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Home My WebLink AboutCT 04-04; LA COSTA RIDGE NEIGHEBORHOOD 2.5; PAVEMENT RECOMMENDATIONS SITIO TORTUGA; 2006-04-05I GEOCON I N C 0 R P 0 R A- T E D 'I3&-'/ 01 Q4-04 GEQTECHNICAL CONSULTANTS Project No. 07290-52-07B April 5, 2006 KB Home Coastal Incorporated 12235 El Camino Real, Suite 100 San Diego, California 92130 Attention: Mr. Gary Mingo Subject: VILLAGES OF LA COSTA - THE RIDGE NEIGHBORHOOD 2.5 SITIO TORTUGA - STATIONS 17+15 TO 22+13 CARLSBAD, CALIFORNIA PAVEMENT RECOMMENDATIONS Gentlemen: In accordance with your request, we have performed supplemental geotechnical services for the subject roadway within the Villages of La Costa - The Ridge development. The scope of our services included obtaining representative subgrade soil samples within the street and performing Resistance Value (R-Value) tests. The purpose of our work was to provide pavement design recommendations. To aid in preparing this letter, we have reviewed the improvement plans entitled Private Street and Improvement Plans for: La Costa Ridge .- Neighborhood 2.5, prepared by Hunsaker and Associates, City of Carlsbad approval dated August 22, 2005; and our report entitled Update Geotechnical Report, Villages of La Costa - The Ridge Neighborhood 2.5, Carlsbad, California, prepared by Geocon Incorporated, dated February 1, 2006 (Project No. 07290-52-07). Subgrade soils in the area are predominately clayey fine sands and sandy to clayey gravels and exhibit relatively low to moderate R-Value characteristics. Based on field observations and previous laboratory tests, subgrade materials possess an expansion potential of "very low" to "low"• (Expansion Index of 50 or less) as defined by Uniform Building Code (UBC) Table 18-I-B. R-Value laboratory tests were performed in accordance with ASTM D 2844-01 (California Test Method No. 301) and the laboratory test results are presented on Table I. Based on conversations with Hunsaker and Associates, the project civil engineer, we understand that a Traffic Index (TI) of 5.0 has been assigned to the subject roadway. Based on the above information and laboratory testing, we recommend the pavement sections indicated on Table II. Pavement section calculations were performed in accordance with California Department of Transportation Highway Design Manual; Section 608.4 and the City of Carlsbad Minimum Structural Standard GS-17. Pavement section calculations are presented on Figure 1. These recommended ections should be considered preliminary with final sections to be determined and approved by the City of Carlsbad. Prior to placing base material for roadways as well as curb and gutter, we recommend the upper 12 inches of subgrade be scarified, moisture onditioned as necessary, and compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content in accordance with ASTM D 1557-02. In addition, the Class 2 aggregate base shall be 6960 Flanders Drive • San Diego, California 92121-2974 0 Telephone (858) 558-6900 U Fax (858) 558.6159 compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content. Asphalt concrete shall be compacted to a density of at least 95 percent of the laboratory Hveem density in accordance with ASTM D 2726-04. The upper 12 inches of subgrade beneath areas to receive concrete sidewalks shall be compacted to a dry density of 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content. Fill soil and aggregate base -lift thicknesses should not exceed 6 inches. Class 2 aggregate base and asphalt concrete shall 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, - W& recommend that a minimum drainage gradient of 1 percent be maintained for pavement surfaces. Drainage from landscaped areas should be directed to controlled drainage structures. Should 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 - Michael C. Ertwine . Shane Rodacker Senior Staff Geologist . RCE 63291 CO (1) Hunsaker and Associates cc .6130166 x rzr? Attention: Mr. David Blalock I] Prdjèct No. 07290-52-07B - 2 - April 5, 2006 TABLE I SUMMARY OF R-VALUE TEST RESULTS ASTM D 2844-01 (CALIFORNIA TEST METHOD NO. 301) Sample Number Location R-Value R-1 Sitio Tortuga - Stations 17+15 to 19+65 22 R-2 Sitio Tortuga - Stations 19+65 to 22+13 24 TABLE If PAVEMENT SECTION RECOMMENDATIONS Traffic Asphalt Class 2 Location Index Concrete Aggregate Base (TI) (inches) (inches) Sitio Tortuga - Stations 17+15 to 19+65 5.0 4.0 5.0 Sitio Tortuga -Stations 19+65 to 22+13 5.0 4.0 4.0 Project No. 07290-52-07B FIGURE 1 PAVEMENT SECTION CALCULATIONS / VILLAGES OF LACOSTA -.THE RIDGE Sitio Tortuga - Stations 17+15 to 19+65 Use subgrade R-Value = 22.0 Traffic Index (TI) = 5.0 Methodology = CALTRANS Highway Design Manual Section 608.4 Safety Factor = 0.2 -- Applied to Asphalt Concrete (AC) GE for AC = (0.0032)( 5.0)(100-78.0)+0.2 = .55 feet from Table 608.4B Highway Design Manual GE = .55 feet for AC yields actual thickness = 2.65, inches Use 4.0 inches of AC - City Minimum GE for 4.0 inches of AC = .83 feet GE for base = (0.0032)( 5.0)(100-22.0) - .83 = .41 feet from Table 608 .4B Highway Design Manual with GF for Class 2 base = 1.1 Base thickness = 4.52 inches Use base thickness = 5.0 inches Design Street Structural Section *** Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggrgate Base Thickness = 5.0 inches. Sitio Tortuga - Stations 19+65 to 22+13 Use subgrade R-Value = 24.0 Traffic Index (TI) = 5.0 Methodology = CALTRANS Highway Design Manual Section 608.4 Safety Factor = 0.2 -- Applied to Asphalt Concrete (AC) - GE for AC = (0.0032)( 5.0)(100-78.0)+0.2 = .55 feet from Table 608.413 Highway Design Manual GE = .55 feet for AC yields actual thickness = 2.65 inches Use 4.0 inches of AC - City Minimum GE for 4.0 inches of AC = .83 feet GE for base = (0.0032)( 5.0)(100-24.0) - .83 = .38 feet from Table 608 .4B Highway Design Manual with GF for Class 2 base = 1.1 Base thickness = 4.17 inches Use base thickness = 4.0 inches *** Design Street Structural Section Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness = 4.0 inches. Project No. 0729052-07B April 5, 2006