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Home My WebLink AboutGeotechnical RecommendationsGeotechnical Recommendations Pine Bridge Development T3N, R1 E, Section 8 Meridian, Ada County, Idaho Prepared for Mr. Dan Torfin Dennis Baker & Associates 250 South Beechwood, Suite #100 Boise, Idaho 83709 Prepared by Bob J. Arnold PE 8717 Craydon Drive Boise, Idaho 83704 208-440-6276 File #4109A Date November 12, 2004 Bob J. Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 biarnoldveOmsn.com Mr. Dan Torfin Dennis Baker & Associates 250 South Beechwood Street, Suite #100 Boise, Idaho 83709 Dear Dan: November 11, 2004 Page 1 of 11 41109A001.doc Re: Preliminary Geotechnical Report Pine Bridge Development T3N, R1 E, Section 8 Meridian, Ada County, Idaho As authorized, on November 10, 2004, this engineer visited the referenced property and observed the excavation of six test pits. The test pits were excavated to 7.0 to 12.0 feet below the existing ground surface. In each pit, further excavation was not possible due to sloughing soils below the groundwater elevation. Soils encountered ranged from clay foams at the surface to a pitrun type sand and gravel mixture at depth. Cemented silt layers and a thin, weak hardpan layer were typically encountered in the test pits. These layers varied greatly in thickness. In all locations soils conditions were acceptable for commercial and or multi -family construction and installation of related civil improvements. Additional research by this engineer included reviewing previously authored reports for Paragon Pacific (south of project), Yellow Freight (east of project), and Oak Harbor Freight (west of the project). The Ada County Soils Profile, Ada County Assessor's website, and the Idaho Department of Water Resources website were also reviewed for pertinent information. The test pits confirm the soils described within the Soils Profile. Well log information indicates groundwater is between 7.0 and 20.0 feet deep within section eight. This also agrees with conditions observed in the field where water was encountered between 7.0 and 11.0 feet below the existing surface. Lab testing of the soils sampled during the test pit excavation is underway. Results will be reported, and this report modified as needed, when the laboratory testing is completed. Bob J. Arnold, PE 8717 Craydon Drive Boise, Idaho 83704 Bob J . Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 biarnoldpea-msn.com November 11, 2004 Page 2 of 11 41109A001.doc It was reported that multi -family residences and commercial properties are planned for this development. Street sections will consist of paved roads to meet ACHD requirements for pavement section and stormwater disposal. Therefore, pavement sections and storm water recommendations are included herein. Preliminary foundation design recommendations as well as general earthwork recommendations are also provided. Based upon the reported conditions, the following preliminary recommendations for construction are provided. COMMERICIAL & MULTI RESIDENTAL FOUNDATIONS • Based upon observed conditions, bearing pressures of up to 2000 psf are acceptable for foundation design. This is provided foundations are founded upon native silts or cemented silts located below the clay loam surface soil. — • All foundations are to be founded at least 30 inches below grade for frost protection. — • Higher bearing pressures are available for foundations bearing on the deeper pitrun type sand and gravel mixture or upon structural fill materials. STRUCTUAL FILLS — • Native soil or imported granular material can be used for fill provided the material is moisture conditioned for proper compaction. One foot or thinner lifts are — recommended. • For shallow fills (less than 3.0 feet), compaction is to meet 95% of the maximum dry density as determined by ASTM D-698, Standard Proctor. For deep fills (greater than 3.0 feet), compaction is to meet 98% of this standard. • Compaction testing by an independent testing firm is required to confirm compaction results. Bob J. Arnold, PE 8717 Craydon Drive Boise, Idaho 83704 Bob J. Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 biarnoldpeomsn.com November 11, 2004 Page 3 of 11 PAVEMENT SECTION 41109A001.doc • An R-value sample was gathered and submitted to a soils laboratory for testing. Based upon the presence of plastic clay soils in the sample it is not anticipated that a reduction in ACHD's maximum pavement section design will be recommended. • Pending completion of the lab analysis, the following street pavement section is recommended. Material Residential Arterials • ACP Pavement 2.5" 3.0" • 3/4" Road Base 4.0" 4.0" • Pitrun Sub Base 14.0" 16.0" • If design elevations are such that the cemented silts or hardpan soils are encountered during excavation to the pavement subgrade, the pitrun sub base layer can be reduced to not less than 8.0". • It is strongly recommended that R-value samples be gathered and analyzed for each phase of the project, thereby reducing the pavement section design where possible. STORM WATER DISPOSAL • Standard infiltration trenches or infiltration/evaporation ponds are feasible for disposal of storm water. There are low plasticity clays and cemented silts present on the property but these soils are typically shallow and therefore easily penetrated during trench or pond construction. • In areas were storm water is concentrated conventional infiltration trenches are recommended. For design purposes a percolation rate of P=8 inches per hour is recommended based upon the observed field conditions. Bob — Arnold, PE 8717 Craydon Drive Boise, Idaho 83704 Bob J. Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 * bjarnoldpe(&-msn.com November 11, 2004 Page 4 of 11 41109A001.doc I appreciate this opportunity to be of service. Please contact me should you require additional information or services. Resp ►ly mitted.- I oa�� Bob J. Arnold, PE Attachment: Preliminary Test Pit Logs Bob J. Arnold, PE 8717 Craydon Drive Boise, Idaho 83704 T Bob J . Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 biarnoldpe msn.com November 11, 2004 �.. Page 5 of 11 Aerial Photo 41109A001.doc L-71 .. Bob J. Arnold, PE 8717 Craydon Drive Boise, Idaho 83704 Bob J. Arnold PE Civil Engineering 7 Geotechnical Engineering Materials Testing & Inspection Services — 208-440-6276 * Fax 208-323-7866 biarnoldpeAmsn.com November 11, 2004 Page 6 of 11 PRELIMINARY TEST PIT LOGS 41109A001.doc Boring #: TEST PIT 1 File #: 41109A001 Client: Dennis Baker Date Excavated: 11/10/04 Project: Pine Bridge Drilled By: Masco Address: Section 8 Logged By: Bob Arnold ept' Feet) Field Descriy�tion Y sample sample Depth M N LL PI Sieve Anal sis y Type feet '/a 3/8" #4 #10 #40 #200 0.0 Dark Brown, wet, soft organic - sandy lean clay - root zone to 8". 1.0 1.0 Tan to white, Moist, Cemented Bag - Silts 5.0 5.0 Weak Hardpan Layer 6.0 6.0 Tan to white, Moist, Cemented - Silts 7.0 7.0 Tan, Wet Loose, Sand Bag 9.0 9.0 Pitrun type Sand and Gravel GROUNDWATER 11.0' - Mixture — Light Brown to Tan to 12.5 White, Wet to Saturated, Very Sandy to 8" maximum. Bob J. Arnold, PE 8717 Craydon Drive _ Boise, Idaho 83704 Bob J. Arnold PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 WarnoldpeAmsn.com November 11, 2004 Page 7 of 11 41109A001.doc Boring #: TEST PIT 2 File #: 41109AO01 Client: Dennis Baker Project: Pine Bridge Address: Section 8 Date Excavated: 11/10/04 Drilled By: Masco Logged By: Bob Arnold Depth (Feet) Fiel1d Descri tlon P sample Sample MIN LL PI Sieve Analysis Type Depth feet 3/4 3/8" #4 #10 #40 #200 0.0 Dark Brown, wet, soft organic - sandy lean clay - root zone to 8". 