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HomeMy WebLinkAboutREPORT - 06-00184 - Madison Memorial Hospital - AdditionPrepared by J. Paul Bastian, P.E. Teri L. Bowman, E.T. STRATA, Inc. 4460 Kings Way #3 Chubbuck, Idaho 83202 P. 208.237.3400 F. 208.237-3449 REPORT Geotechnical Engineering Evaluation Madison memorial Hospital Additions Rexburg, Idaho 0600184 Madison Memorial Hospital Addition Prepared for Adams Management Service Corporation C/O Madison Memorial Hospital 10475 Park Meadows Drive Suite 600 Lone Tree, Colorado 80124 August 24, 2005 j rtfxc;rr f�. Fr<�x� /:ir car �ir«l August 24, 2005 AMSCOR-PO5040A Mr. Steve Catts Adams Management Services Corporation 10475 Park Meadows Drive Suite 600 Lone Tree, CO 80124 RE: Revised Report Geotechnical Engineering Evaluation Madison Memorial Hospital Additions Rexburg, Idaho Dear Mr. Catts: STRATA, Inc. has performed the authorized geotechnical engineering evaluation for the proposed additions to the Madison Memorial Hospital in Rexburg, Idaho. The purpose of our geotechnical engineering evaluation was to explore the subsurface soil and geologic conditions within the proposed development area and to provide geotechnical -engineering recommendations to assist project planning, design and construction. The work was performed in general accordance with our proposal dated March 30, 2005. This report summarizes the results of our field evaluation, laboratory testing, engineering opinions, and geotechnical recommendations. The soil and groundwater conditions at the site are presented in the following report. Specific geotechnical opinions and recommendations for foundation design, earthwork construction, pavement, lateral earth pressure and storm water discharge are included. The geotechnical recommendations presented must be read and implemented in their entirety. Portions or individual portions of the report cannot be relied upon without the supporting text of relevant sections. The success of the proposed construction will depend in part, on following the report recommendations and good construction practice. We recommend that STRATA be retained to provide geotechnical testing and consultation services during construction to verify our report recommendations are followed. It has been our experience that maintaining continuity with a single geotechnical consultant reduces errors and contributes to overall project success and economy. IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com 4460 Kings Way #3, Chubbuck, Idaho 83202 P.208.237.3400 F.208.237.3449 We appreciate the opportunity to work with you on this project. Please do not hesitate to contact us if you have any questions or comments. Sincerely, STRATA, Inc. i Teri Bowman, E.T Project Assistant J. Paul Bastian, PE Project Engineer JBP/tlb IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com REVISED REPORT Geotechnical Engineering Evaluation Madison Memorial Hospital Additions Rexburg, Idaho PREPARED FOR: Adams Management Services Corporation 10475 Park Meadows Drive Suite 600 Lone Tree, CO 80124 PREPARED BY: Strata, Inc. 4460 Kings Way #3 Chubbuck, Idaho 83202 (208) 237-3400 August 24, 2005 TABLE OF CONTENTS IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com 4460 Kings Way #3, Chubbuck, Idaho 83202 P.208.237.3400 F.208.237.3449 PAGE INTRODUCTION.................................................................................................................1 PROPOSED CONSTRUCTION...........................................................................................2 SUBSURFACE EVALUATION PROCEDURES...................................................................2 SUBSURFACECONDITIONS.............................................................................................2 LABORATORYTESTING....................................................................................................3 GENERAL OPINIONS AND RECOMMENDATIONS...........................................................3 SITEPREPARTATION..........................................................................................................4 EXCAVATION CHARACTERISTICS.........................................................................................5 TEMPORARY AND PERMANENT SLOPES...............................................................................5 STRUCTURALFILL..............................................................................................................5 LATERAL EARTH PRESSURE................................................................................................7 FLEXIBLE AND RIGID PAVEMENT DESIGN.............................................................................. 9 CONCRETE SLAB -ON -GRADE FLOORS...............................................................................10 PERIMETER WALL DRAINAGE............................................................................................11 SEISMICITY...................................................................................................................... 12 SITEGEOLOGY................................................................................................................13 FOUNDATIONDESIGN.......................................................................................................13 WET WEATHER CONSTRUCTION........................................................................................15 SURFACE AND SUBSURFACE DRAINAGE.............................................................................16 VOID DETECTION AND REMEDIATION ALTERNATIVES...........................................................16 ADDITIONAL SERVICES RECOMMENDED.....................................................................17 REVIEW OF PLANS AND SPECIFICATIONS...........................................................................17 CONSTRUCTION OBSERVATION AND TESTING.....................................................................17 EVALUATION LMITIATIONS.............................................................................................18 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com 4460 Kings Way #3, Chubbuck, Idaho 83202 P.208.237.3400 F.208.237.3449 REVISED REPORT Geotechnical Engineering Evaluation Addition to Madison Memorial Hospital Rexburg, Idaho INTRODUCTION STRATA, Inc. has preformed the authorized geotechnical