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Home My WebLink AboutCOVENTRY SUBDIVISION PRELIMINARY - 80 93 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTSWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure ►i 10000 SAMPLE OF <;1,Sauv-11 G,,p,f FROM TEST HOLE NO. Ia AT DEPTH OF 2 -3 FEET NATURAL MOISTURE CONTENT I9,Z y, NATURAL DRY DENSITY Z FCF zv 0 m n 0 J .J J W v3i 4 2. 0. `7 SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure SAMPLE OF Sa+tr GAo,-( FROM TEST HOLE NO._.17 AT DEPTH OF g> FEET NATURAL MOISTURE CONTENT �r� C % NATURAL DRY DENSITY 10000 Ilb.o PCF o m c� 00 J J W 4 2. 0. 6\ `j SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure 10000 SAMPLE OF Suc'K'fol4i-lc_.,u-(cf-rofJr-FROM TEST HOLE NO. AT DEPTH OF.___-7__9 FEET NATURAL MOISTURE CONTENT .__... �Z.,y� % NATURAL DRY DENSITY �og,o pCF 0 V. • SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure P] SAMPLE OF FROM TEST HOLE NO. 1¢ AT DEPTH OF Z -3 FEET NATURAL MOISTURE CONTENT �c„ o % NATURAL DRY DENSITY 10000 117. (. PCF O O n t 0 SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure 0] z 0 4. F Q o 6 z 0 U SAMPLE OF Gt pn�c,-�oh�Fv AT DEPTH OF (o --] FEET 10000 FROM TEST HOLE NO. NATURAL MOISTURE CONTENT. ¢ �j % NATURAL DRY DENSITY jo4-.-7 PCF 0 7 a n 0 c z 0 D 0 z m z c� z m m z SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure K 10000 SAMPLE OF FROM TEST HOLE NO. AT DEPTH OF 1-4— FEET NATURAL MOISTURE CONTENT ��,� % NATURAL DRY DENSITY boy L pCF n o 0 w 3 m N N 0 o 0 o n ' N N �O O � 1 � oW i 0 f f SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure ►1 SAMPLE OF FROM TEST HOLE NO. AT DEPTH OF -7 i3 FEET NATURAL MOISTURE CONTENT m 10000 Zz, % NATURAL DRY DENSITY lo¢,Z PCF 0 • i A SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure rj SAMPLE Of `��NrrrC�tA(' S�.Grc�•�c��; FROM TEST HOLE NO. q AT DEPTH OF 3 _� FEET NATURAL MOISTURE CONTENT 14-7 % NATURAL DRY DENSITY 10000 lob.-7 PCF 0 0 • J J W 3A 4 2. 0. b� K SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure 10000 SAMPLE OF FROM TEST HOLE NO. �. c� AT DEPTH OF z,_q FEET NATURAL MOISTURE CONTENT q,Y, % NATURAL DRY DENSITY 5 3.� PCF n o o a afD J. Vf O J. C. _' C zm O �t N N �O A t+ I � w D • 0 SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure 00) z 0 4. Q 0 o 6 z 0 U SAMPLE OF -J, 6RAjr,�� FROM TEST HOLE NO. 'L c� AT DEPTH OF Z-� FEET NATURAL MOISTURE CONTENT 12 4,, % NATURAL DRY DENSITY 10000 9-7,5 PCF [A • A J J W Cn 4 2. .� 0. `i SWELL -CONSOLIDATION LOAD (PSF) 500 1000 5000 Saturated at constant pressure SAMPLE OF AT DEPTH OF 2_3 FEET FROM TEST HOLE NO. 10000 NATURAL MOISTURE CONTENT 1$ -7 % NATURAL DRY DENSITY �0�5 pig r • • Date November 29, 1993 Commission No. 2104-01-01-01 BORING- LOGS u� NNNN sl. -p Imo"• �'R. �. low �v- > II io FOUNDATION ENGINEERING FIG.9 EI • Date November 29' 1993 Commission No.2104-01-01-01 -'Fs-r +bLr- µo.-7Z- BORING. LOGS I4h.9 rL cl o rr \ � 1o^ e, i60 v In4o.N�FP bn.rrJ� Iv'. IZ 2 .�I u rL Rfl 55' K. FOUNDATION ENGINEERING FIG. 8 Q&, Date November 29, 1993 Commission No. 2104-01-01-01 -t�sT Not, I-4o.1 BORING- LOGS to N�.17 4�.1 � Z�L" 20 -7 LIFT •' Ia � I'hi T��Io 7 D- IZ" I..IE,�-{a rtl.�'61LJvdFi L(2n�r:usf (oS — N`rzT�YGIs*tu� +loss TILT. . 3� � ti IZ�, v�,2x=i a J GWu.g.0 11/414?i �s FOUNDATION ENGINEERING FIG.7 0& Date November 29, 1993 Commission No. 2104-ni-o1-01 BORING. LOGS .a IZ" Fi0 A I — _ — _ — S I I��ol-lam GLA T�J FF•� � TI Y So+A Py' , No O - IZ" G�WlD Il�lo/5Z, ao FOUNDATION ENGINEERING FIG. 6 • Date November 29, 1993 Commission No.2104-01-01-01 BORING- LOGS IFS �uwx S^1 0 ' i• SI, MCI I� I I -a- 5M4eX, 7 ' HaD, SJ�T �5 e ' Z• .' -5j Ho 1'57 Mr�v• la��.d V—K IZ^ 1 17 — .e Ff e r T' FOUNDATION ENGINEERING FIG. 5 Date November 29, 1993 Commission No. 2104-01-01-01 I ,? F►a�N,.S BORING. LOGS W.(P 14-7 I�.v I� Ig l2 •• �` +. cite^1S'iiJ�Slli"n��011"✓1 71 Z .. 177Z„ CID a _ Fz 1 _ 17 �y 71(l ✓f -70 - FOUNDATION ENGINEERING FIG. 4 Ll Date November 29, 1993 Commission No.2104-01-01-01 l%t'f [10Lr 40.1 BORING. LOGS 4— 7_ -5 1-lo.il' �0 oIy,Z.. 1+41. ; •�' as - ., Zy1z.. r. r-y'GiV- 44 :-r R{ — a SPH7' Sl.vaa�c+.Lt- %S - -i o• a 2�2.