15 1.5 Tan to white, Moist, Cemented Bag - Silts 4.0 4.0 Weak Hardpan Layer 5.3 5.3 Tan to white, Moist, Cemented - Silts 6.0 6.0 Light Brown, Wet, Blocky Clayey Bag - Silt with Sand 8.5 8.5 Tan, Wet Loose, Sand 10.5 10.5 - Pitrun type Sand and Gravel Mixture — Light Brown to Tan to GROUNDWATER (a) 10.5' 12.5 White, Wet to Saturated, Very Sandy to 8" maximum. Bob J. Arnold, Pc 8717 Craydon Drive Bose, Idaho 83704 Bob J. Arnold PE Civil Engineering 7 Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 * WarnoldpeRmsn.com November 11, 2004 Page 8 of 11 41109A001.doc Boring #: TEST PIT 3 Client: Dennis Baker Project: Pine Bridge Address: cPrrinn R File #: Date Excavated: Drilled By: Logged By: 41109A001 11/10/04 Masco Bob Arnold Depth (Feet) Field Descri tion P Sample Sample MIN LL PI Sieve Analysis Type Depth feet 3/4 3/8" #4 #10 #40 #200 0.0 Dark Brown, wet, soft organic - sandy lean clay - root zone to 8". 1.0 1.0 Tan to white, Moist, Cemented Bag - Silts 2.0 2.0 Weak Hardpan Layer 4.0 4.0 Pitrun type Sand and Gravel GROUNDWATER (a_ 9.0' Mixture — Light Brown to Tan to 10.0 White, Wet to Saturated, Very Sandy to 8" maximum. Boring #: TEST PIT 4 File #: Client: Dennis Baker Date Excavated: Project: Pine Bridge Drilled By: Address: Section 8 Logged By: 41109AO01 11/10/04 Masco Bob Arnold Depth (Feet) Field Description P Sample Type sample Depth M N LL PI Sieve Analysis 0.0 Light Brown to tan, Moist, soft feet M/ 318" #4 #10 #40 #200 - sandy lean clay - root zone to 6". 4.0 Sandier with increased depth. 4.0 Tan to Red, Wet Loose SAND Bag 6.0 6.0 Pitrun type Sand and Gravel Mixture — Light Brown to Tan to GROUNDWATER a) 7.0' 8.5 White, Wet to Saturated, Very IS to 6" maximum. Bob J. Arnold, PE 8717 Craydon Drive Boise, Idaho 83704 Bob J. Arnold PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 * biarnoldpe(a)msn.com November 11, 2004 Page 9 of 11 41109A001.doc Boring #: Client: Project: Address: TEST PIT 5 Dennis Baker Pine Bridge Section 8 File #: Date Excavated: Drilled By: Logged By: 41109A00I 11/10/04 Masco Bob Arnold tion Sample Sample M N LL PI Sieve Analysis Type feet M 3/8" 44 #10 #40 #200 game ie to 8". tented layers —GROUNDWATER Tel @ 9.0' > Tan to Cemented [mum. Boring #: TEST PIT 6 File #: Client: Dennis Baker Date Excavated: Project: Pine Bridge Drilled By: Address: Section 8 Logged By: 41109A001 11/10/04 Masco Bob Arnold Field Description P Sample Type Sample Depth M N LL PI Sieve Analysis feet '/a 3/8" #4 #10 #40 #200 Light Brown, wet, soft organicsandy lean clay - root zone to 8". N Tan to white, Moist, Cemented Silts Weak hardpan layers 6.5 6.5 Pitrun type Sand and Gravel GROUNDWATER g 11.0' - 12.0 Mixture — Light Brown to Tan to White, Wet to Saturated, Cemented at top of layer, to 12"' maximum. Bob J. Arnold, or �E 8717 Craydon Drive Boise, Idaho 83704 Bob J. Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 * Fax 208-323-7866 biarnoldpe@_msn.com November 11, 2004 Page 10 of 11 Idaho Department of Water Resources 41109A001.doc Listing of Driller Reports T. 3 N., R. 1 E. 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IDOM j..::...:....:.........»...,.................. 10 10215/22/1987 :785477 :YELLOW FREIGHT _.w:_ ::_..._.: :_: _.: ..j _::»::# .::_:_..:.. :....w_k. _..._ SYSTEM INC JRR2020 5: 79J9/17/1990 '724040 : STUTZMAN, ^PAUL :. .......... :.................:.:.:::.:::..:..:::.:::.::................:.::::. .. ............... :.....» 9999 3 30 ..._.:._ .»:....... _.. 147�12/8/1977 M':783430 HOWARD&PACIFIC ..:....:.:.......:.::....:...........:....:..:.......,•:...:...........:,....»:...:» ».».::...:::............:....... ..::...:...: :NORTHWESTERN :ELECTRIC - ."DOM 3131 LANARK 50 91 89 6/29/1994 1!727831 :VAN AAKER, RON 14R:EAGLE RD & »» LANARK ST 60f 10 863/29/1993 :72684R Bob J. Arnold, or ` 8717 Craydon Drive Boise, Idaho 83704 Bob J. Arnold, PE Civil Engineering Geotechnical Engineering Materials Testing & Inspection Services 208-440-6276 Fax 208-323-7866 jLarnoldpeAmsn.com November 11, 2004 Page 11 of 11 41109A001.doc Bob J. Arnold, PE 8717 Craydon Drive Boise, Idaho 83704