The URL can be used to link to this page

Home My WebLink About05- Golder A- WEP 2 Geotech Investigation-11-1 O a w A world of capabilities delivered locally SUMMARY OF GEOTECHNICAL SITE INVESTIGATION North Side of Baxter Pass, Colorado for Western Expansion Project Phase II Submitted To: Enterprise Products Company, Inc./Mid-America Pipeline Co. 1100 Louisiana St. Houston, TX 77002 Submitted By: Golder Associates Inc. 595 Double Eagle Court, Suite 1000 Reno, NV 89521 USA Distribution: 1 Copy — Ricky Bates, Enterprise, Houston 1 Copy — Jill Petersen, Enterprise, Hobbs 1 Copy — Jerry Simmons, Enterprise, Fruita 1 Copy — Brad Kiser, Enterprise, Rock Springs 1 Copy — Graeme Major, Golder, Reno 1 Copy — Golder, Reno March 2012 Project No. 113-91752 Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation Golder Associates March 2012 Table of Contents 113-91752 1.0 SCOPE AND PURPOSE 1 2.0 EXISTING PIPELINES IN WEP2 CORRIDOR 2 3.0 PREVIOUS STUDIES AT THE PROJECT SITE 3 4.0 EXISTING SITE CONDITIONS 4 4.1 Geologic Setting 4 4.2 Geology and Landslide Features of the Proposed HDD Areas 5 4.2.1 Woodpile Landslide 5 4.2.2 Columbine Springs Landslide Complex 6 4.2.3 McAndrews Lake Area 7 5.0 FINDINGS OF SUBSURFACE INVESTIGATION 9 5.1 Subsurface Drilling and Testing 9 5.1.1 Woodpile Landslide: Boring WP -1A and WP -1B 10 5.1.2 Columbine Springs Landslide Complex 10 5.2 Laboratory Testing 11 5.3 Rock Quality Designation 13 6.0 CONCLUSIONS AND RECOMMENDATIONS 14 7.0 CLOSING 16 8.0 REFERENCES 17 List of Tables Table 1 Table 2 Table 3 Table 4 Index Testing Results for Soils UCS and Density Testing Results for Bedrock RQD Index Weighted Average RQD for Sandstone and Siltstone List of Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Site Location Map Woodpile Landslide Area Columbine Springs Landslide Complex McAndrews Lake Area Data From 1998 Terracon HDD Investigation List of Photographs Photo 1 Drilling at location of boring WP -1A. Photo 2 Large boulders on ground surface above proposed pipe alignment List of Appendices Appendix A Boring Logs and Core Photographs Appendix B Laboratory Testing Results s:\enterprise\2011 \2011 columbinesprings\wept\report - final \stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 1 113-91752 1.0 SCOPE AND PURPOSE This Summary of Geotechnical Data for the Western Expansion Project Phase II (WEP2) presents the findings of subsurface investigation and surface reconnaissance mapping of two areas along the WEP2 pipeline alignment planned by Enterprise Products Company, Inc. (Enterprise), where installation of the pipe is proposed using HDD (horizontal directional drilling) techniques. The two areas investigated in this study are known as the Woodpile Landslide and the Columbine Springs Landslide Complex. The locations of these respective areas are shown on Figure 1. The scope of the work was outlined in our proposal "Cost Estimate, WEP2 Drilling Investigation and Columbine Inclinometer Replacement" dated August 26, 2011, and included: • Nine (estimated) exploratory borings at the proposed McAndrews Lake HDD, the Columbine Springs Landslide Complex, and the Woodpile Landslide, • Installation of two inclinometers, in boreholes at Columbine Springs Landslide and Woodpile Landslide, and • Taking baseline readings on inclinometers. The final planned number, locations, and depths of the borings were presented in an addendum to the Geotechnical Engineering Investigation Plan provided by Enterprise entitled "Addendum 1: Project Specific Information for Western Expansion Project Phase II Horizontal Direction Drilling (HDD)" and dated September 1, 2011. In addition to prescribing standards for soil classification and testing in the field and laboratory, the addendum specified that free water levels in borings be recorded, and that other significant observations regarding groundwater during the boring process be recorded. No additional engineering or review services, or scheduled monitoring, are included in the current scope. As described in our cost estimate and Enterprise's Geotechnical Engineering Investigation Plan Addendum 1, a third HDD is proposed at McAndrews Lake, which lies approximately 1.25 miles north of the Columbine Springs Landslide Complex. An existing HDD was constructed for another pipeline in this same area in the late 1990's or 2000. Subsurface information is available from this previous investigation and appears in drawings that were prepared for Mid-America Pipeline Company (MAPCO) and were provided to the current project team by Enterprise. Due to difficulties encountered in the time -constrained drilling program at the other two sites, and the desire not to duplicate the efforts of previous studies, the WEP2, HDD design engineers (Rooney Engineering, Inc.) determined that the information from these previous studies and presented in the MAPCO drawings would provide sufficient geotechnical information for the proposed HDD at McAndrews Lake. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx 41417-4 Golder Iwo Associates March 2012 2 113-91752 2.0 EXISTING PIPELINES IN WEP2 CORRIDOR The proposed WEP2 pipeline is to be constructed within and/or adjacent to the existing pipeline corridor and Right -of -Way (ROW), currently containing a total of four pipelines. These include: • The "Red Line." This pipeline is the older of the two Mid-America pipelines now operated by Enterprise. It was originally completed in 1981, but has been relocated, apparently over a significant length, through the study area. Relocations were recorded as revisions on a drawing dated 1981, with annotations that suggest that leaks occurred possibly in two locations in 1987. • The "Brown Line." This pipeline was apparently completed in the late 1990's as a loop to the Red Line. In most locations the Brown Line is in close proximity to the Red Line. An HDD was drilled for a portion of the Brown Line under McAndrews Lake to avoid the 1985 Landslide. Drawings from the late 1990's site investigation and design for this HDD were provided to us and to Rooney Engineering, Inc. (Rooney) by Enterprise. These drawings include data from a subsurface investigation performed by Terracon