� I't�IsT �I'e�. Yv�vr4 F -t3HFz 70++Ii I L e •o .. FOUNDATION ENGINEERING FIG. 3 Date November 29, 1993 Commission No.2T04-01-01-01 LEGEND OF SOI LS SYMBOLS FILL GRAVELS SANDS SHELBY TUBE SA14PLE SILTS GRAVELS, SAND & SILT COMBINATIONS STANDARD PENETRATION SANDY GRAVELS, TEST SAMPLER* GRAVELLY SANDS SILTY SANDS, SANDY SILTS SANDY CLAYS, WATER TABLE AT CLAYEY SANDS TIME OF DRILLING SAND, SILT & CLAY COMBINATIONS CLAYS HOLE CAVED WEATHERED BEDROCK SILTSTONE CLAYSTONE # 20/12 indicates that 20 blows of a 140 lb. hammer falling SANDSTONE 30" was required to penetrate 12" LIMESTONE GRANITE FOUNDATION ENGINEERING FIG. 2 Date: November 29, 1993 Commission No.: 2104-01-01-01 t-- — - — - — — - — — - — - — --- e a a a a a a a s a .I� N7 .� I � � k � I I a;.._......_....- .......... ..... ............................._..... -......I ' Nq. • u I\ �4 ia , -- sU�D�JISIot-�- Co l.oe-art�o .sV-fk— I.Ie3',o f BORING LOCATION MAP FIG. 1 M O I S T U R E- D E N S I T Y D E T E R M I N A T I O N Samples of representative fill materials to be placed shall be furnished by the contractor to the soils engineer for determination of maximum density and optimum moisture for these materials. Tests for this determination will be made using methods conforming to requirements of ASTM D698. Copies of the results of these tests will be furnished to the contractor. These test results shall be the basis of control for compaction effort. D E N S I T Y T E S T S The density and moisture content of each layer of compacted fill will be determined by the soils engineer in accordance with ASTM D1556 or D2167. Any material found not to comply with the minimum specified density shall be recompacted until the required density is obtained. The results of all density tests will be furnished to both the owner and the contractor by the soils engineer. 4 optimum compaction. The moisture shall be uniform throughout the fill. The contractor may be required to add necessary moisture to the backfill material in the excavation if, in the opinion of the soils engineer, it is not possible to obtain uniform moisture content by adding water on the fill surface. If, in the opinion of the soils engineer, the material proposed for use in the compaction is too wet to permit adequate compaction, it shall be dried in an acceptable manner prior to placement and compaction. Moisture requirements for utility backfill, roadway, and curb and gutter subgrades should be plus or minus two percent (+2%) of standard Proctor. C O M P A C T I O N When an acceptable uniform moisture content is obtained, each layer shall be compacted by a method acceptable to the soils engineer and as specified in the foregoing report as determined by the standard Proctor test (ASTM D698). Compaction shall be performed by rolling with approved tamping rollers, pneumatic -tired rollers, three -wheel power rollers, or other approved equipment well -suited to the soil being compacted. If a sheepsfoot roller is used, it shall be provided with cleaner bars attached in a manner which would prevent the accumulation of material between the tamper feet. The roller should be so designed that the effective weight can be increased. 3 P R E P A R A T I O N O F S U B G R A D E All topsoil and vegetation shall be removed to a depth satisfactory to the soils engineer before beginning preparation of the subgrade. The subgrade surface of the area to be filled shall be scarified to a minimum depth of six (6) inches, moistened as necessary, and compacted in a manner specified below for the subsequent layers of fill. Fill shall not be placed on frozen or muddy ground. P L A C I N G F I L L No sod, brush or frozen material or other deleterious or unsuitable material shall be placed in the fill. Distribution of material in the fill shall be such as to preclude the formation of lenses of material differing from the surrounding material. The materials shall be delivered and spread on the fill surface in such a manner as will result in a uniformly compacted fill. Prior to compacting, each layer shall have a maximum thickness of eight (8) inches and its upper surface shall be relatively horizontal. M O I S T U R E C 0 N T R 0 L The fill material in each layer, while being compacted, shall as nearly as practical contain the amount of moisture required for 2 APPENDIX A Suggested Specifications for Placement of Compacted Earth Fills and/or Backfills. G E N E R A L A soils engineer shall be the owner's representative to supervise and control all compacted fill and/or compacted backfill on the project. The soils engineer shall approve all earth materials prior to their use, the methods of placing, and the degree of compaction obtained. A certificate of approval from the soils engineer will be required prior to the owner's final acceptance of the filling operations. M A T E R I A L S The soils used for compacted fill beneath interior floor slabs and backfill around foundation walls shall be impervious and non - swelling for the depth shown on the drawings. No material shall be placed for fill which has a maximum dimension of six (6) inches or greater. All materials used in either compacted fill or compacted backfill shall be subject to the approval of the soils engineer. 