Loading...
HomeMy WebLinkAboutCT 02-25; NORTH PARK AT LA COSTA; FINAL COMPACTION REPORT OF GRADING; 2004-07-30I Geotechnucal • Geologic • Environmental .-- . .-, SS .............. 54 ;S •!' r -.5 1 - - - S - - ' - - .: _- . •_4 '.. - -. .- :. 5••_•' .•5 .-- 5 5- _ _.,-., .4 .., .- 4 • ....•___. 5 . *4 45 S •5s , 4 .4 ., .. 5• - 4••_ - . 4 1 4 ,.5_• 4 • -. - ........:---'.-.-:- ' '. -- -. •_. •-:. --••---.-'- -. _'1, Geotechnical • Geologic • Environmental 5741 Palmer Way • Carlsbad California 92008 • (760) 438 3155 • FAX (760) 931 0915 July 30, 2004 W.0. 3975-B-SC Hallmark Communities 10675 Sorrento Valley Road, Suite- 200-B San Diego, California 92121 Attention Mr Bruce Douthit Subject Final Compaction Report of Grading, Traditions at La Costa, 'Northpark at La Costa," Lots 1 through 14,Carlsbad, San Diego County, California Dear Mr. Douthit This report presents, a summary of the geotechnical testing and observation services provided by GeoSoils, Inc. (GSl) duringthe rough earthwork phase of development for '. Lots 1 through 14, within Traditions at La Costa development. The current phase of S earthwork commenced on, or about, April 21, 2004, and was generally cämpleted on July. ' 28, 2004. Survey of line and grade was performed by others, and not performed by GSI. ' The purpose of grading was to prepare relatively level pads for the cOnstruction of single- family residences and associated infrastructure. Based on the'observations and testing .' performed by GSI,.it is our opinion that the. building'pads and adjoining' areas appear'.. suitable for their intended residential use PREVIOUS WORK The site has been -previously graded under the purview of Benton Engineering, Inc. (see Appendix A). The reader, is referred to the Benton Engineering, Inc. report listed in Appendix A for prior grading, testing, and observation results The site was reported to .have been mass graded during the period from September 21, 1972 to February 6, 1974 (Benton, 1974) 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 Appendix A) GROUNDWATER : :.GroundWater .wäs not encodntered:during grading of'this portion of the project and therefore should not affect the proposed site development, provided our recommendations for landscape maintenance and planting are implemented As a result of the contrasting nature of the onsite earth materials, the possibility of future, localized perched water conditions and minor seepage cannot be precluded, and should be anticipated Should such conditions become apparent within the project in the future, additional recommendations for mitigation may be provided upon request GEOTECHNICAL ENGINEERING Preparation of Existing Ground 1 Prior to grading, the major surticial vegetation was stripped and hauled offsite 2 Removals, consisting of topsoil/colluvium and near-surface weathered artificial fill, were performed to the minimum depths and lateral extent recommended in the approved referenced reports by GSI (see Appendix A) The approximate elevations of the removal bottoms and 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 per ii cent of the laboratory standard / 4 Fills placed on sloping surfaces steeper than 5 1 (horizontal vertical [h v]), as indicated by pre-existing topography, were keyed and benched into competent soil material or bedrock 5 All processing of original ground was observed by a representative of GSI Fill Placement Fill, consisting of native and import 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 approximately 3 feet of fill was placed on Lots 1 through 12, and materials greater than 12 inches in diameter may have been routinely placed below 10 feet from finish grade during the previous grading (Benton, 1974) However, oversized materials may not be precluded from occurring, and/or excavation difficulties may be encountered at depths as-shallow-as 3 feet, or less, Hallmark Communities •.. . : . . . .:. W.O. 3975-B-SC Traditions at La Costa Carisbad July 30 2004 File e wp9\3900\3975b fcr Page 2 GeoSoils, Inc. below finish grade Thus, the potential for excavation difficulties and oversized materials should be disclosed to all homeowners and other interested parties Slopes 1 All slopes are considered grossly and surficially stable and should remain so under normal conditions of care, maintenance, and rainfall As a result of the nature of the onsite materials, slopes may be subject to minor erosion/gullying under concentrated flow Jrom Jrrigation. and/or misdirected surface drainage Landscaping of these slopes should be implemented as soon as possible to mitigate such conditions Other recommended mitigation measures are presented in the "Development Criteria" section of this report 2 Compaction on the face of fill slopes was achieved by back-rolling and/or track Walking. FIELD TESTING 1 Field density lests were performed using nuclear densometer ASTM Test Methods D-2922 and D-3017 and sand cone ASTM Test Method ASTM D-1556. S. 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, orlessthan 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 TRANSITION LOT Lot 14 contains a plan transition between cut and fill As requested by the Client, Lot 14 was completed to the grades specified on the grading plans for "Northpark at La Costa" (Snipes-Dye Associates, 2003) Therefore, the plan transition, which occurs at the northeast end of Lot 14, was not mitigated during this phase of site grading If any future settlement-sensitive structures are planned, GSI should be contacted regarding earthwork MAXIMUMDENSITY MOISTURECONTENT `,-SOIL A - Olive Green, SANDY CLAYS 112.0 17.5 B:- Light Brown, SANDY CLAY 116.0 14.0 C - Gray Brown, SILTY SAND(import) 125.0 8.5 Expansion Index Expansive soil conditions have been evaluated for the site Representative samples of the soils exposed at current finish