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HomeMy WebLinkAboutCT 13-06; LA COSTA VILLAS; GEOTECHNICAL OBSERVATIONS & COMPACTION TESTING; 2015-02-17SMS GEO TECHNICAL SOLUTJONS, INC. Consulting Geotechnical Engineers & Geologists 1465 S Rancho Santa Fe Road Suite 208 San Marcos, California 92078 Office: 760-761-0799 Cell: 760-3314738 smsgeosoLinc@gmail.com Project No. FC-12-14-33 February 277 2015 MBM Development, Inc. Mr. Majid Mortazavi 1608 Lake Drive Cardiff, California 92007 Report of Geotechnical Engineering Observations and Compaction Testing, Remedial Building Pad Grading, La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad, California (Drawing No 483-2A) Submitted herewith please find the following summary of geotechnical engineering observations and compaction testing recently completed by our firm in connection with remedial grading and ground preparation for the graded building pad at the above-referenced property. The building pad at the property is delineated on the enclosed Limits of Compacted Fill and Field Test Location Map reproduced from the project Grading Plan prepared by ACE Civil Engineering The project consisted of an export grading operation. Overall grading designs for the project I development chiefly consisted of cut excavations into pre-existing graded slopes on the south and east perimeters for enlarging the pad surfaces, and the creation of level stepped surfaces for the support of an 8-Unit condominium type residential construction..Terraced site and building basement type retaining walls are incorporated into the designs to achieve ground transitions from upper on & off site grades to lower building pad grades near the adjacent Gibraltar Street. I. REFERENCES The following pertinent plans and documents were used a basis of our engineering observations and I compaction testing services. 1 Grading Plans for La Costa Villas, Drawing No 483-2A, prepared by ACE Civil I Engineering. I 2 "Addendum Geotechnical Plan Review Update, Proposed La Costa Villas Development, Gibraltar Street at Jerez Court, Carlsbad, California," prepared by SMS Geotechnical Solutions, Inc., Project No. 01-9-14-18, dated September 9, 2014. I I Ii Report of Géotechnical Engineering Observations and Compaction Testing Page 2 I La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 "Second Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi- Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by I Allied Earth Technology, Project No. 13-1147H1, dated June 2014. 4. "Update of Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit I Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, California," prepared by Allied Earth Technology, Project No. 13-1147H 1, dated October 10, 2013. I 5 'Preliminary Geotechnical Investigation Update Report, Proposed Multi-Unit Attached Dwellings, Gibraltar Street at Jerez Court, La Costa, Carlsbad," Prepared by Vinje & Middleton Engineering, Inc., Job #04-287-P, dated July 7, 2004 This report was completed under the engineering supervision of the undersigned while employed at the Vinje & Middleton Engineering, Inc. :6. 'Preliminary Soil and Geotechnical Investigation, Graded Hillside Property, Gibraltar Street Near Jerez Court, La Costa Area of Carlsbad, San Diego County, California," prepared by MV Engineering, Inc. Job #1017-91, dated February 20, 1991 II. GEOTECHNICAL CONDITIONS Surface conditions at the project Lot 401 substantially remained unchanged from. those described in the referenced reports However, exposures developed in the pad over-excavations and wall backcut excavations indicated that property was mostly a graded fill pad with perimeter fill slopes Formational bedrock units were exposed below the site fills ranging from approximately 3 to 8 feet in the building pad areas to roughly 10 to 12 feet in the eastern (upper) wall area Site pre-existing fills consisted of light to dark brown silty to sandy clay soils grading medium stiff to very stiff with depth Underlying formational units consisted of dense to stiff light to tan brown clayey sandstone- siltstone designated as the Santaigo Formation (isa). Formational rocks (Td) were exposed in the foundation trench excavation for the eastern (upper) retaining wall with the wall foundations and shear key embedded into the undisturbed natural formational materials. The upper portion of the formational material was marked by a dark colored stiff clayey residual soil that graded to a lighter colored mottled clayey sandstone-siltstone More prominent natural clayey residual soils exposed directly at the bottom of the foundation trench in the southern and northern ends were over-excavated to a minimum depth of 12 inches and reconstructed to the bottom of the foundation elevation with compacted fills similar to the remaining trench areas to create a uniform bearing conditions through (see enclosed Nat). :No indication of adverse geologic structure or instability was in evidence in the temporary wail backcut exposures However, pre-existing shallow slump type failures impacted the slope face above the temporary wall backcut, as mapped on the enclosed Limits of Compacted Fills and Test Location Map The slump failure debris was removed and irregular slope face surfaces in the impacted areas laid back and benched in order to enhance stability of the temporary wall backcut Sippe face slump failure areas should be repaired by proper benching into unaffected hillsides as Report of Geotechnical Engineering Observations and Compaction Testing Page 3 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 approved in the field, and backfilling with compacted fills during the wall backfill operations to achieve original or flatter slope gradients. The reconstructed slope face should be blended into surrounding terrain to provided a smooth