1 0 • condition which might affect the performance of the foundation systems and roadways. 20 geotextile. Adequate discharge areas must be provided. Where the bedrock strata are not exposed in the subgrade, the edge drains without the blanket drain are recommended. G E N E R A L I N F O R M A T I O N The data presented herein were collected to help develop designs and cost estimates for this project. Professional judgments on design alternatives and criteria are presented in this report. These are based on evaluation of technical information gathered, partly on our understanding of the characteristics of the structure proposed, and partly on our experience with subsurface conditions in the area. We do not guarantee the performance of the project in any respect, only that our engineering work and judgments rendered meet the standard of care of our profession. The test holes drilled were spaced to obtain a reasonably accurate picture of subsurface conditions for design purposes. These variations are sometimes sufficient to necessitate modifications in design. We recommend that construction be continuously observed by a qualified soils technician trained and experienced in the field to take advantage of all opportunities to recognize some undetected 19 wall. The slab should be reinforced as necessary for the span involved. PRELIMINARY PAVEMENT RECOMMENDATIONS All interior roadways, as well as a portion of Harmony Road, are to be paved for this project. At this time, R-value test results had not been completed and the City of Fort Collins does not have adequate information to supply the required traffic criteria necessary to complete the pavement thickness recommendations. These recommendations will follow in a later report. Roadways where groundwater levels and/or bedrock surfaces are located within three (3) feet of the pavement surface will require a subdrain. Where bedrock is exposed at the subgrade, we recommend that a blanket drain be constructed between the aggregate base course and the subgrade. The blanket drain should consist of four (4) inches of Class B or C (Colorado Department of Transportation) filter material. The blanket drain shall be fully wrapped in a geotextile suitable for such usage. The blanket drain should be connected to edge drains located underneath the edge of the roadways. The invert of the edge drains should be a minimum of three (3) feet below the pavement subgrade. The edge drains should be a minimum width of twelve (12) inches with four (4) inch diameter perforated pipe at the bottom. The trench shall then be filled with Class B or C filter material and fully wrapped in 18 M M lieu of a plastic membrane. All plants located next to the foundation should be hand watered only using the minimum amount of water. Backfill around the outside perimeter of the structure, except as noted above, should be compacted from optimum moisture to three percent (3%) above optimum moisture, and from eighty-five percent (85%) to ninety percent (90%) of Standard Proctor Density as determined by ASTM Standard Test D-698. The backfill should be mechanically compacted in loose lifts not to exceed twelve (12) inches. Expansive soils and/or bedrock fragments should not be used for backfill materials. If imported material is used, the soil should be relatively impervious and non -expansive. The foundation walls should be well -cured, braced or subfloor installed prior to backfilling. Past experience has shown that severe damage could occur to the foundation walls if expansive material is placed for backfill and allowed to become wet. The backfill placed immediately adjacent to the foundation walls, if not properly compacted, can be expected to settle with resulting damage to sidewalks, driveway aprons, and other exterior slabs -on - grade. To avoid settlement and disfigurement of the slabs in the event