grades were recovered for expansion index testing Expansion Index (E I ) testing was performed in general accordance with Standard 18-2 of the Uniform Building Code ([UBC], International Conference of Building Officials [ICBO], 1997) Based on the test results obtained of 91 to 115, the expansive potentials of the soils within the subject lots are classified as high (i.e., high expansive potentials 91 to 140) The test results are included in Table 2 following the text of this report Sulfate/Corrosion Testing Representative samples of the materials exposed at the current grades onsite have been collectdd for soluble sulfate testing The testing included determination of soluble sulfates, pH, and saturated resistivity. Results indicate that site soils are very strongly acidic (pH=4 9) with respect to acidity and are severely corrosive to ferrous metals Severely corrosive soils are considered to be below 1,000 ohrrs-cm Based upon the soluble sulfate results of 0A 46 percent by weight in soil, the site soils have a moderate corrosion potential to concrete (UBC range for moderate sulfate exposure is -.0. 10 to 0.20 percentage, by weight soluble [SO4] in soil Hallmark Communities W.0. 3975-13-Sc Traditions at La Costa Carlsbad July 30 2004 FHe e wp9\3900\3975b fcr Page 4 GeoSoils, Inc. The use of Type II concrete with an altered water-cementious ratio, per the UBC, is required, however, corrosion protection for buried metallic structures, including rebar, piping, etc.-, has been evaluated by a corrosion. engineer. The soil corrosivity study report . is include in this report in Appendix B Test results are also included in Table 2, following the text of this report Atterberg Limits Tests were performed on soils exhibiting high , expansion potentials (i.e., El between, 91 and 140), per 1997 UBC requirements, to evaluate the liquid limit, plastic limit, and plasticity index in general accordance with ASTM D-431 8 The test results are presented below LOCATION LIUiDcPLASTIC LiMIT4 PLASTiCiTY: lDE* Lots 1-4 50 20 30 - Lots 5-7 57 19 . 38. Lots 8,9, and 14 43 19 24 Lots 10-12 48 18 . . . 30 CONCLUSIONS AND RECOMMENDATIONS . . . . Unless superceded by recommendations presented herein, the conclusions and recommendations contained in GSI reports (see Appendix A) remain pertinent and applicable. All settlement-sensitive improvements should be minimally designed to accommodate 1 inch of differential settlement in 40 feet (1/480) and the expansive and corrosive soil conditions outlined herein FOUNDATION RECOMMENDATIONS . . . General The foundation design and construction recommendations are based on laboratory testing and engineering analysis of onsite earth materials exposed at current finish grades byGSl. Recommendations for PT systems are provided in the following sections. The foundation systems may be used to support the proposed structures, provided they are founded in competent bearing material The proposed foundation systems should be designed and constructed in accordance with the guidelines contained in the UBC (ICBO, 1997) Hallmark Communities .. . ., . . . .. .. . . . . W.O. 3975 -B-SC Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 5 GeoSoils, Inc. Foundation Design 1 The foundation systems should be designed and constructed in accordance with gridlines presented in the latest edition of the UBC 2 An allowable bearing value of 1,500:pounds per square foot (psf) may be used for ..design:.of footings which maintain a minimum width of 12 inches(continuous) and 24 inches square (isolated), and a minimum depth of at least 12 inches into the properly compacted fill The bearing value may be increased by.,one-third for seismic or other temporary loads This value may be increased by 20 percent for each additional 12 inches in depth to a maximum of 2,500 psf No increase in bearing value for increased footing width is recommended 3 For lateral sliding resistance, a'0.85-:,c6 efficient of friction may be utilized for a concrete to soil contact when multiplied by the dead load 4 Passive earth pressure may be computed as an equivalent fluid having a density of 250 pounds per cubic foot (pcf) with a maximum earth pressure of 2,500 psf. 5 When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third 6 All footings should maintain a minimum 7-fo6t horizontal distance between the base 4 . of the footing and any adjacent descending slope, and minimally comply with the guidelines depicted on Figure No 184-1 of the UBC (lCBO, 1997) Construction The following foundation construction recommendations are presented as a minimum criteria from ra. soils engineering viewpoint The current near finish pad grade soils expansion potentials are generally in the high expansive potential (E .I. 91to 90) POST-TENSIONED SLAB SYSTEMS Recommendations for utilizing PT slabs on the site is based on soil parameters exposed at current near finish grade on the site The recommendations presented below should be followed in addition to those contained in the previous sections, as appropriate The information and recommendations presented below in this section are not meant to supersede design by a registered structural engineer or civil engineer familiar with PT slab design PT slabs should be designed using sound engineering practice and be in accordance with local and/or national code requirements Haiimark Communities W.0.. 3975 B Sc Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 6 GeoSoits, Inc. From a.