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HomeMy WebLinkAboutPreliminary Geotech InvestigationPRELIMINARY GEOTECHNICAL INVESTIGATION CORYELL RANCH GARFIELD COUNTY, COLORADO Prepared For; MELROSE CORPORATION P. O. Box 21307 Hilton Head Island, SC 29925 Attention; Mr. Jack Best Job No. GS-2647 Part II January 29, 1999 CTUTHOMPSON, INC. CONSULTING ENGINEERS 234 CENTER DRIVE 9 GLENWOOD SPRINGS, COLORADO 81601 ■ (970) 945-2609 TABLE OF CONTENT SCOPE 1 SUMMARY OF CONCLUSIONS 1 SITE DESCRIPTION 2 PROPOSED DEVELOPMENT 4 SUBSURFACE CONDITIONS 4 Clays 5 5 Gravels and Sands 6 Ground Water SITE DEVELOPMENT 6 Overlot Grading and Road Grading 6 Utility Construction 8 PRELIMINARY BUILDING CONSIDERATIONS 8 Preliminary Building Considerations 8 Interior Floors and Exterior Slabs -On -Grade 9 Below Grade Walls 10 EARTH RETAINING STRUCTURES 11 Interior Subdivision Roads 12 SURFACE DRAINAGE 14 LIMITATIONS 14 FIGURE 1 - APPROXIMATE LOCATIONS OF EXPLORATORY BORINGS AND PITS FIGURES 2 AND 3 - SUMMARY LOGS OF EXPLORATORY BORINGS AND PITS FIGURE 4 - SWELL CONSOLIDATION TEST RESULTS FIGURES 5 THROUGH 8 - GRADATION TEST RESULTS TABLE 1 - SUMMARY OF LABORATORY TESTING MELROSE CORPORATION CORYELL RANCH CTLfT GS-2647, PART 11 SCOPE This report presents the results of our Preliminary Geotechnical investigation for the Coryell Ranch in Garfield County, Colorado. The site is planned for a residential development. The subsurface exploration and engineering analysis were performed to provide an overview of geotechnical considerations to assist in planning the development of the subdivision and developing preliminary foundation recommendations. After building footprints are finalized and building plans are known, additional design level geotechnical study will likely be required for each site. The report identifies issues believed to be common throughout the site and to most of the lots and provides preliminary geotechnical discussion and recommendations regarding overlot grading, infrastructure installation, building site excavations and fills, foundation construction, lateral earth pressures and floor slabs. Our report includes a description of the subsoil conditions found in our exploratory borings and exploratory test pits and a discussion of site development as influenced by geotechnical considerations. This investigation was performed in accordance with our Proposal GS-98-242, dated December 10, 1998. This report is based on conditions disclosed by our exploratory drilling and excavation, site observations, results of laboratory tests, engineering analysis of field and laboratory data and our experience. The criteria presented in this report are intended for planning purposes. A summary of our conclusions is presented below. SUMMARY OF CONCLUSIONS 1. We discovered no geological or geotechnical constraint that would preclude the planned site development. The subsoil conditions are in general favorable for the proposed residential development. Areas of potential geologic hazard to be avoided or mitigated are discussed in our geologic hazard investigation (our Job No. GS-2647, dated January 29, 1999). 2. Our borings and test pits penetrated a surficial mantle of organic sand and c-lay underlain by dense to very dense, moist, silty to clayey gravels with cobble and boulder with thin to moderately thick lenses MELROSE CORPORATION CORYELL RANCH 1 CTUT GS-2647, PART 11 Cf� of medium dense to dense, silty to clayey sands with gravels and occasional cobbles. A 3.6 feet thick and 1 foot thick layer of silty to sandy clays were found in our TH-3 and TP-4, respectively, below the organic soils, above native gravels. 3. The natural clays were judged to be moderately compressible. The natural gravels and sands were judged to possess a low consolidation potential. 4. We anticipate spread footings placed on native gravels will be the recommend foundation type for the majority of lots. Extending of footing excavations to gravels and sands or removal of clays and replacement with structural fill built with on site gravels or sands may be recommended where clays are found at footing elevations. Detailed soils and foundation investigations should be performed on a lot by lot basis to determine the appropriate foundation type and to develop design criteria. 