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HomeMy WebLinkAbout257 GOLDEN VIEW ,IELEA4ENTARY SCHOOL Subsurface Investigation & Foundation Recommendations 4040 "B' Street Anchorage, Alaska NOVEMBER 1982 DOWL En :i eers 4040 "B" Street Anchorage, Alaska 99503 Phone (907) 278-1551 ( Telecopler (907) 272-5742 ) August 13, 1982 W.O. ~D13965 erid: 3137 ECl/Hger 101 8enson, Suite 306 Anchorage, Alaska 99503 Attn: Terrg Hger SubJ: SubsurFace Soils Investigation ~olden View Elementarg School Dear Mr. Hger: Transmitted herein are the results uP the soils investigation and Poundation studg Por this project. This report includes 12 boring logs with accompanging laboratorg testing, and provides recommendations regarding Poondations, drainage, earthwork, and trample areas. The ~oundation recommendations presented herein rePlect our present understanding o~ the proposed development, and the nature o~ the subsurface soils encountered at the site bg this exploration. I~ gout development plans change, or it becomes apparent during construction that subsurPace soil conditions di~Per Prom those encountered during our be contacted immediatelg to to evaluate the recommendations investigation, we should consider those changes and uP this report. IP gou have ang Euestions regarding this report, please Peel Pree to call. Verg trulg gouts, DOWL ENQINEERS Melvin R. Nichols, Partner MRN: kP Attachment(s) M2nric~ P Oswald Kenneth B. Walch Melvin R. Nichols SUBSURFACE INVESTIGATION AND FOUNDATION RECOMMENDATIONS GOLDEN VIEW ELEMENTARY SCHOOL Prepared for: ECI/Hyer Prepared by: DOWL ENGINEERS Ja~{es R. ., P.E. Geotechnical Engineer Melvin R. Nichols, P.E. Partner August, 1982 W.O. #D13965 TABLE 8F CONTENTS PA~E Introduction 1-2 Site Conditions Surface Subsurface Qround Water 3 Conclusions Drainage Waste Water Disposal Foundation Tgpes 4 4-6 Recommendations Drainage Surface Drainage Site Preparation Site Fill Spread Footings Pile Foundation Test Piles and Load Tests Frost Protection Lateral Earth Pressures 6-7 7 7-8 8-10 10 10-11 12 12-14 Inspection and Monitoring 14 Field Exploration and Laboratorg Testing Resistivitg Surveg 16-17 Vicinitg Map Figure 1 Test Boring Locations Figure generalized Subsurface Gross-Section Figure 3-5 Test Borings Figures 6-18 grain Size Distribution Curves Figures 19-21 Allowable Pile Capacitg Figure Negative Skin Friction Due to Fill Consolidation Figure 23 Apparent Resistivitg Map Resistivitg Surveg Results Figure 24 Figure 26 Appendix A Northern Technical Report Investigation SUBSURFACE INVESTIGATION AND FOUNDATION RECOMMENDATIONS 0OLDEN VIEW ELEMENTARY SCHOOL ANCHORAGE, ALASKA INTRODUCTION This report presents the results o~ a subsurface investigation and the ~oundation recommendations ~or the proposed Golden View Elementarg School. The site is located north oF Rabbit Creek Road and west o~ Golden View Drive as shown on Figure 1. The site contains approximately 15 The proposed building is to be a one-story structure with an aproximate Floor area o~ 50,000 square Feet. According to the structural engineer, the maximum column load will be approximatelg 50 kips. The Floors will be constructed o~ concrete slabs. The Finished ~loor elevation will be 629.75 2eet ~or the upper part and 628.0 ~or the lower part oF the building. The ~loor grades aree approximately o~ 6 to 22 2eet above the existing ground surface. A parking lot and bus turn-around will be constructed on the east, or the uphill, side o~ the school, between the school building and Golden View Drive. The parking lot will be cut into the hill, requiring cut depths o~ up to 8 ~eet. Figure 2 shows the approximate building location and the site topograhy. Based on our discussions with the architect and structural en§ineer, we understand the current plan is to use spread ~ootings, ~ounded on natural soils, ~or the building ~oundation. Concrete block (CMU) walls and columns will be constructed on the ~ootings to transfer the building loads to the ~ootings. Fill mag be placed under the building to reduce the lateral loads on the outside ~ooting wails and possiblg ~or 2ire protection, iF required bg the Municipalitg Fire Ma?shall. Fill will be placed on the outside o~ the building to provide at-grade access to all sides oF the building and to provide level plag areas. In this investigation, we have examined several methods o~ supporting the building other than spread Footings Founded on natural soils. These include pile or pier Foundations and spread ~ootings ~ounded on engineered ~ill. These alternatives are also discussed in this report. On-site potable water and waste water disposal sgstems are to be constructed. We understand that the septic sgstem will be constructed on the west~ or downhill~ side oF the school building. A reconnaissance soils investigation on this propertg was conducted bg Northern Technical Services (Nortech) in November~ 1~81. A copg o~ their report to the Municipalitg o~ Anchorage ~ Phgsical Planning Department~ is included in the appendix to this report~ The purpose o~ our investigation was to: 1) explore the subsurface soil and ground water conditions at the site; 2) define criteria eot recommended ~oondation tgpes~ 3) evaluate the bearing capacities and settlements which might be experienced bg the structure as recommended~ and 4) provide earthwork and drainage design criteria. To accomplish the purposes o~ this investigation, a program oF Field exploration, laboratorg testing and engineering analgses was undertaken. The ~ield investigation consisted o~ drilling a total o~ 13 test borings at the locations shown on Figure 2. The boring depths ranged ~rom 20 Feet to 50 ~eet. The deeper borings were placed in areas where the most loads on the soil are expected. In addition, an electromagnetic resistivitg sorveg o~ the site was conducted. The details and results o~ our ~ield exploration and laboratorg testing are presented in the text Following the Conclusions and Recommendations sections. SITE CONDITIONS Surface. The site slopes downward to the west at an average grade o~ 6 to 12 percent, shown on Figure 2. The long axis oF the proposed building is oriented parallel to the general surface topographg. Slopes within the building site range From 6 to 15 percent, with an average slope o~ between 8 and 10 percent. The ground surface was wet and so~t at the time o~ our exploration. The surface vegetation consisted predominatelg oF a mixture oF spruce and birch trees, mad willow and alde~ bushes. A small creek ~lows just south of the school site, through the southwest portion o~ the propertg. Oround seepages were observed at various locations throughout the propertg area. Subsurface The subsurface soil and ground water conditions are illustrated schematicallg on the subsurface cross-sections, Figures 3 through 5, and on the test boring logs~ Figures 6 through 18. The site is overlain bg a lager o~ peat and organics varging {rom ~ to 6 ~eet in depth at the test boring locations. The peat is so~t and saturated. Below the peat is a dense glacial till, consisting o2 a heterogeneous mixture o~ silt, sand and gravel. Tgpicallg, the till soils have a Unified classification o~ SM and contain 20 to 30 percent non-plastic silt, and 20 to 30 percent gravel, the remainder o~ the material is sand. Representative grain size distribution curves o~ this material are shown on Figures 19 through 21. The particles tend to be sub~ounded to subangular. Cobbles and boulders up to 12 inches in diameter were ~ound throughout the soil strata. glacial erratics (large boulders), although not encountered bg the test borings, mag be present within the soil unit. The densitg o{ the glacial till soil increases with depth. Penetration values in the upper 10 ~eet o~ the soil are on the order o~ 30 to 50 blows per ~oot. Below this, the blow counts are tgpicallg 80 to more than 100 blows per The drg densitg o~ the soil based on a limited number laboratorg tests, is 135 to 140 pounds per cubic ~oot and the wet densitg is approximatelg 150 pounds per cubic ~oot. Some cleaner sand and gravel lagers were encountered in the predominatelg siltg till soils. In borings 1 and 2J which extended to 50 2eet, a clean sand was encountered at depths o~ 38 and 42 ~eet, respectivelg. ~roundwater At the time o~ our {ield explorations, the upper ground water surface varied ~rom the ground surface to the inter,ace between the peat and till strata. This is a perched water condition with water ~lowing through the organics downhill over the less permeable glacial tills. Data ~rom the piezometers installed in the borings indicate several piezometric sur2aces in the area explored. In Test Boring 1~ the piezometric level in the