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2021-10-25 Geotech Report October 25, 2021 Atlas No. B212623g Mr. Kyle Enzler E5 Development, LLC PO Box 1613 Meridian, ID 83680 Subject: Addendum #1 —Pavement Recommendations Pollard Subdivision NEC Pollard Lane & Old School Lane Meridian, ID Dear Mr. Enzler: This addendum report presents test results unavailable at the time of the previously issued Atlas Geotechnical Engineering Report (B212623g). 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 As required by Ada County Highway District (ACHD), Atlas has used a traffic index of 6 to determine the necessary pavement cross-section for the site. Atlas has made assumptions for traffic loading variables based on the character of the proposed construction. The Client should review 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 2.0 to 2.7 feet bgs. However, because of the presence of induration and calcium carbonate cementation within the sample, usable R-value test results were unable to be obtained. Based on laboratory testing completed on a project adjacent to the site, an R-value of 12 was achieved for the onsite silt with sand soils. 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. Atlas No. 13212623g Page 1 1 Copyright©2021 Atlas Technical Consultants Flexible Pavement Section The Gravel Equivalent Method, as defined in Section 500 of the State of Idaho Department of Transportation (ITD) Materials Manual, was used to develop the pavement section. ACHD parameters for traffic index and substitution ratios, which were obtained from the ACHD Policy Manual, were also used in the design. Calculation sheet provided in the Attachment section indicate the soils constant, traffic loading, traffic projections, and material constants used to calculate the pavement section. Atlas recommends that materials used in the construction of asphaltic concrete pavements meet the 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 Table 1 — Gravel Equivalent Method Flexible Pavement Specifications ComponentPavement Section Asphaltic Concrete 2.5 Inches Crushed Aggregate Base 4.0 Inches Structural Subbase 12.0 Inches Not Required for Native Soils Compacted Subgrade 12.0 Inches to 95% of ASTM D698 for Existing Fill Materials '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. Common Pavement Section Construction Issues The subgrade upon which above pavement sections are to be constructed must be properly stripped, 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. Atlas does not anticipate pumping material to become evident during compaction, but subgrade clays and silts near and above optimum moisture contents may tend to pump. Pumping or soft areas must be removed and replaced with structural fill. Atlas No. 13212623g Page 12 Copyright©2021 Atlas Technical Consultants Fill material and aggregates 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. If you have any questions, please call us at (208) 376-4748. Respectfully submitted, AL \C NSFoNc/yF 14919 10-25-21 Bailey Hereford Monica Saculles, P 5 41, OF �oP�� ) Engineering Technician Senior Geotechnical C?�e�i���-�' Attachments: Gravel Equivalent Method Pavement Design Distribution: Dave Yorgason (PDF Copy); Teller Bard, Kimley-Horn (PDF Copy) Atlas No. 13212623g Page 13 Copyright©2021 Atlas Technical Consultants GRAVEL EQUIVALENT METHOD PAVEMENT DESIGN Pavement Section Design Location: Pollard SubdiNsion, Residential Roadways Average Daily Traffic Count: All Lanes&Both Directions Design Life: 20 Years Traffic Index: 6.00 Climate Factor: 1 R-Value of Subgrade: 12.00 Subgrade CBR Value: 5 Subgrade Mr: 7,500 R-Value of Aggregate Base: 80 R-Value of Granular Borrow: 60 Subgrade R-Value: 12 Expansion Pressure of Subgrade: 0.19 Unit Weight of Base Materials: 130 Total Design Life 18 kip ESAL's: 33,131 ASPHALTIC CONCRETE: Gravel Equivalent,Calculated: 0.384 Thickness: 0.196923077 Use= 2.5 Inches Gravel Equivalent,ACTUAL: 0.41 CRUSHED AGGREGATE BASE: Gravel Equivalent(Ballast): 0.768 Thickness: 0.329 Use= 4 Inches Gravel Equivalent,ACTUAL: 0.773 SUBBASE: Gravel Equivalent(Ballast): 1.690 Thickness: 0.917 Use= 12 Inches Gravel Equivalent,ACTUAL: 1.773 TOTAL Thickness: 1.542 Thickness Required by Exp. Pressure: 0.210 Design ACHD Depth Substitution Inches Ratios Asphaltic Concrete(at least 2.5): 2.50 1.95 Asphalt Treated Base(at least 4.2): 0.00 Cement Treated Base(at least 4.2): 0.00 Crushed Aggregate Base(at least 4.2): 4.00 1.10 Subbase(at least 4.2): 12.00 1.00 Atlas No. 13212623g Page 14 Copyright©2021 Atlas Technical Consultants