5. Preliminary data indicates concrete slabs -on -grade floors placed on the gravels or sands will perform satisfactory if the soils below slabs are not wetted. Where clays occur at floor subgrade elevation it may be recommended to remove and replace the upper 1 to 2 feet of the clay with granular structural fill. 6. The gravels and sands will provide good subgrade support for pavements and were found at planned subgrade elevations should result in economical, minimum thickness pavement sections. Thicker pavements or removal of 12 to 18 inches of clay and replacement with gravels and sand as a subbase layer may be recommended in areas where clays are found at planned subgrade elevations 7. Control of surface drainage is important to the performance of foundations and interior and exterior slags -on -grade. Surface drainage should be designed to provide rapid removal of surface runoff away from buildings and roads. SITE DESCRIPTION The site consists of the Coryell and Tomcat Ranches. Coryell Ranch is an approximately 272 acre parcel located in the Roaring Fork River Valley approximately one mile northwest of the Town of Carbondale. The confluence of the Roaring Fork and Crystal rivers is at the east central part of the property. Tomcat Ranch is an approximately 8 acre parcel of land located between Coryell Ranch and the MELROSE CORPORATION CORYELL RANCH 2 CTUT GS-2647, PART 11 confluence of the Crystal and Roaring Fork rivers to the east. The Crystal River is along the southeast property boundary. The Roaring Fork River is congruent with the north property boundary. An abandoned railroad grade is aligned through the site from the northwest to southeast. Some single family residential homes are on land adjacent to the northwest and east. County Road 109 is aligned through the south part of the property. Irrigated pasture land is on property above the site to the south. Topographically the site can be visualized as several broad, gently undulating terrace surfaces that step down to the Roaring Fork River at the north part of the property and the Crystal River at the southeast part of the property. An upper terrace is on adjacent property above the site to the south. From the upper terrace ground surfaces drop approximately 150 to 200 vertical feet down steep slopes with gradients of approximately 40 to 50 percent. The terraces that make up the site are separated by comparatively small vertical distances generally on the order of 20 to 30 vertical feet. Terrace surfaces slope to the north and east at gentle grades of 2 to 4 percent. Ground surfaces step down from upper terrace surfaces to the lower levels which are adjacent to the Roaring Fork and Crystal rivers. At the north part of the site along the Roaring Fork River the terrace steps down to the lower level at approximately 10 to 20 percent. At the central part of the site the terrace surface drops abruptly approximately 20 to 40 vertical feet down steep grades of approximately 30 to 50 percent to the Roaring Fork River. At the southeast part of the site the step down to the lower level adjacent to the Crystal River is approximately 40 to 50 vertical feet at a grade of approximately 50 percent. Several ponds are on the lower terrace at the north part of the property. The property has been used for irrigated pasture and haying operations. Vegetation consists of irrigated grasses and weeds. Oak brush, sage and weeds are prevalent in non -irrigated areas and mature trees are common along the banks of the Roaring Fork and Crystal rivers. MELROSE CORPORATION cORYELL RANCH 3 CTUT GS-2647, PART 11 PROPOSED DEVELOPMENT The proposed development will consist of two areas; the "River Club" and "Coryell Ranch". The River Club will be "higher end" single family residences at the north and west parts of the property. Coryell Ranch will be "obtainable housing" located in the southeast part of the property. Total number of residential units will be approximately 70. Water features, parks and open space areas will be incorporated into the development. Roadways and utilities will be constructed. Water and wastewater systems will be centralized and may be provided by connecting to existing systems on adjacent developments or may be provided on site. SUBSURFACE CONDITIONS Subsurface conditions were investigated by drilling eleven (11) exploratory borings and excavating eight (8) exploratory test pits at the approximate location shown on Figure 1. Our borings were drilled using a truck mounted drill rig and 4- inch diameter, continuous flight auger. Exploratory test pits were excavated with a large trackhoe. Subsurface exploration operations were directed by our representative who logged the soils and obtained samples for laboratory testing. Graphic logs of the soils found in our borings and test pits and results of field penetration resistance tests are presented on Figures 2 through 5. Penetration resistance tests were performed in borings by driving a modified California sampler or standard barrel sampler with a 140 pound weight falling 30 inches. Local experience indicates penetration resistance tests using a California sampler are similar in magnitude to the results of a standard penetration test. The modified California sampler results in a 2-inch diameter