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HomeMy WebLinkAboutJOHNSON PROPERTY - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -GEOLOGIC AND PRELIMINARY GEO_ TECHNICAL INVESTIGATION JOHNSON PROPERTY NORTHWEST CORNER OF TIMBERLINE AND DRAKE ROAD LARIMER COUNTY, COLORADO Prepared For. The James Company 2919 Valmont Road, Suite 204 Boulder, Colorado 80301 Attention: Mr. David C. White Job No. FC-1562 August 31, 2000 CTL/THOMPSON5 INC. CONSULTING ENGINEERS 375 E. HORSETOOTH RD. ® THE SHORES OFFICE PARK ® BLDG. 3, SUITE 100 0 FT. COLLINS, CO 80525 970) 206-9455 TABLE OF CONTENTS SCOPE SUMMARY OF CONCLUSIONS SITE CONDITIONS PROPOSED DEVELOPMENT SITE GEOLOGY AND GEOLOGIC HAZARDS INVESTIGATION SUBSURFACE CONDITIONS SITE DEVELOPMENT Overlot Grading Sub -excavation Utility Construction Underdrain Pavements RESIDENTIAL AND LIGHT COMMERCIAL CONSTRUCTION Foundation Systems Floor System and Slab -on -Grade Construction Basements Surface Drainage RECOMMENDED FUTURE INVESTIGATIONS LIMITATIONS FIG. 1 - LOCATION OF EXPLORATORY BORINGS FIG. 2 - ESTIMATED DEPTH TO GROUND WATER SURFACE FIG. 3 - ESTIMATED ELEVATION OF GROUND WATER SURFACE FIG. 4 - ESTIMATED DEPTH TO BEDROCK SURFACE FIG. 5 - ESTIMATED ELEVATION OF BEDROCK FIG. 6 - UNDERDRAIN DETAIL FIGS. 7 THROUGH 16 - LOGS OF EXPLORATORY BORINGS APPENDIX A - LABORATORY TEST RESULTS APPENDIX B - GUIDELINE SITE GRADING SPECIFICATIONS M 1 1 2 3 3 7 7 9 10 11 12 12 13 13 13 14 14 14 15 THEJAMES COMPANY JOHNSON PROPERTY CTUT JOB NO. FC-1562 0 SCOPE This report presents the results of our Geologic and Preliminary Geotechnical Investigation for the Johnson property, located northeast of the intersection of Timberline Road and Drake Road in Fort Collins, Colorado. We understand residential and mixed use development is planned for the site. Our investigation was performed to evaluate the subsurface conditions to assist in planning for the site and to fulfil zoning and platting requirements. The report includes a description of site geology and a geologic hazard assessment-, descriptions of the subsoil and ground water conditions found in thirty five exploratory borings, and our opinions regarding geotechnical conditions that will affect the proposed residential and mixed use development and construction. The report was prepared based on conditions disclosed by our exploratory drilling, results of laboratory tests, engineering analysis of field and laboratory data and our experience with similar subsurface conditions in this area. The criteria presented in the report are intended for planning purposes only. Additional investigations will be required to design residential or commercial structures and roadway pavements. A summary of our conclusions is presented below. SUMMARY OF CONCLUSIONS 1. Subsurface conditions found in the exploratory borings varied but generally consisted of sandy clays and silty sands with gravel underlain by claystone bedrock. Sandy gravels were encountered in three of the test holes. Thin lenses of cemented sandstone bedrock were encountered in three of the borings just above the claystone bedrock. T.. 2. The dry, sandy, soft to medium stiff clays near the surface exhibited k low to high potential for collapse while the slightly moist, stiff to very stiff clays at greater depths tend to exhibit low to moderate swell potential. The samples of claystone bedrock we tested exhibited a swell potential that ranged from low to high. 3. Ground water was measured in each of the borings at depths of to 21 feet below the existing ground surface. Ground water will likely' li imtbasement -level construction for portions of the site unless MpJ ,•': i THE JAMES COMPANY JOHNSON PROPERTY q;,^ . CTUT JOB NO. FC-1562 measures such as an underdrain system and/or site 4. We believe there are no geological or geotechnical constraints at the site that will preclude the proposed construction.. Collapsing soils, expansive soils and bedrock, shallow ground water and localized steep slopes are the main geotechnical features that should be addressed during site development. 5. Site grading should be designed to avoid excessive cuts, which could create shallow ground water and/or shallow bedrock conditions. Basement floors should be set at least 3 feet, and preferably 4 feet or more above the measured ground water level. Utility trenches may require dewatering. 6. Preliminary information indicates about 90 percent of structures on the site may be founded on footings designed with a minimum deadload pressure. Collapsing soils and/or soft soils may necessitate structural mats beneath footings, or extending footings down to stronger native soils. Drilled piers will likely be required where expansive ciaystone is encountered near proposed foundation elevations. 