-soil expansion/shrinkage standpoint, a common contributing factor to distress of structures using PT slabs is fluctuation of moisture in soils underlying the perimeter of the slab, compared to the center, causing a "dishing" or "arching" of the slabs To mitigate this possibility, a combination of soil presaturation and construction of a perimeter cut-off wall should be employed Perimeter cut-oft walls should be a minimum of.18 inches deepfor highly expansive soils: The cut off walls may be integrated into the slab design or independent of the slab and should be a minimum of 5 inches thick The vapor barrier, should be covered above and below with a 2-inch layer of sand (4 inches total),- to aid in uniform curing of the concrete; and it should be adequately sealed to provide a continuous water-proof barrier under the entire slab Specific soil presaturation is not required, however, the moisture content of the subgrade soils should be equal to or greater than the soils' optimum moisture content to a depth of 18 inches below grade, for highly expansive soils ••. "• . Post-Tensioning. Institute (PT!) Méthbd .• • •. PT 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 PTL The following table presents suggested minimum coefficients to be used in the P11 design method Thornthwaite Moisture Index I -20 inches/year. Correction Factor for Irrigation, I 20 inches/year Depth to Constant Soil Suction : .. 7 feet Constant soil SuOtion (pf) •.. . 3.6 Modulus of Subgrade Reaction (pci) •• . 75 5 Moisture Velocity • . • 0.7 inch/month 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 structures have positive drainage that is maintained away from structures Therefore, it is important that information regarding drainage, site maintenance, settlements, and effects of expansive soils be passed on to future owners Hallmark Communities W.0. 3975 B SC Traditions at La Costa Carlsbad Juiy 30 2004 File e wp9\3900\3975b fcr Page 7 Inc GeoSoils, . EXPANSIVE INDEX OF SOIL SUBGRADE, t (per the UBC). ., EXPANSION""::-.'. (E.i.= 91 TO 1301 em center lift 5.5 feet em edge lift 4.5 feet Ym center lift 3.5 inch Ym edge lift 1.2 inch Deepened footings/edges around the slab perimeter must be used to minimize non-uniform surface moisture migration (from an outside source) beneath the slab An edge depth of 18 inches should be considered a minimum The bottom of the deepened footing/edge should be designed to resist tension, using cable or reinforcement per the structural engineer. Other applicable recommendations presented under conventional foundation and the California Foundation Slab Method should be adhered to during the design and construction phase of the project WALL DESIGN PARAMETERS CONSIDERING EXPANSIVE SOILS Conventional Retaining Walls The design parameters provided below assume that either very low expansive soils (Class 2 permeable filter material or Class 3 aggregate base) gr native 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 or damp-proofed, depending on the degree of moisture protection desired 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 Hallmark Communities W.0. 3.975-13-SC Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 8 GeoSoils, Inc. Restrained Walls Any retaining walls that will be restrained prior to placing and comacting backfillmaterial 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 SURFACE SLOPE OF; EQUIVALENT, RETAINED MATERIAL FLUID WEIGHT P C F FLUID WEIGHT P C F HÔRIZôNTAL:VERTiCAL SELECT BACKFILL) .1 (NATIVE BACKFILL) Level* . 38 .50 2tol . 65 * Level backfill behind a retaining wail is defined as compacted earth materials, properly drained, without a slope for a distance of 2H behind the wall. Retaining Wall Backfill and Drainage Positive drainage must be provided behind all retaining walls in the form of gravel wrapped in.ge mofabric and outlets. A backdrain syste 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. Backdraihs should consist of a 4-inch diameter perforated PVC or ABS pipe encased in either Class 2 permeable filter material or 1/2..inch'to 3/4-IflCh gravel wrapped ' in approved filter fabric (Mirafi 140 or equivalent). For low expansive backfill, the filter material should extend a minimum 6f.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 Hallmark Communities •• .• . . • . W.O. 3975-B-SC . . Traditions at La Costa, Carlsbad • . • • • :. . • . • • • July 30, 2004.. File e wp939OO\3975b fcr Page 9 GeoSoils, Inc. DETAILS N T S 2 Native Backfill Provide Surface Drainage Slope or Level Native Backfill ±12" © Rock Filter Fabric ©Waterproofing ox Membrane (optional) 1 or Flatter © Weep Hole • llllflll Native Backfill Finished Surface (D WATERPROOFING MEMBRANE (optional): Liquid boot or approved equivalent © ROCK 3/4 to 1-1/2" (inches) rock.: : © FILTER FABRIC: Mirafi 140N or approved equivalent; place fabric flap behind core. PIPE 4" (inches) diameter perforated PVC. schedule 40 or approved alternative with minimum of 1% gradient to proper outlet point. © WEEP HOLE Minimum 2" (inches) diameter placed at 20' (feet) on centers along the wall, and 3" (inches) above finished surface. (No weep holes for basement walls.) 0 TYPICAL RETAINING WALL BACKFILL -\ - 1 AND DRAINAGE DETAIL 40 ?O DETAIL 1 _J Geotechnical • Geologic • Environmental (!)Waterproofing - Membrane (oi © Weep Finished @ WATERPROOFING MEMBRANE (optional): Liquid boot or approved equivalent. © DRAIN: Miradrain 6000 or i-drain 200 or equivalent for non-waterproofed walls. Miradrain 6200 or ]-drain 200 or equivalent for waterproofed walls. © FILTER FABRIC: - Mirafi 140N or approved equivalent; place fabric flap behind care. @PIPE: 4" (inches) diameter perforated PVC. schedule 40 or approved alternative with minimum of l% gradient to proper outlet point. ®WEEP HOLE: Minimum 2" (inches) diameter placed at 20' (feet) on centers along the wall, and 3" (inches) above finished surface. (No weep holes for-basement walls.) • RETAINING WALL BACKFILL II • AND SUBDRAIN DETAIL • • Aft GEOTEXTILE DRAIN •DETAIL 2. Geotechnical • Geologic • Environmental 1 I or Flatter ©Clean Sand Backfill DETAILS Provide Surface Drainage n2_ Waterproofing f 7. Membrane (opt H © Weep Hole © Filter Fabric Finished Surface Pi I Heel Width 4 ®WATERPROOFING MEMBRANE (optional): . . Liquid boot or approved equivalent. . . © CLEAN SAND BACKFILL:. . Must have sand equivalent value of 30 or greater; can be densified by water jetting. © FILTER FABRIC: . . Mirafi 140N or approved equivalent. ROCK: . . 