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Home My WebLink About1.02 Soil studySEA TON SUBDIVISION COMBINED PRELIMINARY PLAN & FINAL PLAT APPLICATION EXHIBIT B SOIL STUDY Chen@Northern, Inc. Cv,s '.')rjEngineersaro Sr,ieitlisls 5080 Poad 154 Gegrrcoo Springs, Colorado 81601 303 3=57458 303 945-2363 Facs.m le SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE 13 -ACRE PARCEL SOUTH OF CHELYN ACRES FOUR -MILE ROAD GARFIELD COUNTY, COLORADO JOB NO. 4 481 92-1 NOVEMBER 3, 1992 PREPARED FOR: DON SEATON CIO JOHN BAKER, ARCHITECT P.O. BOX 448 CARBONDALE CO 81623-0448 A member 01 the HH Igroup of companies Chen@Northern, Inc. November 3, 1992 Don Seaton c/o John Baker, Architect P.O. Box 448 Carbondale CO 81623-0448 Consu 1.19 Eng.necrs and Sc en fists 5080 Road 154 Glenwood Springs. Colorado 81601 303 945-7458 303 945-2363 FacsFmde Subject: Subsoil Study for Foundation Design, Proposed Residence, 13 -acre Parcel, South of Chelyn Acres, Four -Mile Road, Garfield County, Colorado. Job No. 4 481 92-1 Dear Mr. Seaton: As requested, we have conducted a subsoil study at the subject site, located south of Chelyn Acres, north of Four -Mile Road, Garfield County, Colorado. Subsurface conditions encountered in the exploratory borings drilled in the proposed building area consist of 8 1/2 to 11 feet of medium dense to loose, silty sand overlying hard siltstone bedrock. Groundwater was encountered in Boring 2 at a depth of 8 feet below the ground surface at the time of drilling. The proposed residence can be founded on spread footings placed on the natural silty sand subsoils and designed for an allowable bearing pressure of 1000 psf. Footings could also be placed on the lower siltstone bedrock and designed for an allowable bearing pressure of 5000 psf. The report which follows describes our investigation, summarizes our findings, and presents our recommendations. It is important that we provide consultation during design, and field services during construction to review and monitor the implementation of the geotechnical recommenda- tions. If you have any questions regarding this report, please contact us. Sincerely, CHEN-NORTHERN, INC. Daniel E. Hardin, P.E. DEH/ec Rev. By: SLP A mn,hne n1 tl-n nnpr,ni pnm r�ii me • TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY 1 PROPOSED CONSTRUCTION 1 SITE CONDITIONS 2 FIELD EXPLORATION 2 SUBSURFACE CONDITIONS 3 FOUNDATION BEARING CONDITIONS 4 DESIGN RECOMMENDATIONS 4 FOUNDATIONS 4 FOUNDATION AND RETAINING WALLS 5 FLOOR SLABS 7 UNDERDRAIN SYSTEM 7 SITE GRADING 8 SURFACE DRAINAGE 9 LIMITATIONS 9 FIGURE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 AND 5 - SWELL -CONSOLIDATION TEST RESULTS FIGURE 6 - GRADATION TEST RESULTS TABLE I - SUMMARY OF LABORATORY TEST RESULTS CLASSIFICATION OF SOILS FOR ENGINEERING PURPOSES Chen €Nnt-thern Inc. PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on a 13 -acre parcel of land south of Chelyn Acres, Four -Mile Road, Garfield County, Colorado. The project site is shown on Fig. 1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our proposal for a geotechnical engineering study to Don Seaton, dated August 24, 1992. We previously conducted a geotechnical site reconnaissance at the site under Job No. 4 481 92, dated August 27, 1992. A field exploration program consisting of exploratory borings was conducted to obtain information on subsurface conditions. Samples obtained during the field exploration were tested in the laboratory to determine the engineering characteristics of the on-site soils. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. The results of the field exploration and laboratory testing are presented in the report. This report has been prepared to summarize the data obtained during this study and to present our conclusions and recommendations based on the proposed construction and the subsoil conditions encountered. Design parameters and a discussion of geotechnical engineering considerations related to construction of the proposed residence are included in the report. PROPOSED CONSTRUCTION The proposed residence will be a two-story wood frame structure with a walkout lower level. Ground floor will be slab -on -grade. Grading for the structure is assumed to involve cut (hen€/Nni-tiiern Inc,. • -2 depths between about 10 to 12 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. If building loadings, location or grading plans change significantly from those described above, we should be notified to reevaluate the recommendations contained in this report. SITE CONDITIONS The general site conditions were the same as those described in our previous letter. The building area slopes moderately to steeply to the east at grades of 10% to 40%. Four -Mile Creek is located just east of the building area. Vegetation consists of cottonwood trees, scrub oak, brush and grass. Scattered gray basalt boulders were visible on the ground surface. FIELD EXPLORATION The field exploration for the project was conducted on September 16, 1992. Two exploratory borings were drilled at the locations shown on Fig. 1 to evaluate the subsurface conditions. The borings were advanced with 4 -inch diameter continuous flight augers powered by a track -mounted CME -45 drill rig. The borings were logged by a representative of Chen -Northern, Inc. Samples of the subsoils were taken with 1 3/8 -inch and 2 -inch I.D. spoon samplers. The samplers were driven into the subsoils at various depths with blows from a 140 -pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or ChenNrrtliern 1nc'. • 3 consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Fig. 