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Home My WebLink AboutPZ - GeoTech SITEPost Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC Luke Gilbert February 7, 2023 Constructive Company Page 1 of 10 Property Management File#23884-A 1065 South Allante Place Boise, Idaho 83709 Re: Geotechnical Recommendation Report Crowley Park Subdivision 4135 West Cherry Lane Meridian, Idaho Luke As per your authorization, SITE personnel logged and sampled two test pits on the referenced property. The test pits were excavated in the backyard or south end of the property. It is understood that the existing home in the north end of the property will remain but the out- building and awnings near the center of the property will be demolished. Four new residential units are planned each on a separate lot. Access to all new units will be a driveway planned along the east property line. A standard seepage trench is planned for stormwater injection. The property will be accessed from Cherry Lane to the north. Soil samples were gathered during excavation and were submitted to our in-house soil laboratory for the testing. Soil classifications and test results are reported on the Test Pit Logs. The two test pits were generally similar. The surface soil includes a sandy lean clay soil that extends to four feet deep. It is atop a weakly to firmly cemented silty sand that extends to eight to nine feet deep. Gravel contact occurred at this depth. According to Geologic Mapping (Othberg & Stanford — 1992) these sand and gravel soils are, "Sandy Alluvium of Side Stream Valleys and Gulches". Described as medium to coarse sand interbedded with silty sand and silt with pedogenic clay and duripan present. This reference accurately describes our observations in the test pits. Sloughing soils prevented excavation deeper than our fifteen-foot test pits. Groundwater was encountered at 14 feet deep in one test pit. It is noted that test pits were excavated in February, during the non-irrigation season. a Geotechnical Services/Soil Testing&Inspection Services SITE Post Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC RECOMMENDATIONS The following recommendations are based upon observed conditions and reported test results. • An existing out-building is to be demolished. Stripping of organic material in the planters and landscaped areas will require only minor excavation; 0-6" of grubbing can be anticipated to completely remove most organic materials. This is to be adjusted as needed in the field at the time of construction. Deeper excavation will be required where large trees or bushes are present and to remove any subsurface irrigation system. • While not anticipated based upon reviewed records, any encountered well and septic systems are to be properly abandoned as per IDWR and IDEQ requirements. • The surface soils encountered include sandy lean clay atop a weakly cemented silty sand. Building pads and foundations can be founded atop these native soils or atop structural fill extending to these soils provided inspection confirms they are firm, stable, and free of debris and organics. Compacting the exposed subgrade after excavation and prior to inspection is recommended. Subgrade inspection must confirm stability prior to the placement of structural fill. • Inspection after demolition and clearing and grubbing should confirm that all foundations, slab on grade concrete, pavement, tanks or vaults, and all organic materials including tree roots are removed from beneath future building pads and pavements. Any soils determined to be unacceptable are to be removed to firm bearing or a maximum depth of 1.5 feet and replaced with structural fill. Over excavation of unacceptable soils must extend laterally outside foundations a distance equal to the depth of fill. • Plastic soil (lean clay and elastic silt) may rut or deflect severely if wet when loaded with rubber tire equipment. Excessively wet or deflecting areas are to be over-excavated and repaired with structural fill. If wet weather or soils are present at the time of construction, tracked excavation and materials