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11.2 Soils Report - Addendum 2 V1MATERIALS %M0lllllll` TESTING & INSPECTION AN ATLAS COMPANY 8 February 2019 Page # 1 of 11 bl80977g_add2 ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections Mr. Jeff Harris Coleman Homes, A Toll Brothers Company 3103 West Sheryl Drive, Suite 100 Meridian, ID 83642 208-424-0020 Re: Addendum #2 — Infiltration Testing and Additional Pavement Recommendations Oaks North Subdivision Northeast Corner of McDermott Road and McMillan Road Meridian, ID Dear Mr. Harris: This addendum report presents test results not requested at the time of the previously issued MTI Geotechnical Engineering Report (13180977g). Descriptions of general site characteristics and the proposed project are available in the previous report. Unless otherwise noted in this addendum or the previous addendum, all initial recommendations, limitations, and warranties expressed in the previous report must be adhered to. Infiltration Testing Infiltration testing was conducted in general accordance with the Ada County Highway District (ACHD) Policy Manual. Test pit areas will need to be re -excavated and compacted prior to construction of structures that will be sensitive to settlement. Test locations were presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. Testing was conducted on 7 February 2019. Details and results of testing are as follows: Infiltration Testing Results Test Stabilized Design Test Depth Soil Type Infiltration Infiltration Rate Location (feet bgs) Rate (inches/hour) (inches/hour) JL TP-37 5.4 Poorly graded gravel with sand 6.24 3.12 TP-38 4.3 Sandy silt 1.2 0.6 TP-39 4.0 Sandy silt 0.24 0.12* TP-40 5.0 Poorly graded gravel with sand >8 I 8.0** *Per the ACHD Policy Manual, a minimum design infiltration of 0.5 inch per hour is required. **Per the ACHD Policy Manual, the maximum design infiltration rate is 8 inches per hour. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection MATERIALS %M0lllllll` TESTING 6 INSPECTION 8 February 2019 Page # 2 of I I bl80977g_add2 AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections In accordance with the ACHD Policy Manual, a factor of safety of 2 has been applied to the stabilized infiltration rates achieved during testing. MTI recommends that all infiltration facilities be constructed in accordance with the local municipality requirements Recommended Pavement Sections As required by Ada County Highway District (ACHD), MTI has used a traffic index of 8 to determine the necessary pavement cross-section for the proposed collector roadways. MTI 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. During the original investigation, MTI collected three samples of near -surface soils for Resistance Value (R-value) testing representative of soils to depths of 3.5 feet below existing ground surface. These samples, consisting of lean clay collected from test pits 11, 14, and 20, yielded R-values of 6, 15, and less than 5, respectively. For design, MTI elected to use an R-value of 5, which is considered representative of the overall subdivision. 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 in the Enclosures section. 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 sections. ACHD parameters for traffic index and substitution ratios, which were obtained from the ACHD Policy Manual, were also used in the design. A calculation sheet provided in the Enclosures section indicates the soils constant, traffic loading, traffic projections, and material constants used to calculate the pavement sections. MTI 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. Gravel Equivalent Method Flexible Pavement Specifications Pavement Section Component' Roadway Section Asphaltic Concrete 3.5 Inches Crushed Aggregate Base 6.0 Inches Structural Subbase 16.0 Inches Compacted Subgrade See Pavement Subgrade Preparation Section 'It will be required for MTI personnel to verify subgrade competency at the time of construction. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection MATERIALS %M0lllllll` TESTING & INSPECTION AN ATLAS COMPANY 8 February 2019 Page # 3 of I I bl80977g_add2 ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections Asphaltic Concrete: Asphalt mix design shall meet the requirements of ISPWC, Section 810 Class III plant mix. 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: Material complying with requirements for granular structural fill (uncrushed) as defined in ISPWC. Pavement Subgrade Preparation Uncontrolled fill, which contained debris, and plow zones (which should be treated as fill) were encountered in portions of the site. MTI recommends that these fill materials be excavated to a sufficient depth to expose competent, native soils or to a minimum depth of 11/2 feet below existing grade. If fill materials remain after over -excavation. the exposed subarade must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D698. MTI personnel must be present during excavation to identify these materials. 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 MTI 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. MTI anticipated that pavement areas will be subjected to moderate traffic. Subgrade clays and silts near and above optimum moisture contents may pump during compaction. Pumping or soft areas must be removed and replaced with structural fill. 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. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection MATERIALS ) TESTING & INSPECTION AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering Respectfully Submitted, Materials Testing & Inspection l.� Ni k Stevens, G.I.T. Staff Geologist Enclosures: Geotechnical General Notes Geotechnical Investigation Test Pit Logs Site Map ❑ Construction Materials Testing 8 February 2019 Page # 4 of l 1 b180977g_add2 ❑ Special Inspections Reviewed by: Monica Saculles, P.E. Senior Geotechnical Engineer Reviewed by: Jacob hlador, P.E. Geotechnical Engineer 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 www.mti-id.com • mtiCaQmti-id.com MATERIALS %M0lllllll` TESTING & INSPECTION AN ATLAS COMPANY February 2019 Page # 5 of 11 bl80977g_add2 ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections GEOTECHNICAL GENERAL NOTES RELATIVE DENSITY AND CONSISTENCY CLASSIFICATION Coarse -Grained Soils SPT Blow Counts (N) Fine -Grained Soils SPT Blow Counts (N) Very Loose: < 4 Very Soft: < 2 Loose: 4-10 Soft: 2-4 Medium Dense: 10-30 Medium Stiff: 4-8 Dense: 30-50 Stiff: 8-15 Very Dense: >50 Very Stiff: 15-30 Hard: >30 Moisture Content Description Field Test Dry Absence of moisture, dusty, dry to touch Moist Damp but not visible moisture Wet Visible free water, usually soil is below water table Cementation Descri don Field Test Weakly Crumbles or breaks with handling or slight finger pressure Moderately Crumbles or beaks with considerable finger pressure Strongly Will not crumble or break with finger pressure PARTICLE SIZE Boulders: >12 in. Coarse -Grained Sand: 5 to 0.6 nun Silts: 0.075 to 0.005 mm Cobbles: 12 to 3 in. Medium -Grained Sand: 0.6 to 0.2 mm Clays: <0.005 mm Gravel: 3 in. to 5 mm Fine -Grained Sand: 0.2 to 0.075 mm UNIFIED SOIL CLASSIFICATION SYSTEM Major Divisions Symbol Soil Descriptions Coarse -Grained Soils <50% passes No.200 sieve Gravel & Gravelly Soils <50% coarse fraction passes No.4 sieve GW Well -graded gravels; gravel/sand mixtures with little or no fines GP Poorly -graded gravels; gravel/sand mixtures with little or no fines GM Silty gravels; poorly -graded gravel/sand/silt mixtures GC Clayey gravels; poorly -graded gravel/sand/clay mixtures Sand & Sandy Soils >50% coarse