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Home My WebLink AboutCDP 02-56; WALTERS RESIDENCE; GEOTECHNICAL INVESTIGATION WITH ADDENDUM AND REVISIONS; 2003-01-20C I I I I I I I I I I I I I I I I I I OWEN ENGINEERING GROUP January 22, 2003 Mr. Walten c/o Friehauf Ardl.itects 341 South Cedro Avenue, Suiter Solana Beach, CA 920'75 Attention: Mr. Doug Fess Civil, A~t;&:ctural Engineering r---, .. '·-~ a:·:'l O -~ ,w.i CITY OF CARLSBAD PLANNING DEPT. Subject: Addendum and Revision/Typographic Correction to "Geotechnical Investigation, Walters Residence at 5305 Carlsbad Boulevard, Carlsbad, California" by Owen Engineering Group dated January 20, 2003. References: 1. "Geotechnical Investigation, Walters Residence, 5305 Carlsbad Boulevard, Carlsbad, California" by Owen Engineering Group dated January 20, 2003. Dear Mr. Fess: 2. ''Geotechnical Evaluation on Coastal Bluff Property, Vacant Lot South of 5303 Carlsbad Boulevard, Carlsbad, California" dated March 10, 1997 by Southland Geotechnical Consultants, Project No. 126021 Presented herewith is an addendum report and revision/typographic correction to Geotechnical Investigation Report prepared for the Walters Residence at 5305 Carlsbad Boulevard, Carlsbad, California dated January 20, 2003. Bluff' Stability and Setback Owen Engineering Group (Owen) concluded that the present site conditions are not significantly different from the conditions at the time that the report (referenced no. 2) was prepared and because of the bluff is well protected with shortcrete (see Photo in the reference no. 1). Owen concurred with their analyses and recommendations as presented in the referenced no. 2 and they could be applied for both lots, which includes the adjacent lot (5305 Carlsbad Blvd.). Reference No. 2 is included in the Appendix. Revisionffypographic Correction of Referenced No.I Report Page 4, Paragraph 3: Owen understands that the proposed development consists of the demolition of the existing residential structure and replacement with a new residential structure. The building will be one-story and occupy a footprint of approximately 6,466 square.feet. Conventional shallow foundations are expected to support the proposed structures. Fills for the project are not expected to be significant. 1525 Grand Ave, San Marcos, California 92069 Tulephone (760) 471 -6000 Fax (760) 471-6096 I I I I I I I I I I I I I I I I I I I Revised to Read as Follows: Owen understands that the proposed development consists of the demolition of the existing residential structure and replacement with a new residential structure. The building will be two-story and occupy a footprint of approximately 6,466 square-feet. Conventional shallow foundations are expected to support the proposed structures. Fills for the project are not expected to be significant. Page 11, Paragraph 2: I. An allowable vertical bearing value of 2000 psf should be used for design of continuous footings a minimum 24 inches wide and 24 inches deep and for design of square footings 12 inches wide and 24 inches deep, bearing in properly compacted fill material. The bearing may be increased by 200 pounds per square foot per additional foot of depth or width to a total maximum bearing value of 4000 pounds per square foot. The above values may be increased by one-third when considering short duration seismic or wind loads. Exterior square footings should be tied with a grade beam or tie beam to the main foundation. Revised to Read as Follows: 1. An allowable vertical bearing value of 2000 psf should be used for design of square footings a minimum 24 inches wide and 24 inches deep and for design of continuous footings 18 inches wide and 24 inches deep, bearing in properly compacted fill material. The bearing may be increased by 200 pounds per square foot per additional foot of depth or width to a total maximum bearing value of 4000 pounds per square foot. The above values may be increased by one-third when considering short duration seismic or wind loads. Exterior square footings should be tied with a grade beam or tie beam to the main foundation. Should you have any questions, please do not hesitate to contact the undersigned at (760) 471-6000. ~. ~i:1iss Enclosure: Appendix cc: ~ k'l!addressee M O'Day Consultants Charles J. Randle, P.E. R.C.E. 22096 : E I I I I I I I I I I I I I I I I I APPENDIX J 1 ... .i. ... 1•vv"' J..1.1:.v rA.4. 0001u,1.i4zz ~Kl~HAU~ ARCHITECTS March 1 O, 1997 Project No. 126G21 To: Attention: Subject: L.D. Richards Co,, Builder 1830 Oxford Avenue Cardiff, California 92007 --Mr. Larry Richards Geotechnlcal Evaluation of Co11tal Bluff Property, Vacant Parcel South of 5305 Carlabad Boulevard, Carlab1d, Clllfornla r· I l I I I I I . lotrgdyctlon I I r t~ accordance with your request, Southland Geotechnlcal Consultant, h•• perform1d a· geotachnlcal evaluation of the 1ubJeot coHtal bluff proparty. We understand that a singl•famlly ra,ldence la propoted on the property.· Thie report preaentl a summary of our flald end reaearch 1tudlea and our Qonclualona and recommendation, relative to the proposed development. Wa unclem1nd that aolll 1nglneeting 1arvlcea for foundation design fer the proposed realdenc• are being performed ·by others. Purpose and scope I · . Thie report pr .. ,nta the results . of our gaotechnloal evaluetlon of the coastal bluff property located 1outh of 5305 Cerlabad Boulevard In Carltbacl, The purpose of our study was to evaluat. the g'aotechnlcel conditions at the coastal bluff property and I provide recommandaUona relative to the propoaad construction. The ,cope of our geotechnlcal aveluatlon Included the following: I ·- I I I l· I Review of, aerial photograph•, geoiogic/topogr1phlc mapa, and geologic llterature pertaining to the alte and vicinity, A 11st of the Item• reviewed Is presented In Appendix A. ' Geologic reconnalsaance to obaerve the exlatlng alts condition, Including the coestal bluff and general vicinity. •Preparation of a tape and compaaa proflle of the bluff face. Gaotachnical analysla of the data obtained Including a computer-generated slope stability analyala of the coastal bluff. . . Preparation of thl1 report summarizing the re1ult1 of our geotechnical evalu11t1on of the coastal bluff' property. • •"'-•• 1ta~1n n4!iiH~ ~-• -· -.. ·----- Iii 002 I I ! .. ! r I I I I 1~ '14/2002 11:20 FA.I 8587822422 I . . FRIEHAUF ARCHITECTS I Proleat No. 128G21 I site oescriotion I The subject coastal bluffproperty is known ss San Diego County Assessor's Parcel Number ·210-120.31. The roughly rectangular property Is located .south o? the existing residential development located at 5306 Carlsbad Boulevard 1n the City of I Carlsbad (see Figure 1 ). Th• parcel to the south of the subject lot ls curre~tly undeveloped. The eastern property lln• at the site la located along the wa1t1rly 11de I of Carlsbad Boulevard·{formerly Highway 1 01) and ia approximately 60 feet long, The relativelY level bluff-top area of the property extends, from Carlsbad Boulevard to the top of 'the coastal bluff, approximately 230 feet along the northerly property line and approximately 200 feet along the .aoutherly property line: An approximately 40-foot I high coastal bluff with an overall gradient of approximately 45 degree• le located in · the western portion of the propef'W (see Photos 1 and 2). The approximate elevation I of the bluff edge Is about 40 feet above sea level based on the City of. Carlsbad 1991 orthophoto map (Appendix Al, · I · In general, the bluff-top area at the site elopee·gently towards the weat and I• mostly vegetated with lcepl1nt, weadl and acattared bNah. On February 12, 1917, SOC representatives made approximate meaaurementl of the western portion of the bluff- I top area at the site. The ra1ultant site plan (with the approximate location of the bluff edge) i8 Included III Figure 2, Please note that the bluff edge on the ett. II aO"mawhat obscured by vegetative growth 8rtd rodent burrowlng actfvh:I" (aaa Photo• 3 and 4), .-, We emphasize that our meaauremante are approximate. Figure 2 11 not a aurveyed I map. I I I I I I l I stuff Description During our site vl11t on F1bru1ry 12., 1997, a tepe and compa .. profile of the ooaatal bluff on the property w•• prepared. The resulta of·our approximate mea,urementa are presented. on Figura 3 (Coaltal Bluff Profile). Following la ii ,ummery oftha on11te bluff conditions. · · The approximately 40-foot high coastal biuff elopea at an overall gradient of approximately 46 degr111 (from the baa, of the 1aacllff to the upper bluff adge). , There Is an approximately 10-foot high, irregular but overall, near-vertical ,aacllff at the base of the coaataLbluff. (aae Photo• 1 and 2.). Thi• ·aescllff 11 not vegetated. Portions of the aeacllff are slightly undercut apparently by wave action. Indication• of minor sea cave development In the saacllff were oburved at the alte (1ee Photos 1, 2 an1 5). A ralatlvaly lave! "bench• area, approxlrriately 6 to 115 feet wide, has developed st the contact betWeen tha more re,lstant ~antlego Formation sandstone that compril8ath• aeacllff and the overlying, la .. ra1lstantt1rr90e d1poelt1 that comprise the upper portion of the bluff (aae Photo• 1 and 2), The upper epproxlmataly 30 ver'tlcal feet of the coastal bluff generally 19 aparaely vagatatad with 2 ' 71 ltll 003 SGC .. '. ·, .. f , · ll/14/2002 11:21 FAX 8B87922422 FRIEHAUF ARCHITEcrs I . I l. I I I I I I I t·· I I I I I I J. I Project No. 128G21 lceplant end weeds. However, the uppermost portion of the bluff and the bluff edge are generally moderately to well vegetated with iceplant. Gunlte covers the bluff face , on the properties· to the north and extends approximately 15 feat onto the subject coastal bluff (see Photos 1, 2 and 6). · · Proposed Development Project plans have not yet bean finalized. However; based on our conversations with you, It Is our understanding that a one-to two-story residence la proposed at the site. We understand that the retldance wlll be set back a minimum of 21S feet from the bluff edge. We also understand thet,tha residence will consist of typical, relatively . light, residential constructl~n. Geologic Units .Baaed on our review of a geologic map (~ppandix A, Reference 131 and our onaitt observations, the property 1pp11111 to be underlain by Eocen~aged Santl1go Fo.rmation sandstone ovarl1ln by Qu1tern1ry-1gad terrtca deposits. Surflclal depo111' consisting of beach dapoelts along the toe of the aaacllff ware observed during our site visit and fill soils ware obNrvad on the bluff face and bluff.top area. The approximate limits of these unite, ae observed In our on•lte studies, ere ahown on , Figure 3 and are described below: sontJago FgrmatJpn -The Eoceri•ag,d S1tntlago Formation 11 expoaed in the approximately · 1 <>-foot high, irreauler but near-vertical aeacllff located just easterly of the beach In the western portion of the site. ·· The Santiago Formation sandstone generelly conslets 'of e light gray-brown, well-cemented, silty,'flne-gralned sandstone. T~e Santiago Formation 11 finer ;reined near Its contact with the overlying terr•oe d,poalts. Localized concretion, and oroa1- beddlng were observed In the seacllff face. Terrace Qeoo•ttl -Quaternary-aged terrac, dapoalta unconformably overlle the Santiago Formstion and comprise the meJorlty of the bluff face. The tsrrac, deposits consist of orang•brown to light brown, dansa but friable, slightly ellty fine· to medium-grained s1nd. Near the base of th• terrace deposits, talu• (or slopewash) derived fr.om the terrace deposit• hae acc·umulated by the downslope actions of surface wetera and gravity. ' . Beach P@RA•ita • A varlable thickness of unconsolidated beech deposits occur on the beach at the base of the eeaoliff, During our alte vl1lt1, tha beach deposits consisted of sand. Thia materlal ls subject to addition end removal In response to storm waves and currents. 3 fill 004 {11/14/2002 11: 22 FAX ,8887922422 FRIEHAUF ARCIIITBCfS Iii! 008 C E '--' I I I I I I I ~ I I I I I I I '"-" I Project No. 128G 21 EUI sons. Fill soils exist locally on the bluff facefafi~f blri~-tC:Y ~::e';~~~hi;~ on Fi ure 3) It appears that minor amounts o so s m •• to fnf~I two r~latively small gullies at the· site (see Photos 1 and :i) ·~~ addit;'~ fill soils were apparently pushed over the bluff edge onto the. u ace. d .flll soils generally consist of focally-derived terrace deposit materials an chunks of concrete and asphalt. Geologic Structure. The Santiago Formation Is ~ell exposed In the seacilff at the property and to the south. The Santiago Formation at and near the subject property .1• nearly fltt-lylng, . Bedding In the auatilrnary terrace depo1lta can be . ol,served ,s altemttlng more resistant and Iese reslltant bec:11, Whert observed on site ind In the general site vicinity, the terrace deposits appear to bt horlzontelly baddtd with locallzld ere••·· bedding. Fractures were obaarved In the sea cliff 1nd a dominant near-vertical Joint orlant1tion of NSOW was measured, However, no major out-of-elope bedding components ware observed that would be adverse to elope etablllty, lndloatlon1 of deep-Mated landslide featuree were ncit ob1erved during our re1earch atudle1 or site vlsitl, Review of Gegtecbolcol t1111as•LCCmmJot Map Our review of Geot,chnloal Hazarda/COnstralnt Map ·page 14 of the City of Carlsbad Geotechnlcal Hazards An•IYII• and Mapping Study (Appendix .A) Indicates that the site Is located In Hazard Categories 41 and 153. Category 41 perttln• to ·co11tal stability: moderately stable: hlah steep bluffs, unfavorable 1tructure, moderete to rapid erosion.