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Home My WebLink AboutPZ - Geotech Report ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 Mike Homan February 27, 2024 MH Land men Developt File#25725-A 6820 W. Randolph Drive Page 1 of 14 Boise, Idaho 83709 Re: Geotechnical Feasibility Report Proposed Solara Estates Subdivision 4960 & 5060 S Locust Grove Road Meridian, Idaho Mike: SITE has visited the project site and researched available published information. Documents reviewed included Ada County Records, IDWR Records, Historical Aerial Photos (Google Earth), Geologic Mapping, Ada County Soil Profile, and previous geotechnical recommendation reports prepared by this firm for projects to the north and east of the subject property. Based upon our research and observations, the planned residential development is geotechnically feasible. Preliminary design recommendations are provided herein. The requested geotechnical and groundwater investigations are underway. This report will be amended when this work is completed. We appreciate this opportunity to be of service and look forward to working with you and your design and construction team during design and construction of this project. Respectfully submitted: SITE Consulting, LLC S51�NAL � Bob J. Arnold, PE �e�' cse�Y ® Member-Principal 45 02/27/25 ��?F J F J. A�C� Page 1 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 RESEARCH PROPERTY INFORMATIION & LOCATION The proposed subdivision includes two parcels at 4960 and 5060 South Locust Grove Road. The south parcel includes a single family home that is to be retained. The north parcel is farm or pastureland. The subject property is located on the east side of South Locust Grove Road, one lot south of East Amity Road. An LDS church is located to the north of the subject property. Rural farm properties of twenty and 4.5 acres are to the east and south. Residential subdivisions are located on the north side of Amity Road and to the east along both sides of Amity Road. These include former SITE projects, Grayson, Wells, Castlecreek, and Warrick Subdivisions. PROJECT INFORMATION The proposed Solara Estates Subdivision will include thirteen buildable lots for single family homes. The existing onsite home is to be retained on its own lot. Public (ACHD) streets are planned. All lots will be accessed from streets to be constructed within the subdivision. Solara subdivision will be accessed from South Locust Grove. ` ' I1f1!I'I South parcel from NW Corner. North parcel from SW Corner Page 2 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 ADA COUNTY ACCESSOR RECORDS County Assessor records indicate that the subject property includes a portion of a single tax parcel. The following information was found utilizing landprodata.com. Parcel# Owner Address Acres S1132223320 Curtis Bills 5060 S Locust Grove Road 5.0 S1132223210 Codi Bills 4960 S Locust Grove Road 5.0 HYDROLOGY AND GROUNDWATER RESEARCH Based on well logs located on the DWR website, it is anticipated the groundwater is greater than thirty feet deep and therefore will not be impacted by or impact the planned construction of this development. A well log for the adjacent LDS Church from the IDWR records is included in the Appendix. When test pits are excavated, monitoring wells will be installed in each test pit where the groundwater is reached. If encountered, the groundwater will be monitored through the end of the irrigation season with a separate groundwater report issued at that time. SURFACE SOILS The Ada County Soil Survey website generated the following information: Ada County, Idaho (ID001) Map Unit Map Unit Name Acres percent of Symbol in A0I A0I 122 Pipeline silt 4.7 41.9% loam, S to 12 percent slopes 141 Purdam silt 6.5 55.1% loam, 0 to 2 percent slopes Totals for Area of 11.2 100.0% Interest Surface soils are typically silt Ioams. This matched well with soils descriptions included on the included IDWR well log and will be confirmed when test pits are excavated. Page 13 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 GEOLOGIC MAPPING As per the, "Geologic Map of the Boise Valley and Surrounding Areas-1992" by Orthberg and Stanford, the subject property maps as follows. This agrees well with other reference sources and site observations. has SANDY ALLUVIUM OF SIDE-STREAM VALLEYS AND GULCHES — Medium to coarse sand interbedded with silty fine sand and At. Sediment mostly derived from weathered granite and reworked Tertiary sediments, Thick- ness variable. minor pedogenic clay and calcium carbonate. - GRAVEL OF AMITY' MIT TERRACE Sandy pebble and cobble gravel grading at depth to coarse pebbly sand. Seventh terrace above the floodplaiin. Gravel and sand is about 10 meters (33 feet) thick. Northwest-trending, gently sloping escarpments suggest fauitiIng of the gravel. Manned vAth loess 0.S-2 meters (2-7 feet) Ihick.. Geologic mapping and field observations indicate the majority of this property is at the toe of the Amity Terrace. The existing home is located atop the terrace. Prior