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Home My WebLink AboutEngineer OWTS Replacement Design 06.03.2016June 3, 2016 Mr. Andy Schwaller, Building Official Garfield County Building Department 108 gth Street Glenwood Springs, CO 81601 RE: Swale Property 411CR237, Silt, Colorado OWTS Replacement Design Dear Andy, 6 SGM www.sgm-inc.com The purpose of this letter is to transmit the replacement design regarding the onsite waste water treatment system (OWTS) for the Swale Residence located at 411 CR 237 in Silt, Colorado. The specific location of the property in question is located in Figure 1. As you have likely been made aware, the existing system, designed and constructed in the 1980's has failed in its ability to dispose of supernate effluent from the septic system and is now not effectively disposing of the supernate effluent from the septic tank into the tributary soils under the disposal field. Harvey Gap Road Silt Mesa Road Figure 1 ·Site Location of Swale Property GLENWOOD SPRINGS 118 West Sixth St, Suite 200 I Glenwood Springs, CO 81601 I 970.945.1004 6 SGM www.sgm·1nc.com The existing and replacement design accommodates a 2 bedroom single family home use. The existing system consists of a 1500 gallon concrete septic tank and soil treatment area of standard depth and design for beds of that 1980's era. It appears that the septic tank had not been pumped for a period of time which likely led to the failure of the existing field along with the age of the existing system. Given the condition that the existing field location is in, it is not going to be re-utilized or removed. An area located in the SE corner of the property, honoring 10 foot property line setbacks, is where soil testing was performed under our direction to determine the percolation rates of soils south and east of the exiting septic tank as well as the depth to and existence of both bedrock and ordinary high ground water levels (if present). The location of the site is some 240 feet away from the adjacent property's well south of the Swale property. The well for the Swale property is near their west property line, some 500 feet west of the proposed site. This is all based upon data reviewed from the State Water Engineer's AquaMap tool on the Division of Water Resources web page. Note that the testing was performed during the week of May 23 and it was determined that neither ground water nor bedrock was present. The overburden soils were consistent and appeared to be a clayey material consistent with the 3 Soil Type identified in the Garfield County OSWTS Regulations Table 10-1. Along with the percolation testing and profile hole observations, research was performed to gain insight on the specific soils parameters utilizing the SCS WebSoil survey. The percolation test yielded a percolation rate of between 5 minutes per inch to 20 minutes per inch. However, the instantaneous percolation rate continued to rise giving cause to rely on on-site soil observations coupled with the data obtained from the SCD WebSoil Survey. The higher percolation rate is consistent with our observations of the on-site soils being a "sandy clay loam" soil. The exhibit attached to this letter identify the information that was researched in addition to the testing performed to help determine the LTAR (Long Term Acceptance Rate) for the STA (Soil Treatment Area) for the design of the new disposal field. These Exhibits are listed as follows: 1. Exhibit A: NRCS Soil Map 2. Exhibit B: NRCS Hydrologic Soil Group 3. Exhibit C: NRCS Saturated Hydraulic Conductivity 4. Exhibit D: NRCS Engineering Properties Based upon the soils testing and the researched data, the LTAR for the on-site soils is 0.35 gallons per day per square foot. With this data, the STA (Soil Treatment Area) is 858 square feet. Because we will incorporate