GM 13-18 Geotechnical Recommendations.pdf

158377846

M E M O R A N D U M

Western Federal Lands Highway Division

610 E. Fifth Street

Vancouver, WA 98661

DATE: May 17, 2018

TO: Keith Wong

Project Manager

FROM: Robert Kraig

Geotechnical Engineer

SUBJECT: Geotechnical Memo 13-18

Geotechnical Recommendations

Maiden Road

MT DOT 14203(1)

Fergus County, MT

INTRODUCTION & OBJECTIVE

The Western Federal Lands, Highway Division (WFLHD) has been tasked with designing road improvements for approximately 9.5 miles of the Maiden Canyon Road (the project), also known as the Lewistown Air Force Access Road. The project is located just east of Brooks, Montana, in Fergus County at the intersection of US Highway 191 and the Maiden Canyon Road and includes asphalt concrete paving, aggregate stabilization, full-depth reclamation, grading, drainage, and pavement marking and signing. The project also includes replacing corrugated metal pipe culverts with 16 feet (span) by 5 feet (rise), pre-cast reinforced concrete box culverts at stations 293+61 (approximate MP 5.49) and 374+92 (about MP 7.03) and replacing the existing culvert at station 435+50 (MP 8.18) with a 24-inch equivalent diameter arch or elliptical pipe culvert. All pipe locations are within the second half of the project. The purpose of this memorandum is to provide general geological and geotechnical information as well as information relevant to the culvert replacement sites. This information was obtained from desk studies that include the results of a subsurface investigation performed by the Montana Department of Transportation (MDT) and field reconnaissance performed by members of the project design team. It should be noted that the WFLHD Geotechnical Team did not participate in the field reconnaissance.

Note that the project stationing used for this project (and for other referenced documents discussed in this memorandum) is based on the original stationing taken from the original as-built plan set dated September 25, 1961. The beginning of the project corresponds with station 3+55.93 and the end of the project corresponds with station 502+93.12, as referenced in the 70% plan set dated January 2, 2018.

The project location is shown in Figure 1 and the project vicinity is shown in Figure 2. The culvert locations scheduled for replacement as part of the project are shown relative to the beginning and ending limits of the project in Figure 4.

SITE CONDITIONS

The project is surrounded mostly by grazing and farmland. The terrain consists of rolling hills on the west end and climbs toward the timbered mountain range of the Judith Mountains at the east end. At the start, the project alignment runs east adjacent (to the north of) Warm Spring Creek before turning generally to the southeast where it crosses the creek at about mile post (MP) 5.5 and again at approximate MP 7.0 (see Figure 4), with the creek turning to the south shortly thereafter and the alignment continuing once again generally to the east.

Figure 1: Project Location relative to Billings, Bozeman and Helena, MT

Figure 2: Project Vicinity relative to Brooks, MT

GEOLOGY & LOCAL SOILS DESK STUDIES

We performed desk studies to investigate the local surficial geology and surveyed soils along the project corridor. Information pertaining to the surficial geology was obtained from the Geologic Map of the Lewistown 30’ x 60’ Quadrangle. Information regarding the local surveyed soils was obtained from the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) website. The results of these studies are discussed below.

Local Surficial Geology Obtained from the Geologic Map

Examination of the geologic map excerpt in Figure 3 will show that the project originates at the intersection of the Maiden Road with US 191 in the map unit Ktcm, but moves quickly into stream valley alluvium (Qal) and continues to near the end of the project where it rises from the valley as it moves into the TKtp map unit. Besides the map units that the project crosses, the project alignment runs along several other map units adjacent to the north (I.e., Km, Ktf, Kk, Je, TKrp and PZs). Descriptions from the geologic map for the Ktcm, Qal and TKtp map units are presented below, followed by discussion of the results of the local NRCS soil resource study.

Descriptions of the Km, Ktf, Kk, Je, TKrp and PZs map units are provided as a supplement to this memorandum and as such are contained in Attachment 1.

Figure 3: Excerpt from the Geologic Map of the Lewistown

30’ x 60’ Quadrangle, Central Montana

Ktcm (Upper Cretaceous): Telegraph Creek Formation and Marias River Formation, undivided.

North and west of Judith Mountains, the term Marias River Formation is assigned to rocks from top of Mowry Shale to base of Telegraph Creek Formation (Cobban et al., 1976);

members of formation, not mapped in quadrangle, include, in ascending order, Floweree, Cone, Ferdig, and Kevin. Lower Kevin shale, included in Ktcm, exposed in NENE sec. 5, T18N, R15E; contains 1 ft sandy, chert-pebble and cobble bed named McGowan Concretionary Bed (Cobban et al., 1959). Marias River Formation mapped with overlying Telegraph Creek Formation.

