil localities Temecula Arkose in the,subsurface (figure 4). The maximum exposed thickness of the formation is estimated to be 75 mj though because of faulting. low relief. and the discontinuous oUll:rop pattern, this figure is questionable. . The formation is Composed mostly of pale greenish-yellow, medium-grained, friable, caliche-rich sandstone, which. in its northwesternmost part along the Wildomar fault zone. grades laterally and abruptly to a cobble-and--boulder conglomerate facies composed entirely of Ioca11y derived plutonic, ,metamorph- ic, and volcanic clasts set in a coarse-grained brown sandstone matrix. The composition and character of the conglomerate-- especially the abundance or quartz-bearing gabbro similar to that immediately east of the outcropping conglomerate near Wil- domar, steeply inclined,' west-dipping, crossbedded sandstone North Soutn - - ' - .~.-,- .... ..... ----------------- - - - - - - -- ~_:-~:~.~ , > > '~ . -.."... - -~ , > , , , > > , 1----- --I .- ----- - - - - - -- ------ r ~'I ,.... ~.'.'.- :....;....., ;..: .~.': r--q ;:,-;.-1 pauba Formation. (upper Pleistocene) Unnamed sandstone and conglomerate for~ation (Pleistocene) Temecula Arkose (upper Pliocene) I",,'''', "'i- ""I Basement complex (mid-Cretaceous and older) Figurel". Diagrammatic relationship-between the Pauba Formation, an unnamed sandstone and conglomerate formation, the T emecula Mose, and the rocks of the MesOzoic basement complex. SECTION I ~ 500 _ Meiers 400 - 300 __ SECTION 3 ~~~ SEC.~~~N 2rn::"'j . . ~ :. . . llo - .. - 200 100 o Fossil localily Upper boundoryof luffaceous $andslone facies (modified from Golz and others. 1977). interbeds, and the presence or volcanic clasts petrographically similar to those at Hogbacks--suggest an eastern and northeast- ern source area for these rocks. . A 2-to-3-m-thick ash horizon interstratified with sandstone near Chancy Hill. referred to as the Wildomar kaolin deposit (Dietrich, 1928) and considered a part of the Temecula Arkose (Mann, 1955), is correlated with the O.7-m.y.~ld Bishop Ash (Merriam and Bischoff, 1975). A. Sarna-Wojcicki of the U.S. Geological Survey and Glenn A. Borchardt of the California Division of Mines and Geology have also correlated the Wildo- mar kaolin deposit with the Bishop Ash by neutron-activation analysis (written communication). Detrital biotite originally considered to be part or'the primary ash fall mixed with initial biotite gave two erroneous KI Ar ages of 9.9 :j: 2.5 and 18.7 :j: 0.8 X 10' years (figure 2). Pauba Formation , The Pauba Fonnation, a succession of latc Pleistocene silt- stone, sandstone, and conglomerate. was named by Mann (1955) for exposures at Rancho Pauba, approximately 5 km southeast of Temecula in Rancho California. Rocks in the type area crop out nearly continuously for more than 5 km in the north-facing bank of Temecula Creek in lower Pauba Valley. The Pauba Formation has an exposed thickness of approxi- mately 75 m and is composed of (I) alight-brown, moderately well-indurated, extensively crossbedded, channeled and filled sandstone and siltstone facies that contains occasional interven~ ing cobble-and--boulder conglomerate beds and (2) a grayish- brown, well-indurated, poorly sorted fanglomerate and mud. stone facies. The sandstone and siltstone facies is widespread and crops out in its main part along the eastern side and central portion of the Elsinore trough from near Wildomar south through Pauba Val- "'S' ley and east to its unconformable contact with older sedimen- tary. plutonic, and metamorphic rocks in the vicinity of Skunk 6 .FOnNIA DIVISION OF MINES AND GEOLOC' SR 131 Hollow, Buck Mesa, and upper Temecula Creek (plale I). The slopes underlying these rocks are