engineering evaluation for the proposed addition to the Madison Memorial Hospital in Rexburg, Idaho. A vicinity map is presented as Plate 1. The purpose of the geotechnical engineering evaluation was to assess the general soil and geologic conditions within the proposed development area and to provide geotechnical and soil related construction recommendations with respect to the proposed development. Our recommendations are based on our field observations and laboratory test results. To provide this evaluation of the site we conducted the following scope of work: I. Notified utility mark out prior to the excavation of the test pits. 2. Reviewed site map and topography maps provided by 3. Observed the advancement of 7 borings to depths of up to 16 feet and were terminated in basalt bedrock. The soil encountered in the borings was described and classified referencing ASTM D 2487 and D 2488 Unified Soil Classification System (USCS) and the soil profiles were logged. The borings were backfilled at the time of excavation. Backfill was not compacted or landscaped. 4. Performed Standard Penetration testing to verify the condition of the soil types encountered in the borings. 5. The field and laboratory data were analyzed to provide the project team with geotechnical opinions and recommendations as outlined in our proposal. 6. Prepared and provided five copies of our final summary report of findings, opinion, and geotechnical recommendations to assist design planning and construction. IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com 4460 Kings Way #3, Chubbuck, Idaho 83202 P.208.237.3400 F.208.237.3449 Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A PROPOSED CONSTRUCTION Page 2 The project site is located near the end of East main in Rexburg, Idaho. We understand proposed additions will consist of three single story structures, one two- story structure and a new below grade truck loading dock. The structures will be masonry or wood frame buildings with concrete slab on grade floors. Conventional spread footings for perimeter wall and interior column foundations are proposed. We understand that footing loads for perimeter walls will be approximately 2000 pounds per linear foot and interior column loads will be approximately 450 kips. Storm water will be discharged on site. Parking and access roads for cars and service vehicles is planned near the new additions. The parking areas will be designed predominantly for auto parking and the access roads will support delivery and service vehicle truck traffic. SUBSURFACE EVALUATION PROCEDURES Seven borings were drilled on April 18, 2005 within the proposed project area as identified on the Site Map presented on Plates 2 Site Map. The borings were drilled with a truck mounted CME 75 auger & core drill rig. The soil and rock encountered in the borings was visually classified and described referencing ASTM D 2487 and D 2488, Unified Soil Classification System (USCS). The USCS is provided on Plate 3 and should be referenced to interpret the terms used throughout this report. The subsurface profiles were logged and the exploratory logs and laboratory test data are presented in the Appendix to this report. Select soil samples were obtained for laboratory testing. The borings were loosely backfilled at the conclusion of the field evaluation. We recommend the ground surface in the boring locations be monitored and adjusted as necessary to maintain a level surface. SUBSURFACE CONDITIONS Subsurface soil conditions in test pits typically consisted of 3 to 11 feet of brown fine sandy silt "ML" and/or gravel fill underlain by basalt bedrock. The sandy silt was relatively uniform across the site and the gravel was intermittent. The silt and gravel were underlain by hard to very hard basalt bedrock. Areas of cinders or voids were not i4 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR•PO5040A Page 3 encountered in the borings. Groundwater was not encountered in the locations explored to a depth of up to 16 feet. We do not anticipate groundwater will be encountered within the planned excavation depths, as we understand the proposed construction. LABORATORY TESTING Select soil samples were tested to assess the unconfined compressive strength of the basalt bedrock underlying the site. Laboratory testing was performed referencing ASTM test procedures. The laboratory test results are presented on the boring logs, which are presented in the Appendix to this report. GENERAL OPINIONS AND RECOMMENDATIONS Our geotechnical opinions and recommendations are presented in the following sections to assist project planning, design, and construction of the proposed additions. Our recommendations are based on the results of our field evaluation, laboratory testing, our experience with similar projects in the area, and our understanding of the proposed construction. These opinions and recommendation reflect our conversations with the project team and are based, in part on preliminary information provided to us by your company and the structural engineer. If design plans change, such as loading conditions, foundation sizes or configuration, STRATA should be notified to review our report recommendations and make necessary modifications. Soil conditions in the test pits were observed to be relatively uniform. However, subsurface conditions may vary across the site. These changes in conditions may not be apparent until construction. If the subsurface conditions change from those observed in the test pit locations, the construction schedule, plans, and costs may change. 