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS The subsoil conditions encountered at the site are shown graphically on Fig. 2. The subsoils consist of about 2 feet of topsoil overlying medium dense to loose, silty to very silty sand. Hard siltstone bedrock was encountered below the sand at depths of 8 1/2 to 11 feet and extended to the maximum depth explored, 20 1/2 feet. Laboratory testing performed on samples obtained from the borings included natural moisture content, density, Atterberg limits and gradation analyses. Results of consolidation testing performed on relatively undisturbed drive samples of the silty sands, presented on Figs. 4 and 5, indicate low compressibility under conditions of light loading and wetting with moderate to high compressibility under increased loading after wetting. A small collapse potential was observed for two of the samples when wetted under light load. Results of gradation analyses performed on small diameter drive samples (minus 1 1/2 -inch fraction) of the natural granular soils are shown on Fig. 6. Atterberg limits tests on a cuttings sample of the siltstone bedrock indicates the bedrock is of low plasticity. The laboratory testing is summarized in Table L Free water was encountered in Boring 2 at the time of drilling at a depth of 8 feet. The upper subsoils were slightly moist to moist. Chen aNnrt1iern.Inc f i nc..n,nn F�rnw.r..rc and Sr nn65lc -4 FOUNDATION BEARING CONDITIONS Conventional spread footing foundations should be suitable for support of the residence. Two bearing conditions were considered; footings placed on the upper, medium dense to loose silty sand and footings placed on the lower, siltstone bedrock. Footings placed on the bedrock should experience minimal settlement. Footings placed on the silty sand could experience differential settlement, especially if the soils were to become wetted. Placing the footings on a common bearing stratum should help limit differential settlement. Placing the footings entirely on the siltstone bedrock is the lower settlement risk alternative. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsoil conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural granular soils or siltstone bedrock. The design and construction criteria presented below should be observed for a spread footing foundation system. The construction criteria should be considered when preparing project documents. 1) Footings placed on the undisturbed natural granular soils should be designed for an allowable soil bearing pressure of 1000 psf. Based on experience, we expect initial settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. Additional differential settlement on the order of 1 inch is indicated if the Chent1Northern_ Inc. ('iuI.,,,u. q. Fnrn.ir.•ic aiuI St'4'l1115(5 • -5 bearing soils become wetted. Footings placed entirely on the underlying siltstone bedrock can be designed for an allowable bearing pressure of 5000 psf and should experience minimal settlement. 2) The footings placed on soil should have a minimum width of 16 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 36 inches below exterior grade is typically used in this area. 4) Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) All existing topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the natural granular soils or bedrock. If water seepage is encountered, the footing areas should be dewatered before concrete placement. 6) A representative of the soil engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of 50 pcf for backfill consisting of the on-site granular soils. Cantilevered retaining structures which are separate then€ Nnrthern Inc. Cnntii,en.n F.1lvr M.4C,vrxl Sj'a+rdislc 6 from the residence and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of 40 pcf for backfill consisting of the on-site granular soils. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum standard Proctor density at a moisture content near optimum. Backfill in pavement and walkway areas should be compacted to at least 95% of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected even if the material is placed correctly and could result in distress to facilities constructed on the backfill. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.35. Passive pressure against the sides of the footings can be calculated using an equivalent fluid unit weight of 250 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the Chen rNnrthern.Inc. (•�u��„i��r�y 111.01.,. •.c ..in Sr t'r rIS19 -7 ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be a granular material compacted to at least 95 % of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly Ioaded slab -on -grade construction. There is a risk of some floor slab settlement if the upper sands were to become wetted. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer bases on experience and the intended slab use. A minimum 4 -inch layer of free - draining gravel should be placed beneath below grade slabs to facilitate drainage. This material should consist of minus 2 -inch aggregate with less than 50 % passing the No. 4 sieve and less than 2% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95 % of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on-site sands devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM Free water was encountered during our exploration in Boring 2 at a depth of 8 feet. It has been our experience in mountainous areas that local perched groundwater may also develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can Chen Nni-thern.Inc. 8 create a perched condition. We recommend below grade construction, such as retaining walls, crawl space and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free -draining granular material. The drain should be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to a suitable gravity outlet. Free -draining granular material used in the underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least 2 feet deep. SITE GRADING The risk of construction