by 4 inch long sample suitable for many laboratory tests. Samples obtained from our borings and test pits were returned to our laboratory where they were visually classified and typical samples MELROSE CORPORATION CORYELL RANCH 4 CTLrr GS•2647, PART 11 selected for testing. Laboratory test are presented on Figures 4 through 8 and summarized on Table 1. Our borings and test pits penetrated a surficial mantle of organic sand and clay underlain by dense to very dense, moist, silty to clayey gravels with cobble and boulder and thin to moderately thick lenses of medium dense to dense, silty to clayey sands with gravels and occasional cobbles. A 3.5 feet and a 1.0 foot thick layer of silty to sandy clays were found in our TH-3 and TP-4, respectively below the organic soil, above native gravels. The following paragraphs describe the soils in more detail. la s Comparatively thin lenses of medium stiff to stiff, moist, sandy to silty clays were found at our TH-3 and TP-4 locations. Geologic reports generally refer to these soils as colluvium. The soils are the result of weathering and downslope movement of deposits of the parent sedimentary rock. A clay sample subjected to one dimensional swell/consolidation testing to judge volume change potential possessed a low consolidation potential. Natural moisture content was 18.9 percent and dry density was 107 pcf. The clays may be capable of supporting light foundation loads and may result in relatively high lateral loads on foundation walls. Gravels and Sands Gravel soils were found at all borings and pit locations. The gravels were predominantly silty to clayey with cobbles and boulder with occasional thin to moderately thick silty to clayey sand lenses with gravel and occasional cobble. The gravels were dense to very dense and moist. Drilling in dense gravel alluvium with auger equipment was difficult due to cobbles and boulders and drilling refusal was encountered in most borings. We performed a large scale gradation on a combined sample from several borings and test pits. The dried sample weight was 3288 MELROSE CORPORATION CORYELL RANCH 5 CTLr7 GS-2647, PART 11 pounds. The sample contained approximately 72 percent boulder, cobble and gravel (larger than No. 10 sieve), 23 percent sand (No. 200 sieve to No. 10 sieve) and 5 percent silt and clay sized particles (passing No. 200 sieve). The gravels are capable of supporting moderate to high foundation loads. Lateral loads on walls will be lower where the gravel soils are used as backfill then where clay backfill is used. G ound Wat r Ground water was not found in our exploratory borings or test pits the day of drilling or excavation. The exploration was in the winter prior to heavy spring runoff period. The ground water level may rise during, and for a period after, spring snow melt. A perched water table could develop. We installed PVC pipe at several locations throughout the site to allow future measurements to ground water. SITE DEVELOPMENT The following section presents recommendations and discusses road building and utility installation. overlot Gradin and Raad ;radinci Grading plans were not prepared at this writing. Because the natural topography is comparatively flat overiot grading is anticipated to be minimal. Where earthwork is required to level the ground surface it appears maximum cuts and fills will generally be on the order of 10 feet. Thicker fill (near 20 feet) will likely be required to build road embankments to provide access from County Road 109 to interior subdivision roads. The majority of our exploratory borings were terminated on large cobbles or boulders. Boulders to 4 feet in diameter were observed in test pit excavations. We MELROSE CORPORATION CORYELL RANCH G CTL/T GS-2647, PART 11 believe earthwork can be accomplished with large earthmoving equipment such as D-8 dozers with ripper blades and trackhoes. The majority of subgrade for interior subdivision roads will be native gravels. These gravels will provide very good subgrade support for pavements. Areas of cut to reach road subgrade elevations and excavations for water features should provide a significant amount of gravel which is an excellent soil to use to build road embankments with. Areas to receive fill must be properly prepared. Prior to fill placement, all vegetation, and soft or organic soils should be removed. "Topsoil" is probably 8 to 10 inches thick over much of the road alignments. Subgrade soils in fill areas should be scarified, moisture conditioned to within 2 percent of optimum moisture content and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698). The on -site gravels free of organics or rock larger than 6 inches in diameter or other deleterious materials can be used as fill to build road platforms. Fill part of