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Home My WebLink AboutPZ - Geotechnical Report SITE CONSULTING, LLC Mr. Doug Jayo November 25, 2018 Jayo Construction, Inc. Page 1 of 14 1309 South Five Mile Street File# 18011-13 Boise, Idaho 83703 Re: Geotechnical Recommendations Proposed Cherry Blossom Place Subdivision 615 West Cherry Lane Meridian, Idaho Doug: On March 28, 2017, SITE excavated three test pits on the referenced property. These test pits were excavated on a single parcel (#S1212120850) located on the south side of Cherry Lane, just east of NW 7t" Street. The client provided an address of 615 West Cherry Lane for the subject property. This was confirmed on the Ada County Assessor's website which also indicated the property includes 9.25 acres. It is understood that three lot size parcels, two to the west and one to the east, have been added to this development since our field investigation was completed. No additions or changes to this recommendation report are required due to the addition of these parcels. Based upon our research, observations, and laboratory test results, the site is acceptable for the proposed residential subdivision development. Recommendations for construction are included herein. We appreciate this opportunity to be of service. When appropriate, we would like to discuss continuing our role as geotechnical consultant during construction. Please contact our office if additional information or services are required. Respectfully submitted, Bob J. Arnold, PE SITE Consulting, LL OAL 208-440-6276 * bjarnoldpe@msn.com * Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC INVESTIGATION SITE's original field investigation was undertaken at the request of another developer that terminated their interest in developing this property. Test pit logs and soil samples gathered during our March 2017 field investigation were placed in inventory and the current client contacted after their acquisition of the property. Jayo Construction has contacted with SITE to complete this geotechnical report. In March 2017 SITE staff observed the excavation of three test pits at locations intended to provide full coverage of the subject property. Test pit logs and an aerial photo with test pit locations are included in the Appendix. At the time of our investigation the surface was firm and stable allowing complete access to the property. Historical aerial photos available on Goggle Earth confirm the property has historically been pastureland or farmland. No evidence of former buildings or structures were observed in the field or within the research. In general, surface soils consist of a lean clayey to non-plastic silt / sand soil. A shallow rootzone / organic layer is present in this surface layer that was observed to be two to three feet deep. Below this, a weakly cemented silt / sand soil was encountered. This layer extends to as deep as nine feet in TIP-W, but was typically less than six feet deep. Native gravel was contacted at six feet deep in two of three test pits. Sand and gravel are present below this depth grading cleaner and coarser with increased depth. The native pitrun (sand and gravel) was free flowing and would collapse or slough into the pits faster than excavation and therefore test pits were terminated at shallow depths. Groundwater was not contacted in any of our test pits. Free draining soils were typically present at eight feet deep but were greater than 10 feet deep in TIP-W. Additional research was performed to further evaluate the depth to groundwater. Research included reviewing published geotechnical data and well logs on the IDWR website database. The Ada County Soil Survey, (US Soil Conservation Service) indicates the onsite groundwater should be greater than 80 inches below the existing ground surface. Wells logs reviewed on the IDWR website also indicate the groundwater is greater than 10 feet deep. Numerous wells at the Jackson Station across Cherry Lane (522 West Cherry) indicate groundwater is 12-15 feet deep. Wells at 4th & Cherry Lane and 1158 W. 7th Street are east and west of the subject property and indicate the static groundwater is 11 and 9 feet deep respectfully. 