04 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Site Preparation Page At the time of our field evaluation the site was developed and landscaped. Removal of existing pavement and topsoil will be required. Soil containing roots and vegetation is not suitable for support of the planned pavement sections or concrete floors for the additions and must be removed from the site at the commencement of construction. The native sand/silt soil is prone to collapse and will not support foundation loads without experiencing significant consolidation that would manifest in settlement of the structure. Therefore, all surficial sand/silt soil in its present condition is unsuitable for support of the planned foundation loads and should be removed from the locations to expose the underlying basalt rock. The native soil may be replaced in 6 to 8 inch thick compacted lifts in the footing locations to achieve a subgrade suitable for support of 2000 pounds per square foot. The recompacted silt is not suitable for support of bearing pressures greater than 2000 psf. The native soil is suitable for support of the proposed concrete floors and pavement sections in parking and access road areas provided it is properly moisture conditioned and compacted as outlined in the following sections of this report. After design subgrade elevation has been achieved in the floor, parking and access road locations, we recommend the exposed native soil surface be proof rolled with a minimum of five passes of a large vibratory roller with a drum weight greater than 5 tons. If pumping or unstable soil is observed during the proof rolling operation, the unstable soil should be removed and replaced with structural fill. We recommend final subgrade preparation for sidewalks and building areas include compaction of the upper 8 inches of exposed sub -grade soil to at least 95 percent of the maximum dry density as determined by ASTM D-698 (Standard Proctor). Subgrade soil should be properly moisture conditioned prior to attempting compaction efforts. Optimum moisture content for compaction will vary with soil types. Therefore, the contractor should anticipate a moisture conditioning effort to achieve q IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A acceptable moisture levels. STRATA should review the compaction process priorgto placing structural fill. Once the native soil subgrade has been proof rolled as described above, structural fill placement or foundation or slab preparation may commence. Excavation Characteristics Native soil may be excavated using conventional soil excavation techniques. The upper fine sandy silt soil can be excavated near vertical for excavations up to 4 feet in depth. Trench excavations deeper than 4 feet should allow provisions for excavations to be sloped back at 1.5:1 (horizontal to vertical). Alternatively, deeper trenches and excavations should be shored or braced in accordance with OSHA regulations and local codes. The basalt rock encountered on the site is moderately to closely fractured. While the basalt can be excavated or blasted to achieve vertical slopes the risk of falling rock is present and retaining structures or wire mesh slope or excavation face covering will be required on rock faces over 6 feet in height. Temporary and Permanent Slopes The on-site sandy silt soil is easily eroded by water and prone to sloughing and slope or trench instability. Excavations for utility trenches in the silt to depths of 4 feet can be made with a vertical slope. Trench excavations deeper than 4 feet should be sloped or braced in accordance with OSHA regulations. Temporary slopes in the silt may be at a 1.5 to 1 (H: V) slope and permanent slopes may be at a 2 to 1 slope. Care should be taken to rout run-off away from slopes to avoid erosion or saturation of the slope. Permanent slopes should be re -vegetated as quickly as possible to reduce the risk of erosion and improve slope stability. Structural Fill If foundation loads higher than 2000 psf are planned structural fill beneath column foundations or footings must consist of soil classified as GP, GW or GM soil types according to the USCS. This compacted, granular, structural fill over basalt will i4l IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 6 provide a maximum allowable bearing capacity of 4000 psf. Aggregate and rocks comprising the gravel should be hard and durable and should not experience significant crushing or breaking while being compacted. Because the native silt soil on the site is loose and prone to collapse it is not suitable for support of foundations in its present condition. However, if properly placed and compacted the silt is suitable for support of foundations with a contact pressure of 2000 pounds per square foot or less. Structural fill supporting concrete slab -on -grade floors pavement sections or foundations with contact pressures of 2000 psf or less should consist of GP, GW, GM, SP, SW, SM or ML soil types according to the USCS. The sandy silt soil and sandy gravel fill on the site are suitable for use as structural fill beneath foundations with a contact pressure of 2000 psf or less provided the soil is removed to expose the underlying basalt and replaced in compacted lifts as part of the site preparation. Removal and replacement of the soil will be required to help control differential settlement of the foundations. The silt and/or sandy gravel fill should be placed in loose lifts that are 8 -inches or less in thickness and compacted to a minimum of 95% of its maximum dry density as determined by ASTM D-698. The sandy silt and sandy gravel fill are also suitable for use as structural fill beneath concrete slab -on -grade floors or paved areas. Structural fill for all applications should be of high quality and should not be saturated or contain vegetation, organic matter, frozen clods, debris or other deleterious materials and should meet the soil classification requirements for the soil types listed previously. Structural fill should not contain rocks or aggregate larger than 6 inches in any dimension because the compaction equipment will tend to ride on the larger aggregate which hinders uniform compaction of the lift and can lead to poorly or non - uniformly compacted fill. Structural fill in pavement areas or in areas where concrete floors will be constructed should be placed in loose lifts that are 8 -inches or less in thickness. Each lift should be compacted to at least 95 percent of the maximum dry density of the soil, as determined by ASTM test D 698 (Standard Proctor). IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 7 Structural fill will be required beneath foundations where the planned elevation of the bottom of the footings is higher than the basalt contact. In order to provide uniform support of foundations this will require removal of all the native sandy silt and its replacement in compacted lifts or its replacement with compacted gravel structural fill. Foundation support should be as uniform as possible in order to reduce the potential for differential settlement. Use of different types of structural fill beneath footings in the same building is not