Telegraph Creek Formation, Ktc (Upper Cretaceous):

Medium to light gray weathering, noncalcareous, interbedded siltstone and fissile gray shale, sandier in upper part. Upper contact transitional, generally placed at base of lowest cliff-forming sandstone of overlying Eagle Formation. Formation mapped separately only around northeast end of Judith Mountains where exposures are fairly good and lower contact with Niobrara Formation occasionally observed. In rest of map area, Telegraph Creek Formation is mapped with Marias River Formation as unit Ktcm. Approximate thicknesses: 40 ft (12 m; Lindsey, 1982); 260 ft (87 m; Goddard, 1988).

Marias River Formation, Kmr (Upper Cretaceous):

Rocks above the Mowry Shale and below the Telegraph Creek Formation, as first describe by Cobban et al. (1976) in west-central Montana and as subsequently mapped by Vuke et al. (1995) in the west-adjacent Belt quadrangle.

Marias River member lithologies (not mapped in the Lewistown quadrangle, but mapped by Vuke et al., 1995) closely correspond to their Black Hills stratigraphic

Begin project at US 191

End project

Maiden Road

Ktcm equivalents, reflecting the remarkably consistent depositional conditions within the Western Interior sedimentary basin during this interval of Cretaceous time. Thus, the change to western Montana terminology is somewhat arbitrarily established in the Lewistown area of central Montana.

Qal (Quaternary): Alluvium of modern channels and flood plains (Holocene):

Yellow-tan and gray-tan, poorly to well stratified gravel, sand, silt, and clay deposited in flood plains and channels of modern streams. Locally includes some slightly older Holocene terrace alluvium, where terrace deposits not mapped separately. Thickness not measured.

TKtp (Tertiary): Tinguaite porphyry (Paleocene or upper Cretaceous)

Green and gray porphyry containing conspicuous tabular phenocrysts of alkali feldspar;

chiefly as dikes and sills; forms Lookout Peak and numerous bodies to southeast, and forms numerous dikes and sills west of Maginnis Mountain.

Local Soils Information Obtained from the NRCS

Soils information along the project corridor was obtained from published information available online through the NRCS Web Soil Survey (WSS). The NRCS is a joint effort of the US Department of Agriculture (USDA) and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies, and provides access to natural resource information. An Area of Interest (AOI) was developed that encompassed the project corridor and a Custom Soil Resource Report was generated for the AOI that contains the soil map units and related information for the soil units defined by the project corridor. The report is included in Attachment 1 and a Summary Table providing relevant information about the soil map units arranged in the rough order that they are encountered through the corridor from beginning to end is included in Attachment 3.

Although soil surveys are typically used for land planning purposes, they provide information that can be helpful and in greater detail than the information typically obtained from a geologic map; however, soil surveys typically only provide information regarding soil properties in the top 5 feet of ground.

Results of the study show that the majority of the soil types encountered along the project are described as loamy soils. The NRCS defines loam as a soil material that is 7 to 27 percent clay particles, 28 to 50 percent silt particles, and less than 52 percent sand particles. Many variations of loamy soils are present along the project alignment (e.g., clay loam, gravelly loam, silty clay loam, cobbly loam, etc.), with a few other soil units present in the minority such as silty clay, gravelly sand, etc.

SUBSURFACE EXPLORATION BY MDT

MDT performed a Preconstruction Soil Survey Investigation in May 2013 that included seventeen (17) subgrade test holes at approximately half-mile increments along the project beginning at MP 0.5 and ending at MP 8.5. Subgrade test hole drilling was followed-up by a laboratory testing program. Laboratory tests included in-place moisture content, moisture density relationships, specific gravity, soil classifications, Atterberg Limits, sieve analysis, R-

Value determinations, and chemical and corrosion potential. The MDT test results are included in Attachment 2 except for the test results showing the chemical and corrosion potentials, which are contained in Attachment 3 as discussed later.

Note that the project stationing associated with the MDT investigation followed as closely as possible the stationing used in the original as-builts and is taken to be close to that used in the current plan set.

The MDT test results show that the subgrade soil types varied somewhat along the project length. Unfortunately, the nature of this type of investigation provides no indication of the relative density of the granular soils or consistency of the cohesive soils encountered in the test borings. The test results showed AASHTO soil classifications of A-1a(0) to A-7-6(17). The soil classifications ranging from an A-1-a(0) to A-4(4) underwent R-Value testing. Soils that ranged from A-6(1) to A-7-6-(17) were assigned an R-Value of minus five (-5). The roadbed soils with R-Value of -5 were assigned a relative quality of very poor, as determined by the WFLHD Materials Section in an email dated November 9, 2017.

Testing results showed the subgrade moisture contents to be close to optimum throughout the project. Asphalt cores were not taken.