Consultants Western, Inc. (Terracon), of Salt Lake City, for the Brown Line HDD. • The "Gilsonite Line." The construction date of the Gilsonite Line is unknown, but was probably in the early to mid -1900s. It was installed as a pipeline to carry rock slurry from Bonanza, Utah to Loma, Colorado. The pipeline has had various owners and has carried various petroleum products. We understand that the line is still operational. In two areas which appear to have a history of landslide movement, the pipe is currently on the ground surface. One of these areas is at Columbine Springs Landslide; the other is the 1985 Landslide. ■ The abandoned portion of the Red Line. This portion of the Red Line was apparently abandoned with re-routing of the Red Line as indicated on revisions to the 1981 drawing. It parallels the existing corridor, west and uphill of the active pipelines, for a distance of about 1.5 miles. The proposed WEP2 pipeline is very close to this line in many places. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx 41417-4 Golder Iwo Associates March 2012 3 113-91752 3.0 PREVIOUS STUDIES AT THE PROJECT SITE As described above, a previous subsurface investigation was performed in the immediate area of the proposed HDD at McAndrews Lake. According to the 1998 Mid-America Pipeline drawings, the investigation was completed by Terracon Consultants Western, Inc. Efforts to locate copies of the full report by Terracon were not successful. However, following discussions of this information, the HDD design engineers (Rooney) determined that the information included on the 1998 drawings would be sufficient for their purposes. Golder Associates Inc. (Golder) has been involved in monitoring of the landslide areas north of Baxter Pass since 2004. Activities have included surface mapping of landslide features, annual walking of the existing pipeline corridor to look for evidence of significant changes or renewed movement, installation and monitoring of slope inclinometers, and installation of strain gages on the pipes in key locations. Figures 2 and 3 present observations of reconnaissance surface mapping conducted during the WEP2 drilling investigation, as well as previous site mapping and observations. Appendix A includes the boring log for an inclinometer that was placed in the Columbine Springs Landslide area during a previous Golder study, in addition to the boring logs from the current study, since this information may be a helpful supplement to the current investigation. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx 41417-4 Golder Associates March 2012 4 113-91752 4.0 EXISTING SITE CONDITIONS 4.1 Geologic Setting Between the summit of Baxter Pass and a point downstream of McAndrews Lake, the proposed WEP2 alignment crosses an area of known landslides, some of which are recently or currently active. In some locations, relatively recent landslide movements have damaged or broken existing pipelines. Nearly the entire valley bottom from immediately above the Woodpile Landslide Area to McAndrews Lake is covered by landslide deposits. Over time, the landslides from either side of the valley have coalesced to fill the narrow valley, in some areas forming ponds or boggy ground, and in other areas exhibiting steep, deeply - incised stream cuts. Where the stream is down -cutting through these deposits, steep creek banks have formed. Ongoing erosion of these creek banks has contributed to shallow slumping in many areas, and also acts as a driving mechanism for further movement of existing landslides. Where more stable flat areas have formed from the coalesced slides, the landslide deposits act to buttress the toes of older slides along the lower portion of the valley slopes. The portion of the planned WEP2 alignment north from the summit of Baxter Pass to McAndrews Lake is located near the valley bottom of the generally north -south -trending drainage of West Evacuation Creek (Figure 1). Near the summit of the pass and in the upper part of the valley above McAndrews Lake, the alignment is on the east flank of the valley. At an open meadow about 1/2 mile below the Columbine Springs Landslide area, the alignment shifts to the west side of the valley floor. The elevation of McAndrews Lake and the lower part of the valley is about 7,100 feet above mean sea level (amsl). The valley is flanked to the northeast and southwest with flat-topped ridges that exceed 8,600 feet amsl. The summit of Baxter Pass is at about 8,400 feet amsl. Overall slope angles on the southwest -facing slopes range from about 15 to 25 degrees (27-47 percent) below about 8,000 feet amsl to as much as 34 to 45 degrees (67-100 percent) above 8,000 amsl. Based on the geologic mapping of Cashion (1973), Johnson (1985), and Stover (1992), the McAndrews Lake and Baxter Pass area is underlain by late Cretaceous (66 to 97 million years old) and early Tertiary (37 to 66 million years old) sedimentary bedrock that is overlain by Quaternary (past 1.6 million years) surficial deposits. The bedrock stratigraphy includes, from oldest to youngest, the Mesa Verde Group, which is overlain by the Wasatch Formation, which is in turn overlain by the Green River Formation. The sedimentary bedrock units are nearly flat -lying, but locally faulted (Johnson, 1985). The Mesa Verde Group is mapped locally near the floor of West Evacuation Creek Valley (below about elevation 7,300 amsl), south and southeast of McAndrews Lake (Johnson, 1985). The Mesa Verde Group consists mainly of gray, fine grained sandstone, gray silty shale, carbonaceous shale, and coal (Johnson, 1985). The sandstone is commonly white near the contact with the overlying Wasatch Formation. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 5 113-91752 The Wasatch Formation is about 200-600 feet thick in the Baxter Pass area (Johnson, 1985). It consists mostly of purple, maroon, and gray massive mudstone with lenticular sandstone beds. The individual sandstone beds may be as much as 50 feet thick (Johnson, 1985). Nearly all the landslides in the Baxter Pass and McAndrews Lake area originate in the Wasatch Formation, near the contact with the overlying Green River Formation (Johnson, 1985; Stover, 1992). Based on the mapping of Johnson (1985), the Green River Formation underlies the ridge crests in the Baxter Pass and McAndrews Lake area, and forms the steeper, uniform upper slopes (Stover, 1992). The Green River Formation includes rust -colored to gray and olive gray, dolomitic marlstone (oil shale), limestone, sandstone, and siltstone. The mapped Quaternary surficial deposits in the McAndrews Lake and Baxter Pass area primarily include Holocene (past 10,000 years) floodplain alluvium, Holocene alluvial fan and debris fan deposits, and late Pleistocene (10,000-32,000 years ago) and Holocene landslide and slump deposits (Stover, 1992). The floodplain alluvium fills the West Evacuation Creek Valley to thicknesses of 3-30 feet, and consists of sand, silt, and clay interbedded with gravel lenses. The landslide deposits generally consist of mixed deposits of clay, silt, sand, cobbles, and boulders. However, large torvea (slump) blocks that have detached from the cliffs often consist of relatively intact sediments from their parent formations. Typically, the landslides have failed within the Wasatch Formation, sometimes undercutting the overlying Green River Formation and causing it to fail also. The general landslide types that occur on the slopes include earthflows, debris flows, and rotational slumps (Stover, 1992). 4.2 Geology and Landslide Features of the Proposed HDD Areas The following sections provide more detailed discussion of the conditions specific to the proposed HDD areas, going from south to north. These discussions include pertinent conclusions based on the subsurface drilling described below in Section 5.0, as well as surface reconnaissance conducted during and prior to the 2011 field studies. 4.2.1 Woodpile Landslide The Woodpile Landslide is located approximately one mile north of the summit of Baxter Pass, at the uppermost (up -valley) limit of landslide deposits in this valley. Geologically, it lies near the top of the Wasatch Formation. Immediately above the Woodpile Landslide, limestone, siltstone, and sandstone deposits of the Green River Formation can be seen. Figure 2 presents observations at the Woodpile Landslide area, including observations of reconnaissance surface mapping conducted during the WEP2 drilling investigation, as well as site mapping and observations from studies conducted by Golder prior to 2011. As indicated on Figure 2, there is an area of more recent landslide activity contained within a larger area of less recent landslide movements. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 6 113-91752 However, it should be noted that much of the area shown on Figure 2, beyond the limits of recently active movements, consists of older landslide deposits which appear to be dormant under current site conditions. Disturbance of the areas outlined as having recent or historic landslide movements should be avoided during pipeline construction. A detail map of the immediate area around the Woodpile Landslide is shown in Figure 2, including approximate boundaries of the most recent landslide features as well as the location of boring WP -1. Although nearly the entire area covered in this map is characterized by landslide deposits, or by steep slopes which are scarps associated with the landslides, most of the landslide deposits are older and considered to be inactive at the current time. However, all of these deposits are at risk of renewed ground movements capable of damaging pipelines, should they be unduly disturbed by human activity, or subject to changing climate conditions such as higher groundwater or accelerated erosion from surface water. As shown on Figure 2, the area of landslide deposits that we believe to present the greatest risk to the proposed new pipeline extends from about Station 4+00 to Station 8+00 of the HDD profile as presented in the Rooney drawing dated 8/31/11. Within that area is the most recently active slide mass, extending from about Station 4+20 to 6+40. Movements in this portion of the slide damaged the existing, abandoned pipeline. 4.2.2 Columbine Springs Landslide Complex The Columbine Springs Landslide Complex lies approximately 1,600 to 3,500 feet down -valley from the Woodpile Landslide (Figure 3). It is an area that includes multiple types of landslide features with various ages. The most recent of these features, which impacted the existing pipelines, exhibits evidence of activity during the spring/summer season of 2011 in the form of fresh cracking and scarp enlargement. Other landslide features in the Columbine Springs Landslide Complex include: • an area of apparent shallow -seated movement immediately above the abandoned pipeline that sheared off an existing inclinometer within the past year, • large, older landslide blocks which extend to the west and south of the most recently active area, • a drainage swale which appears to form the upslope boundary of the lowermost older slide block, • a slump and scarp downslope of the existing, relocated "Red Line" pipeline which appears to have evidence of movement within about the past 5-15 years, and • shallow sloughing/slumping of the creek bank which suggests the potential for ongoing bank erosion to initiate further ground movements in the slope immediately above. Therefore, the Columbine Springs Landslide Complex is considered to be a significant risk to pipelines through the area. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 7 113-91752 The existing "Red Line" and "Brown Line" pipelines are equipped with strain gages for the purpose of monitoring the effects of possible ground movements on the pipes. Concurrent with the WEP2 subsurface investigation, the Red and Brown Lines were excavated to allow relief of possible accumulated strains in the pipe within the lower (north) portion of the Columbine Springs Landslide area. Figure 3 presents observations at the Columbine Springs Landslide Complex area, including observations of reconnaissance surface mapping conducted during the WEP2 drilling investigation and the locations of the WEP2 investigation boreholes, as well as site mapping and observations from studies conducted by Golder prior to 2011. As indicated on Figure 3, there are several areas of more recent landslide activity contained within a larger area of older landslide movements. However, it should be noted that much of the area shown on Figure 3, beyond the limits of recently active movements, consists of older landslide deposits which appear to be dormant under current site conditions. The most obvious area of recent landslide activity is the lobe between about station 8+00 and 9+00 of the proposed HDD alignment. Recent ground movements have also been detected over the past several years between about stations 9+00 and 12+50. We recommended that no undercutting or other disturbance of this sensitive area occur during pipeline construction. However, there is also a smaller area of recent slope movements in the existing right-of-way cut between about station 3+00 and 4+00. This feature indicates the meta -stable condition of the relatively high, steep cuts through this area of the existing pipeline corridor. Conventional trench construction through this area would be at risk of further destabilizing these older landslide deposits. We recommend that pipeline construction be conducted through this area in a manner that creates as little disturbance as possible of these slopes. 4.2.3 McAndrews Lake Area Landslides are also present along the east side of McAndrews Lake, including the "1985 Landslide" which damaged the "Red Line." At the 1985 Landslide, strain gages are now in place on the pipeline for monitoring strain in the pipe, and an inclinometer is in place for monitoring potential future ground movements. Other areas of recently -active landslide movement include the "Hairpin Landslide," southeast of the lake. Figure 4 shows the landslide areas in relation to the lake and to the proposed HDD. No specific mapping was conducted in this area during the 2011 investigation. The landslide limits shown in Figure 4 are based on other mapping, reconnaissance, and observations by Golder prior to 2011. An existing HDD was constructed for another pipeline in this same area in the late 1990's or 2000. Subsurface information is available from this previous investigation and appears in drawings prepared for MAPCO, and provided to the current project team by Enterprise. Figure 5 presents the available data from the MAPCO drawing, from the subsurface investigation by Terracon. The estimated locations of boreholes from the Terracon investigation, as approximately scaled from the MAPCO drawings, are also shown on Figure 4 in relation to the proposed HDD profile. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 8 113-91752 The Terracon information indicates that significant deposits of overburden soils, up to about 55 feet below ground, are present at most of the boring locations. Most of the borings penetrated clay just below the ground surface, but some found sand, gravel, and cobbles before encountering bedrock. Although it is not specified in the available Terracon information, we believe that the rocks encountered at depth in the immediate area of McAndrews Lake, and penetrated by all of the borings MAC -1 through MAC -5, are most likely of the Mesa Verde Group. Data on rock strength, from unconfined compressive strength testing, is provided with the Terracon information for the "Short Alternative" but not for the originally proposed crossing. We note that the data plotted down the right side of the drillhole traces in the drawings is the logged "Moh's Hardness," an index of relative mineral strengths. The Moh's Hardness is not equivalent to the ISRM rock strengths included in this report, and usually used in geotechnical investigations. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx 41417- Golder Associates March 2012 9 113-91752 5.0 FINDINGS OF SUBSURFACE INVESTIGATION The subsurface investigation, which consisted of drilling, sampling, and testing to obtain geotechnical information for WEP2 design, was conducted from September 20 to October 1, 2011. The work included completion of five borings at four locations; one location (2 borings) at the Woodpile Landslide, and three borings within the Columbine Springs Landslide Complex. Samples of both soil and rock were obtained during the drilling, and were taken to Golder's laboratory in Lakewood, Colorado, for testing. No free static groundwater table was observed in any of the borings during the investigation. However, drillers usually have difficulty distinguishing when groundwater has been encountered during mud rotary coring. There is considerable evidence of perched and/or shallow groundwater in the landslide areas. Trench excavations would likely encounter shallow groundwater, the presence of which is likely to vary considerably from place to place and with the seasonal conditions at the time of construction. Driest conditions would be expected in late summer and early fall, while spring and early summer may be characterized by wetter conditions. 5.1 Subsurface Drilling and Testing The approximate locations of the borings are shown on Figures 2 and 3. Complete logs of the borings are presented in Appendix A. Appendix A also includes photographs of the rock core recovered during the drilling. The drilling was conducted by Ager Drilling Services, of Yampa, Colorado. The exploratory borings were advanced using a CME -55 drill, mounted on a Bombardier Muskeg low ground pressure track rig. Overburden soils were drilled initially (WP -1A) using hollow -stem augers. However, due to drilling difficulties with boulders in the soils, the driller switched to solid -stem augers for the remainder of the borings. Coring was done using wireline equipment, with HQ core barrels. The borings were drilled to depths of approximately 36 to 95 feet below the existing ground surface. Each of the borings was logged in the field by a Golder Geotechnical Engineer. During the drilling, the materials encountered were visually classified. Bulk and relatively undisturbed soil samples, and selected segments of rock core, were collected for further evaluation and geotechnical testing. Where bedrock was encountered, core was recovered, boxed, and photographed. The boxed core was placed in storage by Enterprise Products at their Dragon Station facility north of the project site. Inclinometers were placed in two of the borings; WP -1 B, and CS -2. The purpose of the inclinometers is to allow monitoring of subsurface ground movements in the landslide areas. Although the inclinometers were placed primarily to supplement or replace existing instrumentation for the existing pipeline operated by Enterprise, they may also provide useful information through these areas should portions of the proposed pipeline be constructed by conventional trenching. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 10 113-91752 5.1.1 Woodpile Landslide: Boring WP -1A and WP -1B The boring drilled at the Woodpile Landslide (WP -1, see Photo 1) encountered weathered bedrock of the Wasatch Formation underlying 28.5 feet of landslide deposits. The uppermost 13 feet of the landslide deposits were noticeably softer than those below, and thus this depth is interpreted to be the thickness of the most recently -moved landslide mass. The landslide deposits at Woodpile Landslide were found to contain a significant quantity of large cobbles and boulders. Some of these are very hard, cemented sandstone or limestone, and others are of softer sandstone or siltstone; these are characteristic rocks of the Green River Formation lying above the slide area. These boulders are believed to be debris from the landslide scarp which was entrained in the slide deposits at the time of initial movement. Thus they would be expected to occur randomly in the slide deposits, and be of varied size. Photo 2 shows two very large boulders that were observed above the existing ROW, approximately 700 feet north of Woodpile Landslide. Although these particular boulders are likely the product of rockfall landing on the ground surface subsequent to landslide movement, there is the potential for similar -size material to be found in the subsurface as part of the landslide deposits. Due to boulders encountered in the drilling at WP -1, two attempts were required to complete the drilling at WP -1. The initial boring encountered a hard boulder from 15.5 to 16.5 feet which the auger was able to grind through with difficulty. However, borehole deviation resulting from this boulder and smaller ones resulted in mis-alignment of the hole such that the coring equipment could not be effectively used. Coring was attempted starting at about 24 feet in the first boring (WP -1A) and approximately 2 feet of very hard limestone and hard sandstone were recovered, later determined to be a boulder within the landslide deposits. Due to the mis-alignment difficulties, the initial boring was abandoned and a new boring (WP - 1 B) was started approximately 6 feet to the north of the first one. The second attempt was successful in reaching, and subsequently coring, bedrock below the landslide deposits. Bedrock encountered in boring WP -1B included interbedded siltstones and claystones of the Wasatch Formation. From 28.5 to about 44.3 feet, the bedrock was highly weathered, and more competent bedrock was encountered below 44.3 feet to the bottom of the boring at 67.5 feet. The Wasatch Formation also contains lenses of relatively resistant sandstones which can be up to 50 feet thick (Johnson, 1985), although none was encountered in this boring. 5.1.2 Columbine Springs Landslide Complex Three boreholes were drilled at the Columbine Springs Landslide Complex as part of the WEP2 subsurface investigation. Locations of the borings are shown on Figure 3. Borehole CS -2 was drilled adjacent to the recent landslide lobe, near the middle of the proposed HDD. It penetrated landslide deposits to a depth of about 39 feet, where it encountered siltstone, claystone, and sandstone of the s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 11 113-91752 Wasatch Formation. The landslide deposits transitioned from stiff to very stiff between about 16 and 19 feet, suggesting that the likely depth of the most recently -active landslide mass is no more than about 19 feet at that location. At the bottom of the boring, from about 89 to 95.3 feet, the rock encountered was a relatively resistant and hard, well -cemented conglomeratic sandstone. Boring CS -3 was drilled near the uphill (south) end of the proposed HDD. This boring penetrated about 38 feet of landslide deposits before encountering highly weathered bedrock of the Wasatch Formation. The landslide deposits transitioned from stiff to very stiff between about 15 and 18 feet, suggesting that the likely depth of the most recently -active landslide mass is no more than about 18 feet at that location. From a depth of about 41.5 to the bottom of the boring at 87 feet, interbedded claystone and siltstone of the Wasatch Formation was encountered. Boring CS -1 was drilled near the downhill (north) end of the proposed HDD. Landslide deposits were penetrated to a depth of about 17 feet at CS -1. Significant organic material was included in the samples recovered from 8 to 9.5 and 13 to 14.5 feet. Landslide deposits were logged as soft to a depth between 9.5 and 13 feet. Between 13 and 17 feet, the deposits transitioned from soft to very stiff, suggesting that the likely depth of the most recently -active landslide mass is no more than about 17 feet at that location. However, movements at this location are likely older than at CS -3 and WP -1. From 28.5 feet to the bottom of the boring at 36 feet, the drilling encountered claystone, siltstone, and sandstone of the Wasatch Formation. Although a few rocks were encountered in the landslide deposits in these borings, they were not as frequent or as large as those found at Woodpile Landslide. Although this may be simply due to the randomness that is characteristic of boulders in the landslide deposits, it may also be that there are fewer large boulders in the deposits at Columbine Springs, since this landslide is located deeper in the Wasatch Formation where it is possible that less material from the overlying Green River Formation was entrained during initial landslide movement. 