placement equipment should be utilized. • Native soils or ISPWC base or subbase can be used as structural fill to fill surface voids caused by demolition and elevate building pads. The inspected and approved subgrade and each lift of structural fill is to be compacted to a minimum of 95% of the maximum dry density as determined by ASTM D698, "Standard Proctor". This engineer can waive compaction testing after visual inspection of the subgrade. N on a Geotechnica/Services/Soil Testing&Inspection Services SITEPost Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC • Inplace testing to confirm proper compaction is required. Three tests per lift for every 5000 square feet or one test per building pad per lift of fill are recommended. Compacted native soil and structural fill must pass both testing and inspection requirements. Deflecting or excessively wet soils fail regardless of compaction results. • Settlements are not expected to exceed one-inch total and 1/2 inch differential if the following recommendations are followed. The proposed buildings may be supported on conventional, continuous, and isolated pad foundations. Foundations that are constructed atop the native, sandy lean clay or cemented sand can be designed to exert a net bearing pressure of up to 1500 psf. • Stormwater disposal can be accomplished with the planned conventional infiltration trench. The system must extend through the onsite cemented silty sand layer. Based upon soils observed in the test pits, the seepage trench should extend to at least ten feet deep. The depth to acceptable soil may vary across the site and is to be confirmed at the time of construction by the project civil or geotechnical engineer. • SITE recommends a design percolation rate of P=4 inches / hour based upon extending drainage facilities to the non-cemented silty sand with gravel encountered in the test pits at ten feet deep. • Based upon lean clay subgrade soils, the following pavement section is recommended: Structural Layer Recommended Thickness H MA 2.5" Base Course 4.0" Subbase 10.0" If the driveway pavement is to be completed before the building structures, SITE recommends increasing the section to 3.0"/4.0"/12.0." • Portland cement concrete is recommended for high traffic areas and areas of special loading such as dumpster storage, motorcycle parking and truck turning areas. • All site concrete shall be placed atop a minimum of 6" or properly compacted subbase atop an inspected and approved subgrade. Concrete thickness to meet ISPWC requirements for sidewalks. M a Geotechnical Services/Soil Testing&Inspection Services SITE Post Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC • HMA, Portland cement concrete, base, and subbase used in pavement construction are to meet the materials quality and placement requirements of ISPWC. 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, SITE Consulting, ILL �,pjONAL,1�� Bob J. Arnold, PE ¢ caRS7�,��'�� 0 /07/2023 OF ID�� A��® appendix follows. on a Geotechnical Services/Soil Testing&Inspection Services SITE Post Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC LOCATION MAP & PROPERTY INFORMATION �. Parcel Number: S1210212465 Information Parcel S1210212465 Primary Owner GILBERT RE HOLDINGS LLC Second I]wner Property Address 4135 W CHERRY LN Total Value $490,200 Subdivision 3N 1W 10 Zoning R1 Acres (Tax) 1.002 Acres (Calcnlated) 0.99 11 Legal 1 FAR#2465 OF NE4N.IJ4 Legal 2 SEC 10 3N 1,.q f.� r land DATA k.. `' N IL _ � I i - P-* F ` •• +# or IL IL r or dj:041 62 S& Landprodata.com L.n a Geotechnica/Services/Soil Testing&Inspection Services SITE Post Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC SITE PLAN in s�r,ss�s»Isal rw�•- I x resi► I �————� S I I �pE r R I IN 3: 7 FFF �1 £ sQ a tl • w w I t r n� ��p k 4 {Geili .V�}ki ' III' ■ F . E I .xi(..'