7. Overall surface drainage should be designed to provide rapid run-off of surface water away from the proposed structures. Water should not be allowed to pond near the crest of slopes, on or adjacent to pavements, or adjacent to the structures. SITE CONDITIONS The Johnson property is about 225 acres located northeast of the intersection of Timberline Road and Drake Road in east -central Fort Collins, Colorado (Fig. 1). One large parcel within the property boundary is excluded from this study. The property is divided topographically into two comparatively flat areas separated by a prominent slope. The slope is located near the approximate mid -point of the southern property boundary, and trends approximately north 45 degrees east through the property from that point. Elevations on the property range from a high of 4,938 near the northwest corner of the property to a low of 4,865 near the southeast corner of the property. A drainage pipeline runs adjacent to the lower edge of the slope in the east side of the central 1/3 of the property. The ground surface generally has slopes less than 5 percent in the flat areas above and. below THE JAMES COMPANY JOHNSON PROPERTY 2 CTLIT JOB NO. FC-1562 a riI the slope. Grades on the steeper slope are on the order of 15 percent with steeper slopes in localized areas. The majority of the property consists of cultivated farm land. There are numerous houses, barns and sheds in the far north and the south ends of the property. There are several corrals in the central part of the property. Adjacent properties consist of farmland and industrial buildings to the west, commercial and industrial buildings to the east, commercial buildings to the north, and a residential construction development to the south. A railroad track borders the property on the northeast side. PROPOSED DEVELOPMENT We understand the property is planned for residential and mixed use development. Site grading plans were not available at the time of this investigation. Because of the existing topography, we anticipate significant cuts and fills for the proposed construction. Paved streets and driveways will be constructed to provide access. Buried sanitary and storm sewers and water lines will be constructed beneath the streets. We anticipate the residences will be one or two story, wood framed structures with basements. Basement excavations may be 5 to 7 feet deep. We assumed the mixed use buildings will be one or two story steel or masonry structures with no basements. SITE GEOLOGY AND GEOLOGIC HAZARDS Site geology was investigated through review of geologic maps, field observations and evaluation of the drilling and laboratory data. This section is intended to discuss concerns related to geologic hazards that may occur during planning and zoning for land use changes. Geologic mapping of the Lower Cache La Poudre Basin by Hershey and Schneider (USGS Map 1-687, 1972) indicates the surface soils over most of the property are variable, and include: eolian soils, described as wind -deposited clay, THE JAMES COMPANY JOHNSON PROPERTY 3 CTIJT JOB NO. FC-1562. silt and sand; alluvial sand and gravel deposits; and pediment deposits comprised of arkosic sands, gravels, and clays, all of Pleistocene and Holocene Age (previous 2 to 3 million years). The wind deposited clays and silts developed a fragile structure during and after deposition. When wetted under overburden pressure, these soils tend to collapse to form a more stable structure, which can result in damaging movements to foundations and floor slabs. Based on the strata encountered in our borings the eolium is of variable occurrence and thickness near the existing ground surface over most of the site. The windblown deposits overly and are interlayered with the alluvial (water - deposited) deposits and the pediment deposits described above. Some clay phases of the soils include expansive clays generally with low swell potential. The overburden soil deposits range in thickness from 7 feet to.28 feet. The underlying bedrock consists of the Middle and transition zones of the Pierre Shale, which generally consists of olive -gray, sandy, claystone-shale and fine-grained sandstone. The total thickness of the Pierre Shale ranges from. 5,000 to 8,000 feet in this area. We believe the Pierre Shale dips gently to the east at about 5 degrees in the area. Our field exploration generally confirmed the conditions described by published mapping. The clay and. claystone bedrock are considered expansive, which could result In heave -related damage to improvements or structures when moisture increase occurs. Some of the clays and silts have a tendency to collapse when wetted