lower sand a~ui~er was at 44.0 2eat. In Test ~oring 8 the piezometer readings indicate that there is a piezometric surface at 15.0 ~eet below the ground surface, as well as at the ground surface. In Test Boring 12 a piezometric surface was measured at 10.0 ~eet and also at the ground surface. These data indicate that ground water is perched above the till surface within the peat and that water is present within the more permeable lagers o~ the till. 3 CONCLUSIONS Drainaqe. Surface and subsurface drainage are important design considerations. Surface drainage can be provided bg properlg designing ~inal site grades. Since there is an abundance o~ near-surface ground water on the site~ we recommend that subsurface drains be constructed to intercept the ground water which ~lows downhill above the peat glacial till inter,ace. The ground water should be intercepted at several locations. Waste Water Disposal The site is not suitable ~or the construction o~ conventional on-site septic sgstems and drain 2ields due to the presence o~ high ground water levels, Even i~ the near-surface ground water were drained awag ~rom a disposal area bg cut-o~ trenches~ a verg large drain ?ield would be necessarg due to the relativelg low permeabilitg o~ the on-site soils. Foundation Tgpes We have considered several ~oundation tgpes including the A. Conventional spread ~ootings placed on engineered ~ill. Conventional spread ~ootings ~ounded on a ~ill o~ uniform thickness. C. Deep ~oundations, including drilled piers~ auger cast piles~ and driven steel H piles. D. Spread ~ootings ~ounded in the till soils, with the building supported on .columns attached to the ~ootings. With stringent control o~ both the ~ill Eualitg and placement, it could be possible to place the building on engineered ~ill. Even with these precautions, differential settlement between the thicker and thinner areas o~ the 2iI1 could be expected. Assuming a compression o~ 1 percent, the total differential settlement could be on the order o~ 3 inches. The building structure would have to be designed ~or such differential settlement. The ~ill reEuired to limit settlement to tolerable amounts would need to be oF a high qualitg. A uniform thickness o~ Fill would reduce the possible occurrence of substantial differential settlements, provided fill is plmced in a uniform manner with stringent Eualitg control. The principle disadvantage oF this option would be the extra cost oF the additional cut and fill (approximatelg 25,000 cubic gards under the building alone), and the fact that the building would be setting on a deep fill. We could not recommend this approach unless gout schedule allowed this fill to set For several months prior to placement oF the Footings. Supporting the building on deep ~oundations such as driven piles or drilled piers Founded on the dense till soils below the peat would minimize total and differential settlement. OF the possible deep Foundation tgpes, steel H piles appear to be the most suitable. The soils are verg dense and contain cobbles and boulders, thus penetration oF the soils bg drilling methods for installation o~ drilled piers or auger cast piles could be a slow and costlg process. Casing o2 drilled pier boring might be reEuired in the fill and in water bearing zones beneath the fill. The need for casing can be eliminated bg using auger-cast piles. These mre constructed bg drilling a hole with a large diameter hollow stem auger drill. Qrout is pumped through the auger under pressure into the hole as the auger is withdrawn. If Fill is placed under the building, downdrag loads as the Fill consolidates would be a major load component on a deep Foundation sgstem. The drilled piers or auger cast piers have a large surface area and thus, larger downdrag loads. Also, the roughness of the concrete surfaces would tend to increase the soil-pile Friction. Steel H piles, as opposed to pipe or wood piles, are recommended because the H shape is better suited for penetration into the hard soils that contain cobbles and occasional boulders. The ends of the piles should be protected bg cast pile tips, such as those manufactured bg Piletips. Further recommendations on the load bearing capacitg and pile design are contained in the next section oF this report. Spread footings, placed on the dense glacial soils is another acceptable alternative. Because of the site grades, the building would have to be supported on columns and/or large footing walls. With either pile foundations or spread Footings, it is not necessarg to construct the ~ill pad to support the building. The ~unction o~ the ~ill is ~or esthetics and to provide at-grade access to the building on all sides~ and as a working surface to ~orm the structural ~loor slab. The ~ill also provides lateral load resistance. RECOMMENDATIONS Drainaqe As a minimum, we recommend that subsurface drains be provided above the parking area, above the building ~ill and at the toe o~ the building pad ~ill. The drainage trench above the parking lot should be constructed uphill From the top oF the cut slope. The depth o~ the trench should extend to at least 3 ~eet below the lowest parking lot grade, or 1~ ~eet, whichever is greater, The 1~ Feet minimum requirement is below the existing ground surface. A trench oF this depth will intercept water Flowing through the peat and through more permeable zones in the soils immediately below the peat. The, bottom oF the trench, based on the test boring information, should be in the dense~ glacial soils. An additional 12 ~oot deep trench should be constructed between the parking lot and the building pad. Also, a drain should be placed at the base oF the building pad slope to intercept any water Flowing under the Fill. The lower drainage trench should extend at least I Foot below the lowest grade oF the building ~ill. Other subsurface drains mag be required to lower the ground water levels in the waste water disposal area, in play ground areas, etc., as determined by the civil engineering site designer. The drainage trenches may be constructed by excavating a trench approximately ~ Feet wide, placing a 6 inch layer oF washed sewer rock (gravel) in the bottom, and then placing a per~orated pipe wrapped in ~ilter ~abric on the washed rock. The trench should then be back~illed with a 12 inch lager o~ washed rock. The remainder o~ the trench can be back,iliad with a clean, sandy gravel to the ground surface. The gravel should have not more than 5 percent silt, and not more than 40 percent particles passing the sieve. The gravel and washed rock backfill mag be nominally compacted except under roadways where the top ~eet o~ gravel should be compacted to at least 95 percent o~ its maximum density as determined bg the American Society oF Testing and Materials, (ASTM), test procedure D1557, 6 F As an alternative, the drains mag be constructed with a synthetic vertical drainage system such as Qeo~ab or E1jin drainage systems. Such a system consists o~ a corregated plastic core with ~ilter ~abric on each side. The product is placed in the trench vertically 2rom near the ground sur2ace to the bottom. A per2orated or slotted pipe is placed in a pocket in the bottom portion o2 the 2ilter to transport the water to a discharge area. With this system a lesser quality o~ back~ill mag be used. We recommend that the back~ill consist o~ non-organic and non-plastic soil containing not more than 10 percent silt. It should be compacted as described above. We recommend constructing drainage trenches before excavating within the parking or building areas~ or as soon as possible in the construction process. The ground water collected in the per~orated pipes should be discharged well away ~rom the building, either into the natural drainages or into a pumped sump. The drain discharge should be protected ~rom ~reezing and the designers should be aware o~ the possibilitg that icing mag occur where the relatiYelg warm ground water is discharged. Surface Drainaae The site grading plan should be designed to direct surface water o~ the parking lot and roadway areas and away ~rom the building structure and pad. A minimum grade o~ 2 percent should be maintained in all areas. The building pad should be sloped to provide at least a 3 percent slope away ~rom the building. Building drains and gutters should discharge away ~rom the building in such a manner that erosion problems are not created. Allowances should be made ~or snow and ice build up, especially during the warm spring months and during break-up. Site Preparation Average peat depths are on the order o~ 4 ~eet. This peat in its present state is very so~t, compressible and saturated. We recommend that the peat be removed under all parking and driveway areas. Removal o~ the peat in other areas is optional. However, the stability o~ the ~ill placed on the site will be less with the peat le~t in place. Also~ the peat will settle or compress up to one-hal~ o~ its thickness. Settlement o~ the ~ill will increase maintenance costs. Excessive differential settlement could increase lateral loads and downdrag loads on the building ~oundation. 