MDT performed tests to determine chemical and corrosive properties on samples obtained from the subgrade test holes and from soil and water samples collected at culvert locations. Of the thirty-seven (37) tested samples from the 17 subgrade test holes, three (3) were shown to have corrosive characteristics. Of the soil samples collected at culvert locations, 3 out of 17 were shown to be corrosive. Water samples from culverts were shown to be corrosive at two (2) locations. A summary of the corrosive properties pertaining to the locations near the culverts scheduled for replacement is presented in Table 1. More complete information resulting from the MDT corrosion tests is provided in Attachment 3 and discussed later in the next section as pertinent to the discussions for the individual culvert locations.

Table 1: MDT Test Samples Shown to be Corrosive

MDT

Hole

Approx.

MP /

Ref. to

CL

MDT

Sample

Type of

Sample

Sample

Depth, ft

Corrosive to Zinc &

Steel

Corrosive to

Aluminum

Alkali

Reactive to

Concrete

Acid

11 5.5 / EB H11S1 Subgrade 2.5 – 4.0 Yes Yes No No

15 7.5 / EB H15S1 Subgrade 2.5 – 3.5 Yes No No No

16 8.0 / WB H16S2 Subgrade 3.0 – 6.0 Yes No No No

-- 28+65 28+65 Culvert

Soils

-- Yes No No No

-- 114+40 114+40 Culvert

Soils

-- Yes No No Yes

-- 293+22 293+22 Culvert

Water

-- Yes No No 0

-- 357+00 357+00 Culvert

Soils

-- Yes No No No

-- 435+56 435+56 Culvert

Water

-- Yes No 0 0

CULVERTS & LOCAL CONDITIONS

Three culverts are scheduled for replacement on the project. The 70% plan set dated March 7, 2018 shows that 16 feet (span) by 5 feet (rise) precast concrete box culverts are planned at 293+61 (≈ MP 5.49) and 374+92 (≈ MP 7.03). In addition, a 24-inch equivalent diameter arch or elliptical pipe culvert is planned to replace the existing CMP culvert at 435+50 (≈ MP 8.18).

Figure 4 shows the relative location of the culverts scheduled for replacement. All culvert replacement locations are in the upper half of the project. The individual culvert locations are discussed under this section. The discussions include information that is pertinent to each site based on the desk study and the MDT investigations. Photos of the culvert sites (293+61 and 374+92) are presented in Attachment 3 along with excerpts from the NRCS soil mapping (discussed earlier) that show the culvert locations and nearby MDT investigation locations, and the MDT Culvert Inspection Report. Note that we were unable to locate any photos of the culvert at Station 435+50.

Figure 4: Culverts scheduled for replacement shown relative to the start and end of project

Culvert at Station 293+61 (Precast Concrete Box)

Reference to the NRCS soil maps in Attachment 3 shows this culvert to be within the soil map unit named Fluvaquentic Haplaquolls, with Map Unit Symbol (MUS 105). Regrettably, the soil survey report does not provide information regarding the typical profile for this soil map unit;

although, it’s setting type is described as a floodplain landform. Photos of this culvert site appear in the attachment as A3-1 through A3-4.

It can be noted that the soil map units Straw Clay Loam (MUS 210) and Burnel Silty Clay Loam (MUS 33) are located adjacent to this soil unit and nearby the culvert, with setting types of floodplain and alluvial fans/stream terraces, respectively. The typical profiles for each of these are shown below. (Limits shown are inches from the surface.) More complete information regarding the soil units is found in the Soils Resource Report in Attachment 1.

Straw Clay Loam (MUS 210): Burnel Silty Clay Loam (MUS 33):

0 to 16; clay loam 0 to 6; silty clay loam

16 to 35; loam 6 to 21; silty clay

35 to 60; silty clay loam 21 to 50; silty clay

50 to 66; stratified silty clay loam to fine sandy loam

MDT subgrade test hole H11 was drilled at MP 5.5 (≈ 293+96, +/- 500 feet ), nearby this culvert, but may be located in a different soil unit. Reference to the MDT test results in Attachment 2 show that three (3) samples underwent testing from this test hole. The test samples were obtained at 2.5’ to 4.0’, 4.0’ to 6.5’ and 6.5’ to 8.0’ below ground surface (BGS) with the tests showing AASHTO soil classifications of A-4, A-6 and A-2-6, respectively, thus indicating AASHTO general ratings of subgrade as fair, poor, and good, respectively, at the test hole location and to the depth of the test hole. This hole was shown to be corrosive to zinc and steel and to aluminum as seen in Table 1 and in Attachment 3.

The MDT Culvert Inspection Report identified a culvert at 293+22 in May 2013 described as three old pipes with one new one added. This is assumed to be the same culvert location shown in the 70% plan set as 293+61. The general condition of the culverts was reported as good; however, the water was shown to be corrosive. This was confirmed by MDT tests on a water sample from the culvert location that was shown to be corrosive to zinc and steel as shown in Table 1.