recommended. Structural fill placed beneath column foundations should be placed directly on the basalt bedrock in uniform 6 -inch thick loose lifts. If contact pressures are 2000 psf or less each lift of the silt should be compacted to 95% of its maximum density per ASTM D-698. If contact pressures are 4000 psf or less each lift of gravel should be compacted to at least 95% of its maximum dry density per ASTM D-1557. The compaction requirements outlined above assume that heavy compaction equipment such as vibratory rollers with a minimum drum weight of 5 tons is used. The maximum loose lift thickness should be reduced where smaller and/or lighter compaction equipment is used. STRATA should be retained to perform field density testing of structural fill to verify contractor compliance with the above minimum compaction criteria. Lateral Earth Pressure Retaining wall systems should be designed to resist lateral earth pressures. These pressures will be generated from the soil retained, plus any surcharge from backfill materials, slopes or equipment adjacent to the walls. We recommend that lateral earth pressures be calculated using an equivalent fluid pressure (efp) of 60 pounds per cubic foot (pcf) for the at -rest case (no wall movement), 300 pcf for the passive case, (wall movement towards the soil mass), and 40 pcf, for the active case (wall movement away from soil mass). These equivalent fluid pressures assume fully drained conditions, and that no hydrostatic forces are acting on the wall. The recommended equivalent fluid pressures also assume the top surface of the backfill adjacent to all retaining walls slopes down and away from the retaining wall at a minimum of two percent for drainage. Lateral surcharge pressures due to equipment, 04 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page a slopes, storage loads, etc. have not been included in the above lateral earth pressure recommendations. The lateral earth pressure coefficient of 0.5 could be used to estimate the lateral earth pressure induced on retaining walls due to adjacent surcharge loads. We recommend all retaining walls be drained to reduce the potential for instability, leakage or seepage. Typical methods for wall drainage are illustrated on Plate 4, Schematic of Wall Drainage System and are discussed further in the Perimeter Wall Drainage section of this report. Wall drainage systems can be combined with footing drains if appropriately designed. Retaining walls should be designed for internal and external stability. We recommend STRATA be retained to provide a global stability analysis of the final slope geometry, including the designed retaining walls. We recommend a coefficient of friction of 0.45 be used for footing and wall design for concrete cast directly on the basalt or silty sand. Lateral surcharge pressures, due to equipment, slopes, storage loads, etc., have not been included in the above lateral earth pressure recommendations. The lateral earth pressure coefficient of 0.5, acting over the entire wall height could be used to estimate the lateral earth pressure induced on walls due to adjacent surcharge loads from equipment and the slope behind the structure. Below -grade walls will be subject to load influences from adjacent equipment structures and foundations. The design of below -grade walls should account for seismic load influences using an equivalent, dynamic lateral fluid pressure equal to 20 pcf. The dynamic pressure should be added to the design static equivalent fluid pressure. The above estimated passive equivalent fluid pressure will be reduced to 240 pcf during earthquake loading conditions. Care must be taken during the use of heavy and/or vibratory equipment near the face of walls (in a zone extending 5 feet back from the wall) to avoid creating an undesirable degree of over -compaction in the soil immediately along the walls and imposing high stresses on the walls. Walls designed for little or no wall movement should be monitored during the backfilling process through survey and string line methods. Below -grade walls should be backfilled as described in the Perimeter Wall Drainage section of this report. IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Flexible and Rigid Pavement Design Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 9 We recommend that all topsoil and vegetation be removed from the proposed pavement area. The upper 6 to 8 inches of fine sandy silt exposed by removal of the topsoil and vegetation should be compacted in-place to at least 95% of its maximum dry density as determined by ASTM D-698 using a large (5 -ton drum weight) vibratory roller prior to placement of subbase or base course for the pavement section. STRATA should be retained to verify the upper 6 to 8 inches of the native subgrade has been proof rolled and structural fill has been compacted as outlined. Providing the site preparation procedures are accomplished as described above, the following minimum pavement sections are recommended for the automobile parking areas: Access Road and Automobile Parking Areas: 3.0"- Class III asphalt concrete top course. 6.0%% -inch -minus, crushed sand and gravel base course. 6.0% Pit -run sand and gravel subbase course. Rigid Concrete Pavement: 6.0" - 4000 psi compressive strength (at 28 days) Portland cement concrete with a maximum 4 -inch slump and 4 to 6 percent entrained air 6.0" — %-inch-minus, crushed sand and gravel base course compacted to at least 95% of its maximum dry density per ASTM D-698. Note: We recommend a curing membrane be place on all finished exterior concrete surfaces immediately after finishing. The curing membrane The above -recommended flexible pavement sections are based on a maximum 20 -year design life. The flexible pavement sections provided above are also based on an estimated structural support R -value of 45 for the near -surface silt soil. The access road pavement section is also based on an estimated Traffic Index (TI) of 6.0. The subbase should consist of 6 -inch -minus, well -graded sand and gravel consistent with Idaho Standards for Public Works Construction (ISPWC) Section 801 and with less than 10% passing the No. 200 sieve and should have an R -value of at least 65. The subbase should be compacted to at least 95% of its maximum dry density as determined by ASTM test D-698. IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 