overlot grading or road building should be placed in 8 inch maximum, loose lifts, moisture conditioned to between 2 percent below to 2 percent above optimum moisture content and compacted to at least 95 percent of maximum ASTM D 698 dry density. Fill placed on steeper cross slopes between terrace benches should be placed on excavated benches. The benches should be 8 to 12 feet wide to allow for heavy compaction equipment. Maximum bench height should be equal to or less than bench width. Placement and compaction of fill should be observed and tested during construction. The upper three feet of fill below road subgrade should be with the native gravels after passing through a 3-inch diameter "grizzly" screen. Areas of fill deeper than 3 feet below the planned subgrade can be with native gravels with a maximum size of 6 inches. Where fills are below roads and are 10 feet or more thick, the fill should be allowed to "cure" throughout at least one winter and MELROSE CORPORATION CORYELL RANCH 7 CM GS-2547, PART 11 tGr spring prior to placement of pavement. This will allow the majority of consolidation to occur and not adversely effect the pavement surface. Utint Construction Utility trenches should be sloped or shored to meet local, State and Federal safety regulations. Based on our subsurface exploration,, we believe the gravels are Type C based on OSHA standards. OSHA recommends temporary construction slopes no steeper than 1.5 to 1 (horizontal to vertical). Excavation slopes specified by OSHA are dependent upon types of soils and groundwater conditions encountered. Seepage and groundwater conditions in the trench may down grade the OSHA soil type. Contractors should identify the soils encountered in excavations and refer to OSHA standards to determine appropriate slopes. Excavations deeper than 20 feet need to be designed by a professional engineer. PRELIMINARY BUILDING CONSIDERATIONS PreI+miriary Etit idins Consideratipns The predominant near surface soils are silty to clayey gravels with cobble and boulder with some interbedded sand lenses. We anticipate native gravels will be found at foundation grades at a large percentage of the building lots. The gravels are judged to be slightly compressible when the moisture content increases significantly and light to moderate loads, as normal with the type of construction planned, are applied. Buildings on the majority of lots can be founded with conventional spread footings on native gravels. In random areas native clays will be found at foundation elevations. Excavation to basement depths will likely remove the clays and expose gravels on some lots where clays are found. Where clay is found at lower level or MELROSE CORPORATION CORYELL RANCH $ CTUT GS•2647, PART 11 basement level foundation elevations it is most likely that foundation recommendations will be to extend footing excavations to expose the native gravel or to over excavate the clays to the gravel surface and replace the removed clays with granular structural fill to planned footing elevations. The structural fill should be the native gravels after passing a 3 inch diameter "grizzly" screen. Footings placed on the native gravels or on granular structural fill can be sized with a maximum allowable soil pressure in the range of 3000 to 5000 psf. Interior Floors and E erior Slabs-3n-Grade Excavations at the majority of the lots will expose silty to sandy gravels with some sand lenses. We anticipate slabs -on -grade floor construction on the native gravels or sands will be appropriate. A minimum of 4-inch thick layer of free draining gravel should immediately underlie slabs constructed below grade. This material should consist of maximum 2-inch diameter aggregate with less than 50 percent passing the No. 4 sieve and less than 3 percent passing the No. 200 sieve. The free draining gravel will aid in drainage below the slabs and should be connected to a perimeter underdrain system. This layer will also act as a leveling course to provide a flat surface on which to place slabs. Structurally supported floors with a crawlspace below the floor, above the native soils will likely be recommended on lots where clay is exposed at floor slab elevation and extends more that a couple feet below the bottom of slab. An alternative would be to remove the clay and replace the soil with a structural fill built with the native gravels and sands after passing through a 3 inch diameter grizzly screen. Floor slabs should not be supported partially on man-made fill and partially on native soils or partially on clays and partially on gravels.. To reduce the adverse effects of differential slab movement, floor slabs should be separated from all MELROSE CORPORATION CORYELL RANCH 9 CTUT GS-2647, PART 11 bearing walls and columns with