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Home My WebLink AboutCT 02-24; VILLAGES OF LA COSTA GREENS 1.11, 1.13, 1.14; PAVEMENT RECOMMENDATIONS BIXBITE PLACE AND GALENA ROAD; 2004-12-27CT 02-24 GEOCON. INCORPORATED GEOTECHNICAL CONSULTANTS (410>) Project No. 06403-52-16B , December 27, 2004 .. r . - - 1oIo John Laing Homes 6183 Paseo Del Norte, Suite 160 Carlsbad, California 92009 Attention: Ms. Liz Albano Subject: VILLAGES OF LA COSTA—THE GREENS NEIGHBORHOOB.l.1 B[XBITE PLACE STATION 10+00 TO12+60 GALENKROAD STATION 22+00TQ26±00 CARLSBAD, CALIFORNIA PAVEMENT RECOMMENDATIONS Dear Ms Albano: In accordance with your request, we have performed supplemental geotechnical services for the subject roadway alignments within Villages of La Costa - The Greens development. The scope of our Services included obtaining representative subgrade soil samples within the street areas and performing Resistance Value (RVa1ue) test. 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 for. La Costa Greens - Neighborhobd 1. 11, 1. 13, 1.14, prepared by Hunsaker and Associates (Drawing No. 406-3), City of Carlsbad approval dated May 6, 2004; and our report entitled Update Geotechnical Report, Villages of La Costa - The Greens,, Neighborhoods 1.1]; '1.13, and L14, Carlsbad, Calfbrnia, dated July 28, 2004 (Project No. 06403-52-16). Subgrade soils in the area are predominately sandy clays and silt' sand, and typically exhibit rltiVëli low -RValue'characteristics. Based on field observations arid previous laboratory tests, subgrade rnaterial (Ekpansion Index-'of 90 oi less), as defined by Uniform Building Code (TJBC) 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 Jndex((T ofö has been assigned to the roadway alignments. It should be noted that a 0 portion of Galena Road was paved during the construction of Alicante Road. The City of Carlsba construction inspector has indicated that the pavement section for the subject section of Galena Road should match that of the existing portion. Based- on the above information and laboratory testing, we 6960 Flanders Drive • SanDieo, California 92121L2974. • Telephone (858)558-6900 ' Fax (858) 558-6159 _*,',•_' y' •,,,. - ...'.. .'.p• '. '' t ' recommend the pavement sections indicated on Table IL Pavement section calculations were performed in accordance with Calfornia 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 J. These recommended sections should be considered preliminary with final sections to be determined and approved by the City of Carlsbad. As indicated on T.ble I, the i72. It is our understanding that the City of Carlbad requires testing for lime treatment of subgrade soils when the R-Value is less than 12. Therefore, additional laboratory testing was performed to assess the actual amount of lime required to effectively treat the subgrade soils. We selected a sample of a similar 'soil type from an adjacent neighb6rhood (Sample No. R-4, Goldstone Road from Neighborhood 1.14) with the R-Value test result of 5. The laboratory test method was based on Texas Method, .which consists of performing a series of Plasticity Index (P1) tests at different lime contents until the PT, 'stabilizes. Table ifi shows' the result of the P1 testsversus lime content. It is our opinion that 3.5 peráent Quick Lime by dry weight (or 4.5 percent hydiated lime) is required to stabilize clayy subgrade. Supplemental R-Value testing of the lime treated materials shows that the R-Value' inreased to. 70. Table IV provides alternative recommended pavement sections that incorporate a lime-treated subgrade. The minimum thickness of lime-treated subgrade is estimated to be 6 inches. It has been our experience that lime treatment is most effective when' used in situations where clays of "high" expansion, potential (Expansion Index of 90 or highr) are present. Due to the presence of silty sands and 'clays with "low" to "medium" expansion potential, - .-.---------- - .