7 We recommend that the area underneath the building be graded such that a uniform slope would be created~ allowing water to drain down slope at all points. Ponding o~ water in ang o{ the excavations should not be allowed. The excavations should be sloped so that water can either run into a collection point where it can be pumped or drained bg other means~ Care should be taken not to contaminate the sandg gravel back~ill o~ the subsurface drains during the excavation and grading process. Site Fill Parking and Traffic Areas: We recommend that the top lager o¢ fill be a non-frost susceptible (NFS) sandg gravel or sand. The thickness o¢ the NFS ¢ill below the pavement will depend on the design requirements. At least 12 inches o~ NFS ~ill should be provided. I~ the traffic areas are not paved, we suggest that the one additional 6 inch lager o~ NFS sandg gravel be used as a surface lager. Additional fill below the sandg gravel surface lager to a deptb o~ 4 feet should conform to fill lgpe II in the Municipalitg e~ Anchorage specifications. These specifications allow ~or up to 10 percent silt in the fill soils. Below 4 ~eet the fill should be classified ~ill as described in the next section o~ this report. A lager o~ ~ilter fabric such as Mirafi 140 or its eEuivalent~ should be placed between the ~ill and the natural non-organic soils. The upper 4 ~eet o~ fill should be compacted to 95 percent o~ the maximum densitg as determined bg the ASTM D-1557 test method, Below 4 feet the minimum compaction reEuirement should be 90 percent o~ maximum densitg. The ~ill should be placed 12 inches in thickness and a sel~-propelled vibratorg in loose lifts not exceeding compacted uni~ormlg with compactor. Building Pad Fill: We understand that three options are being considered ~or ~illing the space between the and the natural ground. One option is to leave the space open~ Another option is to place ~ill to the elevation the bottom of the slab and use the ~ill to ~orm a structural floor slab. The third option is to bring the ~ill within approximatelg O. 0 ~eet o~ the bottom o~ the floor to create a "crawl space", With a crawl space, the fire marshall mag not require as extensive o~ a ~ire protection sgstem. The ~ill on the outside o~ the building imposes a lateral pressure on the ~ooting walls i~ spread footings with CMU foundation wails are constructed. This lateral ~orce can be resisted partialg or totallg bg ~ill on the inside o~ the footing wall. Because the structure is not supported .fl on the ~ill, the need ~or a high qualitg ~ill is not necessarg. Ne recommend, however, that a two Soot thick lager o~ clean sandg gravel be placed on the natural soil as the ~irst ~ill li~t to provide ~or drainage. The gravel should be connected hgdraulicallg with the general subsurface drainage sgstem to drain ang water collected in the gravel. We suggest that ~ill placed on the site adJacent or under the school mag be constructed oS classified soil. Classified soils, in this case, are de~i'ned as soils containing not more than 30 percent ~ines, and no organics or large boulders. The soil must have a moisture content near the optimum moisture ~or compaction and the ~ine particles (material passing the ~00 sieve) must be non-plastic. IS the moisture content o~ the soil is above the optimum moisture content (due to rain or other ~actors) it can be difficult to place and compact to the minimum reEuirements~ Placement oS this ~ill is dependent on the weather. The non-structural ~ill should be compacted to at least 90 percent o~ the maximum densitg as determined bg the ASTM D-1557 test procedures. The ~ill should be placed in lists and compacted with eEuipment appropriate ~or the tgpe o~ material. Vibratorg compactors are usuallg best Sot relativelg ~ree-draining, granular ~illJ whereas non-vibratorg compaction eEuipment is more suitable ~or compaction o~ soils containing more ~ines, Routing construction e~uipment over the Sill will reduce the amount o~ compaction reEuired. Structural Fill Ang ~ill placed under load bearing areas such as under ~ootings, slabs, or pavements is defined as structural ~ill. All ~ill placed under ~ootings should be a non-~rost susceptible sandg gravel having not more than 40 percent particles passing the 04 sieve. In unheated building areas such as entrgwags and porches, at least two ~eet oS non-Srost susceptible ~ill should be placed under the slab. A thicker NFS Sill would reduce the potential ~or ~rost heave. Additional recommendations to minimize the e~ects o~ ~rost heaving are included in the section called "Frost Protection" included a~ter the pile ~oundation recommendations. All structural ~ill under ~ootings and the top two ~eet ~ill under slabs should be placed in li~ts not exceeding inches in loose thickness and compacted to 95 percent maximum denstg as determined bg the ASTM D1557 test procedure~ Compaction and ~ill requirements in pavement and driveua~ areas were discussed previouslg in this report. Spread Footinqs Spread Footings bearing on the dense glacial soils mag be designed For an allowable bearing pressure o~ 5000 pounds per square Foot. The allowable bearing capacitg is dead and normallg applied live loads. The allowable bearing capacitg mag be increased bg one-third For inFreEuentlg applied live loads. The allowable capacity is For vertical loads applied at the ~ooting centroid. We also recommend that a compacted sandg gravel pad having a minimum thickness oF 12 inches be placed under the ~ootings to protect the bearing soils ~rom disturbance. No "bathtubs" should be created. Surface or seepage water should be allowed to drain awag From the Foundation pads. Columns extending through the ~ill would have the same downdrag loads as would the pile Foundations, Braces within the Fill should be avoided i~ at all possible. Downward loads on the braces include the weight o~ the soil above the braces plus additional Forces due to the shearing resistance oF the soil (soil to soil). The ~ootings should be protected From ~ost action i~ the a~ea above the Footing is unheated and the ~ill depth is less than 8 ~eet. F~ost protection measures include burging the Footing at a depth o~ 8 ~eet or insulating. The insulation requirements depend on the depth and dimensions o~ the Footing. To counteract ~rost heave ~orces on the column above the ~ooting~ the column should be connected to the ~ooting and reinforced so that both tension and compression loads can be transmitted. Pile Foundations I~ a deep ~oundation sgstem is the preferred alteenative~ it is recommended that steel H piles be used. The piles should be driven through the ~ill and into the glacial till soils. The glacial soils are ve~g dense. Penetration values on the orde~ o~ 100 blows pe~ Foot were ~ound, usoallg within 10 to 15 ~eet below the top oF the till surface, There~oreJ the H piles can be designed ~or an end-bearing condition. Figure 2~ shows the allowable pile capacities. These values include a Factor o~ safety o~ approximatelg two. The load imparted to the pile includes both building loads and negative Friction or downdrag loads 10 caused as the building pad Fill consolidates. As shown on Figure 23, the downdrag or negative Friction loads depend on the thickness oF the Fill. As the Fill thickness approaches 20 Feet, the downdrag loads on a tgpical pile will probablg exceed the building loads. Pile deflection For lateral loads can be calculated bg assuming that the soil has a linear, modulus oF subgrade reaction, calculated as Follows: Mh = nh (z/d) where: Kh = coeFFic, ient oF subgrade reaction (M units Force/length~) nh = coeFFicient oF subgrade reaction oF pile tip z = depth below surface d = pile width For the Fill soils a nh value oF 30 kips per cubic Foot mag be used For design. This design value should be veri2ied after the actual Fill properties have been determined. The soil against the grade beams will also provide laterml resistance to horizontal movement. The upper one Foot oF soil should be neglected in this case. An equivalent Fluid pressure oF 300 pounds per cubic Foot mag be used in passive earth pressure resistance calculations. Where more than one pile is required per column, the pile spacing should be approximatelg 2.3 times the pile width to reduce the negative skin Friction acting on the piles. The depth oF penetration into the till cannot be determined accuratelg From the information that is available. Factors that influence the depth oF penetration include pile size, pile stiffness, hammer and pile driving accessories, and oF course, soil conditions. As shown on the boring logs, at a depth oF 10 to 15 Feet below the till surface, the sampler penetration values increased up to 70 to 100 blows per Foot. This indicates that the end-bearing strata is relativelg shallow. This should, however, be verified bg driving test piles and bg conducting load tests. 