Loading...
HomeMy WebLinkAboutCDP 12-02; MAGNOLIA AVENUE RESIDENCE 2; PROJECT GRADING REPORT; 2012-06-08I ADVANCED GEOTECHNICAL. SOLUTIONS, INC. I 25109 Jefferson Avenue, Suite 220 Murrieta, California 92562 (C O)AGS Telephone: (619) 708-1649 Fax: (714) 409-3287 NEW POINTE COMMUNITIES, INC. June 8, 2012 16880 West Bernardo Drive, Suite 230 P1W 1201-02 San Diego, CA 92127 Report No. 1201-02-C-4 Attention: Mr. Scot Sandstrom Subject: Project Grading Report, Proposed Single-Family Residences, Parcel 2 (1373 Magnolia Avenue) and Parcel 3 (1377 Magnolia Avenue), Carlsbad, California References: 1) Foundation Design Review Letter, Proposed Single Family Residences, Pci 2 (13 73 Magnolia Ave) and Pcl 3 (13 77 Magnolia Ave), Carlsbad, California, prepared by Advanced Geotechnical Solutions, Inc., dated April 11, 2012 (Report No. 1201-02-B-3). 2) Geotechnical Investigation and Foundation Design Recommendations for Proposed Single-Family Residences, Parcel 2 and 3, 1369 Magnolia Avenue, Carlsbad, California, prepared by Advanced Geotechnical Solutions, Inc., dated March 21, 2012 (Report No. 1201-02-B-2). Gentlemen: In accordance with your request and authorization, Advanced Geotechnical Solutions, Inc. (AGS), presents herein our observations and test results pertaining to the recently completed grading of the subject residential lots, Parcel 2 (1373 Magnolia Avenue) and Parcel 3 (1377 Magnolia Avenue) Carlsbad, California. Based on the results of the testing and observations by representatives of AGS, the work described herein is considered to be in general conformance with City of Carlsbad Grading Code and the recommendations presented in the referenced geotechnical report. This report addresses grading operations aimed at attaining rough grades for the subject lots as reflected on the 20-Scale Grading and Erosion Control Plan (Sheet 2 of 3) prepared by Barger Engineering. Rough grading for the subject site was conducted in May and June, 2012. Soil engineering observations collected during rough grading are summarized in the text of this report and the developed data are presented in Table I. The approximate locations of compaction tests and limits of fill under the purview of this report are shown on the accompanying Plate 1, Compaction Test Location Plan. 1.0 GEOLOGY A brief description of the earth materials encountered on this site is presented in the following sections. Based on our observations during the recent grading, site reconnaissance, subsurface excavations, and review of geologic maps, the site is underlain to the depths explored by old paralic deposits (terrace deposits) which are locally overlain by a thin veneer of artificial fill and topsoil. June 8, 2012 Page 2 P1W 1201-02 Report No. 1201-02-C-4 1.1. Topsoil/Artificial Fill (Undifferentiated) Undifferentiated topsoil/artificial fill soils were encountered in both onsite excavations and encountered during site grading. These soils were of variable thickness, ranging from approximately two to four feet. As encountered, these materials generally consisted of light gray brown to reddish brown, moist, loose, silty to clayey fine- to medium-grained sand. 1.2. Old Paralic Deposits The site is underlain to maximum depth explored by Old Paralic Deposits. These materials can generally be described as mottled gray brown to reddish brown, slightly moist to moist, medium dense to dense, silty fine to medium grained sand. I 1.3. Groundwater Groundwater was not encountered in our exploratory excavations or during grading of the site. No natural groundwater condition is known to exist at the site that would impact the proposed site development. Although unlikely, localized perched groundwater could develop at a later date, most likely at or near fill/bedrock contacts, due to fluctuations in precipitation, irrigation practices, or factors not evident at the time of our field work. I 2.0 GRADING Presented herein is a summary of observations collected during grading. The subject site has been vacant and supported a light to heavy growth of seasonal vegetation. Prior to the commencement of grading I operations, all onsite surface vegetation within the proposed building and driveway areas was removed from the site. I Based on AGS's referenced geotechnical report, it was concluded that remediation of the upper surface soils would be required during site grading operations to provide suitable building pads. Presented herein is a summary of the removal and fill placement operations. 