• Category S3 pert1ln1 to er••• with •other terrain conditions: generally stable: relatively l1vel mesa ilreaa underlain by ttrraoe daposlta, nndltone . or granitic/metavolcanlc btdrock, • Plea,e note that the Geottchnloal Haztrds Analysis and Mapping Study 11 primarily Intended for planning purpo1e1 and should not be construed as definitive data for a 1peclflc site. · faulting Our review of geologic literature (Appendix A) pertaining to the g1neral 1it1 ,area Indicates that there are no known •act1ve• f1ults on or in the Immediate vicinity of the site. An "active• fault le defined bY the .California Division of Mine, and Geology 1a one which has "had 1urfac1 dlapl1cement within Holocene time (about ·the lalt , 1,000 years)" (Appendix A, Aeflrence 4).. Indication, of ectlva ftultlng were not obeerved In the subject coeltll bluff. The nearest known active faultl art the Rose 4 . ,. ' ·' .I 11/14/200% 11: 22 FAX U87922UZ FRIEHAUF ARCHITECTS r Iii! 008 t . Ptoleet No, 126G21 E '-../ Canyon fault located offshore appr~xlme~el~: ~lie: wes;:: t=~d •:~ .t;1:-i;i;:~:~~ I . Bank fault located offshore ~pprox,mhate Y f • th m s~t:.w Th~ San Andreas fault is I I I I I located approximately 25 miles nort east o '. located approximately 62 miles northeast of the srte, Our review of the City of Carlsbad Geotechnicel Hazards Analysis end ·Mapping Study (Appendix A) lndicat@s that a relatively short, northerly-trending fault trace has been mapped on and near the aita. It appears to coincide with th• gully located off site to the south of the subject property (see Figure 1 ). We did no~ obaerve direct, definitive evidence for the prasenoe of thle fault during our site v11lta, however, Ii m•v be obscured by fill eolls present In the offalte gully. The City of Carlsbad study state• that •811 faults that have been mapped within the Cltv limits base~ on ourrent knowledge are ell considered Inactive•. Baaed on Its_ relatively ehort length and northerly trend, it Is our opinion that this mapped fault does not present a selemlc· · · source hazard to the subject project. Tsunami and Storm Wava• I Tsunami ere see waves generattd by submarine earthquakes, landslides or volcanic . action. Submerlne earthquakea are common along the edge of the Pacific Ooean and coastal areas are aubJeot to potential inundatlo!'I by taunami, Moat of the 19 teunaml reoo rded on the San Diego tidal gauge (between 1864 to 1872 and 1909 to 19771 have only been a few tenths of a meter In height (Appendix A, Reference 1), .The I I I I largest San Diego area tldal gauge excur.ion (1 meter) wae associated with the tsunami of Mey 22, 1980 and wu recorded et La Jolla (So;Jppa Pier) (App,ndbc A, Reference 121. The taunaml wu generated by a lllohter magnitude S,15 earthqueka in ChDe. Fo.r comperlaon, th• diurnal range of tid•• It San Diego Bay is 1. 7 metera, The possibility of a deatruotlve t1unaml along the San Diego coaatllne la oonaidared low (Appendix A, Reference 51, However, taunaml or storm wavea (asaoclatad with winter storms), In conjunction with high ·tldee, may erode the coastal bluff taos (eapeclally the friable terreca deposits) bui generally are not anticipated to have the potential for Inundation of the bluff-top building site. Groundwater and Surface Water I During our site viaite, groundwater 111page waa obaerved In the coastal bluff near the southern edge of the gunlte coating on cha northern portion of the site (see Photo.GI, I Based on our• experience end· obaervatlon,, our eatlmatlon to tl:le depth of · groundwater Is thet It Is at or near ua level and may also be perched ·1ooally on th• Santiago Formation at Its contact with the overlying terrace deposits. Groundwater I levels can be expected to fluctuete with the tldee, uaaonal preolpltatlon and \ .. ..., irrigation. Groundwater ie not expected to be a constraint to conlltructlon of the I 15 ·. , . 11/14/2002 11:23 FAX 8587922422 FRIEHAUF ARCHITECI'S IC007 r I I ..__, I I I I :1 I I I-- \ I j I ' ' I : • J i I J J ; I :, ; ,,__, j ,1 ProJi,ct No. 126G21 ro osad residence. However, our experience lndicetas that near-surface P ro~ndweter conditions can develop In area• where no such ground~ater COl)dltlons ~revlously existed, especially in areas where a substantlal lncrease·(n.surface water infiltration results from landscape Irrigation or. unueually heavy prec1p1tatlon. The.bluff-top surface water, appear to primarily drain towards the west•• sheet flow, As they approach the bluff edge on the ,ite, the eurface wat~ra are concentrated Into. generally shallow--gullies that have bean eroded' Into the bluff edge and discharge down the bluff fece. Hjstoric Research Summary vve have reviewed the literature, mapa and aerial photographs of the aite and gan1r111 · vicinity listed In Appendix A. Following la • limited outline summary of our review observations: · The oldest map we found on file at the County of San Diego Is an 1 898 survey · for the Fifth Road Diltl'lct (Appendix A), The bluff along the coa1tlln1 11 sketched on the map and the railway llna I• ehown. The olde1t photograph we reviewed w11 one from the 1 928-29 aerial photograph set on flla et the County of San Diego. The rellroad 1nd coastal highway (approximately the cu,rent Carlabad Boulevard) ere shown on this photo. A dirt road we,t ot the coutal highway, roughly parallel to the coastline, and along the bluff top In the general site vicinity la shown, A wider. cleared spot on this din road (a turn-out or vlewpolnt?I le located In the vicinity of the subject coastal bluff property. The offelte gully to the eouth la apparent. The subdivision roadway (Shore Drive) end acme of the aubdlvlslon homes to the north of the subJec~ property are 1hown on the 1953 aerial photograph,. The single-family residence thet curre.ntly s>elata adjacent to and north ot me subject lot is not 1hown. A dirt ro1d •1t:l1ta along the bluff •dge In the slit vicinity. The subject property appeara It may have been cleared and used for agricultural purposes. A relatively sm1II gully perpendicular to tha bluff edge Is apparent near th• aouthern boundary of the aubjact ·.property. The larg1r offslte gully (approximately 215 faet to the 1outh of the 1ite) 11 eleo appar1nt on the photos. ·The existing residence to the north of the subject property is shown o~ the April g; 1964 photograph and 1ub1equent photos. On ·th1 19.84 photo and photos from the late 1980'1, 1970'1 and 11rly 1980'• end on the County's 1975 orthophoto topogr1phlc map, the subject coastal bluff face appears to be generelly moderately vegetated, The bluff face appears generally smooth. and , ,• --- ~ 11/14/2002 11:24 FAX 8S879Z24Z2 FRIJ!JIAUF ARCBITBCTS I I Prol•et No. 128G21 I I I I I I I I' - uniform as It extends from the bluff edge to the we~tward,?dge of the near· vertical seacliff at Its base. The currently existing bench on the resistant . Santiago Formation is not apparent. ' Based on· our review of 8 197B photo looking north towards the site (Appendix A, Reference 11 ) , gunlta eppeere to cover the lower part of ~he coastal bluff at the site and on the properties to the north and south of the aite, our review of the Army Corpe of Engineer•' report, •coaetal ·Cliff Sediments, San Diego Region" (Appendix A, Reference 11), Indicate, that an episode of erosion occurred between Auguet 7 and 9, 1983, "as • result of waves from a southern hemisphere storm.• In the 'cove' area, appro><lmately 100 feet south of ·the site, the report ltllttl that "the cliff retreated 28 to 35 feet" _and "this wes more erosion at the. 9itt thin' had occurred during the prev1ou1 40-year period.• The photoe show that, at the eubjact prope~, • "bench" developed on the reelatant Santiago Formation as I rnult of landward retreat (approximately 1 5 to 2.0 feet> of the toe of the terrace deposits at the 1lte. However, even though the toe of the terr,ce depoel!I retreated, the upper portion of 1he bluff and bluff edge do not 1ppear to have eroded, beeed on our review of the photos. The "bench" on the resistant Santlego Formlltlon le shown on the 1984 end more recent photo• and wea ob1erved during our site visits. I I I I I I I iii Iv ~I On the 1991 orthQphoto mapping sheet and 1992 photographs, the bluff-top. area ia vegetated genenilly almllarly to what we obaerved during our recent site visits'. However, the bluff edge end bluff face were leu vegetated In the early 1990's than observed during our ·1997 site vltlte. Coastal Bluff Bottoet The Carlsbad coastline In the vicinity of the subject property conalsts of a slight headland to the north of the aite end la Indented (Into. a •cove') to the south of the subject property (see. Figure 1). The 11te It located on the northern edge of the Indentation in the coast (concave to the oceen). Mechenltma for eeacllff ratreit at tha site Include slow abrasion and undercutting by marine ero1lon (wave ectlon) of . the hard, erosion-resistant Santiago Formation. aendatone bedrock exposed In the near-vertical seecllff. Storm surf end higher high tides contribute to the netural process of marine erosion. Other factors affecting the rite of retreat of a near-vertical seacliff at the tot! of • coeml bluff Include degrff of. fracturing, jointing, consolidation of sedlr:nenta, ateepne11 of elope, groundwtter end 1urfece water conditions, vegetation or lack of, and lnten1fty of pedeltrlen and anlmal traffic. 7 Iii! 008 11/14/2002 11: 2' FA.I 8S879Z2UZ I . . FlUt:HAUF ARCBITBl:1'11 I I I I I I I I I ~ I I I I I 1r I /!, ~i l I I Project No. 12BG21 In response to the landward retreat of the seecllff, the overlying coastal b~uff b~cobmes undermined and also retreets landward. During stor!1' surf and h,lgher ti ~s, t e Ot~= of the terrace deposits at the site are also au~Ject to marine ero~1on. mechanisms contributing to bluff . retreat l_nclude failure ot overhanging . bedrock projections, shallow failure of over1teepened portions of the blu_ff-fece terrace deposits and rilling and ravelling of the terrace deposits. Portion, of coastal bluffs .are also' exposed to-.praclpitation, wind, pedeetrlan/anlmal erosion !Including foot traffic and burrowing rodents), variations In landscape, land1cape ma1ntenence, and ' other activities by humans. . During our studies, we did not observe lndlcatlona of deep-seated instability, such ills ancient or active landslides, on the site, and the Santiago Forma~n 1Bndet~ne that comprises the seaollff 1t the site la not known to be prone to large, deep-seated · failures. The terrace deposits are friable and cbmmonly rill and ravel in overateepanad slopes, however, they are not known to be pron• to l.rge, dHp-Nated flllluree. coaar,1 BJuff::Edg• Ratctot BISo• The rate and magnitude of coaetal bluff retraat at a specific elta tre dependent on a variety of factors, both natural and manmade. Many of th•• factors. are ongoing processes and historic documentation can ba helpful In '9tlma1fng general bluff ... dge retreat rates. However, there are other factore affecting coaet91 bluff ratreat that ~ennot be estimated from historic documentation. Such faotort lncludt futura human ecti'llities or possible extreme variation, In regional welther patterns. Detrinental changes in fectors affeotlng· bluff-edge retreet, IUCh as misdirected · drainage, water lint breaks, very heavv storm eurf and/or precipitation, could lnoreese the rate of future erosion. However, favorable ohanau In the factors affecting bluff- edge retreat could decreeaa the rate of future ero1lon. Some of thee• Include eliminating detrimental human activities on the bluff, proper maintenance of a bluff- stabUizlng vegetailve cover, enhanced site drainage provisions and beach sand repleniehment currently proposed by San Diego Countv coastal communities. Research atudlea along the San Diego coast and hletorlc: photogr1ph and map review are components in providing an a,Umatlqn of the rate of bluff.edge retreat. We assume that the historic retreat rate may give an indication of the future retreat rate at a particular site. However, accurate and clear photographic and map documentation tor measuring retreat la not alway• evallable or 11 of fairly short time lnteivsls so ch,lngea may not be noticeable. Lee and others (Apptndlx A, Reference 8) performed research studies of regional historic seacllff retreat and provide a maximum annual rate of .. ,cliff recesalon of 0. 