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Home My WebLink AboutGeological Hazards Report 04.07.2017H-F�XUMAR Geotechnical Engineering I Engineering Geology Materials Testing I Environmental 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs, and Summit County, Colorado GEOLOGIC HAZARDS REVIEW PROPOSED COMMERCIAL REDEVELOPMENT IRMW PROPERTY 1058 COUNTY ROAD 100 CARBONDALE,COLORADO PROJECT NO.17-7-230 APRIL 7, 2017 PREPARED FOR: MRI ATTN: DON VANDEVANDER 2074 COUNTY ROAD 109 GLENWOOD SPRINGS COLORADO 81601 mritraish@comcast.net TABLE OF CONTENTS PURPOSEAND SCOPE OF STUDY....................................................................................... - 1 - PROPOSEDDEVELOPMENT.................................................................................................. 1 - PROJECT SITE CONDITIONS.................................................................................................- 1 - REGONALGEOLOGIC SETTING..........................................................................................- 2 - CARBONDALE EVAPORITE COLLAPSE CENTER........................................................ - 3 - GEOLOGICALLY YOUNG FAULTS ................................................. - - ................................. PROJECT AREA GEOLOGY ........................................ EAGLE VALLEY EVAPORITE (Qc/Pee and Pee) ... SEDIMENTS OF SOPRIS BOWL (Qc/Tsb) .............. LANDFORMS AND SURFICIAL SOIL DEPOSITS Man -Disturbed Ground (af)..................................... Youngest River Terrace- (Qt 1)................................. Older Fans (Qf2)...................................................... Younger Fans (Qf 1)................................................. Colluvium (Qc)........................................................ ........................................................ 4 - ....................................................... - 4 - ....................................................... - 5 - ....................................................... - 5 - .......................................................- 6 - ........................................................ 6 - ........................................................ 7 - ....................................................... - 7 - ........................................................ 8- GEOLOGIC SITE ASSESSMENT............................................................. POTENTIAL HYPERCONCENTRATED FLOWS .............................. POTENTIALROCKFALL..................................................................... SINKHOLES........................................................................................... General Character of Evaporite Sinkholes .......................................... Potential Sinkhole Risk..... ................................................................... EARTHQUAKE CONSIDERATIONS.................................................. LIMITATIONS............................................................................. REFERENCES............................................................................. .............................. 8 - ............................. - 9 - ...........................- 10 - ........................... - 10 - ............................ 11 - ...........................- 11 - ........................... - 12 - ........................... 12 - ................................... 13 - FIGURE 1 — PROJECT SITE LOCATION FIGURE 2 — AERIAL PHOTOGRAPH AND TOPOGRAPHY FIGURE 3 — REGIONAL GEOLOGY MAP FIGURE 4 — WESTERN COLORADO EVAPORITE REGION FIGURE 5 — GEOLOGICALLY YOUNG FAULTS AND LARGER HISTORIC EARTHQUAKES FIGURE 6 — PROJECT AREA GEOLOGY MAP H-P—%KUMAR Project No. 17.7 PURPOSE AND SCOPE OF STUDY This report presents the results of a geologic hazards review for the proposed commercial redevelopment located at 1058 County Road 100, Garfield County, Colorado. The location of the project site is shown on Figure 1. The purpose of the study was to review the geology in the project area and assess if the geology could present constraints and potential hazards to the redevelopment. The study was conducted in accordance with our proposal for geotechnical engineering services to Don VanDevander dated March 13, 2017. A field reconnaissance of the property was performed on March 201h, 2017 to observe the site conditions and collect field information needed to evaluate and map the project area geology. In addition, we have reviewed published regional geologic information, looked at aerial photographs, and reviewed our previous nearby experience. Using this information, an assessment of potential geologic