Loading...
HomeMy WebLinkAboutCT 97-13; CARLSBAD OAKS NORTH PHASE 1; FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING; 2006-08-30RECORD cöi77 thth' FINAL RPO6F-TESINGJ AND OBSERVATION SERVICES DURING SITE GRADING CARLSBAD OAKS NORTH BUISNESS PARK - PHASE 1 LdTSI tHfiOUGH CARLSBAD CALIFORNIA: RECEIVED MAR 24 2016 CITY OF CARLSBAD PLANNING DIVISION PREPARED FOR• TECHBILT CONSTRUCTION COMPANY SAN DIEGO, CALIFORNIA AUGUST 30, 2006 PROJECT NO. 06442-32-04A GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS OWN 0 Project No. 06442-32-04A August 30, 2006 Techbilt Construction Company 3575 Kenyon Street : San Diego, Clifomia 92110 Attention: Mr. Raul Güzman S : Subject: CARLSBAD OAKS NORTH BUSINESS PARK— PHASE 1 LOTS 1 THROUGH 9 CARLSBAD, CALIFORNIA FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING Gentlemen: In accordance with your request and our Proposal No. LG-05260 revison dated August 1, 2005, we have provided testing and observation services during grading for Phase 1 of Carlsbad Oaks North Business Park, Lots 1 through 9. The site is located to the west of the intersection of Melrose Drive and Faraday Avenue. The scope of our services included the following: Observing the grading operation including the placement of compacted fill, the removal and/or processing of loose topsoil, alluvial deposits, landslide debris and undocumented fill placed by others; and the undercutting of formational material exposed at or near street subgrade to facilitate utility excavations. In addition, we observed the placement of several subdrain systems to verify proper installation. Performing in-place density and moisture content tests in fill placed and compacted on the pads/lots and associated streets. Performing laboratory tests to aid in evaluating the compaction, shear strength, and expansion characteristics of the soil matetial used as fill. Iii addition, the water-soluble sulfate content of randomly selected samples from finish grade was tested. Preparing an As-Graded Geologic Map. Preparing this final report of grading. 6960 Flanders Drive • San Diego, California 92121-2974 0 Telephone (858) 5584900 N Fax (858) 5584159 . v : The puiose of this report is to document that the grading of the subject business park has been performed in substantial conformance with the recommendations' bf''the piojectgeoteclnic.al report and subsequent consultations and that the All materials have been properly compacted At the time of this report, the grading for LOts 1, 2, and 6 was incOiiir lete and an addendum report will be provided for these lots after completion: In addition, the deIisit tests for prtions of Lots 13 and 14 (Phase 2) that were part of the overall mass grading plan for Phase 1 have also beenincludedherein. . Grading operations fo Phase 1 were performed concurrently with those for El Fuerte Street and 1:? Avenue Geotechnical information relating to the grading of these roads is presented in the following reporis: ... . . . .. . .. . . . .. .. . . •. Final Report of Testingand Observation Services During Roadway ( iading, Carlsbad Oaks North Business Parh, Faraday Avenue Extension - Sta ionl0+00 through 80+80, Carlsb74 California, prepared by Geocon Incorporated, dated July 27, 2006 (Project Nos. 06442-32- 05A and 06442-32-06A). . Final Report of Testing and Observation Services During Site Grading, Carlsbad Oaks North Business Park; El Fuerte Street Extension - Station10+00 through 38+00, Carlsbad, California, prepared by Geocon Incorporated, dated July 13, 2006 (Project No. 06442-32- 08A). .. . An update geotechnical report presenting fine grading recommendations and geotechnical design criteria for the proposed ultimate development should be prepared by Geocon Incorporated Once final plans have been prepared for the individual building pads. GENERAL. The grading contractor for the project was Pinnick Incorporated of El Cajon, California. The project grading plans were prepared by O'Day Consultants, the project civil engineer, and are entitled Grading and Erosion Control Plans for: Carlsbad Oaks North, Phase 1, C. T. 97-13, City of Carlsbad approval dated October26, 2004 (Drawing No. 415-9A). Recommendations for grading were provided in our report entitled Update Geotechnical Investigation, Carlsbad Oaks North, Business Park and Faraday Avenue Offsite, Carlsbad, California, dated October 21, 2004 (Project No. 06442- 32-03). Staking and collection of the field survey information was performed by O'Day Consultants. The exhibit used as a base map to present the as-graded geologic information and hi-place density test locations (Figures 1 through 4) is a copy of a compilation of digital information provided by O'Day Consultants. The map depicts the ultimate grading configuration with respect to lot lines, slope areas, lot numbers, and finish pad elevations. In addition, the existing ground topography prior to grading is shown. The base-of-fill elevations are also presented. This information was collected by surveyors from O'Day Consultants during remedial grading operations. Theas-graded geologic contacts were Project No. 06442-32-04A -2- . August30, 2006 D I I derived from intermittent field survey shots and estimates made by our field representatives based on survey and/or grade-checkers' stakes. In this regard, the contacts should be considered approximate. References to elevations and locatiOns herein