10 The base course should consist of '14 -inch-minus, well -graded, crushed sand and gravel with less than 8% passing the No. 200 sieve and should be consistent with ISPWC Section 802 and should have an R -value of at least 80. The base course should be compacted to at least 95% of the maximum dry density of the soil per ASTM test D 698 (Standard Proctor). The asphalt concrete for the flexible pavement area should have material properties as specified in ASTM D 3515 and have a mix design with a maximum aggregate size between 3/4 and 3/8 -inch. The asphalt concrete should be compacted as required by ISPWC Sections 809 and 810. Poor maintenance and crack repair of the new pavement section will allow saturated conditions to occur in the section and underlying subgrade. The native silty sand subgrade will soften if saturated and experience a reduction of load bearing capacity. Loss in subgrade strength in the pavement section will result in early failure and higher maintenance requirements during the service life of the pavement. Therefore, we recommend that crack maintenance be accomplished in all pavement areas as needed and at least once every three to five years to reduce the potential for surface water infiltration into the pavement section and underlying subgrade. Concrete Slab -on -Grade Floors We recommend that concrete slab -on -grade floors be underlain by at least 6 inches of % -inch-minus, well -graded, crushed sand and gravel base course to provide a leveling course and moisture protection for the slab. The base course shall be placed over the native basalt or structural fill compacted to at least 95 percent of its maximum dry density as determined by ASTM test D 698 (Standard Proctor). The native silty sand is suitable for support of the concrete slab on grade provided the upper 6 to 8 inches is compacted, in-place, to at least 95% of its maximum dry density per ASTM test D-698. The base course should be compacted to at least 95 percent of its maximum dry density as determined by ASTM D 698 (Standard Proctor). Subgrade areas that become soft, wet or disturbed must be overexcavated to dense, native soil or basalt and replaced with granular structural fill. The base course and vapor barriers should be installed after the majority of under slab plumbing and utilities are completed. Floor slabs should be designed for the anticipated use and equipment or storage #4 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR•PO5040A Page 11 loading conditions. Based on correlation to our field and laboratory test results, we recommend a modulus of subgrade reaction (k) of 230 pounds per cubic inch (pci) be used for concrete floor slab design. This modulus is based on a sandy silt subgrade with at least 6 inches of properly compacted %-inch-minus base course sand and gravel beneath the floor slab. Moisture migration through floor slabs can break down a floor covering, its adhesive or cause various other floor covering performance problems. We recommend the owner consider a vapor barrier for concrete slab -on -grade floors. Vapor barriers should consist of a thick (10 mil), puncture resistant, polyethylene sheeting covered with and additional 2 -inch thick layer of clean, coarse sand placed between the base course and the concrete slab -on -grade floors. Form stakes should never be allowed to penetrate the barrier. Although these recommendations are used, water vapor migration through the concrete floor slab is still possible. Floor covering should be selected accordingly. Manufacturer's recommendations should be strictly followed. Perimeter Wall Drainage We recommend below grade walls be drained to reduce the potential for instability, leakage or seepage. Free -draining, granular structural fill should be used to backfill all below grade walls. Locally supplied top and base course gravel conforming to ITD specifications and with less than ten percent passing the #200 sieve is an acceptable backfill. Two typical wall drainage details are presented on Plate 4, Wall Drainage System. Wall and foundation drain systems may be combined; however, they should never be connected to roof drains. All retaining walls greater than four feet should be designed to resist sliding, overturning, bearing and global stability failures. From our experience, segmental landscape walls can realize some design efficiencies if accomplished by the geotechnical engineer while performing global stability assessments. No matter how the wall design is performed, global stability must be considered for landscape walls. IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Seismicity Addition to Madison Memorial Hospital Rexburg, ID File! AMSCOR-PO5040A Page 12 We understand the 2003 International Building Code (IBC) will be utilized for project structural design. Section 1615.1 of the 2003 IBC outlines the procedure for evaluating site ground motions and design -spectral response accelerations. STRATA utilized site soil and geologic data and the project location to establish earthquake loading criteria at the site referencing Section 1615.1 of the 2003 IBC, Based on the results from exploration, and our review of well logs in the area, we recommend a Site Class B be utilized as a basis for structural seismic design for the project. The Maximum Considered Earthquake (MCE) maps from the 2003 IBC were referenced to develop the site response spectrum for Site Class B. The recommended response spectrum is presented in Figure 1, below. This response spectrum assumes a five percent critical damping ratio in accordance with the IBC, Section 1615.1. A site- specific study was not performed. Structural design may use the spectral response at period T=0.3 seconds for peak ground acceleration at the site. Individual seismic response criteria as utilized to develop the response spectrum are presented in Table 2 below. Design Criteria Value IBC 2003 Reference Ss 0.5 Figure 1615(1) SI 0.17 Figure 1615(2) FA 1.0 Table 1615.1.2(1) F„ 1.0 Table 1615.1.2(2) SMs 0.5 Equation 16-38 SMI 0.17 Equation 16-39 SDs 0.33 Equation 16-40 SD1 0.11 Equation 16-41 To 0.07 Section 1615.1.4 Ts 0.33 Section 1615.1.4 aulu c. otwmc response untena for ]BG 2003 !4 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 13 Site Geology The geology of eastern Idaho, specifically the Rexburg area is characterized by a complex series