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HomeMy WebLinkAboutCT 04-26; ROBERTSON RANCH EAST VILLAGE PA 16, 17, & 18; REVISED PAVEMENT DESIGN REPORT GLEN AVENUE; 2008-10-10cc Q4-2 Geotechnical *Geologic * Coastal • Environmental 5741 Palmer Way Carlsbad, California 92010 • (760) 438-3155 FAX (760) 931-0915 October 10, 20O8 (Revised October 31, 208) Brookfield San Diego Builders, Inc. 12865 Pointe Del Mar-Suite-200 % I R Del Mar, California 92014 Alt/& VJ I ,,rOC) -41 Attention: Mr. Greg McDonnell Subject: Revised Pavement Design Report, Glen Avenue, Station 26"' to the Cut Du Sac, Robertson Ranch East Village, City of Carlsbad, San Diego County, California Dear Mr. McDonnell: In accordance with your request, GeoSoils, Inc. (GSI) has prepared preliminary design and construction recommendations for asphalt concrete (AC) pavement at the subject site The scope of services provided in preparationof this report include a review of the referenced reports and documents (see the Appendix), an evaluation of the pavement section for the subject area, and preparation of this report. PAVEMENT DESIGN Pavement section evaluation was based on traffic index (TI) values provided by (O'Day Consultants, personal communications). Pavement sections were evaluated in accordance with the California Department of Transportation (Caltrans) Highway Design Manual of Instructions and the City of Carlsbad Standard Drawings (see the Appendix). Pavement sections presented are based on the aforementioned criteria and resistance value (R-value) data (see table), evaluated from soils exposed at, or near, final subgrade elevations within the subject areas. A-value testing was performed in general accordance with the latest revisions to the Department of Transportation, State of California, Material & Research Test Method No. 301. ASPHALT CONCRETE PAVEMENT Structural Section Traffic Indices (TI) were provided bythe project civil engineer (O'Day Consultants, personal communication) as 5.0 for the subject traffic areas.. R-values (see Plates 1 through 3) ranging from 6 to 20 were obtained for representative subgrade soils onsite and used in pavement design. The recommended pavement sections are presented in the following table: APPROXIMATE '- TRAFFIC SUBGRADE THlCKNESS BASE THICKNESS 3 I'jRAFFIC IREA ' INLEX' R;VfLUE t Inc inh)1 Glen Avenue, Stations 26 5.0 9 4.0 8.0(2)* to 28 9 Glen Avenue, Stations 28 5.0 6 4.0 to3l'99 Glen Avenue, Stations 31 5.0 20 ,..' 4.0 J34 ( toCulDuSac Per O'Day Consultants, (personal communication) Exceeds City minimum Denotes Class 2 Aggregate Base R >78, SE >25) (4) GSl does not recommend using less than 6 inches of AB, although 5 inches was calculated * Exceeds Caltrans requirements 4' 4 , All pavement installation, including preparation and compaction of subgrade, compaction of base material, and placement and rolling of asphaltic concrete, shall be done in accordance with the City guidelines, and under the observation and testing of the project geotechnical engineer and/or the City. It should be noted that subgrade lime treatment was previously waived by the City for the construction of pavement in the Calavera Hills/Robertson Ranch area (GSl; 2007a, 2007b, 2007c, 2004a, 2004b, and 2004c). It is therefore anticipated that lime stabilization will not be performed for the current 'road construction. It should also be noted that the pavement sections presented for low R-value subgrades exceed the minimum design thickness, using Caltrans design methodology, by an additional 1 inch of base, for these relatively onerous subgrade conditions. The recommended pavement sections are meant as minimums. if thinner or highly variable pavement sections are constructed, increased maintenance and repair may be needed. The recommended pavement' sections provided above are intended as a minimum guideline. If thinner or highly variable pavement sections are constructed, increased maintenance and repair could be expected. If the ADT (average daily traffic) or ADIT (average daily truck traffic) increases beyond that intended, as reflected by the TI used for design, increased maintenance and repair could be required for the pavement Brookfield San Diego Bui!ders, Inc. , V W.O. 5353-El-SC Glen Ave., Robertson Ranch East Village Revised October 28, 2008 File: e:\wp9\5300\5353e1.rpdr Page 2 GeoSoits, Inc. section. Consideration should be giveri.to the increased potential for distress from overuse of paved street areas by heavy equipment and/or construction related heavy traffic (e.g., concrete trucks, loaded supply trucks, etc.), particularly