induced slope instability at the site appears low provided the building is .located as planned and cut and fill depths are limited. We assume the cut depth for the basement level will not exceed one level, about 10 to 12 feet. Fills should be limited to about 8 to 10 feet deep. Water encountered in the cuts will increase the risk of slope instability. Embankment fills should be compacted to at least 95% of the maximum standard Proctor density near -optimum moisture content. Prior to fill placement, the subgrade should be carefully prepared by removing all vegetation and topsoil and compacting to 95 % standard Proctor density. The fill should be benched into the portions of the hillside exceeding 20% grade. Permanent unretained cut and fill slopes should be graded at 2 horizontal to 1 vertical or flatter. The risk of slope instability will be increased if seepage is encountered in cuts and flatter slopes may be necessary. If seepage is encountered in permanent cuts, an investigation Chen Nni-thern. inc. Cnnu,ronn Fnn.n.s,•is n xl Stir+.nhsls 9 should be conducted to determine if the seepage will adversely affect the cut stability. This office should review site grading plans for the project prior to construction. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95 % of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. Free -draining wall backfill should be capped with about 2 feet of the on-site soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. LIMITATIONS This report has been prepared in accordance with generally accepted soil and foundation engineering practices in this area for use by the client for design purposes. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory Chen ONewthern. Inc. f nm �.n�i•n F,rnulr,..ro. -10(1 irurrdisR - 10 - borings drilled at the locations indicated on Fig. 1 and the proposed type of construction. The nature and extent of subsurface variations across the site may not become evident until excavation is performed. If during construction, fill, soil, rock or water conditions appear to be different from those described herein, this office should be advised at once so reevaluation of the recommendations may be made. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fill by a representative of the soil engineer. Sincerely, CHEN-NORTHERN, INC. 4.0,;L‘'0outiI RIEG/ fi, s y � Daniel E. Hardin, P.1i S 24443 E A1 1;.N. fi 'Y Reviewed By -, ,sSIONAI t",a , "olingIIHtIft0- S=PATA aw-u, Steven L. Pawlak, P.E. DEH/ec Chen€ Nnrthern inc. f exiu.iz.iw Fnn,nn..lc,,WI , �, iiII I¢ • • G 70 APPROXIMATE SCALE I" - 20' PROPOSED WATER FEATURE 4. BSc, • • PROPOSED POND i • FOUR MILE CREEK • \ • • • 6,370 GHQ • 6350 34-6 G 34 4 481 921 Chen Northern, Inc. LOCATION OF EXPLORATORY BORINGS Fig. Elevation Feet 6360 6355 6350 - 6345 - 6340 Boring 1 Elev. = 6358' 17/12 21/12 WC=6 DD=97 +4=3 -200=43 30/4 WC=11 DD=108 - 200=44 30/0 Boring 2 Elev. = 6356' 30/0 WC=2 - 200=60 Cuttings LL=23 Sample PI=6 • 6360— Proposed 360— Proposed 16/12 //Lower Floor Level 6355 18/12 WC=7 DD=105 +4=4 - 200=30 4/12 WC=22 DD=104 - 200=34 35/3 30/0 6335 6335 --- 6350 6345 6340 --- Note: Explanation of symbols presented on Fig. 3. Elevation - Feet 4 481 92-1 Chen0Northern, Inc. Logs of Exploratory Borings Fig. 2 LEGEND: 173 Topsoil; sand and silt, slightly clayey, organic, medium dense, slightly moist, dark brown. EdSand (SM); silty, loose to medium dense, slightly moist to wet, brown to reddish brown. Siltstone Bedrock; red, dry to slightly moist, (Morrison Formation). Relatively undisturbed drive sample; 2 -inch I.D. California liner sample. Drive sample; Standard Penetration Test (SPT), 1 3/8 -inch I.D. split spoon sample, ASTM D-1586. 21/12 Drive sample blow count; indicates that 21 blows of a 140 -pound hammer falling 30 inches were required to drive the California or SPT sampler 12 inches. =amrFree water level in boring.at time of drilling. NOTES: 1. Exploratory borings were drilled on September 16, 1992 with 4 -inch diameter continuous flight power :auger. Locations of exploratory borings were measured approximately by pacing from features shown on the site plan provided. . Elevations of exploratory borings were obtained by interpolation between contours on the site plan provided. . The exploratory boring locations and elevations should be considered accurate only to the degree implied by the method used. The lines between materials shown on the exploratory boring logs represent the approximate boundaries between material types and transitions may be gradual. Water level readings shown on the logs were made at the time and under the conditions indicated. Fluctuations in water level may occur with time. . Laboratory Testing Results: WC = Water Content (%) DO = Dry Density (pcf) +4 = Percent retained on No. 4 sieve -200 = Percent passing No. 200 sieve LL = Liquid Limit(%) PI = Plasticity Index (%) 4 481 92-1 ChenNorthern, Inc, Legend and Notes Fig. 3 Compression - % CAL) tv o VO CO .4 rn cn .a w N r o Moisture Content = 6 percent Dry Unit Weight = 97 pct Sample of: very silty sand From: Boring 1 at 3 feet .` �—___ Additional compression under constant pressure due to wetting . d 0.1 1,0 10 100 APPLIED PRESSURE — ksf 4 481 92-1 Chen Northern, Inc. SWELL -CONSOLIDATION TEST RESULTS Fig. 4 Compression - % Compression - % 0 1 2 0 1 2 3 4 0.1 1.0 10 APPLIED PRESSURE — ksf Moisture Content = 11 percent Dry Unit Weight = 1 08 pcf Sample of: very silty sand From: Boring 1 at 8 feet 0 ----------------1------t--------- Additional compression under constant ------"b,,,,,....rl ' • '1-- pressure to wetting due !!