that the backfill is not properly compacted, we recommend that concrete slabs which must span the backfill be supported by the foundation walls. This is conventionally done by use of a brick ledge or haunch. Exterior slabs could be dowelled to the foundation 17 M M pounds may be needed to excavate the firm bedrock. Bedrock used as fill should be broken into pieces less than six (6) inches in diameter. Proper placement of the bedrock as fill may be dif- ficult, and a disc or other mixing equipment may be needed to obtain uniform moisture and proper compaction. It is recommended that bedrock not be used as backfill adjacent to proposed build- ings. L A N D S C A P I N G A N D D R A I N A G E Every precaution should be taken to prevent wetting of the subsoils and percolation of water down along the foundation elements. Finished grade should be sloped away from the structure on all sides to give positive drainage. A minimum of twelve (12) inches fall in the first ten (10) feet is recommended. Sprinkling systems should not be installed within ten (10) feet of the structure. Downspouts are recommended and should be arranged to carry drainage from the roof at least five (5) feet beyond the foundation walls. Plantings are not recommended around the perimeter of the founda- tions. However, if the owners are willing to accept the risks of foundation and slab movement, low water use plant varieties could be used. A horizontal impervious membrane, such as polyethylene, should not be used next to the foundation wall. We recommend the use of a landscape fabric which will allow normal evaporation in 16 40 7. All exterior slabs should be constructed using a more durable sulfate resistant concrete containing Type II cement and with higher air contents and lower water cement ratios. S I T E G R A D I N G A N D U T I L I T I E S Specifications pertaining to site grading are included below and in Appendix A of this report. It is recommended that the upper ten (10) inches of topsoil below building, filled and paved areas be stripped and stockpiled for reuse in planted areas. The upper six (6) inches of the subgrade below paved and filled areas should be scarified and recompacted plus or minus two percent (±2%) of optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D-698-78 (See Appendix A of this report). Additional fill should consist of the onsite clayey soil or imported materials approved by the geotechnical engineer. Fill should be placed in uniform six to eight (6-8) inch lifts and mechanically compacted plus or minus two percent (+2%) of optimum moisture to at least ninety-five percent (95%) of Standard Proctor Density ASTM D-698-78. Bedrock encountered at the site may be used as fill material in selected areas. Heavy-duty construction equipment equivalent to an excavator having a gross weight of ninety thousand (90,000) 15 M !t (two (2) inches for caisson foundations) above or below interior nonload bearing partitions where floors consist of slabs -on -grade. All phases of construction should be con- structed to allow the void to function as intended. 3. Eliminate underllab plumbing where feasible. Where such plumbing is unavoidable, it should be pressure tested during construction to minimize leaks which would result in wetting of the subsoils. 4. Separate slabs -on -grade into panels by use of control joints. We recommend joints be placed no more than fifteen (15) feet on center. Control joints should also be located at potential weak areas such as the corners of driveway slabs. 5. All slabs -on -grade should be underlain with a four (4) inch layer of clean, crushed rock or gravel to help distribute floor loads and to provide a capillary break should moisture penetrate under the slab. 6. Due to the proximity of the groundwater and/or bedrock, any lower levels (i.e. basements), in some areas, should be provided with a perimeter drain as described in this report. The requirement for the drain should be made by the Engineer during the open hole inspection. 