under overburden pressure. Engineered design of foundations, slabs -on -grade, pavements and surface drainage can mitigate the effects of collapse -prone solls and expansive soils and bedrock. Methods for mitigation of swell and collapse -prone soils are discussed in following sections of the report. Hard, cemented lenses of sandstone bedrock are possible in deeper excavations on the site. Site soils and bedrock are not expected to be unusually corrosive to concrete or metal. THE JAMES COMPANY JOHNSON PROPERTY 4 CM JOB NO. FC-1562 b Significant faulting and structural discontinuities are not expected in the bedrock at this site. The soil and bedrock units are not expected to respond unusually to seismic activity. The area is considered by the most recent editions of the Uniform Building Code (UBC) as Zone 1, its least active zone designation. Maximum bedrock accelerations at 4 percent of gravity are probable during major earthquakes in the area. Only minor damage to relatively new, properly designed and built residences would be expected. Regarding the potential for radioactive substances on the parcel, it is normal In the Front Range of Colorado and nearby eastern plains area for radon gas to accumulate in poorly ventilated spaces (i.e., full -depth residential basements) in contact with soil or bedrock. The City of Fort Collins addresses the radon issue in Ordinance No. 45, 1997 and other publications that recognize radon as a health hazard_. The amount of radon gas that can accumulate in an area is a function of many factors, including the radionuclide activity of the soil and bedrock, construction methods and materials, soil gas pathways and accumulation areas. Typical mitigation methods consist of sealing soil gas entry areas and periodic ventilation of below -grade spaces. Radon rarely accumulates to significant levels in above -grade living spaces. Fort Collins has addressed "Radon Reduction Systems" in their book of amendments to the 1997 Uniform Building Code. The extreme northeastern portion of the site may be prone to flooding during extreme flood events because of its comparatively low elevation and proximity to the Cache La Poudre River. However, a floodplain map published by the city of Fort Collins suggests the property is not located within the 100 year floodplain of the Cache La Poudre River. There are no highly -developed, incised drainages on the site. During peak precipitation events, some accumulation of surface sheet flow in drainages is expected. Development typically increases the relative amount of impervious surfaces, which can lead to drainage problems and erosion if surface v water flow is not adequately controlled. Evaluation of flooding potential and surface drainage design should be performed by a civil engineer as part of the project y. design. Erosion potential on the site is considered low on the flat -Lying portions of the site, and moderate to high on the steep slope that bisects the property. Erosion THE JAMES COMPANY JOHNSON PROPERTY 5 CTUT JOB NO. K-1562 potential can be expected to increase during construction, but should return to pre - construction rates or less if proper grading practices, surface drainage design and revegetation efforts are implemented. Groundwater was encountered in our borings at approximate depths of 2 to 21 feet during drilling and several days after drilling. Our field investigation occurred during the summer months when groundwater levels are typically higher due to N irrigation. Portions of the site were inaccessible due to irrigation. Groundwater x; levels will likely increase in the wetter months and during wetter years. If groundwater levels increase to foundation levels, related problems wi... occur. The rise in groundwater to the foundation level will tend to soften the compressible soils, cause large volume changes in collapsing soils, cause expansion of soils with swell potential if present, and could result in persistent wet or moist conditions in crawl' spaces and basements. Mitigation includes underdrains or interceptor drains to lower the groundwater level, ground improvement techniques to increase the strength of soft soils, and special foundation selection and design criteria if swelling or collapsing soils are present. We do not believe the site is located above underground mines or is located in a subsidence hazard zone. Site soils and bedrock are not considered subject to ground subsidence related to natural or mining processes. The bedrock below the site is the Pierre Shale formation which does not contain significant coal beds. There is no evidence of past mining activities on the site. We do not believe the site is an economic source of gravel. No other