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HomeMy WebLinkAboutX2007-1463 - SoilsCOAST GEOTECHNICAL, INC. X'2�v& q —(W lei 3 14747 Artesia Blvd., Saito ;-L,, La PP� AP�", 0692t, %r'(T 14) 921-2827I= (714) 821-0179 `0M ONJU1-MNION a hlalVEV4 November 15, 2005 er aauuulplo ao sepoo gonS to Suelslhad ogt 1e0uen W.O.266704-03 'pllLA eq II 1� 6aoueul I0 is o a9alolA Ob h1PcgEn z aAfJ ab po unsold a{ularsd oN a ,ruspsua sepoo olgnalldN otil 10 uopnlr rN u tl2dp a Su lura5 ao aou nssl r;y1. esouI10 pAoadde uo Ps�q Mr. & Mrs. Jason Pouliot ,o A pcba;duaa oµ ul su0llsdclh opoo fu 1guletis Pt1113 W^al 4824 Cortland Drive sduuylnsuao S,bl Puo f910 A,lu-rr pnoIvan axiao,oA ° sooafiu'aapunoaos;j Corona del Mar, California uollonaisuoo bulcuauawta nq i?` I>' v'`'':''' uuso puu opoa olquallddU ag101 SiOarlsob lia({dwo0 {4c�1 I puaal ru prorSptrD011aniascerCl puesucld,}.I R9t^u'I``llDat�r�I UD �fi}ab'1°for 'Bedrock, Proposed Pile selaue6N pue Syuoua{a dd{a t1pTPorCd akrgt6YetesY1 at 4824 Cortland Drive, aaunnssr lluued .+01 pap' D", �roua del' Mar, a(lforrii4 Reference: . ^ I'll` r� la k4ln (tq paldope Sonoo I r , i : I Ia;lll Sgrs ui :aq et Pun"1 Geologic and Geotechnical Engineering Investigaton ;for Proposed Semi -Subterranean Garage, Pool and Guest House at 4824 f(ttscCfard&' Drive, Corona del Mar, California; by COAST GEOTECHNICAL, dated December 30, 2004. Dear Mr. & Mrs. Pouliot: In accordance with pile wall plans, two borings #5 & #6 have encountered a very hard layer of siliceous sandstone at 33 feet and 35 feet, respectively, below an elevation of 115 ft. Bedrock has been encountered at an approximate elevation of 99, providing 1711 and 19 ft. embedment into bedrock. Structural plans are requiring 21 feet of embedment into bedrock. The underlying bedrock is mainly comprised of thinly bedded siltstone and sandstone which is moderately hard to a elevation of about 89 then becomes hard to very hard mainly comprised of sandstone. The siliceous layer does not appear to be continuous since boring have been completed on either side of #5 & #6 to design depth. We offer the following design increases in light of the materials encountered. Passive pressure increasing at the rate of 500 pounds per square foot of depth to a maximum value of 5,000 pounds per square foot, may be used for competent bedrock to elevation 89 and 750 pounds per square foot of depth to a maximum value of 7,500 pounds per square foot, may be used for bedrock at the elevation below 89.E We hope this will satisfy the structural design although alternatives such as using diffe rft drilling equipment, enlarging the diameter of the borings, deepening adjacent piles or adding.a- t e may also be considered. We appreciate this opportunity to be of service to yg; OF NEWPORT B CH BUILDING d fARTM T �S' '4 APPROVAI. OF THFRG 0. — 11 � � �,N.t Respectfully submitted: COAST GEOTECHNICAL, INC. ���uT{irvcta: PLANS AND POLIO. �Q PFRMITTFE'SAOKN0WLEDOI,7ENT; SF;rMEIVT SI(_NAI �PAN� ORKs' Ming-Tarng Chen h fie' sFrvirEs _--_ RCE 54011 — No. 54011FM;-______ lr COAST GEOTECHNICAL, 14747 Artesia Blvd., Suite 1-D, La Mirada, CA 90638 INC. Pic (714) 621-0169 or (714) 821.2827 Fax: (714) 521.0179 November 15, 2005 Mr. & Mrs. Jason Pouliot 4824 Cortland Drive Corona del Mar, California Reference: Geologic Pool an( Dear Mr. Ry �\ In accordance with -pile sandstone at 33 feet and W.O.266704-03 Subject: Lateral Design for Bedrock, Proposed Pile ryoF Supported Shotcrete Wall at 4824 Cortland Drive, / rN� N�wnopr Corona del Mar, California Nof P qR CTq D 8 N0y8�liAllyD, � C r G N'S AN NY 80 Cr CO SPAR P�0�1 fW/Proposed Semi -Subterranean Garage, ND,.P��°N dfp�zbRdel Mar, California; by COAST un a at an approximate elevation of 99, prow ing Dirtr4`19 en e requiring 21 feet of embedment into bedrock..'6�9�,/fl gLyt3hed bedded siltstone and sandstone which is moderately a ele-i atil very hard mainly comprised of sandstone. The siliceous Jaye oes boring have been completed on either side of #5 & #6 to design depth. ntered a very hard layer of siliceous 15 ft. Bedrock has been encountered nt into bedrock. Structural plans are rock is mainly comprised of thinly >n of about 89 then becomes hard to not appear to be continuous since We offer the following design increases in light of the materials encountered. Passive pressure increasing at the rate of 500 pounds per square foot of depth to a maximum value of 5,000 pounds per square foot, may be used for competent bedrock to elevation 89 and 750 pounds per square foot of depth to a maximum value of 7,500 pounds per square foot, may be used for bedrock at the elevation below 89. We hope this will satisfy the structural design although alternatives such as using different drilling equipment, enlarging the diameter of the borings, deepening adjacent piles or adding a pile may also be considered. CHARLES ASBOTT ASSOCIATES APPROVED FOR PERMIT ISSUANCF We appreciate this opportunity to be of service to you. Respectfully suhnutted: COAST GEOTECHNICAL, INC. Ming-Tarng Chen RCE 54011 ISSUANCE OF A BUILDING PERMIT us_U UPON THESE PLANS IS RECOMMENDED SUBJECT TOZP,p!' ,�. uY r' AGENCIES AND AN`�C'::n4,rT!Ohs'�R APPLICABLE THE STAMPING OI- T HL C f AN. - "G DOCUMENTS SHALL NOTIO OF: ANY THE VIOLATION OF AN`! PRu+ SIONS OP ANY STATE APPROVAL LOCAL aniel E. Here Staff Geologist COAST GEOTECHNICAL Geologic and Geotechnioal Inv stigation �'coN`x: T TEtl1 P1: v af,E� BEACH- = ri-7'i� RFC `P ROVE pi Ai fOr RUG $61 i'IdIGIE� APPI]C 't' ` _ i,�ehrel Prop Garay at Ouse 4824 Cortland Drive Corona del Mar, California BY: COAST GEOTECHNICAL W. 0. 266704-01, dated December 30, 20%ARLes A6BOTT ASSOCIATES APPROVED FOR PERMIT ISSUANCE ISSUANCE OF A BUILDING PERMIT BASED UPON THESE PLANS IS RECOMMENDED SUBJECT TO APPROVAL BY OTHER APPLICABLE AGENCIES AND ANY CONDITIONS NOTED HEREIN. THE STAMPING OF THESE PLANS AND SUPPORTING DOCUMENTS FOR: SHALL NOT BE CONSTRUED TO PERMIT OR BE AN APPROVAL OF THE VIOLATION OF ANY PROVISIONS OF ANY STATE OR LOCAL LAW. �j Mr. &Mrs. Jason Poull'�rt ____—DAT.—aL.A...• D"1 4824 Cortland Drive Corona del Mar, CA 92626 COAST GEOTECHNICAL 14747 Artesia Blvd,, Suite 1-D, La Mirada, CA 90638 Ph: (714) 521-0169 or (714) 821-2827 Fax: (714) 821-0179 December 30, 2004 Mr. & Mrs. Jason Pouliot 4824 Cortland Drive Corona del Mar, California Dear Mr. & Mrs. Pouliot: W.O.266704-01 Subject: Geologic and Geotechnical Engineering Investigation for Proposed Semi - Subterranean Garage, Pool and Guest House at 4824 Cortland Drive, Corona del Mar, California Pursuant to your request, a geologic and geotechnical investigation has been performed at the subject site. The purposes of the investigation were to determine the general engineering characteristics of the earth materials on and underlying the project site and to provide recommendations for the design of foundations and underground improvements. The conclusions and recommendations contained in this report are based upon our understanding of the proposed development and analyses of the data obtained from our field and laboratory testing programs. PROJECT DESCRIPTION It is our understanding that the project will consist of a semi -subterranean garage with a living quarter above, a swimming pool, and guesthouse incorporating retaining walls. PROJECT WORK SCOPE The purpose of our services was to evaluate the project site soil and bedrock conditions and to provide geological and geotechnical engineering conclusions and recommendations relative to the proposed development. Our scope of services consisted of the following: 1. Review of available geotechnical reports. 2. A cursory geotechnical and geologic reconnaissance of the site and surrounding area. 3. Exploration of the site's subsurface earth material conditions by placement of borings. 4. Logging and collection of soil and bedrock samples. 5. Geotechnical laboratory testing of selected earth material samples obtained from the exploratory borings excavated for this project. 6. Engineering analyses of the data obtained from the exploration, review and testing programs. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 2 W.O. 266704 Geotechnical Investigation December 30 2004 7. A summary of our findings and recommendations in this written report. SITE CONDITIONS The project site is located at 4824 Cortland Drive in the Corona del Mar area of Newport Beach and is shown on the Site Vicinity Map, Plate 1. Existing site improvements consist of a single -story residence with attached garage, hardscape and landscape. The site is located on the north side of Cortland Drive and slightly elevated above Cortland Drive. The lot has an essentially level building pad and an ascending slope to the rear (northern) property boundary. The existing residence appears to be performing well. The slope is supported by a 3.5-foot high retaining wall at the toe of slope and the slope gradient is about 2:1 (H:V). The ascending slope rises above the pad level about 18 feet to the northern adjacent property. The slope shows evidence of surficial slumps and down slope creep although the retaining wall at the toe and patio at the top of slope appear to be performing satisfactorily. Site configuration is further shown on Plate 3. FIELD INVESTIGATION The field investigation was performed on December 10, 2004 and consisted of the excavation of three exploratory borings by hand auger equipment, at locations shown on the attached the Site Plan, Plate 3. As excavation progressed, personnel from this office visually classified the earth materials encountered and secured representative samples for laboratory testing. Undisturbed samples for detailed testing in our laboratory were obtained by pushing or driving a sampling spoon into the earth material. A solid -barrel type spoon was used having an inside diameter of 2.5 inches with a tapered cutting tip at the lower end and a ball valve at the upper end. The barrel is lined with thin brass rings, each one inch in length. The spoon penetrated into the soil below the depth of boring approximately six inches. The central portion of this sample was retained for testing. All samples in their natural field condition were sealed in airtight containers and transported to the laboratory. Descriptions of the earth materials encountered are presented on the attached Boring Logs, Plates 7, 8 & 9. The data presented on these logs is a simplification of actual subsurface conditions encountered and applies only at the specific boring locations and the date excavated. It is not warranted to be representative of subsurface conditions at other locations and times. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 3 W.O.266704 Geoteclmical Investigation December 30 2004 REGIONAL GEOLOGY Regional geology is presented on Plate 2, which shows the area to consist of non -marine terrace deposits underlain by sedimentary bedrock assigned to the Monterey formation. Regional adverse geologic conditions are not shown. LITHOLOGY Earth materials encountered within the exploratory borings were visually identified by a COAST GEOTECHNICAL geologist. The materials were classified as artificial fill, native terrace deposits and bedrock. The artificial fills (Af) encountered consisted of yellow brown silty sand, damp to wet, and loose to dense. The fill soil was encounter to depth of about two to six feet below existing grade. Native terrace deposits (Qtn) underlie the artificial fill and consisted of yellow brown to orange brown silty and clayey sand, generally moist and medium dense to dense. Bedrock encountered was assigned to the Monterey formation (Tm) and consisted of yellow - buff to orange brown siltstone, clayey, diatomaceous, moist and generally hard. Each boring was terminated due to refusal Earth materials are further described on the appended Boring Logs, Plates 7 through 9. Site geologic conditions correspond with regional conditions. Site geology is presented on _ Plate 3 along with an appropriate cross section shown on Plate 4. Site geology is considered favorable for the proposed development. GROUNDWATER Groundwater was not encountered during our exploratory work; however, seepage was encountered in one boring. It is not uncommon in the area for zones of saturation and/or perched waters to exist in permeable earth material as a result of heavy irrigation. SEISMICITY Southern California is located in an active seismic region. Moderate to strong earthquakes can occur on numerous local faults. The United States Geological Survey, California Division of Mines and Geology, private consultants, and universities have been studying earthquakes in Southern California for several decades. Early studies were directed toward earthquake COAST GEOTECHNICAL Mr. & Mrs. Pouliot 4 W.O.266704 Geotechnical Investigation December 30, 2004 prediction and estimation of the effects of strong ground shaking. Studies indicate that earthquake prediction is not practical and not sufficiently accurate to benefit the general public. Governmental agencies are shifting their focus to earthquake resistant structures as opposed to prediction. The purpose of the code seismic design parameters is to prevent collapse during strong ground shaking. Cosmetic damage should be expected. Within the past 33 years, Southern California and vicinity have experienced an increase in seismic activity beginning with the San Fernando earthquake in 1971. In 1987, a moderate earthquake struck the Whittier area and was located on a previously unknown fault. Ground shaking from this event caused substantial damage to the City of Whittier and surrounding cities. The January 17, 1994, Northridge earthquake was initiated along a previously unrecognized fault below the San Fernando Valley. The energy released by the earthquake propagated to the southeast, northwest, and northeast in the form of shear and compression waves, which caused the strong ground shaking in portions of the San Fernando Valley, Santa Monica Mountains, Simi Valley, City of Santa Clarita, and City of Santa Monica. Southern California faults are classified as: active, potentially active, or inactive. Faults from past geologic periods of mountain building, but do not display any evidence of recent offset, are considered "inactive" or "potentially active". Faults that have historically produced earthquakes or show evidence of movement within the past 11,000 years are known as "active faults". The nearestknown active fault is the Newport -Inglewood Fault about 3.5 km to the southwest, as shown on Plate 5. The principal seismic hazard to the subject property and proposed project is strong ground shaking from earthquakes produced by local faults. It is likely that the subject property will be shaken by future earthquakes produced in Southern California. Secondary effects such as surface rupture, liquefaction, or flooding, are not considered probable. SEISNUC HAZARDS The site is not mapped as being in a seismic hazard zone subject to seismic induced hazards by the State of California. See Figure 6, "Seismic Hazard Zone Map" Laguna Beach Quadrangle, dated April 15, 1998. Based on near surface bedrock and lack of groundwater, the liquefaction potential for the site is remote. SLOPE STABILITY The slope stability analysis utilizes residual reshear strength values of in -situ samples obtained from the exploratory excavations. The slope stability analyses are presented Plates 13 &14. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 5 W.O. 266704 Geotechnical Investisation December 30 2004 The analyses show a factor of safety above the required 1.5 for gross slope stability. The surficial slope stability is considered unstable and subject to slumping and down slope creep with elevated moisture content. This condition is not adverse to site development. Improvement of site drainage, retaining wall construction and proper slope maintenance would improve this condition. Slope maintenance guidelines are appended. If there are areas where the surficial soil is not removed and recompacted, structures will need to be designed to resist a creep load of 1000 psf, per foot of depth for the upper three feet of soil on the existing slope. GEOTECHNICAL DISCUSSION Development as currently proposed will remove significant portions of the surficial soil on the slope. The guesthouse and pool will incorporate retaining walls into the structure and shall be designed to support the slope. Deepened foundations will be needed so that the entire guesthouse and pool is supported on bedrock. The basement garage excavation of the residence should encounter bedrock and shall be overexcavated to derive support from engineered fill. The guesthouse and pool are expected to separate from the existing residential structure. Pile foundations will most likely be utilized for the structures on the slope. It is our understanding that shoring design will be incorporated into the building wall and pool design. Pile foundations will be embedded a minimum of five feet into competent bedrock. The ascending slope is subject to surficial slumps and creep. Surficial stability can be improved through managed slope maintenance, control of drainage, and proper landscaping. Structures located on the slope will need to be designed for a creep load. Development will require shoring where safe construction cuts cannot be made due to physical site constraints. Shoring may be incorporated into permanent wall designs. CONCLUSIONS AND RECOMMENDATIONS Development of the site as proposed is considered feasible from a soils engineering standpoint, provided that the recommendations stated herein are incorporated in the design and are implemented in the field. These recommendations are subject to change based on review of grading and foundation plans. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 6 W.O. 266704 Geotechnical Investieation December 30 2004 GRADING RECOMMENDATIONS Structures that are to be removed shall be demolished and all debris hauled from the project site. Where trees are removed, the void created by the removal of the root ball shall be backfilled with fill soils compacted to a minimum of 90% relative compaction. Existing utility lines shall be removed, crushed in place, or filled with a lean concrete slurry mix. Grading will be necessary to excavate and recompact existing loose surficial soil on the slope for concrete slab support and as retaining wall backfill; the foundations of the structures on the slope will penetrate surficial soils and derive support from bedrock. Based on field exploration, depths of removal are estimated at three to four feet below existing grade, but will be field adjusted dependent on conditions encountered. Grading may encounter wet soil conditions. Thorough mixing and aeration will be needed to reduce the high moisture content closer to an optimum condition. As an alternate to grading, the interior concrete slab areas may be designed as structural slabs supported by a pile foundation system. Grading will be necessary for the semi -subterranean garage addition to provide engineered fill soil for support. The garage excavation is expected to expose bedrock which shall be overexcavated at least twelve inches below propose foundations. The use of keys in basement wall foundations should be avoided. Excavation bottoms shall be observed and approved by a representative of COAST GEOTECHNICAL prior to processing. Upon approval, the excavation bottoms shall be scarified six inches, moisture conditioned or stabilized as required, and rolled to a minimum of 90% relative compaction. Subsequent fill soils shall be placed in six to eight inch lifts, moisture conditioned as required and compacted to a minimum of 90% relative compaction. This process shall be followed to finish grade. GENERAL GRADING NOTES The entire grading operation shall be done in accordance with the attached "Specifications for Grading". COAST GEOTECHNICAL Mr. & Mrs. Pouliot 7 W.O.266704 Geotechnical Investigation December 30.2004 Any import fill materials to the site shall not have an expansion index greater than 20, and shall be tested and approved by our laboratory. Samples must be submitted 48 hours prior to import. Grading and/or foundation recommendations are subject to modification upon review of final grading and structural plans by the Geotechnical Engineer. Please submit plans to Coast Geotechnical when available. CONSTRUCTION CUTS Construction cuts on the order of six to eight feet are anticipated for the guesthouse, pool and basement garage construction. Shoring will be required for the cuts into the ascending slope. Shoring may not be needed for the basement garage addition although final grading plans will need to be reviewed and evaluated. Where construction cuts cannot be made at maximum 3/4:1 (H:V) gradient shoring shall be utilized. All cuts and shoring design shall take into account removals needed for foundations and or grading. These recommendations are subject to change based on field conditions exposed during grading. The project geologist shall observe all cuts during excavation. SHORING Prior to, during and after shoring has been installed the adjoining properties and structures should be photo -documented, and surveyed. Temporary shoring shall be designed for an equivalent fluid pressure of 30 pcf plus any surcharges. Permanent shoring incorporated into the building and pool on the slope shall be designed for an equivalent fluid pressure of 60 pcf plus any surcharges. Shoring shall be constructed by drilling holes to the required depth, placement of beams, backfill of annulus between beams and the boring hole and wood lagging with one sack slurry or concrete if directed by the structural engineer. No vibratory equipment shall be utilized for installation. Water seepage into the hole will most likely occur. A tremie tube placed to the bottom of the hole will be required for slurry placement if water accumulates. The shoring contractor is advised that casing will most likely be needed to maintain an open hole. Placed wood lagging shall maintain a positive contact with the required construction cut. Any voids shall be in -filled with slurry. During placement of lagging, unsupported vertical cuts, between piles, shall be limited to five vertical feet. Coast Geotechnical shall monitor all phases of shoring installation. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 8 W.O.266704 Geotechnical Investigation December 30, 2004 FOUNDATIONS Foundations for the guesthouse and pool shall consist of 24-inch diameter drilled friction piles embedded a minimum of five feet into bedrock. Piles may be designed in accordance with the attached pile capacity Chart, Plate 15. The subterranean garage may use continuous footings founded in engineered fill soil ..minimum 6f- 24 inches. These foundations may utilize an allowable bearing value of 1500 psf. Continuous footings shall be reinforced with a minimum of four #5 Cars, two top and two bottoms. This value is for dead plus live load and may be increased 1/3 for total including seismic and wind loads where allowed by Code. The foundations on the slope shall be designed for a creep load of 1000 pounds per foot of intercept within the upper three feet of the existing soil on the slope. During the drilling of the piles a representative of Coast Geotechnical shall be present to verify conditions encountered and compliance with geotechnical recommendations. Hard siliceous zones of bedrock may be encountered and seepage water should be expected. Terrace sands are subject to caving, casing to the bedrock contact may be needed. IW.11 lal:: 11*1 11"u Lateral restraint at the base of footings and on slabs may be assumed to be the product of the dead load and a coefficient of friction of .30. Passive pressure on the face of footings may also be used to resist lateral forces. A passive pressure of zero (0) at the finish grade, increasing at the rate of 300 pounds per square foot of depth to a maximum value of 3,500 pounds per square foot, may be used for bedrock and engineered fill at this site. If passive pressure and friction are combined when evaluating the lateral resistance, the value of the passive pressure should be limited to 2/3 of the values given above. CREEP LOAD Foundations placed within fifteen feet of the top of slope and on the descending slope shall incorporate a creep load of 1,000 psf for the upper three feet of existing material. SETBACK Foundations shall maintain a minimum setback distance of ten feet as measured from the bottom outside footing edge horizontally to a competent slope surface. Competent slope surface is determined by the project geologist and is not always the same as the exposed slope surface. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 9 W.O.266704 Geotechnical Investigation December 30 2004 BASEMENT WALL DESIGN/ Foundations for basement walls may utilize previously stated bearing values and lapral pressures. Basement walls shall be designed for an equivalent fluid pressure of 60 pcf. Permanent shoring may be incorporated into the basement walls. A shoring design pressure diagram is attached as Plate 16. Wall backfills shall consist of non -expansive material. All backfill material shall be compacted to a minimum of 90% relative compaction. Basement walls shall be waterproofed to the degree desired by the client. WATERPROOFING There is an inherent risk with moisture problems when constructing below grade rooms. The geotechnical consultant is only responsible for identification of adverse moisture conditions, which could impact below grade rooms. When this condition is present, a qualified person should design the waterproofing for the basement floor and walls accordingly. RETAINING WALLS Freestanding retaining walls may be founded in compacted fill, or competent earth material utilizing previously stated bearing values. If founded on both a construction joint shall be placed at the transition. Retaining walls with level backfill may be designed for an equivalent fluid pressure of 40 pcf, and for 2:1/H:V) backfill 55/pcf. Retaining walls shall also accommodate any surcharges from adjacent structures. The retaining walls shall be designed with adequate drainage to prevent the buildup of hydrostatic pressure. A subdrain shall be placed at the base of the retaining wall. The subdrain shall be a minimum four -inch diameter, perforated SDR 35 or SCH 40 pipe, surrounded with a minimum of one cubic foot of graded gravel per lineal foot of pipe. As an alternate to graded rock 3/4-inch gravel wrapped in filter fabric may be utilized. Retaining wall backfill shall be placed in 6 to 8 inch loose lifts and mechanically compacted to a minimum of 90% relative compaction. Backfills require testing at 2-foot vertical intervals during placement. Onsite soils approved by COAST GEOTECHNICAL are acceptable for use as backfill. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 10 W.O.266704 Geotechnical Investigation December 30 Mn- Footing excavation, subdrain placement, and compaction of backfills requires observation and approval by COAST GEOTECHNICAL. On -site material is adequate for use as backfill. The backfill shall be compacted to a minimum of 90% relative compaction, and requires testing at a minimum of two foot vertical intervals during fill placement. POOL RECOMMENDATIONS Due to inherent differences in supporting capacity of soil and bedrock, it is undesirable to have structures supported by dissimilar materials or undocumented fills. The pool should be a freestanding design, supported entirely by documented fill soil or bedrock but not a combination of supporting materials. Pool walls should be designed to support the water, having a density of 62.4 pounds per cubic foot without bearing from the adjacent soil. The walls should be able to support the adjacent backfill soil when the pool is empty. The earth pressure may be calculated as an equivalent fluid pressure of 62.4 pcf, plus the lateral pressure due to any superimposed surcharge when the pool is empty. Expansion joints should be placed between the deck and the pool. The pool excavation shall be observed by COAST GEOTECHNICAL to verify acceptable conditions. SUBDRAINS Subdrain systems shall'be installed behind both free standing retaining walls and basement walls and at a minimum they shall consist of four inch diameter SCH 40 or SDR 35 perforated pipe surrounded with one cubic foot, per lineal pipe foot, of 3/4 inch gravel. The gravel shall be wrapped in filter fabric. Outlet pipes shall be solid pipe of similar material. SETTLEMENT The maximum total post -construction settlement is anticipated to be on the order of one half inch. Differential settlements are expected to be less than 1/2 inch, measured between adjacent structural elements, over a horizontal distance of forty feet. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 11 W.O. 266704 Geotechnical Investieation December 30 2004 SEISMIC DESIGN Based on the 2001 CBC the site is assigned to Zone 4, soil profile Sd. The near source fault is the Newport -Inglewood Fault, about 3.5 km away. The Newport -Inglewood Fault is a Type B fault with a magnitude of 6.9. The following seismic factors may be utilized in design: ,'-'Na = 1.15 Nv = 1.40 Ca = 0.506 Cv = 0.896 SHRINKAGE Onsite soils are expected to have shrinkage of about 10 to 15% during earthwork. FLOOR SLABS The surface soils are non -plastic. Minimum geotechnical recommendations for slab design is a /four -inch actual thickness, placed over four inches of clean compacted sand, with #33 bars at 18 inches on center each way. The slab shall be supported on engineered fill compacted to a minimum of 90% relative compaction. Subgrade soil should be kept moist prior to casting the slab. However, if the soils at grade become disturbed during construction, they should be brought to approximately optimum moisture content and rolled to a firm, unyielding condition prior to placing concrete. In areas where a moisture sensitive floor covering will be used, a vapor barrier consisting of a plastic film (6 ml polyvinyl chloride or equivalent) should be used. The vapor barrier should be properly lapped and sealed. Since the vapor barrier will prevent moisture from draining from fresh concrete, a better concrete finish can usually be obtained if at least -inches of sand is spread over the vapor barrier prior to placement of concrete. EXPANSIVE SOILS Results of expansion tests indicate that the near surface soils have a very low expansion potential. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 12 W.O.266704 Geotechnical Investigation December 30 2004 UTILITY LINE BACKFILLS All utility line backfills, both interior and exterior, shall be compacted to a minimum of 90% relative compaction and shall require testing at a maximum of two -foot vertical intervals. HARDSCAPE Hardscape subgrade areas shall exhibit a minimum of 90% relative compaction to a depth of one foot. These areas should be tested just prior to pouring concrete. Hardscape should be at least four inches thick and reinforced with #3 bars on 18-inch centers, both ways. CORROSION ANALYSIS Typical onsite soils showed a soluble sulfate content of 66 ppm, which per Table 19-A-4 of the 2001 CBC is a negligible exposure. Special concrete design is not required. Type ]I concrete may be utilized. 11 DRAINAGE Positive drainage should be planned for the site. Drainage should be directed away from structures via non -erodible conduits to suitable disposal areas. The structure should utilize roof gutters and down spouts tied directly to yard drainage. Drainage shall not be directed onto or over slopes. Unlined flowerbeds, planters, and lawns should not be constructed against the perimeter of the structure. If such landscaping (against the perimeter of a structure) is planned, it should be properly drained and lined or provided with an underground moisture barrier. Irrigation should be kept to a minimum. Minimum drainage shall be one percent for hardscape areas and two percent for landscape areas. Drainage swales and pad berms shall be in accordance with City guidelines. TEMPORARY CUTS Temporary construction cuts are anticipated for grading and construction of the project. The following recommendations are for unsurcharged conditions, and are subject to modification based on field observations. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 13 W.O. 266704 Geotechnical Investigation December 30 2004 Temporary cuts for earthwork shall be made no steeper than a 3/4:1 gradient. Cuts that cannot be made in this manner shall be supported with designed approved shoring. No cuts shall be allowed which would remove lateral support from adjacent properties, structures, or public right of ways. OSHA guidelines shall be followed where workers are to enter confined spaces, trench work, or excavations. All cuts shall be observed by the project geologist or geotechnical engineer. Field observations will determine final construction cuts allowed. If adverse conditions are exposed, remedial measures will be recommended. SUPPLEMENTAL CONSULTING During construction, a number of reviews by this office are recommended to verify site geotechnical conditions and conformance with the intentions of the recommendations for construction. Although not all possible geotechnical observation and testing services are required by the City of Newport Beach, the following site reviews are advised, some of which will probably be required by the City: Site grading Foundation excavation review for the all structures Reinforcement placement for all foundations Slab subgrade compaction testing Presaturation checks for all slabs Slab steel placement, primary and appurtenant structures Compaction of utility trench backftll Hardscape subgrade testing Retaining wall backfills Subdrain placement Temporary construction cuts V OAST GEOTECHNICAL Mr. & Mrs. Pouliot 14 W.O. 266704 Geotechnical Investigation December 30 2004 AGENCY REVIEW All soil, geologic, and structural aspects of the proposed development are subject to the review and approval of the governing agency(s). It should be recognized that the governing agency(s) can dictate the manner in which the project proceeds. They could approve or deny any aspect of the proposed improvements and/or could dictate which foundation and grading options are acceptable. Supplemental geotechnical consulting in response to agency requests for additional information could be required. ENGINEERING CONSULTATION, TESTING AND OBSERVATION We will be pleased to provide additional input with respect to foundation design once methods of construction and/or nature of imported soil has been determined. Grading and foundation plans should be reviewed by this office prior to commencement of grading so that appropriate recommendations, if needed can be made. Areas to receive fill should be inspected when unsuitable materials have been removed and prior to placement of fill, and fill should be observed and tested for compaction as it is placed. LINIITATIONS This report presents recommendations pertaining to the subject site based on the assumption that the subsurface conditions do not deviate appreciably from those disclosed by our exploratory excavations. Our recommendations are based on the technical information, our understanding of the proposed construction, and our experience in the geotechnical field. We do not guarantee the performance of the project, only that our engineering work and judgments meet the standard of care of our profession at this time. In view of the general conditions in the area, the possibility of different local soil conditions may exist. Any deviation or unexpected condition observed during construction should be brought to the attention of the Geotechnical Engineer. In this way, any supplemental recommendations can be made with a minimum of delay necessary to the project. If the proposed construction will differ from our present understanding of the project, the existing information and possibly new factors may have to be evaluated. Any design changes and the finished plans should be reviewed by the Geotechnical Consultant. Of particular importance would be extending development to new areas, changes in structural loading conditions, postponed development for more than a year, or changes in ownership. COAST GECTECHNICAL Mr. & Mrs. Pouliot 15 W.O.266704 Geotechnical Investigation December 30 2004 This report is issued with the understanding that it is the responsibility of the owner, or of his representative, to ensure that the information and recommendations contained herein are called to the attention of the Architects and Engineers for the project and incorporated into the plans and that the necessary steps are taken to see that the Contractors and Subcontractors carry out such recommendations in the field. We appreciate this opportunity to be of service to you. Respectfully submitted: COAST GEOTECHNICAL Ming-Tamg Chen RCE 54011 No. 54011 P. 12-31 Todd D. t a4 G60 Daniel E. Herc CEG 1 p. 4/06 Staff Geologist 4 TODC D. ,iO1JEF.AL sn M i914 • u fu n� �tuw31 �_ COAST GEOTECHNICAL Mr. & Mrs. Pouliot 16 W.O. 266704 Geotechnical Investigation December 30 2004 APPENDIX A This appendix contains a description of the field investigation, laboratory testing procedures and results, site plan, and expansive soil recommendations. FIELD INVESTIGATION Field investigation was performed on December 10, 2004, consisting of the excavation of three exploratory borings by hand auger equipment at locations shown on the attached site plan. As the excavations progressed, personnel from this office visually classified the soils encountered, and secured representative samples for laboratory testing. Undisturbed samples for detailed testing in our laboratory were obtained by pushing or driving a sampling spoon into the material. A solid barrel -type spoon was used having an inside diameter of 2.5 inches with a tapered cutting tip at the lower end and a ball valve at the upper end. The barrel is lined with thin brass rings, each one inch in length. The spoon penetrated into the soil below the depth of the excavation approximately 6 inches. The central portion of this sample was retained for testing. All samples in their natural field condition were sealed in airtight containers and transported to the laboratory. Descriptions of the soils encountered are presented on the attached Boring Logs. The data presented on these logs is a simplification of actual subsurface conditions encountered and applies only at the specific boring locations and the date excavated. It is not warranted to be representative of subsurface conditions at other locations and times. LABORATORY TESTING Field samples were examined in the laboratory and a testing program was then established to develop data for preliminary evaluation of geotechnical conditions. Field moisture and dry densities were calculated for each undisturbed sample. Maximum density -optimum moisture relationships were established for use in evaluation of in - situ conditions and for future use during grading operations. Direct shear tests were performed on specimens at near saturation under various normal loads. The results of tests are based on ultimate residual values and are presented appended. Expansion tests were performed on typical specimens of natural soils in accordance with the procedures outlined in U.B.C. Standard 18-2. COAST GEOTECHNICAL Mr. & Mrs. Pouliot 17 W.O.266704 Geotechnical Investieation December 30 2004 TEST RESULTS Maximum Density/Optimum Moisture (ASTM•D-1557) Boring No. Depth in Feet Maximum Density, pcf Optimum Moisture, % 3 0-4 125 9.0 Direct Shear - In -situ Samples Boring No. Depth in Feet Cohesion lbs./s . ft.) Angle of Internal Friction (degrees) 2 4 100 31 2 10 200 30 3 5 500 29 Expansion Index (U.B.C. Standard 18-2) Boring No. Depth in Feet Expansion Index Expansion Potential 3 0-4 10 Very Low Soluble Sulfate Analysis Boring No. Depth in Feet Sulfates 3 0-4 66 COAST GEOTECHNICAL SPECIFICATIONS FOR GRADING SITE CLEARING All existing vegetation shall be stripped and hauled from the site. PREPARATION After the foundation for the fill has been cleared, plowed or scarified, it shall be disced or bladed until it is uniform and free from large clods, brought to a proper moisture content and compacted to not less than ninety percent of the maximum dry density in accordance with ASTM:D-1557-00 (5 layers - 25 blows per layer; 10 lb. hammer dropped 18"; 4" diameter mold). MATERL4LS On -site materials may be used for fill, or fill materials shall consist of materials approved by the Soils Engineer and may be obtained from the excavation of banks, borrow pits or any other approved source. The materials used should be free of vegetable matter and other deleterious substances and shall not contain rocks or lumps greater than eight inches in maximum dimension. PLACING, SPREADING AND COMPACTING FILL MATERMLS Where natural slopes exceed five horizontal to one vertical, the exposed bedrock shall be benched prior to placing fill. The selected fill material shall be placed in layers which, when compacted, shall not exceed six inches in thickness. Each layer shall be spread evenly and shall be thoroughly mixed during the spreading to ensure uniformity of material and moisture of each layer. Where moisture of the fill material is below the limits specified by the Soils Engineer, water shall be added until the moisture content is as required to ensure thorough bonding and thorough compaction. Where moisture content of the fill material is above the limits specified by the Soils Engineer, the fill materials shall be aerated by blading or other satisfactory methods until the moisture content is as specified. After each layer has been placed, mixed and spread evenly, it shall be thoroughly compacted to not less than 90 percent of the maximum dry density in accordance with ASTM:D-1557-00 (5 layers - 25 blows per layer; 10 lbs. hammer dropped 18 inches; 4" diameter mold) or other density tests which will attain equivalent results. Compaction shall be by sheepsfoot roller, multi -wheel pneumatic tire roller or other types of acceptable rollers. COAST GEOTECHNICAL SPECIFICATIONS FOR GRADING PAGE 2 Rollers shall be of such design that they will be able to compact the fill to the specified density. Rolling shall be accomplished while the fill material is at the specified moisture content. Rolling of each layer shall be continuous over the entire area and the roller shall make sufficient trips to ensure that the desired density has been obtained. The final surface of the lot areas to receive slabs on grade should be rolled to a dense, smooth surface. The outside of all fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction operations shall be continued until the outer nine inches of the slope is at least 90 percent compacted. Compacting of the slopes may be progressively in increments of three feet to five feet of fill height as the fill is brought to grade, or after the fill is brought to its total height. Field density tests shall be made by the Soils Engineer of the compaction of each layer of fill. Density tests shall be made at intervals not to exceed two feet of fill height provided all layers are tested. Where the sheepsfoot rollers are used, the soil may be disturbed to a depth of several inches and density readings shall be taken in the compacted material below the disturbed surface. When these readings indicate that the density of any layer of fill or portion there is below the required 90 percent density, the particular layer or portion shall be reworked until the required density has been obtained. The grading specifications should be a part of the project specifications. The Soil Engineer shall review the grading plans prior to grading. INSPECTION The Soil Engineer shall provide continuous supervision of the site clearing and grading operation so that he can verify the grading was done in accordance with the accepted plans and specifications. SEASONAL LIMITATIONS No fill material shall be placed, spread or rolled during unfavorable weather conditions. When work is interrupted by heavy rains, fill operations shall not be resumed until the field tests by the Soils Engineer indicate the moisture content and density of the fill are as previously specified. EXPANSIVE SOIL CONDITIONS Whenever expansive soil conditions are encountered, the moisture content of the fill or recompacted soil shall be as recommended in the expansive soil recommendations included herewith. SITE VICINITY PLAN uNITEn STATES COAST GEOTECHNICAL DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY W.O. 266704 Plate 1 REGIONAL GEOLOGY R GEOLOGY OF THE LACUNA BEACH QUADRANGLE ORANGE COUNTY CALIFORNIA �\ � �Xs �tm WILLIAM J. EDGINGTO� 5 6Y '% N AND SIANG S. TAN, Ci Et Nonmarme deposits on marine lerr ace dep0" s (subscripts indicate relative level with I the lowest).. P Olm Marine terrace depost is (wdhouI non marine cover)\ BEDROCK UNITS )( Tc Capistrono Formolton Tm Monterey Farmation; Tm-ss sandstone 0 Qtn3 m V1� lt4l llp �wr ty SITEu I, Qtn, I., M11.4 Wldlow�t7xgl COAST GEOTECHNICAL W.O. 266704 Plate 2 SITE GEOLOGY MAP r 14 r#1 CORTIAND DRNE note: This plate is not a survey, it is schematic in nature and is intended for illustrations of geotechnical data only. The indicated scale is approximate and is presented for roughlmeasurement only LEGEND {�} ; Exploratory Location �' Geologic Cross Section �I �t Surficial Slump Creeping Slope Af- Artificial Fill Soil Qtn- Terrace Deposits Tm — Bedrock, Monterey Formation Scale 1'=20, COAST GEOTECHNICAL W.O. 226704 Plate 3 GEOLOGIC CROSS SECTION V A u d E2 co c) C .o a) W a e IL I% 'a .o K COAST GEOTECHNICAL W.O. 266704, Plate 4 "t�' w� _ ,,_ ` ',; _ 1►-�, -, SUMMARY OF BORING NO. 1 Date: 12/10/2004 Elevation: E.G. T d S N .� > C N U o a y E L Description o ; y E. U u B Fill: SAND -- silty, coarse -grained, wet Yellow Brown Medium Dense Terrace Deposit: SAND, Silty, fine to medium Yellow Light Dense N/R 18.5 grained, wet, Seepage at 2 feet Gray 5 N/R 9.9 SAND — silty, fine to medium -grained, moist 110 8.6 BEDROCK: SILTSTONE — sandy, clayey, moist Orange Yellow Hard Brown 94 16.4 End of Boring at 7.5 feet, Refusal Seepage Water @ 2 feet Sands are Subject to Caving to— Geologic and Geotechnical Engineering Investigation Work Order 266704 4824 Cortland Drive Corona del Mar, California Plate No. 7 COAST GEOTECHNICAL SUMMARY OF BORING NO. 2 Date: 12/10/2004 Elevation: Mid -Slope N d C + U C C a 7 o G. Description °o U c v U B 0 Slump: SAND — silty, damp Yellow Loose Brown Artificial Fill : SAND —silty, damp to moist Medium Dense to Dense 99 8.2 5 107 13.7 Terrace Deposit: SAND -- silty, slightly clayey, Red Brown Dense ilo- with light gray stringers SAND — clayey, medium to coarse -grained, Red Brown moist to Orange Brown 105 10.2 SAND -- silty, moist Dark Gray Dense Black BEDROCK: SILTSTONE -- clayey, moist Orange Brown Hard 15 End of Boring at 15 feet No Groundwater Sands are Subject to Caving Geologic and Geotechnical Engineering Investigation Work Order 266704 4824 Cortland Drive Corona del Mar, California Plate No. 8 COAST GEOTECHNICAL SUMMARY OF BORING NO. 3 Date: 12/10/2004 Elevation: E.G. T _ N ^ y N U C m V z E r Description o y ❑a v o❑ in V o 0 o v u B Fill: SAND — silty, medium -grained, moist Yellow Brown Dense Terrace Deposit: SAND — silty, clayey, fine to Red Brown to Dense medium -grained, moist Orange Brown 102 14.6 BEDROCK: SILTSTONE -- diatomaceous Yellow -Buff Hard 5 84 21.9 End of Boring at 5.5 feet, Refusal No Groundwater No Caving 10 Geologic and Geotechnical Engineering Investigation Work Order 266704 4824 Cortland Drive Corona del Mar, California Plate No. 9 COAST GEOTECHNICAL R 4 3 0 L 0 SHEAR TEST RESULT Boring No.2 @ 4 Feet 1 2 3 4 Confining Pressure (kips/sq. ft.) Existing Fill samples were tested at saturated conditions. The sample had a dry density of 99 lbs./cu.ft, and a moisture content of 25.5 % Cohesion = 100 psf Friction Angle = 31 degrees Based on 80% peak strength or ultimate strength, whichever is lower Geologic and Geotechnical Engineering Investigation Work Order 226704 4824 Cortland Drive Newport Beach, California Plate No. 10 COAST GEOTECHNICAL SHEAR TEST RESULT Boring No.2 @ 10 Feet 4 3 0' N 1 h a 'ae 2 N N 0 0 1 2 3 4 Confining Pressure (kips/sq. ft.) Terrace Deposit samples were tested at saturated conditions. The sample had a dry density of 105 lbs./cuff and a moisture content of 22 %. Cohesion = 200 psf Friction Angle = 30 degrees Based on 80% peak strength or ultimate strength, whichever is lower Geologic and Geotechnical Engineering Investigation Work Order 226704 4824 Cortland Drive Newport Beach, California Plate No. 11 COAST GEOTECHNICAL SHEAR TEST RESULT Boring No.3 @ 5 Feet 4 3 tC c N a ]e 2 N N w U) 1 0 0 1 2 3 4 Confining Pressure (kips/sq. ft.) Bedrock samples were tested at saturated conditions. The sample had a dry density of 84 lbs./cu.ft. and a moisture content of 36.5 %. Cohesion = 500 psf Friction Angle = 29 degrees Based on 80% peak strength or ultimate strength, whichever is lower Geologic and Geotechnical Engineering Investigation Work Order 226704 4824 Cortland Drive Newport Beach, California Plate No. 12 COAST GEOTECHNICAL SURFICIAL SLOPE STABILITY ANALYSIS ( For Artificial Fill (Sand) Slope) Reference: " Soil Slips, Debris Flows, and Rainstorms in the Santa Monica Mountains and Vicinity, Southern California", U. S. Geological Survey Professional Paper 851, dated 1975. CALCULATIONS: F.S.= C+(y-yw)Z(COS#)2tan tp (y ) ( Z ) ( sin � ) ( cosp ) Where: F.S. is the Factor of Safety. C ( cohesion) = 100 psf y ( saturated density of soil) = 120 pcf yW ( density of water) = 62.4 pcf Z ( depth of slide) = 4 feet P ( slope angle ) = 27 degrees q5 ( angle of friction) = 31 degrees 100+(120-62.4)(4)(0.891)(0.891 )(0.601 ). F.S. = ( 120 ) ( 4 ) ( 0.454 ) ( 0.891 ) 1.08 This factor of safety is below the normally accepted minimum for stable slopes. Work Order 226704 Plate No. 13 SLOPE STABILITY ANALYSIS (For Terrace Deposit (Sand) Slope) Reference: "Design Manual; Soil Mechanics, Foundations, and Earth Structures", NAVFAC DM-9, March 1971, Page 7-7-8. PROPERTIES: C ( cohesion) = 200 psf y ( saturated density of soil) = 120 pcf H ( slope height) = 18 feet B ( slope angle) = 30 degrees ¢ ( angle of friction) = 30 degrees COMPUTATIONS: y H tan ¢ ACO = _ C From Reference Figure 7-4 Ncf = 21.0 120*18*tan 30 200 Ncf C 21 * 200 F. S. _ _ = 1.94 y H 120 * 18 = 6.24 This factor of safety is in excess of the normally accepted minimum for stable slopes. , Work Order 226704 Plate No. 14 .'Amm�►I��%. mopI■//■ ONE ■■■ I■I� P ■■■■■/�/1ii�s N■■I PP Joe WE AM ri AX p E .•-� ■ i 1.0 — 0 2 Ya-Ya H. Q � v� 1.0 ti 2 VALUES FOR MIl gas DEFINITIOKS X,-x,H -x H i *g I o XO £, - 06 �C.e... T Yo'yoH b I N I I - CRITICAL TOE CIRCLE FACTOR OF SAFETY, F3 = Nc{ C H PARAMETER rh1 ton - c '— IF ACm>O CRITICAL SLIP CIRCLE INTERSECTS TOE, GROUND WATER LEVEL AND TOP OF HARD STRATUM ARE BELOW CRITICAL SLIP CIRCLE. FIGURE 7.4 Stability Analysis for Slopes With 0 and c. 7-7-8 EN FRICTION PILE DESIGN Allowable Capacity (Kips) 10.0 20.0 30.0 40.0 50.0 Minimum Embedment 5 Feet ! 5 S i t LL U- v y t i v O 10 1 N 1 Co I O •c 15 C E N I N E E 20 w i ! F ! ! 25 s Y i t 30 ....... ............. .............. ............ ...................... ................................... ......... ........................ ................. ! ...................! Design values given are for 12 inch diameter, cast -in -place friction piles. For piles of different sizes, the allowable capacity will be directly proportional to .the comparative pile diameter. Uplift capacity will be one half the downward value given. Geotechnical Investigation Project No. 226704 4824 Cortland Drive Newport Beach, California Plate 15 COAST GEOTECHNICAL SHORING DESIGN PRESSURE DIAGRAM For shoring design, either of the following may be used: A. Restrained shoring by bracing or anchors: 2�M B. Cantilever of free standing shoring: rth pressure /square foot n pounds/foot of length Note: These values do not include pressures resulting from any adjacent structures. Further support due to these structures may be necessary. For the design of underpinning, the value given in this report may be used. Geotechnical Engineering Investigation Work Order 266704 4824 Cortland Drive Newport Beach, California Plate No. 16 COAST GEOTECHNICAL 12/14/2004 11:53 7145491847 ANAHEIM TEST LAB ANAHEIM TEST LABORATORY 3008 S. ORANGE AVENUE SANTA ANA, CALIFORNIA 92707 PHONE (7I4) 549-7267 TO: COAST GEOTECHNICAL: 14747 ARTESIA BLVD, D-1 LA MIRADAt CA. 90638 ATTN: DAN HERO PROJECT: #266704 POULIOT H-3 @ 0-4' waM •2 ANALYTICAL REPORT SOLUBLE SULFATES per CA. 417 66 ppm DATE: 12/14/04 P.O. No, VERBAL Shipper No. Lab, No. A-6264 SpeCIllGotlOn: Material: SOIL Y I COAST GEOTECHNYCAL Maintenance of Hillside Home Sites Recommendations During the wet weather season, homeowners become concerned about the stability of their building sites. In general, modem design and construction practice minimizes the probability of serious slope failure. The grading codes of the local jurisdiction (cities and counties) in California concerning filled land, excavation, terracing and slope construction are among the most stringent in the country and if followed, are adequate to meet most natural occurrences. Therefore, the concern of the homeowner should be directed toward maintaining slopes, drainage provisions and facilities so that they will perform as designed. The following discussion, general recommendations and simple precautions are presented herein to help the homeowner maintain his hillside building site. The general public often regards the natural terrain as stable - "terra firma". This, of course, is an erroneous concept. Nature is always at work altering the landscape. Hills and mountains are worn down by mass wasting (erosion, sliding, creeping) and the valleys and lowlands collect these products. Thus the natural process is toward leveling the terrain. Periodically (over tens of millions of years) major land movements build mountains and erosion tends to level the terrain. In some areas these processes are very slow and in others they are more rapid. Development of hillsides for residential use is carried out, in as far as possible, to enhance the natural stability of the site and to minimize the probability of instability resulting from the grading necessary to provide home sites, streets, and yards. This has been done by the developers and designers on the basis of geologic and soil mechanics investigations. In order to reduce the risk of slope failures, the slope and drainage provisions and facilities must be maintained by the homeowner. Homeowners are accustomed to maintaining their homes. They expect to paint their houses periodically, replace wiring, clean out clogged plumbing, repair roofs, etc. Maintenance of the home site, particularly on hillsides should be considered on an even more serious basis. In most cases lot and site maintenance can be taken care of along with landscaping and can be carried out less expensively to the homeowner than repair after neglect. Most hillside lot problems are associated with water. Uncontrolled water from poor drainage, over irrigation, a broken pipe, cesspool or ivet weather causes most damage. Wet weather is the largest cause of slope problems, particularly in California where rain is intermittent, but may be torrential. Therefore, drainage and erosion control are the most important aspects of home site stability. These provisions must not be altered without competent professional advice and maintenance must be carried out to assure their continued operations. We offer these procedures as a checklist to homeowners: 1. Check roof drains, gutters and down spouts to be sure they are clear. Depending on your location, if you do not have roof gutters and down spouts, you may wish to install them. Without gutters or other adequate drainage, water falls from the roof eaves and collects against foundation and basement walls, which can be undesirable. COAST GEOTECHNICAL 2. Clear surface and terrace drainage ditches and check them frequently during the rainy season, with a shovel, if necessary. Ask your neighbors to do likewise. 3. Be sure that all drainage ditches and sub -drains have outlet drains that are open. This should be tested during dry weather. Usually this can be done simply with a hose. If blockage is evident, you may have to clear the drain mechanically. 4. Check all drains at the top of slopes to be sure that they are clear and that water will not overflow the slope itself, causing erosion. 5. Keep subsurface drain openings (weep -holes) clear of debris and other material, which could block them in a storm. 6. Check for loose fill above and below your property if you live on a slope or terrace. 7. Watch hoses and sprinklers. During the rainy season, little, if any, irrigation is required. Over -saturation of the ground is not only unnecessary and expensive, but can cause subsurface damage. 8. Watch for water backup of drains inside the house and toilets during a rainy season since this may indicate drain or sewage blockage. 9. Exercise ordinary precaution. Your house and building site was constructed to meet certain standards, which should protect against any natural occurrence, if you do your part in maintaining them. 10. Care and maintenance of hillside homes includes being sure that terrace drains and brow ditches on slopes or at the top of cuts, or fill slopes are not blocked. They are designed to carry away runoff to a place where it can be safely distributed. Generally, a little shovel work will remove any accumulation of dirt and other debris, which may clog the drain. If several homes are located on the same terrace, it is a good idea to check with your neighbors. Water backed up on their properties may eventually reach yours. Water backed up in surface drains will tend to overflow and seep into the terraces, creating less stable slopes. 11. Water should not be permitted to collect or pond on your home site. Ponded water will tend to either seep into the ground loosening fill or natural ground, or will overflow onto the slope and cause erosion. Once erosion is started, it is difficult to control and severe damage may result rather quickly. 12. Roof drains and gutters or down spouts should not be connected to subsurface drains. Rather, arrange them so that water either flows off your property in a specially designed pipe or it flows out onto a paved driveway or the street. The water then may be dissipated over a wide surface or preferably be carried away in a paved gutter or storm drain. Subdrains are constructed to take care of ordinary subsurface water and cannot handle the overload from roofs during a heavy rain. 13. Water should not be allowed to spill over slopes, even where this may seem to be a good way to prevent ponding. This trends to cause erosion and, in the case of fill slopes, can cut away carefully designed and constructed sites. 2 COAST GEOTECHNICAL 14. Loose soil or debris should not be left on or tossed over slopes. Loose soil soaks up water more rapidly than compacted fill. In addition, it is not compacted to the same strength as the slope itself and will tend to slide when laden with water and may even affect the soil beneath it. The sliding may clog terrace drains below or may cause additional damage in weakening the slope. If you live below a slope, try to be sure that loose fill is not dumped above your property. 15. Water should not be discharged into subsurface blanket drains close to slopes. French drains are sometimes used to get rid of excess water when other ways of disposing of water are not readily available. Overloading these drains saturates the ground and, if located close to slopes, may cause slope failure. 16. Surface water should not discharged into septic tanks or leaching fields. Not only are septic tanks constructed for a different purpose, but they will tend, because of their construction, to accumulate additional water naturally from the ground during a heavy rain. Overloading them artificially during the rainy season is bad for the same reason as subsurface subdrains, and is doubly dangerous since their overflow can pose a serious health hazard. In many areas the use of septic tanks should be discontinues as soon as sewers can be made available. 17. Slopes should not be over -irrigated. In some areas ice plant and other heavy ground cover can cause surface sloughing when saturated due to the increase in weight and weakening of the near surface soil. Planted slopes should be located, where possible, in areas where they will be adequately irrigated by rainfall. A landscape architect familiar with hillside work should design slope planting. 18. Water should not be allowed to gather against foundation, retaining walls and basement walls. These walls are built to withstand the ordinary moisture in the ground and are, where necessary, accompanied by subdrains to carry of the excess moisture. If water is permitted to pond against them, it may seep through the wall causing dampness and leakage inside the basement. It also may cause the soil adjacent to the foundation to swell resulting in structural damage to walls and footings. 19. New fill placed behind walls or in trenches should not be compacted by flooding with water. Not only is flooding the least efficient way of compacting fine grained soil, but could damage the wall foundation. 20. Hoses and sprinklers should not be left running on or near a slope, particularly during the rainy season. This will enhance ground saturation which may cause damage. 21. Ditches which have been graded around your house or the lot pad should not be blocked. These shallow ditches have been put there for the purpose of quickly removing water toward the driveway, street or other positive outlet. By all means, do not let water become ponded above slopes by blocked ditches.