7 inch. The research studies also eati,:nated II maximum annuel bluff-edge retreat rate 8 1111 UUII 11/14/2002 11:25 FAX 8587822422 FRIEHAUF ARCHITECTS I I Project No. 128G21 L,of 0.22 to 0.33 feet per year. Over a 76-year period (assumed to be. the economic lifetime of the new construction), thla equates to a conservative eat1mata of bluff· I edge retreat of a maximum of 18.5 to 24.B feet. This max(mum la baaed on research I I I studies of regional historic bluff retreat' that includes coastal bluffs with generally favorable conditions, as wan ·as coaatal bluff& that are affected by more adverse conditions (fracturing, sea caves, groundwater, human activities, etc.) .. The estimated values of ma,dmum retreat are very conservative, and the actual rate of bluff ratreet at the subject property Is expected to be less considering the site conditions and historic bluff-edge retreat at the site, Documentation .of a two-day erosion period at and near the site In August 1983 (discuieed above) Is Included In the'U,S. Army Corps of Englneert' report, "Coestal Cliff Sediment,, San Diego Region" (Appendix A, Aeferanca 11 ). ThJ• report Indicates I that an episode of erosion occurred between Auguat 7 and 9, 1983, •a, a result of waves from a southern hemisphere storm.• In the 'cove' area, epproxlmately 100 I I , feat south of the site, th• report states that •the cliff retraated 28 to 3& feet" and "this waa more erosion at the .altt than h9d occurred during the previous 40-year period." The photos show that at the eubJtct property, a "bench" developed on the resistant Santiago Formation ae a result of lendward retreat (approxlmetely 1 6 to 20 feet) of the toe of th• terreoe depoalt8 at the site. However, evtn though the toe of the terrace deposits retreat.ct landward, the upper portion of the bluff and bluff , , edge did not appear to have retrtsted landwerd et the altt, t· Our historic photograph review (Appendix A) Indicates thet the co••ta( bluff et the subject property la ganerelly similar In c;gnflgurat(og In the 1929, 19&3, snd 1984 I through early 1983 photos •. Th• location of the onalte .bid._ Is generally similar · on the vertical eerlel photogrepha ( 1928 through 1989) llsted In Appendix A and also I I on the 1975 and 1991 orthophoto-topographic maps. However, in early August 1983, the 1:1111 of the onelte terrace deposltt eroded Inland up to approximately 1 B to 20 feat· end resulted In the onalte "bench" on the resistant Santiago Formation sandttone. · I 'I r I ! 11-1 If we assume that there ware no definitive polnta of reference (such •• the existing home to the north) to accurately measure prior Jo the 1 984 aerial photographs (although the bluff appears to be almller In conflguratlonl, tfla resolution end scale of · the photographs are such thet if bJuff••dge CllClft were -In excess ·of epproxlmt1taly 5 to a feat, It would likely be apparent. No apperant retre.t of the bluff edge w11 seen on the photos, however, we could assume, as a •worst-ceae~ scenario, thet the bluff edge had retreated 8 feet over the 25-.year time Interval viewed (from 1984 to 1989), and a historic maximum bluff-edge retre1t rate of approxlmetely 0.'24 fset !Jar year may then· be estlma:t,d from the sihot:ographs. Over a 75-year period, thi• equates to a "worst-caaa• or maximum of b!uff•tdge retreat of 18 feet. II I f i ! =--,' I I I 9 141010 '· ,; f, ~ h '., ' ' ,r . i' :, f r ' I ' . i ' I I 'I : I I li/14/2002 11: 26 FAX 8S879Z2422 FRIEHAUF ARCHITECTS . lill 011 m L I I I I I I I ~ I I I I I I I I Project No. 126G21 From our site visits and photograph review, we observed, for the recent paat, no indications that the current rate of retreat for the bluff edge is greater than thiJ · estimated "worst•caae" historic rate of 0.24 feet ·per year and It apparently is significantly less. However, It 11 very difficult to ~redlct the future and the magnitude · of bluff-edge retreat that may occur in one year, during one etorm event or over the 76-year assumed economic lifetime of the new construction. The rate of coastal bluff retreat over a particular intervel of time (day, year, decade, ate.) may vary from very little to several tenths of a foot. However,· severe eroeion la generally episodic In nature and is dependent on the Intensity of storms and combined high tides (or man's detrimental actions). It is probable thet sever el feet of co11tal bluff-edge retreat could occur at one time or over a short p·erlod of time. However, It is also likely that there will be periods in the future when erosion along the coast and bluff edge la rather insignificant and undetectable. Erosion la a neturally·occurrtng procus that ia affected by human actions. With tim1, tbl biyff edgo wHtr1trt1t l1ndw1rd, . If we assume a future retreat rate baaed on the •worat-c ... " elte-apeciflc historic " aerial photograph evaluation, th• maximum arnount the bluff edge may retreat landward over the next 78 years would be approximately 18 feat, If• future retreat. rate baaed on the regional study of bluff-top retreat rates (Appendix A, Reference 81 is assumed, the m1xlmum amount the bluff edga may retreat ovar die nut 76 years would range from 18.5 to 24.8 feet. Howavar, 111 stated abovt, thlt myimym · retraet rate la based on a researoh etudy of raglonal historic bluff·eda• retreat which also Included coaetal bluffl that are more adversely affected by conditions that , ·contribute to higher ratu of erosion (fracturfng, sea oavu, groundwater, human activities, etc.) than tho,, known at the subject property. We may speculate that the actual maximum value of future bluff-edge ratraat et th• site over the nut 715 yaara · will range somewhere from 18 (the 1lte-1peclflo, hlatorlo •worat-ca11•1 to 24.8 feet (the regional study •worat-caie") and that the 1ctua1 bluff-edge retreat Is likely to be less. It Is our opinion that the residence, propoaed ·to be set be~k II minimum of 25 feet from the bluff edge, will run be endangered by coalltal bluff retreat over the next 76 years. However, lmprovementa, such 1111 patios, fencea, etc., that are within this setback zone m-ay becom1 endangered (undermined) by bluff-edga retreat during the next 76 years end may need to be removed from th1 site. Sea Caye lnflu1nc1 -Sea cave formation and 1ub11quent collapse are localized factors in the bluff r1treet proceaa. Indications of see cave development In ttie seacllff were ob1erved st the subject property during our·11te visit,. Photos 1 and .2 are view, of the 1ubJect coaatal seacliff/bluff and Photo 8 fa e oioaer view of a sea cave on alte. Figure 1 shows the property, nearby vicinity ertd locatlona of the onslte and nearby known area of ••• cave development. Our approximate meaaurementa made on February 12, 1997, Indicate thst the onsite sea cave extends • maximum of approximately 5 fNt obliquely into the 10 --- :/ I I II ii 11/14/2002 11:27 FAX 8187922422 FRIEHAUF ARCHITECTS Iii! 012 I I l I I I I I I I r I I I I I I I ._,, I Proj.ct No. 126G21 seaclitf with a trend of roughly N715W. The sea cave ls about 1 foot In height .. The nearest offaite aea cave to the site is located approximately 3 .feet southerly of the southern property boundary (see Photo 2). · Thia sea cave extends approximately 2 feet Into the ae,cliff with a maximum height of 1..5 feet. Fracturea and bedding planes apparently control the development of these two cavea. Dua to their relatively email alzaa, it 11 our opinion that If either (or both) of th••• aea .cave areas. enlarged and failed. within the next 76 years, their collapee would not imp,ect the proposed r11ldenc1 (which wlll be set back a minimum of 26 feet from ~e bluff edge). · Sejsmjc Shakjng loflYIDGI • In general, the role aalamlc shaking playa In bluff retreat is dependent on bluff condltiona et th~ moment of ehektng. FaUure of bedrock proJectlona on saacllffa, failure of marginally stabls blookl of bedrock, collapse of 111 · i:1va1, and fliilurta of. undercut bluffa may· be common occurrence, along the San Diego coaatllne during atrong ground shaking. The Shoreline Eroelon A1H1ament and Atlee of the San Diego Region (Appendi,c A, Reference 31 atataa that the •potendal for cliff fallura due to a.thquake activity in San Diego la probably ,mall, but tlnce San Diego h•• not experienced ,trong motion In 1i.lch 8 long time, the cllffa ·hers mey be mor, 1u1oaptlb11 to eliding · than thosa In area, with shorter quake..return Interval,.• Slope ~ability catgut1tJgn1 A computer-generated alope·1tablllty analysis waa performed on the ooaltll bluff It the site. The slope atablllty we, analyzed using 'Janbu's Slmpllfled Method ·of Sllcea' with.the PCSTABL 5M computer program. Groundwater wu lnclud1d lri our elope stablllty analyses. The elope ttabDfty calculations are Included In Appendix B. The soil strength parameteni used In our 1na1Y1I, are preaented below. Th1111 vllu11 ara based on laboratory tut reaultl, back-calculatlon, our paat experience In thll area, and our professional Judg•ment. sou Type Unit Welebt Friction ADQII C0b111Qn Terrace Deposits 120.0 pcf 40 degreea 500 p1f Santiago Fm Sandstone 120.0 pcf 36 degreaa 200 paf The results of the analyses (Appendix B) Indicate that for the existing configuration, the calculated factor of safety 1galnat deep-seated failure la in exce11 of 1.5 (the generally eccapt1d standard for tha gaotechnlcal lnduatry). In addition, there ira no Indications of large ancient lendalides In the site vicinity. 11 • ll/·14/2002 11: 27 FAX 8587922'22 FRIBBAUF ARCHITECTS !Cl 013 I I L I I I I I I I r 1. I I ., I I ! I Project No •. 126G21 CONCLUSIONS ANQ RECOMMENDATIONS Bl!lsed on our geotechnfcal !!Valuation of the coastal bluff at the site, it·la our opinion that the proposed residence (and the loading from this relatively llg~t. blu~-top construction) will not adversely Impact the existing coastal bluff, In eddition, ,t the residence Is set back a m.inimum of 26 feet from the.bluff edge n p,anned, it le our opinion that the proposed construction 1hould not be affected by the maximum estimated coastal bluff retreat during Its economic lifetime (aesumed to be 76 years}, Slope StabHlty and Erosion Our geotechnical evaluation of the pre1ant overall static stabilitY on the ·subject property Indicates that the bluff la groaliy 11:lble, IA 111 ~,auc:.t &tats: &s slope i, · ·· mQ&fes t t; or t11thc ewdll?lt :rd brr r bur u audu:uu pound I fl t e c:1disinl ir;a ttl!lllfy. We provide the following recommendation• to help reduce ·erosion of the bluff and to reduce potantlel tor future lnetablllty of the bluff face. Irrigation of the lendecepe eraas on the property 1hould be limited to the minimum amount required to Ntabllah vegetation •nd maintain plant vigor. The upper portion of the -ubJ•at colltal bluff •nd th• bluff edge •re currently moderatelv·to well ve;et.