economically important mineral deposits are expected on this site or are known to occur nearby. No geologic hazards which would preclude the proposed development were noted on the subject tract. We believe the geologic hazards can be mitigated with proper engineering design and construction practices, as discussed in this report. THE JAMES COMPANY JOHNSON PROPERTY 6 CTLIT JOB NO. FC-1562 I INVESTIGATION Subsurface conditions were investigated by drilling 35 borings to depths of 15 to 35 feet at the approximate locations shown on Fig. 1. The borings were drilled using 4-inch diameter, continuous -flight auger and a truck -mounted drill rig. The drilling operations were observed by our field representative, who also logged the soils and obtained samples for laboratory testing. PVC pipe was placed in the borings so that groundwater levels could be measured at a later date. The location of the borings was limited to some extent by soft ground conditions that prevented access by the drill rig. Ground conditions below those portions of the property, primarily in the southwestern and east -central areas) were interpolated from the available data. Completion of the field investigation after irrigation has ceased can confirm our assumptions in areas where borings were not possible at the time of this investigation. Graphic logs of the soils found in our borings and results of field penetration resistance tests are presented on Figs. 7 through 16. Samples obtained during drilling were returned to our laboratory, where they were visually classified and samples were selected for testing. The results of laboratory testing are presented In Appendix A and summarized on Table A-1. SUBSURFACE CONDITIONS The subsoils encountered in our borings consisted of widely varied and intermixed eolian (wind deposited) silts and clays; and alluvial (water -deposited) clays, silts and sands underlain by claystone bedrock. Occasional thin lenses of cemented sandstone were encountered. Gravel was encountered at depths of 3 feet to 18 feet in TH-32, TH-40, TH-44 and TH-51. One boring (TH-39) encountered approximately 8 feet of very soft to soft clay fill. We understand from the current owner that this fill was placed after the removal of an underground gasoline tank at an unspecified time in the past. The over burden soils were thickest near the northwest corner of the property. Field penetration resistance tests indicated the sands were loose to medium dense and the clays were soft to very stiff. Hard THE JAMES COMPANY JOHNSON PROPERTY CTUT JOB NO. FC-1562 7 claystone bedrock was encountered in 18 of 35 borings at depths ranging from 7 to 28 feet below the ground surface. Interpreted contours of the depth to the bedrock surface are shown on Fig. 4 and estimated elevation contours of the bedrock surface are shown on Fig. 5. nnp-dimensional swell -consolidation tests were performed on samples of the sandy clays and claystone. Eleven samples of the clay were tested for swelUconsolidatlon characteristics. Six samples exhibited slight compression to low swell (-0.20 to 0.50) when wetted under an applied load of 1,000 psf. One sample showed moderate swell (2.0 percent), one sample showed high swell (4.80 percent) and three samples showed high collapse potential (-5.6 to -11.3 percent). Five samples of claystone were selected for swell testing. Three of the bedrock samples F exhibited low swell (0.20 to 1.8 percent), and two showed moderate swell (3.2 and 3.9 s, percent). The moderate swelling samples were found in the south (TH-44) and north TH-2) part of the site, generally beneath relative high ground. Ground water was measured in 33 of 35 borings at depths ranging from 2 to rir 21 feet below the existing ground surface when measured several days after drilling. Ground water was measured within 10 feet of the surface in 40 percent of our borings. We believe basement construction will be restricted on 30 percent of the site unless mitigation of the shallow_ water is included in the design. Mitigation methods most commonly include raising site grades and/or the design and installation of an area -wide subdrain system. Such systems are commonly installed i below sanitary sewers and should flow to a positive gravity outfall. A combination of these two mitigation techniques may be an effective solution for this site. Additional discussion of shallow ground water investigation is presented in the Underdrain99 sub -section. In general, the water appears shallowest near the south property boundary, in the southeast corner of the property, and in the east -central part of the property. Site grading that would lessen the prominent natural slope on the property would likely increase the area