are based on as-graded survey information (remedial gradin exhibits) provided by' O'Day Consultants --or gra4e.checkers' stakes in the field..Geocon Incorporated does not provide surveying services and, therefore, has no. opinion regarding the accuracy of the as-graded elevations or surface geometry with respect to the approved grading plans or proper surface drainage GRADING Grading began with iemoving and xpórtiiig brush and vegetation frOththe areas to be graded Topsoil, alluvium, landslide debris, and undocumented fill deposits were then removed to expose formational material. Within areas to receive fill, the exposed soil was then scarified, moisture conditioned and compacted. Fill materials from on-site excavations were then placed and compacted in layers until the design elevations were attained. The areas where hard rock or dense formational material was exposed at, or near street subgrade were undercut approximately 7 feet to facilitate the excavations for underground utilities. The undercut criteria where formational materials exposed near finish grade of the building pads was determined on a case-by-case basis by the owner, depending upon the apparent rippability of the materials exposed. Future excavations in areas where undercuts' were not performed may encounter difficult digging and require breaking and/or localized blasting. Also, oversize material may be generated by the excavations and require :special handling. Refer to the "As-Graded" Geologic Map (Figures 1. through 4) for the approximate delineation of formational areas. Fill Materials and Placement Procedures The on-site fill materials generally consisted of silty to clayey sands and sandy clays with mixtures of gravel and boulders generated from the various formational units exposed on site. In general, the upper 10 feet of building pads and roadways were limited to oversize material less than 12 inches in maximum dimension and 6 inches in the upper 3 feet. Rock material greater than 12 inches was placed deeper than 10 feet below proposed finish grade and at least 3 feet below the deepest utility. Fill materials classified as "soil-rock" miktures were placed in. some portions of the site by spreading and compacting the materials with a Caterpillar bulldozer in lifts 2 to. 3 feet thick or less. During placement of each lift, the fill was uniformly wheel-rolled with loaded rock trucks. These materials were heavily watered during spreading prior to compacting. Soil fills were placed in lifts no thicker - than would allow for adequate bonding and compaction. The soil was moisture conditioned, as p necessary, and mixed during placement. p. . Project No. 06442-32-04A -3 - August 30, 2006 p :.• Field' In-Place Density and LaboratOry Testing . S • Durm m g grading, copaction procedures were observed and rn-place density tests wer . e performed to eval'uate the relative compaction of the fill matenal The iii-place density tests were performed in general conformance with ASTM Test Method D 2922-01 (nuclear) Results of the field density tests and moisture content tests performed durmg grading are summarized on 'Fable I and the approxii'dmate locations are presented on the "As-Graded" Geologic Map In'general, the rn-place density test results indicate that the fill at the loations tested has a relative compaction of .-it:. at least 90 percent and an appropnate moisture content. Laboratory tests were performed on samples of material used for fill to evaluate moisture-density relationships, optimum moisture content and maximum dry deisity (ASTM D 1557-02), expansion charactenstics (ASi'M D 4829-03), sulfate potential (CA Test No 417) and shear strength (AS 'D 3080-03):L oratory testing Ior Phise I(Lots I through 9) was perforthèd concüitently with ihe grading for Faraday Avenue and El Fuerte Street; as such, the sample numbers are not in consecutive order. The results of the laboratory tests that are applicable to the subject grading are summarized on Tables II through V. ... . :..' '•', ,,: ..:•• . . .' , ' F'. Cut and fill slopes were graded at design inclinations of 2 1 (horizontal-.Vertical), or flatter, with Maxi mum heights of approximately 70 feet Slopes that exposed potentially adverse conditions (e g, weak silistones and claystones erosive soils, extensive seepage, etc) were ivi6Vided with a stability fill,The area where a stability fill was constructed is shown on the "As-Graded" Geologic Map .j. hi- gènefal, fill slopes were 'either over-filled and cut baók or 'fraëk-walledwith a bülldózer. during grading. Fill slopes cOmprisèd of clayier soil may be prone to surficial loosening due to** cyclical wetting and drying and may require increased maintenance. All slopes should be planted, drained, and maintained, to reduce erosion. Slope irrigation should be kept to a minimum to just support the vegetative cover Surface drainage should not b6l allowed to flow over the top of the slope Stabilization Fill Slopes A drained stabilization fill as constructed behind Lot 2 to reduce the potential of surficial slope instability due to theprësenáeof wek' cliystoneand si.Itst9nethatetiáls and extensive seepage. In :".. general, a 1:1 (horizontal:vertiéál)' backcut was iiiitiated beyond the top of slope and was extended below pad grade A heel dram and panel drain system was installed to collect the seepage encountered along the temp: backcüt. The excavation