• II _ Q4. x wV� C r T4 WAF {' !9 Ix I M � LJ. —-• I Clipped from Site Plan Supplied by Rock Solid Civil a Geotechnica/Services/Soil Testing&Inspection Services SITEPost Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC AERIAL PHOTO Test Pit Locations -.4135 Cherry Lrr, 'fV. 0 . + r t d 5 4 i kk TP-2 TP-1 •r. J (Google Earth) a Geotechnical Services/Soil Testing&Inspection Services SITEPost Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC TEST PIT LOG Test Pit: TP-1 File #: 23884-A Constructive Company Client: Property Management Date Excavated: 02/16/2022 Project: Crowley Park Subdivision Excavated By: Wood Brothers Location: 4135 Cherry Lane-Meridian Logged By: J. Meusch-SITE DEPTH SOILS DESCRIPTION (feet) 3/4" 1/2" 3/8" #4 # 10 #40 #100 #200 I %M I LL PI 0.0-4.0 Brown, Moist, Firm, Sandy, Lean Clay (CL) 2-6" Rootzone/organic Layer 3.0I 1 100 1 9 1 92 81 1 71.7 125.2 I 37 1 16 I 4.0-7.0 Brown/Tan, Moist, Firm, Weakly Cemented, Silty, Sand (SM) 6.0 100 98 1 94 1 80 1 62 1 36 1 23.9 1 17.6 1 32.8 NP 1 NP 7.0-9.0 Brown/Tan, Moist, Firm, Cemented, Silty, Sand with gravel (SM) 8.0 100 I 95 1 83 1 64 1 45 1 25 1 17 1 15.2 24.2 NP 1 NP I 9.0-11.0 Brown/Red, Moist, Firm, Silty, Sand with gravel (SM) 10.0 1 100 1 97 1 92 1 70 1 52 1 32 1 22 1 15.0 1 21.8 1 NP 1 NP 1 11.0-13.0 Brown, Wet, Firm, Silty Sand (SM) 12.0 I 100 1 9*8 1 93 1 88 -T82—T 58 1 35.7 122.8 I NP 1 NP I 13.0-15.0 Brown/Tan, Wet, Firm, Sand, Gravel, Cobble 15.0 Bottom of Excavation @ 15.0' No Ground Water Encountered Monitoring Well in Place 00 CUD o. Geotechnical Services/Soil Testing&Inspection Services SITEPost Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC TEST PIT LOG Test Pit: TP-2 File #: 23884-A Constructive Company Client: Property Management Date Excavated: 02/16/2022 Project: Crowley Park Subdivision Excavated By: Wood Brothers Location: 4135 Cherry Lane-Meridian Logged By: J. Meusch-SITE DEPTH SOILS DESCRIPTION (feet) 3/4" I 1/2" 13/8" I #4 I # 10 I #40 I #100 #200 I %M I LL PI 0.0-4.0 Brown, Moist, Firm, Sandy, Clay (CL) 2-6" Rootzone/organic Layer 3.0I 1 1 1 100 1 98 1 90 83 1 68.5 126.5 I 35 1 14 I 4.0-8.0 Brown/Tan, Moist, Firm, Cemented, Silt& Sand 8.0-13.0 Brown/Red, Moist, Firm, Silty, Sand, with gravel (SM) 9.0 100 I 98 1 95 1 86 1 79 1 55 1 32 1 17.8 116.1 I N P 1 N P I 13.0-15.0 Brown/Tan, Saturated, Firm, Sand, Gravel, Cobble 15.0 Bottom of Excavation @ 15.0' Ground Water Encountered @ 14.0' Monitoring Well in Place CUD o. Geotechnical Services/Soil Testing&Inspection Services SITEPost Office Box 190537 - Boise, Idaho 83719 site.consulting.idaho@gmail.com - 208-440-6276 CONSULTING, LLC SOIL LOG LEGEND UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM STANDARD TEST METHOD D 2487 FOR CLASSIFICATION OF SOIL FOR ENGINEERING PURPOSES) DIVISIONS TYPICAL DESCRIPTIONS GRAVEL& <5%-#200 GW Well-graded gravel,gravel-sand mixture,little or no fines. GRAVELLY GP Poorly graded gravel,gravel sand mixture,little or no fines SOILS 5-12%4200 GM Silty gravel,gravel-sand-silt mixtures COARSE <50%-#4 GRAINED >12%-#200 GC Clayey gravel,gravel-sand-clay mixtures SOILS <50%- SW Well-graded sand,gravelly sand, little or no fines. #200 SAND& <5%-#200 Poorly graded sand,gravelly sand,little or no fines SANDY FSP SOILS 50%-#4 >12%-#200 SM Silty sand,sand-silt mixtures > SC 11 Clayey sand,sand-clay mixtures ML Inorganic silt and very fine sand, rock flour,silty or clayey fine sand or clayey silt with slight plasticity SILTS AND INORGANIC CLAYS Lean clay-low to medium plasticity,gravelly clay,sandy clay, FINE LL<50% FL silty clay GRAINED SOILS ORGANIC OL To silt and organic silty clay of low plasticity >50%- IF #200 MH Elastic silt,micaceous or diatomaceous fine sand or silty soil. SILTS AND INORGANIC CLAYS CH 11 Fat clay-high plasticity LL>50% ORGANIC OH Organic clay-med.or high plasticity:organic silt ORGANIC SOILS PT Peat, humus,swamp soil with high organic content ABBREVIATIONS AND ACRONYMS AASHTO American Association of State Highway & Transportation Officials HMA Hot Mix Asphalt (Pavement) ASTM American Society for Testing and Materials IDWR Idaho Department of Water Resources ISPWC Idaho Standard for Public Works Construction NP Non-Plastic VNP Visually Observed to be non-Plastic PCC Portland Cement Concrete PSF Pounds per Square Foot TP Test Pit USCS Unified Soil Classification System 0 Nothing Follows a Geotechnical Services/Soil Testing&Inspection Services