MDT test hole H10 is located about 0.5 mile back from the MDT H11 test hole, possibly in the Mocmont Very Gravelly Loam soil (MUS 168). Laboratory tests performed on the sample from this test hole showed no potential for corrosion as can be seen in the Summary of Corrosive Properties of Soil Samples in Attachment 3.

The MDT H12 test hole is located approximately 0.5 mile ahead of the MDT H11 hole possibly in the Raynesford-Hanson Complex (MUS 184) or Sudworth-Nesda Loams (MUS 213) map units. Laboratory test results from this hole did not show potential for corrosion.

Culvert at Station 374+92 (Precast Concrete Box)

Reference to the NRCS soil map excerpts in Attachment 3 show this culvert to be within the soil map unit named Nesda Variant Complex, with MUS 177 and floodplain setting type. The typical profile is shown below with the limits shown in inches from the surface. Photos appear in the Attachment as A3-5 and A3-6.

Nesda Variant Complex (MUS 177):

0 to 6; very gravelly loam

6 to 20; extremely gravelly loam

20 to 60; extremely gravelly sandy loam

MDT subgrade test hole H14 was drilled at MP 7.0 (≈ 373+16 +/- 500’ assumed). Reference to the MDT test results in Attachment 2 show that four (4) samples from this test hole were tested.

The 4 samples were obtained at 2.5’ to 3.5’, 3.5’ to 4.5’, 4.0’ to 4.5’ and 4.5’ to 7.0’ BGS. The test results show AASHTO soil classifications of A-6 for the first 3 samples and A-2-4 for the sample obtained at 4.5’ to 7.0’. According to AASHTO, the test results indicate a general rating for subgrade of poor down to about 4.5 feet BGS and then good between 4.5 feet and 7.0 feet BGS at the test hole location.

The culvert inspection report identified a culvert at 374+85 and is assumed to be the same location shown in the 70% plans as 374+92. The general condition of this culvert was good in May 2013 and no comment was provided regarding corrosion.

The Summary of Corrosive Properties of Soil Samples data sheet in Attachment 3 does not show that a sample of soil or of water was collected directly from this culvert location; however, the MDT laboratory tests performed on the samples taken from the H14 test hole located nearby did not show potential for corrosion. The sample tested 0.5 mile back, (MDT H13 @ MP 6.5 in the 185 MUS soil unit), also showed no corrosive potential. Conversely, one of the samples that underwent laboratory testing from the H15 SG hole drilled about 0.5 mile ahead at MP 7.5 (and mapped within the same soil unit as this culvert) did show potential for corrosion to zinc and steel.

Culvert at Station 435+50 (Equivalent diameter arch or elliptical pipe)

Reference to the NRCS soil map excerpts in Attachment 3 show this minor culvert to be within the soil map unit named Libeg flaggy loam (MUS 147) in a mountain slopes landform setting and a typical profile as shown below. The limits shown below are stated in inches as measured from the surface. We were unable to locate photos for this culvert location.

Libeg Flaggy Loam (MUS 147):

0 to 5; flaggy loam

5 to 20; very channery clay loam

20 to 60; extremely cobbly clay loam

For reference, flaggy soil material is described in the NRCS report as material that has, by volume, 15 to 35 percent flagstones, and Channery soils are described as soil material that has, by volume, 15 to 35 percent thin, flat fragments of sandstone, shale, slate, limestone, or schist as much as 6 inches (15 centimeters) along the longest axis. A single piece is called a channer.)

Note that the soil map unit Nesda Variant Complex (MUS 177) is located nearby to the south.

The Nesda Variant Complex was described previously under the section describing the Culvert at 293+61.

MDT subgrade test hole H17 was drilled at MP 8.5 (≈ 452+36 +/- 500’, assumed). Reference to the MDT test results in Attachment 2 show that three (3) samples from this test hole underwent testing. The test samples were obtained at 2.5’ to 3.0’, 3.0’ to 5.5’ and 5.5’ to 7.0’ BGS. The test results show AASHTO soil classifications of A-6 for the first two samples and A-2-6 for the sample obtained between 5.5’ to 7.0’. According to AASHTO, the soils classifications obtained from the tests indicate likely poor subgrade conditions to about 5.5 feet BGS and then good between 5.5 feet and 7.0 feet BGS at the location of the test hole.

The MDT Laboratory tests from test hole H17 did not indicate corrosion potential as can be seen in Attachment 3.

The MDT Culvert Inspection Report showed this culvert (MDT culvert location @ 435+56) to be in poor condition in May 2013. Tests performed on soil and water samples from this culvert site were performed with the test on the water sample shown to be corrosive to zinc and steel.

MDT subgrade test hole H16 is located in the 177 soil unit about 0.5 mile back from the H17 test hole. Tests performed on one of the two H16 soil samples tested showed corrosive potential to zinc and steel.