1 cubic foot per linear feet of pipe or 3/4 to 1-1/2" (inches) rock.. © PIPE: . . . . . 4" (inches) diameter perforated PVC. schedule 40 or approved alternative with minimum of 1% gradient to proper.outlet point. • • © WEEP HOLE: . •. . . . Minimum 2" (inches) diameter placed at 20' (feet) on centers along the wall, and 3" (inches) . above finished surface. (No weep holes for basement walls.) RETAINING WALL AND SUBDRAIN DETAIL CLEAN SAND BACKFILL DETAIL 3 Geotechnical • Geologic. Environmental 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 90 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 in walls higher than 2 feet should not be considered The surface of the backfill should be :sealed by pavement or the top 1.8 inches compacted with native soil. (E.l 90); 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 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 minimum of a 2-foot overexcavation and recompaction of cut materials for a distance of 21-1, from the point of transition Increase of the amount of reinforcing steel and wall detailing (Le., 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 but. 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 Hallmark Communities • • S • • •. S : W.O. 3975-B-SC Traditions at La Costa Carlsbad...July 30 2004 File e wp9\3900\3975b fcr Page 13 GeoSoils, Inc. 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—Withl 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 becomes progressively worse Accordingly, the developer should provide this information to any homeowners and homeowners association 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 . p,rovided 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 5-foot vertical zone below the slope face and projected upward parallel to the slope face Creep Load 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 Hallmark Communities.. W.O. 3975-B-SC Traditions at La Costa Carlsbad% July 30 2004 File: e wp9\3900\3975b fcr Page 14 GeoSoils, Inc. Point of Fixity Located a distance of .1 .5 times the caisson's diameter, below the creep zone Passive Resistance 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 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 Pause 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 homeowners or homeowners association 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 verified 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 Iayer 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 mini. imum 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 :Hallmark Communities, . .. : .. . WO. 3975-B-SC. . . Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 15 GeoSoils, Inc. .4. . '.. The Use of transverse and iohgitüdinalcohtrol joints are ,recommendêd 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, ½ to 3/8 inches deep, often enough so that no section is greater than 10 feet by 10 feet For sidewalks or narrow slabs, control joints should be provided at 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 . Driveways, sidewalks, and patio slabs adjacent to the ho Use 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 - Planters and walls should not be tied to the house 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 homeowner or homeowners association 7.12.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 Hallmark Communities , . . , . : ,. , , . . , ..- ' ' W.O. 39757B-sc " •' Traditions at La Costa Carlsbad July 30 2004 Fiie e wp9\3900\3975b fcr Page 16 GeoSOiIs, Inc.''. 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 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 fri 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 (i.e., -.,.separations :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. LIFE 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 LIFE 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 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, 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 recommendations .for . : mitigation, should be provided to each homeowner and/or any homeowners 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 . . • Hallmark Communities •.. . ' ': ..... • W.O. 3975B-SC " Traditions at La Costa Carisbad July 30 2004 Fiie e wp9\3900\3975b fcr Page 17 GeoSoils, Inc. 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 can adversely affect site improvements, and cause perched groundwater conditions Graded slopes constructed utilizing onsite materials would be erosive Eroded debris may be minimized and surlicial 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 'prograni to prevent burrowing should be implemented..' Irrigation Of natural (ungraded) slope. areas is. generally not recommended. These recommendations regarding plant.typé, irrigation practices, and rodent control should be ' provided to each homeowner. 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 gradihg, landscaping, and building construction. Therefore, care should be taken that future landscaping or construction activities do not create adverse drainage conditions. Positive.sitedrainage within lots and common areas should be provided and maintained at all times. Drainage should hot 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 this potential. If, areas of seepage develop, recommendations for minimizing this effect 'could be provided upon request. , .. . . ' •' • ' . ,: , ' . ., Hallmark Communities . ' .. ' . . ' . W.O. 3975-B-SC Traditions at La. Costa, Carlsbad ' : ' ' ... .,. • . ' . '' . July30, 2004 • •. ' . File e wp9\3900\3975b fcr Page 18 GeóSoits, 'Inc. 