14 Where basement level construction is desired where groundwater levels will be within three (3) feet of the finished floor elevations, an area subdrain should be considered. The subdrain should be located underneath the sanitary sewer main and be designed to accommodate the perimeter drains described above, as well as lowering the groundwater underneath the roadway. F L O O R S L A B S Soils at proposed foundation elevations are stable at their natural moist condition. However, should moisture contents of the clayey soils or bedrock stratum increase, heaving will result, particular- ly at basement elevations. This phenomenon can result in cracking of the garage slabs or other slabs -on -grade. With the above in mind, construction of the structure, as much as possible, should be done to accommodate movement of the slabs without damage. We recommend the following: 1. Slabs should be constructed "free floating". The slab should be isolated from all structural components and utilities which penetrate the slab. Isolation may be accomplished with 112 inch isolation material or by sleeving. 2. Provide a one and one-half (1-112) inch minimum void space 13 so BASEMENT S AND SUBDRA INS Basement construction is feasible at most of the site. However, where basement or other habitable lower levels are located within three (3) feet of the bedrock and/or groundwater, we recommend that such lower levels be provided with a perimeter drainage system. The drainage system should contain a four (4) inch diameter perforated drain pipe encased in a minimum of twelve (12) inches of clean, 314 inch gravel graded in accordance with ASTM C 33-78. The drain pipe should extend around the lower level with the invert being placed a minimum of four (4) inches below the bottom of the footing to facilitate moisture transfer to the perimeter drain system. The gravel should be placed a minimum of eight (8) inches over the pipe the full width of the trench. The whole system should then be covered with untreated building paper or geotextile to minimize clogging of the gravel with the backfill material. The above drain system should be run at 118 inch per foot minimum to either a sump constructed in the basement or "daylighted" well beyond the foundation system. The sump should be a minimum of eighteen (18) inches diameter by three (3) feet deep and surrounded by at least six (6) inches of clean gravel similar to that provided around the drain. The sump should be provided with a pump designed to discharge all flow from the sump a minimum of five (5) feet beyond the backfill zone or into a subdrain designed to accommodate the anticipated flow. 12 6. A minimum of four (4) inches air space should be provided beneath all grade beams to insure the concentration of dead load pressure on all piers. 7. All piers should be carefully cleaned and dewatered before pouring concrete. in our opinion, casing and/or dewatering may be required. Concrete and reinforcement should be placed immediately after drilling of each pier. 8. Most of the bedrock at the site can be drilled with normal heavy commercial -size pier drilling rigs. Some of the bedrock may be very hard and a problem may arise if the contractor attempts to drill the pier holes in some of the areas with small drill rigs. in case drilling refusal is encountered, the depth of penetration into bedrock may be reduced if design criteria are adjusted accordingly. 9. All pier holes should be inspected during construction by a competent representative of the geotechnical engineer in order to insure that the required penetration and depths are met, that no loose material remains in the hole, and that the holes are properly dewatered prior to placement of the concrete. 11 so so given above may be used in uplift provided the sides of the hole are grooved. In drilling the piers, the following design and construction details should be observed: 1. Piers should be designed for the maximum end bearing, minimum dead load and skin friction specified in this report. 2. Grade beams should be reinforced with rebar to span between each pier. Rebar should be run continuously around corners and be properly spliced. 3. Bearing walls should be omitted in the basement. Partitions should be hung from the floor joists and beams which are supported by adjustable steel columns. A minimum two (2) inch void should be constructed under all partition walls located over slabs. 