/—/;/ • No movement upon wetting 0.1 1.0 10 APPLIED PRESSURE — ksf 0.1 1.0 10 APPLIED PRESSURE — ksf 4 481 92-1 ChenONorthern, Inc, SWELL -CONSOLIDATION TEST RESULTS Fig. 5 Moisture Content = 7 percent Dry Unit Weight = 105 pcf Sample of: silty sand From: Boring 2 at 4.5 feet 0 Additional compression under constant ' • '1-- pressure to wetting due • 0.1 1.0 10 APPLIED PRESSURE — ksf 4 481 92-1 ChenONorthern, Inc, SWELL -CONSOLIDATION TEST RESULTS Fig. 5 HYDROMETER ANALYSIS 24 HR 7HR 45 MIN 15 MIN 100 90 80 70 z 60 s °- 50 r- 4 0 40 30 20 10 0 T IME READINGS SIEVE ANALYSIS U S STANDARD SERIES 60 MIN. 19 MIN. 4 MIN 1 MIN '200 '400 '50'40'30 '16 110'8 1 .4 CLEAR SOUARE OPENINGS �.. 11'• 3" 5' 6' 8" 0 r r 1 L - 1 r - 1 � r r 001 002 111 1 005 009 IF 1 1 111 1 r 6 1 11TS 1 1 .1 1 11ll11 ti 019 .037 074 .149 .297 1 .590 1,19 2.38 4.76 42 2.0 DIAMETER OF PARTICLE IN MILLIMETERS CLAY TO SILT SAND 10 20 30 ❑ 40 Z 50 cE 60 70 80 90 00 9.52 19- I 38-1 . 7 62 127 1 200 152 EINE MEDIUM TCOARSE GRAVEL 3 % SAND 54 LIQUID LIMIT SAMPLE OF very silty sand SILT AND CLAY PLASTICITY INDEX GRAVEL FINE I COARSE 43 % COBBLES FROM Boring 1 at 3 feet HYDROMETER ANALYSIS j] SIEVE ANALYSIS TIME READINGS J U S. STANDARD SERIES CLEAR SOUARE OPENINGS 24 HR. 7 RR_ j 45 MIN. 15 MIN. 60 MIN. 19 MINA MIN. 1 MIN. '200 '100 '50 '40'30 '16 'ire '4 4' V.^ P4 100 z ¢ 40 30 70 L 1 ' t F- 10 0 001 .002 I 1 I 1 '1r T I L 1 1 1 1 1 1 1 j1 1 111111 L LJ 1 1 111 4 } 1 1 11 1 1 111 .005 .009 .019 037 .074 ,149 297 .590 1.19 12.38 4.76 9-52 42 2.0 DIAMETER OF PARTICLE IN MILLIMETERS 1 1 1 1 1 11 1 1 i 19-1 38.1 76.2 127 2 152 CLAY TO SILT GRAVEL 4 % LIQUID LIMIT SAND FINE MEDIUM JCOARSE GRAVEL FINE _1 COARSE C09BLES SAND 66 , % SILT AND CLAY 30 96 SAMPLE OF silty sand PLASTICITY INDEX FROM Boring 2 at 4.5 feet 0 10 20 30 40 w z w 50¢ 1- z w 800 a 70 60 90 100. 4 481 92-1 CheneNorthern, Inc. GRADATION TEST RESULTS Fig, 6 Chen -Northern, Inc. TABLE 1 SUMMARY OF LABORATORY TEST RESULTS 4 481 92-1 SAMPLE LOCATION NATURAL MOISTURE CONTENT OW NATURAL DRY DENSITYNO. IP�II GRADATION PERCENT PASSING 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH WA( SOIL OR BEDROCK TYPE BORING DEPTH Iee1) GRAVEL (%). SAND (%) LIQUID LIMIT (%) PLASTICITY INDEX f%) 1 3 6 97 3 54 43 very silty sand 8 11 108 44 very silty sand ilistone bedrock r. .II1 - 18 2 60 23 6 2 4.5 7 105 4 66 30 silty sand 9.5 104 34 silty sand r CLASSIFICATION OF SOILS FOR ENGINEERING PURPOSES Chen -Northern, Inc, ASTM Designation: D 2487 - 83 (Based on Unified Soil Classification System) ,.aM o•,"moa.-r, Soil Classification Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests' Group Symbol Name' Coarse-Gralned Soils Gravels More than 50% retained on More than 50% coarse No. 200 sieve fraction relained on No. 4 sieve Fine -Grained Soils 50% or more passes the No. 200 sieve - Clean Gravels Cu..4 and 15Cc3' GW Well graded gravel' Less than 5% fines` Cu<4 and/or 1>Cc>3' GP Poorly graded gravel' Gravels with Fines More than 12% fines` Fines classify as ML or MH GM Silty gravel' ° " Fines classify as CL or CH GC Clayey gravel` °" Sands 50% or more of coarse fraction passes No. 4 sieve Clean Sands Cu?6 and 15Cc53` SW Well -graded sand' Less than 5% lines° Cu<6 and/or 1>Cc>3' SP Poorly graded sand' Sands with Fines More than 12% fines° Fines classify as ML or MH SM Silty sand° "' Fines classify as CL or CH SC Clayey sand° "' Silts and Clays Liquid limit less than 50 inorganic organic PI>7 and plots on or above CL "A" line' Lean clay"' Pl<4 or plots below "A" line' ML Silt" " Liquid limit - oven dried <0 75 OL Liquid limit - not dried Organic clay" "" Organic silt` " ° Silts and Clays Liquid limit 50 or more inorganic PI plots on or above "A" line CH Fat clay"' PI plots below "A" line MH Elastic silt' `" organic Liquid limit - oven dried <0.75 OH Liquid limit - not dried Organic clay" " • Organic silt" ° Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat 'Based on the malarial passing the 3 -in. (75 -mm) sieve. 'if field sample contained cobbles or boulders. or both. add "with cobbles or boulders, or both" to group name. 'Gravels with 5 to 12% lines require dual symbols: GW -GM well -graded gravel with sill GW -GC well -graded gravel with clay GP -GM poorly graded gravel with sill GP -GC poorly graded gravel with clay °Sands with 5 l0 12% fines require dual symbols: SW -SM well -graded sand with silt SW -SC well -graded sand with clay SP -SM poorly graded sand with sill SP -SC poorly graded sand w)th clay 100 'Cu = Dm /D,o Cc =D. 'll soil contains 15% sand. add "with sand" 10 group name. '1I fines classify as CL -ML, use dual symbol GC -GM, or SC -SM. "I1 lines are organic, add "with organic fines" to group name. 'EI soil contains a..15% gravel, add "with gravel" to group name. SIEVE ANALYSIS 60 1 SCREEN - IN SIEVE NCI. 321`41 4 % 4 10 20 40 60 140200 0 0 40 4 ¢ 60 ¢Wyr B 0,, = 0.075 100 1 l 1 1 50 10 5 1.0 0.5 0.10 PARTICLE SIZE 11,1 MILLIMETERS c - O'° - 15 = 200 C = (Del'_ 12.51' s 5.6 0 Ow 0.075 c 0.010« 0.075 • 15 PLASTICITY INDEX (PI) 50 40 30 20 10 7 4 0 9f Auerberg Iimils plot in hatched area, soil is a CL -ML. silty clay, 'If soil contains 1510 29% plus No. 200. add "with sand" or "with gravel", whichever is predomlrranl. '11 soil contains ?30% plus No. 200. predominantly sand, add "sandy" to group name. '11 soil contains C30% plus No. 200, predominantly gravel, add "gravelly" 10 group name. ^Pia4 and plots on or above "A" line. °PI<4 or plots below "A' line. "PI plots on or above "A" line. °PI plots below "A" line. For c{palflcstl11 of fine-gralned soils and / / / fine-grained traction oane-grained lco Bolls/ — Equation Norixontal then Equation Vertical then of "A" -line al PI = 4 to LL P1 = 0.73 ILL -201 of "Udine at LL= 16 MP! PI = 0.9 (LLA/ = 25.5, =7 ./ '$ ' A, / / 0� ss ,4''' \'' // / c4' �X\ / / / �' // / /JJ oP G�' MH o OH — /ACSM'///, ML OL 10 16 20 40 so 60 LIQUID LIMIT (LL) 70 BO 90 100 110 391 28' 27" 39° 28' 3" 107° 19' 41 299800 299900 Drainage Class—Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties (Seaton Subdivision) 300000 300100 300200 300300 300400 300500 300600 300700 300830 107" 19' 40" 299800 299900 00 300100 Map Scale: 1:5,250 if printed on A size (8.5" x 11") sheet. 