impacted by shallow ground water. The estimated depth to the ground water surface is presented on Fig. 2 and estimated elevation contours of the ground water surface are shown on Fig. 3. Ground waterMhoxptiof THE JAMES COMPANY JOHNSON PROPERTY $ t;. CTUT JOB NO. FC-1562 levels are expected to fluctuate with operation of irrigation ditches and with changing seasons, and will likely rise following development of the site. SITE DEVELOPMENT Site grading will affect the proposed construction. Based on the existing topography, we anticipate minor grading for the extreme eastern and western portions of the site. In the area of the prominent natural slope, however, grade changes could be extensive. Large cuts in that area will result in the near surface h gravels and the bedrock surface being closer to the final design elevation of the site µ in that area. Geotechnical implications of such a plan that should be considered A;: include shallow ground water, potentially shallow, expansive bedrock, and very hard, cemented sandstone that will likely require special excavating equipment or possibly blasting to install underground utilities. Grading plans should be provided to us so 44p,. we can evaluate potential impacts of grading on the proposed construction. Ground water was measured in the majority of borings between 2 and 21 feet deep at the time of this investigation. Site grading should be planned to avoid excessive cuts where shallow ground water is known to exist, and also in areas where such grading would create shallow ground water conditions. Figure 2 shows areas where ground water was encountered at depths less than 10 feet below the existing ground surface. Basement excavations should be set at least 3 feet, and preferably 4 feet, above the measured ground water level. Large cuts near the crest of the prominent natural ridge will result in expansive claystone bedrock nearer the ground surface and closer to potential foundation elevations. Such a grading plan may increase the need for drilled pier I{ r .. foundations and structural basement floors in certain areas. In areas where fill is required, the ground surface should be stripped of vegetation, scarified, moisture -conditioned to within ±2 percent of optimum moisture THE JAMES COMPANY JOHNSON PROPERTY 9 cTUT JOB NO. FCA562 content and compacted to at least 95 percent of standard Proctor maximum dry w density (ASTM D 698). We anticipate stripping will require minimal cuts of 3 to 5 inches for the majority of the site. The on -site soils can be used as site grading fill. Highly plastic and swelling clays and claystone are not desirable as fill because they may cause problems associated with expansive soils. We believe clay fill should be placed at high y. j moisture content to reduce the swell potential. Clay fills should be moisture -treated to between optimum and 3 percent above optimum moisture content, and sand fll within ±2 percent of optimum. moisture content. Fills should be compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698). The placement and.. compaction of site grading fill should be observed and tested by a qualified geotechnical engineer. Preliminary evaluation of the data indicates the near -surface soils in the northeastern area of the property (vicinity of TH-1, TH-39 and TH-4 through TH-8, TH- 10, TH-11 and TH-14 through TH-16) are dry, sandy silts and clays that have a high collapse potential. These soils are variable in occurrence and in thickness. There is more risk of damage to structures built on collapsing soils. In areas where collapsing soils occur near foundation level, we recommend sub -excavating and replacing a minimum of 3 feet ofthe soils below the planned foundations and floor slabs. Excavation inspections and density testing are commonly recommended for sites such as this in addition to a design level geotechnical investigation. We recommend the collapsing soil areas be further investigated and delineated during design level geotechnical investigations for foundations and pavements. Soft clay fill was encountered in boring TH-39. We recommend the limits of the fill be determined during design level geotechnical investigation, and the fill be removed from beneath structures, utilities or pavements. THE JAMES COMPANY JOHNSON PROPERTY 10 CTUT JOB NO. FC-1562 We believe excavations for utility installation in the near surface clays, sands and gravels can be performed with conventional trenchers or backhoes. Ground water will be encountered, and temporary dewatering should be anticipated during r utility construction. For shallower excavations, dewatering may be accomplished by sloping excavations to occasional sumps where water is removed by pumping. The