constraints and hazards to the proposed facility was performed. This report summarizes the information used in our evaluations, describes our assessments, and presents our findings. PROPOSED DEVELOPMENT The proposed redevelopment is conceptual and could include site grading and some cut into the hillside. Buildings will be of the commercial warehouse type. When building location(s), grading and loading information have been developed, we should be notified to 're-evaluate the recommendations presented in this report. PROJECT SITE CONDITIONS The project site covers about 60 acres in the middle and west of the 95 acre IRMW property, as shown on Figure 1. The project site is currently being used as a waste transfer and recycling center. The project site is on the south and west sides of the old Mid -Continent coal loadout site. H-P�WUMAR Project No. 17-7-230 -2- The topography of the project site and vicinity is shown by the contour lines on Figures 2 and 6. The project site lies at the base of a prominent, 540-foot high, west -trending escarpment. This escarpment forms the south Roaring Fork River valley side to the east of Carbondale. The escarpment has an average slope of about 70 percent and abruptly transitions to the nearly level river valley floor in the vicinity of the project site. A strongly rolling upland with slopes between 5 and 15 percent lies to the south of the escarpment. Before construction of the Mid - Continent coal loadout the transition slope between the very steep escarpment and the river valley floor consisted of small coalescing fans that formed a continuous depositional apron at the base of the escarpment. This apron had an average slope of about 25 percent down to the north toward the river valley floor. The original fan surfaces have been considerably modified by grading for the Mid -Continent coal loadout. The drainage basins upslope of the small coalescing fans are typically less than 2 acres but the largest is about 6 acres. The streams in these basins are ephemeral and only have surface flow following heavy rainfall or snowpack melt. Runoff from the escarpment is currently diverted around most of the project site in a shallow diversion ditch which in places is only about 1.5 feet deep. The fans that developed at the mouths of these ephemeral streams indicate that these small basins in the past have produced debris flows and floods (hyperconcentrated flows). At the time of this study, the property was primarily a waste transfer and recycling facility with some other industrial uses. A mini -storage facility is located on the adjacent property to the east. Ranches and rural development is present on the river terrace to the north. The rolling upland to the south of the escarpment is undeveloped range land. Vegetation on the escarpment consists of an open juniper and pinyon forest with sage brush and grass understory. Scrub oak is present along some of the ephemeral streams. REGONAL GEOLOGIC SETTING The regional geology in the project area is shown on Figure 3. The project site is located on a structural platform with complex geology that lies between the White River Uplift to the north, the Piceance Basin to the west, and the Sawatch Range Uplift to the east. These are first order geologic structures that developed during the Laramide orogeny about 40 to 72 million years ago. The project site is in the western Colorado evaporite region in the southern part of the Carbondale collapse center, see Figure 4. The Carbondale collapse center and the Eagle collapse H-PiWUMAR Project No. 17-7-230 -3- center to the east began to develop about 30 million years after the Laramide orogeny but the evaporate rocks (map unit Pze on Figure 3) in the western Colorado evaporate region were deposited much earlier than the Laramide orogeny. These evaporites were deposited in the northwest -trending central Colorado trough during the ancestral Rocky Mountain orogeny, about 280 to 320 million years ago. CARBONDALE EVAPORITE COLLAPSE CENTER The Carbondale evaporite collapse center is the western of two regional evaporite collapse centers present in western Colorado, see Figure 4. The Carbondale center covers about 460 square miles and as much as 4,000 feet of regional ground subsidence is believed to have occurred during the past 10 million years in the vicinity of Carbondale as a result of dissolution and flowage of evaporite from beneath the region (Kirkham and Others, 2002). Much of this subsidence appears to have occurred within the past 3 million years which also corresponds to high incision rates of the Roaring Fork and Crystal Rivers (Kunk and Others, 2002). It is uncertain