of volcanic calderas, volcanic vents, faults and basalt flows overlain by varying depths of windblown soil. The Rexburg hill consists of a ryolite caldera associated with the Yellowstone volcanic hotspot. After the ryolite 'volcano" became extinct, Quaternary aged basalt of the Snake River Group erupted through the discontinuities in the ryolite core and covered much of the present-day Rexburg hill. Following emplacement of the basalt, windblown silt or "loess" covered the basalt to various depths. Based on our experience in the area and the observed conditions on-site, the conditions on-site are typical of the area and consist of windblown loess, underlain basalt. The basalt in the area is typically variable in nature and can change in appearance and engineering performance in short lateral and vertical distance. The basalt may contain inclusions of the surrounding soil, ryolite clasts, cinder zones, large voids and zones of massive basalt. Figure 1 below illustrates typical basalt properties in the Figure 1. Typical Rexburg Area Basalt Foundation Design The site preparation procedures discussed above must be implemented prior to initiating foundation preparations. We recommend all foundations for these structures bear on basalt bedrock or properly placed and compacted structural fill over basalt i4 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.COM Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 14 bedrock. If native soil is removed and structural fill is required to achieve the desired footing elevation the width of excavation should increase 1 foot horizontally on each side of the footing for every two feet of native soil removed to expose the basalt bedrock. The native sandy silt excavated below footings may be reused as landscaping fill, structural fill for footings with a contact pressure of less than 2000 psf, in pavement areas or as backfill against foundation stem walls or soil retaining walls. The silt should be properly moisture conditioned and compacted as outlined for structural fill in the pavement areas. The following recommendations should be accomplished for all foundations for the hospital: 1. SITE OBSERVATION: Strata should be retained to observe ail footings (soil improvement) overexcavations to verify dimensions, structural fill, and to verify that all bearing surfaces have been prepared in accordance with this report. 2. EXTERIOR FOOTINGS: Exterior footings should bear at least 36 inches below the final exterior grade to help reduce frost effects. Interior footing_ s should bear a minimum of 18 inches below the finished floor elevation. 3. FOOTING WIDTHS: Minimum strip footing widths should be consistent with the International Building Code (IBC). 4. FOOTING SUBGR.ADE: Loose soil, rock or debris must be removed from the basalt surface prior to placement of structural fill or concrete. Footings should never be,constructed over loose, saturated or frozen soil. If loose or unstable areas are observed prior to placing structural fill or concrete, they should be overexcavated to 'he basalt and replaced with compacted granular structural fill. Structural fill should extend a minimum of'i foot beyond the footing edge on both sides of the footing for every 2 feet of vertical depth. 5. ALLOWABLE BEARING VALUE: If above recommendations are accomplished; a maximum allowable bearing value (ABV) of 4,000 psf for iuunticl"un ull uuuiNduteu gravel uver basalt art' 2000 psf for foundations on re -compacted silt over basalt could be used for the footing design. IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www. stratag eotech. con Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 15 Placement of individual footings on the existing gravel is not recommended because the relative density of the gravel is variable and could lead to non-uniform support of the foundations. 6. ANTICIPATED SETTLEMENT: If the above bearing soil, site preparation, earthwork and foundation recommendations are accomplished, we anticipate total settlement will be less than 1/4 inch and differential settlement will be less than 1/8 inch per 25 feet of wall length, or between similarly loaded footings that are not less than 25 feet apart. 7. LIQUEFACTION POTENTIAL: Potential for liquefaction on the site is limited to the fine sandy silt covering the site. In order for liquefaction to occur in the sandy silt the soil would need to be saturated and loose during a seismic event. Since the sandy silt layer is relatively thin and underlain by moderately fractured basalt it is unlikely that saturated conditions will occur and remain on the site. Therefore it is our opinion that the potential for liquefaction on the site is very low. 8. SOIL PROFILE CLASSIFICATION: Our site geologic research, exploration findings, and our experience in the project vicinity indicate structural design may utilize a Site Class B for seismic design referencing section 1615 of the 2003 IBC. Grading, Drainage and Storm water Disposal Wet Weather Construction We recommend that site construction be undertaken during dry weather conditions. If the site preparation and grading is undertaken during wet conditions, the native or re -compacted silty or sandy soil will be susceptible to pumping or rutting when subjected to heavy loads from rubber -tired equipment or vehicles which exert a point load. Wet weather earthwork should be performed by low pressure, track -mounted equipment that spread and reduces the vehicle load. Work should not be performed immediately after rainfall. All soft and disturbed areas should be excavated to undisturbed soil and backfilled with structural fill. Alternatively, the area should be moisture conditioned and re -compacted to structural fill requirements. Assuming the soil is wet and soft but not disturbed, the initial layer of fill placed over the native soil should be at least 12 inches, but no greater than 24 inches, in depth. Compaction of the fill should be sufficient to prevent pumping of the native soil. 114 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR•PO6040A Page 16 Subgrades that become disturbed under construction traffic will require overexcavation to remove soft or disturbed soil. Overexcavated soil should be replaced with compacted structural fill. In summary, careful construction procedures are critical to the successful grading operation if the onsite