DESIGN RECOMMENDATIONS

The results of the laboratory tests should be considered when specifying culvert construction materials. The 70% plan set dated March 9, 2018 shows the planned culverts located at 293+61 and 374+92 to be replaced with precast concrete box type culverts, which should be appropriate considering that none of the MDT laboratory tests showed the soils (or water samples) to be alkali reactive to concrete. In addition, the plan set calls for an equivalent diameter arch or elliptical pipe at 435+50. The MDT laboratory result from the water sample obtained from that site tested positive for corrosion to zinc and steel, which must be considered when selecting pipe materials at that location. (The MDT Corrosive Properties Test Result Summary Table is presented in Attachment 3.)

To our knowledge none of the subgrade investigation holes were drilled at the locations where culvert replacements are planned. Subsurface conditions at the culvert locations are inferred based on the available data, and as such adopting a level of uncertainty is prudent. Given the variability of the type of soils present near the culverts and the fact that the type of investigation performed by the MDT does not indicate relative density or consistency of the in-situ soils (discussed earlier), and the likelihood or possibility of encountering poor subgrade conditions, we make the following conservative recommendations based on assumed poor subgrade conditions for the bearing capacity at all culvert locations.

Factored Bearing Capacity ≤ 0.5 tsf (≤ 1.0 ksf).

The factored bearing capacity was determined based on the methodology presented in the AASHTO Bridge Design Specification and using the results of the MDT subgrade exploration program and laboratory test results, information obtained from the NRCS soil survey, and professional judgement.

Assuming poor subgrade conditions, we recommend allowing for placement of 2 feet of foundation fill beneath the culvert foundation elevations that is separated from the native soils by a separation and stabilization geotextile to provide additional stability and to prevent the migration of the fine-grain in-situ soils. The geotextile should extend up all sides of the excavation. Additional subexcavation may be required as discussed below.

With little exception, the laboratory test results from the MDT test holes near the culvert locations do not show that the tested materials meet the requirement for unclassified borrow.

Because of this, and the uncertainty as to the type of soils that will be encountered at the culvert locations, we recommend that all excavated soils at the these locations be wasted appropriately.

CONSTRUCTION CONSIDERATIONS

The results of our desk study and the results of the MDT Preconstruction Soil Survey Investigation resulted in a reasonable likelihood that clayey soils could be encountered at the footing elevations of the culverts planned for the project. The Contractor must be prepared to excavate into and complete construction in clayey soils of unknown consistency to achieve the required design. It is assumed that all excavated materials below the basecourse will be wasted in accordance with the contract requirements.

Additional subexcavation may be necessary at the culvert locations depending on site conditions. The Contractor should be prepared to perform additional subexcavation as directed by the CO. It is recommended that the project Geotechnical Engineer be contacted to provide specific recommendations in this case.

The groundwater locations are not known based on the type of subsurface investigations performed for the project. Groundwater may be present at the culvert locations during construction. The Contractor should be prepared to dewater for proper construction of the new culverts.

Onsite soils are expected to be moisture sensitive. The Contractor may experience problems with poor support of construction equipment on wet subgrade. The Contractor should be prepared and take steps to manage moisture sensitive subgrade soils, including but not limited to limiting the amount of excavation or subgrade open at one time and use of geogrids and geotextiles and granular materials for equipment support.

REFERENCES

• AASHTO LRFD Bridge Design Specifications, 8th Edition, September 2017

• https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx (Accessed 4/09/2018)

• Geologic Map of the Lewistown 30’ x 60’ Quadrangle, Central Montana; Porter, Karen W.; Wilde, Edith M.; Montana Bureau of Mines & Geology,1999

• Preliminary Line-and-Grade Hydraulics Report, USDOT FHWA WFLHD, James Neighorn, November 30, 2016

• Final Structural Pavement Recommendation Memorandum, USDOT FHWA WFLHD, Maiden Road, MT DOT 14203(1), Stephen Henry, November 9, 2017

CLOSING

Please contact Robert Kraig at (360) 619-7699 or robert.kraig@dot.gov with any questions regarding this memorandum.

RK

https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx mailto:robert.kraig@dot.gov

CC: Keith Wong

Kimber Miller

Jim Neighorn

Denise Steel

Steve Henry

Geotechnical File

Attachments:

• Attachment 1 o Description of Adjacent Geologic Units o NRCS Custom Soil Resource Report

• Attachment 2 o MDT Laboratory Soil Data o AASHTO Soil Classification System o Comparison of USCS with AASHTO

• Attachment 3 o NRCS Soil Mapping Excerpts o NRCS Summary Table o Culvert Photographs o MDT Culvert Inspection Report o MDT Corrosive Properties Test Results

Attachment I Adjacent Geologic Units

NRCS Custom Soil Resource Report

(Intentionally blank)

Adjacent Geologic Units

Descriptions of the Km, Ktf, Kk, Je, TKrp and PZs geologic map units are provided below.