SITE projects at the top of this terrace are referenced herein. PRIOR SITE GEOTECH REPORTS As indicated, SITE has provided geotechnical design services on numerous subdivision projects within the vicinity of the subject property. It is anticipated that onsite soils conditions will be similar to what was encountered at Grayson Subdivision. Grayson is located across Amity Road from the LDS Church. A typical test pit log from Grayson is included in the Appendix. Perc testing at Warrick Subdivision to the east is cited herein. Page 14 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 PRELIMINARY GEOTECHNICAL RECOMMENDATIONS The following comments & recommendations are based upon current development plans and researched information. It is noted that additional field and laboratory work is recommended herein. GENERAL CONSTRUCTION RECOMMENDATIONS • Based upon available data and field observations, grubbing depths of two to eight inches can be anticipated to remove most organic materials. Deeper excavation can be expected along ditches, along property boundaries, and where large trees and bushes are present. This is to be adjusted in the field at the time of construction. • Inspection at the time of construction is required to confirm proper removal of organic materials and that demolition of existing and former concrete structures (ditches) is properly completed. • While not anticipate, any encountered well or septic system is to be closed as per IDEA or IDWR requirements. • After proper clearing and grubbing, proof rolling of subgrade surfaces that will support structural fill or pavements is required. Contractor to provide equipment as needed and schedule proof rolling inspection by geotechnical engineer as clearing and grubbing is completed. • Soft, deflecting, or excessively wet soils will be rejected and require correction. Correction beyond over excavation and replacement with structural fill will require additional engineering based upon observed conditions at the time of construction. • Subgrade surfaces that will support structural fill or pavement sections and all structural fill is to be properly compacted. Compaction is to be based upon obtaining 95% of the maximum dry density as determined by ASTM D-698, "Standard Proctor". This requirement will increase to 98 percent in areas where the fill depth is greater than three feet deep. One test per lot per lift of fill is recommended. • Compaction testing of the subgrade can be waived by the geotechnical engineer based upon visual inspection and proof rolling. • Subgrade and structural fill can meet compaction requirements and still be unacceptable if unstable or excessively wet. Page 15 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 • Wet subgrade soils may become unstable or rut under rubber tire wheel loads. Contractor should avoid causing subgrade failure and use tracked and excavation equipment if indicated by high soil moisture and instability. • Native soils and onsite fill materials can be used as structural fill within building pads and street right of ways. Expansive fat clay, soils with debris or organics and large cemented hardpan pieces are not allowed as structural fill. • Structural fill must extend beyond the building envelope a distance equal to the depth of fill. • Structurally filled, deep pits such as basements, septic tanks, former ditches/canals, and silage pits are to be benched so that no vertical surface greater than three feet is present. Sloping banks at less than 1:1 is also acceptable. • Compaction of silt and clay soil on residential lots will seal crawlspaces and yard areas, greatly reducing percolation. All reasonable efforts to keep water out of crawlspaces are to be taken. These include water proofing of the foundation, proper compaction of foundation and utility trench backfill, and proper grading of the completed lot surface. Ripping yard areas around completed homes prior to fine grading will improve percolation of stormwater. PAVEMENT SECTION RECOMMENDATIONS • It is anticipated that an R-Value of R>20 will be obtained on the subgrade soils. Therefore, for planning and design the following pavement section is recommended, Low Volume T1 = 6 HMA 2.5" Base (3/4" ISPWC) 4.0" Subbase (ISPWC) 12.0" • All materials used to construct pavement sections are to meet the requirements of the local jurisdiction and ISPWC. Page 16 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 STORMWATER RECOMMENDATIONS • For preliminary design and cost estimating purposes, the perc rate from our prior report for Warrick Subdivision to the east is recommended. In this development a perc rate of P=2.0 in /hr. was measured during construction of the onsite facilities. This recommendation will be modified after onsite testing is completed. GENERAL RECOMMENDATIONS • Residential foundations can be designed based upon foundation bearing pressure of up to 1500 psf. Minimum footing widths and foundation embedment depth as provided in the local Building Code are to be enforced. FUTURE RESEARCH • SITE is under contract to provide additional field research to include sampling and logging test pits, laboratory testing of sampled soil, R-Value sampling for roadway design, and monitoring well installation for groundwater monitoring. It is anticipated that these results will generate modifications to the recommendations provided. Addendum reports will be issued as indicated. Appendix follows Page 17 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 APPENDIX Location Map Parcel information Preliminary Plat IDWR Well Log Test Pit Log Soil Log Legend/Abbreviations & Acrnyms Page 18 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 LOCATION MAP xF � { 'r } v - I e t. 6 . •1 � n u r H IT F L TFE — —1-T a � i T TH I ' �� 0 0 o j ❑ I 0 �* o ELL F— IL — r u I T T I T it Page 9 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 PARCEL INFORMATION Parcel Number:S113222321D .. Information s Parcel 51132223210 Primary Owner BILLS COI Second Owner BILLS CURTIS Property Address 4940 S LOCUST GROVE RD Total Value $8,000 Subdivision 3N 1E 32 Zoning RUT AcreslTax} 5 Acres Calculated} 4.901 Legal 1 PAR#3210 OF NW4N'.'U4 Lega12 SEC 323N1E 4 xy� IandproDATA k - Parcel Number: S1132223321} 0 Information Parcel 31132223320 n , Primary Owner BILLS CURTIS �• Second Owner y Property Address 5011 S LOCUST GROVE RO Total Value S1,17T,200 Subdivision 3N1E32 xf Zoning RUT Acres jax} 5 Acres{Calculated} 4.912 Legall N2SW4NW4NW4 Legal SEC323NIE andpro Page 10 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 PRELIMINARY PLAT 072 Now Lu s s M ,a s ffII z i ,� °I c WN s t ° � ❑s ® 0 0 . W, a� ❑ [4-1 r � '.. ... as L I Page 11 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 IDWR Well Log — Adjacent Property LDS Church Across Amity Road STATE 4F IDAHO USE TYPEWRITER OR g' DE Pik R TM IEPJT O F WATER RESCURC'E5 R+%LLPOrNT PEN WELL DRILLER'S REPORT f Swet law 1MyaKae OhMthi.1M rd Fx Ilan Whdl trio 6614410r,104wwtn411 Or YY.Ur Fkawrarrrls y r wldlin 30 MWO 04W Thh—pletion or&-W.mrn[of h.wal. 1. VYELLawNER f. 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E,flr� USE AOOFTIONAL SHEETS rF WECESIRARY - FORYVAFO THE 4WHPTE COPY TO THE DEPARTMENT Page 1 12 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 TEST PIT LOG Test Pit: TP-2 File #: 22085-A Client: Schultz Development Date Excavated: 01/27/22 Project: Grayson Sub Excavated By: SC Excavation Location: See Aerial Photo Logged By: J. Meusch-SITE DEPTH SOILS DESCRIPTION (feet) 3/4" 1/2" 3/8" #4 # 10 #40 #100 #200 %M LL I PI 0.0-1.0 Brown, Moist, Firm, Sand & Silt 1.0-3.0 Brown/Red, Moist, Firm, Sticky, Sandy, Silt (ML) 2.0 1 1 100 1 99 1 97 92 188.6 1 24.4 37 I 14 3.0-5.0 Brown/Tan, Moist, Firm, Silty, Sand (SM) 4.0 1 100 1 98 1 93 1 73 1 43 39 29.3 1 19.3 1 NP I N P 5.0-6.0 Brown/Tan, Moist, Firm, Cemented, silt Hardpan. 6.0-8.0 Brown/Red, Moist, Firm, Silty, Sand & Gravel 7.0 100 1 98 1 71 1 55 1 32 1 28 23.8 1 18.3 1 NP NP 8.0-9.0 Brown/Red, Moist, Firm, Silty, Sand and Gravel 8.5 91 1 81 1 77 1 70 1 61 1 35 1 17 15.1 1 8.6 1 NP NP 9.0-12.0 Brown/Tan, Moist, Firm, Sand, Silt, Cobble Bottom of Excavation @ 12.0' 12.0 No Ground Water Encountered Monitoring Well in Place Page 1 13 ZSITE Post Office Box 190537 - Boise, Idaho 83719 SULTING, LLC Info@siteconsultingllc.com - 208-440-6276 SOIL LOG LEGEND UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM STANDARD TEST METHOD D 2487 FOR CLASSIFICATION OF SOIL FOR ENGINEERING PURPOSES MAJOR DIVISIONS �j TYPICAL DESCRIPTIONS GRAVEL& <5%-200 1=1 Well-graded gravel, ravel-sand mixture, little or no fines. GRAVELLY GP Poorl graded gravel,gravel sand mixture, little or no fines COARSE SOILS 5-12%-200 FG—M-1 S Ity gravel,gravel-sand-silt mixtures ° GRAINED <50/o-4 >12%-200 GC FC_Iayey gravel,gravel-sand-clay mixtures SOILS<50%-200 SAND& <5%-200 SW Well- raded sand,gravelly sand, little or no fines. SANDY 1=1 Poorly graded sand,gravelly sand, little or no fines SOILS SM Silt sand,sand-silt mixtures >50%-4 >12%-200 SC Clayey sand,sand-clay mixtures F91 Inorganic silt and very fine sand, rock flour,silty or clayey SILTS AND INORGA fine sand or clayey silt with slight plasticity NIC CLAYS INP an clay-low to medium plasticity,gravelly clay,sandy clay, FINE LL<50% ty clay GRAINED SOILS ORGANIC OL Organic silt and organic silty clay of low lasticit >50%-200 SILTS AND INORGANIC MH Elastic silt,micaceous or diatomaceous fine sand or silty soil. CLAYS IF—C—H-11 Fat clay-high plasticity ORGAN F—OH-11 Organic clay-med.or high plasticity: organic silt HIGHLY ORGANIC SOILS PT Peat, humus,swamp soil with high organic content ABBREVIATIONS & ACRONYMS AASHTO American Association of State Highway & Transportation Officials ACHD Ada County Highway District ASTM American Society for Testing and Materials BH I Bore Hole IBC International Building Code ISPWC Idaho Standard for Public Works Construction ITD I Idaho Transportation Department NP Non-Plastic PCC I Portland Cement Concrete PCF I Pounds per Cubic Foot TP I Test Pit USCS Unified Soil Classification System Nothing follows. Page 1 14