transition More detail recommendations are provided m the following sections. ilL GROUND PREPARATION AND REMEDIAL GRADING Prior to the remedial grading operations, surface vegetation was removed and cleared for the site as appropriate Upper soft and compressible soils were then stripped and removed from the areas receiving new fills to expose the underlying undisturbed natural dense to stiff formational units, or firm ground, but not less than 3 feet below rough finish pad grades throughout The exposed bottom surfaces were then visually examined, probed and tested to assure stable ground or competent formational units suitable for receiving new fills Earth deposits generated from the site remedial grading operations predominantly consisted of silty to sandy clay (CL) soils ranging high expansion potential The removed soils were moisture conditioned to above (approximately 2%-3%) optimum moisture levels, processed into a umform mixture placed m thin 6 to 8 inches thick horizontal lifts and mechanically compacted with heavy construction equipments consisting of D-4 Bulldozer, 938 Loader and 321 Excavator, to at least 90% of the corresponding laboratory maximum density per ASTM D-1557 Approximate bottom of over-excavation elevations are shown on the enclosed Approximate Limits of Compacted Fills and Test Location Plat and Compaction Test Results Table Periodic engineering observations of the remedial grading Operations and compaction testing of the fills placed within the graded areas were provided by this office from January 9 through February 18, 2015 Limits of remedial grading works, approximate test locations and pertinent elevations as established in the field based on information provided by others, are shown on the enclosed Approximate Limits of Compacted Fills and Test Location Plat Approximate elevations and locations of field density tests were determined by hand level and pacing/tape measure relative to identifiable features located at the site and noted on the grading plan. Pertaining maximum dry density and optimum moisture content tests (ASTM D1557) were obtained from prior site geotechmcal investigations reports (see references) and are summarized in the enclosed Compaction Test Results Table Site preparation and remedial grading were conducted in substantial conformance with Chapter 18 (Soils and Foundations) and Appendix "J" (Grading) of the 2013 California Building Code (CBC), the Grading Ordinance for the City of Carlsbad, the requirements of the project soil report(s) referenced herein and our field recommendations, where applicable and as appropriate All observations and testing were conducted by a representative from this office under direct supervision of the project geotechnical engineering/engineering geologist Field. density tests establishing both the in-place dry densities and moisture contents were performed in accordance with the ASTM D-1556 sand cone test method as the fill was placed. Test locations were placed to provide the best possible coverage. Areas of low compaction, as indicated by the field density tests, were brought to the attention of the contractor. These areas were reworked by the contractor and retested. Engineering observations and compaction test results indicated that the Report of Geotechnical Engineering Observations and Compaction Testing Page 4 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 fills within the approved areas were properly placed. and compacted to at least 90% of the corresponding maximum dry density at the tested locations and are suitable for their intended use ADDITIONAL LABORATORY TESTING One expansion index (El) test was performed during this phase of the project on a representative 50%-50%.rnixture of onsite soils with sandy import soils in accordance with the ASTM D-4829 to determine suitability of the mixtures for use as wall back material The test results are presented in the following table. Sample Description Molded Degree Of Saturation (%) Final (%) Initial Dry Density (PCF) Measured El El 50/0 Saturation Onsite/irnport5ol5Omixture 11 :50 23 105.1 .44 1 44 () moisture content in percent. E150 =Ehneas - (50 - Smeas) ((65 + Elmeas) (220 - Smeas)) Expansion Index (El) Expansion Potential 0-20 :Very Low 21-50 Low 51-90 Medium 91-130 High >130 Very High CONCLUSIONS AND RECOMMENDATIONS In our opinion, site excavations and remedial grading operations were completed in substantial conformance with the project approved grading plan, pertinent geotechnical reports and applicable codes, and are acceptable for their intended use Site subsurface geotechnical conditions were found to vary from those described in the referenced reports, as presented herein. However, earth materials and engineering properties of the compacted fills remain the same Permeable Interlocking Concrete Payers (PIGP) type pavements are proposed for the interior driveway improvement surfaces as shown on the project grading plans (see Limits of Compacted Fill and Field Test Location Map) The proposed PICP pavement sections as shown on the project plans are acceptable from a geotechnical standpoint provided our recommendations presented in the following are also considered and incorporated into the project designs and constructions Onsite clayey (CL) deposits are not suitable for wall and trench backfills and good quality sandy granular import soils should be considered for this purpose, or used to improve the quality of the onsite soils to an acceptable (El less than 50) mixture Report of Geotechnical Engineering Observations and Compaction Testing Page 5 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 A small load of sandy soils was imported to the site and was mixed "50-50" with the onsite soils and tested in accordance with ASTM D-4829. Test results indicated a low expansion potential