Descriptions of the Ktcm, Qal and TKtp map units are provided in the main body of the memorandum.

Figure 3: Excerpt from the Geologic Map of the Lewistown

30’ x 60’ Quadrangle, Central Montana

Km (Cretaceous): Mowry Shale (Upper Cretaceous)

Contains two distinct lithologies totaling about 165 ft thick; fish scales throughout though not in all intervals. Sandstones: light brown-gray weathering, gray, thin- to thick-bedded, fine- to medium-grained, with thin, dark gray, clayey shale interbeds, forming 2 or 3 ledges or low ridges throughout map area; locally cross-stratified, glauconitic, and up to coarse-grained with chert pebbles in coarse fraction; thin (1/2 to 2 in.) white to orange-stained bentonite beds common throughout. Siltstones: light silvery-blue to white weathering, blue-gray, brittle, thin-bedded siltstone and blue-gray shale with common powdery yellow mineral (jarosite) on bedding planes;

predominantly thin-bedded to laminated, commonly exposed in light-colored barren patches across slopes or ridge tops; generally developed above sandstone interval, but where sandstones poorly developed, may comprise most of formation. Lowermost part of formation, generally not exposed, brown-gray or blue-gray, fissile, laminated and bentonitic shale.

Persistent 2- to 3-ft bentonite bed at base probably is Arrow Creek bed of Reeside and Cobban (1960). Approximate thickness 198 ft (60 m; Lindsey, 1982) .

Ktf (Cretaceous): Thermopolis Formation and Fall River Sandstone, undivided (Lower Cretaceous)

Formations mapped as single unit in areas of steep dip and/or extensive cover, generally north and west of Judith Mountains.

Ktcm

Begin project at US 191 Maiden Road

End project

Kk (Cretaceous): Kootenai Formation (Lower Cretaceous)

Dark to medium red, gray-green and minor buff-colored silty, blocky weathering shale, and fine-to coarse-grained, chert-bearing, feldspathic, commonly cross-stratified sandstone. Thick basal sandstone (up to 100 ft, Vine, 1956; Third Cat Creek sandstone of subsurface) is gray, medium-and coarse-grained, conglomeratic, chert-bearing, cross-stratified. Middle part of formation dominated by varicolored mudstones, predominantly red and yellow-tan; thin, gray-white nodular limestone beds occur locally in section above basal sandstone. Upper part of formation interbedded red mudstones and yellow and brown, thin-bedded, fine-grained, quartzose sandstones with minor chert and feldspar (Second Cat Creek sandstone of subsurface).

Approximate formation thickness in Moccasin Mountains 545 ft (165 m; Lindsey, 1982); in Judith Mountains, 330 to 495 ft (100-150 m; Goddard, 1988).

Je (Jurassic): Ellis Group, undivided (Middle Jurassic)

Includes Piper, Rierdon and Swift formations.

Rierdon Formation & Piper Formation, undivided, Jrp:

Mapped in Moccasin Mountains and in domes southeast of Lewistown only, although recognized in Judith Mountains. RIERDON: yellow weathering, gray-brown calcareous shale and thin-bedded, light gray weathering, gray limestones; locally fossiliferous, dominated by Gryphea sp. and other oysters; formation poorly exposed; thickness estimate in Moccasin Mountains area is 90-120 ft (Lindsey, 1982). PIPER: lithologies highly variable vertically and laterally; soft, pastel red, tan, ochre, green and gray, gypsiferous, blocky shales; interbedded shaly limestones, some oolitic; one or more massive, white gypsum beds; brown weathering, yellow-gray, thin-bedded, fine-grained, calcareous sandstones occur in upper part, forming contact with Rierdon; some black shale and dark gray limestone with underlying lighter-colored shales and gypsum have been included in the Piper by Lindsey (1982); unit poorly exposed; thickness estimate is 297 to 363 ft (90 to 110 m in Moccasin Mountains; Lindsey, 1982); 211 to 320 ft (64 to 97 m in Judith Mountains; Goddard, 1988); 0 to 325 ft south of Lewistown (Gardner, 1959).

Swift Sandstone, Jsw:

Brown weathering, gray, fine-grained to coarse-grained, glauconitic and calcareous sandstone; cross-stratified and ripple-laminated with numerous clay partings; interbedded with thin and lenticular mudstones. Basal few feet of sandstone commonly coarse-grained and conglomeratic, containing chert pebbles, mudstone clasts and abundant broken shell material, particularly of oysters. Sandstone commonly forms resistant ridge or ledge; may occur as several sandstone intervals with intervening mudstones. Base of unit sharp though seldom exposed. Upper beds thin, fine-grained and slabby; contact with overlying Morrison Formation poorly exposed; where Morrison sandstone rests on Swift sandstone, contact is located on basis of mineral composition of sandstones. Formation easily recognized throughout report area where Jurassic rocks are exposed. Estimated thickness in Moccasin Mountains is 66-132 ft (20 to 40 m; Lindsey, 1982); in Judith Mountains 56 ft (17 m; Goddard, 1988); 110 ft southeast of Lewistown (Gardner, 1959).

