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HomeMy WebLinkAbout3151; Palomar Airport Road; Palomar Airport Road; 1987-05-22( I I 'i Testing Engineers—San Diego A Division ol United Stales Testir/g Company. Inc. 3467 Kurtz St., P.O. Box 80985, San Diego, Ca. 92138 (619) 225-9641 2956 Industry Street, Oceanside, California 92054 (619) 757-0248 City of Carlsbad •Community Development 2075 Las Palmas Drive Carlsbad, California 92008 Attention; Mr. Al Virgilio May 22, 1987 Job No. 7092-1 RECElViiD "f/iAY 2? 1937 MUNICIPAL PROJECTS DIVISION Subject; Supplementary Geotechnical Consulting Services Palomar Airport Road East of Paseo Del Norte Carlsbad, California Gentlemen: This report presents results of our additional soil investigation and pavement section design of the subject site. The purpose of the soil investigation was to retain bulk soil samples to be used in the laboratory for "R"^value tests. These actual "R"-value test results were then used to estimate the various pavement sections presented herewith. Subsurface conditions were explored by drilling ten 8-inch diameter test borings with a Mobile B-61 drill rig, to 4 to 20 feet depths. A staff geologist from our office was present during the drilling of the test borings. The sample locations and soil types with the respective "R"-value results are presented in Table I. 316 Palomar Airport Road East of Paseo Del Norte Carlsbad, California Page No. 2 May 22,. 1987 Job No. 7092-1 TABLE I Bore Hole No, Bore Hole Location Sample Depth Feet Soil Type R-Value 1 30+00 8 Sandy clay 12 2 32+50 13 Sandy clay 13 3 36+00 12-15 Sandy clay 9 4 36+00 18-20 Sandy clay 8 5 40+00 7 Gravelly Refusal @ 7 ft. 6 42+00 7 Sandy clay 6 7 50+00 2-4 Silty sand 47 8 53+00 4-6 Clayey sand 21 9 72+50 5 Silty sand 57 10 85+00 . 6-8 Silty clay 27 CJ • • O Palomar Airport Road Page No. 3 East of Paseo Del Norte May 22, 1987 Carlsbad, California Job No. 7092-1 ASPHALTIC CONCRETE DESIGN Based on the R-value results and a T.I. value of 9 for primary arterial, as required by the City of Carlsbad, alternate structural sections are computed. For purposes of section design, "R"-value results have been separated to represent three zones of the alignment. The results are summarized and presented on Table II. The design assumes a minimum asphaltic concrete thickness of 6 inches and processed Class II aggregate base course. If the three layer conventional system is preferred, we recommend disintegrated granite (D.G.) with minimum "R"-value of 50 to be used as select import for a subbase course. i. ) Palomar Airport Road Page No. 4 East of Paseo Del Norte May 22,. 1987 Carlsbad, California Job No. 7092-1 TABLE NO. II RECOMMENDED SECTION DESIGN ALTERNATIVES Materials are referenced to Cal Trans Standard Specifications for aggregate subbase, aggregate base, and asphaltic concrete. Zone 1: Station 27+00 to Station 32+50 Basement Soil R-Value 12 Traffic Index (Prime Arterial) 9 Minimum a.c. Thickness, ft. (inch) 0.5' (6") Minimum cover required (GE) ft. (inch) 2.55 Alternative 1: Conventional 3 Layer System; Actual Gravel Equivalent (GE) Course (Gf) Feet Asphaltic Concrete 1.80 0.90 Class II Agg. Base 1.10 0.91 Agg. Subbase (R=50) 1.00 0.75 2.56 Thickness Feet Inch 0.50 6 0.83 10 0.75 9 2.08 25 Alternative 0.50 6\ 1.50 18 / 2.00 24/ Asphaltic Concrete 1.80 Class II Agg. Base 1.10 ( } Palomar Airport Road Page No. 5 East of Paseo Del Norte May 22,.1987 Carlsbad,.California Job No. 7092-1 Zone 2: Station 32+50 to Station 50+00 Basement Soil R-Value 6 Traffic Index (Prime Arterial) 9 Minimum a.c. Thickness, ft. (inch) 0.5' (6") Minimum cover required (GE) ft. (inch) 2.70 Alternative 1: Conventional 3 Layer System; Actual Gravel Thickness Equivalent (GE) Feet Inch Course (Gf) : Feet 0.50 6 Asphaltic Concrete 1.80 0.90 0.83 10 Class II Agg. Base 1.10 0.91 0.92 11 Agg. Subbase (R=50) 1.00 0.92 2.25 27 2.73 Alternative 2: Conventional 2 layer System; 0.50 6. Asphaltic Concrete 1.80 0.90 1.67 20 Class II Agg. Base 1.10 1.83 2.17 C2i^'' 2.73 Note: Based on the "R"-value results and uniform soil type at Station 36+00, either of the above asphaltic pavement sections can be utilized at 17 feet road level. The "R"-value shown on Table I should be verified after grading. I , ) Palomar Airport Road East of Paseo Del Norte Carlsbad, California Page No..6 May 22, 1987 ' Job No. 7092-1 Zone 3; Station"50+00 to Station 85+00 Basement Soil R-Value Traffic Index (Prime Arterial) Minimum a.c. Thickness, ft. (inch) Minimum cover required (GE) ft. (inch) 21 9 0.5' (6") 2.28 Alternative 1; Conventional 3 Layer System: Actual Thickness Feet Inch Course (Gf) Gravel Equivalent Feet (GE) 0.50 6 Asphaltic Concrete 1.80 0.90 0.50 6 Class II Agg. Base 1.10 0.55 0.83 10 1.83 22 Agg. Subbase (R=50) 1.00 0.83 2.28 Alternative lA; Actual Thickness Feet Inch Course (Gf) Gravel Equivalent Feet (GE) 0.50 6 Asphaltic Concrete 1.80 0.90 0.83 10 Class II Agg. Base 1.10 0.91 0.50 6 Agg. Subbase (R=50) 1.00 0.50 1.83 22 2.31 Alternative 2: Conventional 2 layer System: 0.50 6 Asphaltic Concrete 1.80 0.90 1.25 15 1.75 21 Class II Agg. Base 1.10 1.38 2.28 Palomar Airport Road Page No. 7 East of Paseo Del Norte May 22, 1987 Carlsbad, California Job No. 7092-1 The samples taken are assumed to be representatives of the material which will be immediately under the planned structural section. The design is based on the lowest "R"-value for that zone since it represents the lowest quality material encountered. The asphaltic pavement sections recommended reflect our best estimate of the project