with an expansion index (El) of 44 The mixture is considered suitable for use as wall backfihls Additional sandy import soils necessary to improve the quality of the onsite soils, or where used for wall and trench backfills should be good quality clean, granular, non-corrosive deposits (SM/SW) with very low expansion potential (100% passing 1-inch sieve, more than 50% passing #4 sieve and less than 18% passing 4200 sieve with expansion index less than 20). Import soils should be inspected, tested as necessary, and approved by the project geotecimical engineer prior to delivery to the site Import soils should also meet or exceed engmeering charactenstic and soil design parameters as specified in the following sections. All conclusions and recommendations including soil design parameters, •geoteclmical foundation/slab designs and improvement sections provided in the referenced reports and subsequent I letters and addendums will stay unchanged, as specified therein and should be considered in the final designs and implemented during the construction phase, except where specifically superceded below:. I A. Footings and Slab-on-Grade Foundations I The proposed residential units may be supported on shallow stiff concrete footings and slab- on-grade floor foundations designed based upon the as-graded engineering properties of foundation bearing and subgrade soils. Other foundation system alternatives such as post- tensioned or structural slab-on-ground foundations consistent with the onsite high expansive soils are also available The choice of appropriate option will depend on acceptable levels of future building and improvement performance, economic feasibility and ease of - construction. - Site earth bearing and subgrade soils predominantly consist of silty to sandy clay (CL) I deposits ranging to high in expansion potential (expansion index of 98 based on ASTM D-4829 classification) Expansive soils will require adequate moisture conditioning, deeper foundations and thicker slabs with heavier reinforcement in order to alleviate their potential I adverse impacts. The following minimum foundation and slab recommendations are consistent with the site clayey bearing and subgrade soils: I 1. Perimeter and interior continuous strip foundations should be sized at least 18 inches wide and 24 inches deep Spread pad footings, if any, should be at least 30 inches square and 18 inches deep and structurally interconnected with the continuous strip footings with grade beams. Interconnecting grade beams should be a min imum of 12 inches. wide by 18 inches deep Footing depths are measured from the lowest adjacent ground surface, not including the sand/gravel layer beneath floor slabs. I Exterior continuous footings should enclose the entire building per imetet. Flagpole footings also need to be tied together if the footing depth is less than 4 feet below rough I finish grade. LIII Report of Geotechnical Engineering Observations and Compaction Testing Page 6 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 Continuous interior and exterior foundations should be reinforced, with a minimum of four #5 reinforcing bars. Place 245 bars 3 inches above the bottom of the footing and 245 bars 3 inches below the top of the footing. Interconnecting grade beams should also be reinforced with a minimum of 244 bars top and bottom and #3 ties at 30 inches on center maximum Reinforcement details for spread pad footings should be provided by the project architect/structural engineer, Deepenedfoundations shall be requiredfor all building walls adjacent to the internal driveway with Permeable Interlocking Concrete Paver (PICP) type pavement surfaces Deepened foundations adjacent to the internal driveway shall be a minimum of 30 inches deep or extend a minimum of 12 inches below the bottom of the paver section, whichever, is more Unit 1 western building foundations adjacent to the detention basin retaining walls should also be adequately deepened to avoid surcharging of the lower walls (a 1:1 projected line from the bottom outside edge of the building foundations shall be below the bottom of lower wall) The slab subgrade andfoundation'bearing soils should note allowed to dry prior to pouring the concrete or additional groundpreparations, moisture reconditioning and pre saturation will be necessary as directed in thefiekL The required moisture content of the bearing soils is approximately 3% over the optimum moisture content to the depth of 24 inches below slab subgrade Attempts should be made to maintain as-graded moisture contents in order to preclude the need for pre saturation of the subgrade and bearitg soils. Dowel the slab to the footings using #4 reinforcing bars spaced 18 inches on center I maximum extending at least 20 inches into the footing and 20 inches into the slab. The dowels should be placed mid-height in the slab Alternate the dowels each way for all interior footings. I 5 After the footings are dug and cleaned, place the reinforcing steel and dowels and pour the footings. This office should be notified to inspect the foundation trenches and I reinforcing prior to pouring concrete. Once the concrete for the footings has cured and underground utilities tested, place 4 I inches of 3/a-inch rock over the slab subgrade Flood with water to the top of the %-inch rock, and allow the slab subgrade to soak until moisture testing indicates that the required moisture content is present. After the slab subgrade soils have soaked, notify I this office and schedule for appropriate moisture testing. When the required moisture content has been achieved, place, a well-performing moisture I barrier/vapor retardant (minimum 15-mil Stego) over the %-inch rock, and place 2 inches of clean sand (SE 30 or greater) on top of the plastic. I I Report of Geotechnical Engineering Observations and Compaction Testing Page 7 La Costa Villas Project, Lot 401,7570 Gibraltar Street, Carlsbad February 27,2015 If sufficient moisture is present, flooding/pre saturation will not be required and slab underlayment may consist of 2 inches of clean sand (SE 30 or greater) over a well performing moisture barrier/vapor retardant (minimum 15-mil Stego) over 2 inches of clean sand, and thefootings and slab may be poured monolithically. Alternatively, a 4-inch thick base of compacted Y.