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Home My WebLink AboutCC - Geotech Report SITE CONSULTING, LLC Brad Miller January 28, 2016 Ronald Van Auker Inc. Page 1 of 9 1802 Lanark Street File# 16016A Meridian, Idaho 83642 Re: Geotechnical Recommendations Swindell Property 1495 South Locust Grove Meridian, Idaho Brad: As per your authorization and as requested by Matt Munger with WH Pacific, SITE Consulting, LLC logged and sampled two test pits on the referenced property. WH Pacific requested that soils profiles be generated, the depth to groundwater be determined and recommendations for storm water disposal be provided. It was reported that subsurface infiltration trenches are preferred. An aerial photo and the address of 1495 South Locust Grove were obtained from the Ada County Assessor's website. Two parcel numbers S1118449550 & S1 119449350 were also listed for the subject property. The test pits were excavated as close to the planned storm water facilities as possible. Approximate locations are shown on the included aerial photo. These locations were provided by WH Pacific. During excavation, soil samples were gathered, and the included Test Pit Logs were generated. Soils were submitted to our in-house soil laboratory for analysis. Laboratory test results and all soil classifications and descriptions are reported on the attached Test Pit Logs. Our recommendations are based upon the proposed design, the observed conditions and test results as documented herein. tw 208-440-6276 * info@siteconsultingllc.com * Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC GENERAL OBSERVATIONS It is noted that the surface elevation of the subject property is very irregular with numerous low areas and many large piles of fill material. The Topo Map provided by WH Pacific indicates there is six feet of elevation change between our two test pits with the west pit being substantially lower. Both test pits were excavated to the maximum depth possible with the selected equipment. In both pits, sloughing sands and gravels prevented deeper excavation. As indicated, the surface of the site is very irregular. The area between our two test pits is covered with end dumped stockpiles of soils. According to historical aerial photos available on Google Earth, these piles have been onsite for over ten years. This source indicates that earthwork activities have been on going on this property since 2002. SUBSURFACE CONDITION At both test pit locations, the surface appears to have been graded and filled. This may have occurred when the prior utility work was done along the west property boundary. From the existing ground surface to gravel contact varied from 6.5 feet (west) to 9.0 feet (east). Above the native pitrun was layers of silt and sand and blends of silt and sand with gravel. No dense clay, hardpan or cemented silt layer was observed in either test pit. All sampled soils were determined to be non-plastic by laboratory testing. Soils varied from 3-inch minus to #4 minus with moisture content ranging from 6.5 to 12.5 %. Once contacted the native pitrun type sand and gravels graded very quickly to free draining, free flowing, sands, and gravel that are very dry (3.5% moisture). At the bottom of our test pits these materials were dry and flowing freely into the excavation. Materials could not be removed fast enough to excavate to deeper depths. N Gl dp f0 a 208-440-6276 * info@siteconsultingllc.com * Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC GROUNDWATER OBSERVATIONS Since groundwater was not contacted in our 13 feet deep test pits, additional research was undertaken. WH Pacific indicated that a well was present in a small pump house, just east of our east Test Pit. The client was contacted, and permission received to access this well by removing the top of the well casing. On January 8, 2016, the static water level in this well was 38 feet below the pump house concrete floor. A topo map provided by WH Pacific and included in the Appendix indicates the ground surface is 2642 at the pump house, 2638 at our east test pit and 2632 at our west test