sumps should be several feet below the bottom of the excavations so that water Is pumped down through the soils rather than up through the bottoms of excavations, which could de -stabilize the excavation floors. For deep excavations, ry or excavations in areas where grading will result in shallow ground water, more extensive dewatering such as a series of well points may be needed. Spoils piles should not be placed immediately adjacent to the excavations. We recommend a distance back from the edge of the trench at least as great as the depth of the trench. Utility trenches should be sloped or shored to meet local, State and FederalN,J safety regulations. Based on our investigation, we believe the sands, gravels and very moist to wet clays are Type C soils, the clays Type A or B soils and bedrock 4' Type A soils based on OSHA standards. We believe the Type C soils will control the design. According to OSHA guidelines, Type C soils should. be sloped no steeper than 1.5.1 (horizontal:vertical). Sands and gravels near the water table may cave to flatter slopes. Contractors should identify the soils encountered in the excavation and refer to OSHA standards to determine appropriate slopes. Deep trenches, or excavations in areas where cuts have resulted in comparatively shallow bedrock may penetrate gravel with large cobbles and very hard, cemented bedrock lenses. These layers may require special excavation machinery or blasting to loosen them sufficiently for underground utility installation in trenches. Excavations deeper than 20 feet should be designed by a professional engineer. Water and sewer lines are usually constructed beneath paved roads. Compaction of trench backfill can have a significant effect on the life and THE JAMES COMPANY JOHNSON PROPERTY 11 CTUT JOB NO. FC;1562 rf . serviceability of pavements. We believe trench backfill should be placed in thin, loose lifts, moisture -conditioned to within ± 2 percent of optimum moisture content and compacted to, at least 95 percent of standard Proctor maximum dry density a ; ASTM D 698). The placement and compaction of fill and backfill should be observe and tested by a geotechnical engineer. Ground water was measured within 10 feet of the surface in 40 percent of our borings, and may rise with long-term development and subsequent irrigation. We believe basement excavations should be set at least 3 feet, and preferably 4 feet, above the measured ground water level. Consequently, basement -level construction is not recommended where ground water is located shallower than 10 feet unless mitigation measures such as a sub -drain system are implemented. We advocate the use of underdrain systems incorporated into the design of and constructed below sanitary sewer systems to help control ground water levels and provide a gravity outfall for the foundation drains. A typical underdrain cross - pp: section Is shown on Fig. 6. Lowering the ground water level may also make basement construction feasible, or may be effective in combination with increasing site grades. Evaluation of a sub -drain system, particularly the feasible outfalls for such a system should be considered in the development of this property. City of Fort Collins regulations require a pavement design investigation be performed after overlot grading is completed and wet utilities are installed. For planning purposes, however, we anticipate a pavement section of 3.5 inches of asphaltic concrete over 8 to 12 inches of base course may be required for local streets. Collector and arterial streets will require thicker sections. A subgrade investigation and pavement design should be performed after overlot grading is complete and. utilities have been installed to determine final design thicknesses. THE JAME_S COMPANY JOHNSON PROPERTY 12 CTL IT JOB NO. FC-1562 RESIDENTIAL AND LIGHT COMMERCIAL CONSTRUCTION The near=surface soils over the majority of the site include collapsing silts and clays, low -swelling clays and expansive claystone bedrock. We believe that design level geotechnical investigations will show that the majority of residences and light commercial buildings can be founded on footing foundations bearing on the native sands and clays. We believe sub -excavation of collapsing soils may be recommended in an estimated 40 percent of the property. Where soft soils are encountered (SPT less than 4) at foundation -bearing elevations, it may be necessary to construct footings on several feet of imported granular fill, or extend footings down to stronger native soils. Footings on stiff clays or low -swelling claystone may require design to maintain high deadload pressures. Shallow claystone bedrock was encountered in one boring (TH-32) along