the use of Infiltrators (chambers), we have employed the size adjustment factors and reduced the bed size by the following: GLENWOOD SPRINGS 118 West Sixth St, Suite 200 I Glenwood Springs, CO 81601 I 970.945.1004 6 SGM www.sgm·inc.com For using chambers, a 0.7 factor is applied, thus resulting is an area of 600 sf. This results in four infiltrator or chamber trenches of dimension 52' in length. The attached calculations identify the thought process in the design of this system. The design and layout of the system is shown on the attached drawing following this letter. Upon your receipt and review, if you have any questions, please don't hesitate to call. Respectfully, Princip GLENWOOD SPRINGS 118 West Sixth St, Suite 200 I Glenwood Springs, CO 81601 I 970. 945. 1004 Client: OWTS Design Report and Calculations Swale, Thomas E Jr. and Shauna M 411 CR237 Silt, Colorado 81652 Date: 1-Jun-16 Flow Data for the OWTS Design 1 Home Use (2 Bedroom Home) 300 Total= 300 For Home Use, 2 persons per bedroom and 75 gallons per day per person, BODS = 0.06 #/person/day Home Use 300 gpd 0.24 #/day Totals: 300 gpd 0.24 #/day Soll Data for the OWTS 2 Data from on-site soil observations: Appears to be a loamy soil of consistent depth from surface to a depth of 10 feet where gravels and shale are encountered. At a depth of 11', neither bedrock or groundwater have been encountered. Data from the web soil survey indicates a Potts Loam exists. Data from our own percolation testing indicated the following: Holel Hole2 Hole3 Depth Drop perc Depth Drop perc Depth Drop 36 36 36 39.5 3.5 4.6 39 3 5.3 36 3.5 41 1.5 6.7 40 1 10.0 37.5 1.5 41.75 0.75 13.3 40.75 0.75 13.3 38.5 1 42.25 0.5 20.0 41.25 0.5 20.0 39.25 0.75 1 13.3 14.4 Average of 3 percolation holes: 12.6 mpi perc 4.571429 6.666667 10 13.33333 10.0 Given the consideration of all data, the Long Term Acceptance Rate to use Is 0.35 gallons/sf/day Septic Tank Sizing 3 Flow calculated from above: 300 gpd Time to Drop 0 16 10 10 10 10 48 hour detention time for septic tank sizing; Volume= 600 gpd Use a standard 1250 gallon precast concrete septic tank. Sizing of Absorption Field or Soil Treatment Area 5 Going with a soil type 3 and Treatment Level 2, LTAR = 0.35 g/sf/d For a pressure dosed system, size adjustment factor is 1.0 for a bed configuration For a gravity system, the size adjustment factor shall be 1.2 for a bed configuration For a gravity trench system, adjustment factor= 1.0 For a pressure dosed trench system, adjustment factor= 0.8 For use of chambers: size adustment factor is 0.7 STA= Flow/LTAR 857.1429 square feet (unfactored) For a chamber system, gravity flow, adjust size to 0. 7*858= For a chamber system in a trench configuration, length= (this would equate to 4 runs of SO feet each) 600 square feet 200 feet With the effective length of a Quick4 chamber at 4', use 13 chambers per trench Thus the net length of the runs will be 52' each. J ' l ' ~ ~: J t I -· ~ I f l i ~II ~i ~ ttlCtlt' ~ QDINO(IT AT AU HCllUCJ#DIL ~~ OwtrZSIN~ tit/DI LQl:OIUI IN ->Ill MICAS "' CUN#-'11/r -'-1!11'11111MIZ" ,. «UJill ,__ --'1Dlf "-C!MMCl!II ClASS • S&fR Cl.fNi-Olg D£TAlt. NOT Ill SCMS QUICK4 STANDARD MULTIPORT END CAP ~\++ I J-'. I For Construction ll87 ~ 6SGM I I 8 West Si•lh Streel, Suila 200 Glenwood Springs, CO 81601 970.945 1004 www.sgm-inc.~ •·l"ICl'lltllt --_..,._ ~ . .. . .. __ ,,., __ Ill,.,,. fir ~ _.'Oll,._..ACDIS ~ .. 1500 GAL. EXIST. SEPTIC TANK Environmental Plant Center OSWT System Construction ""'' ro $CA4,£ nt J<W 'P'C ro omwc --rrr =- ••SJUl..u.,JllUl'tlf: -AT V•1'ft00#:&1J'C "' 11n•• lllOOf (m'. "f} Rcvi,ion ~ ~ ~ ~ ~ ti INFILTRATOR SYSTEMS INC. QUICK4 STAN DARD CHAMBER r ---34· IJOIJND FOR PR0P£R OllAINAC£ lSTASUSN VCCCTA/ll<f" COVCR NATTV£ 8ACKf11.L I'--·"' ~---Jis·-----t QUICK4 CHAMBER TYPICAL INSTALLAnON DETAIL (Not to Scam) r PIP£ CCP, 111' 11· .w4.r BURIN. DO'rlf 12" UIN.. H -10 LOAD AR£AS 11• UW.. NON• T1W17C AR£AS r:r / tRAOt .....