—inch clean aggregate provided with the vapor barrier (minimum 15-mil Stego) in direct contact with (beneath) the concrete may also be considered provided a concrete mix which can address bleeding, shrinkage and curling is used This office should be notified to inspect the sand, slab thickness, and reinforcing prior to concrete pour. - 6. Adequate setback or deepened foundations shall be required for all foundations constructed on or near the top of descending slopes to maintain, minimum horizontal distances to daylight or adjacent slope face There should be a minimum of 7 feet or ½ of the slope height, 'whichever is more, horizontal setback from the bottom outside edge of the footing to daylight for foundations, unless otherwise specified or approved. 7 All interior slabs should be a minimum of 5 inches in thickness reinforced with #3 reinforcing bars spaced 12 inches on center maximum each way placed near the slab mid-height. I Interior slabs should be provided with "soficut" contraction/control joints consisting of sawcuts spaced 10 feet on center maximum each way. Cut as soon as the slab will support the weight of the saw, and operate without disturbing the final finish which is I 2 ho after final, finish at each control joint location or 150 psi to 800 psi The softcuts should be a minimum of 1-inch in depth, but should not exceed 11/4- inch deep maximum. Anti-ravel skid plates should be used and replaced with each blade I to avoid spalling and raveling. Avoid wheeled equipment across cuts for at least 24 hours. I 8. Provide re-entrant corner reinforcement for all interior slabs. Re-entrant corners will depend on slab geometry and/or interior column locations. The enclosed Isolation Joint I and Re-Entrant Corner Reinforcement (Plate 1) may bed as a. general guideline. 9 Foundation trenches and slab subgrade soils should be inspected and tested for proper moisture and specified compaction levels and approved by the project geotechmcal consultant prior to the placement of concrete. :10. All soil design parameters will remain the same as specified in the referenced reports. I I Report of Geotechnical Engineering Observations and. Compaction Testing Page 8 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 B. Eastern Slope Face Repairs and Restorations Shallow slump type failures impacted the slope face above the temporary wall backcut at the southeast corner, as mapped on the enclosed Limits of Compacted Fills and Test Location Map The slump failure debris was removed and irregular slope face surfaces in the impacted areas laid back and benched in order to enhance stability of the temporary wall backcut No indication of adverse geologic structure or instability was in evidence in the temporary wall backcut exposures. The local slope face erosional slump failures are thought to have chiefly resulted from previous uncontrolled drainage run-off above that concentrated over the slope surfaces. Lack of periodic maintenance and clearing of slope face drainage terraces and failure of concrete ditches are also thought to have caused slope face saturations and may be the initiating factor of the slope face slumping Slope face soils are also in a soft condition Slope face slump failure areas should be repaired by proper benching into unaffected hillsides as approved .in the field, and backfihling with compacted fills during the wall backfill Operations to achieve original or flatter slope gradients. The reconstructed slope face should be blended into surrounding terrain to provided a smooth transition. The following are appropriate: Remove and clear all vegetation from the repair areas, where they occur and as necessary. Clean out existing level benches/steps developed during grading operations tolay back impacted portions of the slope face, and further remove additional all slump debris and failed soils, where they occur, as necessary. Levels benches should at least 2 feet wide, expose firm unaffected soils and slightly heeled back into the hillside Backfill soils should consist of the "50-50" onsite-import soil mixture generated for wail backfihls, pre-manufactured into a well processed and moisture-conditioned mixture prior to the actual placement. The backfill soils should be moisture conditioned to approximately 2% above the optimum moisture levels, throughly mixed and processed into a uniform and homogeneous blend as approved in the field by the project geotechmcal engineer or his designated representative Mechanically compact pre-manufactured backfill soils upon level benches approved by the project geotechmcal consultant m thin (4 to 6 inches) horizontal lifts to minimum 90% of the laboratory maximum dry density (per ASIM D-1557) using hand held equipments (whacker or similar). The reconstructed embankment should be compacted to minimum 90% compaction levels out to the finish slope face and neatly blended into the surrounding areas. I Report of Geotechnical Engineering Observations and Compaction Page 9 La Costa Villas Project, Lot 401, 7570 Gibraltar Street. Carlsbad 27.2015 Slope face restorations and recompaction operations should be inspected and tested by project soils engineer to verify minimum 90% compaction levels within the slope face materials in the repair areas Testing of fill will also assist the contractor to achieve