2.1. Unsuitable Soil Removals Grading for the subject lot consisted of fine grading of the lot to the design grade I depicted on the 20-Scale Grading and Erosion Control Plan (Sheet 2 of 3) prepared by Barger Engineering. Prior to placing any fill on the site, the dry, loose, and compressible I preexisting artificial fill and highly weathered native soils were removed. Removal limits extended horizontally a minimum of five feet outside the structural footprint of the proposed residential structures. Removal depths within the limits of the subject site were I approximately two to four feet below the previously existing grades. The maximum depth of fill under the purview of this report is approximately seven feet. I 2.2. Compaction Operations The excavation bottoms were observed by a representative of this firm after the completion of removals. The exposed removal bottoms were then scarified to an ADVANCED GEOTECHNICAL. SOLUTIONS, INC. June 8,2012 Page P1W 1201-02 Report No. 1201-02-C-4 approximate depth of 6 to 8 inches, brought to above optimum moisture content and compacted in-place to a minimum of 90 percent of the laboratory maximum dry density in accordance with ASTM Test Method D-1557. Fill materials, consisting of the soil types summarized in Table 1, were then placed in thin, loose, lifts (approximately 8 inches), brought to slightly above optimum moisture content, and compacted to a minimum of 90 percent of the laboratory maximum dry density in accordance with ASTM Test Method D-1557. Compaction was achieved by equipment wheel rolling. Compaction tests were taken during the course of grading for every one to two feet of fill placed. A summary of compaction tests pertaining to grading within the subject lots is presented in Table I. The approximate locations of these tests are shown on the accompanying plan (Plate 1). 3.0 DESIGN RECOMMENDATIONS Based on AGS's recent observations and review of the referenced report, the lots are considered suitable for support of the proposed single-family residences. From a geotechnical viewpoint, the proposed structures for the subject lots can be constructed at this time. The foundations for the subject lots should be constructed in general conformance with the recommendations presented in the referenced report and the following. 3.1. Expansion Potential As part of our referenced geotechnical investigation, representative bulk samples of near surface soils were collected and tested to evaluate their potential for expansion. Testing was performed in general accordance with ASTM D 4829. Test results indicate that the soils tested possess an expansion index (El) of 34, which corresponds to a "Low" expansion potential. • 3.2. Foundation Design Criteria The proposed single-family residential structures can be supported on conventional I shallow, slab-on-grade foundation systems. The expansion potential of the underlying soils is classified as "Low". I The following values may be used in the foundation design. Allowable Bearing: 2000 lbs./sq.ft. Lateral Bearing: 250 lbs./sq.ft. at a depth of 12 inches plus I 125 lbs./sq.ft. for each additional 12 inches embedment to a maximum of 2000 lbs./sq.ft. Sliding Coefficient: 0.33 Settlement: Total = 3/4 inch Differential: 3/8 inch in 20 feet I ADVANCED GEOTECHNICAL. SOLUTIONS, INC. I June 8, 2012 Page 4 P1W 1201-02 Report No. 1201-02-C-4 3.3. Seismic Design Criteria I The following seismic design parameters are presented to be code compliant to the California Building Code (2010). The subject lots have been identified to be site class "D" in accordance I with CBC,.2010, Table 1613.5.3 (1). The lots are located at Latitude 33.15682 N and Longitude 117.33252° W. Utilizing this information, the computer program USGS Earthquake Ground Motion Parameters Version 5.1.0 and ASCE 7 criterion, the seismic design category for 0.20 I seconds (Ss) and 1.0 second (S1 ) period response accelerations can be determined (CBC, 2010 1613.5.5.1) along with the design spectral response acceleration (CBC, 2010 1613.5.4). Seismic Design Criteria Mapped Spectral Acceleration (0.2 sec Period), Ss 1.275g Mapped Spectral Acceleration (1.0 sec Period), S1 0.480g Site Coefficient, Fa 1.0 Site Coefficient, F 1.52 MCE Spectral Response Acceleration (0.2 sec Period), SMs 1.275g MCE Spectral Response Acceleration (1.0 sec Period), SM1 0.730g Design Spectral Response Acceleration (0.2 sec Period), SD5 0.850g Design Spectral Response Acceleration (1:0 sec Period), SDI 0.487g I - 3.4. Conventional Foundation Desum Parameters I Based upon the onsite soil conditions and information supplied by the CBC-2010, conventional foundation systems should be designed in accordance with Section 8.2.1 and the following recommendations: I > Two-story - Interior and exterior footings should be a minimum of 15 inches wide and extend to a depth of at least 18 inches below lowest adjacent grade. Footing I reinforcement should minimally consist of four No. 4 reinforcing bars, two top and two bottom or two No. 5 reinforcing bars, one top and one bottom. Slab - Conventional, slab-on-grade floors, underlain by "low" expansive I compacted fill, should be five or more inches thick and be reinforced with No. 3 or larger reinforcing bars spaced 18 inches on center each way. The slab reinforcement and I expansion joint spacing should be designed by the Structural Engineer. Embedment - If exterior footings adjacent to drainage swales are to exist within five feet horizontally of the swale, the footing should be embedded sufficiently to assure I embedment below the swale bottom is maintained. Footings adjacent to slopes should be embedded such that a least seven feet are provided horizontally from edge of the footing a to the face of the slope. ADVANCED GEOTECHNICAL SOLUTIONS, INC. 1 I Ii I I June 8, 2012 Page 5 P1W 1201-02 Report No. 1201-02-C-4 > Garage - A grade beam reinforced continuously with the garage footings shall be I constructed across the garage entrance, tying together the ends of the perimeter footings and between individual spread footings. This grade beam should be embedded at the same depth as the adjacent perimeter footings. A thickened slab, separated by a cold I joint from the garage beam, should be provided at the garage entrance. Minimum dimensions of the thickened edge shall be six (6) inches deep. Footing depth, width and I reinforcement should be the same as the structure. Slab thickness, reinforcement and under-slab treatment should be the same as the structure. Isolated Spread Footings - Isolated spread footings should be embedded a I minimum of 18 inches below lowest adjacent finish grade and should at least 24 inches wide. A grade beam should also be constructed for interior and exterior spread footings and should be tied into the structure in two orthogonal directions footing dimensions and I reinforcement should be similar to the aforementioned continuous footing recommendations. Final depth, width and reinforcement should be determined by the I structural engineer. 3.5. Under Slab I Prior to concrete placement the subgrade soils should be moisture conditioned to at least optimum moisture content. I A moisture and vapor retarding system should be placed below the slabs-on-grade in portions of the structure considered to be moisture sensitive. The retarder should be of suitable composition, thickness, strength and low permeance to effectively prevent the I migration of water and reduce the transmission of water vapor to acceptable levels. Historically, a lO-mil plastic membrane, such as Vis queen, placed between one to four inches of clean sand, has been used for this purpose. More recently Stego® Wrap or I similar underlayments have been used to lower permeance to effectively prevent the migration of water and reduce the transmission of water vapor to acceptable levels. The use of this system or other systems, materials or techniques can be considered, at the I discretion of the designer, provided the system reduces the vapor transmission rates to acceptable levels. I 3.6. Deepened Footings and Structural Setbacks It is generally recognized that improvements constructed in proximity to natural slopes or I properly constructed, manufactured slopes can, over a period of time, be affected by natural processes including gravity forces, weathering of surficial soils and long-term (secondary) settlement. Most building codes, including the California Building Code I (CBC), require that structures be set back or footings deepened, where subject to the influence of these natural processes. For the subject site, where foundations for residential structures are to exist in proximity I to slopes, the footings should be embedded to satisfy the requirements presented in Figure 1. I ADVANCED GEOTECHNICAI.. SOUJT1ONS, INC. June 8, 2012 Page 6 P/W 1201-02 Report No. 1201-02-C-4 FIGURE 1 FACE OF FOOTING TOP OF SLOPE FACE OF STRUCTURE TOE OF H/3 BUT NEED NOT EXCEED 40 FT. H MAX. Ht2 'BUT NEED NOT EXCEED 15 Vf. MAX. 3.7. Concrete Design It is anticipated that the onsite soils will exhibit a "negligible" sulfate exposure when classified in accordance with ACT 318-05 Table 4.3.1 (per 2010 CBC). However, some fertilizers have been known to leach sulfates into soils otherwise containing "negligible" sulfate concentrations and increase the sulfate concentrations to potentially detrimental levels. It is incumbent upon the owner to determine whether additional protective measures are warranted to mitigate the potential for increased sulfate concentrations to onsite soils as a result of the future homeowner's actions. 3.8. Chemical/Resistivity Testin Resistivity tests performed indicate that the onsite soils are "moderately" corrosive to buried metallic materials. AGS recommends minimally that the current standard of care be employed for protection of metallic construction materials in contact with onsite soils or that consultation with an engineer specializing in corrosion to determine specifications for protection of the construction materials. 