requirements based on an evaluation of the subsurface soil conditions encountered at the exploration locations and the assumption that the soil conditions do not deviate appreciably from those encountered. Any unusual conditions, not covered in this report, encountered during site development, should be brought to the attention of the soil engineer. The "R"-value results should also be verified before construction, so that modifications can be made if necessary. This office should be advised of any changes in the project scope or proposed site grading so that it may be determined if the recommendations contained herein are appropriate. Palomar Airport Road East of Paseo Del Norte Carlsbad, California Page No. 8 May 22, 1987 Job No. 7092-1 We appreciate the opportunity to be of service to you on this project and look forward to a continued association on this and future projects. If you have any questions, please do not hesitate to contact our office. Almaz FWS eha Project Engineer Respectfully submitted, TESTING ENGINEERS-SAN DIEGO 1Thomas H. Chapman, RCE 34228 ^ Vice President THC/AF/eh Addressee (2) cc: Jay F. Olsen Testing Engineers—San Diego A Division ol United States Testing Company, Inc. •. 3467 Kurtz St., P.O. Box 80985, San Diego, Ca. 92138(619) 225-9641 2956 Industry Street, Oceanside, California 92054 (619) 757-0248 April 22, 1987 Job No. 7092 City of Carlsbad Community Development 2075 Las Palmas Drive Carlsbad, California 92008 Attention: Mr. Al Virgilio Subject: Geotechnical Consulting Clarification of Elements Regarding Palomar Airport Road Widening Report Carlsbad, California Referenced Report: "Geotechnical Consulting Palomar Airport Road Widening Carlsbad, California," by Testing Engineers-San Diego, dated March 3, 1987 Referenced Letter: "Geotechnical Consulting Palomar Airport Road Widening," by Pountney and Associates, Inc., dated March 30, 1987 Palomar Airport Road Widening Page No. 2 Carlsbad, California April 22, 19817 Dear Mr. Virgilio: This is in response to the referenced letter written by Pountney & Associates, Incorporated regarding our report on the project. During the process of study, limited contact was made between Testing Engineers and the other company in discussing the items to be considered, and its general format. As a result, Pountney and Associates wrote the letter asking fbr clarification and the following is discussed for each of the items: SECTION 1.1 1. "The near surface, saturated, alluvial soil, whenever encountered, should be removed to a minimum depth of three feet" is a general construction recommendation. SECTION 1.2 2. "Soil adjacent to. the roadway should be excavated and recompacted. The excavation should extend to at least ten feet (10') from the outside edges of the roadway". A roadway is in this definition the pavement section, from curb to curb. This excavation and recompaction is intended to give lateral support to the soil under the pavement, to provide protection from erosion and reduce water seepage, as explained in the report. Palomar Airport Road Widening Page No.. 3 Carlsbad, California April 22, 1987 SECTION 1.3 3. The Benching requirement refers to downslope fills. SECTION 1.4 4. The soil removal is mentioned in the two sections. Section 1.1 is refering to the excavation of local pockets of soft and saturated soils wherever encountered. Section 1.4 is referring to loose and/or compressible existing top soil which is to be removed uniformely. Unless the soil is saturated, removal should be limited to two foot thickness. SECTION 1.8 5. Permanent cut and fill slopes should be inclined at no steeper than 2 to 1 (horizontal to vertical). SECTION 2.2 6. In our rough draft of the report, two alternatives including a retaining wall and a crib wall were mentioned. Prior to issuance of our final report, we deleted the crib wall alternative without deleting the "above alternatives". SECTION 3.1 7. We understand there was no specific requirement that the pavement be designed for a Traffic Index (TI) value of 9. La Costa. Avenue, another important project was designed for a T.I. value of 8. So we assumed the same for Palomar Airport Road. Palomar Airport Road Widening Page No. 4 Carlsbad, California April 22, 1987 If TI of 9 is to be used, then an asphalt concrete thickness and crushed aggregate base of 6 inches and 15 inches, repectively, could be used. The City of Carlsbad requires a minimum section of 6 and 18 inches, respectively. A detour pavement section of 4 inches asphalt concrete and 8 inches of aggregate base may be used. SECTION 3.2 8. This section was included because we understand that grading would generate excess material and we suggested that the clay be exported and the on-site granular soil be used in the roadway. We had a discussion about all the above items with Mr. Jay F. Olsen in our meeting on April 10, 1987 and have come to a better understanding. In summary, we feel that the overall recommendations in the report cover most of the necessary design parameters as well as construction techniques. All of the above questions could have been clarified easily with better communication. We hope our contact will improve in the future. Palomar Airport Road Widening Page No. 5 Carlsbad, California April 22, 1987 The opportunity to be of service is appreciated, and if you have any additional questions regarding this project, please do not hesitate to contact us at your convenience. Respectfully submitted, TESTING ENGINEERS-SAN DIEGO Almaz FesTseha Project Engineer AF/eh Addressee (2)