TKrp (Tertiary): Rhyolite porphyry (Paleocene or Upper Cretaceous)

Phenocrysts of potassium feldspar, plagioclase (albite and oligoclase), quartz, hornblende, and pyroxene in gray groundmass; occurs above Warm Spring Creek at western mountain front, Pyramid Peak, Maiden Peak, and in small hill on valley floor east of Maiden Canyon; locally forms dikes and sills.

PZs (Mississippian or Devonian-Cambrian): Sedimentary rocks, undivided (Lower Paleozoic)

Includes rocks of Cambrian, Devonian, and Mississippian age. Cambrian units include Flathead Quartzite, Pilgrim Limestone, Wolsey Shale, and some unassigned lithologies. Devonian unit is Jefferson Formation. Mississippian units include Madison Group and overlying Kibby, Otter, and Heath formations where not separately mapped. Refer to Goddard (1988) for these units in Judith Mountains; refer to Lindsey (1982) for these units in Moccasin Mountains.

(Intentionally blank)

United States Department of Agriculture

A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants

Custom Soil Resource Report for

Fergus County, Montana Maiden Road Alignment

Natural Resources Conservation Service

April 10, 2018

Preface Soil surveys contain information that affects land use planning in survey areas.

They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers.

Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment.

Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions.

The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations.

Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?

cid=nrcs142p2_053951).

Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations.

The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey.

Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/ http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/ https://offices.sc.egov.usda.gov/locator/app?agency=nrcs http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?cid=nrcs142p2_053951 http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?cid=nrcs142p2_053951 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer.

Contents Preface How Soil Surveys Are Made Soil Map

Soil Map Legend Map Unit Legend Map Unit Descriptions

Fergus County, Montana 14—Alder clay loam, 2 to 8 percent slopes 24—Bitton-Winifred-Castner complex, 15 to 60 percent slopes 27—Brazon-Loken complex, 2 to 15 percent slopes 32—Burnel silty clay loam, 0 to 2 percent slopes 33—Burnel silty clay loam, 2 to 8 percent slopes 37—Cabba-Doney-Wayden complex, 4 to 8 percent slopes 44—Castner complex, 4 to 25 percent slopes 53—Daglum-Adger complex, 0 to 2 percent slopes 60—Darret clay loam, 2 to 8 percent slopes 69—Doney-Windham complex, 15 to 45 percent slopes 82—Enbar loam, 0 to 2 percent slopes 94—Fairfield-Danvers clay loams, 2 to 4 percent slopes 96—Fairfield-Judell clay loams, 2 to 8 percent slopes 97—Farnuf loam, 0 to 4 percent slopes 98—Farnuf loam, 4 to 8 percent slopes 105—Fluvaquentic Haplaquolls, nearly level 106—Frazer silty clay loam 107—Gerber clay loam, 0 to 2 percent slopes 108—Gerber clay loam, 2 to 4 percent slopes 110—Gerber-Winifred clay loams, 2 to 8 percent slopes 120—Hibar-Castner loams, 2 to 8 percent slopes 121—Hibar-Castner loams, 8 to 15 percent slopes 124—Hughesville-Skaggs flaggy loams, 15 to 60 percent slopes 133—Judith-Windham gravelly clay loams, 2 to 8 percent slopes 147—Libeg flaggy loam, 15 to 45 percent slopes 151—Linwell silty clay loam, 0 to 2 percent slopes 152—Linwell silty clay loam, 2 to 8 percent slopes 168—Mocmont very gravelly loam, 15 to 60 percent slopes 171—Mocmont-Oraid complex, 25 to 60 percent slopes 177—Nesda variant complex 178—Nesda-Sudworth complex, occasionally flooded 184—Raynesford-Hanson complex, 0 to 4 percent slopes 185—Raynesford-Hanson complex, 4 to 15 percent slopes 193—Roy gravelly clay loam, 2 to 8 percent slopes 195—Roy-Winifred complex, 8 to 45 percent slopes 197—Savage silty clay loam, 0 to 2 percent slopes