if the regional subsidence is still an active geomorphic process or if evaporite subsidence has stopped. If still active, present deformations may be occurring at rates similar to past long-term rates of between 0.5 and 1.6 inches per 100 years. These slow deformation rates should not present a potential risk to the proposed redevelopment area. GEOLOGICALLY YOUNG FAULTS Geologically young faults related to evaporite tectonics are present in the Carbondale collapse center in the vicinity of the project site, but considering the nature of evaporite tectonics, these faults are not considered capable of generating large earthquakes. The closest geologically young faults that are less than 15,000 years old, not related to evaporite tectonics, and considered capable of producing large earthquakes, are located in the Rio Grande rift to the east of the project site, see Figure 5. The northern section of the Williams Fork Mountains fault zone Q50 is located about 61 miles to the northeast and the southern section of the Sawatch fault zone Q56b is located about 61 miles to the southeast. At these distances, large earthquakes at the maximum probable level of around M6.5 on the two closest geologically young fault zones H-P:KUMAR Project o. should not produce strong ground shaking at the project site that is greater than the ground shaking shown on the U. S. Geological Survey 2014 National Seismic Hazard Maps (Peterson and Others, 2014). PROJECT AREA GEOLOGY The main geologic features in the project area are shown on Figure 6. The project area geology map is based on our field observations, aerial photograph interpretations, and our previous work nearby. The map is a modification of the regional geology map by Kirkham and Widmann (1997). Geologic map units shown on Figure 6 are discussed below. EAGLE VALLEY EVAPORITE (Qc/Pee and Pee) Formation rock below the surficial soil deposits in the project area is the middle Pennsylvanian - age, Eagle Valley Evaporite (map units Qc/Pee and Pee). It was deposited in the northwest - trending central Colorado trough during the ancestral Rocky Mountain orogeny, about 280 to 320 million years ago. The Eagle Valley Evaporite is usually covered by a thin layer of colluvium (map unit Qc/Pee) but prominent outcrops (map unit Pee) are locally present on the escarpment. Outcrops that are potential source areas for rockfalls that have the potential to reach the project site are labeled OC-1 through OC-6 on Figure 6. The Eagle Valley Evaporite is a sequence of evaporitic rocks consisting of massive to laminated gypsum, anhydrite, and halite, with interbeds of light colored mudstone, fine-grained sandstone, shale, limestone, and dolomite (Kirkham and Widmann, 1997). The prominent outcrops that are potential rockfall source areas are cemented mudstone, limestone, sandstone, and gypsum. An oil exploration well near Catherine Store about 1.5 miles to the northeast of the project site shows that the Eagle Valley Evaporite is at least 2,700 feet thick at the well location (Kirkham and Widmann, 1997). The bedding in the Eagle Valley Evaporite is usually intensely folded and ductilely deformed by past flowage, load metamorphism, and anhydrite hydration. The evaporite minerals in the formation can locally be soluble in circulating groundwater, and shallow subsurface solution voids that can easily develop into surface sinkholes are locally present where the Eagle Valley Evaporite is near the surface in the western Colorado Evaporite Region, see Figure 4. Evidence of sinkholes was H-PZKUMAR Project No. 17-7-230 -5- not observed in the field or on the aerial photographs of the project area but sinkholes are locally present elsewhere in the Roaring Fork River valley between Basalt and Glenwood Springs. SEDIMENTS OF SOPRIS BOWL (Qc/Tsb) Sediments of Sopris Bowl below thin colluvium (map unit Qc/Tsb) are present near the top of the steep escarpment and upland to the south. These sediments may have a maximum preserved thickness of around 3,600 feet (based on seismic reflection data) and were deposited sometime after the eruption of a volcanic tuff dated to be 35.21±0.03 million years old (Kirkham and Others, 2002). A regional group of basalt flows that have been dated to be around 13.3 million years old occurs near the top of the sediments (Kirkham and Others, 2002). This indicates that most of the sediments in Sopris Bowl were deposited before the start of the regional subsidence of the Carbondale collapse center about 10 million years ago. The sediments are gravelly and cobbly, clast-supported fluvial deposits and matrix supported debris flow deposits. Clast lithologies indicate