5.2 Laboratory Testing The laboratory testing program included the testing of in-situ moisture content, dry density, grain size distribution, Atterberg limits, and rock strength testing. Unconfined Compressive Strength (UCS) testing was performed on rock core samples to characterize the strength of the rock materials. Laboratory test results are presented in Appendix B. Index testing results for the soil samples are summarized in Table 1. All of the samples were of landslide deposits except for CS -3@28.0-29.5 feet, which is a sample of weathered claystone of the Wasatch Formation. The test results indicate that the sampled soils are clays and sandy clays of low plasticity. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 12 113-91752 Table 1: Index Testing Results for Soils Borehole ID Depth (ft) USCS* Soil Classifi- cation Moisture (%) Atterberg Limits Grain Size Distribution LL PL PI % Finer 3/4" % Finer #4 % Finer #200 WP -1A 14.6-15.2 CL 23 40 23 17 100 100 98 CS -1 13.0-14.5 CL 20 33 16 17 100 100 51 CS -2 9.0-10.5 NA NA NA NA NA 100 100 75 CS -2 24.0-25.5 CL NA 41 18 23 100 100 78 CS -3 8.0-9.5 NA 21 NA NA NA 100 98 83 CS -3 13.0-14.5 CL 25 46 21 25 100 98 78 CS -3 28.0-29.5 NA 20 NA NA NA 100 100 75 *Unified Soil Classification System UCS and density testing were performed on samples of Wasatch Formation siltstone and sandstone. UCS values for sandstone ranged from 670-1,513 psi (Table 2), with an average UCS of 700 psi and a standard deviation of 748 psi. This average UCS corresponds to a Very Weak Rock (R1) according to the International Society of Rock Mechanics (ISRM) rock strength classification system. Siltstone UCS values ranged from 139-1,591 psi (Table 2). The average UCS of the siltstone is 1,129 psi, which corresponds to a Weak Rock (R2). The standard deviation of the siltstone UCS values is 427 psi. The density testing results are shown in Table 2. Average dry density is 124 pcf for sandstone, and 134 pcf for siltstone. Standard deviations for the density measurements are 13 and 10 for sandstone and siltstone, respectively. Table 2: UCS and Density Testing Results for Bedrock Borehole ID Depth (ft) Rock Type Formation UCS (psi) ISRM Strength Dry Density (pcf) WP -1B 50.2-50.7 Siltstone Wasatch 139 RO 132.6 CS -1 33.5-34.0 Siltstone Wasatch 159 R1 127.4 CS -2 72.0-72.5 Siltstone Wasatch 1,437 R2 126.3 CS -2 84.0-84.5 Sandstone Wasatch 670 R1 114.6 CS -2 85.2-85.7 Sandstone Wasatch 1,205 R2 118.6 CS -2 88.3-88.9 Sandstone Wasatch 1,513 R2 139.7 CS -3 66.25-66.75 Siltstone Wasatch 176 R1 133.7 CS -3 86.3-87.0 Siltstone Wasatch 1,591 R2 150.4 s:\enterprise\2011 \2011 columbinesprings\wep2\report - final \stamped final report 3-2012\wep2 geotech i nvestigation.docx Golder Associates March 2012 13 113-91752 5.3 Rock Quality Designation Rock Quality Designation (RQD, a modified core recovery index in which only sound core recovered in lengths of 4 inches or greater is counted as recovery) values rate rock quality on a scale of 0 to 100, with 90-100 being Excellent quality rock (Table 3). Table 3: RQD Index RQD (%) Rock Quality <25% Very Poor 25-50% Poor 50-75% Fair 75-90% Good 90-100% Excellent RQD was logged for each core run in the bedrock, and is included in the core logs. Weighted average RQD was calculated for the main rock types encountered, sandstone and siltstone, as shown in Table 4. Table 4: Weighted Average RQD for Sandstone and Siltstone Lithology Weighted Average RQD (%) Feet of Core Drilled Sandstone 51 22 Siltstone 80 110 The core logging indicates the sandstone encountered is Fair quality rock and the siltstone encountered is Good quality rock. We note that relatively little sandstone was intersected during drilling, and the weighted average RQD in Table 4 may not be representative of the sandstone as a whole in the area of the boreholes. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Iwo Golder Associates March 2012 14 113-91752 6.0 CONCLUSIONS AND RECOMMENDATIONS This report presents a summary of information obtained during the 2011 site investigation for the proposed WEP2 pipeline alignment, specific to the design of the proposed HDDs. The alignment crosses areas of active or recently -active landslides and ground movements, and/or areas that are considered to be potentially active during the design life of the pipeline, at the Woodpile Landslide and the Columbine Springs Landslide Complex. HDDs are proposed at these locations. Key findings of the investigation are summarized as follows: • Overburden soils at both the Woodpile Landslide and the Columbine Springs Landslide Complex consist of landslide deposits. The depth of these deposits ranged from about 18 to 39 feet at the locations drilled. The soils are composed of a mixture of clay, silt, sand, and gravel, but are dominated by fines. The soils also contain randomly -distributed cobbles and boulders. • The size and frequency of boulders occurring within the landslide deposits is expected to vary from place to place. Boulders encountered in the subsurface during drilling ranged up to about 2.5 feet in dimension. Boulders observed on the ground surface suggest that sizes in the range from 1 to 3 feet are likely common in the landslide deposits, but may range up to 6 feet or more in diameter. Some of these boulders are of very hard, resistant rock. • At the Woodpile and Columbine Springs areas, bedrock encountered beneath the landslide deposits consists of interbedded siltstones, claystones, conglomerate, and sandstones of the Wasatch Formation. For the most part, the rocks encountered during the drilling were very weak (R1) to weak (R2) in strength. Rock strength data based on testing of samples recovered from the borings is presented in Table 2. Based on published geologic information, we believe the rocks underlying the McAndrews Lake area, described as interbedded layers of claystone, sandstone, conglomerate, and siltstone by Terracon (see Figure 5), are of the Mesa Verde Formation. Rock strength data for these borings are shown on Figure 5. • The results of surface reconnaissance mapping presented in Figures 2, 3, and 4 show the estimated boundaries of recent and historical landslide deposits within the three proposed HDD areas. The following are recommendations