expansion joints. Control joints should be used in floor slabs to reduce damage due to shrinkage cracking. Below Grade Walls We do not anticipate subsurface conditions which will preclude basement construction. Basement excavations will encounter gravels and to a lesser extent clays. Ground water will rise during and after snow melt in the spring. It should be anticipated that any excavation on these lots may expose perched ground water during the spring runoff. Flood irrigation above the site also effects the ground water level in building excavations. Foundation walls will be subjected to lateral earth pressures. Foundation walls at the back of some buildings may act a retaining walls. These walls are restrained and cannot move, therefore, they should be designed for the "at rest" lateral earth pressure. We believe an equivalent fluid density in the range of 45 to 55 pcf will be recommended to design for the "at rest" case. We recommend backfill behind the walls be the on -site gravels and sands 3 inches in diameter or less and compacted to at least 95 percent of standard Proctor maximum dry density (ASTM D 698). Preliminary lateral earth pressure values do not include allowances for sloping backfill, hydrostatic pressure of surcharge loads. Water from surface run-off (precipitation, snow melt, irrigation) frequently flows through backfill placed adjacent to foundation walls and collects on the surface of the comparatively impermeable soils occurring at the bottom of foundation excavations. This can cause damp or wet conditions in basement and crawl space areas of buildings. To reduce the accumulation of water we will most likely recommend that a foundation drain be placed adjacent to foundation walls. The drain should consist of a 4-inch diameter open joint or slotted PVC pipe encased in free draining gravel. Drain lines should be placed at each level of excavation and at least 1 foot below the lowest adjacent finished grade, and sloped at a minimum 1 MELROSE CORPORATION CORYELL RANCH 10 CTLIT GS•2647, PART 11 percent to a positive gravity outfall. Free draining granular material used in the drain system should consist of minus 2-inch aggregate with less than 50 percent passing the No. 4 sieve and less than 3 percent passing the No. 200 sieve. The drain gravel should be at least 1.5 feet thick. EARTH RETAINING STRUCTURES Free standing retaining structures may be required. Several types of retaining structures are used in the area and could be considered. Some examples of different types of walls are listed below: Anchor Walls Tied -back walls tied back via soils nails or earth anchors Steel pile and lagging Continuous drilled pier walls Conventional Retaining Walls Reinforced concrete Crib walls Internally Stabilized Systems Mechanically stabilized earth (MSE) structures Friction reinforcement systems A "rock wall" is generally a landscaping feature. Rock walls greater than approximately 6 feet in height, in our opinion, do not provide adequate resistance to lateral loads. If rock walls are used, we suggest a maximum height of 6 feet. The wall should be battered at an angle of approximately 60 degrees. The width of the base of the wall should be at least'/z the height with a wall face no steeper than 314 to 1 (horizontal to vertical). MELROSE CORPORATION CORYELL RANCH 1 CTL(T GS-2647, PART 11 Retaining walls will be subjected to lateral earth pressure from wall backfill and surcharges. The lateral load on the wall is a function of wall movement. If the wall can move enough to mobilize the internal strength of the backfill, with movement and cracking of the surface behind the wall, the wall can be designed for the "active"earth pressure. If ground movement and cracking is not permitted, the wall should be designed for the "at rest" earth pressure. We suggest an equivalent fluid density in the range of 40 to 50 pcf be used to design for the "active" case and an equivalent fluid density of 45 to 65 pcf be used to design for the "at rest" cast. The values are for preliminary wall designs. The design criteria should be confirmed prior to construction. An equivalent fluid density of 250 to 300 pcf can be used for the "passive" case. Backfill of the walls is likely to be on the on -site gravels. These soils are generally not free draining. When compacted, these materials will probably have compacted moist density in the range of 130 pcf. The angle of internal friction will probably be on the order of 30 to 34 degrees. These soils exhibit small cohesive strength, and cohesion should be neglected in preliminary designs. Lateral earth pressure values do not include allowances for sloping backfill, hydrostatic pressures or surcharge loads. A foundation drain should be placed next to the foundation of any retaining