a Crystal River origin for the sediments in the western part of the bowl and a Roaring Fork River origin of the sediments in the eastern part of the bowl (Kirkham and Others, 2002). LANDFORMS AND SURFICIAL SOIL DEPOSITS The steep, 540-foot high escarpment and the surficial soil deposits and related landforms in the project area are largely related to glacial and interglacial climatic fluctuations during the Quaternary. The upland bench to the south of the steep escarpment is a relic landform that is older than the 620 thousand year old Lava Creek B volcanic ash (Kirkham and Widmann, 1997). The steep escarpment developed as a result of the Roaring Fork River downcutting below the upland surface that started several hundreds of thousands of years ago and has continued to the present. The fans at the base of the escarpment likely formed during and after the last glaciation in the Rocky Mountains. The youngest landscape features in the project area are man -disturbed ground. Surficial soils and related landform map units are discussed below. H-P�—WUMAR Project No. 17-7-230 Man -Disturbed Ground (af) Man -disturbed ground (map symbol af) is common in the project area and has modified the natural landscape. The disturbed ground is associated with grading for the old Mid -Continent . coal loadout facility, grading along County Road 100, and grading for the more recent on -site facilities and the mini -storage buildings adjacent to the project site to the east. As shown on Figure 6, the grading has considerably modified the younger fans (map unit Qf1). The only remnants of these fans are the fan heads in the central part of the project site and the distal parts of the fans to the north of the county road. Grading for the old Mid -Continent coal loadout consists of several nearly level cut and fill benches with interbench slopes typically at about 1.5:1 (horizontal to vertical). Interbench slope heights are typically between 10 and 30 feet. The highest interbench slope is located to the south of the existing main loadout building. This slope is about 50 feet high with an average slope of between 1:1 and 2:1 (horizontal to vertical). Interbench slopes that are flatter than about 1.5:1 (horizontal to vertical) have mostly performed satisfactorily but steeper interbench slopes have undergone considerable post -construction raveling. This raveling will continue unless the raveling slopes are flattened or stabilized by other means. Youngest River Terrace (Qtl) The Roaring Fork River valley floor to the north of the project site is the youngest fluvial terrace along the river (map unit Qt1). The surface of this terrace lies less than 12 feet above the modern river level (Kirkham and Widmann, 1997). Pedogenic soil profiles that developed at the surface of this terrace are typically A/Ck and A/Cg profiles (Natural Resources Conservation Service, 2008). The youngest river terrace probably developed during post -glacial time and the near surface fluvial deposits are likely between about 5,000 to 9,000 years old. The fluvial deposits below the youngest river terrace are very rocky loamy sands and very rocky sands using the Natural Resources Conservation Service (NRCS) soil textural classification system. The rocks are well rounded to subangular and range from gravel- to boulder -size (Kirkham and Widmann, 1997). The fluvial deposits are clast-supported and stratified. H-P�tKUMAR Project No. 17-1-Z -7- Older Fans (Qf2) In places, remnants of older fans (map unit Qf2) are present along the escarpment/river valley floor transition. Low, 10- to 20-foot high, escarpments separate the older fans from the surface of the youngest river terrace (map unit Qtl). This indicates that the older fans are older than the youngest river terrace. The fans probably developed during the late Pleistocene -age, Pinedale glaciation and the fans are likely greater than about 9,600 years old. Pedogenic soil profiles developed at the surface of older fans are A/BwBk profiles (Natural Resources Conservation Service, 2008). Our previous experience in the area to the east of the project site shows that the older fan deposits are rocky silt loams using the NRCS soil textural classification. The rocks are well rounded to angular and range from gravel- to boulder -size. The rounded rocks come from the sediments of the Sopris Bowl (map unit Qc/Tsb) that are present near the steep escarpment. The rocks are supported by the silt loam soil matrix. The older fans are largely the product of sediments deposited by infrequent debris flows and debris floods (hyperconcentrated flows). The older fans are no longer the sites of hyperconcentrated