11 Test Piles mhd Load Tests We recommend test piles be driven at the site and load tests conducted as soon as possible to better estimate the reEuired pile lengths and the pile driving characteristics. We recommend driving at least six test piles in addition to the piles driven ~or the load tests. Further, at least two load tests should be performed to evaluate pile capacitg and to develop pile driving criteria, such as the minimum number o~ blows per ~oot reEuired to develop the design pile capacities~ The load tests should be conducted several dags a~ter the piles are driven to allow ~or "set-up". The load tests should be performed using the procedures outlined in the ASTM D-1143 test procedure. The quick load procedure as outlined in the ASTM test procedure mag be used. The ~ill will provide some temporarg load resistance through pile-soil ~riction. For this reason, we recommend that the piles either be load tested prior to installation o~ the building pad or that the piles be isolated ~rom the ~ill bg use o~ casing or other means. Frost Protection To reduce the potential e~ects o~ ~rost heave, we recommend placing the exterior grade beams or ~ootings at least 4~ inches below the ~inished exterior grade. The exterior ~ace o~ the outside ~oundation wall should be insulated with at least two inches o2 closed-cell, extruded polgstgrene insulation, such as stgro~oam SM (blue), or eEuivalent where the bottom o~ the ~ooting is less than ~ive ~eet below the ~inished outside grade. The insulation serves two purposes: a) to direct the heat ~lowing through the slab downwards and b) to provide a bond break to prevent uplift ~orce on the grade beam or the grade beam walls. The ~toor slabs (slab-on-grade) should not be insulated adjacent to the ~oundation wall where the ~ooting depths are less than 5 ~eet. Unheated structures such as porches and entrgway slabs should not be connected structurallg to the building. Foundations supporting an unheated portion o~ the structure should extend at least 8 ~eet below the ~inal surface grade. Lateral Earth Pressures Lateral earth pressures will act on the retaining walls and on piers within the ~ill~ The magnitude o~ the earth pressure depends, in part, on the ~ualitg o~ the ~ill (densitg and grain size). We recommend that the eEuivalent ~luid pressures listed on the table below be used ~or static loading conditions. Neglect the top ~oot o~ soil in passive earth calculations. EQUIVALENT FLUID PRESSURE Sand/Siltg Sand Sandg Qravel Fill Fill (pc~) (pc~) Horizontal Back,ill Active 45 35 Passive Case 350 400 3 Horizontal to 1 Vertical Downward Slope Active Case 35 30 Passive Case 200 250 2 Horizontal to 1 Vertical Downward Slope Active Case 35 30 Passive Case 140 175 The coefficient o~ ~riction between the base o~ the ~oundation and the soil can be assumed to be 0.4. For piers the e~ective width should be taken as twice the actual width. For eartbEuake loading conditions, it can be assumed that an additional ~orce eEual to 14 H2 will be applied to the wall where H is eEual to the height o~ the wall below the ground sur~ace~ This is applicable ~or both soil tgpes. The units are pounds per ~oot width o~ wall. This ~orce should be applied at a distance o~ 0.5 H above the base o~ the retaining wall or pier and is additive to the static earth pressure. The ~actors listed above do not take into account surcharge loads such as wheel loads. It is also assumed that the wall is ~ree to rotate at least .004 times the height o~ the wall ~rom the ~ooting to the top o~ the back~ill. For rigid walls and a horizontal back2i, ll the equivalent Pluid pressure should be increased to 60 pc~ ~or sand/siltg sand ~ill and 55 pc~ ~or sandg gravel ~ill. Appropriate sa~etg {actors should be applied in o~ the wall, The earth pressures given un,motored. the design herein are 13 Subsurface drainage must be provided as recommended in this report. The retaining wall bmck~ill should be ~ree-draining and drains and/or weep holes provided, to prevent the build-up o~ hgdrostmtic ~orces behind the wall. Two inches o~ insolation behind the walls mhd provide at least 5 ~eet o~ NFS back~ill behind the wall i~ the ~ace o~ the wall is unheated. Inspection and Monitorinq All phases o~ the construction activitg involving either earthwork or placement o~ ~oundations should be monitored bg a geotechnical engineer or a technician working under the direction o~ m geotechnical engineer. Foil-time inspection is recommended during construction o~ drainage trenches and placement o~ the ~ill. Tests should be taken to veri~g the Eomlitg o~ both the ~ill and its placement. These tests should be conducted on emch li~t placed. I~ piles are driven~ ~olI-time inspection is recommended during the driving o~ test piles~ during load tests~ and during installmtion o~ the production piles. The inspector should keep a record o~ pile driving activities including blow counts. The results o~ the test driving~ load tests~ and driving records o~ the production piles should be reviewed bg a geotechnical engineer during the progress o~ the job. 14 FIELD EXPLORATION AND LABORATORY TESTIN~ Thirteen test borings were drilled at the locations shown on Figure 2. The test borings were drilled on dune 15, to dune 24, 1982, with a hollow stem auger drill rig, mounted on a Nodwell track carrier. The drill rig is owned and was operated bg Denali Drilling, Inc. The drilling operation was observed and the test holes logged bg Mr. Terrg Barber, Alaska Testlab engineering geologist. Samples were taken at approximatelg 5 Pout intervals with either a standard penetration sampler having an inside diameter uP 1.4 inches or a split spoon sampler, similar in design to the standard penetration sampler, except that the inside diameter is 2.5 inches. The standard penetration sampler was driven with a 140 pound weight ~alling a distance uP 30 inches. The larger spoon sampler was driven with a 340 pound weight Palling 30 inches. The number o~ blows required to drive the sampler a distance o~ 12 inches is shown on the test boring logs. In mang cases, it was not possible to drive the sampler the required distance. The number uP blows in this situation is indicated on the boring logs as 100+ blows per The ground water level was noted on the boring logs where it was encountered while drilling. Also, slotted pipe piezometers were placed in selected drill holes. The depth uP the slotted section is shown at the end uP the test boring log. Bentonite clag was placed above the slotted section to seal oPP water 2rom above and below the slotted section where the slotted section uP the pipe did not extend to the bottom uP the test hole~ The borings were located horizontallg and verticallg bg survegors ~rom DOWL Engineers. Deviations Prom the staked locmtions are also shown on the boring logs. The borings in the parking area and in the proposed waste water disposal site area (Boring ~13) were drilled at locations suggested bg the civil design engineer. One boring in the parking area was deleted due to the close proximitg o~ the proposed boring and Nortec Boring No. 1 drilled during the preliminarg investigation. The Nortec borings shown on Figure 2, were located either Prom taping ~o a surveged test boring location or to a surveg coordinate point. In the laboratorg, the moisture content o2 each sample was determined and the samples were visuallg classiPied. Grain size distribution tests were conducted on representative samples~ The results o~ these tests are shown on Figures 19 through 21. 