wall. The 1 to 2 feet of backfill directly behind the wall should be a "clean" gravel imported to the site or a man made drain board product and provided with positive gravity discharge. nx )r Subdivision Roads Subgrade soils will generally be silty to clayey sands. We estimate a Hveem Stabilometer Value (R-value, ASTM, D 2844, AASHTO T-1998) of 40 to 60. An equivalent daily load application (EDLA) of 8 which represents a design equivalent single axle load (ESAL) of 58,400 for a 20 year design period was used to determine the preliminary pavement sections for interior subdivision roads. Based on our calculations, we recommend 5.0 inches of full depth asphalt or 3.0 inches of asphalt underlain by 6.0 inches of compacted aggregate base where the subgrade MELROSE CORPORATION CORYELL RANCH 12 CTL r GS-2647, PART 11 I is gravels. Where clay subgrade occurs we believe appropriate pavement section will likely be 6.0 inches of full depth asphalt or 3.0 inches of asphalt underlain by 9 inches of aggregate base course. A geotextile fabric is recommended between clay subgrade and aggregate base. Trash pick-up areas should be paved with 6.0 inches of Portland cement. Prior to paving, the entire pavement subgrade should be scarified, moisture conditioned to within 2 percent of optimum moisture content and compacted to at least 95 percent of the standard Proctor maximum dry density (ASTM D 698). Fill below pavement to achieve the subgrade elevation should be moistened to within 2 percent of optimum moisture content and compacted to at least 95 percent of ASTM D 698 maximum dry density. Before placing base course, full depth asphalt or concrete, we recommend the entire subgrade surface be proof rolled with a (18 kipslaxle) heavy pneumatic tired vehicle such as a loaded ten wheel dump truck. Areas which deform excessively should be overexcavated and recompacted or otherwise stabilized. Concrete pavement will require careful material and construction control. Concrete should have a minimum Modulus of Rupture (flexual strength) of 600 psi. A laboratory mix design should have a compressive strength of at least 3750 psi. We recommend the concrete contain a minimum of 5.6 sacks of cement per cubic yard and between 5 and 7 percent entrained air. Colorado Department of Transportation Class P mix should satisfy the above requirements. if a combination section is used, the aggregate base course should have a minimum R value of 78. The base course should be moisture conditioned to near optimum moisture content and compacted to at least 95 percent of the modified Proctor maxim dry density (ASTM D 1557). Asphalt should have a total resistance (Rt) of at least 95 and should be compacted to 95 percent maximum Marshal density. We recommend the asphalt be designed with at least 1650 pound Marshall Stability. The oil content, void ratio and gradation need to be considered in the design. MELROSE CORPORATION CORYELL RANCH CTUT GS-2647, PART 11 13 SURFACE DRAINAGE Surface drainage will need to control and channelize surface water down, around and away from roads and buildings. Seasonal surface flows through building footprints need to be re-routed away from the buildings. Any areas of potential ponding water should be eliminated. The performance of foundations and concrete flatwork is influenced by moisture conditions in the subsoils. Wetting of foundation soils can be reduced by grading the ground surface to cause rapid run-off of water away from the buildings. Wetting or drying of the open foundation excavations should be avoided. The ground surface surrounding the buildings should be sloped to drain away from the buildings in all directions. We recommend a slope of at least 12 inches in the first 10 feet. Roof downspouts and drains should discharge well beyond the limits of all backfill. Buried discharge lines are not desirable. LIMITATIONS The criteria in this report is preliminary and not for construction. The criteria is intended for use in developing preliminary designs. Design level criteria can only be developed and published after review of grading and building plans for individual lots. Individual site specific investigations will be needed. Our exploratory borings and test pits were spaced to obtain a reasonably accurate picture of the subsurface. Variations in these subsurface conditions not shown by our exploratory borings will occur. Our report was based on conditions disclosed by our exploratory borings and test pits, results of laboratory testing, engineering analysis and our experience. Criteria presented reflects anticipated construction as we understand it. MELROSE CORPORATION CORYELL RANCH 14 CTLIT GS•2647, PART 11 1�J This investigation was conducted in a manner consistent with that level of care and skill ordinarily exercised by members of geotechnical engineers currently practicing under similar conditions in the locality of this project. No other warranty, express or implied, is made. If we can be of further service or if you have questions regarding thi eport, please call. 