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 satuiation of soil-at-the base of the slope9 Are the slopes hard rock and/or impermeable, or relatively permeable, or, do the slopes already have or are they proposed to have subdrains (Le., , stabilization fills, etc)2 Was the lot at the base of the slope overexcavated or is it proposed to be overexcavated9 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, homeowner Irrigation, or other circumstances Where drains are constructed during grading, including subdrains, the Iocátions/elèvations 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 homeowners and any homeowners association Hallmark, Communities S S ..W.O. 3975-13-SC 'S Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fer Page 19 GeoSoils, Inc. DETAILS N.T.S. SCHEMATIC TOE DRAIN DETAIL •. •• •:. •. _7 -. ••• •• ••• • .• • Drain May Be Constructed into, S or at, the Toe of Slope ,-' • S • S • —Pad Grade -,,,-c.• S -Native NOTES >fr'nD' Ks 1) Soil Cap Compacted to 90 Percent Relative - Compaction 12 Minimum 2) Permeable Material May Be Gravel Wrapped in Filter Fabric (Mirafi 14014 or Equivalent) 3) 4-Inch Diameter Perforated Pipe (SOR 35 or e,- Equivalent) with Perforations Down S - _ • 4.) Pipe to Maintain a Minimum 1 Percent Fall. 5.) Concrete Cutoff Wall to be Provided at Transition to Solid Outlet Pipe. Permeable Mated • • • 6.) Solid Outlet Pipe to Drain to Approved Area. 7.) Cleanouts are Recommended at Each Property 24" • • Line. Minimum - S • Drain Pipe S S S 12" H -- 4-- ••- -• SCHEMATIC TOE DRAIN DETAIL - S • • S • -- ioSc1, Itç. DETAIL 4 - Geotechnical • Coastal Geologic • Environmental :. ••,• ' ' ' DETAILS' NT S 21 SLOPE (TYPICAL)-.. TOP OF WALL ' • -. ..... . ' .•• . - BACKFILL WITH COMPACTED NOTES NATIVE SOILS - 1) Soil Cap Compacted to 90 Percent - Relative Compaction 12 RETAINING WALL ' ,. - - -- ' ' MIN 2.) Permeable Material May Be Gravel Wrapped in Filter Fabric (Mirafi 140N or Equivalent). 3) 4-Inch Diameter Perforated Pipe - (SDR-35 of Equivalent) with SO .-MIRAFI 140 FILTER FABRIC ' Perforations Down. FINISHED GRADE - /' OR EQUAL Pipe to Maintain a Minimum I Percent Fall. ,7T314" CRUSHED GRAVEL •' . . , . -11 1 7--- 5) Concrete Cutoff Wall to be Provided WALL FOOTING-...! - , .. ..• - . , at Transition toSolid Outlet Pire.. • I . • :6.) Solid Outlet Pipeto Drain to L— • E'.'' ' ' Approved Area. • • • -' Mf 24" , . • •. 7.) Cleanouts are Recommended at M , -4 DRAIN Each Property Line I • , . • , 8.) Compacted Effort Should Be Applied to Drain Rock 1 T02 T H2_ ' . • • SLJBDRAIN ALONG RETAINING WALL DETAIL ' ., • S . .•• '' NOT TO SCALE - SUBDRAIN ALONG RETAINING WALL DETAIL DETAILS ,.• . : • .', . • • Geotechnlcal • Coastal • Geologic. Environmental,: . . I 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 P 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 Jo the type of vegetation chosen and their potential effect upon surface Improvements (Le.,'. 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 coll'ector pipes or non-erosive devices that will carry the water away from the house 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 drainage conditions, or damaged utilities, and should be anticipated Should perched groundwater conditions develop, this office could assess the affected area(s)-and provide Hallmark Communities : ' ' , W.O. 3975 -SC : Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 22 GeoSoils, me. the appropriate recommendations to mitigate the observed groundwater conditions Groundwater conditions may change with the introduction of irrigation, rainfall, or other factors Site lmi,rovémeñts Recommendations for .exterior concrete flätwork design.ad construction can be. provided . upon request 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 This office should be notified in advance of any fill placement, grading of the site, or trench backfi Ili ng after rough grading has been completed This includes any grading, utility trench, and retaining wall backfills 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 and 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 verify that the excavations are 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 excavations should be compacted to a minimum relative compaction of 90 percent, if not removed from the site... .. : .. : .• .. . . ... . . ....... .. . .. ...' Hallmark Communities . .. . .S . . . : .. . M.O. 3975-MC. I .. Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 23 GeoSoiIs Inc* Trenching Considering the nature of the onsite soils, it should be anticipated that caving or sloughing could be a factor in subsurface excavations and trenching Shoring or excavating the trench walls at the angle of repose (typically 25 to 45 degrees) may be necessary and should be anticipated All excavations should be observed by one of our representatives and minimally conform to CAL-OSHA and local safety codes 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 (-I 2-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 verify 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 verify the desired results 3 All trench excavations should conform to CAL-OSHA and local safety codes 4. .Utilitieárossing '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 . . . ... . .. .. ( 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 significant excavation (i.e., higher than 4 feet) During placement of subdrains, toe drains, or other subdrainage devices, prior to placing fill and/or backfill .. Haiimark Communities . . . . . . . S . . .3975-B-SC Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b tcr Page 24 GeoSoils, Inc. 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 barriers (i.e., visqueen, etc.).. .• . ... .:.. : . . S. 