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Home My WebLink AboutCT 04-03; LA COSTA RIDGE NEIGHBORHOODS 2.3 & 2.4; PAVEMENT RECOMMENDATIONS CORTE BOSQUE, CORTE PACIFICA; 2006-01-04/? Ot/O3 C1O.07t GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS (low) Project No. 07290-52-05 January 4, 2006 Shea Homes 9990 Mesa Rim Road San Diego, California 92121 Attention: Mr. Greg Ponce Subject: VILLAGES OF LA COSTA - THE RIDGE NEIGHBORHOODS 2.3 AND 2.4 (NORTH) CORTE BOSQUE STATIONS 10+10 TO 13+30 CORTE PACIFICA STATIONS 10+10 TO 12+50 CARLSBAD, CALIFORNIA PAVEMENT RECOMMENDATIONS Gentlemen: In accordance with your request, we have performed supplemental geotechnical services for the subject roadways within the Villages of La Costa - The Ridge development. The scope of our services included obtaining representative subgrade soil samples within the street areas 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 Improvement Plans and Utility Plans for: La Costa Ridge - Neighborhoods 2.3 and 2.4 (North), prepared by Hunsaker and Associates (Drawing No:, 420-5), City of Carlsbad approval dated August 23, 2005, and our report entitled Update Geotechnical Investigation, Villages of La Costa - The Ridge, Carlsbad, California, prepared by Geocon Incorporated, dated August 27, 2001 (Project No. 06015-52-05). Subgrade soils in the area are predominately clayey fine sands and sandy to clayey gravels and exhibit relatively low to high 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 roadways. 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 sections 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 conditioned as necessary, and compacted to a dry density 6960 Flanders Drive 0 San Diego, California 92121-2974 0 Telephone (858) 558-6900 0 Fox (858) 558-6159 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 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, we 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 IO?RO A. hane €dker * RCE 63291 SR: dmc (2) Addressee (1) Hunsaker and Associates Attention: Mr. David Blalock (3/del) Shea Homes Job Site Trailer Attention: Mr. Matthew Davey Project No. 07290-52-05 - 2 - January 4, 2005 FIGURE 1 PAVEMENT SECTION CALCULATIONS VILLAGES OF LA COSTA - THE RIDGE Corte Bosque - Stations 10+10 to 13+30 Use subgrade R-Value = 33.0 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)(100-33.0) -.83 =.24 feet from Table 608.4B Highway Design Manual with GF for Class 2 base = 1.1 Base thickness = 2.60 inches Use base thickness = 4.0 inches, City of Carlsbad Minimum *** Design Street Structural Section Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness = 4.0 inches. Corte Pacifica - Stations 10+10 to 12+50 Use subgrade R-Value = 37.0 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)(100-37.0) - .83 = .17 feet from Table 608.4B Highway Design Manual with GF for Class 2 base = 1.1 Base thickness = 1.91 inches Use base thickness = 4.0 inches, City of Carlsbad Minimum Design Street Structural Section *** Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness = 4.0 inches. Project No. 07290-52-05 January 4, 2005 FIGURE 1 (Continued) PAVEMENT SECTION CALCULATIONS VILLAGES OF LA COSTA - THE RIDGE Corte Pacifica - Stations 12+50 to 14+50 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, City of Carlsbad Minimum GS-17 *** Design Street Structural Section *** Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness = 5.0 inches. Project No. 07290-52-05 January 4, 2006 TABLE I SUMMARY OF R-VALUE TEST RESULTS ASTM D 2844-01 (CALIFORNIA TEST METHOD NO. 301) Sample Number Location R-Value R-9 Corte Bosque - Stations 10+10 to 13+30 33 R-10 Corte Pacifica - Stations 10+10 to 12+50 37 R-11 Corte Pacifica - Stations 12+50 to 14+50 22 TABLE II PAVEMENT SECTION RECOMMENDATIONS Location Traffic Index (TI) Asphalt Concrete (inches) Class 2 Aggregate Base (inches) Corte Bosque - Stations 10+10 to 13+30 5.0 4.0 1 4.0 Corte Pacifica - Stations 10+ 10 to 12+50 5.0 4.0 4.0 Corte Pacifica - Stations 12+50 to 14+50 5.0 4.0 5.0 Project No. 07290-52-05 January 4, 2005