pit. Therefore, groundwater is greater than 14 feet below the bottom of our west (deepest) test pit. Based upon our experience in the area, this greatly exceeds any season change in the groundwater. STORMWATER RECOMMENDATION The free draining pitrun type sand and gravel encountered in both test pit locations at ten feet below the surface will accept stormwater and therefore infiltration trenches are acceptable. Based upon observed conditions and experience on other projects in the general vicinity the percolation rate for these soils will greatly exceed the P= 8 in / hr that is currently the upper limit for storm water design. Confirmation of this assumed percolation rate at the time of construction is recommended and will likely be required. GENERAL COMMENTS Concern must be expressed for construction of roadways on this property. It is recommended that all undocumented fill materials within planned right of ways be stripped and then, if acceptable, replaced as structural fill. Unacceptable material will include soils with organic matter, large clod or pieces of hardpan, concrete, pavement and other debris, excessively wet soils, low density soils, and expansive clay. ISPWC requirements for fill quality, placement methods and inspection are recommended. M Gl dp f0 a 208-440-6276 * info@siteconsultingllc.com * Post Office Box 190537 * Boise, Idaho 83719 CONSITE SULTING, LLC 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, LLC Bob J. Arnold, PE %pNAL STE.9 �* a OF Appendix Follow M a 208-440-6276 * info@siteconsultingllc.com * Post Office Box 190537 * Boise,Idaho 83719 CONSITE SULTING, LLC APPENDIX Test Pit Locations Topo Map Test Pit Logs (2) Ln tw m a 208-440-6276 * info@siteconsultingllc.com * Post Office Box 190537 * Boise,Idaho 83719 SITE CONSULTING, LLC Test Pit Locations gill Ea q - J ■ • ■o ■ ■ ■ ■,4l - ..AN. . C O • G Aerial Photo from Ada County Assessor Website v an m a 208-440-6276 * info@siteconsultingllc.corn * Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC TOPO MAP IB 17 ol lYTlA!lI 1L !i CREEK uo I �N[AWO I r RUT AM 144 t'3N g iSSUNF.�50'NRGPA L yam' INST. 92fi8L94 f _. 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T-.. n Ol a0 a 208-440-6276 * info@siteconsultingllc.com * Post Office Box 190537 * Boise,Idaho 83719 SITE CONSULTING, LLC TEST PIT LOG Test pit#: TP-East File: 16016A Client: Van Auker Date Excavated: 12/6/15 Project: Swindell Property Digger: Culver/ Backhoe Location: East Infiltration Trench Logged By: K.Arnold DEPTH SOILS DESCRIPTION Sample 3/8 #4 #10 #40 200 M PI LL Type 0.0-1.0 FILL-Topsoil -Brown, Moist to Wet, Silt and Sand 1.0-5.5 Brown, Moist, Sandy SILT(ML) Bag 100 94 88 68 54.0 10.5 NP NP with Gravel 2.5 Scalped 5.5-6.5 Brown, Moist, Firm, SILT(ML) Bag 100 92 74 69.9 10.0 NP NP 6.0 6.5-9.0 Brown, Moist, Sandy, SILT(ML) Bag 98 93 87 82 62.2 11.5 NP NP 8.0 9.0 Gravel Contact 9.0-12.5 Tan &White, Moist, Coarse, Bag 65 55 46 18 5.5 2.9 NP NP PITRUN type Sand and Gravel 12.0 Scalped Free Draining at 10 feet 12.5 Bottom of Hole - Sloughing Soils Prevented Deeper Exploration NO GROUNDWATER ENCOUNTERED 00 v an m a 208-440-6276 * info@siteconsultingllc.corn * Post Office Box 190537 * Boise, Idaho 83719 SITE CONSULTING, LLC TEST PIT LOG Test pit#: TP-West File: 16016A Client: Van Auker Date Excavated: 12/6/15 Project: Swindell Property Digger: Culver/ Backhoe Location: West Infiltration Trench Logged By: K.Arnold DEPTH SOILS DESCRIPTION Sample 3/8 #4 #10 #40 200 M PI LL Type 0.0-0.8 FILL-Topsoil, Brown, Moist, Silt and Sand 0.8-3.5 Tan to Light Brown, Moist, Silty Bag 97 90 83 61 37.4 7.5 NP NP SAND with Gravel 2.5 3.5-5.5 Brown, Moist, Firm, Silty, SAND Bag 100 98 79 44.4 11.2 NP NP 5.0 5.5-6.5 Brown, Moist, SAND with silt Bag 76 70 65 45 28.9 6.8 NP NP And gravel 6.0 6.5 Gravel Contact 6.5-13.0 Tan &White, Moist, Fine, Bag 61 51 42 15 8.4 3.5 NP NP PITRUN type Sand and Gravel 12.0 Scalped FREE DRAINING AT 9.0 FEET 13.5 Bottom of Hole - Sloughing Soils Prevented Deeper Exploration NO GROUNDWATER ENCOUNTERED Nothing Follows tw 208-440-6276 * info@siteconsultingllc.corn * Post Office Box 190537 * Boise, Idaho 83719