3.9. Retaining Walls The following earth pressures are recommended for the design of retaining walls onsite: Rankine Equivalent Fluid Level Backfill Coefficients Pressure (psf/lin.ft.) Coefficient of Active Pressure: Ka = 0.36 45 Coefficient of Passive Pressure: K = 2.77 346 Coefficient of at Rest Pressure: Ko = 0.53 66 ADVANCED GEOTECIINICAL SOLUTIONS, INC. I June 8, 2012 Page 7 1 P/W 1201-02 Report No. 1201-02-C-4 I Rankine Equivalent Fluid 2: 1 Backfill Coefficients Pressure (psf/lin.ft.) Coefficient of Active Pressure: Ka = 0.75 79 I Coefficient of Passive Pressure: Descending K (-) = 0.99 124 Coefficient of At Rest Pressure: K0 = 0.92 116 The foundations for retaining walls of appurtenant structures structurally separated from the building structure may bear on properly compacted fill. A bearing value of 2,000 psf may be used for design of retaining walls. Retaining wall footings should be designed to resist the lateral forces by passive soil resistance and/or base friction as recommended for foundation lateral resistance. To minimize the potential for hydrostatic pressure, wall backfill should consist of a free draining backfill (sand equivalent "SE" >20) and a heel drain should be constructed. The heel drain should be place at the heel of the wall and should consist of a 4-inch diameter perforated pipe (5DR35 or SCHD 40) surrounded by 4 cubic feet of crushed rock (3/4-inch) per lineal foot wrapped in filter fabric (with similar properties to Mirafi 140N or equivalent). Proper drainage devices should be installed along the top of the wall backfill and should properly sloped to prevent surface water ponding adjacent to the wall. In addition to the wall drainage system, the wall should be waterproofed and/or damp-proofed to effectively seal the wall from moisture infiltration through the wall face. The wall should be backfilled with granular soils placed in loose lifts no greater than 8- inches thick, at or near optimum moisture content, and mechanically compacted to a minimum 90 percent relative compaction as determined by ASTM Test Method D1557. Flooding or jetting of backfill materials generally do not result in the required degree and uniformity of compaction and, therefore, is not recommended. The soils engineer or his representative should observe the retaining wall footings, backdrain installation and be present during placement of the wall backfill to confirm that the walls are properly backfilled and compacted. ADVANCED GE01ECHNICAL. SOLUTIONS, INC. June 8, 2012 Page 8 P1W 1201-02 Report No. 1201-02-C-4 I WATERPROOFING ROVI I MEMBRANE DRAINAGE (OPTIONAL) \ SWUE IDS \ / 12in. NATIVE I 8ACKFILL i mm. (EK50) I ! SELECT I . BI4CKFILL . (E1<20& . SE) •I 11/2 mht 1:1(H:V)ORFLATTER ORAIN (I) I - , _ I INOTEI& (1) 44nCH 'toas oi vc soovm SUtlflItE PLACED PERPOPAnOM DIZVNANDSURROUNDED 6YA MN IMUN OF QJ3$C FEET OF 3t4 INCH ROCKOR APPROVED EO1.$VME41 SUSS1111IIEANO W1WO IN P4IRAF4 i40 FIL1R FAEIRC OR APIOVEI) OthUNT5USS11TUtI 3.10. Utility Trench Excavation I All utility trenches should be shored or laid back in accordance with applicable Cal/OSHA standards. Excavations in bedrock areas should be made in consideration of I underlying geologic structure. AGS should be consulted on these issues during construction. I 3.11. Utility Trench Backfill Mainline and lateral utility trench backfill should be compacted to at least 90 percent of maximum dry density as determined by ASTM: D-1557. Onsite soils may not be suitable I for use as bedding material but will be suitable for use in backfill, provided oversized materials are removed. No surcharge loads should be imposed above excavations. This I includes spoil piles, lumber, concrete trucks or other construction materials and equipment. Drainage above excavations should be directed away from the banks. Care should be taken to avoid saturation of the soils. I Compaction should be accomplished by mechanical means. Jetting of native soils will not be acceptable. ~ I ADVANCED GEOTECIINICAL. SOLUTIONS, INC. Li June 8, 2012 Page 9 1 P1W 1201-02 Report No. 1201-02-C-4 3.12. Exterior Slabs and Walkways 3.12.1. Subgrade Compaction The subgrade below exterior slabs, sidewalks, driveways, patios, etc. should be compacted to a minimum of 90 percent relative compaction as determined by ASTM Test Method: D 1557. I 3.12.2. Subgrade Moisture The subgrade below exterior slabs, sidewalks, driveways, patios, etc. should be moisture I conditioned to a minimum of 110 percent of optimum moisture content prior to concrete placement. I 3.123. Slab Thickness Concrete flatwork and driveways should be designed utilizing four-inch minimum thickness. 3.12.4. Control Joints Weakened plane joints should be installed on walkways at intervals of approximately eight to ten feet. Exterior slabs should be designed to withstand shrinkage of the concrete. 3.12.5. Flatwork Reinforcement Consideration should be given to reinforcing any exterior flatwork. 