-------------- - 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 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 should 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 should be compacted to a density of at.least 95 percent of the laboratory Hveem density in accordance with ASTM D 2726-00. The upper 12 inches of subgrade beneath areas to receive concrete sidewalks 'should 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 base lift thickness should not exceed 6 inches. Class 2 aggregate base and asphalt concrete should conform to the City of Carlsbad specific'átions. ', ' 1 •' ' ' The performance of asphalt concrete pavement is highly dependent on providing positive surface drainage away from the edge of the pavement Ponding of watr on or adjacent to the pavemnt will likely result in pavement distress ãndsubgade failure. Tr'ditce the occurrence-for such situations, we recommend that a minimum drainage gradient of 1 perc,ent be maintained for pavement surfaces. Drainage form làñdscaped areas-should be directed to controlled drainage structures. Project No. 06403-52-16B -2- ' December 27, 2004 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 N. Roo -Shane Rodacker CI) No. 63291 M RCE 63291 Fxp .6130/06 SR:dmc ..' - OF C (2) Addressee (1) Hunsaker and Associates Attention: Mr. David Blalock (3/del) John Laing Homes C/ Devenco; La Costa Greens Job Site Attention: Mr. Will Bigler Project No. 06403-52-16B - 3 - December 27, 2004 TABLEI SUMMARY OF R-VALUE TEST RESULTS ASTM D 2844-01 (CALIFORNIA TEST METHOD NO. 301) Sample Number Location k-Value R-3 Galena Road Station 22+00 to 24+00 16 R-4 Bixbite Place Station 10+00 to 12+60 11 R-5 Galena Road Station 24+00 to 26+00 8 TABLE 11 PAVEMENT SECTION RECOMMENDATIONS - IONAL Location Traffic Index Asphalt Concrete Class 2 ggr egate Base (TI) / (inches) ches) Galena Road Station 22+00 to 24+00 5.0 4 Bixbite Place Station 10±00 to 12+60 50 4 7 'Galena Road Station 24+00 to 26+00 5.0 4 7 TABLE III SUMMARY OF PLASTICITY INDEX VS. LIME CONTENT SAMPLE NO. R-4 - GOLDSTONE ROAD Plasticity Index (PI) . ' Percent Lime 29 0 22 3 19 4 18 ', 5 16 6 Project No. 06403-52-16B . . December 27, 2004 TABLE IV ALTERNATIVE PAVEMENT SECTION ECOMMENDATIONS LIME-TREATED S9BRADE .7' L.raffic Asphalt Class 2 Minimum Location ' Index . Concrete Aggregate. Lime-Treated (inches) Base Subgrade (inches) . (inches) Bixbite Place Station 10+00 t9A2+60 5.0 4 4 6 Galena Road Station 24-2o 26+00 5.0 4 6 Project No. 06403-52-16B . . . . December 27, 2004 FIGURE 1 PAVEMENT SECTION CALCULATIONS VILLAGES OF LA COSTA - THE GREENS Galena Road - Station 22±00 to 24+00 Use subgrade R-Value = 16.0 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)(100-16.0) - .83 = .51 feet from Table 608.4B Highway Design Manual.with GF for Class 2 base = Base thickness = 5.57 inches Use base thickness =%0 inches 7 Design Street Structural Section Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness =$.0 inches. 1 Bixbite Place Station 10+00 to 12+60 Use subgrade R-Value = 11.0 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 6084B 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)(100-110) - .83.= .59 feet from Table 608.4B Highway Design Manual with GF for Class 2 base = Base thickness = 6.44 inches -" Use base thickness = 7.0 inches Design Street Structural Section Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness = 7.0 inches. Project No. 06403-52-16B S December 27, 2004 FIGURE 1 (Continued) ;fl •. "PAVEMENT SECTION CALCULATIONS. VILLAGES OF LA COSTA- THE GREENS Galena Road - Station 24+00 to 26+00 Use subgrade R-Value = 8.0 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 = 265 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- 8.0) -.83 = .64 feet from Table 608.4B Highway Design Manual with GF for Class 2 base 1.1 Base thickness = 6.97 inches Use base thickness = 7.0 inches Design Street Structural Section Asphalt Concrete Thickness = 4.0 inches. Class 2 Aggregate Base Thickness = 7.0 inches. '1 Project No. 06403-52-16B . December 27, 2004