soil is at or above optimum moisture content and loose. Consulting STRATA prior to initiating this type of construction is recommended to help improve earthwork efficiency and achieve a stable subgrade. Surface and Subsurface Drainage Site grading, including all sidewalks and landscaped area grading, should slope a minimum of 2 percent away from the proposed building to help prevent ponding and to direct surface runoff away from the structure. All runoff from downspouts, roof areas, sidewalk areas, landscaped areas, and other large volumes of storm water should be directed and maintained away from the structure and not be allowed to infiltrate the soil beneath the building area, sidewalks or footings. All drainage should be directed to an approved discharge and/or collection facility, such as shallow detention ponds or seepage beds, located a minimum of 50 feet away from building foundations. The native silty sand encountered in the test pits can be used for storm water disposal. Filtration beds in the native soil should be designed using an infiltration rate of 20 minutes per inch. Gravel used to construct filtration beds should be separated from the native soil by a non -woven filter. If silt or clay fines are permitted to enter the gravel it will greatly reduce the infiltration rate and reduce the efficiency of the storm water disposal system. It will be critical to control water from the structure to reduce the potential for soil saturation that could create conditions where ice heaving or differential movement of sidewalks or other improvements could occur. Void Detection and Remediation Alternatives Borings have been drilled at predetermined locations across the site. Areas of possible voids or cinders have not been detected in any of the borings. However, isolated areas of voids or cinder pockets may be exist within the project limits and may not become apparent until after construction has commenced. If voids or areas of weaker basalt are encountered remediation may be required # I IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, ID File: AMSCOR-PO5040A Page 17 Remediation alternatives include 1) blasting to collapse the areas, 2) using concrete grout to fill the zones or 3) excavation of the basalt, voids or cinders and replacement with compacted structural fill. Based on the information obtained from the borings, we do not anticipate large areas requiring remediation. If voids are encountered during construction Strata should be notified to assess the discovered conditions and provide recommendations for remediation. Loading on the concrete floor slab is much less than the loads supported by footings for the structure. The rock cores obtained at the site indicate approximately 5+ feet of competent basalt with a compressive strength of approximately 4000 to 8000 pounds per square inch underlying the site. Based on the high compressive strength of the basalt rock and the relatively light floor loads, remediation of the basalt under the concrete floors should not be required. ADDITIONAL SERVICES RECOMMENDED Review of Plans and Specifications We recommend that STRATA be retained to review the civil and structural foundation plans and earthwork specifications prior to bidding of the construction documents. It has been our experience that having the geotechnical consultant from the design team review the construction documents reduces the potential for errors, and also reduces costly changes to the contract during construction. STRATA can provide review of the construction documents on a time and expenses basis. Construction Observation and Testing We recommend that STRATA be retained to observe the exposed subgrade in all building footing trenches and sidewalk areas to verify site stripping, and excavation has been accomplished to the recommended native bearing soil, that all soft or unsuitable soil has been removed as described above, and that all bearing surfaces have been prepared in accordance with this report. STRATA can provide construction material testing and special inspection for earthwork, concrete, asphalt, masonry, and steel. If we are not retained to perform the recommended services, we cannot be responsible �41 IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com Addition to Madison Memorial Hospital Rexburg, to File: AMSCOR-PO5040A Page 18 for soil engineering related construction errors or omissions. The recommended services are not included in this evaluation and would be billed on a time and expense basis. EVALUATION LIMITATIONS This geotechnical engineering report has been prepared to assist planning, design of the proposed additions to Madison Memorial Hospital in Rexburg, Idaho. Our services consist of professional opinions and recommendations made in accordance with generally accepted geotechnical engineering principles and practices. This acknowledgment is in lieu of all warranties either expressed or implied. The following plates accompany and complete this report: Plate 1: Vicinity Map Plate 2: Site Map Plate 3: Unified Soil Classification System (USCS) Plate 4: Schematic of Wall Drainage System Appendix: Exploratory Boring/Laboratory Results IDAHO MONTANA NEVADA OREGON UTAH WASHINGTON WYOMING www.stratageotech.com N jj FFFTTFTI FT7 MTM z UNIFIED S®MS V_LA(RF-,Vrlirt-AT7rnN QVccqrrq1nK SOIL CLASSIFICATION CuaaT IStandard 2—Inch OD Split—Spoon Sample .Groundwater — After 24 Hours BG MAJOR DIVISIONS GRAPH SYMBOL LETTER SYMBOL TYPICAL NAMES RG Bulk Sample Ring Sample «: GW Well—Graded Gravel, CLEAN Gravel—Sand Mixtures. BORING LOG SYMBOLS GRAVELS Q GP Poorly—Graded Gravel, GRAVELS Gravel—Sand Mixtures. GRAVELS GM Silty Gravel, Gravel— WITH Sand—Silt Mixtures. GC Clayey Gravel, Gravel— COARSE FINES GRAINEDSand—Clay Mixtures. SOILS < < ° ° , ;; SW Well—Graded Sand, CLEAN o o Gravelly Sand. SANDS SP Poorly—Graded Sand, SANDS Gravelly Sand. SANDS e SM Silty Sand, WITH E Sand—Silt Mixtures. `' .