when the final section is not in place (i.e., topcoat) Best management construction practices should be followed at all times, especially during inclement *èather PAVEMENT GRADING RECOMMENDATIONS General All section changes shall be. properlytransitioried. If adverse conditions are encountered during the preparation of subgrade materials, special construction methods may need to be employed. A GSI representative shall be present for the preparation of subgrade, base rock, and asphalt concrete. Subgrade Within street and parking areas, all surticial deposits of loose soil material shall be removed and recompacted as recommended After the loose soils are removed the bottom is to be scarified to a depth of at least 12 inches moisture conditioned as necessary and compacted to 95 percent of the maximum laboratory density, as determined by ASTM test designation D 1557. Deleterious material, excessively wet or dry pockets, concentrated zones of oversized rock fragments and any other unsuitable materials encountered during grading shall be removed The compacted fill material shall then be brought to the elevation of the proposed subgrade for the pavement. The subgrade shall be proofroIled in order to ensure a uniform firm and unyielding surface. All grading and fill placement shall be observed by the project soil engineer and/or his representative. Base Rock Compaction tests are required for the recommended base section. Minimum relative compaction required will be 95 percent of the laboratory maximum density as determined by ASTM test designation D 1557. Base aggregate shall be in accordance with Section 26 of Caltrans Standard specifications (California Department of Transportation, 2006), for Caltrans Class 2 aggregate base. Brookfield San Diego Builders, Inc. W.O. 5353-El-SC.' Glen Ave. Robertson Ranch. East Village Revised. October 28, 2008 Fi1e:e:\wp9\5300\5353e1.ipdr Page. 3 GeOSQIIs, Inc. Paving Prime coat may be omitted if all of the following conditions: are met: The asphalt pavement layer is placed within two weeks of completion of base and/or subbase course. 2. Traffic is not routed over completed base before paving. 3,. Construction is completed during the dry season of May through October. 4. The base is kept free of debris prior to placement of asphaltic- concrete. If construction is performed during the wet season of November through April, prime coat may be omitted if no rain occurs between completion of base course and paving and the time between completion of base and paving is reduced to.three days, provided the base is free of loose soil or debris. Where prime coat has been omitted and rain occurs, traffic is routed over base course, or paving is delayed, measures shall be taken to restore base course and subgrade to conditions that will meet specifications as directed by the soil engineer. Drainage Positivei drainage shall be provided for all surface Water to drain toward the curb and gutter, or to an approved drainage channel Positive site drainage shall be maintained at all times. Water shall not be allowed to pond or seep into the ground. Over-watering of landscape areas should be avoided. OTHER DESIGN PROFESSIONALS/CONSULTANTS The design civil engineer shall review the re commendations provided herein, incorporate those recommendations into their plans and by explicit reference make this report part of their project plans. 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. Brookfield San Diego Builders, Inc. W.O. 5353-El -SC Glen Ave., Robertson Ranch East Village Revised October 28, 2008 File :e:\wp9\5300\5353e1.rpdr Page 4 GeoSélls, Inc. 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 express or implied. Standards of practice are subject to change with time. GSl assumes no responsibility or liability for work or testing performed by others, or their inaction, or work performed when GSl is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent bythe 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. The opportunity to be of service is greatly appreciated. lf.you have any questions, please do not hesitate to call our office. Respectfully sub GeoSoils, Inc. 0. Robert G. Crisma Engineering Geol RGC/ATG/JPF/jk Attachments Distribution G. No. 1934 Cer,tfled I Engioeerihg Geologist Op CGi 934 Geotechnical Engineer, GE 2320 Plates i through .3 - R-value Test Results Appendix - References (4) Addressee Bro'okfield San Diego Builders, Inc. W.O. 5353-El-Sc Glen Ave., Robertson Ranch East Village . Revised October 28, 2008 Fi1e:e:\wp9\5300\5353e1.rpdr . Page 5 GeoSoils, Inc.