10 Resistivitq Surveq Supplemental to the test boring program, an electromagnetic resistivity survey was conducted over the proposed site o~ the Qoldenview School. A resistivity survey can assist in the interpolation o~ shallow (0-15 ~eet) soil conditions between test borings, and can o~ten identi~g anomalous zones within a site such as permafrost or buried pipes. A contour map o~ apparent resistivity values also provides a ~airlg good representation o~ the spacial distribution o~ shallow soil types and/or water table conditions across the site. The resistivity survey was conducted using a Qeonics EM-31 Terrain Conductivity Meter. This instrument measures the apparent conductivity o~ the ground by utilizing the principals o~ magnetic induction, and its depth o~ investigation is approximately 15 to 20 ~eet. A grid o~ survey stakes at 50 ~eet intervals was laid out over the school building ~ootprint on dune 20, 1~82~ and th~ EM-31 survey was conducted on June 21, bg Mr. Tom Williams and Ms. dan Mulder, geologists with Alaska Testlab. Readings were taken every 25 ~eet within the grid established over the proposed building ~ootprint. The actual building location was subseRuentlg shifted east o~ the original proposal, but the maJority o~ the ~ootprint lies within the resistivity survey boundaries. The terrain conductivity readings (in millimhos per meter) were converted to apparent resistivity values (in ohm-meters) and the results are presented in a contour map in Figure 24. The terrain across the survey site consists o~ several iow marshy areas contrasted bg small morainal mound ~eatures that are 5-10 ~eet higher. The soils distribution across the site as seen in the many borings is consistent: 3 to 5 ~eet o~ peat underlain bg dense glacial till. These soil conditions provide a ~airly ~lat resistivity background, so that the apparent resistivity contours are principally reflective o~ soil moisture conditions. The resistivity map contains several contrasting zones. The major ~eature (shaded on the apparent resistivity map) is a large zone o~ low resistivity (50 - 75 ohm-meters) through the center o~ the survey site. This is interpreted as an area o~ high ground water levels, at or near the surface, and corresponds to ~ield observations o~ a marshy area o~ low topography. Several higher resistivity anomalies, 125 to 150 ohm-meters, correlate with the 16 morainal mounds, which with higher retieP are better drained than surrounding areas. These areas can be wet at the sur~ace~ doe to mater perched in the peat, whereas the actual piezometric water level is several ~eet below the 17 Huffman Rd i DeArmoun Rd 144TH TWILIGHT LN MANYTELL Rabbi Creek '" PROJECT LOCATION E TH. AVE GOLDEN VIEW VICINITY MAP ELEMENTARY SCHOOL FIGURE 0% · LTEEGsETNBRoRINGS B~f DOWL ENGINEERS, dUNE 1982 (~ TE~T BORINGS BY 'NORTECH, OCTOBER 1981. ' ~- GENE'RALIZE~ S~BSURFACE, CROSS-SECTIONS: ~T ~A~IAI~ ~ (SEE FIGURES 3 4, ~ 5} ' ~ · t~/ .o~: ' ' - ~OL~E~' view I. TEST BORINB$ LOCATED 8Y DOWL ENGINEERS SURVEY, FB.?~3~I. · 2. MT TEST BO~INGSLOB~TIONS ~E ~PPROXIM~TE. ' TH-9 TH-2 TH -5 / \ TH-I~ ITl m rtl 0 0 0 ~ o ~ ~ o 0 0 0 0 o 0 o o TH -9 rtl m I'rl (n fi) TH-8 ELEVATION (FEET) 0 0 0 0 0 o ~ 0 0 0 TH-~3 m.--I rrl · -t '--I m -< r- ..<~z FRIED ~'-'1 ~"'r ~ o ~ 0 0 0 TH-2 TH-I (FIG 19) TEST BORING ELEVATION= 607 'F-4, dark Brown Peat, fibrous, saturated, soft F-4, Grey Sandy Silt, interlayered with clean sand, s~, soft F-l/F-2, Grey Silty Gravelly Sand'~ith occasional cobbles and boulders to 12" diameter, 20-40% fine or coarse gravel, 15-30% non- p!asisilt, subrounded to subangular particles, moist~~ ~ery dense, (glacial till) DEPTH 3.0' 4.5I KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) [TSF) TV : SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS EL = LIQUID LIMIT PI · PLASTIC INDEX [] = 2.5" I.D. SPOON SAMPLe:, 540,$'-.WEIGHT, :50"FALt. [] = G~ SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ '- C~OUND WATER TABLE WHILE DRILLING LOG OF BORING LOGGED BY TB W.O. NO. 013965 FIC~ 6 7.6 TEST BORING I cont'd. ELEVATION= 607.:' DEPTH F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangutar parttcles, moist~-uery dense, 38.0' NFS/F-2, Brown Sand, fine with sandy silt seams, moist, very dense 15.4 V Ground Water Level, June 28, 1982 .~ Sand becomes coarser MA (FIG 21) 21.8 B7 Test Boring ~ompleted June 23, 1982 Piezometer Installed, Slotted at 39' to 49', Sealed with Bentonite Above 39' 51.0' KEY PP -- UNCONFINED COMPRESSIVE ~TRENGTH (PENETROMETER) (TSF) 'iA/ = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI :: PtASTIC INDEX [] = 2.5" I.D. SPOON SAMPLE, 340# WEIGHT, ~O"FALL [] -' GRAB SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ -' GROUND WATER TABLE WHILE DRILLING LOG OF BORING I' L ] DEPTH F-4, dark Brown Peat, fibrous, saturated, soft ~o'~d Wa~er~evel While Drilllnq (Perched) ' F-4 organic Sandy Silt.' F~I/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles, moist, very dense, (glacial till) 2o5w KEY PP = UNCONFINED COMPRESSIVE S~RENGTH (PENETROMETER) (TSF) TV = SHEAR ST~NGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT Pi · PLASTIC INDEX [] = 2.§"LD. SPOON SAMPLE, 340# ~EIGHT, ~O"FALL [] = GR~B SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ = GROUND WATER TABLE WHILE DRILLING . LOG OF BORING, ¥~O. NO D13965 F~C-~RE 7 I ' TEST BORING ELEVATION= 606.9 2 contel. DEPTH ;round Water Level While Drilling F-2, interlayered Silty Sand, (fine), and Sandy Silt, (non-plastic~,~aturated, dense 42.0' 51.5' KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS · Lt. = LIQUID LIMIT PI = PLASTIC iNDEX ~ = 2.5"1.D. SPOON SAMPLE, ~10# WEIGHT= ~O"FALL [] = GRAB SAMPLE [] = SPT SAMPLE [] '- SHELBY TUBE-PUSHED ~ = C~OUNO WATER TABLE WHILE DRILLING LOG OF BORING FIC4JRE TEST BORING ELI[VAT[ON= ~05.2 F-4, dark Brown Peat, fibrous, saturated, soft F-4, organic Silt F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangular particles, satura~d, .~edlum dense, (glacial till) ~ ...... Grades to very dense, moist DEPTH S.OI KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) {TSF) TV = SHEAR STRENGTH (TORVANE} (TSF) MA = MECHkNICAL ANALYSIS LL : LiQUiD LIMIT PI = PLASTIC INDl[X [] = 2.5" LD. SPOON SAMPLE, 340;~ WEIGHT, ~O"FALL [] = GF~B SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ = GROUND WATER TABLE WHILE DRILLING LOG OF BORING 12.1 3 cont%l. OEPTH 38.0' Test Boring Completed June 18, 1982 Hollow Stem Auger Broke on Cobble KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) {TSF) [~ =, GPJ~B SAMPLE LOG OF BORING TEST BORING ELEVATION: 616 ...... ............ ~,~, Water Level While Dr±lllng ,,"': DEPTH F-4, Grey Sandy Silt with-organics and roots, loose 5.0~ F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameeter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles,/moist, very dense, (glacial till) 7.0t Cobbles at 27-33' Test Boring Completed June 23, 1982 33.5' KEY PP = UNCONFINED COMPRESSIVE STRENGTH {PENETROMETER) (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS Lt- = LIQUID UMIT Pi · PLASTIC INDEX [] = ~.B" I.D. SPOON SAMPLE, ~,40# WEIGHT~ ~O"FALL r-1 = GR/~ SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ = GROUND WATER T.'~BLE WHILE DRILLING LOG OF BORING TEST BORING 5 ELEVATION= 61 6.5 DEPTH F-4, dark Brown Peat, fibroust saturated, soft Ground Water Level While ~i'~.~ NFS, Grey to Black Gravelly Sand, angular to subrounded 1" gravel, saturated, loose 3.0~ (FIG 19) F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles, moist, very dense, (glacial till) ~ X ~ CONT'D. KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI = PLASTIC INDEX [] = 2.5" I.D. SPOON SAMPLE, 340# WEIGHT, ~O"FALL [] = GRAB SAMPLE [~ = SPT SAMPLE [] : SHELBY TUBE-PUSHED ~ = GROUND WATER TABLE WHILE DRILLING LOG OF BORING TB LOGGED E¢¢ V~O. NO. D13965 F'] GORE 10 TEST BORING 5 conf'd. ELEVATION = 616 o 5 DEPTH F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangular particles, moist, very dense, (glacial till) Numerous cobbles 34-38' 78 Test Boring Completed June 22, 1982 KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) (TSF) TV : SHEAR STRE. NGTH (TORVANE) (TSF) MA: MECHANICAL ANALYSIS Lt. = LIQUID LIMIT Pi : PLASTIC INOEX [] = 2.5"1.0. SPOON SAMPLE, 340# WEIGHT, 30"FALL [] = GRAB SAMPLE [~ = SPT SAMPLE [] : SHELBY TUBE-PUSHEO ~ -- GROUND WATER TABLE WHILE DRILLING LOG OF BORING 41.5' TEST BORING ELEVATION: 613.1 6 DEPTH ~A FIG 20) 100~ F-4, dark Brown Peat, fibrous, saturated, soft F-l/F-2; Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to suban~ular particles, saturated, medium dense, (glacial till) Grades very dense, moist Test Boring Completed June 17, 1982 3.0I 30.5' KEY PP = UNCONFINED COMPBESSIVE STRENGTH (PENETROMETER} (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI = PLASTIC INDEX [] = 2.5" I.D. SPOON SAMPLE~ 540# WEIGHT, 50"FALL [] = 8RA~ SAMPLE I~ = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ -- GROUND WATER T~LE WHILE DRILLING LOG OF BORING LOGGED BY TR WO, NO. D13965 FIGLrRE 1 I I, ~ ~ EL£VATION; 616.1 DEPTH F-4, dark Brown ~eat, fibrous, saturated, soft 3.0I F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangular particles, saturated, medium dense Grades very dens~ (FIG 20) ~-' .