subdued and commonly man. tIed by a O.5-to-l-m-thick soil horizon. Discontinuous con- glomerate interbeds 10-50 em thick occur locally in the easternmost exposures of the siltstone and sandstone facies but are essentially absent in the westernmost exposures near Wildo- mar. West-dipping crossbeds,. channel-aod-fiIl features. and a variation 'in grain size along strike within individual beds are also common :to the easternmost exposure. These factors. when con. sidered together, suggest that this part of the Pauba Formation w8S:deposited in a fluviatile environment by a river system whose headwaters,: though certainly at a considerably higher base level, may have been coincident with the present-day drainage of T emecula Creek. The, fanglomerate facies of the Pauba Fonnation crops out nearly continuously along the~ eastern and central parts of the Elsinore ,trough from Temecula north to Cole Canyon. The clasts of the fanglomerate have been derived principally from the plutonic and metamorphic basement complex. Clasts of the fan- glomerate are angular and set in a well-lithified mudstone ma. trix which has also been derived from the local basement terrain. The mudstone swells considerably by the addition of water and. based on ifield observation. has an extremely high plasticity in- dex., The fanglomerate facies was probably deposited by sheet- wash activity on initially moderately steep slopes as small mud flows that coaJ.esced to form the continuous debris apron that now mantles these slopes. The fanglomerate facies is now partly dissected by east-flowing drainages that carry detritus to Mur- rieta Creek in the central part of the trough. Where these drain- ages have cut deeply into the bedrock, an interfingered relationship. between the fanglomerate and the finer grained sandstone and siltstone facies has been exposed. Because the facies change occurs over a distance of several hundred meters, the contact between these units is an approximation of where surface ex,posures belong entirely to the finer grained facies along the eastern side of the contact The late Pleistocene age assigned to the Pauba Formation is based on its superpositional relationship with the unconformably underlying approximately O.7-m.y.--old unnamed sandstone and conglomerate formation (plate I) and on a small fossil assem. blage reported by Mann (1955). The fossils, which include Equ. us. occur approximately I km northeast of Interstate Highway 15 (previously U.S. Highway 395) in the northwest bank of Santa Gertrudis Creek. Mann (1955, p. 14) states, "The horse teeth are modern in every respect and are much less indurated than the horse teeth found in the Temecula Arkose." Photo 2. Wildomcr fault zone neor Ran- cho Coljfornio. Dripping Springs formation The Dripping Springs Formation was named by Mann (1955) for exposures of fanglomerate that crop out immediately east of the area in road cuts along State Highway 71 in the Vail Lake 7,5' U.S. Geological Survey quadrangle. Only two smal1 expo. sures of these beds occur in the area studied, and they lie in the vicinily of lhe Yampa Ranch (Ial. 33"27'50"N., long. IlTOO'12"W.) and the eastern Pechanga Indian Reservation (Ial. 33"26'lO"N., long. IIT02'40"W.). These deposits are composed of pebble. cobble, and boulder fanglomerate in a reddish-brown, poorly consolidated, poorJy sorted sandstone matrix. The clasts are mostly subangular to subround and have been derived rrom the local basemen I rocks composed of gabbro, granodiorite, and hybrid gneiss. The age of the Dripping Springs Formation is not known, though it is certain from field relationships that it post-dates the age of the Temecula Arkose and is either equivalent to, or slight. Iy younger