proper moisture and compaction levels. Slopeface repair and restoration geotechnical inspection and compaction testing should be completed as part of the wall backfill testing work and presented in a separate Wall Backfill and Slope Repair and Restoration compaction Report. Controlling slope face surface drainage is an important factor in the overall stability and future performance of the project hillside This can be achieved by improving the slope face drainage and disallowing concentrated run-off from above Surface runoff over the slope surfaces should also not be allowed to saturate the soils within the outer embankment face or percolate into the hillside, and should be collected and directed in a controlled manner. Overflow of the upper (off site) pad surface water from the top of the slope should be avoided. Slope face drainage terraces and concrete lined drainage swales behind the retaining walls should collect and divert surface water to suitable discharge locations Period maintenance and upkeep of site drainage facility shall be required to assure continued popper and unobstructed functioning of all surface and subsurface drainage facilities. The completed slope face should be provided with a suitable plant cover. Natural brush is best but difficult to quickly establish Initially, only broad-leafed, deep rooted vegetation which requires a minimum of irrigation should be used Over watering of site vegetation should be avoided Only the amount of water to sustain vegetation life should be provided. A well -qualified landscape architect should be consulted for this purpose. Eastern Slope Face Contour Cut Grading The existing concrete ditch near the top of the temporary wall backcut is planned for removals and replacement with a new concrete-lined drainage ditch directly behind the wall, as shown on the enclosed Limits of Compacted Fill and Field Test Location Map (also see the project final grading plan) Upon removal of the existing concrete ditch, the disturbed slope face areas may be contour cut graded to provide a smooth transition and blend into the surrounding areas Finish slope face should expose firm and competent stable surfaces, as approved in the field Unfavorable slope face exposures will require stabilization including reconstruction with compacted fills upon level benches as discussed herein or compacting the slope face exposures to enhance surficial stability as directed in the field Slope face drainage improvements, maintenance, and plant cover remains the same as specified. Permeable Interlocking Concrete Payers (PICP) Permeable Interlocking Concrete Payers (PICP) are planned for the internal driveway improvement surfaces as a part of the project BMP designs, as shown on the grading plans (see Plate 1). The proposed PICP pavement sections as shown on the project plans are Report of Geotechnical Engineering Observations and Compaction Testing Page 10 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27,201$ considered substantially acceptable from a geotechnical standpoint provided the following are also considered and incorporated into the design and construction of the proposed permeable/previous paving surfaces: In general, infiltrated water through the PICP pavements shall not impact the driveway :subgrade and nearby building foundation bearing soils, adjacent 'wall backfihls and nearby graded embankments. For this purpose, under drains perforated pipes (Sch. 40 or greater) placed approximately 3 inches above the bottom of pavement base course (ASTM No 57 stone) should be installed Due to the site highly moisture sensitive plastic clayey subgrade soils and very close proximity of the building foundations to the permeable driveway pavements, an impervious liner (minimum 15-mil Stago) should be provided at the bottom ofpavement base course (4STMN6. 57 stone) over the approved compacted subgrade Saturation of site clayey soils will result in loss of strength and periodic heaving and shrinkage can occur in response to wetting and drying and shall not be allowed Outlet box structures which capture and discharge the infiltrated runoff via the storm drain pipes to the designated locations are critical components of the pavement system. Planned PICP pavements should be provided with thickened concrete curb/edge restraintS, as necessary and appropriate. Deepened building and wall foundations shall also be necessary where they occur near or adjacent (less than 15 feet) to the permeable pavements or site bioretention basin Other similar protective measures such as :miflimum 3 sack concrete slurry cutoff walls may also be considered along the edges of the proposed PICP pavements and bioretention system near the project building and wall foundations. PICP pavement structural section will depend to storage and infiltration capacity of the system, as well as engineering properties of subgrade soils, and should be provided by the project design consultant From a geotechmcal engmeermg standpomt, based on our analysis and design assumptions (R-Value of 5 and TI of 4 5) as a minimum PICP pavement section should consist of 3 ½-inch PICP over a minimum of 2 inches ofASTM No 8 bedding course/choke stone over a minimum of 12 inches of ASTM No 57 stone base course over a minimum of 12 inches of 95% compacted subgrade. R-Value testing of subgrade soils may also be performed toconfimn structural section designs. Bedding course /choke stone and base course stone should also be well compacted, consolidated and interlocked (avoid crushmg the under drain pipes) with heavy construction equipment (minimum 95%) ASTM No 8, No 9 or No 89 should be used for joint materials depending on the joint size and per manufacturer recommendations Gradation requirements for ASTM No. 57, No. 8, No, 89 and No. 9 are as follows: Report of Geotechnical Engineering Observations and Compaction Testing Page 11 La Costa Villas Project, 'Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 Sieve Size Percent Passing . No. 57 No.8 No. 89 No.9 11/2 100 1" 95to100 ½" . 