0 50 100 200 306200 Meters 300 300300 300403 300500 300600 300700 300800 0 USDA Natural Resources Conservation Service 250 500 1,000 Feet 1,500 Web Soil Survey National Cooperative Soil Survey 0 0 0 m M1 M 0 0 0 0 0 M 0 v 1011/2009 Page 1 of 3 39° 28 26" 39° 28' 4' Drainage Class -Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties (Seaton Subdivision) MAP LEGEND Area of Interest (AOI) Area of Interest (AOL) Soils Soil Map Units Soil Ratings Excessively drained fl Somewhat excessively drained 0 Well drained Q Moderately well drained 0 Somewhat poorly drained 0 Poorly drained Fa Very poorly drained Not rated or not available Political Features p Cities Water Features ( j Oceans Streams and Canals Transportation +++ Rails xY Interstate Highways US Routes Major Roads . y Local Roads MAP INFORMATION Map Scale: 1:5,250 if printed on A size (8.5" x 11") sheet. The soil surveys that comprise your AOI were mapped at 1:24,000. Please rely on the bar scale on each map sheet for accurate map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http:1/websoilsurvey.nres.usda.gov Coordinate System: UTM Zone 13N NAD83 This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Survey Area Data: Version 5, Jun 9, 2008 Date(s) aerial images were photographed: 7/19/2005; 8/6/2005 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/1/2009 Page 2 of 3 Drainage Class–Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Seaton Subdivision Drainage Class Drainage Class— Summary by Map Unit — Aspen -Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 18 Cochetopa-Antrobus association, 12 to Well drained 25 percent slopes 13.2 11.4% 42 Fluvaquents, 0 to 10 percent slopes Somewhat poorly drained 12.4 10.7% 49 Goslin fine sandy loam, 3 to 6 percent Well drained slopes 24.9 21.6% 50 Goslin tine sandy loam, 6 to 25 percent Well drained slopes 3.8 3.3% 94 95 Showalter-Morval complex, 5 to 15 Well drained percent slopes Showalter-Morval complex, 15 to 25 Well drained percent slopes 12.8 48.2 11.1% 41.8% Totals for Area of Interest 115.3 100.0% Description "Drainage class (natural)" refers to the frequency and duration of wet periods under conditions similar to those under which the soil formed. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil. Seven classes of natural soil drainage are recognized -excessively drained, somewhat excessively drained, well drained, moderately well drained, somewhat poorly drained, poorly drained, and very poorly drained. These classes are defined in the "Soil Survey Manual." Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Web Soil Survey 10/1/2009 P Y 9 Conservation Service National Coo erative Soil Surve Pae 3 of 3 26 Soil Survey stoniness. Buildings and roads should be designed to offset the effects of shrinking and swelling. The high content of rock fragments makes excavation difficult. This map unit is in capability subclass Vie, nonirrigated. The Cochetopa soil is in the Subalpine Loam range site, and the Antrobus soil is in the Stony Loam range site. r18—Cochetopa-Antrobus association, 12 to 25 percent slopes. This map unit is on mountainsides and fans. Elevation is 8,500 to 10,500 feet. The average annual precipitation is 18 to 20 inches, the average annual air temperature is 36 to 38 degrees F, and the average frost -free period is 45 to 60 days. This unit is about 45 percent Cochetopa loam and 35 percent Antrobus very stony loam. The Cochetopa soil is in broad, slightly concave areas, and the Antrobus soil is on the steeper convex slopes. Included in this unit are small areas of Forsey and Jerry soils. Included areas make up about 20 percent of the total acreage. The Cochetopa soil is deep and well drained. It formed in alluvium derived dominantly from basalt. Slope is 12 to 20 percent. Typically, the upper part of the surface layer is dark grayish brown loam about 3 inches thick. The lower part is very dark grayish brown clay loam about 11 inches thick. The subsoil is clay loam about 24 inches thick. The substratum to a depth of 60 inches or more is gravelly clay loam. The soil is noncalcareous to a depth of 40 to 60 inches and calcareous below that depth. Permeability is slow in the Cochetopa soil. Available water capacity is moderate. The effective rooting depth is 60 inches or more. Runoff is rapid, and the hazard of water erosion is moderate. The Antrobus soil is deep and well drained. It formed in alluvium and colluvium derived dominantly from basalt. Slope is 15 to 25 percent. About 12 to 15 percent of the surface is covered with stones, and 25 percent is covered with cobbles. Typically, the upper part of the surface layer is dark grayish brown very stony loam about 8 inches thick. The lower part is brown very stony loam about 5 inches thick. The substratum to a depth of 60 inches or more is extremely stony loam. The soil is calcareous throughout. Permeability is moderate in the Antrobus soil. Available water capacity is low. The effective rooting depth is 60 inches or more. Runoff is rapid, and the hazard of water erosion is moderate. This unit is used as rangeland or for homesite development. The potential plant community on the Cochetopa soil is mainly Thurber fescue, bearded wheatgrass, Columbia needlegrass, mountain brome, and Idaho fescue. Western wheatgrass, mountain snowberry, geranium, western yarrow, and small areas of aspen also are included. The average annual production of air- dry vegetation is about 2,800 pounds per acre. If the range condition deteriorates, Kentucky bluegrass, geranium, Douglas rabbitbrush, and western yarrow increase in abundance. The potential plant community on