200—Shambo loam, 2 to 8 percent slopes 201—Shambo-Labre complex, 2 to 8 percent slopes 203—Sheege-Rock outcrop complex, 15 to 60 percent slopes 208—Straw loam, 0 to 2 percent slopes 209—Straw loam, 2 to 8 percent slopes 210—Straw clay loam, 0 to 2 percent slopes 213—Sudworth-Nesda loams 218—Tamaneen clay loam, 0 to 2 percent slopes 219—Tamaneen clay loam, 2 to 4 percent slopes 238—Tigeron very gravelly loam, 15 to 60 percent slopes 242—Timberg-Castner complex, 15 to 45 percent slopes 244—Tomty-Delette complex, 8 to 25 percent slopes 245—Turner loam, 0 to 2 percent slopes 261—Whitecow-Hughesville complex, 2 to 20 percent slopes 263—Whitecow-Hughesville-Rock outcrop complex, 45 to 60 percent slopes 264—Whitore-Firada cobbly clay loams, 15 to 60 percent slopes 265—Widen-Hughesville-Lipke complex, 15 to 60 percent slopes 271—Winifred-Castner-Norbert complex, 8 to 45 percent slopes 272—Winifred-Judith clay loams, 4 to 8 percent slopes 273—Winifred-Judith clay loams, 8 to 15 percent slopes 275—Winifred-Windham-Eltsac complex, 15 to 45 percent slopes 276—Work clay loam, 0 to 2 percent slopes

References Glossary

Custom Soil Resource Report

How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity.

Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA.

The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape.

Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries.

Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units).

Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research.

The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas.

Soil scientists make many field observations in the process of producing a soil map.

The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded.

These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape.

Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties.

While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management.

Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil.

Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date.

After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately.

Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit.

Soil Map

620000 621000 622000 623000 624000 625000 626000 627000 628000 629000 630000 631000 632000 633000 634000 635000 636000

620000 621000 622000 623000 624000 625000 626000 627000 628000 629000 630000 631000 632000 633000 634000 635000 636000 637000

47° 14' 1'' N

9°

5'

3' ' W

47° 14' 1'' N

9°

1'

5'

' W

47° 8' 49'' N

9°

5'

3'

' W

47° 8' 49'' N

9°

1'

5'

' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84 0 2000 4000 8000 12000

Feet 0 500 1000 2000 3000

Meters Map Scale: 1:46,900 if printed on B landscape (17" x 11") sheet.

MAP LEGEND MAP INFORMATION

Area of Interest (AOI) Area of Interest (AOI)

Soils Soil Map Unit Polygons

Soil Map Unit Lines

Soil Map Unit Points

Special Point Features Blowout

Borrow Pit

Clay Spot

Closed Depression

Gravel Pit

Gravelly Spot

Landfill

Lava Flow

Marsh or swamp

Mine or Quarry

Miscellaneous Water

Perennial Water

Rock Outcrop

Saline Spot

Sandy Spot

Severely Eroded Spot

Sinkhole

Slide or Slip

Sodic Spot

Spoil Area

Stony Spot

Very Stony Spot

Wet Spot

Other

Special Line Features

Water Features Streams and Canals

Transportation Rails

Interstate Highways

US Routes

Major Roads

Local Roads

Background Aerial Photography

The soil surveys that comprise your AOI were mapped at 1:24,000.

Please rely on the bar scale on each map sheet for map measurements.

Source of Map: Natural Resources Conservation Service Web Soil Survey URL:

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: Fergus County, Montana Survey Area Data: Version 18, Sep 8, 2017

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Jul 19, 2015—Sep 9, 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.

Map Unit Legend

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

14 Alder clay loam, 2 to 8 percent slopes

26.0 0.8%

24 Bitton-Winifred-Castner complex, 15 to 60 percent slopes

120.8 3.6%

27 Brazon-Loken complex, 2 to 15 percent slopes

4.2 0.1%

32 Burnel silty clay loam, 0 to 2 percent slopes

64.7 1.9%

33 Burnel silty clay loam, 2 to 8 percent slopes

67.6 2.0%

37 Cabba-Doney-Wayden complex, 4 to 8 percent slopes

0.0 0.0%

44 Castner complex, 4 to 25 percent slopes

7.2 0.2%

53 Daglum-Adger complex, 0 to 2 percent slopes

18.7 0.6%

60 Darret clay loam, 2 to 8 percent slopes

0.1 0.0%

69 Doney-Windham complex, 15 to 45 percent slopes

17.3 0.5%

82 Enbar loam, 0 to 2 percent slopes

20.7 0.6%

94 Fairfield-Danvers clay loams, 2 to 4 percent slopes

46.8 1.4%

96 Fairfield-Judell clay loams, 2 to 8 percent slopes

1.5 0.0%

97 Farnuf loam, 0 to 4 percent slopes

60.4 1.8%

98 Farnuf loam, 4 to 8 percent slopes

7.4 0.2%

105 Fluvaquentic Haplaquolls, nearly level

103.2 3.1%

106 Frazer silty clay loam 13.4 0.4%

107 Gerber clay loam, 0 to 2 percent slopes

57.3 1.7%

108 Gerber clay loam, 2 to 4 percent slopes

50.1 1.5%

110 Gerber-Winifred clay loams, 2…