-~DI(~ 14 • OBSDlllATION PIPC. m> £)(1S11NC NAl?l£ SM;KFTU. ,.,,,. / rl-51111 soc, m> ! t l:./unm.roR QIC.l'CK4~ ~ ~ ~lfll£SS Cll4MBlR u \\ I .J• NOTC " °'°' .a• " lJO'fH. l'flOtlDC (TrP) :~,,:,=~~~01Zl00 ,.. -ANl&DIT-- 6' MIN (10· SHOWrl) QUICK4 TRENCH DETAIL NOT"' SOii Dote I Bv I JwN<>. 2011>21 I l Plan View Schematic Drawn by: KS System Layout Odo: 6 /3 /2016 oc rt l!>S Of 01 '"'' 2'C l.,,lt ..... 'H JC'1J"N a ... I .. e i i :t ~ i ~ ~-... 2169930 269950 _,_ 269970 Soil Map-Rifle Area, Colorado, Parts of Garfield and Mesa Counties (Swale Property OWTS) 270010 270030 270050 27007'0 I »' JC' 8'N ~~~-,.-....... ,.. :t ~ i ~ Iii 2l699JO 269950 269970 269990 270010 2'/0030 270050 2i0070 Map Salle: 1: 1,170 if prYlll!d m A landscape ( 11" x 8.5") sheet N o ....... 1s=======30=--------------=00=============00MaPss A o,... .... ~so=======1~00,... .......... ~2oo::;::::==========~JOOFes:. Mapptljedial: WebMen3Dr Comermordilat!!s: WGS84 Fdgettcs: lJTMZone 13NWGS84 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 270090 EXHIBIT A VOlSll 270110 2701JO DlllSll 270170 :t );: i ~ 270170 :t ~ ~ ~ I I ~ i m ~ m • m ... 61212016 Page 1of3 'H' JC' 1.3' N »' JC'B' N !ii Soil Map-Rifle Area, Colorado , Parts of Garfield and Mesa Counties (Swale Property OWTS) MAP LEGEND MAP INFORMATION Area of lntere1l (AOIJ D Area of Interest (AOI) Solla D Soll Map Unit Polygons ,..,,. Soil Map Unit Lines c::J Soil Map Unit Points Speclal Point Features (l1) 181 )( 0 ;x; . .. 0 A. .w. ~ @ 0 v + .. . .. ~· 0 9 JI/ Natural Resources Conservation Service Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Waler Perennial water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sod1cSpot § Spoil Area 0 Stony Spot lD Very Stony Spot v' Wet Spot t:. Other ... Special Line Features Water Features Streams and Canals Transportation +++ Rails ~ , Interstate Highways US Routes Major Roads Local Roads Background & Aerial Photography Web Soil Survey National Cooperative Soil Survey The soil surveys that comprise your AOI were mapped at 1:24 ,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of son line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale . Please rely on the bar scale on each map sheet for map measurements . Source of Map : Natural Resources Conservation Service Web Soll Survey URL: http:llwebsollsurvey.nrcs.usda.gov Coordinate System : Web Mercator (EPSG :3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection , should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area:. RiRe Area , Colorado , Parts of Garfield and Mesa Counties Survey Area Data: Version 9. Sep 22 , 2015 Soil map units are labeled (as space allows) for map scales 1 :50 .000 or larger. Date(s) aerial images were photographed: Aug 7, 2011-Sep 3, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on lhese maps. As a result, some minor shifting of map unit boundaries may be evident. 612/2016 Page 2 of 3 Soil Map-RiRe Area , Colorado , Parts of Garfield and Mesa Counties Map Unit Legend Rifle Area, Colorado, Parts of Garfield and Mesa Counties (C0683) Map Unit Symbol 55 66 Totals for Area of Interest - USD\ Natural Resources --Conservation Service Map Unit Name Acres lnAOI Potts loam, 3 to 6 percent slopes Torriorthents-Camborthids- Rock outcrop complex , steep Web Soil Survey National Cooperative Soil Survey 4,0 0.1 4.1 Swale Property OWTS Percent of AOI 98.3% ~ 100.0% 6/2/2016 Page 3 of 3 H' J4'13"N m ... " ~ i ~ m ~ .. I ... ! ... I R ~ ... i-.. ~ 269930 269950 '2fH!lO Hydrologic Soil Group-Rifle Area, Colorado, Parts of Garfield and Mesa Counties (Swale Property OWTS) 270010 210030 270050 I H' J4'8'N i-~ ... .. . ;;= ~ ~ ~ !ii 269930 269950 269970 269990 270010 210030 N A Map Salle: 1: 