the Antrobus soil is mainly bluebunch wheatgrass, needlegrasses, antelope bitterbrush, mountain big sagebrush, and Saskatoon serviceberry. Other plants that characterize this site are Douglas rabbitbrush and mountain snowberry. The average annual production of air-dry vegetation is about 1,200 pounds per acre. If the range condition deteriorates, mountain big sagebrush, Douglas rabbitbrush, needlegrasses, and annual weeds increase in abundance. The suitability of this unit for range seeding is poor. The main limitations are the slope and the stones on the surface. Suitable management practices include proper range use, deferred grazing, and rotation grazing. Aerial spraying is suitable for brush management. If this unit is used for homesite development, the main limitations are a high shrink -swell potential and the stoniness. Buildings and roads should be designed to offset the effects of shrinking and swelling. This map unit is in capability subclass Vle, nonirrigated. The Cochetopa soil is in the Subalpine Loam range site, and the Antrobus soil is in the Stony Loam range site. 19—Cochetopa-Antrobus association, 25 to 50 percent slopes. This map unit is on mountainsides. Elevation is 8,500 to 10,500 feet. The average annual precipitation is 18 to 20 inches, the average annual air temperature is 36 to 38 degrees F, and the average frost -free period is 45 to 60 days. This unit is about 45 percent Cochetopa loam and 40 percent Antrobus very stony loam. The Cochetopa soil is on slightly concave benches, and the Antrobus soil is on the steeper convex slopes. Included in this unit are small areas of Forsey and Jerry soils. Included areas make up about 15 percent of the total acreage. The Cochetopa soil is deep and well drained. It formed in alluvium and colluvium derived dominantly from basalt. Slope is 25 to 40 percent. Typically, the upper part of the surface layer is dark grayish brown loam about 3 inches thick. The lower part is very dark grayish brown clay loam about 11 inches thick. The subsoil is clay loam about 24 inches thick. The substratum to a depth of 60 inches is gravelly clay loam. The soil is noncalcareous to a depth of 40 to 60 Aspen -Gypsum Area, Colorado 39 Suitable management practices include proper 42—Fluvaquents, 0 to 10 percent slopes. This grazing use and a planned grazing system. The broadly defined unit consists of deep, somewhat poorly suitability of this soil tor range seeding is poor. The drained, nearly level soils on flood plains and alluvial main limitation is the slope. The slope limits access by valley floors. These soils formed in alluvium. livestock. The limited accessibility results in overgrazing Fluvaquents are stratified and vary widely in texture of the less sloping areas. and in depth to sand, gravel, and cobbles. Typically, the This unit is poorly suited to homesite development. surface layer ranges from loamy sand to fine sandy The main limitation is the slope. loam or from silt loam to clay loam. The underlying This map unit is in capability subclass Vile, layers are generally sandy loam or loam stratified with nonirrigated. It is in the Deep Loam range site. sand, gravel, and cobbles. In some areas grave! and cobbles are on or near the surface. 41—Evanston loam, 45 to 65 percent slopes. This The water table fluctuates between depths of 0.5 foot deep, well drained soil is on alluvial fans, terraces, and and 2.0 feet during spring and summer. These soils are valley sides. It formed in mixed alluvium. Elevation is occasionally flooded for brief periods in late spring and 6,500 to 8,000 feet. The average annual precipitation is early summer. 13 to 15 inches, the average annual air temperature is Included in this unit are small, isolated areas of 42 to 46 degrees F, and the average frost -free period is Redrob soils. Also included are small, isolated areas 80 to 90 days. where water stands at or near the surface all year. Typically, the surface layer is brown loam about 12 These water areas are identified by a special symbol on inches thick. The subsoil is clay loam about 13 inches the soil maps. Included areas make up about 15 thick, The substratum to a depth of 60 inches or more is percent of the total acreage. loam. These soils are used for wildlife habitat, recreational Included in this unit are small areas of Tridell soils, development, or grazing. The native vegetation is areas of Evanston soils that have slopes of less than 45 mainly cottonwood, willow, water -tolerant grasses, percent, and small areas of Rock outcrop. Included sedges, and rushes. Mule deer, cottontail rabbit, coyote, areas make up about 15 percent of the total acreage. and bobcat and ducks, geese, and other native birds Permeability is moderate in this Evanston soil. find food and shelter on these soils. Where feasible, Available water capacity is high. The effective rooting planting small grain, trees, and shrubs improves the depth is 60 inches or more. Runoff is rapid, and the habitat for upland wildlife. hazard of water erosion is moderate or severe on the This unit is poorly suited to homesite development. steeper slopes. The main limitations are the flooding and the seasonal This unit is used mainly as rangeland. It also is used high water table. as wildlife habitat. This map unit is in capability subclass Vlw, The potential plant community on this unit is mainly nonirrigated. It generally is in the Riverbottom range bluebunch wheatgrass, western wheatgrass, site. At the higher elevations, however, it is in the muttongrass, Douglas rabbitbrush, and mountain big Mountain Meadow range site. sagebrush. Utah serviceberry, mountain snowberry, prairie junegrass, and Ross sedge commonly are also 43—Forelle-Brownsto complex, 6 to 12 percent included. The average annual production of air-dry slopes. This map