~ ~ CONT'D. KEY PP = UNCONFINED COMPRESSIVE STRENGTH {PENETROMIET£R) (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS Lt. : LIQUID LIMIT Pi · PLASTIC INDEX [] : Z.5" I.D. SPOON SAMPLE, 340# WEIGHT, 50"FALL [] = GF~) SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ = GROUND WATER TABLE WHILE DRILLING LOG OF BORING LOGGED BY TB V~O. NO. D13965 FIC4JRE 12 TEST BORING 7 contel. ELEVATION= 616.1 DEPTN 36.0' Interlayered NFS, Grey Sand and F-2, Brown Silty Sand, fine to medium, saturated, very dense Test Boring Completed June 16, 1982 41.5' KEY Pp = UNCONFINED COMPRESSIVE SI'RENGTH (PENEI'ROMETER) (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI = PLASTIC INDEX [] = SFT SAMPLE LOG OF BORING LOGGED BY TB W.O. NO D13965 TEST BORING ELEVATION-' 622 F-4, dark Brown Peat, fibrous, saturated, soft DEPTH F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles, §aturated, medium dense, (glacial t~ll) Grades very dense Ground Water Level While Drilling (6/28/82) 3o0m Test Boring Completed June 24, 1982 Slotted Pipe Piezometer Installed PiPe Slotted from 3' to 19.5' Depth and Sealed with Bentonite at 3' 20.5' KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) (TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS - LL = LIQUID LIMIT Pi '= PLASTIC INDEX [] = 2.§" I.D. SPOON SAMPLE, 340# WEIGNT~ 30"FALL [] = GRAB SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE- PUSHEO ~ -' GROUND WATER TABLE WHILE ORILLING LOG OF BORING BO.,'NG ELEVATION-- 623 Ground Water Level While Drilling F-4, dark Brown Pea%, fibrous, saturated, soft DEPTH F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangular particles, saturated, medium dense, (glacial till) Grades very dense, moist Water Seepage While Drilling.' Auger broken on cobble at 25' Test Boring Completed June 21, 1982 25.0' KEY . pP = UNCONFINED COMPHESSIVE STRENGTH (PENETROMETER) [TSF) TV = SHEAR STFU~NGTH (TORVANE) {TSF} MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI = PLASTIC INDEX [] = 2.§" I.D. SPOON SAMPLE, 340# WEIGHT, 50"FALL [] = GRAB SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~[~ = G/:~OUND WATER TAgLE WHILE DRILLING LOG OF BORING LO CC-E D BY TB W.O. NO. D13965 FIGLiRE 14 I0 F-4, dark Brown Peat, fibrous, saturated, soft Brown to Grey Sandy Organic Silt F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles, sa~t~, medium dense, (glacial till) -"~. ...... ' Interlayered with silts and clean gravelly sand, 10-72' depth Grades very dense KEY PP = UNCONFINED COMPRESSIVE S~RENGTH (PENETROMETER) (TSF) TV = SHEAR STRENGTH (]'ORVANE) (TSF) MA = MECH~%NICAL ANALYSIS LL : LIQUID LIMIT Pi ~: PLASTIC INDEX [] = 2.5" I.D. SPOON SAMPLE, ~,40# WEIGHT, ~O"FALL D = Gl:~aB SAMPLE [] = SPT S~MPLE [] = SHELBY TUBE-PUSHED ~ = GROUND WATER TABLE WHILE DRILLING DEPTH 4o5I CONT'D. LOG OF BORING LO CGED BY TB ',~O. NO D13965 F~C43~E 15 TEST 80RING IOconf l. ELEVATIONTM 622.3 DEPTH F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles, moist, ~ery dense, (glacial till) 49.5' Test Boring Completed June 17, 1982 KEY PP = UNCONFINED COMPRESSIVE STRENGTH (PENETROMETER) (TSF) TV = SHE~ STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI = PLASTIC INDEX [] = 2.5" I.[1 SPOON SAMPLE, 540# WEIGHT~ 50"FALL C] = GRAB SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE~- PUSHED ~ = GROUND WATER TABLE WHILE DRILLING . LOG OF BORING LOGGFD I~Y TB W.O. NO. D13965 TEST BORING II ELEVATION= 6i9.8 DEPTH F-4, dark Brown Peat, fibrous, saturated, soft Ground Water Level While Drilling (6/28/82) F-4, Blue-Grey Gravelly sand F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangular particles, saturated, medium dense, (glacial till) Grades very dense' Test Boring terminated at 10', moved 6' SW and redrilled hole 3o0t (FIG 20) Test Boring Completed June 15, 1982 Slotted Pipe Piezometer Installed Pipe Slotted Between 20 and 30 Foot Depth Bentonite Seal P~aced at 4.5 Foot Depth 30.8' KEY pp = UNCONFINED COMPRESSIVE STRENGTH (PENETROM~TER) {TSF) TV = SHEAR STRENGTH (TORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT PI = PLASTIC INDEX [] = GRAB SAMPLE [] = SPT SAMPLE [] = SHELBY TUBE-PUSHED ~ -' G,9OUND WATER TABLE WHILE DRILLING LOG OF BORING LOGGED BY TB FIGURE I 6 g TEST BORING 12 ~ Ground Water Level While Drilling F-4, dark Brown Peat, fibrous, saturated, soft F-l/F-2, Grey silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, sub- rounded to subangular particles, saturated, very dense, (glacial till) Ground Water. Level While Drilling (6/28/82) DEPTH Test Boring Completed June 14, 1982 Slotted Pipe Piezometer Installed and · Sealed with Benzonite at 5.7' 5.7~ 19.0' KEY pP = UNCONFINED COMPRESSAtE 5-TRENGTH (PENETROMETER) (TSF) TV = SHEAR STRENGTH (~ORVANE) (TSF) MA = MECHANICAL ANALYSIS LL = LIQUID LIMIT Pi = PLASTIC INDEX ~ = 2.5" I.D. SPOON SAMPLE,'3,40# WEIGHT~ 30"FALL [] = GRAB SAMPLE [] · SPT SAMPLE [] = SHELBY TUBE-PUSHEB ~ = GROUND WATER TABLE WHILE DRILLING LOG OF BORING TB LOGGED BY WO. NO. D13965 FIGURE 17 TEST BORING ELEV~ION: 598.5 · F-4, dark Brown Peat, fibrous, saturated, soft DEPTH F-l/F-2, Grey Silty Gravelly Sand with occasional cobbles and boulders to 12" diameter, 20-40% fine to coarse gravel, 15-30% non-plastic silt, subrounded to subangular particles, moist, very dense, (glacial till) 3.5I F-4, Grey Sandy Silt, non-plastic, very hard, (glacial till) Test Boring Completed June 24, 1982 20.0' 22.0' KEY PP = UNCONFINED COMPRESS~E STRENGTH (PENETROMETER) (TSF) TV : SHEAR STRENGTH (TORVANE) (TSF) MA: MECHANICAL ANALYSIS ti.. = LIQUID LIMIT Pi = PLASTIC INDEX [] = 2.5"1.D. SPOON SAMPLE, 340# WEIGHT~ ~O"FALL [] = GRAB SAMPLE ~ = SPT SAMPLE ~ = SHELBY TUBE- PUSHED ~ = C~OUND WATER TABLE WHILE DRILLING LOG OF BORING LOGGED ~Y 'PR WO. NO. D13965 Z 0 W Z 0 Z N ±H913~ A8 W3NIJ iN30 0 0 I0- £0- 30- 4O ALLOWABLE 20 40 '~ I ' ! END BEARIN~ CAPAC~-rY 6,0 8,0 MINIMUM EMBEDMENT = 15' NOTES: 1. Effective pile tip area = web x flange depth. 2. Downdrag loads must be subtracted from allowable pile loads. 3. Values shown are for planning purposes only. Actual allowable loads should be determined after driving of test piles and/or load tests. ALLOWABLE PILE END BEARING H CAPACITY PILES FIGURE 0 ~EGATIVE SKI" F~IOTION (TONS~FT ~) 20' 25- NOTE: 1. Graph is for steel H piles. 2. For total downdrag load multiply value shown on graph by the effective pile area per foot of pile. 3. Effective pile area = Perimeter = 2x(web + flange) NEGATIVE SKIN FRICTION DUE TO FILL CONSOLIDATION FIGURE C APPENDIX RECONNAISSANCE INVESTIGATION PROPOSED GOLDENVIEW ELEMENTARY SCHOOL For Municipality of Anchorage Physical Planning Department by Northern Technical Services November, 1981 INTRODUCTION In this report we present the results of a reconnaissance investigation of an area adjacent to Mercedes Drive near Rabbit Creek Road. The site of our investigation is described as Site 1 in the Golden View Elementary School Alternative School Site Study draft report dated August, 1981, prepared by the Municipal 'Planning Department. The site is shown on Figure 1, Location Map. The purpose of our investigation was to determine site suitability for construction of a one-story elementary school which would have an enrollment of 400 to 600 students. We understand that on-site sewage disposal and water supply are planned for the facility. [ ] The scope of our investigation included determining capability of site soils for: o Support of a one-story, wood-frame structure, and o Absorption of on-site sewage effluents. In addition we were to determine the tendency for soils problems such as: o Excessive shrink-swell o Instability o Frost heave, and o Seepage Ground-water level and potential for developing an on-site water supply also were to be determined as part of this investigation. Our participation on the project was verbally authorized by Mr. Brnce Phelps during a meeting on October 28, 1981. SOIL RECONNAISSANCE INVESTIGATION Investigation of the site soils included a visual surface inspection. In addition five test borings were drilled at the locations shown on Figure 2, Test Boring Location Map. Con- tinuous logs of subsurface conditions encountered during test boring are presented on Figures 3 through 7. Laboratory tests were performed on selected samples to determine soil characteristics and to confirm field classifications of soil type. The laboratory test results are shown on Figures 8 through 10, Laboratory Test Results. The following site soil descriptions summarizes information obtained during the test boring program and subsequent laboratory testing of soil samples. SOILS The ground surface at the site is covered by spruce and alders with a two to three foot thick mat of organic material