25 to 60 '100 100 85 to 100 90 to 100 100 No.4 OtolO 10to30 20to55 85to100 No.8 0to5 OtolO 5to30 lOto4O No. 16 . 0 to 5 0 to 10 0 to 10 No. 50 . 0to5 0to I ,5 Pervious concrete pavement section, if considered, should consist of a minimum of 8 inches thick pervious concrete (modulus of rapture of 600 psi) over a minimum of 6 inches of ASTM No 57 stone base course over a minimum of 12 inches of 95% compacted subgrade, as indicated on the project plans, is considered adequate. The need for an impervious liner at the bottom ofpavement base course (ASTMNo. 57 stone) I over the compacted subgrade will remain the same as specified. 6. A concrete transition strip should be provided between the project asphalt, PICP and - pervious concrete pavements and around the perimeter of the PICP installations E. Exterior Concrete Slabs.! Flatworks 1.. All exterior slabs (walkways, patios) supported on highly expansive subgrade soils should be a minimum of 4 inches in thickness, reinforced with #3 bars at 12 inches on centers in both directions placed mid-height in the slab The subgrade soils should be compacted to minimum 90% compaction levels at the time of fine grading and before placing the slab reinforcement. In order to enhance performance, of exterior slabs and flatworks supported on potentially expansive and moisture sensitive subgrade soils, a minimum 8 inches wide by 12 inches deep thickened edge reinforced with a minimum of 144 continuous bar near the bottom should be considered along the slab perimeter. Tying the slab panels to adjacent curbs, where they occur, with #3 bars at 12 inches on centers, may also be considered. I I Lii I I] Report of Geotechnical Engineering Observations and Compaction Testing Page 12 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 Reinforcements lying on subgrade will be ineffective and shortly corrode due to lack of adequate concrete cover. Reinforcing bars should be correctly placed extending through the construction joints tying the slab panels In construction practices where the reinforcements are discontinued or cut at the construction joints, slab panels should be tied together with minimum 18 inches long #3 dowels (dowel baskets) at 12 inches on centers placed mid-height in the slab (9 inches on either side of the joint). Provide "tool joint" or "softcut" contraction/control joints spaced 10 feet on center. (not to exceed 12 feet maximum) each way. The larger dimension of any panel shall not exceed 1256/o of the smaller dimension Tool or cut as soon as slab will support weight, and can be operated without disturbing the final finish which is normally within 2 hours after final finish at each control joint location or 150 psi to 800 psi Tool or softcuts should be a minimum of 1 -inch but should not exceed 1 V4-inch .deep maximum In case of softcut joints, anti-ravel skid plates should be used and replaced with each blade to avoid spalling and raveling. Avoid wheeled equipments across cuts for at least 24,hours. Joints shall intersect free-edges at a 900 angle and shall extend straight for a minimum of 1 Meet from the edge The minimum angle between any two intersecting Joints shall be 80° Align joints of adjacent panels Also, align joints in attached curbs with Joints in slab panels Provide adequate curing using approved methods (curing compound maximum coverage rate = 200 sq. ft./gal.). Subgrade soils should be tested for proper moisture and specified compaction levels and approved by the project geotechnical consultant prior to the placement of concrete. V ADDITIONAL GEOTECHNICAL OBSERVATIONS AND TESTING This office should be notified no later than 2 p.m. on the day before any of the following operations be in order to schedule appropriate testing and/or field observations for confirmation and approval of the completed work: A. Wall Bacldills Observe -wall back drain installations in substantial accordance with the enclosed Retaining wall Drain Detail, Plate 2 The crushed rock backfill zone should be well consolidated and interlocked by mechanical/hand-operated equipments and construction tools suitable to the site conditions. Wall backfill soils shall be compacted by mechanical means to .a minimum of 90% of the corresponding maximum dry density, unless otherwise specified Good quality sandy import soils or "50-50" manufactured mix should be used I I I Report of Geotechnical Engineering Observations and Compaction Testing Page 13 La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 B. Foundations and Utift Trenches Observe the plumbing and utility trenches after the pipes are laid and prior to backfihling. Backfill soils within trenches 12-inches or more in depth shall be compacted by mechanical means to a minimum of 90% of the corresponding maximum dry density, unless otherwise specified Good quality sandy import soils or "50-50" manufactured mix should be used Jetting or flooding of the backfill is not allowed Care should be taken not to crush the utilities or pipes during the compaction of the trench backfill Test the plumbing trenches beneath slabs for minimum compaction requirements prior to sand and moisture barrier placement. Observe the bottom of the footing trenches for proper embedment, compaction levels, and design widths and embedment. .4. Confirm footing reinforcement size and placement, slab thickness and reinforcing,sand thickness and moisture barrier placement. C. Fine Grading, Pavement Base and Subgrade and Site Improvements L Observe placement and perform compaction testing for fills placed under any conditions 12-inches or more in depth, to include: Building