208-440-6276 * bjarnoldpe@msn.com (2) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC RECOMMENDATIONS Site Work Grubbing depths of up to 2 to 6 inches can be anticipated to remove most organic materials. Roots may exist as deep as two feet below the ground surface where large trees and ditches are or were located and along former irrigation ditches. Therefore, stripping depth is to be adjusted in the field at the time of construction. Excavations caused by grubbing of ditches or over excavation of soft or wet areas are to be backfilled with structural fill. All subgrade soils present in the test pits can be used as structural fill on building lots and within right of ways. If encountered, blending clay surface soils with onsite or imported sand and gravels will improve surface drainage. Compaction of any fill placed within building pads or right of ways must exceed 95% of the maximum dry density as determined by Standard Proctor testing. It should be anticipated that the Meridian City Engineering and / or Building Department will request these test results prior to or at the time of home construction. Structural fill must pass compaction testing and visual inspection for stability. Fill that passes compaction but is observed to rut or deflect under construction traffic is to be rejected Pavement Sections A sample of the near surface sandy silt was gathered and sent to a specialty soil lab for R-Value Testing. Results from Pavement Engineering Inc are attached and indicate an R-Value of R>20 was obtained on the submitted sample. Based upon this value, and a traffic Index of TI=6 (residential street), a pavement section of 2.5" / 4.0" /12.0" is recommended for all subdivision interior streets. All materials and methods used in the construction of streets and sidewalks are to comply with ACHD and ISPWC requirements. 208-440-6276 * bjarnoldpe@msn.com (3) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC Residential Foundation System The proposed single-family residential structures may be supported on conventional, continuous, and isolated pad foundations founded upon the native soils or upon structural fill extending to these soils. Based upon proper placement and compaction of structural fill, bearing pressures of up to 1500 psf are allowed for foundations founded on the native soils or upon properly placed and compacted structural fill. Either crawlspaces or slab on grade floors are acceptable. Foundation drains are not required for this development. Foundations are to be properly embedded at least 24" below adjacent grade for frost protection. Outside of crawlspaces and basements the foundation is to be waterproofed with spray or brushed on foundation mastic. Slab on Grade Concrete Care must be taken so that all excavations below both interior and exterior slab on grade concrete are properly backfilled in accordance with the structural fill recommendations. Trenches and wall backfill areas are to be filled in lifts and benched each lift so that fill is not placed against a vertical soil face greater than three feet tall. Areas of excessive yielding should be excavated and backfilled with structural fill. Any fill used to increase the elevation of slab on grade concrete should meet the requirement for structural fill. Slab on grade floors, sidewalks, patios, driveways, and other pavements should be placed atop a mat of at least 0.5 feet of granular structural fill materials. This depth is to increase to one foot when concrete is to be placed over clay soil. This is required to prevent seasonal heaving of sidewalks, patios, garage floors, and driveways. Mat material should all pass a 3/4-inch sieve and should contain less than seven percent passing the # 200 sieve. The mat shall be compacted to the requirement for structural fill. Storm Water It is recommended that storm runoff be directed away from all open excavations and not be allowed to puddle on subgrade soils. SITE recommends a design percolation rate of P=8 inches per hour with a drain time of less than 24 hours for facilities that extend to the free draining sand and gravel encountered in our test pits. Free draining materials and the percolation rate is to be confirmed at the time of construction. 