flow deposition. Younger Fans (Qfl) Over twenty, small coalescing fans (map unit Qf1) that once formed a continuous deposition apron along the escarpment/river valley floor transition slope are present in the project area. The drainage basins tributary to the younger fans are very steep and small. The basin slopes are greater than 30 percent and the basin areas are typically less than 2 acres but the largest is 6 acres. The younger fans grade smoothly to the youngest river terrace surface (map unit Qtl). Our previous experience with the development to the east of the project site shows that in the subsurface, the younger fans overlie the youngest river terrace deposits. These two geologic relationships indicate that the younger fans are younger than the youngest river terrace deposits. The younger fans likely formed during the past 5,000 years following the post -glacial climatic optimum about 5,000 to 7,000 years ago. They may be associated with the three neoglacial cycles that occurred in the Colorado Rocky Mountains during the past 5,000 years (Benedict, H-P—%KUMAR Project No. t 7-7-2's 1973). Like the older fans, the younger fans are also largely the product of sediments deposited by infrequent debris flows and debris floods (hyperconcentrated flows). The younger fans appear to still be active geomorphic features and areas within the project site to the north of the younger fan heads should be considered potential sites for future hyperconcentrated flow deposition. The statistical recurrence probabilities and risks associated with hyperconcentrated flows on the younger fans are discussed in the Geologic Site Assessment/Potential Hyperconcentrated Flows section of this report. Cut slope exposures and our previous experience in the area to the east of the project site shows that the younger fan deposits are similar to the older fan deposits. The younger fan deposits are rocky silt loams using the NRCS soil textural classification. The rocks are well rounded to angular and range from gravel- to boulder -size. The rounded rocks come from the sediments of Sopris Bowl (map unit Tsb) that are present near the top of the steep escarpment. The rocks are supported by the silt loam matrix. Colluvium (Qc) Thin colluvium (map unit Qc) covers the Eagle Valley Evaporite (map unit Pee) and the sediments of Sopris Bowl (map unit Tsb) on the steep escarpment and upland to the south of the project site. The colluvium appears to be similar to the younger and older fan deposits and is probably also a rocky silt loam using the NRCS soil textural classification. The rocks should be well rounded to angular and range from gravel- to boulder -size. The rounded rocks come from the sediments of Sopris Bowl (map unit Tsb) that are present near the top of the steep escarpment. The rocks are probably supported by the silt loam matrix. GEOLOGIC SITE ASSESSMENT This study shows that geologic conditions that could present an unusually high risk to the proposed redevelopment are not present at the locations of the proposed project components. Although the potential risks are not unusually high, the proposed facilities are exposed to some H-P%KUMAR Project No. 17-7-230 geologic risks including hyperconcentrated flows, rockfalls, sinkholes, and earthquake related strong ground shaking. These geologic conditions, an assessment of their potential risks, and the need for risk mitigation are discussed below. POTENTIAL HYPERCONCENTRATED FLOWS The younger fans (map unit Qf1) appear to still be active geomorphic features and areas within the project site to the north of the younger fan heads should be considered potential sites of future debris flow and flood (hyperconcentrated flow) deposition triggered by extreme thunderstorms over the drainage basins. Historic thunderstorm triggered hyperconcentrated flows have occurred on similar fans in the lower Roaring Fork River valley but historic flows have probably not occurred at the project site. Without long term observation or detailed fan specific stratigraphic studies it is not possible to evaluate the statistical recurrence probability of major hyperconcentrated flows at the project site with a high level of confidence. In our opinion, the statistical recurrence probability of major hyperconcentrated flows at the project site is likely long and may be around 100 years and possibly longer. A major hyperconcentrated flow event has the potential to damage structures in the project site and deposition of mud and debris should be expected in the project site. The larger basins on either side of the Eagle Valley Evaporite outcrop OC-1 appear capable of producing relatively