-d with lotplant, At thl• time, It 11 our opinion that modifications to the . vegatetlon In thait . •reat ihould not be ccnllderad. However, If landscape plentlng and/or plent ·re,raoval on tlie weeterfy bli.aff•top · area is perform1d, It ahould bit done.wJtboyt slgnlflcentlf dleturblng the bluff. top soils. The 1urficlal atablllty of tho,, portion• of the bluff thet -,-not well vegetated mav be lncre•td by planting in eccord1nca with the recommendation• of • profe11lon1I lend1cape co~pany isxperlenced with coastal bluffs. Terracing or excavation of the bluff-face 1olla should be avoided. Drainage at the sitl 1hould be directed auch thtt 1urf1ce watera dlacherge Into non-erosive drain1ge provlalona. Runoff at the alte lhould not be directed over the bluff edge .. Eave gutter-ahould be considered for the re11dance 1nd should be properly maintained, Pedeetrl1n and animal traffic (and burrowing, ate,) on the bluff face and bluff edge should b1 curtailed. Bluff" Top· setback · As previously stated, we speculate that the max(roym value of future bh.1ff•edge retreat at the site over the next 78 year-msy r1ngeaomewhare from 1 B to 24,8 feet, and the actua( value of bluff.edge retreat Is likely to be le... The proposed ra1ldenca will be set back a minimum of 215 feet from the bluff edge. It 11 our opinion that the 12 11/14/ZOOZ 11:28 FAX 8S8T9ZZ4ZZ FRil!IIAUF ARCBITBCIS I . I L I I I I I I I r I Projll(;t No, 126G21 proposed setback will safeguard the proposed residence from bluff retreat during the economic lifetime of the residence. Sejsmjc considerations The prjnclpel conalderatlon, for mo,t structures In sauthem Calitornie ire surface rupturing of fault traces and damage cau11d by ground 1haklng or 1el1mlcally-l11duced ground settlement or liquefaction'. The po11lblllty of damage due to ground rupture , is considered minimal 1lnce no active f11ultl •r• known to orou the site. It II our opinion that the potentl1I for liqueflctlon or ••llmlcelly-lnduced ground 11ttlement et the site due to an earthquake is very low bec1u1• of the denH nature of the underlying terrace depo1ltl and Santiago f.orm1tlon aandatona. . ' ' The seismic hazard moat likely to Impact th• ,It• 11 ground 1h1klng reaultlng from 11n earthquake on one of the major 1cttve regional feultl. The nearest known active fault Is the Rosa Canyon fault located offlhore approximately .4 mllea weat of the 11te. It Is estimated that a maximum e1rthqueke on thll portion of the Ro•• C1nyon fault (magnitude 6.6) could produce moderate to ••vere ground shaking at th• site, As previously indicated,. In general, the role Ml1mic 1h1klng play, In bluff retreat II dependent on bluff-condltlon1 It the mom,nt of 1h1klng. Thli seacllff 11t the 1ubject property is near-vertlcel 11nd locelly portion• 1re lllghtly overh1nglng. It 11 po11lbl• that some of the bedrock projectlon1 m1y fell a the re1ult of 1evere ground 1heklng at the site. Overateepened portion• of the terreoe deposits m1y undergo 1hlllow failure end some r11velllng of the poorly lndul'lltlld bluff-flee terr1oe depo11ta miy 1110 occur during ground shaking, a1peci1lly on the unvegetlttd portion• of the bluff fece. I However, it is our opinion thlt th1 potent11I for d .. p-,e1ted or severe, catastrophic . failure of the bluff due to expected 111,mlc ground sh1klng 11 low 11t the site. I Other consJdaratjons I The recommendations provided in thll 'repo~ are b ... d on our understanding that 1 single-family residence (with it• relatlvely light loading) 1, pl1nned at the site and will be set back a minimum of 26 feet from the bluff edge. The elte condition, and bluff I edge indicated on Figures 2 ind ·3 hive been compiled from approxlmete measurements made during our 11t1 vl1lt1. They 1hould not be relied on for 1lte development. If needed, we 1ugge1t th1t .1 llcenaed l1nd surveyor· be retained to I prepare a site topographic p!an that eoouretaly delineate• the property bounderla, end bluff edge. In addition, a comprahen11ve site drelnege 1tudy may be conducted. to develop a site-specific drainage pl1n for the propoud development. Pl•••• note that I the recommendations cont1lned herein mey be revised baaed on modified end/or I._/ additional information regarding th.e 1tructur1 end Jmprovemanta planned at the 11te. I 13 !ill 014 I 'I . . • 11/14/2002 11:29 FAX 85879%2422 I FRIBIIAUF ARCHITECTS I L I I Project No. 128621 A qualified consultant should be retained to review site conditions ar:id. assess potential site Impacts following significant erosion events lr.t the future or 1f major changes in the bluff configuration ere noticed. Limitations and VoiiPcf'Qltx of Cgndjtjona I This geotachnlcal evaluation report addre11e1 the co1stal 'bluff conditions at the prqperty and Is based on our understanding that the proposed development con,1,ts of design and construction of a n~w alngl•flmHy re1idence aet back a minimum of I . 26 feet from the bluff edge. We und~tand thlt eoll• englnNrlng service• for de~ign and construction of thla propo.aed realdtntlal development art being performed by I I I ~ I I I others. In addition, we heve not performed an eveluatlon of the presence of hazardous materials/contamination at the site. ·· · · This report is baaed on our docuinent/photogreph review, .urflclal obaervatlona ·of the geologic conditions exposed at the sit• end vlolnlty, Thie report ••umea that the , geologlc/solls condition, do not devllt. eppreclably from tho• ot,urvad during our site visits. The recommendation• of thll report pertain only to the coastal bluff property evaluated. The findings of this report are valid •• of this data. Change, In ,condition, of-a property can. how1ver, occur with the pu1ag1 of tfmt, whether they be due to natural proceuas or the 11)/0rk of man on thll or adjacent propertlee, In addition, changes In applicable or appropriate standards may occur, from leglelatlon or the broadening of knowledge In th.• field• of geoteohnloal engineering or geology. Hence, the findings of this report may be lnvalkllted wholly or In part by changea beyond our control. Therefore, this report should not be rallitd upon after a period of Mo years without a review by us. . · · If there are queetions regarding the Information contained herein, we should be contacted. We will not be re1pon.lbl1 for the Interpretation by other• of the Information herein. Our service, conal,t of prof ... lonal consultation ilnd no warranty of any kind whatsoever, express or Implied, 11 made cir lntsnded In connection with 1 · the work performed by us. I I I v I 14 iii! 015 • --- . , . ., . .. ,, ·' .. 1' !! ' 1 11/14/2002 11: 30 FA.I_ 8&87922422 FRIEHAUF ARCHITBcrS I L I I I I I •• I r· I I I I I I t I Project No. 126021 If you have any questions regarding our report, please call. We appreciate this opportunity to be of service. Sincarely, SOUTHLAND GEOTECHNlCAL CONSULTANTS· Attachments: Figure 1 -Sita Location Map · · Figura 2 -Site Plan Figure 3 -Coestel Bluff Profile Photographs 1 through 6 Appl!nd_lx A • References Steve , RCE 47672 Project Englnee . Appendix B -Slope Stability Calculetlona Distribution: (3) Addressee .. 16 Iii 018 • 11/14/2002 11:30 FAX 8587922422 FRIEHAUF ARCHITECTS 1___. I SITE LOCATION MAP Project No. 126G21 Vacant Parcel South of 5305. Carlsbad Boulevard, Cartabad Scale (approximitte): 1 inch -100 feet Base Map: City of Carltbad Orthophoto To,:,ogriph/c Map 93 d!illted 1991 Ill 017 FIGUAE: 1 11/14/2002 11:32 FAX 8S87922422 I-·· I L I I I I I I I I t'i 'I I I I I I Site plan compiltd from approximate measurements m•de by SGC repr11enuttvH L"'" 02· 1 :z-97 . I THIS IS N'OT A SURVEYED MAP FRIEHAUF ARCHITECTS "' APPROX. NORTH Sc:ale (approlClmate); 1 Inch ,. 10 feet SITE PLAN v,c,nt Peteet South of 5305 Carlsbad Btvd, C.tl1bad Project No. 128G21 FIGURE 2 -c-- ·Scala (approximate): 1 inch= 10 feet ---··-- . ' . . . . . . ' . . .. . ' -?"""' --7---_.,_ seai:l"tff .. ··. . . .. . . . . . ' ... • I • • • • • • ~ . . .. . . . . . . .. : . . . . . . . . . . . . . . . . . . . . ~ ~~~:'.:.-:·::.~-:~~ci FORMATION ·. :: .... ::-:~: .... _::rtt:rJ .. : .: ...... .s.-t-.:-;. .. - Coasul bluff profile compiled from 8PPIOximllt8 measurement& made by SGC representatives on 02-12-97 (see RGUAE 2 for profile locatlonl .,, -· ---· ---· ----~--- .. · TERRACE DEPOSITS .... N60E ' , Nl!lfoximate loc:itlon of ' : 25-foot aetback line for I new residence ' I / COASTAL .BLUFF PROFILE Vacant Parcel South ot 5305 Carlsbad Blvd, Carlsbad Project No. 126G21 FIGUAE3 SGC 1i ' .. 0 0 .. ... ... .. .. ! .. '" .. .. ... .. .. ~ .. .. i3 ... I i ... ~ ~ "' el 0 ... "' 11/1--l , :?002 11: .3 J FAX 8587922422 FRIEHAUF ARCHITECT~ !llfl~~""il~' ·"'f\•'!o'l".JI'::~~·~·~·:.'::•_.',:.~.;.;~ -=-~~r ..... -.;. .... ~,:. ...... :,-"':t~ ... .,.. •• ..,.~,-·,'-:.. .............. ---·--------· .. _ ----·· -----· __ __ Project No. 126G21 --- PHOTO 1 CoHtal bluff, view southerly from near northern property boundary. . 1-31-97 '--" •BENCH- I PHOTO 2 Coastal bluff, view northerly from near southern property boundary 2·1 2-97 I ~~,... U /1412002. 11: 34 FAX 8587922422 I I I I I I I I PHOTO 4-,. 2-12·97 Bluff edoe, view northerly from fence inside southerly property boundary FRIEHAUF ARCHITECTS ~PHOT03 1~31 -97 Bluff edge, view northerly from south of site 141021 Project No. 126G21 SGC I J I I I I I I I I I I I I I I I I I OWEN ENGINEERING GROUP January 20, 2003 Mr. Walters C/o Friehauf Architects 341 South Cedro Avenue, Suiter Solana Beach, CA 92075 Attention: Mr. Doug Fess Civil, Geotechnical and Structural Engineering Subject: Geotechnical Investigation, Walters Residence, 9505 Carlsbad Boulevard, Carlsbad, California References: See Appendix A Dear Mr. Fess: Owen Engineering Group (Owen) is pleased to present the results of our Geotechnical Investigation at 5305 Carlsbad Boulevard in Carlsbad California. The purpose of this investigation was to evaluate the nature and characteristics of the surficial deposits below the proposed development and their influence on the construction of a single-family residence. Objective and Scope As outlined in the proposal, the purposes of this geotechnical study was to explore and evaluate the subsurface soil conditions at the subject site and provide geotechnical recommendations for the design of foundations, retaining structures, and pavements. A description of the scope of work is presented below. Task 1: Data Review/Utility aearance Review of existing data was conducted prior to the field investigation. A list of documents reviewed is included in the references section of this report. Each ofOwens's proposed field exploration locations was located and cleared with known existing utility lines and the participating utility companies through Underground Service Alert (USA). Task 2: Field Exploration Field exploration activities were performed at the subject site on December 9, 2002. A total of two (2) borings were advanced within the project limits using a truck-mounted hollow- stem auger drill rig. The locations of these borings are shown on Figure 2. One (1) of the borings (OE-101) was excavated to a depth of approximately 29feet below ground surface (bgs) and one (1) boring (OE-102) was advanced to approximately 50 feet bgs. Borings were 1525 Grand Ave, San Marcos, California 92069 14661 Myford Road, Suite C, Tustin, California 92806 Telephone (760) 471 -6000 Fax (760) 471-6096 Telephone (714) 734 -7993 Fax (714) 734-9732 I E I I I I I I I I I I I I I I I I I E excavated to visually classify the subswface soils and to obtain representative samples necessary for geotechnical testing. Field activities were perfonned under the supervision of a State of California Certified Engineering Geologist. Representative bulk, disturbed, and. relatively undisturbed samples were retrieved, sealed, and transported to our laboratory for selected testing. The typical sampling interval was approximately S feet. The number of blows needed to drive both a standard penetration test (SPT) sampler and a California-type split-barrel ring sampler was recorded. A description of the field exploration activities as well as the boring logs describing the encountered subsurface conditions is presented in Appendix A. Task 3: Laboratory Testing Laboratory testing was performed on representative bulk and relatively undisturbed samples to substantiate visual field classifications and to provide engineering parameters necessary for geotechnical design. The laboratory test results are presented on the boring logs in Appendix A and Appendix B. Testing consisted of in-situ moisture content and dry density, modified Proctor compaction, grain size distnbution, and direct shear testing. In situ moisture content and dry density tests were performed in accordance with American Society for Testing and Materials (ASTM) standard test method D2435. One (1) modified Proctor compaction test was conducted on sample LB-1 from Boring OE-101 in accordance with ASTMD1557. Grain size analyses were performed in accordancewithASTMD422. Direct shear tests were conducted on two (3) samples, from OE-101 and OE-102, according to ASTM D-3080. In the direct shear tests, samples were tested under normal stresses of l, I. 5, and 2. S kips per square foot (kst). Task 4: Geotechnical Analyses Field and laboratory data were analyzed in conjunction with the available preliminary plans provided by Fruehauf Architects. Owen evaluated potential foundation systems, lateral earth pressures for retaining walls, and construction considerations including earthwork and estimated shrinkage. Potential geologic hazards such as ground shaking, liquefaction, lateral spreading, ground rupture, and seismic settlement was also evaluated. Recornrnmdations for seismic parameters used in standard Uniform Building Code (VBC) (ICBO, 1997) seismic design were developed. Task 5: Geotechnical Report This report was prepared presenting the findings, conclusions, and recommendations for grading and foundation engineering. Recommendations for foundation type, allowable foundation bearing pressure, estimated settlements, seismic hazard mitigation, passive resistance, lateral earth pressures for retaining structures, soil corrosivity, soil collapse potential, rockfall hazard mitigation, and