1,170 if Jrt1ted ~ A landscape (11" x 8.5") sheet ------r:::::=====-------------============iMeters o ~ ~ ro oo o ....... so======1~00------------~2oo~==========::;:i~r-eet Mapprojedlal: WebMe!al!Dr Comeraot!nates: WGS84 Edge tics: lJTMZone 13NWGS84 27IXl50 270070 Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 21IXl90 270110 EXHIBIT B :c i;: ~ 270150 2701.30 270150 ~ 270170 270170 ;;= ~ ~ ~ ~ ~ I I m i ... m ... ~ 61212016 Page 1 of4 »' 34' 13"N H' J4'8'N ~ Hydrologic Soil Grou~ifte Area, Colorado, Parts of Garfield and Mesa Counties (Swale Property OWTS) MAP LEGEND Ant• of Interest (AOI) L Area or lnleresl (AOI) Solla Soll Rating Polygons D A D AID QB D BID oc D C/D D D D Not rated or nol available sou Rating LlnH -A .,,.,, AID _. B ~ BID -c -CID -D • • Not rated or not available Soll Rating Polnb D A 1!J AID El B • BID Natural Resources Conservation Service a c a CID El D D Nol rated or not available Water Features Streams and Canals Transportation +++ Ralls ,,_ Interstate Highways ~ US Routes Major Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soil Survey MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1 :24 ,ODO. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of lhe detail of mapping and accuracy of soil line placement. The maps do nol show the small areas of contrasling soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soll Survey URL: http://websollsurvey.nrcs.usda.gov Coordinate Syslem: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projedion, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product 1s generated from the USDA·NRCS certified data as of the version date(s) listed below. Soil Survey Area: Rifle Area, Colorado, Parts of Garfield and Mesa Counties Survey Area Data: Version 9 , Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Aug 7, 2011-Sep 3 , 2011 The orthophoto or other base map on which lhe soil lines were compiled and digilized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 612/2016 Page 2 of 4 Hydrologic Soil Group-Rifle Area , Colorado, Parts of Garfield and Mesa Counties Swale Property OWTS Hydrologic Soil Group Hydrologlc Soll Group-Summary by Map Unit -Rifle Area, Colorado, Parts of Garfield and Mesa Counties (C0683) Map unit symbol Map unit name Rating Acres lnAOI Percent of AOI 55 Potts loam, 3 to 6 percent c 4.0 slopes 66 Torriorthenls-D 0.1 Camborthids-Rock outcrop complex , steep Totals for Area of Interest 4.1 Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (AID , B/D , and CID). The groups are defined as follows ; Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chieHy of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. USDA Natural Resources ~-Conservation Service Web Soil Survey National Cooperative Soil Survey 98.3% 1.7% 100.0% 61212016 Page 3 of4 Hydrologic Soil Group-Rifle Area, Colorado, Parts of Garfield and Mesa Counties Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specmed Tie·break Rule: Higher usrn Natural Resources ~-Conservation Service Web Soil Survey National Cooperative Soil Survey Swale Property OWTS 61212016 Page 4 of4 3 ~ i Saturaled Hydraulic Conductivily (Ksat)-Rifte Area, Colorado, Parts of Garfield and Mesa Counlies (Swale Property OWTS) ~ 39' 34' 13" N m ... 269930 269950 269970 269990 270010 270030 270050 270070 ' ····-.J, I ::+ ... L 1 ~---~ 39' 34' B"N ~ I I ... e m 2-... ~ m-~w _ ..... ,,_ ... . 3 ~ i ~ 269930 269950 269970 269990 270010 2700JO ~ Scale: 1: 1,170 if prWecl on A Lvldsrape ( 11" x 8.5") sheet. N -------=======--------------============::::::1~ o ~ ~ ro ~ A o------·sor::======100 ................ 