large debris flows or floods (hyperconcentrated flows). If these risks are not acceptable to the owner or governmental regulatory agencies, then additional studies should be performed to further evaluate hyperconcentrated flow risk and mitigation. Risk mitigation would likely be direct protection of the structures by wall reinforcement or the construction of diversion channels down through the development. The existing bench and berm located below Eagle Valley Evaporite outcrops OC- 5 and OC-6 does not appear to be adequate mitigation for major hyperconcentrated flows. Hyperconcentrated flow diversion channels are most effective when constructed at low angles to hyperconcentrated flow direction. A more effective diversion channel would divert the hyperconcentrated flow to the north, past the proposed redevelopment. Considering the probable low risk, the cost of mitigation to achieve a low risk could be greater than the cost of building repair and the cleanup of mud and debris if a major hyperconcentrated flow event occurred during the service life of the facility. H-PEKUMAR Project No. 17-7-230 -10- POTENTIAL ROCKFALL Prominent outcrops of the Eagle Valley Evaporite (map unit Pee) are present on the escarpment to the south of the project site and some of these outcrops are potential source areas for future rockfalls that could reach the project site. These potential rockfall source zones are labeled OC-1 through OC-6 on Figure 6. Rockfall blocks were observed in the field down slope of OC-1, OC- 2, OC-3, OC-5 and OC-6. Some larger rockfall blocks could have been removed during grading for the old Mid -Continent coal loadout facilities and the existing waste transfer facility. The largest rockfall blocks observed in the field had dimensions of about 3 feet, by 1.5 feet, by I foot, and an estimated weight of around 675 pounds, but larger blocks were found during previous studies in the area. Multiple rockfall blocks stopped in the diversion ditch which indicates that rockfall has occurred since the coal loadout was constructed. Without long term observation in is not possible to evaluate the statistical recurrence probability of rockfalls at the project site. It is possible that future rockfalls could reach the proposed structures and project site. Future rockfalls have the potential to damage structures on the project site. There is also some risk of harm to on -site personnel but this risk should be low and likely not greater than the risk to the travelling public on Colorado highways in low risk rockfall areas. If these risks are not acceptable to the owner and governmental regulatory agencies, then additional studies should be performed to further evaluate rockfall risk and mitigation. Risk mitigation would likely be a rockfall catching or attenuating fence located upslope of the facilities requiring protection. At the time of the site visit it was observed that the existing ditch was relatively full of soil and rocks. Removal of some of the soil and rocks (deepening of the ditch) would increase the effectiveness of the ditch at stopping small rockfall events. There is an existing berm on the south side of the road below OC-1. The road creates a landing area for rockfalls and the combination of this and the berm will likely stop most small rocks falling from OC-1. Increasing the height of this berm would make it more effective. SINKHOLES The evaporite mineral in the Eagle Valley Evaporite can be locally soluble in circulating groundwater and solution of these minerals can result in local subsurface voids which can H-P IWUMAR Project o. - -11- sometimes develop into surface sinkholes. Shallow subsurface solution voids and sinkholes are locally present in areas where the Evaporite lies at a shallow depth throughout the western Colorado evaporite region, see Figure 4. The general character of evaporite sinkholes and the potential risk that sinkholes pose to the proposed site are discussed below. General Character of Evaporite Sinkholes Evaporite sinkholes in western Colorado are typically 10- to 50-foot diameter, circular depressions at the ground surface. The sinkholes mostly result from upward caving of a soil rubble pipe to the ground surface. The soil rubble pipe is formed by piping and subsurface erosion of surficial soils into subsurface solution voids in the underlying evaporite. Direct caving of very large solution caves have also occurred in the region. New sinkholes can develop at the ground surface with little or no advanced warnings and existing sinkholes can be reactivated. New sinkholes and reactivated sinkholes have the potential for severe damage to buildings and other