4. All piers should penetrate a minimum of five (5) feet into the firm bedrock with a minimum length of ten (10) feet. 5. All piers should be reinforced their full length to resist tension. We recommend the use of at least two (2) #5 bars. The rebar should extend into the grade beam to tie the pier to the grade beam. 10 The foundation walls and other structural elements should be designed by a qualified structural engineer for the appropriate loading conditions. All footings or pads should be placed below any topsoil or fill unless the fill has specifically been placed and compacted for support of footings or pads. All exterior footings, pads, and grade beams should be placed below frost depth (thirty (30) inches in this area) to provide adequate cover for frost protection. Drilled Piers and Grade Beams Where footings and/or grade beams will bear partially on the bedrock and partially on the upper soils, or where footing elevations are located within three (3) feet of the bedrock strata, we recommend the use of a drilled pier and grade beam type foundation system. The piers should be drilled a minimum of five (5) feet into the firm bedrock with a minimum length of ten (10) feet. The piers should be designed for a maximum end bearing value of 15,000 PSF, maximum side shear on that portion of the pier in bedrock of 1,500 PSF and a minimum dead load of 5,000 PSF. A nominal amount of reinforcing steel should be used in all piers. Difficulty is sometimes experienced in achieving the desired minimum dead load. If this occurs, we suggest the piers be reinforced full length to take the difference between the "desired" and the "obtainable" dead load in tension. The side shear value E 1. All footings, pads, and\or grade beams should be below frost depth. Frost depth in this area is considered to be thirty (30) inches. 2. Foundation walls should be reinforced with rebar to span an unsupported length of ten (10) feet or between each pad. Rebar should be run continuously around corners and be properly spliced. Foundations should be designed by a Registered Engineer for the conditions described in this report. 3. Bearing walls should be omitted in the basement. Partitions should be hung from the floor joists and beams supported by adjustable steel columns. A 1-112 inch void should be con- structed under all partition walls located over slabs. 4. it is our opinion that basement construction is feasible for this site. However, all finished floor slabs located within three (3) feet of the groundwater and/or bedrock stratum should be protected by a perimeter drain as detailed in this report. 5. All footings, pads, and/or grade beams should bear on similar strata. 6. We recommend the performance of an excavation inspection for each lot to make a final determination on foundation type. P depending upon variations in precipitation, surface irrigation and runoff on the site. Due to the shallow depth of bedrock in some areas, surface water from the above sources could percolate through the upper soils or backfill becoming trapped upon -the relatively impervious bedrock stratum forming a perched water table. The ambient groundwater table at the site is not expected to rise to a level which would affect the construction or utilization of a residence constructed over a basement unless a source of water not presently contributing becomes available. F O U N D A T I O N R E C O M M E N D A T I O N S Spread Footings Where clays and sands are encountered at footing elevations and at least three (3) feet above the bedrock strata, we feel that the structure should be supported by a continuous balanced spread footing and/or grade beam foundation. The footings should be designed for a maximum allowable bearing capacity of 1500 pounds per square foot (dead load plus 112 live load) with a minimum dead load of 500 pounds per square foot to help counteract potential swelling of the subsoils. The following recommendations should be followed in the design of , the foundation system: 7 of the deeper clays. Laboratory and field tests indicate that these deposits exhibit low to moderate bearing capacities with a low to no swell potential when wetted. The upper clays grade into clean to clayey sands. The sands contain traces to moderate amounts of gravel. These deposits exhibit low to moderate bearing capacities with no swell potential. The sands were encountered to depths ranging from two (2) feet to greater than twenty (20) feet. Siltstone, sandstone, and claystone bedrock strata were encountered below the upper sands and clays. Siltstone with claystone layers appear to be predominant material along the west side. Minor sandstone beds were observed in this area. Soft claystone was encountered primarily at the east end of the project. The bedrock strata exhibits