was then was backfilled with compacted granular granular fill material. Figure 5, Geologic Cross Section A-A', shows the approximate limits of the stability fill. Project No. 06442-32.04A -4- . August 30, 2006 Subdralns (GeheráI) P Two types of subdrains were constructed in accordance with our' recommendations The systems P consisted of i stability fill backdrain and canyon subdrains The subdrain locations were surveyed by P the project civil engineer and the locations are presented on the "As-Graded" Geologic Map Additional dicussión regáxding the construction of the drainage* iystems is provided below.. P The final segment of subdrains consisted of non-perforated drainage pipe provided with a concrete cut-off wall constructed at the perforated/non-perforated mterface It is recommended that all subdrain outlets that empty mto open space or brow ditches be provided with a headwall structure to protect the end of the pipe from damage or burial Stability Fill Baókdràlns The stability fill constructed on the north facing slope behind Lot 2 was provided with a drain system consisting of 4-foot-wide Mirafi drainage panels positioned approximately 20 to 30 feet on center and vertically oriented against the temporary backcut and connected to a heel drain at the bottom. The p heel drain consisted of an 8-inch-diameter perforated PVC pipe surrounded by 3%-inch, open-graded gravel wrapped in filter fabric. The heel drain was- extended to the west and east along the stability fill backcut and ultimately connected to a storm drain box structure located outside of the toe of slope - at El FuerteStreet approximate Station 17+75 and into the brow ditch situated on the west side of Lot 2. In addition, heel drain cleanouts were installed along the stability fill backcut in the event that future maintenance is necessary. The cleanouts were capped at the finish ground surface and their locations have been shown on the "As-Graded" Ueologic Map. -. Canyon Subdralns S p Typical canyon subdrains consisting of 8-inch'perforated PVC pipe encapsulated in gravel and filter p fabric were placed at the base of the remedial excavations where a depression occurred in the bedrock topography. Some of the original subdrain alignments were later diverted due to conflicts with underground utilities in Faraday Avenue whichwère not known during the initial placement of the subdrain system. - Finish Grade Soil Conditions Observations and laboratory test results indicate that prevailing soils randomly sampled (for Lots 3, 4, 5, 7 and 8) at finish grade have an Expansion Index (El) ranging from 0 t 2 and are classified as having a "very low" expansion potential (El of 20 or less) as defined by Uniform Building Code - (UBC) Table 18-I-B. The expansion condition for the lots in an interim condition will be provided upon completion of grading. Table III presents the results of the expansion classification for the prevailing soils at finish grade. I, Project No. 06442-32-04A - 5- August 30, 2006 Oversize fragments and roc materials were generated fromexcavations during the ding operation. To the extent possible, the oversize material was placed within the "hold down" ardds as previously discussed..The potential for encountering oversize materials (12 inches or greater) should be considered if deep excavations (10 feet or more are proposed (i e, underground utilities, etc) Although particular attention was given to restricting the oversize material to the placement zones described previously, I some randomly occurring fragments larger than 12 inches in nominal diameter may be present in the upper portions of fill areas The performance of the fill, however, should not be adversely affected and the grading perfornied is considered to be in substantial conformnce with our recommendations Corrosion 'S Laboratâry tests performed áñ' razidom° soil samples to measure the percentage of water-* soluble sulfate Of the compacted fill at finish grade for Lots 3 through 5, and 7 and 8 indicate that the On-site materials possess a "hegligible" to "moderate" potential for sulfate exposure to concrete structures, as defined by UBC Table 19-A-4. Table V presents the results of the water-soluble sulfate for the various lots sampled (Lots 3, 4, 5, 7, and 8). I Geocon Incorporated dOes not practice in the field of corrOsion engineering; Therefore, it is I recommended that further evaluatiàn by a corrosion engineer be performed if improvements are planned that are susceptible to corrosion. I SOIL AND GEOLOGIC CONDITIONS S In general, the soil and geologic conditions encountered during grading were found to be similar to those described in the referenced project geotechnical report. The enclosed "As-Graded" Geologic Map (Figures 1 through 4) depicts the general geologic conditions observed. Information provided by the project paleontologist was utilized in identifying the geologic units. Figure 5 (Geologic Cross Section A-A) represents the general geometry of the stability flit. The figures have been annotated to show a general representation Of the as-graded geologic conditions observed during grading. Geologic contacts should be considered approximate. No geologic conditions were observed during grading that would preclude the continued development of the lots. S •: CONCLUSIONS AND RECOMMENDATIONS 1.0 General 1.1 Based on observations and test results, it is the opinion