man-made facilities. Historic sinkholes have developed in the western Colorado evaporite region but have rarely damaged structures. This indicates that sinkhole development is still an active geomorphic process in the region but does not statistically present an unusually high risk to structures in the region as a whole. Potential Sinkhole Risk Evidence of sinkholes was not observed in the field or on the aerial photographs of the project site. In our opinion, the risk that a sinkhole will develop at the proposed redevelopment site is low during a reasonable exposure time. The sinkhole risk at the project site does not appear greater than the existing risk elsewhere in the Roaring Fork River valley or in the western Colorado evaporite region with shallow evaporite, as shown on Figure 4. The low risk in the region is inferred from the large extent of the sinkhole prone areas in comparison to the small number of new sinkholes that have developed during historic times in the region. The project site owner should be made aware of the low sinkhole risk and that the proposed facilities cannot be considered totally risk free. If evidence of a developing sinkhole is noted, it may be possible H-P%KUMAR Project No. 1 - -12- to limit potential facility damage with ground improvement techniques such as structural backfill and compaction grouting. EARTHQUAKE CONSIDERATIONS Historic earthquakes within 150 miles of the project site have typically been moderately strong with magnitudes of M5.5 and less and Modified Mercalli Intensities of VI and less, see Figure 5. The largest historic earthquake in the project region occurred in 1882 (Kirkham and Rogers, 1985). This earthquake was apparently located in the northern Front Range about 117 miles to the northeast of the project site and had an estimated magnitude of M6.2 ± 0.3 and a maximum intensity of VII. Historic ground shaking at the project site associated with the 1882 and the other larger historic earthquakes in the region does not appear to have exceeded Modified Mercalli Intensity VI (Kirkham and Rogers, 1985). Modified Mercalli Intensity VI ground shaking should be expected during a reasonable exposure time for the proposed project facilities, but the probability of stronger shaking is low. Intensity VI ground shaking is felt by most people and causes general alarm, but results in negligible damage to structures of good design and construction. The U. S. Geological 2014 National Seismic Hazard Maps indicate a peak ground acceleration of 0.08g has a 10% exceedance probability for a 50-year exposure time and a peak ground acceleration of 0.3g has a 2% exceedance probability for a 50-year exposure time at the project site (Peterson and Others, 2014). This corresponds to a statistical recurrence time of about 500 years and 2,500 years, respectively. These accelerations are for firm rock sites with shear wave velocities of 2,500 fps and higher in the upper 100 feet and should be modified for soil profile amplification at the project site. The seismic soil profile at the project site should be considered as Class D, stiff soil sites as described in the 2015 International Building Code unless site specific shear wave velocity studies show otherwise. LIMITATIONS This study was conducted according to generally accepted engineering geology principles and practices in this area at this time. We make no warranty either express or implied. The H-P-KUMAR Project No. 17-7-230 -13- conclusions and recommendations submitted in this report are based on our field observations, aerial photograph interpretations, published regional geology information, the currently proposed development plan, and our experience in the area. This report has been prepared exclusively for our client and is an evaluation of the geologic constraints and their potential influence on the proposed development. Additional evaluations will be needed if hyperconcentrated flow and rockfall mitigations are considered. We are not responsible for technical interpretations by others of our information. If you have any questions or need further assistance, please call our office. Sincerely, H-P= KUMAR Robert L. Duran, E.I. Reviewed by - Steven L. Pawlak, P.E. RLD/ksw REFERENCES Benedict, J. B., 1973, Chronology of Cirque Glaciation, Colorado Front Range: Quaternary Research, v. 3, p. 584-599. Kirkham, R. M., and Others, 2002, Evaporite Tectonism in the Lower Roaring Fork River Valley, West -Central Colorado, in Kirkham R. M., Scott, R. B., and Judkins, T. W. eds., Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado: Geological Society of America Special Paper 336, Boulder, Colorado. H-P:—WUMAR