2coo============::::;>'Jl.1)Fe8 Map~; Web Meltclttr ComerCIXlldilates: ~ Edge tr:s: lJTM Zone 13N ~ 270050 270070 lJSOA Natural Resources iiiiim Conservation Service Web Soil Survey Nallonal Cooperalive Soil Survey 2ilXl90 :Dll110 EXHIBIT C :Dll150 :Dlll30 :Dll150 :Dll170 3 ;:; i ~ ~ s i -· ! :Dll170 3 r.. i ~ ... ~ e ~ ; 6/212016 Page 1of3 39' 34' 13" H 39' 34' B"N ~ Natural Resources Conservation Service Saturated Hydraulic Conductivity (Ksat)-Rifle Area, Colorado, Parts of Garfield and Mesa Counties (Swale Property OWTS) MAP LEGEND Area of Interest (AOI) __J Area of lntere&t (AOI) Solla Soll Rating Polygons D <=5.8100 C!J > 5.8700 and<= 19.9259 D Not rated or nol available Soll Rating LlnH ,,_ <: 5.8700 ~ > 5.8700 and<= 19.9259 • • Not rated or not available Soll Rating Points • <=5.8700 m > 5.8700 and <= 19.9259 0 Not rated or not available Water Features Streams and Canals Transportation +++ Rails ,,...,,_. """""' Interstate Highways US Routes Major Roads Local Roads Background Iii Aerial Photography Web Soil Survey National Cooperative Soil Survey MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1 :24,000. Warning: Soil Map may nol be valid at lhis scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils thal could have been shown at a more delailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: htlp:/lwebsollsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Rifle Area, Colorado, Parts of Garfield and Mesa Counties Survey Area Data: Version 9, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Aug 7, 2011-Sep 3, 2011 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. 61212016 Page 2 of 3 Saturated Hydraulic Conductivity (Ksat)-Rifle Area , Colorado. Parts of Garfield and Mesa Counties Saturated Hydraulic Conductivity (Ksat) Swale Property OWTS Saturated Hydraulic Conductivity (Ksatt-Summary by Map Unit -Rifle Area, Colorado, Parts of Garfield and Mesa Counties (C0683) Map unit symbol Map unit name Rating (micrometers Acres lnAOI Percent of AOI I per second) 55 Potts loam, 3 to 6 percent 19.9259 4.0 slopes 66 Torriorthents-5 .8700 0.1 Camborthids-Rock outcrop complex , steep ~ Totals for Area of Interest 4.1 ---- - Description Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a saturated soil transmit water. The estimates are expressed in terms of micrometers per second. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture . Saturated hydraulic conductivity is considered in the design of soil drainage systems and septic tank absorption fields . For each soil layer, this attribute is actually recorded as three separate values in the database. A low va l ue and a h igh value indicate the range of this attribute for the soil component. A "representative" value indicates the expected value of this attribute for the component For this soil property, only the representative value is used. The numeric Ksat values have been grouped according to standard Ksat class limits. Rating Options Units of Measure ; micrometers per second Aggregation Method: Dominant Component Component Percent Cutoff: None Specified Tie-break Rule : Fastest Interpret Nulls as Zero; No Layer Options (Horizon Aggregation Method}: Depth Range (Weighted Average) Top Depth : 24 Bottom Depth : 48 Units of Measure: Inches USDA Natural Resources ~-Conservation Service Web Soil Survey National Cooperative Soil Survey 98.3% 1.7% ·~J 61212016 Page 3 of 3 Engineering Properties-Rifle Area, Colorado, Parts of Garfield and Mesa Counties EXHIBIT D Engineering Properties This table gives the engineering classifications and the range of engineering properties for the layers of each soil in the survey area. Hydrologic soil group is a group of soils having similar runoff potential under similar storm and cover conditions. The criteria for determining Hydrologic soil group is found in the National Engineering Handbook, Chapter 7 issued May 2007(http:// directives.sc.egov .usda.gov/OpenNonWebContent.aspx?content= 17757. wba). Listing HSGs by soil map unit component and not by soil series is a new concept for the