pad contour grading. Driveways, Street and yard improvements, sidewalks, curbs and gutters. The spreading or placement of soil obtained fom any excavation (spoils from footings, underground utilities, swimming pools, etc.).. Observation and testing of base and .subgrade beneath the driveway, perimeter yards, patios, sidewalks, etc., prior to placement of pavement surface or concrete. Moisture testing prior to concrete pour, if required and as specified. Any operation not included herein which requires our testing, observation, or. conformation for submittal to the appropriate agencies. VI. DRAINAGE I The ownerideveloper is responsible for insuring adequate measures are taken to properly finish grade the building pad after the structures and other improvements are in-place so that the drainage 'waters from the improved site and adjacent properties are directed away from I proposed structures in accordance with the designed drainage patterns shown on the approved plans. I I Report of Geotechni cal Engineering Observations and Compaction Testing Page 14 I La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February, 27, 2015 A minimum of 2% gradient should be maintained away from all foundations Roof gutters and downspouts should be installed on the building, all discharge from downspouts should I be led away from the foundations and slab to a suitable location Install area drains in the yards for collection and disposal of surface water. Planter areas adjacent to foundations should be provided with damp/water proofing, using an impermeable liner against the footings, and a subdrainage system within the planter area Site and building stem type retaining walls should be provided a well-constructed back dram as specified in the project soil reports Planting large trees behind site retaining walls should be avoided. I It should be noted that shallow groundwater conditions may develop in areas, vhere no such conditions existed prior to site development This can be contributed to by substantial I increases of surface water infiltration resulting from landscape irrigation which was not present prior to the site redevelopment It is almost impossible to absolutely prevent the possibility of shallow water conditions developed from excessive landscape irrigation over the entire site Therefore, we recommend that shallow water conditions, if developed, be I immediately remedied. The property owner should be made aware that altering drainage patterns, landscaping, the I addition of patios, planters, and other improvements, as well as over-irrigation and variations in seasonal rainfall, all effect subsurface moisture conditions, which in turn affect structural I performance. VII EXPANSIVE SOIL AND DRAINAGE MAINTENANCE CLAUSE Onsite hearing and subgrade soils consist of highly expansive moisture sensitive silty to sandy clayey (CL) soils. These deposits can experience movements and undergo volume changes upon wetting and drying which can be detrimental to the site improvements and structures Building foundations/slabs and site improvement recommendations provided herein are provided with the intent to alleviate adverse impacts of site potentially expansive I :sojls However, maintaining a uniform as-graded soil moisture during the post construction periods is essential in the future performance and stability of site structures, embankments and improvements. Drainage improvements should be installed and well-maintain and water i intrusions into the site clayey bearing and subgrade soils prevented. A maintenance program for continuous inspections and upkeep of the project surface and subsurface drainage facilities, as well as the retention basin will be required to assure proper functioning and uninterrupted continuous discharge flow of the captured runoff water as specified. A maintenance schedule consisting of at least two times a year, before and after I the annual rainy season is recommended. In case of deficiencies , noted conditions should be immediately repaired. Development Of an unfavorable condition, if noted during the scheduled maintenance should also be to the attention of the project consultant to provide I appropriate mitigation recommendations. P I Report of Geotechnical Engineering Observations and Compaction Testing Page 15 I La Costa Villas Project, Lot 401, 7570 Gibraltar Street, Carlsbad February 27, 2015 VIII. LIMITATIONS I Our description.of grading operations, as well as observations and testing services herein, has been limited to those pad remedial grading operations performed periodically from January 9 to February I 18, 2015. The recommendations provided herein have been based on our field observations and testing as noted No representations are made as to the quality or extent of materials not observed and tested. This report is issued with the understanding that the owner or his representative is responsible for ensuring that the information and recommendations are provided to the project architect/structural engineer and other design consultants so that they can be incorporated into the plans Necessary steps shall be taken to ensure that the project general contractor and subcontractors carry out such recommendations during construction. This report should be considered valid for permit purposes, for a period of six• months and is subject to review by our firm following that time. IFANYCJL4NGESAREMADEIN THE FINAL PAD SIZE, LINESAND GRADES, B UILDINGLOCA TION, ELEVATIONS, ETC .,PRIOR TO THE CONSTRUCTION, THIS REPORT WILL BECOME INVALID AND FURTHER ENGINEERING AND RECOMMENDATIONS WILL BECOME NECESSARY. If you have any questions or need clarification, please contact this office at your convenience. Reference to our Project No FC-12-14 -33 will help to expedite our response to your in quines We appreciate this opportunity