pertaining to final design and construction of the proposed pipeline through the Woodpile, Columbine Springs, and McAndrews Lake areas: • Areas delineated on the maps in Figures 2, 3, and 4 as containing recent or historic landslide deposits should be avoided for construction of HDDs. HDD entry and exit points should be located well outside of these limits. The HDD bores below these areas should be at a depth that is well below the landslide deposits and highly weathered bedrock, based on the depths indicated by the borings. • All construction activities, including trenching, right-of-way construction, slope cuts, and road/access construction should specifically avoid cutting into, or disturbance of, any area shown on Figures 2, 3, and 4 as "recent landslide movement ." These areas are considered to be highly susceptible to re -activation or acceleration of ongoing movements. Such re -activated or increased movements could impact construction of the proposed pipeline, and could also present a real and immediate hazard to the operating pipelines already existing in this corridor. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx Golder Associates March 2012 15 113-91752 • Cutting of slopes within areas delineated as "likely historic landslide movement" should be avoided as much as possible. If cuts, or other significant ground disturbance, are needed in these areas, we recommend that an experienced landslide geologist/engineer work with the project team to minimize the potential for re -activation of the landslide deposits. ■ If conventional trench construction is selected, rather than HDD, through any of the areas shown as "recently or historically active" on Figures 2, 3, and 4, we recommend that strain gage instrumentation be applied to the pipe, similar to what is currently in place for the "Red" and "Brown" lines at the Columbine Springs Landslide. Specific care will be needed during trenching and construction to minimize the risk of reactivating landslide movements. If this is to be done, we recommend that an experienced landslide geologist/engineer work with the project/construction team on site during construction through these areas. • Much of the area shown outside of the delineated "recently or historically active" landslide deposits shown on the maps is still within landslide deposits, albeit of older and likely (currently) more stable condition. However, significant cuts and fills should be avoided in these areas also, as reactivation of older landslide deposits may often lead to a long-term and ongoing maintenance problem. If significant ground disturbance is needed in these areas, we recommend that an experienced landslide geologist/engineer work with the project team to minimize the opportunities for re -activation of the landslide deposits. The conclusions and recommendations presented in this report are based upon data obtained from the boreholes at the indicated locations, field observations, laboratory testing, and our current understanding of the proposed pipeline project. It is possible that subsurface conditions vary between or beyond the investigated locations. The nature and extent of such variations may not become evident until construction. This report was prepared in accordance with the generally accepted standards of practice for geological and geotechnical engineering as exist in the site area at the time of our investigation. No other warranties, express or implied, are intended or made. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx 41417-4 Golder Iwo Associates March 2012 16 113-91752 7.0 CLOSING It has been a pleasure to assist on this interesting project. Please call or e-mail if you have any questions or if we can be of further assistance. GOLDER ASSOCIATES INC. Nancy Dessenberger Senior Consultant 41 • r •fri5888 *` (I) ...T.1‘ 3/1rn' 9p Graeme Major, PE Principal Geotechnical Engineer Document ID: 11322 Rhonda Knupp Senior Geologist s:\enterprise\201142011mlumbinespringslwep2\report-final4stamped final report 3-20124wep2 geotech dnvestigation.docx Golder Associates March 2012 17 113-91752 8.0 REFERENCES Colton, R.B., Holligan, J.A., Anderson, L.W., and Patterson, P.E., 1976. Preliminary Map of Landslide Deposits in Colorado: U.S. Geological Survey Miscellaneous Investigations Series Map 1-964. Golder, 2011. McAndrews Lake and Columbine Area, Summer 2011 Inclinometer Readings. Letter report to Enterprise Products, August 31, 2011. Golder, 2008. Report on the June 25, 2008 Geologic Hazards Field Reconnaissance of the Enterprise Pipeline Right -of -Way Between Baxter Pass and McAndrews Lake, Colorado. Letter report to Enterprise Products, August 8, 2008. Golder, 2007. Report of the November 6, 2007 Geologic Hazards Field Reconnaissance of the Enterprise Pipeline Right -of -Way between Baxter Pass and McAndrews Lake, Colorado. Johnson, R.C., 1985. Preliminary Geologic Map of the Baxter Pass Quadrangle, Garfield County, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF -1813. Stover, B.K., 1992. Surficial Geology and Geologic Hazards of the Douglas Pass -Baxter Pass Region, Rio Blanco and Garfield Counties, Colorado: Colorado Geological Survey Map Series 27. Stover, B.K., 1985. Surficial-Geologic and Slope Stability Study of the Douglas Pass Region: Colorado Geological Survey Open File Report 86-3. U.S. Geological Survey, 1964. Baxter Pass Quadrangle, Colorado — Garfield County, 71/2 Minute Series. s:\enterprise\2011\2011 columbinesprings\wept\report - final\stamped final report 3-2012\wep2 geotech investigation.docx 41417- Golder Associates FIGURES anza ttag n 0 tL 0 O ,1 Rio Blanco Meeker aufora j 13 J Q[Baxter Pass A[[ha Atchee CaiWriera Cartrunera HDD Project Location Ruby i 50 Colorado Q u aline Canyons Nat anal Westwatetl Conservation Area Fruita WPWI 7,559 Garfield c. he.i Castle Parachute Una De Beque Alan ",Appleton„ ,Palisade • Grand Junction Colorado M. Mesa VWh rtewater Kannah tJtlaweep Carryon Jn c o m p a I- roughton Molina Skyway Anvil Points Heiberger Collbran Grand Mesa !4atonal Forest and Mesa Grand Mesa Cedaredge Delta Orchard City Huff 17891 Read - Delta Keyhole Chtpeta 2 3 Hotchkiss Gunnison Gorge . National Crawford q r e C.onser,•ation Area Mack Olathe Morose `anyon, o: the Gunnison N. Montrose cedar creek Maher mer e• CartL Glenw.. Springs Cattle tie:• illi(lii dClL 4_ Gtnisori vt Wik C- 0 c Map backgrounds by ESRI / Bing Maps Golder Associates GARFIELD COUNTY, COLORADO Prepared by Rooney Engineering, Inc McAndrews Lake Horizontal Directional{Drill 711r - County County Hwy 201 Columbine Springs Horizontal Directional Drill Woodpile Horizontal Directional Drill SITE LOCATION DETAIL EEnterprise Products BAXTER PASS - HORIZONTAL DIRECTIONAL DRILLS WESTERN EXPANSION PROJECT PHASE II PROJECT LOCATION MAP SITE LOCATION MAP FIGURE 1 4101 1 • A.. c tir Ar ILIMEZ 4 F•. • qpi,trt-a--,, aLoo 41 A. • .. , 1f t. 4• r IF1 m aP I xi 7 a • ortv ire a IL r s." P _Afr - -17 f fro 101 At UPPER LIMIT OF SLIDE TERRAIN • 1 1>� • • 'Sr FLOWLINE OF CREEK • sitEs 0.s� i• • effil • • 4 • _. . 