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Home My WebLink AboutSDP 99-07; RANCHO LA COSTA VILLAGE; PAVEMENT SECTIONS - RANCHO SANTA FE ROAD; 2002-01-08GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS (low) Project No. 05467-52-08 January 8, 2002 RECEWED Simac Construction JAN 2 2002 15938 Bernardo Center Drive. San Diego, California, 92127 ENGINEERING Attention: Mr. Richard Simis 1)EPARTME!"!T Subject: RANCHO LA COSTA VILLAGE CARLSBAD, CALIFORNIA PAVEMENT SECTIONS - RANCHO SANTA FE ROAD NORTHBOUND WIDENING STATION 159+00 TO STATION 165+95 Gentlemen: In accordance with your request, we have performed supplemental geotechnical services for Rancho Santa Fe I Road fronting the Rancho La Costa Village development. The scope of our services included obtaining representative subgrade soil samples within the proposed street widening, performing Resistance Value (R-Value) laboratory tests, and to provide pavement design recommendations. To aid in preparing this letter, we have reviewed Improvement Plans for. Rancho La Costa Village, prepared by Stuart Engineering, and our geotechnical report entitled Interim Report of Testing and Observation Services During Site Grading, Rancho La Costa Village, Carlsbad, California, dated November 27, 2001 (Project No. 05467-52-07). Existing soil in the subgrade area are predominately clayey sand and silty clay and exhibit low R-Value characteristics. Based on field observations and laboratory tests, it is our opinion that subgrade materials have an Expansion Index (El) less than 90 and can be classified as "medium" in expansion potential as defined by the Uniform Building Code 1997 (UBC) Standard 18-I-B. It is our understanding that a Traffic Index (TI) of 8.5 has been assigned to Rancho Santa Fe Road. Based on the above information, the laboratory R-Value. test results, and using procedures from California Department of Transportation Highway Design Manual; Section 608.4, we recommend the pavement sections indicated in Table I. Results of the laboratory R-Value tests are shown in Table II, and pavement design calculations are shown in Figure 1. The recommended section should be considered preliminary with a final section to be determined and approved by the City of Carlsbad. It should be noted that Table I reflects the City of Carlsbad minimum structural section for "major arterial streets" as listed on: Structural Section of Streets and Alleys, dated April 20, 1993. It is recommended that unsuitable soils within the proposed road widening, be processed and compacted prior to placing base material for roadways, as well as curb and gutter. We recommend the upper 12 inches of subgrade be scarified, moisture conditioned and compacted to a minimum of 95 percent of the laboratory maximum dry density at or slightly above optimum moisture content as determined by ASTM D1557-91. In addition, the Class 2 aggregate base should be compacted to a minimum of 95 percent of the laboratory maximum dry density at or slightly above optimum 6960 Flanders Drive 0 San Diego, California 92121-2974 0 Telephone (858) 558-6900 0 Fax (858) 558-6159 moisture content as determined by ASTM D1557-91 and lift thickness should not exceed six inches. The upper 12 inches of subgrade beneath areas to receive concrete sidewalks should be compacted to a minimum 90 percent of the laboratory maximum dry density at or slightly above optimum moisture content as determined by ASTM D1557-91. Asphalt concrete should be compacted to 95 percent of the laboratory Hveem density as determined by ASTM D2726. Class 2 aggregate base and the asphalt concrete should conform to the City of Carlsbad specifications. The performance of asphalt concrete pavement is highly dependent on providing positive surface drainage away from the edge of the pavement. Ponding of water on or adjacent to the pavement will likely result in pavement distress and subgrade failure. To reduce the occurrence for such situations, we recommend that a minimum drainage gradient of 1 percent be maintained for pavement surfaces. Drainage form landscaped areas should be directed to controlled drainage structures. If you have any questions regarding, this correspondence, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON INCORPORATED hawn Weedon RCE 61803 c 3 Lu DFL:dlj ExP O6i3O/ )' (2) Addressee (3/del) Simac Construction (Jo Attention: Mr. Don Anthony (1) Stuart Engineering Attention: Mr. Stuart Peace Project No. 05467-52-08 - 2 - January 8, 2002 rancho santa fe road 159+00-162+00 Use subgrade R-Value = 12.0 Traffic Index (TI) = 8.5 Methodology = CALTRANS Highway Design Manual Section 608.4 Safety Factor = 0.2 -- Applied to Asphalt Concrete (AC) GE for AC = (0.0032)'( 8.5) (100-78.0)+0.2 = .80 feet from Table 608.4B Highway Design Maiival GE = .80 feet for AC yields actual thickness = 5.07 inches Use AC thickness = 5.0 inches GE for AC thickness used = .79 feet GE for base = (0.0032) ( 8.5) (100-12.0) - .79 = 1.61 feet from Table 608.4B Highway Design Manual with GF for Class 2 base = 1.1 Base thickness = 17.52 inches Use base thickness = 17.5 inches *** Design Street Structural Section Asphalt Concrete Thickness = 5.0 inches. Class 2 Aggregate Base Thickness = 17.5 inches. rancho santa fe road 162+00-165+95 Use subgrade R-Value = 12 .0 Traffic Index (TI) = 8.5 Methodology CALTRANS Highway Design Manual Section 608.4 'Safety Factor = 0.2 -- Applied to Asphalt Concrete (AC) GE for AC = (0-0632)( B.'5)(100-78.0)+0.2 = .80 feet from Table 608.4B Highway Design Manual GE = .80 feet for AC yields actual thickness = 5.07 inches Use AC thickness = 5.0 inches GE for AC thickness used = .79 feet GE for base = (0.0032) ( 8.5) (100-12.0) - .79 = 1.61 feet from Table 608.4B Highway Design Manual with GF for Class 2 base = 1.1 Base thickness = 17.52 inches Use base thickness = 17.5 inches Design Street Structural Section Asphalt Concrete Thickness =. 5.0 inches. Class 2 Aggregate Base Thickness = 17.5 inches. I PAVEMENT DESIGN CALCULATIONS I GE000N (low) INCORPORATED GEOTECHNICAL CONSULTANTS 6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974 PHONE 858 558-6900- FAX 858 558-6159 SW/AML DS7E0000 E/GE0TEO1/PtATE/GV1CMI'3.DWG/on RANCHO LA COSTA CARLSBAD, CALIFORNIA DATE 01-08.2002.] PROJECT NO. 05467 -52-08 1 FIG. TABLE I PAVEMENT SECTION RECOMMENDATIONS Location Asphalt Concrete Class 2 Aggregate Base - (inches) (inches) Rancho Santa Fe Road Station 5.0 18.0 159+00 to 165+95 TABLE II SUMMARY OF R-VALUE AND SAND EQUIVALENT TEST RESULTS * Sample No. Location R- Value R-3 Rancho Santa Fe Road Station 159+00 to 162+00 12 R-4 Rancho Santa Fe Road Station 162+00 to 165+95 12 *Rvalue by California Test Methods 301. Project No. 05467-52-08 January 8, 2002