208-440-6276 * bjarnoldpe@msn.com (4) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC Inspection & Testing A qualified engineer or his representative should monitor fill placement to ensure the work is performed in accordance with these recommendations. Testing should be performed in accordance with ASTM Test Methods D3017-88 and D2922-91 (nuclear densometer). For mass filling, field nuclear moisture - density testing shall be performed on each lift, on each residential lot. Trench backfill and right of ways are to be tested to ACHD / ISPWC requirements. It is noted that structural fill can pass compaction tests and still be unacceptable if pumping, rutting, or deflecting under vehicle or foot traffic. General Comments After the plans and specifications for construction are completed, it is recommended that this consultant be provided the opportunity to review the final design and specifications. This review will confirm that the earthwork recommendations have been properly interpreted and implemented. At that time, it may be necessary to submit supplementary recommendations. This review is a part of this service and will not result in additional invoicing unless additional research and recommendations are needed. Testing and inspection services are recommended herein. Proper quality control during construction is required to confirm materials and methods and thereby obtain a desirable finished product. Monitoring and testing should also be performed to verify suitability of materials used for structural fills and to confirm proper demolition, subgrade grubbing, subgrade stability, and proper placement and compaction of fills. Any deviations from the herein described subsurface conditions must be brought to the attention of this consultant. This report has been prepared for the exclusive use of the client and their retained design consultants. Findings and recommendations within this report are for specific application to the proposed construction described herein and apply only to the property identified. Appendix Follows 208-440-6276 * bjarnoldpe@msn.com (5) Post Office Box 190537 * Boise, Idaho 83719 CONSITE SULTING, LLC APPENDIX Conceptual Plan Aerial Photo with Test Pit Location Test Pits Logs (3) Soil Log Legend / Abbreviations and Acronyms Pavement Section Calc Sheets R-Value Report 208-440-6276 * bjarnoldpe@msn.com (6) Post Office Box 190537 * Boise,Idaho 83719 CONSITE SULTING, LLC Conceptual Plan 1 ,c ® c U IIr[f i 1 '�1 1 4 a __- I-` ----- r,} O I Supplied by Client 208-440-6276 * bjarnoldpe@msn.com (7) Post Office Box 190537 * Boise,Idaho 83719 r mwk El JL dft TP-N 4900 * ; 4 TP-W T P_E O, .,,I SITE CONSULTING, LLC TEST PIT LOG Test Pit: TP-N File#: 18040-B Client: Jayo Construction Date Excavated: 03/28/17 Project: Cherry Blossom Place Excavated By: Culver Excavation Location: North End of Property Logged By: B. Arnold, PE -SITE DEPTH SOILS DESCRIPTION feet 3/4" 1/2" 3/8" #4 #10 #40 #100 #200 %M LL PI 0.0 Brown, Dry, Firm,Sandy,CLAY - With rootzone/organic layer 4-6" 3.0 R-Value Sample R=23 2.0 1 100 1 98 1 97 96 89 79 68.5 19.5 1 43 1 20 3.0 Brown,Moist,Firm,Weakly Cemented,Silty,SAND(SM) 5.5 5.0 100 1 73 1 57 1 47 1 31 23 16.7 11.1 I NP NP 5.5 Cemented Silt/Hardpan Layer 6.0 6.0 Gravel Contact 6.0 PITRUN type sand and gravel with non-plastic fines - Free draining at 8.0 below existing ground surface. 10.0 8.0 scalped 1 100 1 92 1 88 1 80 1 24 3 1.2 1.9 NP NP 10.0 Bottom of Excavation No Groundwater Encountered Sloughing Soil prevented deeper reach. 208-440-6276 * bjarnoldpe@msn.com (9) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC TEST PIT LOG Test Pit: TP-W File#: 18040-B Client: Jayo Construction Date Excavated: 03/28/17 Project: Cherry Blossom Place Excavated By: Culver Excavation Location: West side, south end Logged By:1 B. Arnold, PE -SITE DEPTH SOILS DESCRIPTION feet 3/4" 1 1/2" 1 3/8" 1 #4 1 #10 #40 #100 #200 1 %M I LL PI 0.0 Brown, Dry,Firm,Sandy,CLAY - With rootzone/organic layer 4-6" 2.0 2.0 Brown,Moist,Firm,Weakly Cemented,Silty,SAND(SM) 9.0 3.0 100 1 92 1 87 1 72 1 57 45 34.8 21.8 NP NP 9.0 Gravel Contact 9.0 PITRUN type sand and gravel - Free draining at 11.0 below existing ground surface. 13.0 13.0 Bottom of Excavation No Groundwater Encountered Sloughing Soil prevented deeper reach. 