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GS 2647 .0 D 001 D OD2 .005 ,009 019 037 074 149 297 590 1 18 2.0 2 3a + 78 9 52 042. DIAMETER OF PARTICLE IN 1.1U METERS SANDS CLAY (PLASTIC) TO SILT (NON -PLASTIC) FINE Sample Of GRAVEL SILTY (GMA__ From TH f - AT 4 FEET rm_ ,M 191 361 76-2. 127 2200 GRAVEL COARSE FINE I COARSE I COMES GRAVEL 45 % SAND 43 % SILT & CLAY 12 % LIQUID LIMIT - % PLASTICITY INDEX % HYDROMETER ANALYSIS SIEVE ANALYSIS HR. 7 HR. ME EAAINGS 45 MIN 15 MIN, 60 MIN19 MIN, + MIN. I MIN. USN+ '200 '100 '50 '40'30 '16 -Iola '4 3w 0'4' 1%- S r 8'0 100 - -1 ,. - -(-. 80 70 40 - .- _ ... .- c ; SD u 50 f 40 — - -- - sD go ...... }I Do O DOS - ��. 1-19 2.02.38 4.76 9.52 .p.42 191 381 782 121200 52 Dp�__ I QOD2 DIAMETER OF PARTICLE IN MILLIMETERS CLAY (PLASTICI TO SILT (NON -PLASTIC) FINE MEDIUM COARSE I FINE COARSE CC8"S sample of SAND. GRAVEL 34 % SAND 44 % From 7N-2 - A T 4 FEET -- - SILT 8 CLAY 22 %LIQUID LIMIT - - - PLASTICITY INDEX Gradation JOB NO. '64 Test FIG. 5 WYCIROMETER ANALYSIS S{cV r ANALYSIS CLEAR SQUAREOPENNGS 25 HR. 7 HR T E REJ+41NG5 U S- 57'AHDARD SERIES '200 '100 '50'40'30 .16 "10'& '4 318' 314' 9' S' 45 MIN 15 MIN 6D MIN 19 MIN 4 MIN 1 MIN. —1;5' 0 90 20 80 --... .. w- ... ,. .. ..... -- ..�1 •y 40 --- ---- 78 17 - - _ -- 80 _ ' Q + _074 fig 297Q S9fl� I.19 2A 2,58 4.76 _ inn 9 52 39 I 36.1 i@ 7 12152i90 0 002 009 019 �D07� 001 .ODS DIAMETER OF PARTICLE IN MILLIMETERS CLAY (PLASTIC) TO SILT (NON -PLASTIC) Sample of GRAVEL SlLTY_CGMjJ From TH 3 - AT 9 FEET GRAVEL _ 53 % SAND_ 38 % SILT S CLAY 9 % LIQUID LIMIT �- % PLASTICITY INDEX HYOROMETER AXALYSIS SIEVE ANALYSIS u ING9 HR 7 HR. Ir RE:&Q OS U•S MIN. '2D0 '100 A SERI 'S0 .4070 16 '10'8 '4 3!8' 314' 1 '/.' 3` Q 45 MIN. 15 MIN 60 MIN 19 MIN A MIN- t 10 20 CM 00 70 30 F�.�.--• - . _ _ _ .. F - .... .. I . I �. au 10 Qpq�..:pp[sZ iC6 Q09 019 0:7 1374---149 1137L 7,0238•456 952, 19s 561 110 T6? i2IS? :5901.19 DIAMETER OF PARTICLE IN MILLIMETERS SANDS GRnVEI_ CLAY (PLASTIC) TO SILT (NON -PLASTIC) FINE MEDIUM COARSE FINE COARSE COB[iLES % SAND 39 GRAVEL 1279 Sample of SAND, CLAYEY (SC) . � SILT &CLAY 49 % LIDUID LIMIT - From TH 5 - AT 9 FEET -- - _. PLASTICITY INDEX - Gradation JOB NO I:_ I Test FIG.6 n DRCµETE: A; i lis SIEVE ANALYSIS TIMER NGS U S" STANDARO SERIES CLEAR S"RF CPENMS 25 MR. 7 MR, a 3B $ 4 1 X' S rw a' 45 MIN f 5 MIN. 60 MIN.19 MIN 4 MIN I MIN. '200 '100 'a0'40 �0 ' 16 ' 10'8 `�T 0 10 - 20 TO L - - - - 60 a w.. --:, 70 SO - .. 9D •.. 019 937 0-(A 149 .297 .590 1.19 2"0 2.3A 478 952 191 ?8 1 762 121-P 001 0.002 DOS 009 O.d2 DIAMETER OF PARTICLE IN MILLIMETERS AN GRAVEL CLAY (PLASTIC) TO SILT (NON•PLASTIC) FlNE MEDIUM COARSE FINE COARSE C06BLE5 Sample of SAND. SILTY r(M _ _ GRAVEL 38 0/0 SAND 52 TH $ A7 4 F1wET — SILT & CLAY 10 % LIQUID LIll+tkT - °A From — - PLASTICITY INDEX ~'/° r1YDiiOM1 ER Ai4ALYS15 SIEVE RNALYSIS HR, 7 HR. TIME EA>] ME NI 5 C< S N 4SMM.15MIN 66MIN19MIN, 41" 1 WN '200 •1D0 '50'40'M '1B '10'6 'd 778' 3w 1w D 100 10 20 b0 — - :. . _ ... _ 30 ° 2 70 - i 60 - - 70 30 1- 80 90 to 0061 0.4 Z 065 Mg019 , 037 074 .14- —2970 590 1.13 2 0 2.38 4 70 1 361 76,Y 12 52200 DIAMETER OF PARTICLE IN MLL1METFR5 SANDS GRAVEL CLAY (PLASTIC) TO SILT NON -PLASTIC) FINE MEDIUM COARSE FINE COARSE COBBLES GRAVEL % SAND % Sample of SILT &CLAY °1° L10lJlp LIMIT From — . — _ _ — - — PLASTICITY INDEX °Ie Gradation JOB NO. Test FIG- 7 �iYflRpMETER ANALYSIS SIEVE ANALYSIS [45 HR. 7 HR TI1t7E R� US STANDARD SERIES CLEAR $OUAitF OPEHfNGs MIN 15 MIN fi0 MIN 19 MIN. 4 MIN. 1 MIN, '200 'IDO 'SO -40'30 ' 16 '10.6 '4 3183IA' 1!,- 3 5'fi8'p—. .— _ .. .. 8t1 30 - - 40 40 7— TO �0 O011 0.002 005- 009• ••019..•A37�.074 140 297042590 IA9 2.02A C76 0'.r2 191 N1 76.2 127 DIAMETER OF PARTICLE IN MILLIMETERS SANDS GRAVEL CLAY (PLASTIC) TO SILT (NON -PLASTIC) FINE MEDIUM COARSE FINE COARSE COBBLES Sample of NAVEL SILTY - GRAVEL 72 % SAND 23 % �' ^Y� — - SILT & CLAY 5 1 LIQUID LIMIT - % From COMBINE❑ — PLASTICITY INDEX _ - y % HYDRQMETER RNALY5IS SIEVE ANALYS 5 HR. 7 HR. T€ME fiEF01ldGS L S .lid S I S -4 31W W IW 3' 6_b' e'0 45 MIN_ 15 MIN 60 MIN 19 MIN a idW, 1 WIN '200 100 'S0'40 *30 16 106 100 — -- .. ! -. g0 20 so 30 p 50 So 60 --- 60 70 -- -. - •. -. _ • •19 100 0.007 , • 019 •-- p37 •074 • 1 <9 2970 590 t 2.0 2.38 a 78�9 S2 113.1 56.1 76.2 12ti P 002 00S 009 42 DIAMETER OF PARTICLE IN MILLMETERS SANDS GRAVEL CLAY (PLASTIC) TO SILT (NON -PLASTIC) FINE I MEDIUM COARSE I FINE I COARSE 1 COBBLES Sample of From GRAVEL % SAND % SILT &CLAY % LIQUID LIMIT_ PLASTICITY Gradation