seismicity are presented. Owen bas also provided preliminary pavement section thickness for on-site areas. This report contains a site map, logs of the borings, and laboratory test results. Owen Engineering Group Walters Residence January 20, 2003 Page2 I FIGURE 1 -VICINITY MAP Mag 14.00 Mon Jan 2017:32 2003 Scale 1 :31,250 (at ~-> 2000 Feet 1000Meters Local Reed Ms;or Connector --T1'11il I I I I I I I I I I I I I I I I I I I SITE LOCATION AND DESCRIPTION The proposed project site is located at 5305 Carlsbad Boulevard in the southern portion of the City of Carlsbad in San Diego County, California (Vicinity Map, Figure 1 ). It is a roughly rectangular shaped parcel bound to the west by bluffs descending to the beach and the Pacific Ocean, to the east by Carlsbad Boulevard and to the north and south by residential development. Vacant lot to the south of the above address is a part of this study. The subject site is a mostly developed approximately 1.5-acre lot that lies at elevations of approximately 50 to 40 feet above mean sea level. These elevations correspond to a gentle slope westerly from Carlsbad Boulevard to the top of the bluff. The bluff profile then descends steeply to coastline at angle between approximately 60 and 40 degrees. The Bluff face is covered with shotcrete. PROPOSED DEVELOPMENT Owen understands that the proposed development consists of the demolition of the existing residential structure and replacement with a new residential structure. The building will be one-story and occupy a footprint of approximately 6,466 square-feet. Conventional shallow foundations are expected to support the proposed structures. Fills for the project are not expected to be significant. GEQTECHNICAL CONDITIONS GeoJo1ic Conditions Regional Geologic Setting The site is located at the coastal margin of Peninsular Ranges Physiographic and Geotnorphic Province. The Peninsular Ranges are characterized by a complex of northwest-southeast oriented blocks separated by faults of similar trend. One of the largest geologic units in western North America, the Peninsular Ranges extends 900 miles from the Los Angeles Basin to the tip of Baja California in Mexico. Regional Faulting and Seismicity Evidence of active faulting was not observed at the site during this investigation. In addition, there are no Alquist-Priolo Earthquake Fauh Zones (CDMG, 1997) located within or trending toward the subject property. Accordingly, trenching to locate active faults was not necessary for this investigation. The site is located in the seismically active Southern Califumia region and will probably be subjected to moderate to severe ground shaking during the life of the project. In addition, the site is located approximately 6 kilometers northeasterly of the Rose Canyon Fault system, which has been identified (CDMG, 1996) as an active fault (i.e., surface rupture within about Owen Engineering Group Walters Residence January 20, 2003 Page4 I I I I I I I I I I I I I I I I I I I the last 11,000 years). The maximum magnitude earthquake expected to occur on the Rose Canyon Fault has a moment magnitude of 6.9. (CDMG, 1996). Documented active faults that are located within 100 kilometers of the subject site are listed in Table A The table also provides the estimated maximum earthquake in moment magnitude (M...J associated with each fault. The maximum earthquake is estimated using correlations between fault parameters such as slip rate, fault length, rupture area. and actual measured earthquake magnitudes. Table A: Faults Within 100 km Radius of Subject Site Fault Roso Canyon Newport-Inglewood (Offahon:) Coronado Bank ~Tomecula ~Julian ~Ivy PalosVerdos Earthquake Valloy Nowport-Inpwood (LA Basin) San Jaointo-Anza San Jaointo-SanJaoinlo Valloy Cbino-Co.ttlJal Ave. (Elsinon:) San Jacmto-Coyole Crook ~Whittior Ehinme-Coyotc MOlUltain San Jaointo-San Bemadino Jaminp, 1994 CDM0, 1996 Distan<:e To Mapit1Jdc {3) Site MwAX (km) (1) 6.3 6.9 9.4 6.9 32.2 7.4 40.S 6.8 40.6 7.1 S7.1 6.8 S8.8 7.1 70.2 6.S 76.3 6.9 77.1 7.2 78.2 6.9 79.2 6.7 BS.I 6.8 8S.4 6.8 92.3 6.8 99.0 6.7 Slip~(]) (mm/yr) 1.50 I.SO 3.00 S.00 S.00 S.00 3.00 2.00 1.00 12.00 12.00 1.00 4.00 2.S 4.00 12.00 Fault l.ensth ('l Down (km) Dip(>) Type l6J Width (km)lt : : ss 6 13 2 B 66 7 13 2 B 18S 19 13 2 B 42 4 IS 2 A 75 8 IS 2 A 38 4 IS 2 A 96 10 13 2 B 20 2 IS 2 B 64 6 13 2 B 90 9 18 2 A 42 4 18 2 A 28 3 IS 2 B 40 4 IS 2 A 37 4 IS 2 A 38 4 IS 2 A 35 4 IS 2 A F9f9M#f· 1) 21llrouiJi8) 2) 6) M.. = rna1<i11111rnlll<llllflll mapitw!e u oolrul-by rdlli<mliip-by W<lls IIUICoppenmith. 1994 FauhT)pellomUBc:1997. T)peA:&ubue&ubwilh--m•de2:7.0IIUlllip-2:5mm/yr. T)pe C faulls an,fiwlla wbidl how--mufe< 6.5 IIUlltip-$2 mm/yr, T)pe Bfiwlla ..,.tbooafaulb wbid,. do not moot T}poA or l)poC<ril«il. 7) r = rovate, rl = ri8]I: Jat«aJ, II= ldl 1"unl, -Jlrib llip, o = oblique Owen Engineering Group Walters Residence January 20, 2003 PageS • Typo of Motion (7) rl-u 11 ... rl-u rl-88 rl-u rl-11 rl-a rl-u rl-u rl-11 rl-u rl-r-o rl-u rl-u rl-u rl-u I I I I I I I I I I I I I I I I I i, I 'I !i ' I Site Geology The site geology is characterized two units, Bedrock assigned to the Eocene-aged Santiago Formation, which is overlain by Quaternary-aged terrace deposits. The Santiago Formation was observed in the each of the borings at depths on the order of25 to 27 feet bgs. These depths correspond to elevations on the order of 13 to 16 feet above MSL. The Santiago Formation can be observed in the lower bluffs south of the property. The Santiago Formations consists of a moderately hard to hard tine-grained sandstone with some silt. It is moderately cemented and typically massive. The overlying Terrace deposits consist oflight yellowish brown to dark reddish brown (near- surface) sand. The sand is medium to very dense and fine grained. At the contact with the Santiago Formation a gravel layer was observed in both borings excavated as part of this study. Groundwater The groundwater table was encountered during Owen's field investigation in Boring OE-I 02 at a depth of 43 feet bgs. This depth corresponds to a measurement taken immediately after removing the auger from the borehole. A stabilized reading may differ from this depth. However the depth correlates well with measurements by others (Converse, 1984) and puts groundwater the approximate elevation of mean sea level. No landslides have been mapped in the vicinity of the subject site. However, steep cliffs exist adjacent to the site to the west. These cliffs ( coastal Blutrs) have been armored with shotcrete (see Photo 1 in Appendix C). LIQUEFACTION Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake- induced ground motion, create excess pore pressures in relatively cohesionless soils. These soils may thereby acquire a high degree of mobility, which can lead to lateral movement, sliding, consolidation and settlement of loose sediments, sand boils and other damaging deformations. This phenomenon occurs only below the water table; but after liqueJllctionhas developed, it can propagate upward into overlying non-saturated soil, as excess pore water dissipates. One of the primary factors controlling the potential for liquefilction is depth to groundwater. Typically, liquefaction has a low potential where groundwater is greater than 40 lilet deep and is virtually unknown below 60 feet. Since groundwater was encountered at 43 feet below bgs or at about MSL within the Santiago Formation which is very dense bedrock (N>50). Therefore, the potential for liquefaction at the subject site is considered negligible. Owen Engineering Group Walters Residence January 20, 2003 Page6 • C £ I I I I I I , I I I I I I I I I I ' I ,1 ii SLOPE STABUJD'. AND FQUNDAJIQN SETBACK Slope stability analysis and coastal bluff analysis were performed by Southland Geotechnical Consultants and presented in their report dated March 10, 1997. The report indicated that the proposed residence could be setback from the bluff edge as close as 25 feet. The site is not significantly differ from the description stated in the report (also see 01/01/2003 photo in Appendix C). The review of the current plan by Friehauf Architects indicated that the proposed residence will be located approximately 40 feet from the top of the bluff. The barbeque pit/patio .as proposed is located within the 25-foot setback zone. It is the Owen's opinion that the proposed barbeque pit/patio would not impact the bluff stability. CONCLUSIONS AND RECOMMENDATIONS Based on the field exploration, laboratory testing and engineering and geological analyses, it is Owen's opinion that the site is suitable for the proposed development from a geotechnical engineering and geologic viewpoint, providing that the recommendations presented herein are incorporated into design and construction phases of development. Seismic Design Comiduations General The subject property is located in a seismically active region and the proposed facility can be expected to be subject to seismic shaking during its design life. Potential seismic hazards include ground shaking, liquefaction and lateral spreading, ground surface rupture due to faulting, seismic settlement, slope instability, and mmamis and/or seiches. The following sections discuss these potential seismic hazards with respect to this site. Ground Shaking Because this site is located in the seismically active Southern California region, Owen recommends that the proposed development be designed in accordance with requirements of the 1997 UBC for Seismic Zone 4. Owen recommends that a soil profile type s. be used in the UBC design procedure. Other UBC seismic design parameters including C., C,,, N., Nv, Z, and source type are given in Table 3-1. A seismic bazard analysis was performed to evaluate the potential strong ground motions from an earthquake near the site. In accordance with 1997 UBC guidelines, the ground motions (peak horizontal ground acceleration measured as a percentage of the acceleration due to gravity) used for the analysis corresponds to an event that has a 10 percent chance of exceedence in 50 years. The ground motion associated with this event has been estirnated to be 0.44g (USGS, 2001b), where g = the acceleration due to gravity. This ground motion corresponds to an earthquake with a magnitude ofbetween 6.5 and 7.0 near the site (USGS, 2001a). Owen Enginuriog Group Walters Residence January 20, 2003 Page7 • I I I I I I I I I I I I I 11 l II I I 11 1, I I The following seismic design parameters should be used to develop the Design Response Spectrum, per Chapter 16 of the 1997 UBC: Table 16-J Soi!Profile Type s. Figure 16-2 Seismic 1.one 4 Table 16-1 Seismic l.ono Factor Z 0.40 Table 16-Q Seismic Coefficient, Ca 0.44 Table 16-R Seismic Coefficient, Cv 0.57 Table 16-S Near Source Factor, Na 1.0 Table 16-T Near Source Factor, Nv 1.0 Table 16-U Seismic Source Type B NearestFaDlt Rose Canyon 6.3Km Seismic Displacements The potential for ground surface settlements during an earthquake was evaluated using the procedure outlined in Terz.aghi et al. (1996). For a magnitude 7. 5 earthquake, the maximum seismic settlement of the ground surface at the site was estimated to be about 1 inch. The structures on the subject site are expected to be subjected to differential seismic settlements of about 0.25 inch. Other Seismic Con1ideratio111 Owen has found no evidence that any faults trend toward or traverse the site. Therefore, the likelihood of ground-surface rupture due to faulting is considered low. Due to the absence of landlocked bodies of water and the elevation of the site, seismic seiches or tsunamis are not expected to be a concern. Site Grading The geotechnical engineering analyses performed concerning site preparation and the recommendations presented herein, have been completed using the infonnation provided. In the event that any significant changes are made to proposed site development, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and the recommendations of this report are verified or modified in writing by this office. The following general recommendations are preliminary and will require updating subsequent to review of final site grading and development plans. Owen Engineering Group Walters Residence January 20, 2003 Pagc8 • I I I I I I I I I I I I I I I I I I ;I I General All grading and earthwork construction should be conducted in accordance with the requirements of the City of Carlsbad, and recommendations presented herein. 1. 2. 3. 