than, the late Pleistocene Pauba Formation. landslidt! Deposits Very few landslides occur in the area studied. The largest of these were mapped and are shown on plate 1. The location and a brief description of each landslide is given in table I. Terrace Deposits Quaternary terrace deposits crop out as isolated remnants of a once-widespread sedimentary cover. These deposits are com- posed mostly of reddish-brown, well--consolidated, coarse- grained sandstone and conglomeratic sandstone that contain stringers of pebble and cobble conglomerate. They are best pre- served east of the Wildomar fault zone and south of the Murrieta Hot Springs fault between Buck Mesa and Pauba Valley. Here. the surface upon which the terrace deposits rest lies between approximately 455 m on the east and 375 m on the west and. though regionally elevated and very slightly tilted to the west, is tectonically unmodified (figure 5). South of Pauba Valley, in the area east of the Wildomar fault zone, the terrace is steeply tilted to the northwest (figure 5) as a result of youthful uplifting of the Palomar Mountain tectonic block. Only one smalllerrace has been mapped on the southwest side of the Elsinore fault zone, and its age relationship to those to the west of the fault zone is uncertain. This terrace. which lies near (p ~ ,. , . CALIFORNIA OIVISION OF MINES AND GEOLOGY THOMAS E. GAY JR., STATE GEOLOGIST . i I I ! I ! i ":~~:::': :~":i'::~i,f~::i.:.:::(~t~~;~ LEGEND JJ ;g, I I I I B Alluvium, colluvium, and slope wash ~ Older alluvium EJ Stream-terrace deposits [;J >- 0:: q: Z a:: ILl !i :::J a Terrace deposits [;J landslide deposits '" <:: '" " <:> ..... '" '- ~ Q.. [;J Dripping Springs Formation ~ ~ Pauba Fonnation Qps" sandstone part; (}Pf, fanglomerate paPt. ~ Unnamed sandstone and conglomerate. formation Qua, sandstone paPt; Que, congZomerate part. >- a:: q: f- a:: ILl f- H Temecula Arkose ~ B Santa Rosa Basalt '" <:: '" " <:> ~ [;] Older terrace deposits ~ Quartz monzonite Kqm, fresh rock; Kqmd, decomposed rock. -{' (/) Ga Granodiorite 11__:: J " ~~;.., . " !7...~,::,~. ..0. . ~,.\. ~ ,.....-. -....; 7.~~.::..,. ..:-,.'-.,:, l :;>;-;;!;.,..... . ~ ~:~~D~o<; . -:':;~'':'l'. ". ".. .~,.,-' ~J=:l;;-;::... ,,-..: ","~ '":', . ~ " ~j I ~:~.ii,~S~,~,,,i " 'f j: ! ~ : ~ ~ ii.! if., i:' , . :~ J~ !~. lH :i-. :, :; . . MAP SYMBOLS - 175 U D FAULT ---**........ Solid line where confirmed. dashed line where inferred, dotted line where conce~led by unfaulted rocks; U, upthrown side; D. downdropped side; single:arrow and corresponding number indicate direction and amount of dip of fault plane; double arrows indicate the relative direction of horizontal movement;~~~ indicates shear zoneL X. indicates fault based on gravity data. ----------- Geologic contact ~ Sync 11 ne , --------+------ Anticline - r:--' = c::- Dike in metamorphic rock complex . 1... Tuffaceous horizon o~~~~~ooo",,oo Conglomerate horizon in sandstone fonmation ---T'i5 Dip and strike of bedding ~ Dip and strike of over- turned bedding -\15 Approximate dip and strike of bedding ----v40 Strike and dip of layering in volcanic rocks 175 Strike and dip of S-surface in metamorphic 'rocks ---50 Dip and strike of jOint -II- Strike of vertical joint . 05 20 75 01 Rock sample locality . 05 15 75 01 (KA g) Rock sample locality of material dated by KIAr analysis. . -9- Berghofer No. 1 (1234 m) Exploratory oil well Showing total depth drilled below land surface and name. o BS 2W 17 MI Water well Showing State number. ~.,.. TT.,.. d -< y-c " y "'.......1-.).- Closed depression @- Q\5~ Landslide deposit and corresponding number. __ -75___ _ Contours of the ground water table as measured in the autumn of 1971. (Contour interval in 25 mJ. '~-.,J i ~~'*_: