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HomeMy WebLinkAboutSUP 06-11; Robertson Ranch Planning Area 12 and 13; Geotechnical Report; 2008-06-05Geotechnical • Geologic • Coastal • Environmental REPORT OF MASS GRADING PLANNING AREA 12 (13.44 ACRES) AND PLANNING AREA 13 (6.92 ACRES) ROBERTSON RANCH WEST, CARLSBAD SAN DIEGO COUNTY, CALIFORNIA 92010 CITY OF CARLSBAD PLANNING DEPARTMENT APPLICATION NO. SUP 06-12/HDP 06-04 FOR ROBERTSON FAMILY TRUST C/0 SEABOURNE DEVELOPMENT CO. P.O. BOX 4659 CARLSBAD, CALIFORNIA 92018-4659 W.O. 5247-B1-SC JUNE 5, 2008 Geotechnical • Geologic • Coastal • Environmental 5741 Palmer Way • Carlsbad, California 92010 • (760)438-3155 • FAX (760) 931-0915 June 5, 2008 W.O. 5247-B1-SC Robertson Family Trust c/o SeaBourne Development Co. P.O. Box 4659 Carlsbad, California 92018-4659 Attention: Mr. Ken Cablay Subject: Report of Mass Grading, Planning Area 12 (13.44 Acres), and Planning Area 13 (6.92 Acres), Robertson Ranch West, Carlsbad, San Diego County, California 92010, City of Carlsbad Planning Department Application No. SUP 06-12/HDP 06-04 Dear Mr. Cablay: This report presents a summary of the geotechnical testing and observation services provided by GeoSoils, Inc. (GSI) during the mass grading phase of development for Planning Areas (PA) -12 and PA-13. It is GSI's understanding that the purpose of grading was to prepare a relatively level "super pad" for the future construction of a park site and associated infrastructure. Earthwork commenced on, or about, February 7,2008, and was generally completed on May 9,2008. The mass grading consisted of sheet grading PA-12 and PA-13 to the approved grading plan by O'Day Consulting (OC, 2006). The approximate elevations of field density test locations indicated in Table 1 are based on the approved grading plan (OC, 2006). Currently, it is our understanding that future development plans of PA-12 and PA-13 are anticipated to be a park site and associated infrastructure. Therefore, supplemental geotechnical recommendations should be provided when construction and precise grading plans have been developed. Survey of line and grade was performed by others, and not performed by GSI. EXISTING ADJOINING FILL For context, geotechnical testing and observation services were previously performed by GSI during the previous adjacent mass grading phase of development for Calavera Hills II. Earthwork commenced in May 2007, and was generally competed on October 2007. The purpose of that work was to construct a sheet graded pad, building areas for the construction of multi-family structures, and an 84-inch storm drain and associated improvements for Cannon Road. Compacted fills were placed within these areas, as summarized in GSI (2008,2007a, and 2007b). Some of the compacted fill reported herein was placed on those fills. ENGINEERING GEOLOGY The geologic conditions exposed during the process of grading for the current phase of development were regularly observed by a representative from our firm. The geologic conditions encountered generally were as anticipated and presented in the preliminary geotechnical reports (see the Appendix, References). Earth Materials Alluvium (Map Symbol - Qal) Alluvial sediments occur within a distinct depositional environment onsite, termed valley alluvium, deposited within the larger, broad flood plains located along the west and south sides of the project. Where encountered, alluvial sediments consist of sandy clay and clayey/silty sand. Clayey sands are typically loose to medium dense, while sandy clays are stiff. Alluvium ranges from generally damp to wet above the local groundwater table, to saturated just above and below the groundwater table. As a result of the presence of groundwater, alluvial removals were limited in depth. Therefore, as provided for in the approved report (GSI, 2007c), saturated left-in-place alluvial soils (see Plates 1 and 2), will require settlement monitoring and site specific foundation design. Terrace Deposits (Map Symbol - Qt) Mid- to late-Pleistocene terrace deposits encountered onsite consist of sediments which vary from silty sand to sandy/silty clay. They are typically reddish brown to brown and olive brown, slightly moist to moist, and medium dense/stiff. Terrace deposits are generally considered suitable for the support of structures and engineered fill. However, due to the non-uniform and different soil types occurring against each other, creating non-uniformity, overexcavation is recommended if expansive-or settlement-sensitive improvements (i.e., buildings, concrete decks, etc.) are proposed within this area. Geologic Structure Our review and observations during grading indicates that jointing within the terrace deposits generally strikes east-west to N65E. Joints are typically steeply dipping (generally in excess of 40 degrees), and are generally inclined to the west. Bedding is generally dipping in a southerly direction. Beds are typically sub-horizontal to gently dipping (generally less than 15 degrees), and are generally inclined to the southwest. The contact between the alluvium overlying the Pleistocene-age terrace deposits is unconformable in nature, as in much of California, many ancient swales and channels were deeply incised Robertson Family Trust W.O. 5247-81-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 Rle:e:\wp9\5247\5247b1 .ros Page 2 GeoSoils, Inc. during the last major pluvial epoch, this occurring approximately 12,000 to 18,000 years ago (Dietrich and Dorn, 1984; Shlemon and others, 1987). Faulting is discussed below. Faulting A small fault zone was observed to transect the Pleistocene-age terrace deposits during mass grading in one localized area. The fault was field located based on GPS measured coordinates and was geologically mapped, as shown on the accompanying Plate 1 and Plate 2. For context, in this area of southern California faulting is characterized by a series of Quaternary-age fault zones which typically consist of several individual, en echelon faults, that generally strike in a northerly to northwesterly direction. Some of these fault zones (and the individual faults within the zone) are classified as active, while others are not, according to the criteria of the California Geological Survey ([CGS] formerly known as California Division of Mines and Geology). Active fault zones are those which have shown well defined and demonstrable evidence of faulting during the Holocene Epoch (the most recent 11,000 years). The site does not lie within an Alquist-Priolo Earthquake Fault Zone (Bryant and Hart, 2007). The trace of the fault on-site was exposed during grading within the western portion of the super pad. This corresponds to the western side of a ridgeline that was excavated to design grades, and provided the primary embankment material for the project. The only materials that are faulted consist of the Pleistocene Epoch terrace deposits. Based on GSI's geologic observation and mapping, this discrete fault trace is sinuous, generally trends N30 to N50 east, is steeply dipping (dip varying from 45 to 55 degrees), and is generally most often inclined to the west. The fault surface, where observed, is typically composed of a thin clayey to sandy clay sheared surface exhibiting down dip striations. Striations were observed to be generally vertical. The fault was not observed during grading of the northerly adjacent PA-14 (GSI, 2008), but was observed to die out in the bounding cut slope between PA-13 and PA-14. The fault trace could not be traced southernly through the entire PA-12 and dies out approximately 140 feet north of the designed cut/fill daylight transition. Studies of faults provide clues to the formation of dip slip and other types of movement on such faults. Strike slip faults tend to concentrate deformation along a single linear strand, that may extend for tens or hundreds of miles with only minor changes in strike (Weldon, et al., 1996). Weldon, et al. (1996) also points out that active strike slip faulting produces a characteristic assemblage of landforms, including linear valleys, offset or deflected streams, shutter ridges, sag ponds, pressure ridges, benches, scarps, and small horsts and grabens. Strike slip faults also transport non-tectonic landforms laterally (i.e., fluvial terraces, stream channels, and alluvial fans), while the erosional and depositional processes forming them continue. Structures characteristic of a compressional or transpressional faulting regime typically form imbricate thrust systems, fault-bend folds or ramp folds, fault-propagation folds, stacked colluvial wedges, pressure ridges, thrust faults, and folds (with planar limbs and sharp hinge lines characteristic of fault-bend and Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 3 GeoSoils, Inc. propagation anticlines that generally form parallel to strike slip faults [Suppe, 1983 and 1985]). The onsite fault does not exhibit these characteristics. Similarly, features characteristic of extensional or transtensional faulting include normal faults, tilted fault blocks, antithetic faults, and horsts and grabens. These features were not noted onsite, except the onsite fault generally appeared to have characteristics of a normal fault. As pointed out by Chen, et al. (2002), during long periods of quiescence, fault-line scarps will retreat and become irregular; if the recurrence interval is sufficiently short (i.e., typical of active faulting), the fault-line scarp will be well preserved. The primary indicator of paleoearthquakes in an extensional environment (i.e., normal faults), is a fault scarp (McCalpin, 1996). Our investigation did not reveal fault scarps were present onsite. Furthermore, a review of aerial photographs (USDA, 1953) did not indicate a photo-lineament specifically associated with this onsite fault. The fault was not previously mapped during site specific studies nor has it been shown on any published geologic maps of the area. The nearest mapped active fault to the site is the Newport-lnglewood - Rose Canyon fault zone located approximately 6.6 miles west of the site. Based on the northeast trend, this fault is not likely to be tectonically related to the modern tectonic regime, thus, it is likely a relict structure from an ancient transtensional tectonic environment, and is non-seismogenic. Based on the above discussed research, field observations, and lack of typical diagnostic criteria indicative of Holocene movement, GSI reasonably concludes that it is unlikely that active faulting exists onsite. Based on the data, if any movement occurred on the onsite fault, it was pre-Holocene. Thus, this fault does not warrant building setbacks per CGS criteria. Present site use has been planned as park and recreational. Differential expansion/compression characteristics across the fault trace may impact future buildings, or concrete decks, etc. GSI should review the final development and precise grading plans and provide any additional recommendations as deemed prudent, based on proposed use and precise grading plans. These may include overexcavation and/or special foundation design for expansion or settlement. Groundwater Groundwater was encountered during grading at elevations ranging from about 32 to 44 feet Mean Sea Level (MSL) in the valley alluvial material (Map Symbol - Qal). Generally, and based upon the available data, regional groundwater is not expected to be a major factor in the development of the site. However, perched groundwater may occur within the fill or along zones of contrasting permeabilities (i.e., differing fill lifts or along bedding planes and bedrock joints/discontinuities, etc.), due to migration from onsite, offsite, or adjacent drainage areas, and during and/or after periods of above normal or heavy precipitation or irrigation. Thus, perched groundwater conditions may occur in the future, after development, and should be anticipated. These observations reflect site conditions at the completion of grading and do not preclude changes in local groundwater conditions in the future. Should such conditions become apparent within the project in the Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 4 GeoSoils, Inc. future, additional recommendations for mitigation may be provided upon request. This potential would need to be disclosed to all interested/affected parties. EARTHWORK CONSTRUCTION Earthwork operations have been completed in general accordance with the approved report for the site (GSI, 2007),City of Carlsbad grading ordinance, and the guidelines provided in the field by this office. Observations during grading included removals along with general grading procedures and placement of compacted fills by the contractor. Preparation of Existing Ground 1. Prior to grading, the major surficial vegetation was stripped and hauled offsite. 2. Removals, consisting of topsoil/colluvium, alluvium, and near-surface weathered terrace deposits, were performed to the minimum depths and lateral extent, or greater, as recommended in the approved referenced report by GSI (2007c). The approximate removal limits are indicated on Plates 1 and 2. 3. Subsequent to the above removals, the exposed subsoils were scarified to a depth of about 12 inches, moisture conditioned as necessary to at least optimum moisture content, then compacted to a minimum relative compaction of 90 percent of the laboratory standard. 4. Fills placed on sloping surfaces steeper than 5:1 (horizontal to vertical [h:v]), as indicated by pre-existing topography, were keyed and benched into competent terrace deposits. 5. All processing of original ground was observed by a representative of GSI. Fiil Placement Fill, consisting of native soils, was placed in 6-to 8-inch lifts, watered, and mixed to achieve at least optimum moisture conditions. The material was then compacted, using earth moving equipment, to a minimum relative compaction of 90 percent of the laboratory standard. It should be noted that materials greater than 12 inches in diameter were routinely placed below 10 feet from finish grade. However, oversized materials may not be precluded from occurring, and/or excavation difficulties may be encountered at finish grade. Thus, the potential for excavation difficulties and oversized materials should be disclosed to all affected/interested parties. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros ^ _ „„ _ Page 5GeoSoils, Inc. Transitions During mass grading of the site, a designed cut/fill transition, as indicated on the grading plans by OC (2006), was graded without any additional mitigation, such as overexcavation of the cut, since the location of settlement sensitive structures was not known. Once precise grading plans have been formulated, GSI should review such plans in order to provide recommendations for overexcavation, as warranted. Slopes Fill Slopes Graded slopes constructed under the purview of this report should perform satisfactorily with respect to gross and surficial stability under normal conditions of care, maintenance, and rainfall (semi-arid). Fill slopes, constructed under the purview of this report, were provided with a basal bench, or keyway, excavated into suitable earth material in general accordance with the approved GSI recommendations (GSI, 2007c). Cut Slopes A cut slope (west side of Wind Trail Way) was excavated in general accordance with the approved GSI recommendations (GSI, 2007c), and exposed terrace deposits earth material(s). The exposed material within this cut slope was highly fractured, and locally exhibited an out of slope bedding component. Therefore, above normal maintenance and care should be expected on this cut slope. When precise grading plans have been developed, this cut slope should be re-evaluated and supplemental recommendations will be provided, as warranted. Future design may necessitate stabilization of the cut slope, depending on development plans for adjacent PA-14. Temporary Slopes Temporary construction slopes may be constructed at a gradient of 1:1 (h:v), or flatter, in compacted fill and/orterrace deposits (provided adverse conditions [including groudwater] are not present, as evaluated by GSI, prior to workers entering trenches). Utility trenches may be excavated in accordance with guidelines presented in Title 8 of the California Code of Regulations for Excavation, Trenches, and Earthwork, with respect to "Type B" soil (compacted fill and/or native material), provided groundwater is not present. Construction materials and/or stockpiled soil should not be stored within 5 feet from the top of any temporary slope. Temporary/permanent provisions should be made to direct any potential runoff away from the top of temporary slopes. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 6 GeoSoils, Inc. Natural Slopes Natural slopes are not present within PA-12 and PA-13. FIELD TESTING 1. Field density tests were performed using nuclear (densometer) ASTM test methods D 2922 and D 3017 and sand-cone ASTM test method ASTM D1556. The test results taken during grading are presented in the attached Table 1, and the locations of the tests taken during grading are presented on Plates 1 and 2. 2. Field density tests were taken at periodic intervals and random locations to check the compactive effort provided by the contractor. Where test results indicated less than optimum moisture content, or less than 90 percent relative compaction in fills, the contractor was notified and the area was reworked until retesting indicated at least optimum moisture and a minimum relative compaction of 90 percent were attained. Based upon the grading operations observed, the test results presented herein are considered representative of the compacted fill. 3. Visual classification of the soils in the field was the basis for determining which maximum density value to use for a given density test. LABORATORY TESTING Maximum Density Testing The laboratory maximum dry density and optimum moisture content for the major soil types within this construction phase were determined according to test method ASTM D 1557. The following table presents the results: SOIL TYPE A B C D E *,,, < •"'' , DESCRIPTION SANDY CLAY, Reddish Brown CLAYEY SAND, Brown CLAYEY SAND, Brown Gray CLAYEY SAND, Dark Gray SILTY CLAY, Greenish Gray MAXIMUM DENSITY (PCF) - 118.0 128.0 124.0 125.0 102.0 MOISTURE CONTENT , $ ^PERCENT) 13.5 10.0 11.5 11.0 21.5 Robertson Family Trust PA-12 & PA-13, Robertson Ranch West File:e:\wp9\5247\5247b1 .ros ilSj Inc. W.O. 5247-B1-SC June 5, 2008 Page 7 Expansion Index Expansive soil conditions have been evaluated in the general area of the site. Representative samples of the soils exposed at finish grades will need to be recovered for Expansion Index (E.I.) testing at the conclusion of precise grading. Based on the test results obtained, the expansive potentials of the soils within the subject lots are anticipated to be classified as high to very high (i.e., high to very high expansive potentials 90 to >130). To reiterate, additional expansion testing will need to be conducted at the conclusion of precise grading. Sulfate/Corrosion Testing GSI previously conducted sampling of onsite materials for soil corrosivity on the subject project (GSI, 2007c). Laboratory test results were completed by Schiff & Associates (consulting corrosion engineers). The testing included evaluation of pH, soluble sulfates, and saturated resistivity. Representative samples of the soils exposed at finish grades will need to be recovered for sulfate/corrosion testing at the conclusion of precise grading. Test results indicate that the soil presents a negligible sulfate exposure to concrete, in accordance with Table 19-A-4 of the Uniform Building Code/California Building Code ([UBC/CBC], International Conference of Building Officials [ICBO], 1997 and 2001; California Building Standards Commission [CBSC], 2007); and further results indicate the soils are severely corrosive to ferrous metals, etc., based on saturated resistivity. Site soils are considered to be moderately alkaline with regards to acidity/alkalinity. A corrosion specialist should be consulted forthe appropriate mitigation recommendations, as needed. Once again, additional corrosion testing will need to be conducted at the conclusion of precise grading. PRELIMINARY CONCLUSIONS AND RECOMMENDATIONS General Preliminary conclusions and recommendation are provided in our referenced report (GSI, 2007c). However, for convince, the previous preliminary conclusions and recommendation are reproduced below and modified as appropriate. Currently, it is our understanding that future development plans of PA-12 and PA-13 is anticipated to be a park site and associated infrastructure. Therefore, supplemental geotechnical recommendations should be provided when construction plans have been formulated. As-Built Conditions As-built soil conditions to be considered in foundation design and construction are as follows: Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\524A5247b1 .ros Page 8 GeoSoils, Inc. GSI's review, field work, and laboratory testing indicates that onsite soils have a high to very high expansion potential (E.I. greater than 90), and a plasticity index (P.I.) greater than 42. • As-built fill thicknesses range from approximately 181/a to 30 feet for areas with left in-place saturated alluvium, and approximately 0 to 241/2 feet thick in the terrace deposits area. • When precise grading plans have been formulated, the cut slope (west side of Wind Trail Way) should be evaluated and supplemental recommendations will be provided, as warranted. Future design may necessitate cut slope stabilization, depending on development plans for adjacent PA-14. • A small fault zone was observed to transverse the subject site during mass grading (See Plates 1 and 2). This fault is pre-Holocene in nature, based on CGS guidelines. Accordingly, recommendations for mitigation of faulting (i.e., structural setbacks), are not warranted. The presence of this pre-Holocene fault in the cut pad, where different soil types may be juxtaposed against each other, creating non-uniformity, will necessitate the overexcavation of the affected area where expansive- or settlement-sensitive improvements (i.e., concrete decks, buildings, etc.) overlie this feature. This would also help mitigate the potential for perched water conditions on cut pad areas, as well as provide a uniform fill mat for mitigation of any minor sympathetic movement on the pre-Holocene fault, in the event that a nearby earthquake of sufficient magnitude should occur. • A design cut/fill transition occurs between the artificial fill compacted under the purview of this report and the terrace deposits (see Plates 1 and 2). In order to provide for the uniform support of structures, on a preliminary basis, a minimum 3-foot thick fill blanket is recommended for building pads containing plan transitions. Any cut portion of the pad for the structure should be over excavated a minimum 3 feet below finish pad grade. Areas with fills less than 3 feet should be over excavated in order to provide the minimum fill thickness. Maximum to minimum fill thickness within a given building footprint should not exceed ratio of 3:1. As such, deeper over excavation will be necessary for fill areas with maximum fills in excess of approximately 9 feet. Overexcavation is also recommended for cut pads exposing claystones and/or heterogenous material types (i.e., sand/clay). Recommended overexcavation depths should be determined based on final development and precise grading plans. Preliminary Foundation Design Our review, field work, and laboratory testing within the general area indicates that onsite soils may have a high to very high expansion potential. The preliminary recommendations for foundation design and construction are presented in GSI's previous report (GSI, 2007c) Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 9 GeoSoils, Inc. are reproduced below. Final foundation recommendations should be provided at the conclusion of precise grading, and based on laboratory testing of fill materials exposed at finish grade. Bearing Value 1. The foundation systems should be designed and constructed in accordance with guidelines presented in the latest approved edition of the UBC/CBC (ICBO, 1997 and 2001 ;CBSC, 2007). 2. An allowable bearing value of 2,000 pounds per square foot (psf) may be used for the design of continuous footings at least 12 inches wide and 12 inches deep, and column footings at least 24 inches square and 24 inches deep, connected by a grade beam in at least one direction. This value may be increased by 20 percent for each additional 12 inches in depth to a maximum of 3,000 psf. No increase in bearing value is recommended for increased footing width. The allowable bearing pressure may be increased by one-third underthe effects of temporary loading, such as seismic or wind loads. Lateral Pressure 1. For lateral sliding resistance, a 0.25 coefficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load. 2. Passive earth pressure may be computed as an equivalent fluid having a density of 225 pounds per cubic foot (pcf) with a maximum earth pressure of 2,250 psf. 3. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third. Construction The following preliminary foundation construction recommendations are presented as a minimum criteria from a soils engineering standpoint. The onsite soils expansion potentials generally range from high (E.I. 91 to 130) to very high (E.I. >130) range. Conventional foundation systems are not recommended for high to very highly expansive soil conditions or where alluvial soil is left in-place (see Plates 1 and 2). Post-tension slab or mat foundations may be used for all soil conditions. Recommendations by the project's design-structural engineer or architect, which may exceed the soils engineer's recommendations, should take precedence over the following minimum requirements. Final foundation design will be provided based on the expansion potential of the near-surface soils encountered during precise grading, as well as differential settlement potential. Preliminary foundation recommendations are presented below. Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247t>1 .ros Page 10GeoSotlSj Inc. Mat Foundation Design/Construction In order to mitigate expansive soil conditions, the structure may be supported by a mat slab foundation. The structural mat foundation should have a double mat of steel (minimum No. 4 reinforcing bars located at 12 inches on center each way [top and bottom]), and a minimum thickness of 12 inches. A thickened edge (24 inches below the lowest adjacent grade) should be provided along the perimeter and across a large or wide entrance. Mats may be designed by Section 1815 (Div. Ill) of the UBC/CBC (ICBO, 1997 and 2001; CBSC, 2007) methods using an effective P.I. of 45. Mat slabs may be designed for a modulus of subgrade reaction (Ks) of 70 pounds per cubic inch (pci) when placed on compacted expansive soils (E.I. up to 130). The following section of this report provides supplemental recommendations for under-slab soil moisture transmission mitigation. The slab subgrade moisture content should be at least 120 percent of the soil's optimum moisture content to a depth of 24 inches below grade, requiring presaturation, and subsequent proof-testing. Subgrade Preparation Clay subgrade materials should be compacted to a minimum of 87 to 90 percent of the maximum laboratory dry density, in view of their expansive potential. Prior to placement of concrete, the subgrade soils should be presaturated to 24 to 36 inches below grade to at least 120 percent of the soils optimum moisture content. This should be evaluated by our field representative prior to vapor retarder placement, and prior to and within 72 hours of the concrete pour. Alternative methods, including sealing the subgrade surface with select sand/base and periodic moisture conditioning, may also be considered, as long as the minimum recommended soil moisture contents are achieved. Lime treatment of the soil subgrade may also be considered; however, this will require additional geotechnical analysis. POST-TENSIONED SLAB DESIGN Post-tensioned slab foundation systems may be used to support the proposed buildings. Based on the potential differential settlement within areas of the site underlain by alluvium, post-tensioned slab foundations are recommended exclusively. General The information and recommendations presented in this section are not meant to supersede design by a registered structural engineer or civil engineer familiar with post-tensioned slab design or corrosion engineering consultant. Upon request, GSI could provide additional data/consultation regarding soil parameters as related to post-tensioned slab design during grading. The post-tensioned slabs should be designed Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 11 GeoSoils, Inc. in accordance with the Post-Tensioning Institute (PTI) Method. Alternatives to the PTI method may be used if equivalent systems can be proposed which accommodate the angular distortions, expansion potential and settlement noted for this site. Post-tensioned slabs should have sufficient stiffness to resist excessive bending due to non-uniform swell and shrinkage of subgrade soils. The differential movement can occur at the corner, edge, or center of slab. The potential for differential uplift can be evaluated using the 1997 UBC Section 1816, based on design specifications of the PTI. The following table presents suggested minimum coefficients to be used in the PTI design method. Thornthwaite Moisture Index Correction Factor for Irrigation Depth to Constant Soil Suction Constant Soil Suction Jpf) -20 inches/year 20 inches/year 7 feet 3.6 The coefficients are considered minimums and may not be adequate to represent worst case conditions such as adverse drainage and/or improper landscaping and maintenance. The above parameters are applicable provided positive drainage is maintained away from structures, for a distance of at least 5 feet. Therefore, it is important that information regarding drainage, site maintenance, settlements, and effects of expansive soils be passed on to future owners and/or interested parties. Based on the above parameters, design values were obtained from figures or tables of the 1997 UBC Section 1816 and presented in Table 1. These values may not be appropriate to account for possible differential settlement of the slab due to other factors (i.e., fill settlement). If a stiffer slab is desired, higher values of ym may be warranted. However the slab thickness should be at least 6-inches thick. Robertson Family Trust PA-12 & PA-13, Robertson Ranch West File:e:\wp9\524A5247b1 .ros W.O. 5247-B1-SC June 5, 2008 Page 12 GeoSoilSj Inc. POSTrTENSION FOUNDATIONS a EXPANSION POTENTIAL' ,>*->• -> em center lift em edge lift ym center lift ym edge lift Bearing Value01 Lateral Pressure Subgrade Modulus (k) Perimeter Footing Embedment'2' HIGHLY EXPANSIVE > (EJ. ==91-1301 5.5 feet 4.5 feet 3.5 inches 1 .2 inches 1 ,000 psf 225 psf 70 pci/inch 24 inches VERY HIGHLY EXPANSIVE ^ * (E.L>130) 6.0 feet 4.5 feet 4.5 inches 1 .6 inch 1,000 psf 225 psf 50 pci/inch 24 inches (1) Internal bearing values within the perimeter of the post-tension slab may be increased to 2,000 psf for a minimum embedment of 12 inches, then by 20 percent for each additional foot of embedment to a maximum of 3,000 psf. (2) As measured below the lowest adjacent compacted subgrade surface. Note: The use of open bottomed raised planters adjacent to foundations will require more onerous design parameters. Subgrade Preparation The subgrade material should be compacted to a minimum 87 to 90 percent of the maximum laboratory dry density, in view of their expansive potential. Prior to placement of concrete, the subgrade soils should be moisture conditioned in accordance with the following discussion. Perimeter Footings and Pre-Wetting From a soil expansion/shrinkage standpoint, a fairly common contributing factorto distress of structures using post-tensioned slabs is a significant fluctuation in the moisture content of soils underlying the perimeter of the slab, compared to the center, causing a "dishing" or "arching" of the slabs. To mitigate this possible phenomenon, a combination of soil pre-wetting and construction of a perimeter cut-off wall grade beam should be employed. Deepened footings/edges around the slab perimeter must be used to minimize surface moisture migration beneath the slab. Embedment depths are presented in the above table for various soil expansion conditions. The bottom of the deepened footing/edge should be designed to resist tension, using cable or reinforcement per the structural engineer. Slab subgrade should possess above optimum moisture content of at least 4 to 5 percent for highly to very highly expansive soils to a depth of 24 inches. Pre-wetting of the slab subgrade soil prior to placement of steel and concrete will likely be recommended and Robertson Family Trust PA-12 & PA-13, Robertson Ranch West File:e:\wp9\5247\5247b1 .ros GeoSoils, Inc. W.O. 5247-B1-SC June 5, 2008 Page 13 necessary, in order to achieve optimum moisture conditions. Soil moisture contents should be evaluated at least 72 hours prior to pouring concrete. If pre-wetting of the slab subgrade is completed prior to footing excavation, the pad area may require period wetting in order to keep to soil from drying out. UNDERSLAB TREATMENT/SOIL MOISTURE CONSIDERATIONS GSI has evaluated the potential for vapor or water transmission through slabs, in light of typical floor coverings and improvements. Please note that slab moisture emission rates, range from about 2 to 27 lbs/24 hours/1,000 square feet from atypical slab (Kanare, 2005), whilefloor covering manufacturers generally recommend about 3 lbs/24 hours as an upper limit. Thus, the client will need to evaluate the following in light of a cost v. benefit analysis (owner complaints and repairs/replacement), along with disclosure to owners. Considering the E.I. test results, anticipated typical water vapor transmission rates, floor coverings and improvements (to be chosen by the client) that can tolerate those rates without distress, the following alternatives are provided: 1. Concrete slab underlayment should consist of a 10- to 15-mil vapor retarder, or equivalent, with all laps sealed per the UBC/CBC (ICBO, 1997 and 2001; CBSC, 2007) and the manufacturer's recommendation. The vapor retarder should comply with the ASTM E 1745 - Class A or Class B criteria, and be installed in accordance with ACI 302.1R-04. The 10- to 15-mil vapor retarder (ASTM E 1745 - Class A or Class B) shall be installed per the recommendations of the manufacturer, including all penetrations (i.e., pipe, ducting, rebar, etc.). 2. Slab underlayment should consist of 2 inches of washed sand placed above a vapor retarder consisting of 10- to 15-mil polyvinyl chloride, or equivalent, with all laps sealed per UBC (ICBO, 1997). The vapor retarder shall be underlain by 4 inches of pea gravel (Va to % subangular to angular clean crushed rock, 0 to 5 percent fines) placed directly on the slab subgrade, and should be sealed to provide a continuous water-resistant retarder under the entire slab, as discussed above. All slabs should be additionally sealed with suitable slab sealant. 3. Concrete should have a maximum water/cement ratio of 0.50. This does not supercede Table 19-A-4 of the UBC/CBC (ICBO, 1997 and 2001; CBSC, 2007) for corrosion or other corrosive requirements. Additional concrete mix design recommendations should be provided by the structural consultant and/or waterproofing specialist. Concrete finishing and workablity should be addressed by the structural consultant and a waterproofing specialist. 4. Where slab water/cement ratios are as indicated above, and/or admixtures used, the structural consultant should also make changes to the concrete in the grade beams Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\524A5247t>1 .ros Page 14 GeoSoils, Inc. and footings in kind, so that the concrete used in the foundation and slabs are designed and/or treated for more uniform moisture protection. 5. Owner(s) should be specifically advised which areas are suitable for tile flooring, wood flooring, or other types of water/vapor-sensitive flooring or equipment, and which are not suitable. In all planned floor areas, flooring shall be installed per the manufactures recommendations. 6. Additional recommendations regarding water or vapor transmission should be provided by the architect/structural engineer/slab or foundation designer and should be consistent with the specified floor coverings indicated by the architect. Regardless of the mitigation, some limited moisture/moisture vapor transmission through the slab should be anticipated. Construction crews may require special training for installation of certain product(s), as well as concrete finishing techniques. The use of specialized product(s) should be approved by the slab designer and water-proofing consultant. Atechnical representative of the flooring contractor should review the slab and moisture retarder plans and provide comment prior to the construction of the residential foundations or improvements. The vapor retarder contractor should have representatives onsite during the initial installation. SETBACKS All footings should maintain a minimum horizontal setback of H/3 (H = slope height) from the base of the footing to the descending slope face. This setback should not be less than 7 feet, nor need not be greater than 40 feet. This distance is measured from the footing face at the bearing elevation. Footings adjacent to unlined drainage swales should be deepened to a minimum of 6 inches below the invert of the adjacent unlined swale. Footings for structures adjacent to retaining walls should be deepened so as to extend below a 1:1 projection from the heel of the wall. Alternatively, walls may be designed to accommodate structural loads from buildings or appurtenances as described in the retaining wall section of this report. PRELIMINARY SETTLEMENT ANALYSIS GSI has previously estimated the potential magnitudes of total settlement, differential settlement, and angular distortion for the site (GSI, 2007c). The analyses were based on laboratory test results and subsurface data collected from borings completed in preparation of that study. Site specific conditions affecting settlement potential include depositional environment, grain size and lithology of sediments, cementing agents, stress history, moisture history, material shape, density, void ratio, etc. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 15 GeoSoils, Inc. Ground settlement should be anticipated due to primary consolidation and secondary compression of the left-in-place alluvium and compacted fills. The total amount of settlement, and time over which it occurs, is dependent upon various factors, including material type, depth of fill, depth of removals, initial and final moisture content, and in-place density of subsurface materials. Post Grading Settlement of Compacted Fill Compacted fills onsite, are not generally prone to excessive settlement. Based on our previous analysis, total settlements, on the order of 1/2 inch, or less, should be anticipated (GSI, 2007c). Post Grading Settlement of Alluvium Where these materials are left in-place, settlement of the underlying saturated alluvium is anticipated due to the weight of added planned fills. The magnitude of this settlement will vary with the proposed fill heights (i.e., measured from existing grades), and the thickness, texture, and compressibility of the underlying, left-in-place saturated alluvium. Due to the predominantly fine grained texture of the alluvial soils onsite, settlement of the alluvial soil will occur over time. The areas underlain by alluvial soil, the material was removed to saturated conditions (i.e., ±1 foot above regional ground water level) and recompacted. Therefore, result in leaving alluvium in place, previous calculated total settlements on the order of 3 to 8 inches should be anticipated in these areas. Previous calculations were performed for total settlements for fill thicknesses of 15, 20, and 30 feet within alluvial areas. The calculated total settlements are estimated to be on the order of 4, 5.5, and 7.8 inches, respectively. We estimate about one-quarter of these computed settlements have occurred during grading, with the remainder constituting the post grading component of the total settlement. The anticipated post grade differential settlement is expected to be about one-half of the remaining total settlement over a horizontal distance of 40 feet. Waiting periods on the order of at least 18 months should be anticipated, to allow for an adequate amount of settlement to occur prior to construction of settlement-sensitive improvements. Total settlement may be revised, dependant on the actual field data from monitoring of monuments installed in areas were left-in-place alluvium occurred. Monitoring Areas where alluvial soil is left-in-place should be monitored and the settlement values revised based on actual field data. Settlement monuments have be installed and our currently being surveyed monthly by OC. GSI considers these stations (see Plate 1 and Plate 2) representative of the left-in-place saturated alluvial soil onsite. It is GSI's opinion that after 6 to 8 months of monitoring and less than 1A inch has been recorded, the primary consolidation of settlement should have occurred in the left-in-place saturated alluvial soil Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 16 GeoSoils, Inc. onsite. Monitoring should continue if areas are not developed, for additional data recordings. Dynamic Settlements Ground accelerations generated from a seismic event (or by some man-made means) can produce settlements in sands, both above and below the groundwater table. This phenomena is commonly referred to as dynamic settlement and is most prominent in relatively clean sands, but can also occur in other soil materials. The primary factor controlling earthquake induced settlement in saturated sand, is the cyclic stress ratio. In dry sands earthquake, induced settlements are controlled by both cyclic shear strain and volumetric strain control. On site, the alluvial materials are clayey, thus, dynamic settlement is not considered a significant issue. Settlement Due to Structural Loads The settlement of the structures supported on strip and/or spread footings founded on compacted fill will depend on the actual footing dimensions, the thickness and compressibility of compacted fill below the bottom of the footing, and the imposed structural loads. Provided the thickness of compacted fill below the bottom of the footing is at least equal to the width of the footing, and based on a maximum allowable bearing pressure of 3,000 psf, provided in this report, total settlement of less than 1/2 inch should be anticipated. The design of structures are typically controlled by differential settlement, and not the total settlement. In order to evaluate differential settlement, data on the relative position and dimensions of adjacent footings, structural loads on the footing, and the nature and thickness of compressible soils below each footing may be assumed to be on the order of one-half of the total settlement. In areas where structures will be founded on formational or bedrock, and/or compacted fills, and not underlain with saturated alluvium, total settlement is anticipated to be less than 11/2 inches, with a differential settlement on the order of % inch over a horizontal distance of 40 feet, under dead plus live loads Areas underlain by alluvial soils left-in-place should be designed to withstand an overall total settlement, depending on depth of fill, ranging from 4 to 8 inches and a differential settlement of 2 to 4 inches over a horizontal distance of 40 feet, under dead plus live loads. Given additional time for the alluvial soils to consolidate, total and differential settlements will be less. Total settlements on the order of 2 inches, or less, and a differential settlement of approximately 1 inch over a horizontal distance of 40 feet, under dead plus live loads, could be realized once the area has been allowed to consolidate for an additional 8 to 12 months, prior to construction, as further evaluated by settlement monitoring. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\524A5247b1.ros Page 17 j Inc. Due to the predominantly clayey nature of the underlying wet alluvium, the magnitude of seismic settlement will be less than that due to static loading conditions. The seismic differential settlement for design should be minimally about 11/2 inches over a horizontal span of 40 feet. WALL DESIGN PARAMETERS CONSIDERING EXPANSIVE SOILS Conventional Retaining Walls The design parameters provided below assume that either very low expansive soils (typically Class 2 permeable filter material or Class 3 aggregate base) or native onsite materials are used to backfill any retaining walls. The type of backfill (i.e., select or native), should be specified by the wall designer, and clearly shown on the plans. Building walls, below grade, should be water-proofed. The foundation system for the proposed retaining walls should be designed in accordance with the recommendations presented in this and preceding sections of this report, as appropriate. Footings should be embedded a minimum of 18 inches below adjacent grade (excluding landscape layer, 6 inches) and should be 24 inches in width. There should be no increase in bearing for footing width. Recommendations for specialty walls (i.e., crib, earthstone, geogrid, etc.) can be provided upon request, and would be based on site specific conditions. Restrained Walls Any retaining walls that will be restrained prior to placing and compacting backfill material or that have re-entrant or male corners, should be designed for an at-rest equivalent fluid pressure (EFP) of 65 pcf, plus any applicable surcharge loading. For areas of male or re-entrant corners, the restrained wall design should extend a minimum distance of twice the height of the wall (2H) laterally from the corner. Cantilevered Walls The recommendations presented below are for cantilevered retaining walls up to 10 feet high. Design parameters for walls less than 3 feet in height may be superceded by City and/or County standard design. Active earth pressure may be used for retaining wall design, provided the top of the wall is not restrained from minor deflections. An equivalent fluid pressure approach may be used to compute the horizontal pressure against the wall. Appropriate fluid unit weights are given below for specific slope gradients of the retained material. These do not include other superimposed loading conditions due to traffic, structures, seismic events or adverse geologic conditions. When wall configurations are finalized, the appropriate loading conditions for superimposed loads can be provided upon request. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 18 GeoSoilSj Inc. ^ SURFACE SLOPE OF * 4> RETAINED MATERIAL re; j HpRIZONTALVERTlCAL Level* 2to1 EQUIVALENT V FLUID WEIGHT P.C.F. (SELECT PRE-APPROVED BACKFILL)**\ 40 60 EQUIVALENT } FLUID WEIGHT P.C.FI I °t (NATIVE PRE-APPROVED^ >« ^ ..*. f BACKFILL)***?-' - '" - 45 65 * Level backfill behind a retaining wall is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall. ** E.I. <20, P.I. <15, SE >30, <10% passing No. 200 sieve. *** Native backfill with EFW shown are for very low to low expansive soils (E.I. = 0-50, P.I. <15). Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in geofabric and outlets. A backdrain system is considered necessary for retaining walls that are 2 feet or greater in height. Details 1, 2, and 3, present the backdrainage options discussed below. Backdrains should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or %-inch to 11/2-inch gravel wrapped in approved filter fabric (Mirafi 140 or equivalent). For low expansive backfill, the filter material should extend a minimum of 1 horizontal foot behind the base of the walls and upward at least 1 foot. For native backfill that has up to medium expansion potential, continuous Class 2 permeable drain materials should be used behind the wall. This material should be continuous (i.e., full height) behind the wall, and it should be constructed in accordance with the enclosed Detail 1 (Typical Retaining Wall Backfill and Drainage Detail). For limited access and confined areas, (panel) drainage behind the wall may be constructed in accordance with Detail 2 (Retaining Wall Backfill and Subdrain Detail Geotextile Drain). Materials with an E.I. potential of greater than 50 should not be used as backfill for retaining walls. For more onerous expansive situations, backfill and drainage behind the retaining wall should conform with Detail 3 (Retaining Wall and Subdrain Detail Clean Sand Backfill). Outlets should consist of a 4-inch diameter solid PVC or ABS pipe spaced no greater than ±100 feet apart, with a minimum of two outlets, one on each end. The use of weep holes, only, in walls higher than 2 feet, is not recommended. The surface of the backfill should be sealed by pavement or the top 18 inches compacted with native soil (E.I. <50). Proper surface drainage should also be provided. For additional mitigation, consideration should be given to applying a water-proof membrane to the back of all retaining structures. The use of a waterstop should be considered for all concrete and masonry joints. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 19 GeoSoils, Inc. (1) Waterproofing membrane CMUor reinforced-concrete wall Structural footing or settlement-sensitive improvement Provide surface drainage via an engineered V-ditch (see civil plans for details) Proposed grade sloped to drain per precise civil drawings (5) Weep hole AYC- Footing and wall design by others , . ."^-^ .Slope".or fevel ... ... . - ;•/ GraveJ /— (3 j .Filter ;f abric Native backfill =1 (h:v) or flatter backcut to be properly benched (6) Footing (1) Waterproofing membrane. (2) Gravel; Clean, crushed, % to 1% inch. (3) Filter fabric: Mirafi 140N or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient sloped to suitable, approved outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Footing: |f bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. RETAINING WALL DETAIL - ALTERNATIVE A Detail 1 (1) Waterproofing membrane (optional) CMUor reinforced-concrete wall 6 inches (5) Weep hole- £Proposed grade sloped to drain per precise civil drawings \ Footing and wall design by others. Structural footing or settlement-sensitive improvement Provide surface drainage via engineered -ditch (see civil plan details) (h:v) slope ." " . ."•- .- • " •"' * : >^. Slope; or . '• - '•..•• '•••• • * »•••..•• • • .•' '. •. -•""•' ••'.'.',- •'•• -'''•:••' "•'•:•/ fevel- ••,.•.'./:•..-. ••'•-.':/ ••'-' • ^ ;_'• • "- • / : -.•'• ••': ' •"'•'•""/' • . '• •. ' .-. .'. y\ A <1 * . • . •* •. ' ^X^ (2) Composite.. - -\ '-.y^-- "••••; drain - . ''.... ;••:' ; ^^>- (3)Filter;fabrb^Native backfill 11 (Irv) or flatter backcut to be properly benched (6) 1 cubic foot of %-inch crushed rock (7) Footing (1) Waterproofing membrane (optional): Liquid boot or approved mastic equivalent. (2) Drain: Miradrain 6000 or J-drain 200 or equivalent for non-waterproofed walls; Miradrain 6200 or J-drain 200 or equivalent for waterproofed walls (all perforations down). (3) Filter fabric: Mirafi 140N or approved equivalent; place fabric flap behind core. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Graveh clean, crushed, % to 1)^ inch. (7) Footing: If bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. RETAINING WALL DETAIL - ALTERNATIVE B Detail 2 (1) Waterproofing membrane CMUor reinforced-concrete wall --it ±12 inches (5) Weep hole- {Proposed grade sloped to drain per precise civil drawingsxs \ \. T\ \"7" V Structural footing or settlement-sensitive improvement Provide surface drainage (h=v) slope Slope"! or level . .. :. H/2.; .•••^-l- :'/ minimum'•'•• • '•-,' '• ' Footing and wall design by others (3) Filter fabric (2) Gravel (4) Pipe (7) Footing (8) Native backfill (6) Clean sand backfill 11 (h=v) or flatter backcut to be properly benched (1) Waterproofing membrane: Liquid boot or approved masticequivalent. (2) Graveh Clean, crushed, % to 1}£ inch. (3) Filter fabric: Mirafi 140N or approved equivalent. (4) Pipe: 4-inch-diameter perforated PVC, Schedule 40, or approved alternative with minimum of 1 percent gradient to proper outlet point (perforations down). (5) Weep hole: Minimum 2-inch diameter placed at 20-foot centers along the wall and placed 3 inches above finished surface. Design civil engineer to provide drainage at toe of wall. No weep holes for below-grade walls. (6) Clean sand backfill: Must have sand equivalent value (S.E.) of 35 or greater; can be densified by water jetting upon approval by geotechnical engineer. (7) Footing: |f bench is created behind the footing greater than the footing width, use level fill or cut natural earth materials. An additional "heel" drain will likely be required by geotechnical consultant. (8) Native backfill: If El. <21 and S.E. >35 then all sand requirements also may not be required and will be reviewed by the geotechnical consultant. RETAINING WALL DETAIL - ALTERNATIVE C Detail 3 Wall/Retaining Wall Footing Transitions Site walls are anticipated to be founded on footings designed in accordance with the recommendations in this report. Should wall footings transition from cut to fill, the civil designer may specify either: a) A minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 2H, from the point of transition. b) Increase of the amount of reinforcing steel and wall detailing (i.e., expansion joints or crack control joints) such that a angular distortion of 1 /360 for a distance of 2H on either side of the transition may be accommodated. Expansion joints should be placed no greater than 20 feet on-center, in accordance with the structural engineer's/wall designer's recommendations, regardless of whether or not transition conditions exist. Expansion joints should be sealed with a flexible, non-shrink grout. c) Embed the footings entirely into native formational material (i.e., deepened footings). If transitions from cut to fill transect the wall footing alignment at an angle of less than 45 degrees (plan view), then the designer should follow recommendation "a" (above) and until such transition is between 45 and 90 degrees to the wall alignment. TOP-OF-SLOPE WALLS/FENCES/IMPROVEMENTS AND EXPANSIVE SOILS Expansive Soils and Slope Creep Soils at the site are likely to be expansive and therefore, become desiccated when allowed to dry. Such soils are susceptible to surficial slope creep, especially with seasonal changes in moisture content. Typically in southern California, during the hot and dry summer period, these soils become desiccated and shrink, thereby developing surface cracks. The extent and depth of these shrinkage cracks depend on many factors such as the nature and expansivity of the soils, temperature and humidity, and extraction of moisture from surface soils by plants and roots. When seasonal rains occur, water percolates into the cracks and fissures, causing slope surfaces to expand, with a corresponding loss in soil density and shear strength near the slope surface. With the passage of time and several moisture cycles, the outer 3 to 5 feet of slope materials experience a very slow, but progressive, outward and downward movement, known as slope creep. For slope heights greater than 10 feet, this creep related soil movement will typically impact all rear yard flatwork and other secondary improvements that are located within about 15 feet from the top of slopes, such as swimming pools, concrete flatwork, etc., and in particular top of slope fences/walls. This influence is normally in the form of detrimental settlement, and tilting of the proposed improvements. The dessication/swelling and creep discussed above continues over the life of the improvements, and generally Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\524A5247b1 .ros Page 23 GeoSoils, Inc. becomes progressively worse. Accordingly, the developer should provide this information to any owners and owners association and/or any interested/affected parties. Top of Slope Walls/Fences Due to the potential for slope creep for slopes higher than about 10 feet, some settlement and tilting of the walls/fence with the corresponding distresses, should be expected. To mitigate the tilting of top of slope walls/fences, we recommend that the walls/fences be constructed on a combination of grade beam and caisson foundations. The grade beam should be at a minimum of 12 inches by 12 inches in cross section, supported by drilled caissons, 12 inches minimum in diameter, placed at a maximum spacing of 6 feet on center, and with a minimum embedment length of 7 feet below the bottom of the grade beam. The strength of the concrete and grout should be evaluated by the structural engineer of record. The proper ASTM tests for the concrete and mortar should be provided along with the slump quantities. The concrete used should be appropriate to mitigate sulfate corrosion, as warranted. The design of the grade beam and caissons should be in accordance with the recommendations of the project structural engineer, and include the utilization of the following geotechnical parameters: Creep Zone: Creep Load: Point of Fixity: Passive Resistance: 5-foot vertical zone below the slope face and projected upward parallel to the slope face. The creep load projected on the area of the grade beam should be taken as an equivalent fluid approach, having a density of 60 pcf. For the caisson, it should be taken as a uniform 900 pounds per linear foot of caisson's depth, located above the creep zone. Located a distance of 1.5 times the caisson's diameter, below the creep zone. Passive earth pressure of 300 psf per foot of depth per foot of caisson diameter, to a maximum value of 4,500 psf may be used to determine caisson depth and spacing, provided that they meet or exceed the minimum requirements stated above. To determine the total lateral resistance, the contribution of the creep prone zone above the point of fixity, to passive resistance, should be disregarded. Robertson Family Trust PA-12 & PA-13, Robertson Ranch West File:e:\wp9\5247\5247b1 .ros W.O. 5247-B1-SC June 5, 2008 Page 24 GeoSotls, Inc. Allowable Axial Capacity: Shaft capacity : 350 psf applied below the point of fixity over the surface area of the shaft. Tip capacity: 4,500 psf. EXPANSIVE SOILS. DRIVEWAY. FLATWORK. AND OTHER IMPROVEMENTS The soil materials on site are likely to be expansive. The effects of expansive soils are cumulative, and typically occur over the lifetime of any improvements. On relatively level areas, when the soils are allowed to dry, the dessication and swelling process tends to cause heaving and distress to flatwork and other improvements. The resulting potential for distress to improvements may be reduced, but not totally eliminated. To that end, it is recommended that the developer should notify any owners, owners association, and/or any interested/affected parties of this long-term potential for distress. To reduce the likelihood of distress, the following recommendations are presented for all exterior flatwork: 1. The subgrade area for concrete slabs should be compacted to achieve a minimum 90 percent relative compaction, and then be presoaked to 2 to 3 percentage points above (or 125 percent of) the soils' optimum moisture content, to a depth of 18 inches below subgrade elevation. The moisture content of the subgrade should be proof tested within 72 hours prior to pouring concrete. 2. Concrete slabs should be cast over a relatively non-yielding surface, consisting of a 4-inch layer of crushed rock, gravel, or clean sand, that should be compacted and level prior to pouring concrete. The layer should wet-down completely prior to pouring concrete, to minimize loss of concrete moisture to the surrounding earth materials. 3. Exterior slabs should be a minimum of 4 inches thick. Driveway slabs and approaches should additionally have a thickened edge (12 inches) adjacent to all landscape areas, to help impede infiltration of landscape water under the slab. 4. The use of transverse and longitudinal control joints are recommended to help control slab cracking due to concrete shrinkage or expansion. Two ways to mitigate such cracking are: a) add a sufficient amount of reinforcing steel, increasing tensile strength of the slab; and, b) provide an adequate amount of control and/or expansion joints to accommodate anticipated concrete shrinkage and expansion. In order to reduce the potential for unsightly cracks, slabs should be reinforced at mid-height with a minimum of No. 3 bars placed at 18 inches on center, in each direction. The exterior slabs should be scored or saw cut, 1/2 to 3/s inches deep, Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 25 GeoSoilSj Inc. 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 intervals of every 6 feet. The slabs should be separated from the foundations and sidewalks with expansion joint filler material. 5. No traffic should be allowed upon the newly poured concrete slabs until they have been properly cured to within 75 percent of design strength. Concrete compression strength should be a minimum of 2,500 psi. 6. Driveways, sidewalks, and patio slabs adjacent to the house should be separated from the house with thick expansion joint filler material. In areas directly adjacent to a continuous source of moisture (i.e., irrigation, planters, etc.), all joints should be additionally sealed with flexible mastic. 7. Planters and walls should not be tied to the house, 8. Overhang structures should be supported on the slabs, or structurally designed with continuous footings tied in at least two directions. 9. Any masonry landscape walls that are to be constructed throughout the property should be grouted and articulated in segments no more than 20 feet long. These segments should be keyed or doweled together. 10. Utilities should be enclosed within a closed utilidor (vault) or designed with flexible connections to accommodate differential settlement and expansive soil conditions. 11. Positive site drainage should be maintained at all times. Finish grade on the lots should provide a minimum of 1 to 2 percent fall to the street, as indicated herein. It should be kept in mind that drainage reversals could occur, including post-construction settlement, if relatively flat yard drainage gradients are not periodically maintained by the owner, owners association, or any interested/affected parties. 12. Due to expansive soils, air conditioning (A/C) units should be supported by slabs that are incorporated into the building foundation or constructed on a rigid slab with flexible couplings for plumbing and electrical lines. A/C waste water lines should be drained to a suitable non-erosive outlet. 13. Shrinkage cracks could become excessive if proper finishing and curing practices are not followed. Finishing and curing practices should be performed per the Portland Cement Association Guidelines. Mix design should incorporate rate of curing for climate and time of year, sulfate content of soils, corrosion potential of soils, and fertilizers used on site. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 26 GeoSoilfj Inc. PRELIMINARY PAVEMENT DESIGN Pavement sections presented are based on the R-value data (to be verified by specific R-value testing at completion of grading) from a representative sample taken from the project area, the anticipated design classification, and the minimum requirements of the City. For planning purposes, pavement sections consisting of asphaltic concrete over base are provided. Anticipated asphaltic concrete (AC) pavement sections are presented on the following table. ASPHALTIC CONCRETE PAVEMENT TRAFFIC AREA Cul De Sac Local Street Collector TRAFFIC INDEX*2* (Tl, Assumed) 4.5 5.0 6.0 SUBGRADE R-VALUE (Subgrade Parent Material) 12 12 12 A.C. THICKNESS (inches) 4.0 4.0 4.0 CLASS 2 AGGREGATE BASE THICKNESS™ (inches) 5.0 6.0 12.0 (1)Denotes standard Caltrans Class 2 aggregate base R >78, SE J>22). (2)TI values have been assumed for planning purposes herein and should be confirmed by the design team during future plan development. The recommended pavement sections provided above are meant as minimums. If thinner or highly variable pavement sections are constructed, increased maintenance and repair could be expected. If the ADT (average daily traffic) beyond that intended, as reflected by the traffic index used for design, increased maintenance and repair could be required for the pavement section. Subgrade preparation and aggregate base preparation should be performed in accordance with the recommendations presented below, and the minimum subgrade (upper 12 inches) and Class 2 aggregate base compaction should be 95 percent of the maximum dry density (ASTM D 1557). If adverse conditions (i.e., saturated ground, etc.) are encountered during preparation of subgrade, special construction methods may need to be employed. These recommendations should be considered preliminary. Further R-value testing and pavement design analysis should be performed upon completion of precise grading for the site. Robertson Family Trust PA-12 & PA-13, Robertson Ranch West File:e:\wp9\5247\5247b1 .ros GeoSoils, Inc. W.O. 5247-B1-SC June 5, 2008 Page 27 PAVEMENT GRADING RECOMMENDATIONS General All section changes should be properly transitioned. If adverse conditions are encountered during the preparation of subgrade materials, special construction methods may need to be employed. Subarade Within street areas, all surficial deposits of loose soil material should be removed and recompacted as recommended. After the loose soils are removed, the bottom is to be scarified to a depth of 12 inches, moisture conditioned as necessary and compacted to 95 percent of maximum laboratory density, as determined by ASTM test method D 1557. Deleterious material, excessively wet or dry pockets, concentrated zones of oversized rock fragments, and any other unsuitable materials encountered during grading should be removed. The compacted fill material should then be brought to the elevation of the proposed subgrade for the pavement. The subgrade should be proof-rolled in order to ensure a uniformly firm and unyielding surface. All grading and fill placement should be observed by the project soil engineer and/or his representative. Base Compaction tests are required for the recommended base section. Minimum relative compaction required will be 95 percent of the maximum laboratory density as determined by ASTM test method D 1557. Base aggregate should be in accordance to the "Standard Specifications for Public Works Construction" (green book) current edition. *Paving Prime coat may be omitted if all of the following conditions are met: 1. The asphalt pavement layer is placed within two weeks of completion of base and/or subbase course. 2. Traffic is not routed over completed base before paving. 3. Construction is completed during the dry season of May through October. 4. The base is free of dirt and debris. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 28 GeoSoils, Inc. If construction is performed during the wet season of November through April, prime coat may be omitted if no rain occurs between completion of base course and paving and the time between completion of base and paving is reduced to three days, provided the base is free of dirt and debris. Where prime coat has been omitted and rain occurs, traffic is routed over base course, or paving is delayed, measures shall be taken to restore base course, subbase course, and subgrade to conditions that will meet specifications as directed by the soil engineer. Drainage Positive drainage should be provided for all surface water to drain towards the area swale, curb and gutter, or to an approved drainage channel. Positive site drainage should be maintained at all times. Water should not be allowed to pond or seep into the ground. If planters or landscaping are adjacent to paved areas, measures should be taken to minimize the potential for water to enter the pavement section. DEVELOPMENT CRITERIA Slope Deformation Compacted fill slopes designed using customary factors of safety for gross or surficial stability and constructed in general accordance with the design specifications should be expected to undergo some differential vertical heave or settlement in combination with differential lateral movement in the out-of-slope direction, after grading. This post-construction movement occurs in two forms: slope creep, and lateral fill extension (LFE). Slope creep is caused by alternate wetting and drying of the fill soils which results in slow downslope movement. This type of movement is expected to occur throughout the life of the slope, and is anticipated to potentially affect improvements or structures (e.g., separations and/or cracking), placed near the top-of-slope, up to a maximum distance of approximately 15 feet from the top-of-slope, depending on the slope height. This movement generally results in rotation and differential settlement of improvements located within the creep zone. LFE occurs due to deep wetting from irrigation and rainfall on slopes comprised of expansive materials. Although some movement should be expected, long-term movement from this source may be minimized, but not eliminated, by placing the fill throughout the slope region, wet of the fill's optimum moisture content. It is generally not practical to attempt to eliminate the effects of either slope creep or LFE. Suitable mitigative measures to reduce the potential of lateral deformation typically include: setback of improvements from the slope faces (per the 1997 UBC and/or adopted California Building Code), positive structural separations (i.e., joints) between improvements, and stiffening and deepening of foundations. Expansion joints in walls should be placed no greater than 20 feet on-center, and in accordance with the structural engineer's recommendations. All of these measures are recommended for design of structures and improvements. The ramifications of the above conditions, and Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 29 GeoSoils, Inc. recommendations for mitigation, should be provided to each owner and/or any owners association. Slope Maintenance and Planting Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Positive surface drainage away from slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Over-watering should be avoided as it adversely affects site improvements, and causes perched groundwater conditions. Graded slopes constructed utilizing onsite materials would be erosive. Eroded debris may be minimized and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover soon after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for landscaping should be light weight, deep rooted types that require little water and are capable of surviving the prevailing climate. Jute-type matting or other fibrous covers may aid in allowing the establishment of a sparse plant cover. Utilizing plants other than those recommended above will increase the potential for perched water, staining, mold, etc., to develop. A rodent control program to prevent burrowing should be implemented. Irrigation of natural (ungraded) slope areas is generally not recommended. These recommendations regarding plant type, irrigation practices, and rodent control should be provided to each owner or any interested/affected parties. Over-steepening of slopes should be avoided during building construction activities and landscaping. Drainage Adequate lot surface drainage is a very important factor in reducing the likelihood of adverse performance of foundations, hardscape, and slopes. Surface drainage should be sufficient to prevent ponding of water anywhere on a lot, and especially near structures and tops of slopes. Lot surface drainage should be carefully taken into consideration during fine grading, landscaping, and building construction. Therefore, care should betaken that future landscaping or construction activities do not create adverse drainage conditions. Positive site drainage within lots and common areas should be provided and maintained at all times. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and not allowed to pond and/or seep into the ground. In general, the area within 5 feet around a structure should slope away from the structure. We recommend that unpaved lawn and landscape areas have a minimum gradient of 1 percent sloping away from structures, and whenever possible, should be above adjacent paved areas. Consideration should be given to avoiding construction of planters adjacent to structures (buildings, pools, spas, etc.). Pad drainage should be directed toward the street or other approved area(s). Although not a geotechnical requirement, roof gutters, down spouts, or other appropriate means may be utilized to control roof drainage. Down spouts, or drainage devices should outlet a minimum of 5 feet from structures or into a subsurface drainage system. Areas of seepage may develop due to irrigation or heavy rainfall, and should be anticipated. Minimizing irrigation will lessen Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 30 GeoSoils, Inc. this potential. If areas of seepage develop, recommendations for minimizing this effect could be provided upon request. Toe of Slope Drains/Toe Drains Where significant slopes intersect pad areas, surface drainage down the slope allows for some seepage into the subsurface materials, sometimes creating conditions causing or contributing to perched and/or ponded water. Toe of slope/toe drains may be beneficial in the mitigation of this condition due to surface drainage. The general criteria to be utilized by the design engineer for evaluating the need for this type of drain is as follows: • Is there a source of irrigation above or on the slope that could contribute to saturation of soil at the base of the slope? • Are the slopes hard rock and/or impermeable, or relatively permeable, or; do the slopes already have or are they proposed to have subdrains (i.e., stabilization fills, etc.)? Are there cut-fill transitions (i.e., fill over bedrock), within the slope? • Was the lot at the base of the slope overexcavated or is it proposed to be overexcavated? Overexcavated lots located at the base of a slope could accumulate subsurface water along the base of the fill cap. Are the slopes north facing? North facing slopes tend to receive less sunlight (less evaporation) relative to south facing slopes and are more exposed to the currently prevailing seasonal storm tracks. • What is the slope height? It has been our experience that slopes with heights in excess of approximately 10 feet tend to have more problems due to storm runoff and irrigation than slopes of a lesser height. Do the slopes "toe out" into a residential lot or a lot where perched or ponded water may adversely impact its proposed use? Based on these general criteria, the construction of toe drains may be considered by the design engineer along the toe of slopes, or at retaining walls in slopes, descending to the rear of such lots. Following are Detail 4 (Schematic Toe Drain Detail) and Detail 5 (Subdrain Along Retaining Wall Detail). Other drains may be warranted due to unforeseen conditions, owner irrigation, or other circumstances. Where drains are constructed during grading, including subdrains, the locations/elevations of such drains should be surveyed, and recorded on the final as-built grading plans by the design engineer. It is recommended that the above be disclosed to all interested parties, including owners, owners association, and any interested/affected parties. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1 .ros Page 31 GeoSoils, Inc. Drain pipe Permeable material ——12 inches——J Drain may be constructed into, or at, the toe-of-slope 12-inch minimum 24-inch minimum 1. Soil cap compacted to 90 percent relative compaction. 2. Permeable material may be gravel wrapped in filter fabric (Mirafi 140N or equivalent). 3. 4-inch-diameter, perforated pipe (SDR-35 or equivalent) with perforations down. 4. Pipe to maintain a minimum 1 percent fall. 5. Concrete cut-off wall to be provided at transition to solid outlet pipe. 6. Solid outlet pipe to drain to approved area. 7. Cleanouts are recommended at each property line. SCHEMATIC TOE DRAIN DETAIL Detail 4 2=1 (H=V) slope (typical) Backfill with compacted native soils Top of wall Retaining wall Finish grade Mirafi 140 filter fabric or equivalent %-inch crushed gravel Wall footing 4-inch drain 1 to 2 f. NOTES: 1. Soil cap compacted to 90 percent relative compaction. 2. Permeable material may be gravel wrapped in filter fabric (Mirafi 140N or equivalent). 3. 4-inch-diameter, perforated pipe (SDR-35 or equivalent) with perforations down. 4. Pipe to maintain a minimum 1 percent fall. 5. Concrete cut-off wall to be provided at transition to solid outlet pipe. 6. Solid outlet pipe to drain to approved area. 7. Cleanouts are recommended at each property line. 8. Effort to compact should be applied to drain rock. SUBDRAIN ALONG RETAINING WALL DETAIL Detail 5 Erosion Control Cut and fill slopes will be subject to surficial erosion during and after grading. Onsite earth materials have a moderate to high erosion potential. Consideration should be given to providing hay bales and silt fences for the temporary control of surface water, from a geotechnical viewpoint. Landscape Maintenance Only the amount of irrigation necessary to sustain plant life should be provided. Over-watering the landscape areas will adversely affect proposed site improvements. We would recommend that any proposed open-bottom planters adjacent to proposed structures be eliminated for a minimum distance of 10 feet. As an alternative, closed-bottom type planters could be utilized. An outlet placed in the bottom of the planter, could be installed to direct drainage away from structures or any exterior concrete flatwork. If planters are constructed adjacent to structures, the sides and bottom of the planter should be provided with a moisture barrier to prevent penetration of irrigation water into the subgrade. Provisions should be made to drain the excess irrigation water from the planters without saturating the subgrade below or adjacent to the planters. Graded slope areas should be planted with drought resistant vegetation. Consideration should be given to the type of vegetation chosen and their potential effect upon surface improvements (i.e., some trees will have an effect on concrete flatwork with their extensive root systems). From a geotechnical standpoint leaching is not recommended for establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent minimum relative compaction. Gutters and Downspouts As previously discussed in the drainage section, the installation of gutters and downspouts should be considered to collect roof water that may otherwise infiltrate the soils adjacent to the structures. If utilized, the downspouts should be drained into PVC collector pipes or other non-erosive devices (e.g., paved swales or ditches; below grade, solid tight-lined PVC pipes; etc.), that will carry the water away from the house, to an appropriate outlet, in accordance with the recommendations of the design civil engineer. Downspouts and gutters are not a requirement; however, from a geotechnical viewpoint, provided that positive drainage is incorporated into project design (as discussed previously). Subsurface and Surface Water Subsurface and surface water are not anticipated to affect site development, provided that the recommendations contained in this report are incorporated into final design and construction and that prudent surface and subsurface drainage practices are incorporated into the construction plans. Perched groundwater conditions along zones of contrasting permeabilities may not be precluded from occurring in the future due to site irrigation, poor Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b>1 .ros Page 34 GeoSoils, Inc. drainage conditions, or damaged utilities, and should be anticipated. Should perched groundwater conditions develop, this office could assess the affected area(s) and provide the appropriate recommendations to mitigate the observed groundwater conditions. Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors. Site Improvements If in the future, any additional improvements (e.g., pools, spas, etc.) are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. Pools and/or spas should not be constructed without specific design and construction recommendations from GSI, and this construction recommendation should be provided to the owners, any owners association, and/or other interested parties. This office should be notified in advance of any fill placement, grading of the site, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills, flatwork, etc. Tile Flooring Tile flooring can crack, reflecting cracks in the concrete slab below the tile, although small cracks in a conventional slab may not be significant. Therefore, the designer should consider additional steel reinforcement for concrete slabs-on-grade where tile will be placed. The tile installer should consider installation methods that reduce possible cracking of the tile such as slipsheets. Slipsheets or a vinyl crack isolation membrane (approved by the Tile Council of America/Ceramic Tile Institute) are recommended between tile and concrete slabs on grade. Additional Grading This office should be notified in advance of any fill placement, supplemental regrading of the site, or trench backfilling after rough grading has been completed. This includes completion of grading in the street, driveway approaches, driveways, parking areas, and utility trench and retaining wall backfills. Footing Trench Excavation All footing excavations should be observed by a representative of this firm subsequent to trenching and prior to concrete form and reinforcement placement. The purpose of the observations is to evaluate that the excavations have been made into the recommended bearing material and to the minimum widths and depths recommended for construction. If loose or compressible materials are exposed within the footing excavation, a deeper footing or removal and recompaction of the subgrade materials would be recommended at that time. Footing trench spoil and any excess soils generated from utility trench Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 35 GeoSoils, Inc. excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site. Trenching/Temporary Construction Backcuts Considering the nature of the onsite earth materials, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching. Shoring or excavating the trench walls/backcuts at the angle of repose (typically 25 to 45 degrees [except as specifically superceded within the text of this report]), should be anticipated. All excavations should be observed by an engineering geologist or soil engineer from GSI, prior to workers entering the excavation or trench, and minimally conform to Cal-OSHA, state, and local safety codes. Should adverse conditions exist, appropriate recommendations would be offered at that time. The above recommendations should be provided to any contractors and/or subcontractors, or owners, etc., that may perform such work. Utility Trench Backfill 1. All interior utility trench backfill should be brought to at least 2 percent above optimum moisture content and then compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. As an alternative for shallow (12-inch to 18-inch) under-slab trenches, sand having a sand equivalent value of 30 or greater may be utilized and jetted or flooded into place. Observation, probing and testing should be provided to evaluate the desired results. 2. Exterior trenches adjacent to, and within areas extending below a 1:1 plane projected from the outside bottom edge of the footing, and all trenches beneath hardscape features and in slopes, should be compacted to at least 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used in these backfill areas. Compaction testing and observations, along with probing, should be accomplished to evaluate the desired results. 3. All trench excavations should conform to Cal-OSHA, state, and local safety codes. 4. Utilities crossing grade beams, perimeter beams, or footings should either pass below the footing or grade beam utilizing a hardened collar or foam spacer, or pass through the footing or grade beam in accordance with the recommendations of the structural engineer. Robertson Family Trust W.O. 5247-B1-SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 36 GeoSofls, Inc. SUMMARY OF RECOMMENDATIONS REGARDING GEOTECHNICAL OBSERVATION AND TESTING We recommend that observation and/or testing be performed by GSI at each of the following construction stages: • During grading/recertification. • During excavation. • During placement of subdrains, toe drains, or other subdrainage devices, prior to placing fill and/or backfill. • After excavation of building footings, retaining wall footings, and free standing walls footings, prior to the placement of reinforcing steel or concrete. • Prior to pouring any slabs or flatwork, after presoaking/presaturation of building pads and other flatwork subgrade, before the placement of concrete, reinforcing steel, capillary break (i.e., sand, pea-gravel, etc.), or vapor retarders (i.e., visqueen, etc.). • During retaining wall subdrain installation, prior to backfill placement. • During placement of backfill for area drain, interior plumbing, utility line trenches, and retaining wall backfill. • During slope construction/repair. • When any unusual soil conditions are encountered during any construction operations, subsequent to the issuance of this report. • When any developer or owner improvements, such as flatwork, spas, pools, walls, etc., are constructed, prior to construction. GSI should review and approve such plans prior to construction. • A report of geotechnical observation and testing should be provided at the conclusion of each of the above stages, in order to provide concise and clear documentation of site work, and/or to comply with code requirements. GSI should review project sales documents to owners/owners associations for geotechnical aspects, including irrigation practices, the conditions outlined above, etc., prior to any sales. At that stage, GSI will provide owners maintenance guidelines which should be incorporated into such documents. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 37 GeoSoils, Inc. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer, structural engineer, post-tension designer, architect, landscape architect, wall designer, etc., should review the recommendations provided herein, incorporate those recommendations into all their respective plans, and by explicit reference, make this report part of their project plans. This report presents minimum design criteria for the design of slabs, foundations and other elements possibly applicable to the project. These criteria should not be considered as substitutes for actual designs by the structural engineer/designer. Please note that the recommendations contained herein are not intended to preclude the transmission of water or vapor through the slab or foundation. The structural engineer/foundation and/or slab designer should provide recommendations to not allow water or vapor to enter into the structure so as to cause damage to another building component, or so as to limit the installation of the type of flooring materials typically used for the particular application. The structural engineer/designer should analyze actual soil-structure interaction and consider, as needed, bearing, expansive soil influence, and strength, stiffness and deflections in the various slab, foundation, and other elements in order to develop appropriate, design-specific details. As conditions dictate, it is possible that other influences will also have to be considered. The structural engineer/designer should consider all applicable codes and authoritative sources where needed. If analyses by the structural engineer/designer result in less critical details than are provided herein as minimums, the minimums presented herein should be adopted. It is considered likely that some, more restrictive details will be required. If the structural engineer/designer has any questions or requires further assistance, they should not hesitate to call or otherwise transmit their requests to GSI. In order to mitigate potential distress, the foundation and/or improvement's designer should confirm to GSI and the governing agency, in writing, that the proposed foundations and/or improvements can tolerate the amount of differential settlement and/or expansion characteristics and other design criteria specified herein. PLAN REVIEW Final project plans (grading, precise grading, foundation, retaining wall, landscaping, etc.), should be reviewed by this office prior to construction, so that construction is in accordance with the conclusions and recommendations of this report. Based on our review, supplemental recommendations and/or further geotechnical studies may be warranted. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 38 GeoSoils, Inc. LIMITATIONS The materials encountered on the project site and utilized for our analysis are believed representative of the area; however, soil and bedrock materials vary in character between excavations and natural outcrops or conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. Inasmuch as our study is based upon our review and engineering analyses and laboratory data, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty, either express or implied, is given. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction; or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Thus, this report brings to completion our scope of services for this portion of the project. All samples will be disposed of after 30 days, unless specifically requested by the Client, in writing. Robertson Family Trust W.O. 5247-B1 -SC PA-12 & PA-13, Robertson Ranch West June 5, 2008 File:e:\wp9\5247\5247b1.ros Page 39 GeoSoils, Inc. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to contact the project manager, Bryan E. Voss, at our office. Respectfully submitted, GeoSoils. Inc. £]/*ftt ' iryan byvoss ProjecfManager/St n P. Franklin Engineering Geolog^ BEV/JPF/BBS/jk/jh Attachments: Certified Engineering Geologist B^rfShahrvini eotechnical Enginee Distribution: Table 1 - Field Density Test Results Appendix - References Plates 1 and 2 - Field Density Test Location Map (3) Addressee (1) O'Day Consultants, Attention: Mr. Keith Hansen Robertson Family Trust PA-12 & PA-13, Robertson Ranch West File:e:\wp9\5247\5247b1 .ros W.O. 5247-81-SC June 5, 2008 Page 40 GeoSoils, Inc. Table 1 FIELD DENSITY TEST RESULTS TEST NO. 1* 1A 2* 2A 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 DATE 2/7/08 2/7/08 2/7/08 2/7/08 2/7/08 2/7/08 2/8/08 2/8/08 2/8/08 2/8/08 2/8/08 2/8/08 2/8/08 2/8/08 2/8/08 2/8/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/9/08 2/11/08 2/11/08 2/11/08 2/11/08 2/11/08 2/11/08 2/11/08 2/11/08 2/11/08 2/12/08 2/12/08 2/12/08 2/12/08 2/12/08 2/12/08 2/12/08 TEST LOCATION SEPA-12 SEPA-12 SEPA-12 SEPA-12 _j SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SEPA-12 SWPA12 SWPA12 SEPA12 SWPA12 SWPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SWPA12 SEPA12 SEPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 ELEV OR DEPTH (ft) 35.0 35.0 35.0 35.0 37.0 37.0 38.0 38.0 40.0 40.0 42.0 43.0 45.0 45.0 47.0 47.0 35.0 35.0 38.0 40.0 40.0 42.0 44.0 46.0 48.0 48.0 50.0 50.0 39.0 45.0 43.0 42.0 40.0 41.0 37.0 44.0 42.0 41.0 37.0 39.0 38.0 41.0 40.0 39.0 MOISTURE CONTENT (%) 13.6 14.1 13.9 14.2 14.2 14.7 14.6 15.0 14.0 14.6 15.3 14.9 15.2 14.7 14.4 14.0 15.9 16.8 17.0 16.5 13.8 15.0 14.7 18.2 17.7 17.9 18.4 18.8 14.4 15.7 16.2 14.7 15.9 15.6 11.2 13.7 12.8 13.5 16.0 14.0 15.2 12.4 15.7 11.7 DRY DENSITY (pcf) 109.3 116.4 112.1 115.8 115.6 116.2 118.4 116.1 115.6 117.0 116.4 116.1 116.9 115.8 115.7 116.1 106.6 106.4 106.8 106.2 116.0 115.8 115.6 107.6 106.7 106.2 106.6 106.3 115.2 110.2 115.3 108.4 108.0 106.8 116.1 107.4 115.2 109.5 106.4 107.4 106.5 113.0 107.6 112.2 REL COMP (%) 85.4 90.9 87.6 90.5 90.3 90.8 92.5 90.7 90.3 91.4 90.9 90.7 91.3 90.5 90.4 90.7 90.3 90.2 90.5 90.0 90.6 90.5 90.3 91.2 90.4 90.0 90.3 90.1 90.0 93.3 90.0 91.8 91.5 90.5 90.7 91.0 90.0 92.7 90.1 91.0 90.2 91.1 91.1 90.5 TEST METHOD SC ND ND ND ND ND SC ND ND ND ND ND SC ND ND ND ND ND ND ND ND ND SC SC ND ND ND ND ND ND ND ND SC ND ND ND ND ND ND ND ND SC ND SC SOIL TYPE B B B B B B B B B B B B B B B B A A A A B B B A A A A A B A B A A A B A B A A A A D A D Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros W.O. 5247-B1-SC June 2008 Page 1 GeoSoils, Inc. Table 1 FIELD DENSITY TEST RESULTS TEST NO. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70* 70A 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 DATE 2/12/08 2/12/08 2/12/08 2/13/08 2/13/08 2/13/08 2/13/08 2/13/08 2/13/08 2/13/08 2/13/08 2/13/08 2/13/08 2/14/08 2/14/08 2/14/08 2/14/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/19/08 2/20/08 2/20/08 2/20/08 2/20/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 2/21/08 TEST LOCATION SEPA12 SEPA12 SEPA12 SEPA12 SWPA12 SWPA12 SWPA12 SEPA12 SEPA12 SEPA12 SEPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SEPA12 SEPA12 SEPA12 SEPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SEPA12 SWPA12 SWPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SWPA12 SEPA12 ELEV OR DEPTH (ft) 46.0 45.0 42.0 43.0 42.0 41.0 42.0 47.0 44.0 43.0 48.0 44.0 45.0 41.0 41.0 42.0 42.0 44.0 44.0 46.0 46.0 46.0 47.0 47.0 49.0 49.0 48.0 49.0 49.0 46.0 46.0 46.0 46.0 45.0 45.0 47.0 47.0 47.0 47.0 49.0 49.0 49.0 50.0 50.0 MOISTURE CONTENT {%) 13.8 13.6 14.0 14.1 17.1 18.3 16.8 17.5 18.5 15.1 18.8 16.3 13.7 16.3 16.3 15.8 14.9 17.8 18.4 17.7 17.9 16.4 17.7 14.7 15.5 14.6 17.6 18.5 17.7 18.6 18.5 18.9 17.7 14.9 14.4 11.8 12.1 11.8 11.5 11.2 11.9 13.9 14.8 12.8 DRY DENSITY (pcf) 106.4 107.8 108.2 108.8 107.3 106.3 108.1 109.5 106.9 110.0 108.2 107.9 116.3 107.6 108.8 109.1 106.9 106.6 107.5 106.8 106.7 106.2 106.9 115.2 116.2 115.2 107.0 104.8 106.9 106.2 106.9 106.6 107.0 110.0 108.7 112.3 112.0 112.7 113.5 112.8 113.0 106.5 108.0 116.2 REL COMP (%) 90.1 91.3 91.6 92.2 90.9 90.0 91.6 92.7 90.5 93.2 91.6 91.5 93.0 91.1 92.2 92.4 90.5 90.3 91.1 90.5 90.4 90.0 90.6 90.0 90.8 90.0 90.7 88.8 90.6 90.0 90.6 90.3 90.7 93.2 92.1 90.6 90.3 90.9 91.5 90.2 90.4 90.3 91.5 90.8 TEST METHOD ND ND ND ND ND ND ND ND ND ND ND SC ND ND ND ND ND SC ND ND ND ND SC ND ND ND ND SC SC ND ND ND ND ND ND ND ND SC ND ND ND ND ND SC SOIL TYPE A A A A A A A A A A A A C A A A A A A A A A A B B B A A A A A A A A A D D D D C C A A B Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros GeoSoils, Inc. W.O. 5247-B1-SC June 2008 Page 2 Table 1 FIELD DENSITY TEST RESULTS TEST NO. 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109* 109A 110* 110A 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 DATE 2/28/08 2/28/08 2/28/08 2/28/08 2/28/08 2/29/08 2/29/08 2/29/08 2/29/08 2/29/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/3/08 3/4/08 3/4/08 3/4/08 3/4/08 3/4/08 3/4/08 3/4/08 3/4/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/5/08 3/6/08 TEST LOCATION SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SEPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 West PA 12 North PA 12 NEPA12 NEPA12 North PA 12 North PA 12 North PA 12 West PA 12 West PA 12 NEPA12 NEPA12 NEPA12 North PA 12 North PA 12 NWPA12 NWPA12 North PA 12 NEPA12 NWPA12 North PA 12 NEPA12 NWPA12 North PA 12 NEPA12 East PA 12 SEPA12 West PA 12 SWPA12 ELEV OR DEPTH (ft) 48.0 48.0 48.0 48.0 49.0 49.5 48.0 49.0 49.0 49.0 45.5 47.2 52.0 50.0 51.0 52.0 39.0 43.0 46.0 42.0 42.0 45.0 41.0 45.0 47.0 45.0 47.0 49.0 49.0 49.0 50.0 51.0 51.0 51.0 53.0 53.0 53.0 55.0 55.0 55.0 50.0 52.0 54.0 38.0 MOISTURE CONTENT {%) 12.9 11.1 15.9 11.1 15.6 14.7 15.1 14.8 14.2 14.0 13.6 11.8 16.5 15.8 14.6 13.5 17.8 14.4 14.3 13.3 13.6 15.7 14.8 12.5 14.0 11.3 13.9 15.0 15.5 18.0 14.0 14.2 13.6 14.5 22.4 21.9 21.8 23.5 22.0 21.6 13.7 11.6 11.7 14.2 DRY DENSITY 115.7 115.3 111.3 114.9 109.1 110.4 110.1 115.4 115.2 113.6 113.1 122.3 106.8 110.2 106.7 107.5 106.8 108.2 113.6 116.3 109.2 110.6 106.3 105.3 108.0 104.1 107.7 113.8 114.8 107.6 107.3 109.4 107.4 108.0 91.8 92.3 91.9 92.4 92.0 . 91.8 107.2 115.7 114.8 108.0 REL COMP (%) 90.4 90.1 94.3 91.9 92.5 93.6 93.3 90.2 90.0 91.6 91.2 95.5 90.5 93.4 90.4 91.1 90.5 91.6 90.9 93.0 92.5 93.7 90.0 89.2 91.5 88.2 91.3 91.0 91.8 91.2 90.8 92.7 91.0 91.5 90.0 90.5 90.1 90.6 90.2 90.0 90.8 92.6 91.8 91.5 TEST METHOD ND ND ND ND SC ND ND ND ND ND ND ND ND ND ND ND ND ND SC SC ND ND ND SC ND ND ND ND ND ND SC ND ND SC ND ND ND ND SC ND ND ND ND ND SOIL TYPE B B A C A A A B B D D B A A A A A A C C A A A A A A A C C A A A A A E E E E E E A C C A Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros GeoSoils, Inc. W.O. 5247-B1-SC June 2008 Pages Table 1 FIELD DENSITY TEST RESULTS TEST NO. 128 129 130* 130A 131* 131A 132* 132A 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 147' 148 148' 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 DATE 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/6/08 3/7/08 3/7/08 3/7/08 3/7/08 3/7/08 3/7/08 3/7/08 3/7/08 3/7/08 3/10/08 3/7/08 3/10/08 3/10/08 3/10/08 3/10/08 3/10/08 3/10/08 3/10/08 3/10/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 3/11/08 TEST LOCATION SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 Test Number Skipped SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA13 SWPA13 West PA 13 West PA 13 West PA 13 West PA 13 SWPA13 SWPA12 SWPA12 SWPA12 SWPA12 SWPA12 SWPA13 SWPA13 West PA 13 West PA 13 North PA 12 NWPA12 ELEV OR DEPTH (ft) 36.0 39.0 38.0 38.0 38.0 38.0 38.0 38.0 40.0 41.0 42.0 42.0 44.0 44.0 44.0 46.0 46.0 46.0 48.0 48.0 48.0 49.0 40.0 49.0 40.0 40.0 42.0 43.0 43.5 44.0 45.0 45.0 47.0 47.0 47.0 48.5 49.0 48.5 49.0 51.0 51.0 42.0 44.0 MOISTURE CONTENT <%) 13.8 13.6 12.0 12.4 11.6 12.8 14.1 14.6 15.7 14.5 15.2 12.3 11.3 13.8 14.2 15.9 13.8 16.7 13.8 14.6 13.5 11.8 14.9 12.6 15.6 14.7 15.5 13.7 14.2 14.8 16.7 14.8 16.1 15.8 15.9 14.8 16.0 16.5 15.7 15.5 16.4 12.0 12.5 DRY DENSITY 106.4 107.1 104.3 112.6 105.3 113.7 104.7 107.5 106.3 107.6 106.7 113.2 113.6 106.3 106.6 107.2 115.6 106.7 107.5 106.9 106.5 113.6 106.8 112.9 107.4 106.6 106.4 115.2 113.8 106.4 114.8 113.8 106.5 106.8 107.2 106.3 106.7 108.1 107.0 106.5 106.4 114.7 117.1 REL COMP (%) 90.2 90.8 84.1 90.8 84.9 91.7 88.7 91.1 90.1 91.2 90.4 90.6 90.9 90.1 90.3 90.8 90.3 90.4 91.1 90.6 90.3 91.6 90.5 91.0 91.0 90.3 90.2 92.9 91.8 90.2 92.6 91.8 90.3 90.5 90.8 90.1 90.4 91.6 90.7 90.3 90.2 92.5 94.4 TEST METHOD ND ND ND ND ND ND ND ND ND ND ND ND ND ND SC ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND SOIL TYPE A A D D D D A A A A A C C A A A B A A A A D A D A A A D D A D D A A A A A A A A A D D Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros W.O. 5247-B1-SC June 2008 Page 4 GeoSoilSj Inc. Table 1 FIELD DENSITY TEST RESULTS TEST NO. 167* 167A 168* 168A 169* 169A 170* 170A 171 172 173 174 175 176 177 178 179* 179A 180 181 182 183 184 185 186 187 188 189 190 191 192 193* 193A 194 195 196* 196A 197* 197A 198 199 200 201 202 DATE 3/12/08 3/12/08 3/12/08 3/12/08 3/12/08 3/12/08 3/12/08 3/12/08 3/12/08 3/12/08 3/13/08 3/13/08 3/13/08 3/13/08 3/13/08 3/13/08 3/13/08 3/13/08 3/13/08 3/14/08 3/14/08 3/14/08 3/14/08 3/14/08 3/14/08 3/17/08 3/17/08 3/17/08 3/17/08 3/17/08 3/17/08 3/17/08 3/18/08 3/18/08 3/18/08 3/18/08 3/18/08 3/18/08 3/18/08 3/18/08 3/19/08 3/19/08 3/19/08 3/19/08 TEST LOCATION West PA 13 West PA 13 West PA 13 West PA 13 SWPA13 SWPA13 SWPA13 SWPA13 West PA 13 West PA 13 NWPA13 NWPA13 West PA 13 NWPA13 NWPA13 NWPA13 West PA 13 West PA 13 NWPA13 SWPA13 SWPA13 West PA 13 NW PA 13 NWPA13 West PA 13 NWPA13 NWPA13 West PA 13 SWPA13 South PA 13 South PA 13 NWPA13 NWPA13 West PA 13 NWPA12 NWPA13 NWPA13 West PA 13 West PA 13 NWPA13 West PA 12 North PA 12 North PA 12 North PA 12 ELEV OR DEPTH (ft) 40.0 40.0 40.0 40.0 40.0 40.0 42.0 42.0 42.0 42.0 44.0 44.0 44.0 46.0 46.0 46.0 48.0 48.0 48.0 50.0 50.0 50.0 52.0 52.0 52.0 50.0 50.0 52.0 52.0 52.0 52.0 54.0 50.0 52.0 53.0 54.0 54.0 55.0 55.0 56.0 57.0 57.0 57.0 57.0 MOISTURE CONTENT {%) 13.8 12.9 13.4 11.9 14.5 13.2 12.7 12.7 14.6 15.5 12.9 11.8 14.9 12.0 11.7 14.7 11.7 14.1 12.4 13.8 15.0 14.7 15.2 12.4 13.1 13.6 14.0 12.3 11.7 12.3 11.7 8.1 13.6 12.1 12.3 11.7 14.7 11.7 8.1 11.2 23.6 21.9 22.7 24.7 DRY DENSITY (Prf) 106.5 113.8 106.8 112.9 107.2 113.8 106.3 111.8 106.5 106.3 111.6 112.2 106.4 112.8 115.6 107.0 104.3 106.8 112.7 106.4 107.1 106.9 106.2 114.2 113.1 106.6 106.5 114.5 113.8 113.0 116.2 109.2 106.6 111.5 114.5 100.2 107.3 100.4 108.7 115.6 92.6 92.8 93.4 92.1 REL COMP {%) 85.9 91.8 86.1 91.0 86.5 91.8 85.7 90.2 90.3 90.1 90.0 90.5 90.2 90.2 90.3 90.7 88.4 90.5 90.2 90.2 90.8 90.6 90.0 92.1 90.5 90.3 90.3 92.3 91.8 91.1 90.8 87.4 90.3 89.9 92.3 84.9 90.9 85.1 92.1 90.3 90.8 91.0 91.6 90.3 TEST METHOD SC ND ND ND ND ND ND ND ND SC ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND SC ND ND ND SC SC ND ND ND SOIL TYPE D D D D D D D D A A D D A C B A A A C A A A A D C A A D D D B C A D D A A A A B e E E E Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros GeoSoilSj Inc. W.O. 5247-B1-SC June 2008 PageS Table 1 FIELD DENSITY TEST RESULTS TEST NO, 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242* 242A 243 244 245 DATE 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/19/08 3/20/08 3/20/08 3/20/08 3/20/08 3/20/08 3/20/08 3/20/08 3/20/08 3/20/08 3/21/08 3/21/08 3/21/08 3/21/08 3/21/08 3/21/08 3/21/08 3/24/08 3/24/08 3/24/08 3/24/08 3/25/08 3/25/08 3/25/08 3/25/08 3/25/08 TEST LOCATION North PA 12 West PA 12 NEPA12 SWPA12 SWPA13 SWPA12 South PA 13 SWPA12 East PA 12 East PA 12 NEPA12 NEPA12 NEPA12 NEPA12 SWPA12 NNSPA12 Test Number Skipped NEPA12 NEPA12 North PA 12 NEPA12 North PA 13 North PA 13 NWPA13 North PA 13 NWPA13 SWPA13 SWPA12 West PA 13 Test Number Skipped Test Number Skipped NEPA12 SWPA13 PA 12 NEPA12 North PA 13 NWPA13 West PA 13 West PA 13 NEPA12 NEPA12 NEPA12 NEPA12 NEPA12 ELEV OR DEPTH (ft) 57.0 57.0 59.0 59.0 59.0 59.0 59.0 59.0 53.0 53.0 53.0 55.0 55.0 55.0 61.0 61.0 59.0 60.0 60.0 60.0 61.0 61.0 63.0 62.0 62.0 64.0 63.0 64.0 64.0 65.0 65.0 65.0 66.0 65.0 65.0 67.0 54.0 54.0 56.0 58.0 60.0 MOISTURE CONTENT (%) 23.9 14.7 13.5 15.3 21.6 22.9 21.7 13.9 14.5 15.5 13.7 21.8 22.6 21.5 25.7 25.2 14.5 15.2 15.0 22.4 21.8 14.7 13.5 15.3 12.1 13.8 14.7 14.5 13.8 15.8 23.7 22.8 14.4 13.5 13.7 16.0 11.1 11.8 13.8 11.8 11.0 DRY DENSITY (pcf) 92.3 107.5 106.6 106.8 93.2 91.9 92.4 107.2 106.9 106.5 107.7 91.8 92.3 91.9 92.0 92.4 107.2 108.2 107.4 92.1 92.3 117.3 115.4 118.2 115.8 107.2 108.2 107.4 106.9 106.5 92.0 91.9 106.5 106.8 107.0 107.5 107.4 115.8 106.8 114.5 112.5 REL COMP (%) 90.5 91.1 90.3 90.5 91.4 90.1 90.6 90.8 90.6 90.3 91.3 90.0 90.5 90.1 90.2 90.6 90.8 91.7 91.0 90.3 90.5 91.6 90.2 94.6 93.4 90.8 91.7 91.0 90.6 90.3 90.2 90.1 90.3 90.5 90.7 91.1 83.9 90.5 90.5 91.6 90.0 TEST METHOD SC ND ND ND SC ND ND ND SC ND ND ND SC ND ND ND SC ND ND ND SC ND ND ND SC ND ND ND SC ND ND ND ND ND ND ND ND ND ND ND ND SOIL TYPE E A A A E E E A A A A E E E E E A A A E E B B C D A A A A A E E A A A A B B A C C Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros GeoSoils, Inc. W.O. 5247-B1-SC June 2008 Page 6 Table 1 FIELD DENSITY TEST RESULTS TEST NO. 246 247 248 249 250 251 252 253 254 255 S-256 S-257 S-258 S-259 S-260 S-261 S-262 S-263 S-264 S-265 S-266 S-267 S-268 S-269 S-270 S-271 S-272 S-273 S-274 S-275 S-276 S-277 S-278 S-279 S-280 S-281 S-282 S-283 S-284* S-284A S-285 S-286 S-287 S-288 DATE 3/25/08 3/25/08 3/25/08 3/25/08 3/25/08 3/25/08 3/26/08 3/26/08 3/26/08 3/26/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/27/08 3/28/08 3/28/08 3/28/08 3/28/08 3/28/08 3/28/08 3/28/08 3/28/08 3/28/08 3/28/08 3/31/08 3/31/08 3/31/08 3/31/08 3/31/08 3/31/08 4/1/08 4/1/08 4/1/08 4/1/08 4/1/08 4/4/08 TEST LOCATION NEPA12 NEPA12 SWPA13 West PA 13 West PA 13 West PA 13 SEPA13 East PA 13 North PA 13 North PA 13 East PA 12 East PA 12 East PA 12 East PA 12 East PA 12 SEPA12 South PA 12 South PA 12 South PA 12 SWPA12 SWPA12 SWPA12 North PA 13 NWPA13 West PA 13 West PA 13 West PA 13 SWPA13 SWPA13 West PA 13 West PA 13 West PA 13 West PA 13 SWPA12 SWPA12 SWPA12 PA 12 PA 12 West PA 12 West PA 12 West PA 12 West PA 12 West PA 12 West PA 12 ELEV OR DEPTH (ft) 62.0 64.0 63.0 65.0 67.0 69.0 65.0 67.0 69.0 70.0 60.0 58.0 56.0 54.0 52.0 50.0 48.0 46.0 44.0 42.0 40.0 38.0 75.0 70.0 68.0 66.0 65.0 63.0 60.0 58.0 55.0 52.0 60.0 58.0 54.0 50.0 46.0 42.0 54.0 54.0 52.0 50.0 48.0 46.0 MOISTURE CONTENT (%) 14.2 13.8 22.5 25.4 13.9 21.5 11.1 13.8 11.8 11.0 14.2 13.5 15.3 14.1 12.1 11.3 10.5 10.9 10.3 12.1 14.5 11.7 11.6 12.7 13.6 13.7 14.0 13.8 11.0 11.5 11.2 11.1 14.7 13.9 13.6 14.0 10.1 10.0 11.6 11.9 13.5 14.0 12.1 21.5 DRY DENSITY (pcf) 108.9 107.5 93.0 91.9 107.0 91.8 107.8 107.0 91.9 91.8 106.8 106.5 107.2 106.6 115.2 114.7 115.2 115.7 115.9 113.4 106.8 114.5 112.7 112.9 107.1 106.8 106.4 107.1 115.3 111.6 112.9 113.2 107.0 106.8 108.0 107.5 116.8 115.6 114.5 115.8 106.8 107.0 113.8 92.1 REL COMP (%) 92.3 91.1 91.4 90.1 90.7 90.0 91.4 90.7 90.1 90.0 90.5 90.3 90.8 90.3 92.2 91.8 90.0 90.4 90.5 90.7 90.5 91.6 90.2 90.3 90.8 90.5 90.2 90.8 90.1 90.0 90.3 90.6 90.7 90.5 91.5 91.1 91.3 90.3 89.5 90.5 90.5 90.7 91.0 90.3 TEST METHOD ND ND SC ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND SOIL TYPE A A E E A E A A E E A A A A C C B B B C A C C C A A A A B D C C A A A A B B B B A A C E Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros W.O. 5247-B1-SC June 2008 Page 7 GeoSoils, Inc. Table 1 FIELD DENSITY TEST RESULTS TEST NO. S-289 290 291 S-292 S-293 DATE 4/4/08 5/9/08 5/9/08 5/9/08 5/9/08 TEST LOCATION West PA 12 NEPA12 NWPA13 PA 12 PA 12 ELEV OR DEPTH (ft) 47.0 63.0 67.5 48.0 55.0 MOISTURE CONTENT (%) 22.4 13.7 21.6 14.7 14.8 DRY DENSITY (Prf) 91.9 107.1 92.1 106.4 106.7 REL COMP (%) 90.1 90.7 90.3 90.2 90.4 TEST METHOD ND ND ND ND ND SOIL TYPE E A E A A LEGEND: 1 = Repeated Test Number * = Failed Test A = Retest ND = Nuclear Densometer NE = North East NW = North West S = Slope Test SC = Sand Cone SE = South East SW = South West Robertson Family Trust PA-12 and PA-13, Robertson Ranch West File: C:\excel\tables\5200\5247b1 .ros GeoSoils, Inc. W.O. 5247-B1-SC June 2008 PageS APPENDIX REFERENCES APPENDIX REFERENCES Bryant, W.A., and Hart, E.W., 2007, Fault-rupture hazard zones in California, Alquist-Priolo earthquake fault zoning act with index to earthquake fault zones maps; California Geological Survey, Special Publication 42, interim revision. California Building Standards Commission, 2007, California building code. Chen, Y., Chen, W., Wang, Y., Lo, T., Lui, T., and Lee, J., 2002, Geomorphic evidence for prior earthquakes: lessons from the 1999 Chichi earthquake in central Taiwan, in Geological Society of America, Geology, v. 30, no. 2. pp. 171-174. Dietrich, W.E., and Dorn, R., 1984, Significance of thick deposits of colluvium on hillslopes: A case study in the coastal mountains of northern California, Journal of Geology, v. 92, p. 133-146. GeoSoils, Inc., 2008, Interim report of rough grading, Planning Area 14 of Robertson Ranch East Village, City of Carlsbad, California, W.O. 5353-B-SC, dated May 20. , 2007a, Report of rough grading, Planning Area 15 of Robertson Ranch, East Village, Carlsbad Site Development Plan 06-04, Drawing 450-6A, Carlsbad, San Diego County, California, W.O. 5353-B-SC, dated November 9. 2007b, Compaction report of geotechnical observation and testing services, 84-inch storm drain improvements for Cannon Road, Robertson Ranch East Village, Carlsbad, San Diego County, California, W.O. 5355-D-SC, dated August 16. ,2007c, Preliminary geotechnical evaluation, Planning Area 12 (13.44 Acres), and Planning Area 13 (6.92 Acres), Robertson Ranch West, Carlsbad, San Diego County, California 92010, City of Carlsbad Planning Department Application No. SUP 06-12/HDP 06-04, W.O. 5247-A-SC, dated January 31. 2004, Updated geotechnical evaluation of the Robertson Ranch property, Carlsbad, San Diego County, California, W.O. 3098-A2-SC, dated September 20. , 2002, Geotechnical evaluation of the Robertson Ranch property, City of Carlsbad, San Diego County, California, W.O. 3098-A1-SC, dated January 29. International Code Council, Inc., 2006, International building code and international residential code for one- and two-family dwellings. International Conference of Building Officials, 2001, California building code, California code of regulations title 24, part 2, volume 1 and 2. GeoSoils, Inc. , 1997, Uniform building code: Whittier, California, International conference of building officials, Volumes 1, 2, and 3: especially Chapter 16, Structural forces (earthquake provisions); Chapter 18, Foundations and retaining walls; and Chapter A-33, Excavation and grading. Kanare, Howard, M., 2005, Concrete Floors and Moisture, Engineering Bulletin 119, Portland Cement Association. McCalpin, J.P., 1996, Paleoseismology in extensional tectonic environments, chapter 3, in McCalpin, J.P., ed., Paleoseismology, Academic Press, Inc., San Diego, California. O'Day Consultants, 2006, Grading plans for Robertson Ranch Future PA 12 and PA 13, Sheet 1 through 6, Job no. 01-1014, dated October. Shlemon, R.J., Wright, R.H., and Montgomery, D.R., 1987, Anatomy of a debris flow, Pacifica, California; Geological Society of America, in Reviews in engineering geology, volume VII, Debris flows/avalanches: process, recognition, and mitigation, p. 181-199. State of California, 2006, Civil Code, Sections 895 et seq. Suppe, J., 1985, Principals of structural geology, Prentice-Hall, New York. , 1983, Geometry and kinematics of fault-bend folding. Am. J. Sci 283, 684-721. United States Department of Agriculture, 1953, Aerial photographs, flight date April 11, flight No. AXN-8M, photos nos. 69, 70, 102, and 103, scale 1"=2,000'±. Weldon, R.J., McCalpin, J.P., and Rockwell, T.K., 1996, chapter 6, Paleoseismology in strike-slip tectonic environments, in McCalpin, J.P., ed., Paleoseismology, Academic Press, Inc., San Diego, California. Robertson Family Trust Appendix File:e:\wp9\5200\5247b1 .ros Page 2 GeoSoils, Inc.