unit is on mountains and benches. vegetation is about 1,500 pounds per acre. !f the range Elevation is 6,500 to 7,500 feet. The average annual condition deteriorates, mountain big sagebrush, precipitation is 12 to 14 inches, the average annual air Douglas rabbitbrush, cheatgrass, and annual weeds temperature is 40 to 44 degrees F, and the average increase in abundance. frost -free period is 85 to 105 days. Suitable management practices include proper This unit is about 55 percent Forelle soil and 30 grazing use and a planned grazing system. The percent Brownsto soil. suitability of this soil for range seeding is poor. The Included in this unit are small areas of Tridell soils on main limitation is the slope. The scope limits access by knolls, Mussel and Morval soils in swales, and basalt livestock. The limited accessibility results in overgrazing Rock outcrop. Also included are small areas of soils of the less sloping areas. that are similar to the Forelle and Brownsto soils but This unit is poorly suited to homesite development. have soft bedrock below a depth of 40 inches. Included The main limitation is the slope. areas make up about 15 percent of the total acreage. This map unit is in capability subclass Vile, The Forelle soil is deep and well drained. It formed in nonirrigated. It is in the Deep Loam range site. mixed alluvium derived dominantly from sedimentary 64 throughout the year. This soil is subject to rare flooding of brief duration. Ice jams may cause flooding during prolonged cold periods in winter. This unit is used for irrigated hay and pasture or as wildlife habitat. It is well suited to hay and pasture. The main limitations are the restricted rooting depth for plants that are not water -tolerant and a short growing season. The wetness limits the choice of suitable forage plants and the period of cutting or grazing and increases the risk of winterkill. Irrigation water can be applied by furrow, border, corrugation, and sprinkler methods. This unit provides food and cover for waterfowl and other wetland wildlife. This unit is poorly suited to homesite development. The main limitations are the wetness and the hazard of flooding. This map unit is in capability subclass IVw, irrigated and nonirrigated. It is in the Riverbottom range site. 93—Rogert very stony sandy loam, 25 to 65 percent slopes. This shallow, well drained soil is on mountainsides. It formed in residuum derived dominantly from granite. Elevation is 7,500 to 9,500 feet. The average annual precipitation is 18 to 20 inches, the average annual air temperature is 36 to 38 degrees F, and the average frost -free period is 35 to 60 days. Typically, the upper part of the surface layer is dark grayish brown very stony sandy loam about 6 inches thick. The lower part is brown very gravelly sandy loam about 11 inches thick. Hard granite is at a depth of 10 to 20 inches. The soil is noncalcareous throughout. Included in this unit are small areas of soils that are similar to the Rogert soil but are finer textured and deeper over granite bedrock. Also included are small areas of soils that are similar to the Rogert soil but have a lighter colored surface layer. Included areas make up about 15 percent of the total acreage. Permeability is moderately rapid or rapid in the Rogert soil. Available water capacity is very low. The effective rooting depth is 10 to 20 inches. Runoff is medium, and the hazard of water erosion is moderate. This unit is used for livestock grazing or wildlife habitat. The potential plant community is mainly western wheatgrass, bluebunch wheatgrass, prairie junegrass, and mountain big sagebrush. Other plants that characterize this site are needleandthread, Indian ricegrass, Idaho fescue, and small numbers of many forbs. Some areas of aspen are also included. The average annual production of air-dry vegetation is about 1,000 pounds per acre. The suitability of this unit for range seeding is poor. The main limitations are the slope and the surface Soil Survey stoniness. Suitable management practices include proper range use, deferred grazing, and rotation grazing. Aerial spraying is suitable for brush management. This unit is poorly suited to homesite development. The main limitations are the slope and the depth to bedrock. This map unit is in capability subclass Vile, nonirrigated. It is in the Rocky Loam range site. —� 94—Showalter-Morval complex, 5 to 15 percent slopes. This map unit is on alluvial fans, high terraces, and valley sides. Elevation is 7,000 to 8,500 feet. The average annual precipitation is 14 to 16 inches, the average annual air temperature is 42 to 44 degrees F, and the average frost -free period is 80 to 90 days. This unit is about 45 percent Showalter very stony loam and 35 percent Morval loam. The Showalter soil is in convex areas, and the Marva! soil is in the more concave areas. Included in this unit are small areas of soils that are similar to the Morval soil but have a thicker surface layer. Also included are small areas of soils that are similar to the Morval soil but have 30 to 40 percent cobbles in the substratum. Included areas make up about 20 percent of the total acreage. The Showalter soil is deep and well drained. It formed in alluvium derived dominantly from basalt. About 10 to 15 percent of the surface is covered with stones, 5 percent with cobbles, and 5 percent with gravel. Typically, the surface layer is brown very stony loam about 8 inches thick. The upper 3 inches of the subsoil is very cobbly clay loam. The lower 28 inches is very cobbly clay. The substratum to a depth of 60 inches or more is very cobbly clay loam. Permeability is slow in the Showalter soil. Available water capacity is moderate. The effective rooting depth is 60 inches or more. Runoff is medium, and the hazard of water erosion