of Geocon Incorporated that the grading, which is the subject of this report, :has been performed in substantial conformance with the recommendations of the referenced prOject. soil reports. Soil and geologic conditions encountered during grading that differ from those anticipated by the project soil I • Project No. 06442-32-04A -6- August 30,2006 • 0 •0 . •. .'' ':". . S repórt'are not uncommoii. Where such conditions requiEed a gnificant :. iflcatiôn'to the recommendations of the project soil report, they have been described herein. - 1:2 No soil or geologic conditions were observed during grading that would preclude the continued development of the property as planned Based upon laboratory test results and field observations, it is our opinion that the fill.soils within the subject lots and associated streets have generally been compicted to at least 90 percent relative compaction at the j ;: . ..:'. ";• . :'. .• . .:. S ... 1.: :.. . ..: 1 3 Fine grading and construction of utilities/foundations may encounter non-rippable formational material and/or generate some concretionary fragments and/or rock material 12 niches or greater in situ Deeper excavations within the fill (10 feet or greater) for itö'vtheÜts' Such ás 1Iiie: loading' docks, etc,' rnaals àunter:t oversize 2 inches or greater): The potential for these condititins should be taken Into consideration when determining the type of equipment to 'utilize for future excavation operations. The oversize material may require special handling techniques and exportation. It is not uncommon for '&oundwater. or. seepage conditions., to. develop where none,, previously existed, particularly after landscape irrigation is initiated The occurrence of induced groundwater seepage from landscaping can be greatly reduced by implementing and monitoring a landscape program that limits Irrigation to that sufficient to support the vegetative cover without overwatermg Shallow subdrains may be required in the future if seeps 6ccU'aftCr rainy periods or aftör landScàiinjis installed.:. ifèrezces to the thickness nd ext nt of rock hold-down areas within roadways or capping of 'bull ing pads are approximate 'and were based upon the finish grade elevations of the approved referenced grading plans. I.. 2.0 2.1, Drainage Adequate drainage proviSioñs"are' imperative. Under no circumstances should w'ater be allowed to pond adjacent to footings The building pads should be properly finish graded after the buildings and other improvements are in place so thaf draniage water is directed 'away 'from 'fothdátibns pavements ; °coñcièté' slabs, and ilope 'tops to' con&olléddraiñâge devices. . . Project No. 06442-32-04A . -7- . . August 30, 2006 1.4 3 1 An update geotechnical report presenting fine-grading recommendations and geotechnical design criteria should be prepared by Geocon Incorporated once the final development i. plans have been prepared for the subject lots LIMITATIONS The conclusions and recommendations contained herein apply only to our work with respet to grading and represent cond on June 13, itions at the date of our final observation of grading operations 2006 An' subsequent grading should be done in conjunction with our observation and testing services . As used herein' the ter "observation" inipliesonly thitweobseived the progress of the work with which we agreed to be involved. Our services did not include the evaluation or identification of the potential presence of hazardous materials. Our conclusions and opinions as to whether the work essentially complies with the job specifications are based on our observations, experience and test results. Due to the inaccuracies inherent in most field and. laboratory soil tests, and the necessary : assumption that the relatively small soil sample testedis representative of a significantly larger. volume of soil, future tests of the same soil location or condition should not be expected to duplicate specific individual* t sults of this rèpri Subüaôe âditions and the acür Of tests used to . measure suchcóditio an vary greatly at any time. We make no warranty, exptes§ or implied, except that our services were performed in accordance with engineering principles generally accepted at this time and location We. will accept S respOnsibility for any subsequent changes made to the site by othérs,by the uncontrolled action of water, or by the failure of others to properly repair damages caused by the uncontrolled action of water. It is the responsibility of Techbilt Construction Company to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project, are Incorporated into the plans, and that the necessary steps are taken to see: that the. contractor:.': and..s,contactórs carry..ou t. Such recommendations . in thó flld. Recommendations that pertain to the future maintenance and care for the property should be brought to the attention of future owhers of the property or portions thereof. The findings and recommendations of this report may be invalidated wholly or partially by changes outside our control. Therefore, this répórt is subject to review and should not be relied upon after a p&riod of three years. Project No. 06442-32-04A . . -8- . August 30, 2006 Very truly yours, GEOCON INCORPORATED ¼ RCE 6319 Exp QMD TKR:SR:anh . (10/del) Addressee . .. S' . . . . . . . . . . . S .. .(. j• .:•. :. August 30,206 . Project No. 06442-32-04A -9- - .