engineers. Past engineering references contained lists of HSGs by soil series. Soil series are continually being defined and redefined, and the list of soil series names changes so frequently as to make the task of maintaining a single national list virtually impossible. Therefore, the criteria is now used to calculate the HSG using the component soil properties and no such national series lists will be maintained. All such references are obsolete and their use should be discontinued. Soil properties that influence runoff potential are those that influence the minimum rate of infiltration for a bare soil after prolonged wetting and when not frozen. These properties are depth to a seasonal high water table, saturated hydraulic conductivity after prolonged wetting, and depth to a layer with a very slow water transmission rate. Changes in soil properties caused by land management or climate changes also cause the hydrologic soil group to change. The influence of ground cover is treated independently. There are four hydrologic soil groups, A, 8, C, and D, and three dual groups, AID, 8/D, and CID. In the dual groups, the first letter is for drained areas and the second letter is for undrained areas. The four hydrologic soil groups are described in the following paragraphs: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. Depth to the upper and lower boundaries of each layer is indicated. USOI\ Natural Resources ~-Conservation Service Web Soil Survey National Cooperative Soil Survey Swale Property OWTS 61212016 Page 1 of4 Engineering Properties-Rifle Area, Colorado, Parts of Garfield and Mesa Counties Texture is given in the standard terms used by the U.S. Department of Agriculture. These terms are defined according to percentages of sand, silt, and clay in the fraction of the soil that is less than 2 millimeters in diameter. "Loam," for example, is soil that is 7 to 27 percent clay, 28 to 50 percent silt, and less than 52 percent sand. If the content of particles coarser than sand is 15 percent or more, an appropriate modifier is added, for example, "gravelly." Classification of the soils is determined according to the Unified soil classification system (ASTM, 2005) and the system adopted by the American Association of State Highway and Transportation Officials (AASHTO, 2004). The Unified system classifies soils according to properties that affect their use as construction material. Soils are classified according to particle-size distribution of the fraction less than 3 inches in diameter and according to plasticity index, liquid limit, and organic matter content. Sandy and gravelly soils are identified as GW, GP, GM, GC, SW, SP, SM, and SC; silty and clayey soils as ML, CL, OL, MH, CH, and OH; and highly organic soils as PT. Soils exhibiting engineering properties of two groups can have a dual classification, for example, CL-ML. The AASHTO system classifies soils according to those properties that affect roadway construction and maintenance. In this system, the fraction of a mineral soil that is less than 3 inches in diameter is classified in one of seven groups from A-1 through A-7 on the basis of particle-size distribution, liquid limit, and plasticity index. Soils in group A-1 are coarse grained and low in content of fines (silt and clay). At the other extreme, soils in group A-7 are fine grained. Highly organic soils are classified in group A-8 on the basis of visual inspection. If laboratory data are available, the A-1, A-2, and A-7 groups are further classified as A-1-a, A-1-b, A-2-4, A-2-5, A-2-6, A-2-7, A-7-5, or A-7-6. As an additional refinement, the suitability of a soil as subgrade material can be indicated by a group index number. Group index numbers range from 0 for the best subgrade material to 20 or higher for the poorest. Rock fragments larger than 1 O