is slight. The Morval soil is deep and well drained. ft formed in alluvium derived dominantly from basalt. Typically, the surface layer is brown loam about 7 inches thick. The upper 12 inches of the subsoil is clay loam. The lower 4 inches is loam. The substratum to a depth of 60 inches is loam. The soil is noncalcareous to a depth of 19 inches and calcareous below that depth. Permeability is moderate in the Morval soil. Available water capacity also is moderate. The effective rooting depth is 60 inches or more. Runoff is medium, and the hazard of water erosion is slight. This unit is used as hayland or rangeland, for crops, or for homesite development. It is moderately suited to hay and crops. The main limitations are the surface stoniness, the slope, and the slow permeability. Aspen -Gypsum Area, Colorado 65 Grasses and legumes grow well if adequate fertilizer is used. Limiting tillage for seedbed preparation and controlling weeds help to control runoff and erosion. If properly managed, the unit can produce 3 tons of irrigated grass hay or 60 bushels of barley per acre annually. The potential plant community on the Showalter soil is mainly bluebunch wheatgrass, western wheatgrass, prairie junegrass, Indian ricegrass, true mountainmahogany, antelope bitterbrush, Saskatoon serviceberry, and big sagebrush. The average annual production of air-dry vegetation is about 900 pounds per acre. The potential plant community on the Morval soil is mainly needleandthread, western wheatgrass, muttongrass, prairie junegrass, and big sagebrush. The average annual production of air-dry vegetation is about 1,500 pounds per acre. The main limitation for range seeding or mechanical treatment is the surface stoniness in areas of the Showalter soil. Range seeding generally is restricted to broadcasting because of this limitation. This unit is poorly suited to homesite development. The main limitations are the shrink -swell potential and the stones throughout the profile. This map unit is in capability subclass Vle, irrigated and nonirrigated. The Showalter soil is in the Loamy Slopes range site, and the Morval soil is in the Deep Loam range site. 95—Showalter-Morval complex, 15 to 25 percent slopes. This map unit is on alluvial fans, high terraces, and valley sides (fig. 7). Elevation is 7,000 to 8,500 feet. The average annual precipitation is 14 to 16 inches, the average annual air temperature is 42 to 44 degrees F, and the average frost -free period is 80 to 90 days. This unit is about 45 percent Showalter very stony loam and 35 percent Morval loam. The Showalter soil is in convex areas, and the Morval soil is in the more concave areas. Included in this unit are small areas of soils that are similar to the Morval soil but have 30 to 50 percent cobbles in the substratum. Included areas make up about 20 percent of the total acreage. The Showalter soil is deep and well drained. It formed in alluvium derived dominantly from basalt. About 10 to 15 percent of the surface is covered with stones, 5 percent with cobbles, and 5 percent with gravel. Typically, the surface layer is brown very stony loam about 8 inches thick. The upper 3 inches of the subsoil is very cobbly clay loam. The lower 28 inches is very cobbly clay. The substratum to a depth of 60 inches or more is very cobbly clay loam. Permeability is slow in the Showalter soil. Available water capacity is moderate. The effective rooting depth is 60 inches or more, Runoff is medium, and the hazard of water erosion is moderate. The Morval soil is deep and well drained. It formed in alluvium derived dominantly from basalt. Typically, the surface layer is brown loam about 7 inches thick. The upper 12 inches of the subsoil is clay loam. The lower 4 inches is loam. The substratum to a depth of 60 inches is loam. The soil is noncalcareous to a depth of 19 inches and calcareous below that depth. Permeability is moderate in the Morval soil. Available water capacity also is moderate. The effective rooting depth is 60 inches or more. Runoff is medium, and the hazard of water erosion is slight. This unit is used as rangeland or hayland or for homesite development. The potential plant community on the Showalter soil is mainly bluebunch wheatgrass, western wheatgrass, prairie junegrass, Indian ricegrass, true mountainmahogany, antelope bitterbrush, Saskatoon serviceberry, and big sagebrush. The average annual production of air-dry vegetation is about 900 pounds per acre. The potential plant community on the Marval soil is mainly needleandthread, western wheatgrass, muttongrass, prairie junegrass, and big sagebrush. The average annual production of air-dry vegetation is about 1,500 pounds per acre. The main limitation for range seeding or mechanical treatment is the surface stoniness in areas of the Showalter sail. Suitable management practices include proper range use, deferred grazing, and rotation grazing. Aerial spraying is suitable for brush management. If this unit is used for hay and pasture, the main limitations are the surface stoniness, the slope, and the slow permeability in the Showalter soil. Grasses and legumes grow well if adequate fertilizer is used. This unit is very poorly suited to homesite development. The main limitations are the slope, the shrink -swell potential, and the stones throughout the profile. This map unit is in capability subclass Vle, nonirrigated. The Showalter soil is in the Loamy Slopes range site, and the Morval soil is in the Deep Loam range site. 96—Southace cobbly sandy loam, 1 to 6 percent slopes. This deep, well drained soil is on upland terraces, mountainsides, and alluvial fans. It formed in alluvium derived dominantly from redbed sandstone and shale intermixed with gypsiferous material. Elevation is 6,000 to 7,000 feet. The average annual precipitation is