the ridge between the higher elevations in the western 1/3 of the site and the lower elevations located in the southeastern corner of the site. We believe drilled piers will likely be required for this area which we estimate to be about 10 percent of this site. Ground water was measured at 2 to 21 feet below the surface, and will likely complicate pier installation. Temporary casing, dewatering, and concrete placement by tremie or pumping methods may be necessary for deep piers. A detailed Soils and Foundation Investigation should be performed after site grading has been completed to provide lot -specific design recommendations. Floor System and Slab -on -Grade Construction We estimate about 40 to 50 percent of the site to have low to moderate swell and/or collapse potential. Slab -on -grade floors are typically used in unfinished basements for these soil conditions. Structurally supported floor systems should be used in all non -basement finished living areas and in basements on lots where the swell potential is rated as high or very high. We also generally recommend supported basement floors for walk -out basements on lots with moderate, high and THE JAMES COMPANY JOHNSON PROPERTY 13 CTUT JOB NO. FC•1562 very high swell potential. Home buyers should consider structural basement floors on any lot where they intend to finish the basement. Ground water was measured between 2 and 21 feet deep (Fig. 3) at the time of our investigation. Site grading should be planned to set the basement floor levels at least 3 feet, and preferably 4 feet or more above the ground water level. We recommend foundation drains be installed around basements. If no underdrain system is installed, foundation drains should lead to a sump pit where a pump is Installed to remove water. Basement walls should be designed and constructed to resist lateral earth pressures. The ground surface around the structures should be graded to provide for rapid run-off of surface water away from the structures and off of pavements. We recommend slopes of at least 12 inches in the first 10 feet for the areas surrounding residences, where practical. Roof downspouts and other water collection systems should discharge well beyond the limits of all backfiil around the residences. Water should not be allowed to pond between residences or on or adjacent to pavement. Proper control of surface run-off is also important to control erosion of surface soils. Sheet flow should not be directed over unprotected slopes. Water should not be allowed to pond at the crest of slopes and on or adjacent to pavements. Permanent overlot slopes should be seeded or mulched to reduce erosion. RECOMMENDED FUTURE INVESTIGATIONS Based on the results of this investigation and the proposed development, we recommend the following investigations be performed: 1. Review of the site grading plans by our firm; 2. Subgrade investigation and pavement design after grading and utility installation; THE JAMES COMPANY JOHNSON PROPERTY 14 CTUT JOB NO. FC-1562 1 3. Evaluation and design of the underdrain system (if planned); 4. A design -level Soils and Foundation Investigation after grading; and 5. Delineation and mitigation of the man -placed fill in the area of TH-39; and 6. Construction testing and inspection during site development and construction. LIMITATIONS Our borings were widely spaced to provide a general characterization of subsurface conditions for preliminary assessment and planning of residential and light commercial construction. Conditions between borings may vary. We believe this investigation was conducted in a manner consistent with that level of care and skill ordinarily used by geotechnical engineers practicing in this area at this time. No other warranty, expressed or implied, is made. If we can be of further service in discussing either the contents of this report or our analysis of the influence of subsurface conditions on the design of the proposed development, please call. CT H0MPSON, INC Seth Buckman e.Di v-; ri Thomas A. tia e , CPG; tE Project Man ;hn - S C IAL SBTAC:nIj 6 copies sent) THE JAMES COMPANY JOHNSON PROPERTY CTUT JOB NO. FC-1562 15 1 714,N O 34 TH-41 TH-5o VICINITY MAP FORT COLLINS AREA) NO SCALE LEGEND: TH-1 INDICATES APPROXIMATE LOCATION OF EXPLORATORY BORING O TH-13 INDICATES APPROXIMATE LOCATION OF BORINGS TO BE MILLED AFTER HARVEST Locations of Exploratory Borings 451 Wy r Y••• F,V Y ' tyyyyy{ r'' lei:. SCALE: 1 "=600' TH-1 TH-2 39TH TH-4 \THHM-23 TH"3 i T" TH-6 TH-7 T010 TH-11 TH-14 TH-15 TH-20 TH 21 .H-22 O O O TH3 T" TH-1.2 TH.13 O TH-18 TH-17 O TH-18 O TH-19 O TH-24 TH-a T>-28 ® O O O ® ® TH33 H35 TH-38 TH 47 _ O O O TH38 TH 31 O THE TH-45 James Company JOHNSON PROPERTY No. FC-1562