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 homeowner improvements, such as flatwork, spas, pools, walls, etc , are constructed 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 homeowners/homeowners associations for geotechnical aspects, including irrigation practices, the conditions outlined above, etc., prior to any sales At that stage, GSI will provide homeowners maintenance guidelines which should be incorporated into such documents 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 .' S design criteria for thedesign 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.'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. Hallmark Communities W.0. 3975 B SC Traditions at La Costa Carlsbad*July 30 2004 File e wp939OO\3975b fcr Page 25 GeoSoils, Inc. 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 transmittheirrequeststo GSI In orderto mitigate potential distress, thefoundation 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 design criteria specified herein PLAN REVIEW Me Final project plans.:..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 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 is expressed or implied 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. 1. '*ork -performed.: when GSF 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 Hallmark Communities . . . . .'.. , . . . . . . W.O. 3975-B-SC Traditions at La Costa Carlsbad July 30 2004 File e wp9\3900\3975b fcr Page 26 GeoSoils, Inc. GeOSoils, Inc. 37 6/25/04 - Lot 7 : Traditions FG 152 • 107.1 91.1 92.3 . ND ND . B B 38 6/29/04 Lot 12/S.W. Corner Traditions 283.0 16.5 104.8 90.3 SC B Hallmark Communities W 0 3975 B SC Traditions at La Costa Carlsbad July 2004 File C \excel\tabies\3900\3975b Page 1 GeoSoils, Inc. TEST NO. DATE TEST LOCATION TRACT• NO. ______ ELEV OR MOISTURE CONTENT DRY DENSITY REL COMP TEST METHOD SOIL TYPE 1* 4/21/04 Lot 12 North Park 287.0 11.1 104.7 90.3 Sc B 1k 4/21/04 Lot 12 North Park 287.0 15.3 . 104.5 90.1 ND B .2* 4/21/04 11+25 Corte Tradicion North Park 287.0 14.7 105.0 90.5 ND B 2A 4/21/04 11+25 Carte Tradicion North Park 287.5 15.0 104.7 90.3 ND B .3. 4/21104 Lot .1 North Park 287.0 14.7 105.0 90;5 ND B 4 4/22/04 Lot -2 North Park 288.5 18.1 101.6 . 90.7 SC A 4/22/04 Lot 11 North Park 288.0 17.9 101.0 90.2 ND A 6 4/22/04 Lot 10 North Park 289.0 14.8 104.9 90.4 ND B 7 4/22/04 Lot 3 • North Park 288.0 18.5 100.8 90.0 ND A 8 4/23/04 . Lot 1 . North Park 289.0 17.7 . 101.6 90.7 . ND , A 9 4/23/04 Lot 2 North Park 288.0 15.3 105.7 91.1 SC B 10* 4/23/04 Lot 3. North Park 288.5 15.8 97.3 83.9 ND B 10A 4/23/04 . • Lot 3 North Park 288.5.. 14.9 105.3 90.8 SC B 11 4/23/04 Lot 12 North Park 287.0 . 17.8 101.2 90.4 ND A 12 .4/23/04 . . Lot 11 North Park 288.0 . . 17.5 101.8 90.9 ND A 13 4/23/04 . Lot 13 North Park 287.0 17.8 101.1 90.3 ND 14 4/26/04 ..Lot4 North Park 287.0 .17.6 103.5 92.9 SC A 15 4/26/04 Lot 10 North Park .291.0 .14.3 105.0 90.5 ND B 16 4/26/04 Lot 12 North Park 289.0 15.1 ,. 105.4 90.9 .'.,-ND B 17 - 4/26/04 Lot 11 North Park 290.0 .14.3 108.5 93.5 •SC B 18* 4/27/04 Lot North.Park 289.0 . .12.5 111.8 96.4 SC • B 18A 4/27/04 Lot North Park 289.0 • .15.1 104.8 • 90.3 ND B 19 • 4/27/04 Lot North Park 289.0 _• .14.7 • 105.4 90.9 ND B 20 4/27/04 Lot 2 . North Park 289.0 14.3 105.0 90.5 .ND 21 4/28/04 Lot 11 .. North Park 290.65 176 105.1 90.6 SC B 22 5/3/04 Lot 8 • North Park 291.0 17.8 . 105.3 90.8 ND B 23 5/3/04 Lot 9 North Park 291.5 17.5 105.1 90.6 ND B 24 6/23/04 Lot 5 Traditions 293.0 .• 15.5 106.8 92.0 ND B 25 6/23/04 Lot 4 Traditions 291.0 16.2 105.3 90.7 ••ND B 26 6/23/04 Loti Traditions 290.0 15.9 106.1 .91.4 ND B 27 6/24/04 ...t 7 Traditions 294.0 14.9 . 107.4 92.5 ND B-- 28 6/24/04 Lot 6 Traditions 293.0 15.4 105.8 91.2 SC 29 6/24/04 • Lot 1 Traditions FG 17.0 • 104.9 90.4 ND B. 30 6/24/04 ' Lot 2 - . Traditions FG • .16.1 106.4 91.7 ND 13- 31 6/24/04 Lot 3 Traditions FG • 15.8 105.7 91.1 ND • 32 6/25/04 Lot 4 Traditions FG . 15.0 - • 108.2 93.2 ND 33 6/25/04 Lot 6 Traditions 294.0 .. 16.8 105.1 90.6 ND B 34 6/25/04 Lot 7 - Traditions 295.0 15.T 106.4 91.7 ND B 35 6/25/04 • Lot 5 _Traditions FG • 15.9 • 106.3 91.6 ND B 36 6/25/04 • Lot 6 • Traditions .FG 16.2 105.7 TEST NO. DATE - TEST LOCATION TRACT NO. ELEV OR DEPTH (ft) MOISTURE CONTENT (%) DRY DENSITY (pcf) REL COMP (%) TEST METHOD SL TYPE 39 6/29/04 Lot 11/South Slope Traditions 285.0 16.0 106.3 91.6 ND B 40 6/29/04 Lot 10/South Slope Traditions 287.0 15.4 105.7 91.1 ND B 41 6/30/04 Lot 10 Traditions 289.0 14.6 107.6 92.7 ND B 42. 6/30/04 Lot 11 Traditions 287.0 15.1 106.1 91.4 SC B 43 6/30/04 . Lot 12 Traditions .286.0 15.8 105.8 91.2 ND B 44 7/2/04 Lot Traditions 292.0 15.0 105.0 90.5 ND B 45• 7/2/04 Lot Traditions 291.0 15.6 105.9 91.2 ND B 46 . 7/6/04 Lot 8 Traditions 293.0 15.0 106.9 92.1 ND. B 47 7/6/04 Lot Traditions 292.0 15.6 106.3 91.6 ND . B 4.8 7/7/04 Lot . Traditions FG 10.6 117.6 94.0 ND C 49 7/7/04 Lot 9 Traditions FG 9.4 . 115.5 92.4 ND .0 50 1 7/26/04 Lot 10 Traditions FG 15.6 105.9 91.2 ND B 51 7/27/04 Lot 11 Traditions 287.0 15.8 107.1 92.3 ND B 52 7/27/04 Lot 12 Traditions 288.0 16.6 106.0 91.3 ND B 53 7/7/04 11 +80 Corte Tradition Traditions FG 16.0 105.5 91.0 ND B 54 7/7/04 10+50 Corte Tradition Traditions FG 15.4 104.8 90.4 ND B 55 7/7/04 12+03 Corte Tradition Traditions . FG 15.0 107.3 .92.5 ND B 56 7/7/04 13+03 Corte Tradition Traditions FG 14.8 104.5 90.1 ND B 57 7/28/04 Lot 11 Traditions FG 16.0 105.4 90.8 ND B 58 7/28/04 Lot 12 Traditions FG 14.8 105.0 1 90.5 ND B LEGEND:- * = Indicates Failed Test A = Indicates Retest FG = Finish Grade ND = Nuclear Densometer SC = Sand Cone Hallmark Communities . . Traditions at La Costa, Carlsbad . File: C:\excel\tables\3900\3975b . . GeoSoils, Inc. W.O. 3975-B-SC July 2004 Page - "EXPANSION.' • POTENTIAL (per SOLUBLE - : UBC) SULFATE APPROX.' .. :. DEPTH UBC CONTENT UBC LOT • - RESISTIVITY. OFFILL' pT:' . CLASS ,ught.'o). SS pH'. (ohm/ern)'., ..