JOB No. µ ; Test FIG. 3 ti N N d Z m O 3 F.. Ln W H M 0 1 w Q.J CO ja m J LL. 0 cn m a W February 2, 1999 Melrose Corporation P.O. Box 21307 Hilton Head Island, SC 29925 Attention: Mr. Jack Best Subject: Additional Recommendations Slope Stability Evaluation Slopes Adjacent to County Road 109 Coryedl Ranch Garfield County, Colorado Job No. GS-2650 Gentlemen: We have viewed the most recently proposed building lot layout and performed additional evaluation regarding set -back distancefrom the north shoulder of County Road 109 and berm height as part of a plan to protect buildings from run out from a earth flowldebris flow event. The following paragraphs present results of our plan review and additional mitigation recommendations. We previously recommended a 200 feet setback from the road shoulder and a 5 to 6 feet high berm to contain and/or divert run off material. At the affordable housing area at the east end of the development some lots are closer than 200 feet to the road. Specifically Lots A2 thru A5 and Lots 18, 25, and 26 are partially within 200 feet of the road shoulder. Lot A-6 is completely within 200 feet of the shoulder. It is best if structures on these lots can be located at least 200 feet from the shoulder. An acceptable alternative would be to increase the berm height to at least 7 to 8 feet high to protect the buildings. A second alternative would be to elevate the building footprints at least 8 feet above the bottom of the road shoulder embankment. CTL/THOMPSON, INC. CONSULTING ENGINEERS 2.34 CI-Ni 1 N HI 4 GLENWOOD SPRINGS CoLORADO 81601 4 10701 945 2809 When the proposed final grading scheme for protecting structures is available we should meet with the owner, planner and civil engineer to review the plan and to allow comment. We appreciate the opportunity to work with you on this project. Please call if you have questions. Very truly yours, h Mariagd :dd:cd -:� ,r•• ;opies sent) MELROSE CORPORATION CORYELL RANCH Z JOB NO. GS-2650 March 2, 1999 Melrose Corporation P.O. Box 21307 Hilton Head Island, SC 29925 Attention: Mr. Jack Best Subject: Additional Recommendations Containment/Diversion Berm Coryell Ranch Garfield County, Colorado Job No. GS-2650 Gentlemen: We have viewed the most recently proposed building lot layout (dated March 1, 1999) and performed additional evaluation regarding set -back distance From the north shoulder of County Road 109 and berm height as part of a plan to protect buildings from run out from an earth flowidebris flow event. The following paragraphs present results of our plan review and additional mitigation recommendations. We previously recommended a 200 feet setback from the road shoulder and a 5 to 6 feet high berm to contain and/or divert material from an earth flow/debris flow event (our letter dated January 18, 1999). At the affordable housing area at the east end of the development some lots are closer than 200 feet to the road. Specifically Lots A2 thru A5 and Lots 18, 20, 21, 25, and 26 are partially within 200 feet of the road shoulder. Lot A-6 is completely within 200 feet of the shoulder. An acceptable alternative to the above set back distance and berm height recommendations would be to increase the berm height to at least 7 to 8 feet high to protect the buildings. A second alternative would be to elevate the building footprints at least 8 feet above the bottom of the road shoulder embankment. At a March 1, 1999 meeting of design team members we were asked what the height of the berm should be at each of the two possible alternative alignments shown on Figure 1 as Alternative "A" and Alternative "B". At the Alternative "A" location which is directly adjacent to the road we recommended a 7 to 8 feet high berm. At the Alternative ,B" location we recommend a berm 7 to 8 feet tall adjacent CTUTHOMPSON, INC. CONSULTING ENGINEERS ,.� i,iIrri iiNwno O:-,I,mrJ(,:, t,tof0IIAUc):,,,.,,i r '"',""I.9u,.1 to the road decreasing in height to 5 or 6 feet at 200 feet from the road. The berm can be built with on site soils free of organic matter or other deleterious material. The top of the berm should be at least 4 feet wide and side slopes should be no steeper than 2 to 1 (horizontal to vertical). The berm fill should be moisture treated to within 2 percent of optimum moisture content and compacted to at least 90 percent of standard Proctor maximum dry density (ASTM D 698). When the proposed final grading scheme for protecting structures is available we should meet with the owner, planner and civil engineer to review the plan and to allow comment. We appreciate the opportunity to work with you on this project. Please call if you have questions. Very tru CT 0 , INC. oh, ec I ; P E. " Br kan4ber db:cd ( copies serif MELROSE CORPORATION CDRYELL RANCH JOB NO GS 2650