3.12.6. Thickened Edge Consideration should be given to construct a thickened edge (scoop footing) at the perimeter of slabs and walkways adjacent to landscape areas to minimize moisture variation below these improvements. The thickened edge (scoop footing) should extend approximately eight inches below concrete slabs and should be a minimum of six inches wide. ADVANCED GEOTECIINICAL SOLUTIONS, INC. - j AL Advanced Geotechnical Solutions, Iic--,. -----.... PAUL J. DERISI, Vice President CEG 2536, Reg. Exp. 5-31-13 Distribution: (6) Addressee UEQç 0/0.2536 '\) r( CERTIFIED \—i ENGINEERING GEOL GIST • EXP 1(3 OF c'-\' June 8, 2012 Page 10 P1W 1201-02 Report No. 1201-02-C-4 4.0 LIMITATIONS This report presents information and data relative to onsite construction operations for the subject site. A representative(s) of this firm probed and tested at random locations in an effort to determine whether compliance with the project compaction, specifications, and applicable Building Code was being obtained. The presence of our personnel during testing operations does not involve any supervision or direction of the contractor or his work forces. The opportunity to be of service is sincerely appreciated. if you should have any questions, please do not hesitate to contact the undersigned. Rpcnej'i11v Submitted Attachments: Table 1 (Compaction Test Table) Plate 1 (Compaction Test Location Plan) Appendix A-Homeowners Maintenance Guidelines ADVANCED GE01ECHNICAL SOLUTIONS, INC. - - - - - - - - - - - - - - - - - - - I 107 LF "8 PVC 0% MIN I - - - I 152.51 154 ~7,7 F~ qwm PCL 31 '54 1 ISTNGPER COP O18 F 2% 106 GROSS AREA= 14,551 SF - 0 FF= I ~7.50 L 0 PAD= 155.50 114 107 11 103 101 l --156 13 k 105 '— H ' i L —I54---11 N266'40W lU8.49' 153 _ _ NnL58- 352 54 15Z5 13.'5' 288.59' 7- -'T- -rV1 H EXISTING 2O528 6 SPLIT FACE WALL 7 5' 3' VEGETATED SPLIT FACE WALL F(QRATIVE_CAP SWALE w/_DFCQRAI1VF CAP, LEGEND: PLATE I S Approximate location of field 115 Compaction Test Location Plan density test EE149.5 Approximate elevation of removal bottom (0)AGS Approximate limits of grading DA nuT,' SCALE under purview of report WktiIL11 Al AL SOLUTIONS, INC. Project: Report: Date: P/W1201.021201-02-C-461812012 NOTE: BASE MAP TAKEN FROM 20-SCALE GRADING AND EROSION CONTROL PLANS FOR 1369 20' 0 10' 20' 'W,80' II MAGNOLIAAVENUE, SHEET 2 OF 3, DWG. NO. 472-5A, PREPARED BY BARGER ENGINEERING June 8, 2012 SUMMARY OF LABORATORY Page 1 of Table 1 P1W 1201-02 MAXIMUM DRY DENSITY AND Report No. 1201-02-C-4 OPTIMUM MOISTURE CONTENT TABLE 1 OPTIMUM MAXIMUM MOISTURE DRY CONTENT DENSITY SOIL TYPE DESCRIPTION (%) (pcf) A Brown Silty Sand 9.5 124.5 B Reddish Brown Silty Sand 8.5 129 1201-02-C4 Magnolia Ave Compaction Tests - Table 1/Max Table ADVANCED GEOTECIINICAI.. SOLUTIONS, INC. June 8, 2012 FIELD DENSITY TEST RESULTS Page 2 of Table 1 P1W 1201-02 TABLE 1 (contd) Report No. 1201-02-C-4 TEST NUMBER/LOCATION/ELEVATION KEY S - Sewer Trench I - Irrigation Trench SD - Storm Drain Trench E - Electrical Trench iT - Joint Utility Trench W - Water Trench RTW - Retaining Wall FTG - Footing FG - Finish Grade SG - Subgrade CG - Curb and Gutter Subgrade B - Base AC - Asphalt Concrete Finish Grade BC - Asphalt Concrete Base Course CC - Asphalt Concrete Cap Course -R,R1,R2 - Indicates Retest * Rock Correction- Estimated Percent Retained on #4 Sieve (Method A) or 3/4 inch (Method C), Maximum Dry Density and Optimum Moisture Content adjusted per ASTM D 4718 Date Test Number Location Depth or Elev. Soil Type Rock Corr.* Moisture (%) Dry Density (pd) Rel. Comp. (%) Proj. Spec. (%) Test Type (S/N) Pass or Fail Opt. Field Max. Field 5/30/12 101 Parcel 2 153.5 B 15 7.2 7.3 133.5 128.5 96 90 N Pass 5/30/12 102 Parcel 2 154.5 A 5 9.0 9.1 126.1 121.3 96 90 N Pass 5/30/12 103 Parcel 2 155 A 5 9.0 9.4 126.1 120.4 95 90 N Pass 5/31/12 104 Parcel 3 152 A 0 9.5 97 124.5 119.3 95 90 N Pass 5/31/12 105 Parcel 3 153.5 B 0 8.5 8.9 129.0 124.5 96 90 N Pass 5/31/12 106 Parcel 3 155 B 0 8.5 9.3 129.0 121.7 94 90 N Pass 5/31/12 107 Parcel 3 156.5 B 0 8.5 9.7 129.0 120.8 93 90 N Pass 6/1/12 108 Driveway 150 A 0 9.5 10.3 124.5 119.1 95 90 N Pass 6/1/12 109 Driveway 150.5 A 0 9.5 9.9 124.5 119.9 96 90 N Pass 6/1/12 110 Driveway 151 B 0 8.5 8.7 129.0 120.4 93 90 N Pass 6/1/12 iii Driveway 153 B 0 8.5 8.9 129.0 121.3 94 90 N Pass 6/4/12 112 Driveway 152.5 B 0 8.5 10.1 129.0 120.6 93 90 N Pass 6/4/12 113 Driveway 155 B 0 8.5 9.8 129.0 122.8 95 90 N Pass 6/5/12 114 Parcel 2 FG B 0 8.5 9.7 129.0 120.9 93 90 N Pass 6/5/12 115 Parcel 3 FG B 0 8.5 9.0 129.0 122.2 94 90 1N Pass 1201-02-C4 Magnolia Ave Compaction Tests - Table i ADVANCED GEOTECIINICAL. SOLUTIONS, INC. - - - - - - - - - - - - - - - - - - - June 8, 2012 Page 11 P/W 1201-02 Report No. 1201-02-C-4 APPENDIX A HOMEOWNERS MAINTENANCE GUIDELINES ADVANCED GEOTECHNICAL. SOU.JTIONS, INC. I I HOMEOWNERS MAINTENANCE GUIDELINES I Homeowners are accustomed to maintaining their homes. They expect to paint their houses periodically, replace wiring, clean out clogged plumbing, and repair roofs. Maintenance of the home site, particularly on hillsides, should be considered on the same basis, or even on a more serious basis because neglect can result in serious consequences. In most cases, lot and site maintenance I can be taken care of along with landscaping, and can be carried out more economically than repair after neglect. Most slope and hillside lot problems are associated with water. Uncontrolled water from a broken pipe, cesspool, or wet weather causes most damage. Wet weather is the largest cause of slope problems, particularly in California where rain is intermittent, but I may be torrential. Therefore, drainage and erosion control are the most important aspects of home site stability; these provisions must not be altered without competent professional advice. Further, maintenance must be carried out to assure their continued operation. As geotechnical engineers concerned with the problems of building sites in hillside developments, we offer the following list of recommended home protection measures as a guide to homeowners. Expansive Soils I Some of the earth materials on site have been identified as being expansive in nature. As such, these materials are susceptible to volume changes with variations in their moisture content. These soils will swell upon the introduction of water and shrink upon drying. The forces associated with these volume changes can have significant negative impacts (in the form of differential movement) on foundations, walkways, patios, and other lot improvements. In recognition of this, the project developer has I constructed homes on these lots on post-tensioned or mat slabs with pier and grade beam foundation systems, intended to help reduce the potential adverse effects of these expansive materials on the residential structures within the project. Such foundation systems are not intended to offset the forces (and associated movement) related to expansive soil, but are intended to help soften their effects on the structures constructed thereon. I Homeowners purchasing property and living in an area containing expansive soils must assume a certain degree of responsibility for homeowner improvements as well as for maintaining conditions around their home. Provisions should be incorporated into the design and construction of homeowner improvements to account for the expansive nature of the onsite soils material. Lot maintenance and landscaping should also be conducted in consideration of the expansive soil characteristics. Of primary I importance is minimizing the moisture variation below all lot improvements. Such design, construction and homeowner maintenance provisions should include: + Employing contractors for homeowner improvements who design and build in recognition of local building code and I site specific soils conditions. + Establishing and maintaining positive drainage away from all foundations, walkways, driveways, patios, and other hardscape improvements. I •• Avoiding the construction of planters adjacent to structural improvements. Alternatively, planter sides/bottoms can be sealed with an impermeable membrane and drained away from the improvements via subdrains into approved disposal areas. I + Sealing and maintaining construction/control joints within concrete slabs and walkways to reduce the potential for moisture infiltration into the subgrade soils. Utilizing landscaping schemes with vegetation that requires minimal watering. Alternatively, watering should be done I in a uniform manner as equally as possible on all sides of the foundation, keeping the soil "moist" but not allowing the soil to become saturated. + Maintaining positive drainage away from structures and providing roof gutters on all structures with downspouts I installed to carry roof runoff directly into area drains or discharged well away from the structures. •• Avoiding the placement of trees closer to the proposed structures than a distance of one-half the mature height of the tree. I + Observation of the soil conditions around the perimeter of the structure during extremely hot/dry or unusually wet weather conditions so that modifications can be made in irrigation programs to maintain relatively constant moisture conditions. Sulfates I On site soils were tested for the presence of soluble sulfates. Based on the results of that testing, the soluble sulfate exposure levels of the onsite soils were determined to be "negligible" when classified in accordance with the AC! 318-05 Table 4.3.1 (per 2009 CBC). 1 ORANGE AND L.A. COUNTIES INLAND EMPIRE SAN DIEGO AND IMPERIAL COUNTIES (714)786-5661 (619)708-1649 (619)850-3980 Homeowners should be cautioned against the import and use of certain fertilizers, soil amendments, and/or other soils from offsite sources in the absence of specific information relating to their chemical composition. Some fertilizers have been known to leach sulfate compounds into soils otherwise containing "negligible" sulfate concentrations and increase the sulfate concentrations in near-surface soils to "moderate" or "severe" levels. In some cases, concrete improvements constructed in soils containing high levels of soluble sulfates may be affected by deterioration and loss of strength. Water - Natural and Man Induced Water in concert with the reaction of various natural and man-made elements, can cause detrimental effects to your structure and surrounding property. Rain water and flowing water erodes and saturates the ground and changes the engineering characteristics of the underlying earth materials upon saturation. Excessive irrigation in concert with a rainy period is commonly associated with shallow slope failures and deep seated landslides, saturation of near structure soils, local ponding of water, and transportation of water soluble substances that are deleterious to building materials including concrete, steel, wood, and stucco. Water interacting with the near surface and subsurface soils can initiate several other potentially detrimental phenomena other then slope stability issues. These may include expansion/contraction cycles, liquefaction potential increase, hydro-collapse of soils, ground surface settlement, earth material consolidation, and introduction of deleterious substances. The homeowners should be made aware of the potential problems which may develop when drainage is altered through construction of retaining walls, swimming pools, paved walkways and patios. Ponded water, drainage over the slope face, leaking irrigation systems, over-watering or other conditions which could lead to ground saturation must be avoided. ) Before the rainy season arrives, check and clear roof drains, gutters and down spouts of all accumulated debris. Roof gutters are an important element in your arsenal against rain damage. If you do not have roof gutters and down spouts, you may elect to install them. Roofs, with their, wide, flat area can shed tremendous quantities of water. Without gutters or other adequate drainage, water falling from the eaves collects against foundation and basement walls. •• Make sure to clear surface and terrace drainage ditches, and check them frequently during the rainy season. This task is a community responsibility. •• Test all drainage ditches for functioning outlet drains. This should be tested with a hose and done before the rainy season. All blockages should be removed. 9 Check all drains at top of slopes to be sure they are clear and that water will not overflow the slope itself, causing erosion. + Keep subsurface drain openings (weep-holes) clear of debris and other material which could block them in a storm. + Check for loose fill above and below your property if you live on a slope or terrace. + Monitor hoses and sprinklers. During the rainy season, little, if any, irrigation is required. Oversaturation of the ground is unnecessary, increases watering costs, and can cause subsurface drainage. + Watch for water backup of drains inside the house and toilets during the rainy season, as this may indicate drain or sewer blockage. •• Never block terrace drains and brow ditches on slopes or at the tops of cut or fill slopes. These are designed to carry away runoff to a place where it can be safely distributed. •• Maintain the ground surface upslope of lined ditches to ensure that surface water is collected in the ditch and is not permitted to be trapped behind or under the lining. Do not permit water to collect or pond on your home site. Water gathering here will tend to either seep into the ground (loosening or expanding fill or natural ground), or will overflow into the slope and begin erosion. Once erosion is started, it is difficult to control and severe damage may result rather quickly. I 9 Never connect roof drains, gutters, or down spouts to subsurface drains. Rather, arrange them so that water either flows off your property in a specially designed pipe or flows out into a paved driveway or street. The water then may be dissipated over a wide surface or, preferably, may be carried away in a paved gutter or storm drain. Subdrains are constructed to take care of ordinary subsurface water and cannot handle the overload from roofs during a heavy rain. •• Never permit water to spill over slopes, even where this may seem to be a good way to prevent ponding. This tends to I cause erosion and, in the case of fill slopes, can eat away carefully designed and constructed sites. + Do not cast loose soil or debris over slopes. Loose soil soaks up water more readily than compacted fill. It is not compacted to the same strength as the slope itself and will tend to slide when laden with water; this may even affect the I soil beneath the loose soil. The sliding may clog terrace drains below or may cause additional damage in weakening the slope. If you live below a slope, try to be sure that loose fill is not dumped above your property. I ADVANCED GEOTECHNICAL. SOLUTIONS, INC. I .:. Never discharge water into subsurface blanket drains close to slopes. Trench drains are sometimes used to get rid of excess water when other means of disposing of water are not readily available. Overloading these drains saturates the ground and, if located close to slopes, may cause slope failure in their vicinity. 4- Do not discharge surface water into septic tanks or leaching fields. Not only are septic tanks constructed for a different purpose, but they will tend, because of their construction, to naturally accumulate additional water from the ground during a heavy rain. Overloading them artificially during the rainy season is bad for the same reason as subsurface subdrains, and is doubly dangerous since their overflow can pose a serious health hazard. In many areas, the use of septic tanks should be discontinued as soon as sewers are made available. •• Practice responsible irrigation practices and do not over-irrigate slopes. Naturally, ground cover of ice plant and other vegetation will require some moisture during the hot summer months, but during the wet season, irrigation can cause ice plant and other heavy ground cover to pull loose. This not only destroys the cover, but also starts serious erosion. In some areas, ice plant and other heavy cover can cause surface sloughing when saturated due to the increase in weight and weakening of the near-surface soil. Planted slopes should be planned where possible to acquire sufficient moisture when it rains. + Do not let water gather against foundations, retaining walls, and basement walls. These walls are built to withstand the ordinary moisture in the ground and are, where necessary, accompanied by subdrains to carry off the excess. If water is permitted to pond against them, it may seep through the wall, causing dampness and leakage inside the basement. Further, it may cause the foundation to swell up, or the water pressure could cause structural damage to walls. Do not try to compact soil behind walls or in trenches by flooding with water. Not only is flooding the least efficient way of compacting fine-grained soil, but it could damage the wall foundation or saturate the subsoil. + Never leave a hose and sprinkler running on or near a slope, particularly during the rainy season. This will enhance ground saturation which may cause damage. + Never block ditches which have been graded around your house or the lot pad. These shallow ditches have been put there for the purpose of quickly removing water toward the driveway, street or other positive outlet. By all means, do not let water become ponded above slopes by blocked ditches. Seeding and planting of the slopes should be planned to achieve, as rapidly as possible, a well-established and deep- rooted vegetal cover requiring minimal watering. It should be the responsibility of the landscape architect to provide such plants initially and of the residents to maintain such planting. Alteration of such a planting scheme is at the resident's risk. . The resident is responsible for proper irrigation and for maintenance and repair of properly installed irrigation systems. Leaks should be fixed immediately. Residents must undertake a program to eliminate burrowing animals. This must be an ongoing program in order to promote slope stability. The burrowing animal control program should be conducted by a licensed exterminator and/or landscape professional with expertise in hill side maintenance. In conclusion, your neighbor's slope, above or below your property, is as important to you as the slope that is within your property lines. For this reason, it is desirable to develop a cooperative attitude regarding hillside maintenance, and we recommend developing a "good neighbor" policy. Should conditions develop off your property, which are undesirable from indications given above, necessary action should be taken by you to insure that prompt remedial measures are taken. Landscaping of your property is important to enhance slope and foundation stability and to prevent erosion of the near surface soils. In addition, landscape improvements should provide for efficient drainage to a controlled discharge location downhill of residential improvements and soil slopes. Geotechnical Review Due to the presence of expansive soils on site and the fact that soil types may vary with depth, it is recommended that plans for the construction of rear yard improvements (swimming pools, spas, barbecue pits, patios, etc.), be reviewed by a geotechnical engineer who is familiar with local conditions and the current standard of practice in the vicinity of your home. Additionally, recommendations contained in the Geotechnical Engineering Study report apply to all future residential site improvements, and we advise that you include consultation with a qualified professional in planning, design, and construction of any improvements. Such improvements include patios, swimming pools, decks, etc., as well as building structures and all changes in the site configuration requiring earth cut or fill construction. ADVANCED GEOTECHNICAL SOLUTIONS, INC.