4. The proposed grading entails cuts and fills to create positive drainage away from the proposed structure towards appropriate drainage devices. The areas proposed to receive fill should tie observed and approved by the project geotechnical consultant prior to filling. The exposed surface should then be processed (scarified and/or removed) to a minimum depth of six to twelve inches, brought to near optimum moisture content, then compacted to minimum project standards. Processing and moisture conditioning depths(s) can vary depending upon the time of the year grading is undertaken, and site conditions at that time. Any remaining areas to be cut should be cut to grade and observed by the geotechnical consultant. The resulting areas of cut surface may require processing (scarification and/or overexcavation), if deemed necessary based on exposed conditions. Fills placed on existing surfaces, with a gradient steeper than S: l (horizontal to vertical), should be benched into firm and dense materials and brought to finished grade with compacted fill. The need and disposition of drains will be determined by the project soils engineer based on field conditions. Site Preparation Areas beneath the existing residence should be removed to depths necessary. to remove existing concrete footings. Surficial vegetation, pavements, deleterious, organic, inert, and oversized materials (greater than 6 inches in maximum dimension) should be stripped and isolated prior to removal of reusable soils. Areas to receive fill or structural loading should be stripped ofloose or soft earth materials until a firm subgrade is exposed. The stripping work should include the removal ofloose uncompacted fill/soils, topsoil, and alluvium that, in the judgment of the geotechnical engineer, is compressible or contains significant voids. All uncompacted fill soils within the building footprints should be removed and recompacted. The stripping operation must expose a firm subgrade that is free of large voids. In general, the exposed subgrade should have a dry density greater than 90 percent of the maximum dry density. The subgrade soils exposed at the bottom of each excavation should be observed by a geotechnical engineer or geologist from Owen's office prior to the placement of any fill. Additional removals may be required as a resuh of observation and testing of the exposed subgrade soils. After site preparation, excavation, and prior to placement of any compacted fills where necessary, processing of the approved subgrade should be performed by: (1) scarifying to a Owen Engineering Group Walters Residence January 20, 2003 Page9 • I I I I I I I I , I I I I u I I I I ' I I I' ,!1 I I depth of 6 to 8 inches; (2) moisture conditioning to within 2 percent of optimum moisture content; and (3) compacting to a minimum of90 percent of the maximum dry density. Excavation Characteristics The borings advanced at the site were advanced using a truck-mounted, hollow-stem auger with low to moderate effort required through the on-site soils. Conventional earth moving equipments (i.e. scrapers, dozers, and excavators) are expected to be capable ofperlbrming the excavations required in these materials. Engineered Fill Due to the generally granular nature of the on-site soils, it is Owen's opinion that most of the excavated on-site soils are suitable for use as engineered fill as long as particles greater than 6 inches in dimension are removed. Fills should be placed in horizontal lifts no greater than 8 inches in loose thickness and then be compacted to at least 90 percent of the maximum dry density, as evaluated by ASTMD1557, below the slab-on-grade and pavements. The removal and recompaction of the on-site soils should extend beyond the foundations a distance equal to the depth of removal beneath the foundation. Import materials should have a liquid limit of2S or less, a plasticity index of 12 or less, and be uniformly graded with no greater than 30 percent of the particles passing the No. 200 sieve and no particles greater than 6 inches in dimension. A granular import is preferred at this site to facilitate freely draining conditions behind reitaioing structw"es, foundation elements, and below pavements and slabs. If new import materials are dissimilar to those assumed in Owen's geotechnical analyses, then special earthwork recommendations may be required. Earthwork operations should be observed and tested by a representative of Owen's office. Owen recommends that a shrinkage factor ofbetween 1 O and lS percent be used for the on- site soils. This recommended range is a rough estimate and should be used accordingly. The actual shrinkage value will be affected by several factors including the nature of the import materials, waste quantities during handling, local in-situ and compacted densities, actual compactive effort used in the field, and others. Fill Placement Subsequent to completing the removals and any overexcavation(s), the excavated onsite soils that are free of vegetation and deleterious debris may be placed in relatively thin ( 4 to 8 inches loose) lifts, brought to 2 percentage points above the optimum moisture content and compacted to a minimum relative compaction of 90 percent of the laboratory standard (ASTM D-1557). All grading should conform to the 1998 California Building Code and the requirements of the City of Carlsbad, except where specifically superseded in the text of this report and reviewed and approved by representatives of the City of Carlsbad. Owen Engineering Group Walters Residence Jan11a1Y 20, 2003 Page 10 • I I I I I I I I I I I I L I .t I ! I : I j I I I I I I I FOUNDATION RECOMMENDATIONS Design Our review, fieldwork and laboratory testing indicate that onsite soils have a low expansion potential. Recommendations for preliminary foundation design and construction of commercial buildings with column and continuous wall loads should not exceed SO kips and 4. 0 kips per lineal foot, respectively, and are presented below: Bearing Value 1. An allowable vertical bearing value of 2000 psf should be used for design of continuous footings a minimum 24 inches wide and 24 inches deep and for design of square footings 12 inches wide and 24 inches deep, bearing in properly compacted fill material. The bearing may be increased by 200 pounds per square foot per additional foot of depth or width to a total maximum bearing value of 4000 pounds per square foot. The above values may be increased by one-third when considering short duration seismic or wind loads. Exterior square footings should be tied with a grade beam or tie beam to the main foundation. 2. All footings should be embedded a minimum of24 inches into properly compacted fill or competent natural soil. 3. All continuous footings should be minimally reinforced with four No. S rebars, two top and two bottom. 4. Interior columns should be supported on isolated footings or integrated footing and grade beam systems. Column loads should not be supported directly by slabs. Lateral Pressure 1. Passive earth pressure of compacted fill may be computed as an equivalent fluid having a density of 3 SO pcf per foot of depth, to a maximum earth pressure of 2500 psf 2. An allowable coefficient of friction between properly compacted fill soil and concrete of0.35 may be used with the dead load forces. 3. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. 4. All footings should maintain a minimum horizontal from the top of the bluff in accordance with the recommendation presented in the referenced report and/or the applicable Building Code, whichever greater. This distance is measured from the footing face at the bearing elevation to the face of the descending slope face. Portion(s) the structure that encroach into the setback area could be supported by caissons or deepened footing. Owen Engineering Group Walters Residence JanlllllY 20, 2003 Page 11 • I I I I I I I I I I :J I " 11 /I I ti 1, I I , I I 5. The upper 12 inches of passive pressure should be neglected if not confined by slabs or pavement. Construction Consideration All footings should be embedded a minimum of 24 inches into properly compacted fill or competence natural soil. Foundation footings should be minimally reinforced with four No. 5 bars, two top and two bottom (in the cross-sections). Footings should either have continuous footings across large openings (i.e., garages or entrances) or be tied with a grade beam or tie beams. All exterior isolated footings should be tied in at least two perpendicular directions by grade beams or tie beams to reduce the potential for lateral drift or differential distortion. The base of the grade beams should enter the adjoining footings at the same depth as the footings (i.e., in profile view). The grade beam steel should be continuous at the footing connection. Grade beams and footings should be minimally reinforced and sized per the structural engineers recommendations. When reviewing the interior building footings, the structural engineer should consider utilizing grade beams to control lateral drift ofisolated column footings, if the combination of friction and passive earth pressure will not be sufficient to resist lateral forces. Prior to placing steel or concrete, the footing and grade beam excavations should be well moistened. Foundation Settlement -Structural Loads For two-story residential buildings, the anticipated total and differential settlements are on the order of0.50 inch and 0.25 inch, across 30 feet span, respectively. Majority of the foundation settlement is anticipated to occur during the construction. The estimated settlement should be in addition to the seismic induced settlement as previously stated. Slab-on-Grade Concrete slab-on-grade floors may be used for the proposed structures. The slab-on-grade should be placed on a minimum of 12 inches of recompacted on-site soils to provide a uniform subgrade bearing. If reducing the passage of water vapor through the floor slab is desired, Owen recommends that a vapor barrier be placed below the slab. In addition, the barrier should be covered with 2 inches of clean sand (i.e., no greater than 5 percent passing the U.S. No. 200 sieve) and be underlain by 1 inch of clean sand to protect the barrier during construction, act as a capillary break, and aid proper curing of the concrete slab. Areas adjacent to foundations, including planters, should be designed to drain away from the structure to avoid an accumulation of water beneath the slab. The following recommendations are meant as minimums. The project structural engineer should review and verify that the minimum recommendations presented herein are considered adequate with respect to anticipated uses. Owen Engineering Group Walters Residence Janwuy 20, 2003 Page 12 I I I I I I I I I I I I I :; I I I I I I / I :/ I Concrete slabs should be at least six (4) inches thick and be underlain by subgrade material compacted to a minimum 90 percent of the maximum laboratory dry density to a depth of 12 inches. The slab should be reinforced minimally with No. 4 bars at 18 inches on center. Subgrade Preparation The subgrade material should be compacted to a minimum 90 percent of the maximum laboratory dry density. Prior to placement of concrete, the subgrade soils should be moisture conditioned to at least 2 to 3 percentage points above the optimum moisture content, to a depth of 12 inches and be verified by a OEG field representative. Moisture Protection In areas where moisture condensation is undesirable (e.g., areas to have moisture sensitive floor coverings) a minimum 10-mil plastic membrane should be placed with all laps/openings sealed. The membrane should be sandwiched between two, 2-inch (minimum) sand layers. Retaining Walls and Swimming Pool Retaining walls up to 12 feet for the basement and swimming pool should be designed at-rest pressure equivalent to pressure exerted by fluid having a density of 53 pcf. Other cantilevered retaining walls are also anticipated. The design parameters provided below assume that low expansive soils (on-site) are used to backfill of the walls. Unrestraint cantilevered retaining walls should be designed to resist active earth pressures equivalent to pressures exerted by a fluid having the following densities: .. BACKFILL (HORIZONTAL: VERTICAL) .EQUJV ALENT f'LUlD DENSITY . .. ·· .. (pd) ... • ... ···· .... '.