inches in diameter and 3 to 1 O inches in diameter are indicated as a percentage of the total soil on a dry-weight basis. The percentages are estimates determined mainly by converting volume percentage in the field to weight percentage. Percentage (of soil particles) passing designated sieves is the percentage of the soil fraction fess than 3 inches in diameter based on an ovendry weight. The sieves, numbers 4, 10, 40, and 200 (USA Standard Series), have openings of 4.76, 2.00, 0.420, and 0.074 millimeters, respectively. Estimates are based on laboratory tests of soils sampled in the survey area and in nearby areas and on estimates made in the field. Liquid limit and plasticity index (Atterberg limits) indicate the plasticity characteristics of a soil. The estimates are based on test data from the survey area or from nearby areas and on field examination. References: American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard 02487-00. US!).\ Natural Resources ~-Conservation Service Web Soil Survey National Cooperative Soil Survey Swale Property OWTS 61212016 Page 2 of 4 Engineering Properties-Rlfle Area , Colorado, Parts of Garfield and Mesa Counties Report-Engineering Properties Absence of an entry indicates that the data were not estimated. The asterisk "" denotes the representative texture; other possible textures follow the dash. The criteria for determining the hydrologic soil group for individual soil components ls found in the National Engineering Handbook, Chapter 7 issued May 2007{http://directives.sc.egov.usda.gov/ OpenNonWebContent.aspx?content= 17757. wba). Engineering Properties-Ri fle A re a, Colorado, Parts of Ga rfield and Mesa Count ies Swale Property OWTS Map unit symbol and Pct. of Hydrolo Depth USDA text u re Claaslflcatlon Fragme nts Percentage paaslng sieve number-Liqui d Plastic It I s oll name map glc unit group I 55-Potts loam, 3 to 6 I percent slopes Potts ~ 85 c I Natural Resources Conservation Service ,,, 0-4 4-28 28-60 --- loam Clay loam Loam Unlned AASHTO >10 I 3·10 Inches Inches Pct I Pct I CL, CL-A-4 0-0-0 0-0-0 ML CL A-6 0-0-0 0-0-0 CL . Cl· A-4 0-0-0 10-0-0 Ml I Web Soil Survey National Cooperative Soil Survey 4 10 40 I 100-100 100-100 85-90- -100 -100 95 100-100 100-100 190-95-1 -100 -100 00 100-100 100-100 85-90- -100 -100 95 -~ llmlt 200 Pct 60-68-25-28 75 ·30 70-75-30-35 80 -40 60-68-25-28 75 -30 y lndex 1 5-8 -10 I ·- 10-15-2 0 5-8 ·10 61212016 Page 3 of 4 Engineering Properties-Rifle Area, Colorado, Parts of Garfield and Mesa Counties Engineering Properties-Rifle Area, Colorado, Parts of Garfield and Mesa Counties Map unit symbol and Pct. of Hydrolo Depth USDA texture Classlflcatlon Fragments soll name map glc unit group Unified AASHTO >10 3·10 Inches Inches In Pct I Pct 66-Torriorthenls- Camborthlds-Rock I outcrop complex, I sleep Torriorthents , steep 45 D 0-4 Variable - -0-0-0 0-10· 20 4-30 Fine sandy loam, CL, CL· A-2, A-4, 0-0-0 0-6-20 loam, clay loam ML, SC· A-6 SM.SM 30-34 Unweathered - - -- bedrock Camborthids, steep 20 c 0-4 Variable CL-ML, A·2,A-4 , 0-0-5 0-0-40 ML, SC-A-6 SM ,SM 4-30 Loam, clay loam CL, CL-A-4 ,A-6 0-0-0 0-3-5 ML 30-34 Unweathered - - - - bedrock Rock outcrop, sleep 15 0-60 Unweathered --- - I bedrock I Data Source Information Soil Survey Area: Survey Area Data: Rifle Area, Colorado, Parts of Garfield and Mesa Counties Version 9, Sep 22, 2015 USDA Natural Resources :iiiiiiiii Conservation Service Web Soil Survey National Cooperative Soil Survey Percentage passing sieve number- 4 10 40 200 -- -- 65-90-60-85-50-65-25-48- 95 90 80 70 -- -- 65-100-60-100-35-55-25-43- 100 100 75 60 100-100 75-88-1 55-73-50-SS- -100 00 90 80 - --- --- - I Swale Property OWTS Liquid Plastic It limit ylndex Pct -- -- 15-25 NP-10-2 .35 0 I --- 20-28 -35 25-33 -40 - 0-7 -14 - NP-8 -15 5-13-20 - - -- 61212016 Page4 of 4