fraction passes No.4 sieve SW Well -graded sands; gravelly sands with little or no fines SP Poorly -graded sands; gravelly sands with little or no fines SM Silty sands; poorly -graded sand/gravel/silt mixtures Sc Clayey sands; poorly -graded sand/gravel/clay mixtures Fine Grained Soils >50% passes No.200 sieve Silts &Clays LL < 50 ML Inorganic silts; sandy, gravelly or clayey silts CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium -plasticity clays OL Organic, low -plasticity clays and silts Silts & Clays LL > 50 MH Inorganic, elastic silts; sandy, gravelly or clayey elastic silts CH Fat clays; high -plasticity, inorganic clays OH Organic, medium to high -plasticity clays and silts Highly Organic Soils PT Peat, humus, hydric soils with high organic content 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mtkcl.com Copyright©2019 sopection Testing &Inspection MATERIALS %M0lllllll` TESTING 6 INSPECTION 8 February 2019 Page # 6 of 11 bl80977g_add2 AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-37 Date Advanced: 6 Feb 2018 Logged by: Nick Stevens, G.I.T. Excavated by: Struckman's Backhoe Service Location: See Site Map Plates Latitude: 43.65038 Longitude:-116.46949 Depth to Water Table: Not Encountered Total Depth: 5.4 Feet bgs Notes: Infiltration testing conducted at 5.4 feet bgs. Depth Field Description and USCS Soil and Sample Sample Depth Qp Lab (Feet bgs) Sediment Classification Type (Feet bgs) Test ID Lean Clay Fill (CL-FILL): Dark brown, 0.0-0.9 slightly moist, medium stiff. 0.75-1.0 --Some fine-grained sand and 8-inch minus cobbles noted throughout. 0.9-2.9 Lean Clay (CL): Dark brown, slightly moist 0.5-1.5 to moist, soft to stiff. Sandy Silt (ML): Whitish -tan to light brown, dry to slightly moist, very stiff to hard, with 2.9-4.3 fine-grained sand. --Intermittent weak to moderate calcium carbonate cementation noted throughout. Poorly Graded Gravel with Sand (GP): Gray 4.3-5.4 to tan, dry, dense, with fine to coarse -grained sand and 6-inch-minus cobbles. --Some clay content noted throughout. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection MATERIALS 8 February 2019 TESTING & Page # 7 of 11 INSPECTION bl80977g_add2 AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-38 Date Advanced: 6 Feb 2018 Logged by: Nick Stevens, G.I.T. Excavated by: Struckman's Backhoe Service Location: See Site Map Plates Latitude: 43.652049 Longitude:-116.473185 Depth to Water Table: Not Encountered Total Depth: 4.3 Feet bgs Notes: Infiltration testing conducted at 4.3 feet bgs. Depth (Feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth (Feet bgs) Qp Lab Test ID Lean Clay (CL): Dark brown, slightly moist, 0.0-2.9 stiff. 1.25-1.75 --Plow zone noted to a depth of 0.8 foot bgs. Sandy Silt (ML): Whitish -tan, dry to slightly 2.9-4.3 moist, hard, with fine-grained sand. --Intermittent weak to moderate calcium carbonate cementation noted throughout. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti@mti-id.com coPY�9ht©2019 sopectertion Testing &Inspection MATERIALS %M0lllllll` TESTING 6 INSPECTION 8 February 2019 Page #8ofII b180977g_add2 AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-39 Date Advanced: 6 Feb 2018 Logged by: Nick Stevens, G.I.T. Excavated by: Struckmans's Backhoe Service Location: See Site Map Plates Latitude: 43.649706 Longitude:-116.461384 Depth to Water Table: Not Encountered Total Depth: 4.0 Feet bgs Notes: Infiltration testing conducted at 4.0 feet bgs. Depth Feet bgs) Field Description and USCS Soil and Sediment Classification Sample Type Sample Depth Feet bgs) Qp Lab Test ID Lean Clay (CL): Dark brown, dry to slightly moist, stiff to very stiff. 0.0-3.5 --Plow zone noted to 0.7 foot bgs. 1.75-3.0 --Intermittent weak calcium carbonate cementation from 3.9 to 5.8 feet bgs. Sandy Silt (ML): Tan to light brown, dry to slightly moist, very stiff to hard, with fine to 3.5-4.0 medium -grained sand. --Intermittent weak to moderate calcium carbonate cementation noted throughout. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection MATERIALS %M0lllllll` TESTING 6 INSPECTION 8 February 2019 Page #9ofII bl80977g_add2 AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log #: TP-40 Date Advanced: 6 Feb 2018 Logged by: Nick Stevens, G.I.T. Excavated by: Struckman's Backhoe Service Location: See Site Map Plates Latitude: 43.652004 Longitude:-116.458787 Depth to Water Table: Not Encountered Total Depth: 5.0 Feet bgs Notes: Infiltration testing conducted at 5.0 feet bgs. Depth Field Description and USCS Soil and Sample Sample Depth Qp Lab Feet bgs) Sediment Classification Type Feet bgs) Test ID 0.0-1.5 Lean Clay (CL): Dark brown, slightly moist, 0.75-1.5 medium stiff to stiff. Sandy Silt (ML): Whitish -tan, dry to slightly moist, very stiff to hard, with fine to medium- 1.5-3.4 grained sand. --Intermittent weak to moderate calcium carbonate cementation noted throughout. Poorly Graded Gravel with Sand (GP): Gray 3.4-5.0 to tan, dry, very dense, with fine to coarse - grained sand and 7-inch-minus cobbles. 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection MATERIALS TESTING 6 INSPECTION 8 February 2019 Page # 10 of 11 bl80977g_add2 AN ATLAS COMPANY ❑ Environmental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections GRAVEL EQUIVALENT METHOD — PAVEMENT THICKNESS DESIGN PROCEDURES Pavement Section Design Location: Oaks North Subdivision, Collector Roadway Average Daily Traffic Count: Design Life: Traffic Index: Climate Factor: Subgrade CBR Value: R-Value of Aggregate Base: R-Value of Granular Borrow: Subgrade R-Value: Expansion Pressure of Subgrade: Unit Weight of Base Materials: Total Design Life 18 kip ESAL's: ASPHALTIC CONCRETE: Gravel Equivalent, Calculated: Thickness: Gravel Equivalent, ACTUAL: CRUSHED AGGREGATE BASE: Gravel Equivalent (Ballast): Thickness: Gravel Equivalent, ACTUAL: SUBBASE: Gravel Equivalent (Ballast): Thickness: Gravel Equivalent, ACTUAL: TOTAL Thickness: Thickness Required by Exp. Pressure: 2,000 All Lanes & Both Directions 20 Years 8.00 1 2.5 80 60 5 0.60 130 371,659 0.512 0.262564103 0.57 1.024 0.414 1.119 2.432 1.313 2.452 2.125 0.665 Design Depth Inches Asphaltic Concrete (at least 2.5): 3.50 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): 6.00 Subbase (at least 4.2): 16.00 R-Value of Subgrade: 5.00 Subgrade Mr: 3,750 ACHD Substitution Ratios 1.95 1.10 1.00 Use = 3.5 Inches Use = 6 Inches Use = 16 Inches 2791 S Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515 als www.mti-id.com • mti mti-id.com Copyright©2019 sopection Testing &Inspection Site Map Plate 1 NOTES: - Not to Scale • Aerial Photograph by Environmental Risk Information Services LEGEND i N C Approximate Site ------- Boundary I Approximate MTI Test 8 TP-25 Pit Location - Advanced 29 June 2018 TP-26 '� � � ' ® Approximate MTI Test 8 Pit Location - Advanced TP-20 = 16 July 2018 ® — TP-24 TP-21 Tg 8 8 TP-33 Approximate MTI Test ® TP-27 Pit Location - Advanced . �..... __ ® 29 October 2018 TP-36 TP-34 TP-28 � ® TP-35 ® ® Approximate MTI Test ® TP 23 TP-22 m TP 19 Pit Location - Advanced 8 ® ® 8 6 February 2019 0 TP-29 o ® �i Approximate MTI Test Pit Location with Piezometer TP 2 TP 3 TP 4 TP 5 TP 6 TP 7 TP 8 TP-9��i TP-38 TP-40 . ■ Oaks North Subdivision TP-1 T T Northeast Corner of McDermott Road _ B TP-13 and McMillan Road TP-39 0 „ t Meridian, ID TP -31 8 Modified by: NGS 1 TP 17 TP 16 TP 15 TP 12 TP-11 :� 8 February 2018 ® 8 ® Drawing: B180977g MCMILLAN ROAD 1 II 17 p R - MATERIALS TESTING & ►��tl' W" i� _- INSPECTION '� r1 .. _ _ — -- 1---�• ( 2791 S. Victory View Way Phone: 208 376-4748 — Boise, ID 83709-2835 Fax: 208 322-6515 I 'y � .� i� E-mail: mti@mti-id.com