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HomeMy WebLinkAboutCC - Geotech Report Add#1 �r'Irr-c��1 October 20, 2021 Atlas No. B212624g Mr. Kyle Enzler E5 Development, LLC PO Box 1613 Meridian, ID 83680 Subject: Addendum #1 —Pavement Recommendations Jasmine Lane Townhomes 2610 East Jasmine Lane Meridian, ID Dear Mr. Enzler: This addendum report presents test results unavailable at the time of the previously issued Atlas Geotechnical Engineering Report (B212624g). Descriptions of general site characteristics and the proposed project are available in the previous report. Unless otherwise noted in this addendum, all initial recommendations, limitations, and warranties expressed in the previous report must be adhered to. RECOMMENDED PAVEMENT SECTIONS Atlas has made assumptions for traffic loading variables based on the character of the proposed construction. The Client shall review and understand these assumptions to make sure they reflect intended use and loading of pavements both now and in the future. Atlas collected a sample of near-surface soils for Resistance Value (R-value) testing representative of soils to depths of 3.5 to 4.0 feet bgs. This sample, consisting of clayey sand collected from test pit 4, yielded a R-value of 21. The R-value was converted to a CBR value of 8 for design calculations. The following are minimum thickness requirements for assured pavement function. Depending on site conditions, additional work, e.g. soil preparation, may be required to support construction equipment. These have been listed within the Soft Subgrade Soils section of the original report. Results of the test are graphically depicted as an Attachment. Flexible Pavement Sections The American Association of State Highway and Transportation Officials (AASHTO) design method has been used to calculate the following pavement sections. Calculation sheets provided in the Attachments section indicate the soils constant, traffic loading, traffic projections, and material constants used to calculate the pavement sections. Atlas recommends that materials used in the construction of asphaltic concrete pavements meet requirements of the ISPWC Standard Specification for Highway Construction. Construction of the pavement section should be in accordance with these specifications and should adhere to guidelines recommended in the Construction Considerations section of the original report. Atlas No. B212624g Page11 Copyright©2021 Atlas Technical Consultants �TrT-G7T_�. Table 1 —AASHTO Flexible Pavement Specifications Pavement Section Component Driveways and Parking Driveways and Parkin,.r Light Duty Moderate DW Asphaltic Concrete 2.5 Inches 3.0 Inches Crushed Aggregate Base 4.0 Inches 4.0 Inches Structural Subbase 6.0 Inches 6.0 Inches Compacted Subgrade See Pavement Subgrade See Pavement Subgrade Preparation Section Preparation Section 'It will be required for Atlas personnel to verify subgrade competency at the time of construction. Asphaltic Concrete: Asphalt mix design shall meet the requirements of ISPWC, Section 810. Materials shall be placed in accordance with ISPWC Standard Specifications for Highway Construction. Aggregate Base: Material complying with ISPWC Standards for Crushed Aggregate Materials. Structural Subbase: Granular structural fill material complying with the requirements detailed in the Structural Fill section of this report except that the maximum material diameter is no more than 2/3 the component thickness. Gradation and suitability requirements shall be per ISPWC Section 801, Table 1. Pavement Subgrade Preparation Native clay soils are moderately plastic and will be susceptible to shrink/swell movements associated with moisture changes. Areas of the site within the proposed pavement sections should be excavated to sufficient depths to either completely remove clay soils or to expose clay soils and moisture condition as follows: The clay soils should be scarified to a depth of 6 inches and compacted between 92 to 98 percent of the maximum dry density as determined by ASTM D698. The moisture content should be within 2 percent of optimum. Structural fill should be placed as soon as possible after compaction of clay soils in order to limit moisture loss within the upper clays. Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, compacted (if indicated), inspected, and proof-rolled. Proof rolling of subgrade soils should be accomplished using a heavy rubber-tired, fully loaded, tandem-axle dump truck or equivalent. Verification of subgrade competence by Atlas personnel at the time of construction is required. Fill materials on the site must demonstrate the indicated compaction prior to placing material in support of the pavement section. Atlas anticipated that pavement areas will be subjected to moderate traffic. Subgrade clayey and silty soils near and above optimum moisture contents may pump during compaction. Pumping or soft areas must be removed and replaced with structural fill. Atlas No. B212624g Page 12 Copyright©2021 Atlas Technical Consultants �r'Irr-c��1 Fill material and aggregates, as well as compacted native subgrade soils, in support of the pavement section must be compacted to no less than 95 percent of the maximum dry density as determined by ASTM D698 for flexible pavements and by ASTM D1557 for rigid pavements. If a material placed as a pavement section component cannot be tested by usual compaction testing methods, then compaction of that material must be approved by observed proof rolling. Minor deflections from proof rolling for flexible pavements are allowable. Deflections from proof rolling of rigid pavement support courses should not be visually detectable. Atlas recommends that rigid concrete pavement be provided for heavy garbage receptacles. This will eliminate damage caused by the considerable loading transferred through the small steel wheels onto asphaltic concrete. Rigid concrete pavement should consist of Portland Cement Concrete Pavement (PCCP) generally adhering to ITD specifications for Urban Concrete. PCCP should be 6 inches thick on a 4-inch drainage fill course (see Floor Slab-on-Grade section of the original report), and should be reinforced with welded wire fabric. Control joints must be on 12- foot centers or less. If you have any questions, please call us at (208) 376-4748. Respectfully submitted, Bailey Hereford Monica Saculles, PE Engineering Technician Senior Geotechnical Engineer Attachments: AASHTO Pavement Design R-Value Laboratory Test Data Distribution: Teller Bard, Kimley-Horn (PDF Copy) Atlas No. B212624g Page 13 Copyright©2021 Atlas Technical Consultants �TrT-G7T�1. AASHTO PAVEMENT DESIGN Pavement Section Design Location: Jasmine Lane Townhomes,Light Duty Average Daily Traffic Count: 150 All Lanes&Both Directions Design Life: 20 Years Percent of Traffic in Design Lane: 50% Terminal Seviceability Index(Pt): 2.5 Level of Reliability: 95 Subgrade CBR Value: 8 Subgrade Mr: 12,000 Calculation of Design-18 kip ESALs Daily Growth Load Design Traffic Rate Factors ESALs Passenger Cars: 60 2.0% 0.0008 426 Buses: 0 2.0% 0.6806 0 Panel&Pickup Trucks: 12 2.0% 0.0122 1,298 2-Axle,6-Tire Trucks: 2 2.0% 0.1890 3,352 Emergency Vehicles: 1.0 2.0% 4.4800 39,731 Dump Trucks: 0 2.0% 3.6300 0 Tractor Semi Trailer Trucks: 0 2.0% 2.3719 0 Double Trailer Trucks 0 2.0% 2.3187 0 Heavy Tractor Trailer Combo Trucks: 0 2.0% 2.9760 0 A\erage Daily Traffic in Design Lane: 75 Total Design Life 18-kip ESALs: 44,807 Actual Log(ESALs): 4.651 Trial SN: 1.84 Trial Log(ESALs): 4.658 Pavement Section Design SN: 2.21 Design Depth Structural Drainage Inches Coefficient Coefficient Asphaltic Concrete: 2.50 0.42 n/a Asphalt-Treated Base: 0.00 0.25 n/a Cement-Treated Base: 0.00 0.17 n/a Crushed Aggregate Base: 4.00 0.14 1.0 Subbase: 6.00 0.10 1.0 Special Aggregate Subgrade: 0.00 0.09 0.9 Atlas No. B212624g Page14 Copyright©2021 Atlas Technical Consultants AASHTO PAVEMENT DESIGN Pavement Section Design Location: Jasmine Lane Townhomes,Moderate Duty Average Daily Traffic Count: 150 All Lanes&Both Directions Design Life: 20 Years Percent of Traffic in Design Lane: 50% Terminal Seviceability Index(Pt): 2.5 Level of Reliability: 95 Subgrade CBR Value: 8 Subgrade Mr: 12,000 Calculation of Design-18 kip ESALs Daily Growth Load Design Traffic Rate Factors ESALs Passenger Cars: 60 2.0% 0.0008 426 Buses: 1 2.0% 0.6806 6,036 Panel&Pickup Trucks: 10 2.0% 0.0122 1,082 2-Axle,6-Tre Trucks: 2 2.0% 0.1890 3,352 Emergency Vehicles: 1.0 2.0% 4.4800 39,731 Dump Trucks: 1 2.0% 3.6300 32,193 Tractor Semi Trailer Trucks: 0 2.0% 2.3719 0 Double Trailer Trucks 0 2.0% 2.3187 0 Heavy Tractor Trailer Combo Trucks: 0 2.0% 2.9760 0 Average Daily Traffic in Design Lane: 75 Total Design Life 18-kip ESALs: 82,820 Actual Log(ESALs): 4.918 Trial SN: 2.04 Trial Log(ESALs): 4.920 Pavement Section Design SN: 2.42 Design Depth Structural Drainage Inches Coefficient Coefficient Asphaltic Concrete: 3.00 0.42 n/a Asphalt-Treated Base: 0.00 0.25 n/a Cement-Treated Base: 0.00 0.17 n/a Crushed Aggregate Base: 4.00 0.14 1.0 Subbase: 6.00 0.10 1.0 Special Aggregate Subgrade: 0.00 0.09 0.9 Atlas No. B212624g Page 15 Copyright©2021 Atlas Technical Consultants �r'Irr-c��1 R-VALUE LABORATORY TEST DATA Source and Description: TPA @ 3.5'-4.0', Clayey Sand Date Obtained: September 21It, 2021 Sample ID: 21-0884 13212624G Sampling and Preparation: ASTM D75: AASHTO T2: X ASTM AASHTO X D421: T87: Test Standard: ASTM AASHTO Idaho T8: X D2844: T190: Sample A B C Dry Density (Ib/ft3) 115.1 115.1 115.9 Moisture Content % 14.3 15.1 15.7 Expansion Pressure (psi) 0.39 0.18 0.00 Exudation Pressure psi 3525 2200 1930 R-Value 33 17 6 R-Value @ 200 psi Exudation Pressure = 21 R-Value @ Exudation Pressure 33.0 29.0 25.0 m 21.0 17.0 13.0 9.0 5.0 300 250 200 150 Exudation Pressure (psi) Atlas No. B212624g Page 16 Copyright©2021 Atlas Technical Consultants