(ft)-'' CATEGORY'. REQUIRED 1 ' 91 High 0.146 Moderate .4.9'.410 5 III Yes 2 • 93 High 0.146 Moderate 4.9 410 . 6 ifi • - • Yes 3 . . . 101 High 0.146 Moderate 4.9 410 7 ' Ill Yes 4 107 High 0.146 Moderate 4.9 '410 8 III Yes 5 95 High 0.146 Moderate 4.9 410 4 III Yes' 6 104 High ' 0.146 ' Moderate 4.9 ' 410 ' 3 III . . Yes 7 . 96 High 0.146 Moderate 4.9 '410 3 ' ' III Yes 8 106 High 0.146 • Moderate 4.9 . • 410 4 • III • -. ' Yes 9 •. •- 110 High 0.146' Moderate 4.9 410. 3 • III Yes 10 94 High 0.146 Moderate 4.9 410 , 6 • III . Yes 11 . 105 High 0.146 Moderate 4.9 410 • 6 . - Ill . • Yes : 12 • 93 High ' 0.146 Moderate 4.9 410 4 Ill . . Yes Corte Traditions (13) 115 High 0.146 Moderate 4.9 410 .. 2 ' . NA NA - Park Site (14) ' 108 High 0.146 Moderate 4.9 '410 .' Transition ' NA • ' . NA 5.. 5 .5 1 4. 5 4 5 '5 4 '5 .1 - •'-'. . APPENDIX A REFERENCES 44 .4 4 4. 5. 'S .4 5, .4 5. / r 5 4 4 5 .._ 4 .. .'..-, '.• -,. .- - - ,•• •. , ''•5_ - .. - . ., S - '''5', * .4' :•rS• •s . A .. -. . . - - s S.. t *5 4 1 I.. - 1 4 - 4 4. APPENDIXB SOIL CORROSIVITY STUDY - I 1 / - I S. - -, .- ., . -S. , -. - , . .:-'- 4 4. 5 a I 4 .5- I I -S 1 4 S '' '•• .5 5 ._' .... . .• - - ?, ,, 5 , . 'S ... s., - -. - . - ,:. ,-- S .- ,••5'' ' -. :'- - . -. ,' .. . S 5 4 -- 4 '5 4 4. 4 4. I M J SCHIFF &.-ASSOCIATES, INC Consulting Corrosion Engineers - Since 1959 Phone: (909),626-09 ' 67 I Fax: (909) 626-3316 431 W Baseline Road E-mail: mjsa@mjschiff.com Claremont CA 91711 http://www.mjschiff.com June 151 2004 1 GEOSOILS, INC. 5741 Palmer Way Carlsbad, California 92008 Attention Mr Brian .Voss'. Re Soil Corrosivity Study Hallmark - Traditions at La Costa La Costa, California Your #3975-B-SC, MJS&A #04-0738HQ INTRODUCTION Laboratory tests have been completed on one soil sample you provided for the referenced project. The purpose of these tests was to determine if the soils might have deleterious effects on underground utility piping and concrete structures We assume that the sample provided is representative of the most corrosive soil at the site The proposed project consists of 12 single-family homes. The site is located at the corner of Lévante' Street and La Costa Avenue. Water table depth was not provided; therefore, its effect on site corrosivity could not be accounted for in this analysis and report The scope of this study is limited to a determination of soil corrösivity and general corrosion control recommendations for matenals likely to be used for construction Our recommendations do I not constitute, and are not meant as a substitute for, design documents for the purpose of construction If the architects and/or engineers desire more specific information, designs, specifications, or review 00 0 of design, we. will be happy to work with them as a separate phase of this project. . 0 TEST PROCEDURES 0 The electrical resistivity of the sample was measured ma soil box per ASTM (157 in its as-received 0 condition and again after saturation with distilled water. Resistivities are at about their lowest value 0 0 when the sail is saturated.'The pH of the saturated sample was measured. A 5:1 water:soil extract . from the sample was chemically, analyzed for the major soluble salts commonly found in soils and for*. arrimonium arid., nitrate. The total 'acidity was determined, on the' sample to assess the acidic buffenng of the soil Test results are shown in Table 1 0 CORROSION AND CATHODIC PROTECTION ENGINEERING SERVICES 0 0 0 • PLANs'& SPECIFICATIONS • FAILURE ANALYSIS • EXPERT WITNESS • CORROSIVITY AND DAMAGE ASSESSMENTS GE@SOILS, INC JunL 15 2004 MJS&.A 404-0738HQ PauL 2 SOIL CORROSIVITY A major factor in determining soil corrosivity is electrical resistivity The electnLal resistivity of a soil is a measure of its resistance to the flow of electrical current Corrosion of buried metal is an electrochemical processin which the amount of metal loss due to corrosion is directly proportional to the flow, of electrical current (DC) from the metal into the soil Corrosion currents, following Ohm's Law, are inversely proportional to soil resistivity Lower electrical resistivities result from higher moisture and soluble salt contents and indicate corrosive soil A correlation between electrical resistivity and corrosivity toward ferrous metals is Soil Resistivity in ohm-centimeters Corrosivity Category over 10,000 mildly corrosive 2,000 to 10,000 • moderately corrosive 1,000 to 2,000 corrosive below 1,000 severely corrosive Other soil characteristics that may influence corrosivity towards metals are pH, soluble salt content, soil types, aeration, anaerobic conditions, and site drainage The electrical resistivity was in the mildly corrosive category with as-received moisture. When saturated, the resistivity was in the severely corrosive category. The resistivities dropped considerably with added moisture becausethe sample was dry as-received. Soil pH was 4.9. This value is very strongly acidic. Acidic soils can be corrosive to concrete and metallic building materials. . Total acidity was 480 mg H''Ikg. This is high enough .to cause significant deterioration of the . concrete as well as heaving if allowed to contact the concrete .. The soluble salt content of the sample was very high. Chloride and sulfate salts, were the predominant constituents. Sulfate was in a range where sulfate resistant cement is recommended. Ammonium and nitrate were detected in low concentrations Tests were not made for sulfide and negative oxidation-reduction (redox) potential because these samples did not exhibit characteristics typically associated with anaerobic conditions This soil is classified as severely corrosive to ferrous metals, aggressive to copper, and moderate for sulfate attack on