--'. Level 33 2:1 45 The foundation system for the proposed retaining walls should be designed in accordance with the recommendations presented in the foundation design section of this report. Wall Backfill and Drainage All retaining walls should be provided with an adequate back drain and outlet system to prevent buildup of hydrostatic pressures behind the wall. Typical back drainage should consist of 4-inch perforated PVC Schedule 40 embedded in 3 cubic foot per foot of% inch crushed rock wrapped in filter fabric. The subdrain should be outlet every SO lineal feet interval. Utility Trenches Bedding material should consist of sand with an SE not less than 30, which may then be jetted. Jetting in trenches adjacent to slopes should be carried out only under the specific approval of the soils engineer. Owen Engineering Group Walters Residence January 20, 2003 Page 13 • I I I I I I :1 l ll l I I I I I 'I I I I I I I Backfill of all trenches should be compacted to achieve a relative compaction of not less than 90 percent, the compaction standard being obtained per ASTM D-1557. Care should be taken not to damage utility lines. The site soils are considered suitable for use as trench backfill, provided they are at or near optimum moisture. The walls of temporary construction trenches are expected to be stable when excavation is nearly vertical, with only minor sloughing, provided the total depth does not exceed about 4 feet. Shoring of excavation walls or flattening of slopes may be required if greater depths are necessary. All trench excavations should conform to CAL-OSHA and local safety codes. Pavements Based on the granular nature of the on-site materials and the laboratory test results, Owen used a subgrade R-value of 68 for pavement design. Site specific testing (R.-value) should be conducted to verify improvements to the subgrade prior to implementation. Fleuble Asphalt Concrete Pavements Using an R-value of 68 and assumed traffic index (Tl) values, Owen bas developed the following recommendations for preliminary tlexil>le pavement design: Asphalt Concrete (inches) Parking Areas (TI=4.5) 2.0 Access Lanes (TI=S.O) 2.0 Truck Lanes (TI=6.0) 2.0 Class II Aggregate Base (inches) 4.0 4.0 4.0 The asphalt concrete thickness can be divided into base and finish courses. The uppermost 6 inches of subgrade and the Class II aggregate base should be compacted to at least 95 percent of the maximum dry density. Pavement section thicknesses will increase for areas of heavy vehicular use and for areas where larger wheel loads are anticipated. Subgrade drainage is an jmportant factor that enhances pavement performance. Subgrade surfaces below the flexible pavement structural section should be sloped to direct runoff to suitable collection points and to prevent ponding. Concrete curbs separating pavement from arid landscape areas should extend at least 6 inches below subgrade surfaces to reduce the potential for the movement of moisture through the aggregate base-course layers. The recommended pavement sections are preliminary in nature. The actual soils present at subgrade elevation after grading may be different than those assumed for this study. Owen recommends that bulk samples of the actual subgrade materials be retrieved and tested (R.- value) after grading is completed. Final pavement design recommendations may be presented after reviewing these R-value test results. Owen Engineering Group Walters Residence January 20, 2003 Page 14 • I I I I I I I I I I I I I I 1, I I I I CONCRETE DRIVEWAY AND EXTERIQRFLATWQRK Based upon a low expansive nature of the site soils (per 1997 UBC 18-1-B), the following recommendations are presented for exterior flatwork: 1. The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction, and be pre-moistened to 2 to 3 percentage points above optimum moisture content to a depth of 12 inches, as required. 2. 3. 4. 5. Concrete slabs should be cast over a minimum of 4 inches of clean sand (SE>30), compacted to a minimum of 90 percent and be wetted down completely prior to pouring concrete to minimize loss of concrete moisture to the surrounding earth materials. In order to reduce the potential for unsightly cracks, slabs may be reinforced at mid- height with a minimum of 6 x 6 -10 xl O welded wire mesh. Driveways, approaches and loading dock areas, otherwise designed by a qualified structural engineer, should be minimally reinforced with No. 4 bars at 18 inches at 18 inches on center. Exterior slabs should be at minimum 4-inches thick (nominally). Driveway slabs and approaches should be at least 6-inches thick. The exterior slabs should be scored or saw-cut, 2 to 3/8 inches deep, often enough so that no section is greater than 10 feet by 10 feet. For sidewalks or narrow slabs, control joints should be provided at every 6 feet or less. The slabs should be separated from the foundations and sidewalks with expansion joint material. Lot Drainage 1. Subsequent to the grading of the building pads, the designed drainage devices on the pads and slopes should be maintained to allow surface runoff to drain towards the street or designed area drain. Failure to maintain positive drainage may contnoute to foundation distress, utility trench settlement, and/or slope failures. 2. During and subsequent to any improvements, the positive drainage away from the structures and top of slopes should be maintained. Landscape and Irrigation 1. Slope surfaces should be landscaped as soon as possible. Slope vegetation should consist of deep routing vegetation that is capable of surviving in an arid climate. 2. The irrigation program for the slope areas should be decreased as soon as the vegetation has germinated or rooted. The irrigation should be adjusted for frequency and duration based upon seasonal changes. Owen Engineering Group Walters Residence January 20, 2003 Page 1S I I I I I I I I I I I I 1 I I I I I I I I 3. Irrigation should not promote runoff or ponding of water. The irrigation cycles should be of a short period of time that is adequate to support the vegetation. Geotechnical Observation/l'esting Observation and/or testing should be performed by the geotechnical consultant at each of the following stages: 1. During grading and precise grading. 2. Prior to importing of material. 3. 4. 5. 6. 7. After excavation for footings of buildings, free-standing walls, and prior to pouring concrete. Prior to placement of backfill. During placement ofbackfill for area drain, interior plumbing and utility line trenches, and retaining walls, if any. During slope or erosion repair, if any. When any unusual soil conditions are encountered during any construction operation subsequent to issuance of this report. LIMITATIONS The materials encountered on the project site and utilized in our laboratory study are believed representative of the area; however, soil materials vary in character between excavations or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Owen assumes no responsibility or liability for work, testing, or recommendations performed or provided by others. Inasmuch as this study is based upon the site materials observed, selective laboratory testing and engineering analyses, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice and no warranty is expressed or implied. Standards of practice are subject to change with time. Owen Engineering Group Walters Residence Jamwy 20, 2003 Page 16 I I I I I I I I I I I I ' I I ! 'I ! I ;I 1 , I I I I CLOSURE The opportunity to be of service is greatly appreciated. If you have any questions concerning this report or if we may be of furtller assistance, please do not hesitate to contact Jhe undersigned. Respectfully submitted, Owen Engineering Group ;JJ-/J---- AlanPace C.E.G. 1952 Enclosures: Figure 1 (In Text) Appendix A Appendix B Appen4ix C AppendixD Plate 1 Distribution: (4) Addressee (1) 0 'Day Consultllnts Owen Engineering Group Walters Residence Januaty 20, 2003 Page 17 I I I I I I I I I I , I ' I , I :.:1, I Ji :1 I I . 1.ij' I !) . I , I ' I APPENDIX A LIST OF REFERENCES I I I I I I I I I I ; I I , I I I I I I I I LJ§T OF REFERENCES Campbell, K.W., and Bozorgnia, Y., 1994 (Revised 1997), Near-Source Attenuation of Peak Horizontal Acceleration from Worldwide Accelerograms Recorded from 1957 to 1997; Proceedings, Fifth U.S. National Conference on F.arthquake Engineering, Vol Ill, Earthquake Engineering Research Institute, pp. 292-293 California Department of Mines and Geology (CDMG), 1996, Probabilistic Seismic Hazard Assessment for the State of California, Open File Report No. 96-08. CDMG, 1986 (Revised 1996), Geologic Map of California, Santa Ana Sheet. CDMG, 1973 (Revised 1997), Fault-Rupture Hazard Zones in California, Special Publication 42. International Conference ofBuilding Officials (ICBO), 1997, 1997 Uniform Building Code, Volume 2, Structural Engineering Design Provisions, Whittier, California, April. Jennings, 1994, Fault Activity Map of California and Adjacent Areas with Locations and Ages of Recent Vokanic Eruptions, CDMG. Portland Cement Association (PCA), 1984, Thickness Design for Concrete Highway and Street Pavements. Terzaghi, K, Peck, RB., and Mesri, G., 1996, Soil Mechanics in Engineering Practice, Third Edition, John Wdey & Sons, Inc., pp. 471-472. United States Geological Survey (USGS), 2001a, Historical &zrthquake Information Databases, National Earthquake Information Center, http://www.neic.cr.usgs.gov/neis/epic/epic.html. USGS, 2001b, Peak Ground Acceleration Database, JO Percent Probability of 'Exceedance in 50 Years, http://geobazards.cr.usgs.gov/eq/html/data.shtml. Wells, D.L., and Coppersmith, K.J., 1994, New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Seismological Society of America Bulletin, v. 84, no. 4, p. 974-1002. Wesnousky, S.G., 1986,&zrthquakes, Quaternary/au/ts, andseismichazardinCalifomia: Journal of Geophysical Research, v. 91, p. 12, 587-12, 631. I I ii ,. ,1·· i' :1 I I I I I I I I I I I I I I I I I I I "Geotechnical Evaluation of coastal Bluff Property, Vacant Parcel South Of 5305 Carlsbad Boulevard, Carlsbad, California" dated March 10, 1997 by Southland Geotechnical Consultants, Project No. 126G21. ''Geotechnical Investigation and Bluff Retreat Study, Parcel No. 210-120-30, Carlsbad, California" by ICG Incorporated, dated March 28, 1991, Job No. 04-8529-001-00-00. I I I I I I ii I• 'I I I I I 11 Iii 1•j I ' I I i1 I , I I I I WG OF BOREHOLE 101 Date Drilled: 12/9/02 Logged by: __ _:.,AP~--Project Manager: vs Equipment: _ ___,H~o=llo'""w'-"S=tem=A""uger=---Driving Weight and Drop: 140#/30"drop Surface Elevation(ft): 42.0 Depth to Water(ft): -~ 0==... ~ B= Im~ ~ § 1------S-UMMAR ___ Y_O_F_SUB __ SURF--A-C_E_CO_ND_m_o_iN_S ___ --l . .''. ·: ... / .. .... s -,,:, <' r 'lerrace aepos1t: Sand (lil'), IIIU1t moist Dark yellow brown ClellSC, NIA IIAMPLl!8 ii ,... ... ~ ~ 10 :{ff:~+ ---------------------------------------g " Light yellow brown " r Omvels, well rounded -2S -,·., , : . [il~,:::j::. --~---------~------------""T------------' (Ct> (118111iago Formation): Sandseone, pey, fllCIIMO'II - -30 -. -. r - -3S - r -. -40 -- - --- -4S - --g-- ,: ----so -15 - -~-~ I--iii -• 3-ss --~ ': = EOB@29' No Groundwater No Caving Boring Backf11led with Cuttings m--i OWEN ENGINl!ERING GROUP Walters Residence '"" ".' ~ 8e; eS, i i Ii ~ !1 ::2 lS 6.7 110. lS S.1 104.• 26 4.1 19 4.6 109. 30 S.3 S0/3" s, 8.0 116. I IS2S GrandAvcnuc San Marcos, CA 92069 Phone: (760) 471-6000 Fax: (760) 471-06069 5305 Carlsbad Blvd, Carlsbad, CA ~ 0 '"" Ii Plate B-1 I I I I I I I I I I I 1 • ! I t I I I I I I I WG OF BOREHOLE 102 Date Drilled: 12/9/02 Logged by: AP Project Manager: Equipment: Hollow Stem Auger Driving Weight and Drop: 140#/30"drop Surface Elevation(ft): 41.0 Depth to Water(ft): 43 .Shelby ~=:;:.,,, !'. W""'1 ~ ,-.. SAMPLES I-" ';;.I!. Tube ATD 8~ C ~ ca-u B~ trn =,,.. rt--._, 53 Ii i5 T-i ~ ~§ SUMMARY OF SUBSURFACE CONDmONS i 5 ::s --.·· > Terrace uepos1ts: ,)8llQ, .brown, nne dense, -. .· slightly moist E3 27 2.8 1.-'-. . >:_ 5 .·· ··.··.· . --.. . · .... i 47 -.. : --. .. .-. -: ·-. --31 2.8 .. -10 -. . :g 26 4.4 --·-. .::>.·::::i·:.::.:::.:> -15 -::_·:.::.-::·:_·_.::._-:·:::·:---E3 38 5.0 -• ::-:.:::.·.<···:··. - -20 -lti~ Light grey tg 44 3.4 ----"Onivels, weillOUllded -------------------------- ~-,~~ -25 · ..•.. " . : ... ( Formatiom): Silty • ._. M: Very fine ~ 54 3.5 " .. grained, moderately bard, light grey, moist " . : .. . .. ' -30 -· tg 80 14.' " -. : . " , . : . : -35 - · . ~ 80 18.( --. . . . . . -40 -Very moist :g 74 16.1 --: : : : -. . ... !'. . . . . -45 -.. . . --: . . ' -50 50/4" 17.' --.. -EOB@50.3' . . . . Groundwater at end of drilling@ 43' -55 -NoCavini . . -. Boring Bacldlll with Cuttings . . OWEN ENGINEERING GROUP 1525 Grand Avenue Walters Residence San Marcos, CA 92069 5305 Carlsbad Blvd, Carlsbad, CA Phone: (760) 471-6000 Fax: (760) 471-06069 I vs ~ ~ 0 ~ I-" ;~ ~1 ~ 101.o 104.• 103.: 102. 107. Plate B-2 t ' ' l i h " 11 I l ' i "iJ .. ,, "'qt.:'.@, I I I I I I I I I I I I I I I I I I I APPENDIXC LABORATORY TESTING AND SITE PHOTO I I I I I I I i I I ~ I ~ iJi I I I I I ,I j I Specimen Identification Ii S • 101 2.0 5 Ill 101 5.0 Ill NORMAL PRESSURE, pol Clasalllcallon ti MC% c 111 14 112 J OWEN ENGINEERING GROUP DIRECT SHEAR TEST I 1525 Grand Avanua Projact: Waltars Reaklence D er, San Marcoe, CA 92089 ~ Telephone: (780) 471-8000 Location: 5305 Carlsbad Blvd, Cerlsbad, CA + 31 31 31 151:;;.;;;;.;;;;.;;;;~-F-ax:-·-(7-80-~-4-7-1-0806---9------------~N.u.m.be.r.:---------------------------' I I I I I I I I I I I I I I I I I k b ~ ! : l 3: 135 130 125 120 115 110 8. ~ U) 105 z UJ C ~ C 100 95 90 85 80 75 0 DEG \ ' ' \ \ ' \ ' I\ \ "' ~ ' -i ' ' :\ \ \ ' ' 1 . \ . I ' \ / ' " I \ ' I ' \ ' 5 10 15 OWEN ENGINEERING GROUP 1525 Grand Avanue San Marcos, CA 92089 Telephone: (780) 471.