moderate to high bearing capacities. The siltstone and claystone exhibits a moderate swell potential when wetted. The sandstones exhibit no swell potential. The bedrock strata were encountered to the depths explored. Groundwater observations were made as the borings were being advanced and immediately after completion of the drilling operation. At the time of our field investigation, groundwater was encountered in Test Hole Nos. 1, 21 3, 4, 7, 9, 10, 11 and 18 at depths ranging from twelve (12) feet to eighteen (18) feet. The groundwater table can be expected to fluctuate throughout the year volume. Results of those tests are presented at the end of this report. A calibrated hand penetrometer was used to estimate the approximate unconfined compressive strength of selected samples. The calibra- ted hand penetrometer has been correlated with unconfined compres- sion tests and provides a better estimate of soil consistency than visual examination alone. As part of the testing program, R-value tests were performed on selected samples to determine the soil support characteristics for roadway design purposes. At this time, R-value test had not been completed. S U B S U R F A C E C O N D I T I O N S Generally, very thin to moderately thick layers of alluvial and pediment soils overlie bedrock strata of the Pierre Shale. Free groundwater was encountered in nine (9) of the eighteen (18) borings. Clays containing slight to high amounts of sand and traces of gravel were encountered in the upper one (1) to twelve (12) feet of the borings. The clays appear to be more plastic near the north end of the project. Minor layers of sand were encountered in some 5 0 to (3) inch O.D. thin wall samplers (Shelby), pushed hydraulically into the soil in accordance with ASTM D-1587. In this sampling procedure, a seamless steel tube with a beveled cutting edge is pushed hydraulically into the ground to obtain a relatively undisturbed sample of cohesive or moderately cohesive soil. All samples were sealed in the field and preserved at natural moisture content until time of test. L A B O R A T O R Y T E S T I N G P R O C E D U R E S The recovered samples were tested in the laboratory to measure their dry unit weights, natural water contents, grain size and for classification purposes. Selected samples were tested for strength and stability characteristics. These include swelling, compressibility, collapse and shear strength of the soil and/or rock. One dimensional consolidation -swell tests were performed on selected samples to evaluate the expansive, compressive and collapsing nature of the soils and/or bedrock stratum. In the consolidation -swell test, a trimmed specimen is placed in a one- dimensional confinement ring and a vertical load is applied. After seating, the sample is inundated with water and the height change of the specimen is recorded. The confining load is then incremen- tally increased until the specimen is compressed to its original 4 on the attached diagram, are approximate and were made by pacing. Angles for locating the borings were estimated. Elevations of the borings are approximate and were obtained using a level and rod. The elevations were referenced to an assumed elevation of 100.0 feet using the top of the north nozzle of the fire hydrant at the northwest entrance to McGraw Elementary. The approximate location of the benchmark is shown on the attached boring location map, Figure 1. The locations and elevations of the borings should be considered only to the degree implied by the methods used to make those measurements. Complete logs of the boring operations were compiled by a represen- tative of our firm as the borings were advanced. The approximate location of soil and rock contacts, free groundwater levels, and standard penetration tests are shown on each boring log. The transition between different strata can be and most often is gradual. An index of soils relative density and consistency was obtained by use of the standard penetration test, ASTM Standard Test D-1586. The penetration test result listed on the log is the number of blows required to drive the two (2) inch split -spoon sampler twelve (12) inches (or as shown) into undisturbed soil by a one hundred and forty (140) pound hammer dropped thirty (30) inches. Undisturbed samples for use in the laboratory were taken in three 3 Road, east of Front Range Community College and