208-440-6276 * bjarnoldpe@msn.com (10) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC TEST PIT LOG Test Pit: TP-E File#: 18040-B Client: Jayo Construction Date Excavated: 03/28/17 Project: Cherry Blossom Place Excavated By: Culver Excavation Location: East side, south end Logged By:J B. Arnold, PE -SITE DEPTH SOILS DESCRIPTION feet 3/4" 1 1/2" 1 3/8" 1 #4 1 #10 #40 #100 #200 %M LL PI 0.0 Brown, Dry,Firm,Sandy,CLAY - With rootzone/organic layer 4-6" 2.5 2.5 Brown,Moist,Firm,Weakly Cemented,SILT SAND 6.5 6.5 Gravel Contact 6.5 PITRUN type sand and gravel - Free draining at 8.0 below existing ground surface. 11.5 11.5 Bottom of Excavation No Groundwater Encountered Sloughing Soil prevented deeper reach. 208-440-6276 * bjarnoldpe@msn.com (11) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC SOIL LOG LEGEND UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM STANDARD TEST METHOD D 2487 FOR CLASSIFICATION OF SOIL FOR ENGINEERING PURPOSES MAJOR DIVISIONS J=FTYPICAL DESCRIPTIONS GRAVEL& <5% #200 =1 Well-graded gravel, ravel-sand mixture, little or no fines. GRAVELLY GP Poorl raded gravel,gravel sand mixture, little or no fines COARSE SOILS 5-12%-4723001=1 Silty gravel, ravel-sand-silt mixtures GRAINED <50%-#4 >12%-#200 1=1 Clayey ravel,gravel-sand-clay mixtures SOILS SAND& <5% #200 =1 Well-graded sand,gravelly sand,little or no fines. <50%-#200 SANDY = Poorl - raded sand,gravelly sand, little or no fines SOILS >12%-#200 SM Silty sand,sand-silt mixtures >50%-#4 SC Clayey sand,sand-clay mixtures SILTS& INORGANIC El Inorganic silt and very fine sand, rock flour,silty or clayey fine sand or clayey silt with slight plasticity FINE CLAYS CL Lean clay-low to medium plasticity,gravelly,sandy,or silty clay GRAINED LL<50% ORGANIC OL Organic silt and organic silty clay of low plasticity SOILS SILTS& INORGANIC MH Elastic silt,micaceous or diatomaceous fine sand or siltv soil. >50%-#200 CLAYS CH Fat clay-high 'plasticity LL>50% ORGANIC OH Organic cla -med.or high plasticity:organic silt HIGHLY ORGANIC SOILS PT Peat, humus,swamp soil with high organic content ABBREVIATIONS AND ACRONYMS ASTM American Society for Testing and Materials IBC International Building Code ISPWC Idaho Standard for Public Works Construction ITD Idaho Transportation Department NP Non Plastic PCC Portland Cement Concrete TP Test Pit USCS Unified Soil Classification System cf Pounds per Cubic Foot sf Pounds per Square Foot tsf Tons per Square Foot sf/f Pounds per Square Foot/ Foot 208-440-6276 * bjarnoldpe@msn.com (12) Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC DESIGN SECTION CALCULATIONS (ACHD R-Value Method) Project: Cherry Blossom Place File No.: 18040-B Cherry Lane - Meridian, Idaho Caic By: B. Arnold Client: Jayo Construction Date: 11/25/18 Design Thickness Equation: T= 0.0032 (TI) (100-R)(12) = GE (inches) T= Design Thickness TI = Traffic Index = 6 ACHD GE = Gravel Equivalent R = R-Value = 10 Soil Sample GE= 21.2 Inches ACHD ACID, 3/4" Road Base and Aggregate Subbase Actual Thickness Equivalent Thickness ACHD Asphalt Concrete Thickness = 2.5 Inches ACE= 5.0 Inches 3/4" Road Base Thickness Desired = 4.0 Inches RBE= 4.4 Inches Calculated Aggregate Subbase Thickness Equation: Subbase Thickness=SB=GE-ACE-RBE SB= 11.8 Inches CALCULATED DESIGN SECTION ACHD Asphaltic Concrete= 2.5 inches 3/4" Road Base = 4.0 inches Aggregate Subbase = 12.0 inches RECOMMENDED DESIGN SECTION Asphaltic Concrete = 2.5 inches 3/4" Road Base = 4.0 inches Aggregate Subbase = 12.0 inches 208-440-6276 * bjarnoldpe@msn.com (13) Post Office Box 190537 * Boise, Idaho 83719 C0N:SITE SULTING, LLC CONTRACTED R-VALUE Pavement Engineering Inc. Redding•San Luis Obispo fil Caltrans`iAMPL/CC•CA RESISTANCE(R)VALUE TEST ASTM D 2844 Laboratory No.: L170355 Project No.: 170023 Sample Date: NIA Report Date: April 25.2017 Client: Site Consulting LLC Project Name: 2017 Laborato Testing Sample Description: Brown Silty Clay Sample Location: McFadden 100 90 80 70 60 50 s` 40 M 30 20 10 0 800 700 600 500 400 300 200 100 0 Exudation Pressure (P.S.I.) —Resistance Value Test —300 P.S.I. 1 Specimen No. 7 8 9 Moisture Content % 26.6 24.6 24.0 Dry Density(PCF) 95.5 97.3 96.5 Resistance Value R) 8 30 38 Exudation Pressure(PSt) 153 374 479 Expansion Pressure 17 43 87 As Received Moisture Content(%) 26.6 RESISTANCE VALUE AT 300 P.S.I. 23 AI�QReviewed By: Brandon � Rodebaugh Materials Engineer Nothing Follows 208-440-6276 * bjarnoldpe@msn.com (14) Post Office Box 190537 * Boise, Idaho 83719