«>00 Fax: (780) 471-08089 I Source of Material 1011.2 DeaclipUon of Material . Teat Method A8TM D11117 Method A ' ' TEST RESULTS \ ' \ Maximum Dry Danslty 123.S PCF i\ Optimum Water Content 13.0 % ' \ \ \ ' ' ' ' ATIERBERG LIMITS ' i I\ J:b_ PL ~ I\ \ ' ' \ CUIV8S of 100'II, Saturation ' ' for Speclflc Gravity Equal to: \ \. 2.80 \ ' ' I\. 2.70 ' ' 1, 2.80 ' " I\ ' ' I\ ' ' " I'\ ... ' ' ' ' ,, .. " I'-~ " " ' ' [' 20 25 30 35 40 45 WATER CONTENT,% MOISTURE-DENSITY RELATIONSHIP Project Walters Realdence Location: 5305 Carlsbad Blvd, Carlsbad, CA Number. I I I I I I I I I I 11 I 1 , I I :1 II 1 11 I l I I I I U.S. SEVE OPENING N INCHES I U.S. SIEVE NUMIIERS I HYDROMETER 8 4 2 1.5 1 3/4 112311 3 4 e 110 141e 20 30 40 150 1111 100140200 100 I I ! I i I I ' -! I I I I ~ I 95 ! I I I j 90 ! I 85 ' ! ! i 80 ! ! i ' ! 75 ! If 1 ' 70 ! j ! I I I 65 i ' !c I ! !2 80 ! UJ :!l: 55 i:i ! ' ffi 50 I if ! I 1! !z 45 I Ii ! UJ l I ~ 40 ' UJ I j 1.1 ! I .. I ' ,I 35 ' ' i i ,, ! i I ' I\ ! ! 30 i 11 ' i ! I 25 ' I ! ! ,I I l ! 20 I ! I ' \ i ,! ! 15 \ ' i i I; ! 10 " ' ' I Ii I ' ! 5 I I! ! 0 I; ! 100 10 1 0.1 0.0, 0.001 GRAIN SIZE IN MIWMETERS I COBBLES I GRAVEL 1-, SAND I SILT OR CLAY I -I fine -I fine Specimen ldenllflcaUon Cl8Alflcatlon LL PL Pl Cc Cu • 101 10.0 POORLY GRADED 8AND(8P) 1.21 2.31 Ill 101 20.0 POORLY GRADED 8AND(8P) 0.90 2.71 t Specimen ldentiflcsUon 0100 060 030 010 %Gravel %Sand %Slit %Clay ~. 101 10.0 2 0.20t 0.10 o.ou o.o 111.3 4.7 6 0.241 0.1117 0.0 ~ Ill 101 20.0 2 0.437 H.7 3.3 !! ~ l Owen Engineering Group GRAIN SIZE DISTRIBUTION I 1525 Grand Avenue Project: Walters Residence tm San Marcos, CA 90069 ! Telephone: (780) 471-eDOO Loca11on: 5305 Carlsbad Blvd, Carlsbad, CA Fax: (760) 471.eo96 Number: I I I I I , I I I I I I I I I ! I I I I I g ,: -C • --i ! 3: I !'l I U.S. SIEVE OPENING IN IIICHt!S I U.S. SIE\IE NUMBERS I HYDROMETER 8 4 3 2 1.5 1 314 1123111 3 • 8 9101418 20 30 40 80 80 100140200 100 I i I I I r I I .... " I I I I ~ I 95 ' ! / Ii I Ii 90 j ! I\ · 1V\1 i 85 ' i Ii i\ ' 80 i Ii ' ll i ! ! 75 I ' I i i 70 i i ! 85 " !i: ! 11 £! 60 i w l j : 55 j I! i 1"\ \ ffi 50 1! ! l ll Ii I \ \ !z 45 H ' 11 ' l \ w ! i l;1 40 1! ,! ,, Ii I \\ w i a.. ! Ii 35 I Ii ! \ I Ji i 30 I I• i I \ i I! ! 25 i Ii ! i \, ! 1! 20 I i i \ i I i I ! 15 i i l i II, l ' 10 i i I I ! 5 ' I I I ! 0 ! 100 10 1 0.1 0.01 0.001 GRAIN SIZE IN MIWMETERS I COBBLES I GRAVEL 1 ...... , SAND I SILT OR CLAY I ...... I llne -I fine Spechnenldentlllcation Cl11881flcaUon LL PL Pl Cc Cu • 102 10.0 Ill 102 20.0 0.97 2.89 1/J,. 102 30.0 * 102 40.0 0 102 50.0 Specimen ldenllllcsllon 0100 080 030 010 %Gravel %Sand %Silt %Clay • 102 10.0 8.3 0-'33 0.234 o.o Ill 102 20.0 2 0.3M 0.20I 0.123 0.0 92.1 7.9 1/J,. 102 30.0 2 0.21 0.0 14.9 35.1 * 102 40.0 4.75 0.313 0.109 o.o 75.9 24.1 0 102 50.0 2 0.411 0.193 o.o U.7 14.3 Owen Engineering Group GRAIN SIZE DISTRIBUTION 1525 Grand Avenue Project: Walters Rnklence DEG San Marcos, CA 90069 Telephone: (760) 471-8000 Location: 5305 Carlsbad Blvd, Carlsbad, CA Fax: (760) 471-6096 Number. I I I I I . I I I I . I I ' I I I I I I I i I I I I I I I ' I I I I ' I I 1 I ' ! ! I ' i i I ' I ' I I I ' I I ' I I -~ ,\ .. ,,,.,.....,, APPENDIX» GENERAL EARTHWORK AND GRADING SPECIFICATIONS I I I I I I I I I I I I I , I ., iJ ' I I I I I I GENERAL EARTHWORK AND GRADING SPECIFICATIONS 1.0 GENERAL INTENT These specifications present general procedures and requirements for grading and earthwork as shown on the approved grading plans, including preparation of areas to be filled, placement of fill, installation of subdrains, and excavations. The recommendations contained in the geotechnical report are a part of the earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case of conflict. Evaluations performed by the consultant during the course of grading may result in new recommendations, which could supersede the specifications and/or the recommendations of the geotechnical report. 2.0 EARTHWORK OBSERVATION AND TESTING Prior to the commencement of grading, Owen Engineering Group (soils engineer and engineering geologist, and their representatives) shall be employed for the purpose of observing earthwork procedures and testing the fills for conformance with the recommendations of the geotecbnical report and these specifications. It will be necessary that the consultant provide adequate testing and observation so that he may evaluate that the work was accomplished as specified. It shall be the responsibility of the contractor to assist the consultant and keep him apprised of work schedules and changes so that he may schedule his personnel accordingly. It shall be the sole responst'bility of the contractor to provide adequate equipment and methods to perform the work in accordance with applicable grading codes or grading plans. If: in the opinion of the consultant, unsatisfactory conditions, such as questionable soil, poor moisture conditioning. inadequate compaction, adverse weather, etc., are resulting in a quality of work less than required in these specifications, the consultant will be empowered to reject the work and recommend that construction be stopped until the unsatisfactory conditions are rectified. Maximum dry density tests used to determine the degree of compaction will be performed in accordance with the ASTM D1557-91 American Society for Testing and Materials test method. 3.0 PREPARATION OF AREA TO BE FILLED 3.1 Clearing and Grubbing All brush, vegetation and debris shall be removed or piled and otherwise disposed of 3.2 Processing The existing ground, which is determined to be satisfactory for support of fill shall be moisture conditioned. Existing ground, which is not satisfactory shall be over-excavated as specified in the I I I I I I I I I I I I 11 I I I I I I I following section. Scarification shall continue until the soils are broken down and free of large clay lumps or clods and until the working surface is reasonably uniform and free of uneven features which would inhibit uniform compaction. 3.3 Over-excavation Soft dry, spongy, highly fractured porous and otherwise unsuitable ground extending to such a depth that surface processing cannot adequately improve the condition, shall be over-excavated down to the :firm ground, as approved by the geotechnical consultant. When Cut/fill daylight line is located within a building pad area, the cut section shall be undercut a minimum of3 feet and recompacted to 90".lo relative compaction as directed by the geotechnical engineer. 3.4 Moisture Conditioning Over-excavation and processed soils shall be watered, dried-back, blended, and/or mixed as required to attain uniform moisture content near optimum moisture as determined as ASTMD1557-91. 3.5 Recompaction Over-excavation and processed soils which have been properly mixed and moisture conditioned shall be recompacted to a minimum relative compaction of 95 percent of the maximum dry density as determined by ASTM D1557-91. 3.6 Benching Where fills are to be placed on ground with slopes steeper than 5: 1 (horizontal to vertical units), the ground shall be stepped or benched. The lowest bench (keyway) shall be a minimum of 15 feet wide, shall be at least 2 feet deep, shall expose :firm material, and shall be approved by the consultant. Other benches shall be excavated into firm material for a minimum width and height of 4 feet. Ground sloping flatter than 5: 1 shall be benched of otherwise over-excavated when considered necessary by the consultant. 3. 7 Approval All areas to receive fill, including processed areas, removal areas, and keyways, shall be approved by the consultant prior to fill placement. 4.0 FILL MATERIAL 4.1 General Materisl to be placed as fill shall be free of organic matter and other deleterious substances, and shall be approved by the consultant. Soils of poor gradation, expansion, or strength characteristics shall be placed in areas designated by the consultant or shall be mixed with other soils to serve as satisfactory fill material. • I ;, I I I I I I I I I I I ii I I I I I I I 4.2 Ovenize Oversize material defined as rock or other irreducible material with any dimension greater than 12 inches, shall not be buried or placed in fills, unless, the location, materials, and disposal methods are specifi~ approved by the consultant. Oversized disposal operations shall be such that nesting of oversize material does not occur, and such that the oversize material is completely surrounded by compacted or densified fill. Oversized material shall not be placed with 10 feet vertically of finish grade or construction, unless specifically approved by the consultant. 4.3 Import If importing of fill material is required for grading, the import material shall meet the requirements of Section 4 .1. 5.0 FILL PLACEMENT AND COMPACTION 5.1 Fill lifts Approved fill material shall be placed in areas prepared to receive fill in layers not exooecting 8-inches in compacted thickness. The consultant may approve thicker lifts if testing indicates the grading procedures are such that adequate compact is being achieved with lifts of greater thickness. Each layer shall be spread evenly and shall be thoroughly mixed during spreading to attain uniformity of material and moisture in each layer. 5.2 Fill Moisture Fill layers at a moisture content less than optimum moisture shall be watered and mixed and wet fill layers shall be aerated by scarification or shall be blended with drier material. Moisture conditioning and mixing of fill layers shall continue until the fill material is at uniform moisture content at or near optimum. 5.3 Compaction of Fill After each layer has been evenly spread, moisture conditioned, and mixed, it shall be uniformly compacted in accordance with the table presented below. DESCRIPTION COMPACTION Cllll'BlllA Fill Benca1h Footings aod S1ructuml Building Members 90% RotainiDg Wall Ba:ltfill 90% U1ility Tmu:h Bactfill NOIHlluctunll 9<W, Structund 90% Note: Comp11&)11on cntcria baaed on ASTM DI SS7 • I I I I I I I 11 11 I I I I I I I ,I !1 I l 1 Compaction equipment shall be adequately sized and shall be either specifically designed for soil to be compacted or of proven reliability to efficiently achieve the specified degree of compaction. 5.4 Fill Slopes Compacting of slopes shall be accomplished, in addition to normal compacting procedures, by backrolling ofslopes with sheepsfoot rollers at frequent increments of2 to 3 feet in fill elevation gain, or by other methods producing satisfactory results. At the completion of grading, the relative compaction of the slope out to the slope face shall be at least 95 percent. 5.5 Compaction Testing Field tests to check the fill moisture and degree of compaction will be performed by the consultant. The location and frequency of tests shall be at the consultant's discretion. In general, the tests will be taken at an interval not exceeding 2 feet in vertical rise and/or 1,000 cubic yards of embankment. 6.0 SVBDRAIN INSTALLATION Subdrain systems, if required, shall be installed in approved ground to conform to the approximate alignment and details shown on the plans or herein. The subdrain location or materials shall not be changed or modified without the approval of the consultant. The consultant, however, may recommend, and upon approval, direct changes in subdrain line, grade or material. All subdrains should be surveyed for line and grade after installation and sufficient time shall be allowed for the surveys, prior to commencement of filling over the subdrains. All "canyon subdrain and replacement-fill backdrain outlets shall be located, excavated, and exposed upon completion of grading and after any slope modifications (i.e., landscaping) in order to ensure proper drainage and to minimize the potential for saturation of fills and/or slope failures. 7.0 EXCAVATION Excavation and cut slopes will be examined during grading. If directed by the consultant, further excavation or over-excavation and refilling of cut areas shall be performed, and/or remedial grading of cut slopes shall be performed. Where fill-over-cut slopes are to be graded, unless otherwise approved, the cut portion of the slope shall be made and approved by the consultant prior to placement of materials for construction of the fill portion of the slope. • D I I I I I I I I I I I I I I I I I I J DENSE OfJ-iSE ~outlO co\lER \ ... ---· I I . L-