including live vegetation and organic debris. Beneath this organic mat lies glacial till consisting of sandy gravel and silty sand layers with gravel and cobbles. Occassionai three to five foot thick layers of sand occur between glacial till layers and, in some areas, immediately beneath the organic material. These sand layers are probably glacial outwash deposits and are of limited aerial extent. The outwash layers are rated non-frost susceptible (NFS) as defined by the Corps of Engineers Soil Classification System. The glacial till sands are rated slightly frost susceptible (F2) according to the Corps of En- gineers Soil Classification System. Glacial till occurs to a depth of at least 16 feet below ground level at all five test boring locations. Bedrock was not en- countered in any of the five test borings. GROUND WATER Near surface ground water was encountered at all five test boring locations. A perched water table exists at the Test Boring-1 and 2 locations. Beneath the perched water table and at the other three test boring locations, the water table is from two to nine and one-half feet below ground level. All water level measurements were made immediately upon completion of drilling each test boring. WATER SUPPLY ~o water well data are available which are specific to the site. In order to determine the possibility of developing an on-site water supply we surveyed home owners having wells near the site. The survey was made by personal interview and by questionnaire. In this effort, we contacted 19 individuals with property adjacent to the site or within 2,000 feet of the site. A summary of our survey results yielded the following: o Three wells with information on total depth and yield. o Two wells with approximate total depth and approximate yield. o Five wells with known or approximate depth only. o Eight wells with either no information or no response. o One well where the owner tore up the questionnaire. Based on the survey of wells, we found total well depths ranged from about 30 feet to 320 ~eet below ground surface. Most wells were from 50 to 125 feet deep. Water yields ranged from just enough to sustain a single residence to 35 gallons per minute However, because of the usual short-term pumping test used to determine well yields we do not consider the reported well yields totally reliable. Water well records and subdivision information on file with the Municipality of Anchorage were reviewed to obtain additional water supply data for wells in the general vicinity of the site. These sources indicate typical well depths of about 125 feet with water yields of about 16 gallons per minute. Again, water yields reported are questionable because of typically short pumping tests used to obtain the recorded values. CONCLUSIONS The following conclusions are based on the results of our reconnaissance investigation. It should be understood that valuable basic site information has been obtained as a result of our reconnaissance investigation. However, additional soils and hydrologic testing are required to verify preliminary -conclusions presented in this report. SOILS AND FOUNDATIONS CONDITIONS The silty gravelly sands beneath the site are glacial till and glacial outwash deposits. These soils should provide adequate support for one-story structures on properly designed foundations. The generally granular soils contain less than 20 percent fine-grained materials and are only slightly frost susceptible. (U.S. Corps of Engineers ratings of NFS or F2). Soil grain size distribution indicates the soils are relatively impermeable although capable of absorbing sewage effluent at rates suitable for limited on-site disposal. Shrink and swell characteristics of soils are generally associted with clay content. Field examination did not indicate the presence of significant clay content. We do not anticipate that shrinkage or swelling of soils encountered during the investigation will present problems at this site. The soils appear to be stable throughout the site because: 1. Site soils are dense and generally granular. 2. Only traces of organic materials occur in the granular soils. 3. Site topography is relatively level with only gradual slopes. The presence of dense granular soils, even with high water table conditions, tend to be relatively stable during seismic shaking. Site topography is relatively level with slopes generally less than 10 percent. Dense granular soils and relatively flat slopes combine to provide stable soil conditions throughout the site. ON-SITE SEWAGE DISPOSAL Disposal of sewage effluents on-site will require careful planning and special consideration. Disposal of sewage effluents beneath the site will be complicated by lack of permeability in the granular soils and high water table conditions. Municipal regulations dealing with on-site sewage require thaf effluent leaching structures be located not less than four feet above the water table. The water table is generally less than nine feet below the ground surface along the eastern one-half of the site. Therefore, leaching trenches or fields designed to dispose of sewage effluents on-site would have to be less than five feet deep along that part of the site. Throughout most of the western one-half of the site the water table is less than four feet below the ground surface. Therefore on-site disposal of sewage effluents would require using techniques such as "mounding" with permeable fill to increase depth to the water table. Seepage of ground water probably occurs on the western edge of the site during periods of high water table conditions. While the water table was relatively high at the time of our investigation, even higher water table conditions may occur during spring break-up and after prolonged periods of heavy rain. Use of the western portion of the site for buildings, playgrounds or parking may require placement of fill to increase ground elevations in topographically low areas. WATER SUPPLY A properly designed well or wells may be capable of supplying sufficient water to meet the short- and long-term needs of the proposed school. Total well depths and apparent water yields for existing wells vary considerably throughout the area surrounding.the site. It appears unlikely that a well(s) alone -can provide water at a sufficient rate to meet water supply needs during periods of peak use. Therefore a water supply system designed to fulfill proposed school needs may require that substantial water storage be included in the supply development. Water storage requirements will be dependant upon actual yields f~om on-site water supply well(s). RECOMMENDATIONS Our recommendations for additional investigation of this site are made with the assumption that the Municipality of Anchorage is interested in continuing their consideration for development of the site. As discussed in the Conclusions section of this report, there are several specific areas of concern which would require mor~ detailed investigation to determine construction at the site. Our recommendations are and operation suitability as follows: o A building location should be selected near the northeast corner of the site. o A detailed soils investigation should be conducted to develop input values for foundation design at the selected building location. o A topographic map should be prepared to show site contours at two to five foot invervals. o A test well should be drilled to confirm specific water supply capability at the site. o The test well should be registered with the State of Alaska, Department of Natural Resources. Because of the limited potential for on-site sewage effluent disposal, we recommend the Municipality of Anchorage consider the following procedures. Gray water, including drinkin9 fountains and wash basins, should be plumbed so that effluents from these facilities can be disposed of on-site. The remaining sewage effluents should be stored for periodic disposal by vacuum trucks as needed. F ©i-IORAGE~' 0 ~ 4 6 8 I0 S~.I'F:' I1'~ MfLES LOC~TI~ Ol~ MAP Figure SITE BOUNDARY O 100 200 ;;500 400 SCALE IN FEET TEST BORING LOCATION MAP A LOG OF BORi,,G NO. 1 DATE: ~O-i LOCATION: GOLDEN VIEW ELEME TYPE OF BORING: AUGER COMPLETION DEPTH: 16 ft. DEPTH OF WATER: PERCHED O ~ STANDARD ~- ~~.~ SOIL DESCRIPTION T] ~ ~ ~ Blows ~ ~ 0 15 3~ 45 6 0 Bork Brown ~[brous Or~onics~ So~uro~ed~ Sof~ 5 SM ~ ~ Blueish Gray Silty Sand w/ some Gravel, m~:'~' J ~ ~7~lastic silt, fine to coarse grained~ J ~ moist,~dense (glacial till) J more gravel, some cobbles,~ I0 ] GradeSless silt,W/very dense by 7 ft. J -20- Test Borin~ Completed 10-1~-81 , k 25- 30- -50- .; Figure EMENTARY SITE #1 ft. W.D. 7 ft. PENETRATION r )er Foot 60 75 90 105 120135 150 Figure 4. LOG OF BORt,.G NO. 2 DATE: IO-i LOCATION: GOLDEN VIEW ELEMENTARY SITE TYPE OF BORING: AUGER COMPLETION DEPTH: 16.5 ft. DEPTH OF WATER: PERCHED 5 ft. W.D. 8 ft. .