concrete. . . GEOSOILS, INC June IS 2004 MJS&A 04-0738HQ Pae 3 CORROSION CONTROL RECOMiMENDATIONS, The life of buried materials depends on thickness, strength, loads, construction details, soil moisture, etc, in addition to soil corrosivity, and is, therefore, difficult to predict Of more practical value are corrosion control methods that will increase the life of materials that would be subject to significant corrosion Steel Pipe Abrasive blast underground steel piping and' apply a dielectric 'cbating, such as. polyurethane, extruded polyethylene, a tape coating system, hot applied coal tar enamel, or fusion bonded epoxy intended for underground use Bond 'underground steel pipe with rubber gasketed, meëhanical, grooved end, or other nonconductive type joints for electrical continuity.' Electrical continuity is necessary for corrosion' monitonng and cathodic protection Electrically insulate each buried steel pipeline from dissimilar metals and metals with dissimilar coatings (cement-mortar vs. dielectric), and above ground steel pipe to prevent dissimilar metal corrosion cells an& to facilitate the application of cathodic protection Apply cathodic protection to steel piping as per NACE International Standard RP-0 169-02 Iron Pipe Encase cast and ductile iron piping per AWWA Standard Cl 05 or coat with epoxy or polyurethane intended for underground use. Note: the thin factory-applied asphaltic coating applied to ductile iron pipe '.for transportation and aesthetic purposes does not constitute a corrosion control coating. Electrically insulate underground iron pipe from dissimilar metals and from above ground iron pipe with insulating joints per NACE International Standard RP-0286-02 Bond all nonconductive type joints for electrical continuity Apply cathodic protection 'to' ductile iron water piping as pet NACE International Standard RP- 0169-02:'. Copper 'Tubing.. Buried* copper tubing shall be protected by: Encasing-the copper in two layers of 10-mil thick' polyethylene sleeves, taking care not to damage the polyethylene Protect wrapped copper tubing by applying cathodic protection per NACE International Standard -0169-02. Any damaged polyethylene shall be 'repaired by wrapping it in 2 0-mil thick pipe wrapping tape: The amount ' of cathodic protection current needed can be minimized by coating the tubing Preventing soil contact. Soil contact may be prevented by placing the tubing. above ground. Install a factory coated copper pipe with a minimum of 100-mu thickness such as "Aqua . Shield" or similar products. ,Polyethylene coating protects against elements that corrode copper and prevents contamination between copper and sleeving However, it must be continuous with no cuts or defects if installed underground GEOSOILS, INC Junc 15 2004 MJS&A#04-0738HQ Paue4 Plastic ind Vitrified Clay Pipe No special precautions are required for plastic and vitn tied clay piping placed underground from a corrosion viewpoint Protect all fittings and valves with wax tape per AWWA Standard C2 17-99 or epoxy. All Pipe On all pipes, appurtenances, and fittings not protected by cathodic protection, coat bare metal such as valves, bolts, flange joints, joint harnesses, and flexible couplings with wax tape per AWWA Standard C2 17-99 after assembly. Where metallic pipelines penetrate concrete structures such as building floors, vault walls, and thrust blocks use plastic sleeves, rubber seals, or other, dielectric material to prevent pipe contact with the concrete and reinforcing steel Concrete Protect concrete structures and pipe from sulfate attack in soil with a severe sulfate concentration, 0.1 to 0 2 percent Use Type II cement, a maximum water/cement ratio of 0 50, and minimum strength of 4000 psi per applicable code, such as 1997 Uniform Building Code (UBC) Table 19-A-4. or Amencan Concrete Institute (ACI-3 18) Table 4.3 1 Standard concrete cover over reinforcing steel may be used for concrete structures and pipe in contact with these soils Concrete structures and pipe should be protected from acid attack due-to-the low pH and high total Acidity. Concrete can be protected by preventing contact with the moisture in acidic soil Contact can be prevented with impermeable, waterproof, acid resistant barrier coatings such as Liquid Boot® If soil/concrete contact is prevented, sulfate resistant cement, as specified above, is not required CLOSURE Our services have been performed with the usual thoroughness and competence of the engineering profession No other warranty or representation, either expressed or implied, is included or intended Please call if you have any questions Res.ectfuUy Submitted, Reviewed by, M.J. SCHIFF & AS$'OCIATES, INC. / / —"JamesTKe:gan Jo W French, P. E M J Schiff & Associa tes, Inc Consullinç' Corrosion L,iguILLr' -SI/ILL I959 Phone: (909) 626-0967 ra (909) 6-76-3316 431 JJ' BUSLIUlL Road E-mail lu//a lnJ(JI iff Lan! ClurLinont, C-1. 91711 t Lhs1tL IilJ(1zIfJ coin Table I - Laboratory Tests on Soil Samples Hallmark Your #3975 -B--SC, MJS&A #044733L4B 26-May-04 Sample ID Lot .' FG.. Resistivity Units as received ohm cm 120000 saturated . ohm-cm 410 :. . . . .• OH. 49 Electrical Conductivity ms/cm 1.12. Chemical Analyses Cations calcium Ca2" mg/kg 289 magnesium . M 2' mg/kg' '112 . ..' . . sodium Na mg/kg 321 Anions carbonate CO32 mg/kg ND bicarbonate HCO3' mg/kg ND chloride - CI mg/kg. . S . 255 .....', . . . -. . sulfate SO42 mg/kg 1,459 Other Tests ammonium NH4 mg/kg 11.6 nitrate N031 mg/kg L8 2 sulfide S qua I` na Redox mY : na Total Acidity 1-1" mg/kg 480 Electrical conductivity in millisiemens/cm and chemical analysis were made on a 1:5+ soil-to-water extract mg/kg = 'milligrams per kilogram (parts per million) of dry soil. ' .. Redox = oxidation-reduction potential in millivolts ND = not detected na = not analyzed' Page 1 of 1