to be of service to you, Steven' J. Meizer CEO #2362 Plate 1, Isolation Joint and Reinforcement Plate 2., Retaining Wall Drain Detail Compaction Test Results Approximate Limits of Compacted Fills and Test Location Map Distribution: Addressee (5, e-mail) ACE Civil Engineering (e-mail) .SMS GEOTECHNICAL SOLUTIONS, INC, Consulling Geotechnicai Engineers & GeoIogist (a) ( b) ISOLATION JOUTS CONTRACTION JOIN (c) ENTRANT NER CRACk RE-ENTRANT C REINFORCEMEN NO. 4 BARS Pt BELOW TOP O ISOLTION JOINTS AND RE-ENTRANT CORNER REINFORCEMENT Typical - no scale NOTES: Isolation joints around the columns should be either circular as shown in (a) or diamond shaped as shown in (o) [-,'no isolation joints are used around columns or it the corners of the isolation joints do not meet the contraction joints, radial cracking as shown in (c)may occur (reference Ad). In order to control cracking at the re-entrant corners (±2700 corners), provide reinforcement as shown in (c). Re-entrant corner reinforcement shown herein is provided as.a general guideline only and is subject to veriftation arid chanoes by the project architect and/or structural engineer based upon slao geometry locatior arid other engineeiria and construction factors. SMS GFLOTECHN!CAL SOLUTIONS. INC- Consulting Geotechnical Engineers & Geologists PLATE 1 CONSTRUCTION SPECIFICATIONS 1 Provide granular, ñon-expansive backfill soil in 1:1 gradient wedge behind wall. Compact backfill to minimum 90% of laboratory standard. 1 I I I I I I I . I 1. I RETAINING WALL DRAIN DETAIL Typical - no scale drainage Granular, non - expansive / backfill Cornaced ,, ,' Waterproofing - Filter Material Crushed rock (wrapped in filter fabric) or Class 2 Permeable Material Perforated drain pipe / U' (see specifications below) Competent, approved soils or bedrock I 2. Provide back drainage for wall to prevent build-up of hydrostatic pressures. Use drainage openings along base of wall or back drain system as outlined below. I Backdrain should consist of 4 diameter PVC pipe (Schedule 40 or equivalent) with perforations down Drain to suitable outlet at minimum 1% Provide % 1½ crushed gravel filter wrapped in filter fabric (Mirafi 140N or equivalent) Delete fitter fabric wrap if Caltrans Class 2 permeable material is used. Compact Class 2 material to minimum 90% of laboratory standard. I 4. Seal back of wall with waterproofing in accordance with architect's specifications. 5 Provide positive drainage to disallow pondring of water above wall. Lined drainage ditch to minimum 2% flow away from wall is recommended. Use 1% cubic foot per bot with granular back-fill soil and 4 cubic foot per fopt if expansive backfill soil is used. - - - - - - - - - - - - - - - - - - - COMPACTION TESTRES(JL TS PROJECT NO: . FC -12-14-33 PROJECT NAME: La Costa Villas, Lot 401, Building Pad Gradiñg(CT13-06, Drawing No. 483-2A) PROJECT LOCATION 7570 Gibraltar. Street, Carlsbad, California LABORATORY MAXIMUM DRY. DENSITY/OPTIMUM MOISTURE CONTENT TEST RESULTS '(ASTM D1557): Soil Type (1): Light Brown to Tan 'Clayey Sand to Sandy Clay Soil Type" (2).: Light to Dark Brown silty sandy Clay Maximum Dry Density: 115.7 pcf Maximum Dry Density 114.5 pcf Optimum Moisture: 15% Optimum Moisture: 16% FIELD COMPACTION TEST RESULTS .(ASTM D1556): Date .2015 Test No. .. Location . Approximate Test .. . Elevation Field . . . .. Moisture (%) Field. Dry . . . Density Max: Dry . . Density Relative . .... Compaction (°/) Comments 1/9 1 1 Keyway, NW Corner of Unit I . .86i 14 1.06.6 114.5 93 Bottom of Over-ExcavatiOn @86.0' 1/9 2 NW. Area, B/W Detention Basin & Driveway . 89 16. 105.2 114.5 92 1/9 3 Detention-Basin 90 . 15: 106 .' 114.5 93 1/9 4 Unit 1 91 16 103.9 . 114.5 91 Bottom of Over-Excavation @ 89.5' 1/12 5 Unit.2 91.5 17 :107.1 1145 94 . . . . ... .. 1/12 6 Unit 3 90 17, 105.9 114.5 92 . Bottom of Over-Excavation @ 88.5' 1/12 7 Unit 4 92 15 106 .1, 114.5 93 Bottom of Over-Excavation @90 5 1/12 '8 Driveway, B/W Units I & 5 92 16 106.7 114.5 93 Bottom of Over-Excavation.@ 91.0' 1/12 9 Unit 2 . 93: 17 104.1 1.14.5 91 1/13 '10 Unit 93 . 16 104.9 1j4.5 92 1/13 11 Unit 1 94 17 105.7 1.14.5 92 .1/13 .12 Unit 4 94 16 1.06.3 . 114.5 93 Bottom ofOver-Excavation.@.93.5' 1/14 , 13 Unit . 95. , 18. 104.8 ' 114.5 92 1/14 14 Driveway, B/W Units 4 & 8 95' 18 104.9 1,14.5 92 ' . .. - - - - - - - = - - - - - - - - - - - Date Date 2015 Test No. Location Approximate Test Elevation (Ft) Field Field Density Dry : (Pei) Moisture Compaction Max Dry Density. ty. Relative (PcI) Comments 1/14 15 Unit 96 17 105.4 114.5 92 1/14 16 Driveway, B/W Units 3 & 7 94 16 107.1 114.4 94 Bottom of Over-Excavation @93.0' 1/15 17 Unit 5 92 18 103.7 114.5 91 Bottom of Over-Excavation @91.5' 1/I5 18 Unit 6 93.0 18 104.8 114.5 92 Bottom of Over-Excavation @92.0' 1/15 19 Uiiit6 94.5 15 107.4 11.4.5 94 1/15 20 Unit 7 93.5 15 106.6 114.5 93 Bottom of Over-Excavation @92.5' 1/15 21 Unit 8 94 16 105 114.5 92 Bottom of Over-Excavation @ 93.5' 1/16 . 22 Unit 5 94.5 16 105.6 114.5 92 Bottom of Over-Excavation @ 91.5' 1/17 23 Unit . 95 18 107.1 114.5 94 1/17 24 Unit 8 . 96 17 1.06.7 114.5 93 Bottom of Over-Excavation @ 93.0' 1/17. 25 S. End .ofE'ly Ret. Wall Fnd. Over-Ex. .107 .1.6 106,8 115.7 92 Over-Ex. Bottom of Fnd. Trench a mm. 12" & Reconst. W/ Comp'd Fill 2/18 26 Unit F.G. 16 105.3 114.5 92 2/18 27 Unit F.G. 16 . 106.6 114.5 93 2/18 28 Unit F.G. 16 106.2 114.5 93 2/18 29 Unit F.G. 17 109 114.5 95 2/18 30 Unit 5 F.G. 17 106.2 114.5 93 2/18 31 Unit 6 F.G. 1.5 106.6 114.5 93 2/18 32 Unit F.G. 17 106.7 .114.5 93 2/18 .33 Unit 8 F.G. 17 105.4 114.5 92 Explanations: Over-Ex. or OX (Over-Excavate), F.G. (Finish Grade). Approximate. test elevations are measured from staking and grading controls provided by others. See attached Approximate Limits of Compacted Fills and Test Location Plat for test locations.