008• • • _.—.am. ono . moo _— .•1 1 P• i E_N fRY.-; 1 ST +i0 > p 1141111_A p 39°35.80767'N i ONG: 108°57.48665'W + 1 EV 7799' — p I ' STRAIN GAGE ARRAY 7 1 • CREEK BANK SLUMPING I • O O + O O TEST BOR. ELEV: 780' LAT: 39 LONG: 10:°5 414 e UPPER LIMIT OF SLIDE TERRAIN r N O = + M cr_ lit ._a 200' x 200' TEMPORARY WORKSPACE ' POIN EXIT ! 4r - STA. 13+00 AT: 39°35.59392'W ONG: 108°57.50344'W EV 7971' Ib' P II SURVEY CENTERLINE IF e * 10 • of 4 1 • O O r) 40 Mil at `i • It' • NOTES 1. STRAIN GAGE ARRAY SHOWN NEAR STATION 5+00 WAS RECOMMENDED IN PREVIOUS STUDY. THE STRAIN GAGE WAS NEVER INSTALLED. THERE ARE NO STRAIN GAGES AT WOODPILE LANDSLIDE AREA. REFERENCE 1. BASE MAP INFORMATION TRANSMITTED FROM ROONEY CONSTRUCTION TO GOLDER AUGUST, 2011. v41 Golder Associates LEGEND 4 i. 6 4. t TEST BORE WP -1 AREA OF RECENT (PAST 10 TO 25 YEARS) LANDSLIDE MOVEMENT, DASHED WHERE APPROXIMATE AREA OF LIKELY HISTORIC LANDSLIDE MOVEMENT (PAST 10 TO 100 YEARS) APPROXIMATE BOUNDARIES OF OLDER LANDSLIDE FEATURES APPROXIMATE BOUNDARIES OF LANDSLIDE FEATURES FROM SURFACE MAPPING PRIOR TO 2011 INITIALLY PLANNED, BUT NOT DRILLED 2011 TEST BORING LOCATION ACTUAL BORING LOCATION AIL -16 f44. • tip ilk tl 4 lor 1111' 100 0 100 1" = 100' Feet WOODPILE LANDSLIDE AREA FIGURE 2 Oct 19, 2011 14:27 MTMarks 1 Plotted: 12/14/11 9:41am MTMarks Drawing File: N:\11\113 -91752\_A BAXTER PASS\ 11391752A001.dwg 1 Layout: 18x24 COLUMBINE 1 Modifi 11P01, sailp.413140 Iik.af. * t • Ak. • ..Ikt 0,1 a L • • O. • ...• .. TEAS Bo -RE os- EL E CS- 4LAT . 396..32311' —LONG: 10 -57.600 ` O 0;i; k COLUMBINE ▪ v • e LANDSLIDE* CON1PLE?X TEST BO R 0 • at RE CS -2 1� ELEV 747' LAT: 39'36.22766'N LONG: 108°57 51816'W + 1 + -1- r • F .. c ^ 0 ` ` O �\ O otr \ N \ \ a gto -POINT OF ENTRY STA. 0+00 LAT: 39 36.33715'N ACCESS ROAD LONG: 108`57.61846'W ELEV 7426' 200 • i TE B�. GK'S Ey: 758 LAT 39 36 14233`N LONG: 10857-5 50'W •1114411r WV S'O • lir • 111, • 0 POIt QFNGIT ' 1°�� pr LBINE0 �41°, Z i r AQ• j. i at 4. 0' x 200' COMPLEXE� .` TEMPORARY RKSPnrE AP • .* •- /04 . t a ;.. • ABANDONED PIP .4 la Pi Miale ea ', 4r LEGEND IMMI TEST BORE CS -2 REFERENCE AREA OF RECENT (PAST 10 TO 25 YEARS) LANDSLIDE MOVEMENT, DASHED WHERE APPROXIMATE AREA OF LIKELY HISTORIC LANDSLIDE MOVEMENT (PAST 10 TO 100 YEARS) APPROXIMATE LIMITS OF COLUMBINE LANDSLIDE COMPLEX/OLDER LANDSLIDE FEATURES APPROXIMATE BOUNDARIES OF LANDSLIDE FEATURES FROM SURFACE MAPPING PRIOR TO 2011 INITIALLY PLANNED, BUT NOT DRILLED 2011 TEST BORING LOCATION ACTUAL BORING LOCATION 1. BASE MAP INFORMATION TRANSMITTED FROM ROONEY CONSTRUCTION TO GOLDER AUGUST, 2011. G,741Golder Associates 150 0 150 1" = 150' Feet COLUMBINE SPRINGS LANDSLIDE COMPLEX FIGURE 3 N:\11\113-91752\_A BAXTER PASS\ 11391752A001.dwg I Layout: 18x24 McANOREWS 1 Modified: Oct 19, 2011 14:27 MTMarks 1 Plotted: 12/14/11 9:43am MTMorks c. 0 0 sem: • gawk Of Ilk • • fa fli itf E - ► . i1 • rto.•, 'sem ••, • 44 Irot 41%0 flajtp 14 mo' a•i!�I •Y•• •,� 11* 116 b. .. L • •� r4' -• Lam•• ` • R • • • • • -- • • 1IN -51 Atoi, Y 201 '9 • • ABANDONED PIPELINE/WEP a II SURVEY CENTERLINE •• t• •.�„4;,+ k r •'�.. G Z_ • Y _ tIr % s - - i. . •• - t 46- fa,4 POINT OF ENTRY L,LEV: 6995.86' LAT; 39°36.95221'N LONG: 18°58.36918'W 1 1 TEST BOI E MC -1 ELEV: 7000.10 •••� : L T' 39°37.4 53'N" L�17108°58.58. 29'W 200' x 200' TEMPORARY WORKSPACE EDGE OF ROAD EDGE OF IRR DITCH STA. 25+70 - STA, 29+22q. EDGE_ OP_IRR DIT„ �s,; ,• STA. 29+38 4, FENCE CROSSINCa.�1�.�'�a STA. 29+72 '�10,c1f =kR• 8-4 GE OF WATER A.7+69 . p. 4 • • TEST_BORE MC -3 ELEV; 120.Q3" LAT: °36.98344'N LONG: 108°58.36389'W. 0 � $ i"g. ; . 1 1 1985 SLIDE AREA LAKE BOTTOM ELEV: 7094' PO IilI'. i*:1i, ELAVMS IMP. ..:...... LA IIIM licfr7CKIsO. teDitd:**DRI:WAyi . `►' t*':iN'4t-"TN6 OLDER SLIDE MARGIN d — fkt. •b. • • •`r • • . . 64-�r- R 1 • Y 111, w 4ik .— •♦ 4- • ,.s► - Nocv+0.4 • •t ' 4. • 4 o 0 .tro• .w• .'c, ,err .414 • NOTES 1►..• . �• • •i • • lilt J. 4 L -, w 1116• • •1L+- Is ;' �';�' i I �L� 4. . �t. , s • •14",''. '* J "moi ' s • s LAKE BOTTOM ELEV: 7092.2' LAKE BOTTOM ELEV: 7096.9' McANDREWS LAKE WATER ELEV: 7102.3' 11. •'- : • • 0 ELEV: 7096.5' • 4 ��Ztti.((..• �. y� !. ` M ! �r• z+ -' ./ a,'.s • tb • •• • 1, TEST BORES MC -1, MC -2, AND MC -3 WERE NOT DRILLED. LOCATIONS OF BORINGS B-1 THROUGH B-5 WERE SCALED OFF FROM APPROXIMATE LOCATIONS SHOWN ON HDD DESIGN SHEET PROVIDED TO MID AMERICA PIPELINE BY J.D. MAIR & ASSOC. INC., DATED 7/09/98 "PROPOSED DIRECTIONAL DRILL, 10" PIPELINE CROSSING MCANDREWS LAKE", DRAWING AND MUST BE CONSIDERED APPROXIMATE ONLY. REFERENCE 1. BASE MAP INFORMATION TRANSMITTED FROM ROONEY CONSTRUCTION TO GOLDER AUGUST, 2011. Golder Associates LEGEND ' i. • •ir w 7GM—NMI fill NMI M TEST BORE MC -2 B-3 AREA OF RECENT (PAST 10 TO 25 YEARS) LANDSLIDE MOVEMENT, DASHED WHERE APPROXIMATE AREA OF LIKELY HISTORIC LANDSLIDE MOVEMENT (PAST 10 TO 100 YEARS) APPROXIMATE BOUNDARIES OF LANDSLIDE FEATURES FROM SURFACE MAPPING PRIOR TO 2011 INITIALLY PLANNED, BUT NOT DRILLED 2011 TEST BORING LOCATION APPROXIMATE LOCATION 1998 (EST.) BORING BY TERRACON AC • • • • .• i ••• • 41 `. a • Lt. •, • • 4.•• .• sR •• • • • r • �p j► ' - ,� • •r • s I .c 1['�il t g. Y 4 i WAD - aa _. •.. , LAKE BOTTOM• • • w • .1# •_1 ••• • • • • ' L i• • • 200 • • • • • 0 1 • • 1 • 200 1" = 200' Feet McANDREWS LAKE AREA FIGURE 4