~ STANDARD PENETRATION ~ ~ ~.~ SOIL DESCRIPTION TEST ~ ~ i :~ Blows per Foot ~ ~ i ~ o ~5 30 45 6o75 9o lo512o)35 150 0 Dark Brown Organics, Saturated, Soft 5- ] Blueish Gray Gravelly Silty Sond~ ~ ~ " non-plastic silt, fine ~o coarse, ~ wet, medium dense (glacial tilt) ~ )0 ~ Grades w/ less silt, more grave~, SM w/ cobbles & very dense at 9 ft., Boulder ~12in. at 12 Test Boring Completed 10-19-81 - 20- - 25- - 30- - 35 - -40 - -45~ Figure ,5. LOG OF BORI,.G NO. 3 DATE:IO-Ii, LOCATION: GOLOEN VIEW ELEMENTARY SITE #l TYPE OF BORING: AUGER COMPLETION DEPTH] 16.5 ft. DEPTH OF WATER: PERCHED -- W.D. 2 ft. SOIL DESCRIPTION Dark Brown Organics, Soft, Saturated Brown Very Gravelly Sand w~,s.ome...si.ltL occasional cobbles, Gray Silty Gravelly Sand w/ occasional cobbies & sand Ioyers,Qwet, very dens6 ~,~ ( g ia c i a i-'~,ji:~) ................ Test Boring Completed I0- 19-81 STANDARD PENETRATION TEST Blows per Foot 0 15 :~0 45 ~,0 75 90 los 120J3.s I.so ..... ...................... i:lgure ~,. LOG OF BORt..G NO. 4 DATE: ,O LOCATION: GOLDEN VIEW ELEMENTARY SITE TYPE OF BORING: AUGER COMPLETION DEPTH: 16.5 ft. DEPTH OF WATER: PERCHED - W.D. 4 ft. ;STANDARD PENETRATION ~ 0 ,,.~ SOIL DESCRIPTION TEST =:' ~ ~ Blows per Foot ~ > ~ 0 15 30 45 607590 105120135 150 0 Dark Brown Organics, Saturated, Soft Blueish Gray Silty Gravelly Sand 5- ~ non-plastic silt, sand fine to coarse, SM ~ occasional cobbles, very dense (glacial till) 10 Gray Sa~d, Fine to Coarse, SP ~--~'a'l~F'G~'~;~dense ( outwash sand ) Gray Silty Gravelly Sand~ , non-plastic slJt~ grav~'~salurated Test Boring Completed 10-19-81 - 20- - 25- - 30- - 35 - -40 - - 45- -50~ Figure 7. LOG OF BORt,.G NO. 5 DATE: LOCAT,ON: GOLDEN V,EW TYPE OF BORING: AUGER COMPLETION DEPTH: 16.5 ~L DEPTH OF WATER: PERCHED - W.D. 9.Sft ~STANDARD PENETRATION ~ ~ ~ ~ SOIL DESCRIPTION TEST ~ ~ ~ Blows per Foot ~ ~ ~ 0 15 3g 45 60 75 90 105120~5 150 0 Brown Organics Brown Sandy GraveJ w/ trace silt -- ~- SW ~ & silt layers~ coarse sand, rounded particles~ moist, very dense (glacial outwash) Gray Silty Gravelly Sand~ SM sa~ura~ed~ very dense (glacial till) Test Boring Completed - 25- - 30- - 35 - -40 - -50- g ._.1 I >- Q:: 0 0 UJ 0 < L ~ [~ I I I LJ I ~ , t~.l.__l-hJ o ~ n~ 0 O ~ >o Test Hole Log - Description Guide ~those samples receive an independent textural classification in the laboratory ' ~to verify the field examination. ~The logs often include the following items: Depth Interval - usually shown to 0.1 foot, within that zone no significant change in soil type was observed through drill action, direct observation or sampling. Frost Classification - NFS, Fl, F2, F3, F4, see "Soft Classification Chart" Texture of Soil An engineering classification of the soils by particle s:ze and proportion, see "Soil Classification Chart", note the proportions are approximate and modifications to the soil group due to stratification, inclusions and changes in properties are included. d~. no or little apparent surface moisture, damp. moisture forms portion of color, less than plastic limit, wet. no free water, often soft, if cohesive soil, saturated, free water may be squeezed out, ifa free draining soil; dilatent at natural moisture content, if a non-plastic silt or fine sand. (The moisture content is further definedby reference to PI, LW, NP. M%or dftatency.} Density - refers to more or-less non-cohesive soils, such as sand gravel mixtures with or without a fine fraction, derived from drilling action and/or sample data; usually described as: very loose, loose, medium dense, very dense. General intent is to portray earthwork ch~ract er;st;cs. stiffness - refers to more-or less cohesive soils and fine grained silts of the clay-sftt groups. Derived from drill action and/or sample data. Very soft, soft, stiff, very stiffand hard are commonly used terms. Particle size -- The largest particle recovered by the split spoon is 1-3/8", Shelby tube 3", auger flights (minute-man} 2", Auger flights (B-50 hollow stemJ 6'-8". Larger particles are described indirectly by action of the drftling and are referred to as cobbles, 3" to 8", or boulders 8"+. Therefore when reviewing the gradation sheets, if any, the description on the hole log must be considered for an:indication of larger particles; Unified Soft Classification - This is a two letter code. See Unified Classification sheet for further definition. In some cases AASHO and/or FAA soft classifications may be shown a5 well as the unified. Atterberg Limits useful for fine grained and other plastic softs, PI; natural mmsture content beheved to be less than plastic L{mlt PI+; natural moisture content believed to be between plastic and liquid limits L~; natural moisttue content believed to be greater than liquid limit N~P; non-plastic, useful as a modifying description of some silty mater;ah. Dilatency - is the ability of water to migrate to the surface of a saturated or nearly saturated soll sample when vibrated or jolted - u~ed as an aid to determine ifa fine grained soL] i$ g slightly or non-pl~tic silt or a volcanic ash, Rock flour -- finely ground soft that is not plastic but otherwise appears similar to~ clayey silt. Organic Content -- usually described as Peat, PT. sometimes includes discrete particles such as wood, coal, etc. as a modifier to an inorganic soil. Quantity described as; trace, or an estimate of volume, or, in case of all organic, - as Peat. This may include tundra, muskeg and bog material. Muck -- a modifier used to describe very soft, semi-organic deposits usually occuring below a peat deposit, Amorphus peat -- organic particles nearly or fully disintegrated. Fibrous Peat -- organic particles more-or less intact. Bottom of Testhole includes last sample interval. Frost Line - seasonal frost depth as described by drilling action and/or samples at the time of drftling. Frozen Ground -- other than frost line, described by samples, usually includes description of ice content, often will include modified Unified Classification for fiozen soils this is a special case related to permafrost studies. Free Water Level -- The free water level noted during drilling. This is not necessarily the static water table at the time of drilling or at other seasons. Static water table determination in other than very permeable soils requires observation wells or piezometer installations, used only in special cases, Blow/6" - The number of blows of a 140 weight free falling 30" to advance a 2" split spoon 6"; the number of blows for a 12" advance is. by definition, the standard penetration. M% - natural moisture content of the soil sample, usually not ~orrned ou dean sands or gravels below the water table. Type of Sample S__P, refers to 2" split spoon driven into the soil by 140 pound weight, a disturbed sample, ~S, thin wall tube, "Shelby" used to obtain undisturbed samples of fine grained soil, G, "grab" disturbed sample from auger flights or wall of trench, .~, cut sample, undisturbed sample from wall of trench. Dr}' Strength - a useful indicator of a soil's clayey fraction, N-None, L=Low, M=Medium, H=Nigh Group - The samples are placed into apparently similar groups based on color and texture and are arbitrarily assigned a group letter. Further disturbed tests including Atterberg Limits, grain size, moisture<lensity relationship, etc. may be performed on the group and are assumed to reflect the general distrubed characteristics of the soils assigned to the group. This is an important phase of the soil analysis and is u,ed to standardize the various qualitative determinations and to reduce the number of qpantitative te$ts necessary to dgscribe tl~e soil man. TEXTURAL SOIL CLASSIFICATION CHART GRAVEL 30% CLAY CLAYE CLAYE~ OR SILT'~ ~ SILT SAND GRAVEL GRAVELLY SAND GRAVEL 0 I0 20 :50 40 50 60 70 80 90 I00 GRAVEL (+ ~4 SCREEN) % BY WEIGHT FROST CLASSIFICATION SYSTEM NONFROST SUSCEPTIBLE SOILS ARE INORGANIC SOILS CONTAINING LESS THAN 3% FINER THAN 0.02 mm. GROUPS OF FROST-SUSCEPTIBLE SOILS: FI GRAVELLY SOILS CONTAINING BETWEEN 3 AND 20% FINER THAN 0.02 mm. F2 SANDY SOILS CONTAINING BETWEEN 3 AND 15% FINER THAN 0.02 mm. F3 a. GRAVELLY SOILS CONTAINING MORE THAN 20% FINER THAN 0.02 mm. AND SANDY SOILS (EXCEPT FINE SILTY, SANDS) CONTAINING MORE THAN 15% FINER THAN 0.02 mm, b. CLAYS WITH PLASTICITY INDEXES OF MORE THAN 12. EXCEPT VARVED CLAYS. F4 a. ALL SILTS INCLUDING SANDY SILTS. b. FINE SILTY SANDS CONTAINING MORE THAN 15% FINER THAN 0.02 mm. c. LEAN CLAYS WITH PLASTICITY INDEXES OF LESS THAN 12, d. VARVED CLAYS.