west of Crest Road. The 28+ acre site consists of old alluvial and pediment deposits located over bedrock strata of the upper Cretaceous Pierre Shale. The southwest corner of the project had been previously stripped of overburden soils for use for the building pad for McGraw Elementary School. Two (2) irrigation ditches are located at the west end of the project. Twelve (12) lots are located east of the elementary school on Crest Road. The site is vegetated with grasses and has a slight to moderate slope towards the east. F I E L D I N V E S T I G A T I O N The field investigation consisted of eighteen (18) deep borings at selected locations on the site. Three (3) of the borings were sleeved for groundwater monitoring purposes. Twelve (12) additional shallow test holes were drilled for pavement recommendations. Distances between borings are as indicated on the attached test boring location map, Figure 1. The borings were advanced using a four (4) inch diameter continuous flight power auger. All borings were continued to hard bedrock or to depths considered sufficient for the purposes of this report as set forth in the scope. The borings were laid out by Foundation & Soils Engineering, Inc. personnel based on a plat provided by Land Design Studio. Distances from the referenced features to the boring locations, as indicated 2 a S C 0 P E The following report presents the results of our subsurface investigation on Coventry Subdivision, situated in the North Half of Section 2, Township 6 North, Range 69 West of the 6th Prime Meridian, Larimer County, Colorado. This investigation was performed for Colorado Land Source at the request of Ms. Kay Force of Jim Sell Design, Inc. We understand the site is to be developed into one hundred nine (109) single family residential lots. Construction is to be typical wood frame type and brick veneer and as such, should generate only light loading, on the order of 1,000 to 2,000 PLF. Concentrated loads, if any, should not exceed 15 to 20 KIPS. The purpose of this investigation is to identify subsurface condi- tions and to obtain test data to properly design and construct the foundation system, floor slabs, and roadways. The conclusions and recommendations presented in this report are based upon the acquired field and laboratory data and previous experience with similar subsurface conditions in the area. S I T E D E S C R I P T I O N The site is located in southwest Fort Collins, south of Harmony 1 a a TABLE OF CONTENTS Letter of Transmittal i Scope 1 Site Description 1 Field Investigation 2 Laboratory Testing Procedures 4 Subsurface Conditions 5 Foundation Recommendations 7 Basement and Subdrains 12 Floor Slabs 13 Site Grading and Utilities 15 Landscaping and Drainage 16 Pavement Recommendations is General Information 19 Test Boring Location Map Figure 1 Legend of Soil Symbols Figure 2 Boring Logs Figures 3 - 9 Consolidation Swell Test Figures 10 - 20 Summary of Test Results Figures 21 - 26 Suggested Specifications for Placement Appendix A of Compacted Earth Fills and/or Backfills a a November 29, 1993 Commission No.: 2104-01-01-01 Colorado Land Source 9085 East Mineral Circle #200 Englewood, Colorado 80112 Gentlemen: The enclosed report presents the results of a subsurface investi- gation for Coventry Subdivision, a proposed subdivision of Fort Collins, Colorado. In summary, low to non -swelling sands, clays and moderately swelling bedrock strata were encountered in the borings. Although the site soils and/or rock are suitable for support of the proposed structures, care will be needed in both the design and construction of the buildings to minimize the potential for foundation and floor slab movement. The attached geotechnical report presents the results of our investigation and recommendations concerning design and construc- tion of the foundation system and support of floor slabs. We appreciate the opportunity to be of service to you on this project. If you have ons;. please feel free to call. Respect ul1y, 23841 Kevin W. Patterson, FOUNDATION & SOILS KWP1jlb ,cC7rJ sfi Sell :Design Ih- 46 a SUBSURFACE INVESTIGATION FOR COVENTRY SUBDIVISION FORT COLLINS, COLORADO Prepared for Colorado Land Source 9085 East Mineral Circle #200 Englewood, Colorado 80112 November 29, 1993 Commission No.: 2104-01-01-01 Prepared By FOUNDATION & SOILS ENGINEERING, INC. CONSULTING ENGINEERS 100 East Third Street Loveland, CO 80537