Project No. 17-7-230 - 14- Kirkham, R. M., and Rogers, W. P., 1985, Colorado Earthquake Data and Interpretations 1867 to 1985: Colorado Geological Survey Bulletin 46. Kirkham, R. M., and Scott, R. B., 2002, Introduction to Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado, in Kirkham R. M., Scott, R. B., and Judkins, T. W. eds., Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado: Geological Society of America Special Paper 336, Boulder, Colorado. Kirkham, R. M., and Widmann, B. L., 1997, Geology Map of the Carbondale Quadrangle, Garfield County, Colorado: Colorado Geological Survey Open File 97-3. Kunk, M., J., and Others, 2002, 40Ar/39Ar Ages of Late Cenozoic Volcanic Rocks within and Around the Carbondale and Eagle Collapse Centers, Colorado: Constraints on the Timing of Evaporite-Related Collapse and Incision of the Colorado River, in Kirkham R. M., Scott, R. B., and Judkins, T. W. eds., Late Cenozoic Evaporite Tectonism and Volcanism in West -Central Colorado: Geological Society of America Special Paper 336, Boulder, Colorado. Natural Resources Conservation Service, 2008, Soil Survey of Aspen -Gypsum Area, Colorado: Version 5, June 9, 2008. Peterson, M. D. and Others, 2014, Documentation for the 2014 Update of the National Seismic Hazard Maps: U. S. Geological Survey Open -File Report 2014-1091. Tweto, O. and Others, 1978, Geology Map of the Leadville 1 ° X 20 Quadrangle, Northwestern Colorado: U. S. Geological Survey Map I-999. Widmann B. L. and Others, 1998, Preliminary Quaternary Fault and Fold Map and Data Base of Colorado: Colorado Geological Survey Open -File Report 98-8. H-PE K MAR Project No. 17-7-230 r4 NX T- i 44 / o i, __`._ A: r-T -r --1 Ar it,' OD A X PZ White Jr P7 I-V Y& River V ':'Xr P I-V I i V um upli T P7 P7�e Nt% -�Ar Rze F, A Tr PZ MOU(Itain PZe Piceance 'ry Ts C) P7 P" rr T% TK,,; 7i TV roz CD Projects rwl�Site MZ 0 Ts CaSUP P. 0 cl. MZ M, Basin �t �, T P P7 TK- FA cl\-h Explanation: Lis Post-Laramide Sediments Pro-Lararnide Mesozoic Sediments High -Angie FauKs o st- L.;q m 2t i d e_ V ol c a ni cs Paleozoic Sediments P^ ^ Thrust Faults Post-Laranlide Intrusivas Pennsylvanian EvaV2�rites Synclines 0 Ili L A =TK c Laramide Basin Sediments Pracambrian_CrystalIne Rocks 4 AniiclimDs I Scale I in. 7 mi La. -amide Intruzives Contact Highways F.-birsj a.,y 201 -) Mc6f;ed tcirj-n-;. Cvveto 1,197Y) IRMW Property Geologic Hazards Review, County Rd. 100 - Regional Figure 3 17-7-230 1 H-P E-:Z: KUMAR I Geology Map I I !Z E N So- Aatch RangF Anilclin= WUU-- Y W ids a d � Qom.-: i �u f0 do c _ _ cI L C ti � C N U UJ L w L y L H-P ` KU MAR IRMW Property Geologic Hazards Review, County Rd. 100 - Western g 17-7-230 Figure 4 Colorado Evaporate Region VI 150 mils U � -y,,� B SIi1 l l� a -I V'vy NB. idrfie Walden k1 j J f Axial Basin Liy Parl• A1891 1871 7 +:+ FoA Cdllns Great • 1977 VI VI �1 craft �'' / SlEamhoat Sp'Inga • Love43nd r Greeley M 5 C ��////// 0 N Front y_ 1E62 n Fort PLI Rockyrd'n Arsenal VII VI to VII _ (D BaAdpr hd 3.2 to %1 $._ Imt-ismlc l3P1Q="n" Vail ,\ Sell Seismic t3el! -. 5"0ducsd G Project -Ezalr- F scc Dzcv= O 'raW°i Rr9e l �� 3rdl::nn �, Site / G I-- Kicv.•a L lC%rl(:r.1tn� 1dLj3 �rspen fir. C351a r d 9 J S CrauJ , t �� ... ISQ 7 rHC�Cnck Grans ! .nv Coloreds Sp C'I�II"I -2 tiff til.onlr�s�._ r,175 Sala l f �' Poetl•; r I-0drier. ny 1913 T VI Lake Cil 1900 — It` Nlalserb:�r7 I iT Duamg. D[.I:;e - i •tJ. NI 1 Tiri'3d I VII r ' CI .arse l Explanation: Post -Glacial Faults: Historic Seismic Zones: Fail? younger than about i5,000 }e:re ?reas wiih hislUnrally hiy( selami, o-7 i• i;7 Larger Historic Earthquakas: la Local surace Nava or body wave iragnitude Farthyuak=_s with ma.inum inlrnshy gr�f,ler c :in. VI VI P Icdi°i=d Prlercelli int.rislty Ur miCrilud, grsaler thar NI 5-0 from 1867 to prasen:, p 5i.Inl Nuclear Explosion: L I i ar.,e urrlergrau[•d �t.Cl_.-:r exrlCSi�a� fa n�tu �.I r}�� P.eferEncss: Scale: I in. _ �G n1i -=sEr,ur ernan Tment `P/idrnann arc Olhsrs (1598) f ebruarr'�91'� U. S. Geological Su-is;d Earthquake Catalogs - H-P ` KU MAR 1RMW Property Geologic Hazards Review, County Rd. 100 - 17-7-230 � Figure 5 Geologically Young Faults and Larger Historic Earthquakes s k� L 4= O a) f0 0 Ncc ..� C � m u 2N E E C ` cc O U C E _Cn U m Y E CD 0 Is U w a m a C > L L W c0 L U O a d W rn > v a m o > > moo ccm E �o m W !a U — a f0 c > W O N Y a 70 O ev O 2 N E d m ° c 7_ E dW c Oat CL UQ Wo�aV d i i em- 0 ( 1 . �7, 1 E C! �, ;O { o a• ;� t I � a� m ' {1 1 ��. _ J12, Y t 66 > ,11111 ` \ qb c > 7 U LL C U, 10 LL Gyl 2I0 o >- 01 � o : 11 � i_j W �W - 17-7-230 H—P KU MAR IRMW Property Geologic Hazards Review Figure 6 Project Area Geology Map