� u ` SC Clayey Sand, FINES E. e, Sand—Clay Mixtures. ML Inorganic ilt, Sandy SILTS AND CLAYS or Clayey Silt. Inorganic Clay of Low LIQUID LIMIT CL to Medium Plasticity, LESS THAN 50% Sandy or Silty Clay. I 1 I 1 I 1 OL Organic Silt and Clay FINE 1 1 1 of Low Plasticity. GRAINED Inorganic Silt, Mica— SOILS MH ceous Silt, Plastic SILTS AND CLAYS Silt. CH Inorganic Clay of High LIQUID LIMIT Plasticity, Fat Clay. OH Organic Clay of Medium GREATER THAN 50%\ to High Plasticity. PT Peat, Muck and Other Highly Organic Soils. SOIL CLASSIFICATION CuaaT IStandard 2—Inch OD Split—Spoon Sample .Groundwater — After 24 Hours BG Baggie Sample IIRock California Modified 3—Inch OD Split—Spoon Sample Core Q GroundwaterBK =_ at Time of Drilling RG Bulk Sample Ring Sample Shelby Tube 3—Inch OD Undisturbed Sample BORING LOG SYMBOLS GROUNDWATER SYMBOLS TEST PIT LOG SYMBOLS SYFR&-r& C'EJIJ:NN CK_ EilOI!1EEE'�'C g 11.\IEFI!ld'E611!A.. 'f�IY.�Y: Y�. FV✓a.t hnS �] p„Y,d!Jf- File: PLATE- 'i THIS DRAWINGS' CROSS-SECTIONS MAY BE USED FOR GRAVITY WALLS. THIS IS NOT A STRUCTURAL DETAIL. 2% SLOPE e WALL MEMBRANE AS APPROVED BY THE PROJECT ENGINEER a e d 3/4 IN. BASE COURSE ° CONCRETE d FLOOR ' ° 0 °d I=1 I I INFORMATIONAL ONLY (NOT TO �% SLOPE 12 -INCH SOIL COVER IIII I 'I BY THE PROJEOCT VED ENGINEERS UNDISTURBED NATIVE OR COMPACTED GRANULAR MATERIAL 12 -INCH SOIL COVER MIRADRAIN OR EQUIVALENT UNDISTURBED NATIVE OR COMPACTED MATERIAL Pop NON—WOVEN PERFORATEDFILTER FABRIC . E.0.5% MINIMUM • • •. UNDISTURBED NATIVE OR COMPACTED MATERIAL REFER TO MANUFACTURER'S SPECIFICATIONS AND TEXT OF REPORT FOR INFORMATION REGARDING DRAINAGE SYSTEM, WALL DESIGN AND RELATED GEOTECHNICAL CONSIDERATIONS. SAND OR GRAVEL BACKING = 4 -INCH -DIAMETER, PERFORATED PVC PIPE LAID WITH A 0.5% MINIMUM LONGITUDINAL SLOPE WITH (1 -INCH) DRAIN ROCK WRAPPED IN FILTER FABRIC. sYFI&Y& 4EOriGFNI":4EIIG NE6q NC E Ia14TE�lALS ISTN/i �(I,x�v! y Frew x:Ls �rneNA ter SCHEMATIC OF WALL APPENDIX BORINGS, & LABORATORY TEST RESULTS F Boring No. I I Subsurface En JL! w N 0 } w o Soil o �� CO aFP °0 c o oo � o—` v U c REMARKS s i tion Cn 'n CO ED m o_ U c O o a E W— Fine Sandy SILT (native) — ML brown, loose, slightly moist. 1 2 3 qbIack, 4 8 4 30/1 > V`A> +, BASALT —>�`A> strong to>moderatel ;ti�A; RX �>1<A> >N<A> 60 >N<A> 9 >ti<A> >� <A> <� L �' A 10 > °<A> Boring Terminated in basalt RX i`A> ' at 11' ', r` >�,A>� 7� , i 12 13 14 15 File: AMSCOR Boring Number: 1 EKpLOo AyORV Project No.: P05040A Date Drilled: 4/18/2005 O EON@ LOOS Drill Rig: CME 75 Boring Diameter: 0.2' core S T R aTa T, y,,yF, N;F .:n<Mnnop sweet g of 1 Depth to Ground Water: NA Logged By. JPB Boring No. ; J w o I y Subsurface Soil a w a NJ m a N 0 0~ a c o i° o- o > � t o— a Y v v o REMARKS Description c N~ m ma 0 0 w _= a n F Fine Sandy SILT (native) — brown, loose, slightly moist. ML 1 2 3 4 5 2 17 6 2 6 7 8 9 10 s <n 5;<n5 I BASALT —Gray to black, r>;<n> >ti<n> strong to very strong, RX moderately fractured. >� n> 13 > i n> �<n> ` �' ` 60 14 > <n> > <n> �a n> Boring Terminated in basalt 16� 15 40 d<n> 0 File: AMSCOR Boring Number: 2 E`pLOo aVO�� 0 �Q��� �0�� Sheat Il of Il 04 SYRaTa Project No.: P05040A Date Drilled: 4/18/2005 Drill Rig: CME 75 Boring Diameter: 0.2' core Depth to Ground Water: NA Logged By. JPB��+��--r-�r�^��-<��•�n.���1• Boring No. r 0 N o J y o 1 N o N Subsurface Soil 1 v" °' o , d o ` o =W LU REMARKS Description _ o N~ mm; o , o v LU Fine Sandy SILT (fill) — brown, loose, slightly moist. 1 ML Fine to Coarse Sandy GRAVEL GP Q — (fill) brown, dense, damp t .o:: ':b•�% moist. 3 0. tr .g dr ..o.:. 4 a.. 5 0. O X92 2 6 50/1' BASALT — Gray to black, hard to 'v very hard, fresh, fine to'G^� 6 moderate grain, closed joints RX >;� >; with moderately to widely >'h-A>N spaced fractures. >�<A>' 7 G' >j<A> >;<A>; 60 RQD = 1007 >N. 8 <A > * AL >;'A>; 9 G >�<A>N A7 G> �<A> G Boring Term. in basalt 10.5' 10 ^>>x�A;x 5 11 12 13 14 Boring Terminated in basalt 16' 15 File: AMSCOR Boring Number: 3 Project No.: P05040A Date Drilled: 4/18/2005 QORHO L082 Drill Rig: CME 75 Boring Diameter: 0.2' core STRaT� ,. Sheet I of 1 Depth to Ground Water: NA Logged By, JPBr. Boring No.' � a J m a° 3 N > w Subsurface Soil A7-- o_ N a a= t o—. Y° L REMARKS Description 0 m m v o -. `o o_ M — a a 4) Fine to Coarse Sandy GRAVEL (fill) — Light brown, dense, moist. 1 1 GP BASALT Fine Sandy SILT (nabrown, loose, slightl A7-- — Gray to black, strong to very strong, moderately fractured. HI Bnrinn Tarm!nm.l ;.. L... -- U at 14' p File: AMSCOR — P05040A Project No.: P05040A g Drill Rig: CME 75 Depth to Ground Water: NA >�zA>; RX >I<A>N 8 >i<A>i L >H<n>H 9 >1A>i >H<A>H >)<A' V 10 RX >,<A>ti <A>� 11 >ti7A>ti �<A>j 12 ;<A>AH > <A>V H<n>H 13 n7 �<A> V .7 L l 9 18 84 3 Number: il Drilled: April 18, 2005 1 Diameter: 0.2' Core-rRa�-a 0OMHO LOW Sheet Y of & Boring No. 5v Subsurface Soil �N o m o a �� 0 Y N W Description _ Q N~ a= m o n; 0` v c� v a 0 o w REMARKS — as 0 L E Fine to Coarse Sandy GRAVEL — (fill) Light brown, dense, j GP ':�:.•0; moist. 2 :.... . a •. p.. 3 �.. a.• 9. 4 o:O o� 5 BASALT — Gray to black, >ti<ti n> strong to very strong, RX >N<njH moderately fractured. 8 >i<A> >^ <n>H >�<n>b 9 <n>> ^ ^ > V<n> 84 10 RX >'I<n>S _ > �G^>N 11 >ti<n>i 4> >N<A>N t� >ry<n>� 12 <n `> ti ^>> > <n>+ 13 > Boring Terminated In basalt > <n>� ; at 14, V�^> V C A.^ 15 File: AMSCOR — P05040A Boring Number: 540�� 0 �Q��O ���� Project No.: P05040A Date Drilled: April 18, 2005 Drill Rig: CME 75 Boring Diameter: 0.2' Core �TRaTa �•r--.�,u�r. ^--�r�...,.,>e Sheet I of g Depth to Ground Water: NA Logged By: JPB Boring No.5 W o I N Subsurface Soil N am w —W REMARKS`NDescription o CO Q_ L — as E :.g Fine to Coarse Sandy GRAVEL:.6:..00 (fill) — Light brown, dense, GP ::o:•�• moist. 1 4:1. o.... 2 o.. o v w.: >,<A> N � <n> Li 7 L L> > v<n> v BASALT — Gray to black, 5 RX > L> A>" <> strong to very strong, >ti�A>'� moderately fractured.A>N 6 Iti A>1 "<A>" 60 <A> 7 >,<A>H A> < Boring Terminated in basalt > >"<n>N at 6 L> 9 10 11 12 13 14 15 File: AMSCOR — P05040A Boring Number: 6 IMPLOPATOWY QOQSHO LOW Project No.: P05040A Date Drilled: April 18, 2005 Drill Rig: CME 75 Boring Diameter: 0.2' Core sTRa-ra �^�-e•-yYF ^ �--�>:...,.�:r. Sheet I of i Depth to Ground Water: NA ILogged By. JPB Boring No. 7 = V) V) 0 J v o o N Subsurface Soil W �g °' M oa a o� o = 1 d REMARKS Description _ N~ m m C c 0 o � — v a a P Fine Sandy SILT (native) — brown, loose, slightly moist. ML 1 2 3 4 5 5 6 11 5 7 8 BASALT — Gray to black, '`^< very strong, widely spaced fractured. 10 ;<^> <,< sX�^s 12 RX >"<^> ;<^> 13 ;ti ^; <,< SM Ate' Boring Terminated in basalt 14' 15 File: AMSCOR Boring Number: 7 Project No.: P05040A Date Drilled: 4/18/2005 QOQ��R LO�aO Drill Rig: CME 75 Boring Diameter: 0.2' core S T R 3T 3 �i���--'��,ryF„k... ,Fe�.<:,'.ee Sheet g of 1 Depth to Ground Water: NA Logged By. JPB