CO 9 & US 6 Improvement Project at I-70 Silverthorne/Dillon Interchange PEL Study

STATE HIGHWAY 9 / U.S. HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE PLANNING AND ENVIRONMENTAL LINKAGES STUDY

July 9, 2012

Prepared for: Colorado Department of Transportation Region 1 Prepared by: AECOM 717 17 Street, Suite 2600 Denver, CO 80202 TH

STATE HIGHWAY 9 AND U.S HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE PLANNING AND ENVIRONMENTAL LINKAGES (PEL) STUDY

TABLE OF CONTENTS

SECTION

PAGE

EXECUTIVE SUMMARY

1

I

3

INTRODUCTION

Project Overview Purpose and Need Screening of Alternatives Proposed Action II

ENVIRONMENTAL CONSEQUENCES, MITIGATION COMMITMENTS AND MITIGATION MEASURES OF THE PROPOSED ACTION

3 6 7 9

16

Summary of Consequences, and Anticipated Mitigation

16

III NEPA PROCESS RECOMMENDATION

22

Overview Non Programmatic Categorical Exclusion: Applicability and Requirements Non Programmatic Categorical Exclusion: Tasks to Complete the Process

22 22 22

IV

23

NEXT STEPS

APPENDIX A. B. C. D. E. F. G.

PEL Questionnaire Purpose and Need Launch Phase Technical Report Feasibility-Level and Concept Level Screening Analysis Detailed-Level Screening Analysis Public Involvement Report Environmental Resource Analysis

STATE HIGHWAY 9 AND U.S HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

LIST OF FIGURES

FIGURES

PAGE

1 2 3 4 5 6

3 4 5 10 12 14

Project Study Area Detailed Map of the Interchange Area Six CSS Process Steps and the Three Project Phases: Launch, Evaluate and Deliver Diverging Diamond Design Westbound On Ramp Design SH 9/Wildernest Intersection Design (Ultimate)

LIST OF TABLES

TABLES

PAGE

1 2035 Level of Service (LOS) with the Proposed Improvements 2 Summary of Environmental Consequences and Anticipated Mitigation Measures

9 16

STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

EXECUTIVE SUMMARY The Colorado Department of Transportation (CDOT) began a feasibility study process for the State Highway 9 (SH 9) and U.S. Highway 6 (US 6) Improvement Project at the Interstate 70 (I-70) Silverthorne/Dillon Interchange in early 2010. The completion of this process in the form of this Planning and Environmental Linkages (PEL) Study follows completion of the I-70 Mountain Corridor Final Programmatic (Tier 1) Environmental Impact Statement (PEIS) and Record of Decision (ROD).

This PEL Study is a planning document designed to focus the project, to anticipate and avoid future NEPA problems, and to reduce the level of NEPA documentation needed: Environmental Impact Statement (EIS) vs. Environmental Assessment (EA) vs. Categorical Exclusion (CatEx or CE).

The PEL Study includes an overall description of the feasibility study process and results and summarizes and incorporates by reference the following key project documents (PEL Study Appendixes A-G): A.

PEL Questionnaire: The Federal Highway Administration/CDOT PEL Questionnaire summarizes basic information and methods that were applied in the PEL process.

B.

Purpose and Need: The Purpose and Need describes the project’s basic purpose and problems statements or needs that should be addressed by the emerging solutions or proposed improvements.

C.

Launch Phase Technical Report: This report provides baseline information from the I-70 Mountain Corridor PEIS and others sources to describe the affected environmental of the project’s study area.

D.

Feasibility-Level and Concept Level Screening Analysis: This pair of screening analyses use evaluation criteria to identify fatal flaws and other important considerations for a wide range of improvement alternatives and options, compares the outcomes and determines which alternatives and options should be eliminated from further consideration or advanced for further consideration.

E.

Detailed-Level Screening Analysis: This screening analysis uses specific qualitative and quantitative criteria to evaluate and compare potential effects of the alternatives and options, defines the alternatives and options that should be eliminated from further consideration and recommends a refined list of proposed improvements for further consideration.

F.

Public Involvement Report: The public involvement report fully defines the project team’s effort to generate participation and input from public agencies, stakeholders and the public through the project process, and describes and includes various approaches, documents and tools that were used.

G.

Environmental Resource Analysis: Effects and Mitigation Measures: This analysis evaluates the overall effects of the proposed improvements defined by the Detailed-Level screening Analysis in term of their environmental consequences, and identifies environmental mitigation commitments and other recommended mitigation measures.

1

STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

Based on the evaluation and observations made in the PEL analysis, the following improvements were recommended: Diverging Diamond Intersection, Alternative C Westbound On Ramp -Improved Grade, Options A and C* SH 9/Wildernest Intersection, Options A and C* A continuous eastbound auxiliary lane from the Frisco Interchange to the Silverthorne/Dillon Interchange is also evaluated, but at a lesser level of detail than the interchange area alternatives and options. The auxiliary lane is a stand-alone project that could be phased. The auxiliary lane requires further study. *The Westbound On Ramp Option A (improved grade) and Option C (improved grade and two-lane on ramp over the Blue River) are related in that Option A provides a phased implementation that allows early action that can later be expanded to include Option C buildout. This offers flexibility to implementation depending on the construction funding available. At the SH 9/Wildernest intersection, Option A is the ultimate buildout design and Option C (interim) is the phased implementation that allows early action that can later be expanded to include Option C buildout.

Based on the characteristics of the proposed improvements, their potential environmental consequences, and applicable procedural requirements, no significant effects are anticipated.

Funding for project construction has not been secured so the next step in the process is to secure some or all of the funding needed for project construction. Once funding is available, the funded portions of the project would be subject to the NEPA Process and a final decision over the type of NEPA documentation to prepare would be made. The outcome of the NEPA process would lead to a final decision about the proposed action. At this time, the NEPA action that is recommended is a Documented Categorical Exclusion (CatEx).

2

STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

I

INTRODUCTION

Project Overview The Colorado Department of Transportation (CDOT) began a feasibility study process for the State Highway 9 (SH 9) and U.S. Highway 6 (US 6) Improvement Project at the Interstate 70 (I-70) Silverthorne/Dillon Interchange in early 2010. The completion of this process in the form of this Planning and Environmental Linkages (PEL) Study follows completion of the I-70 Mountain Corridor Final Programmatic (Tier 1) Environmental Impact Statement (PEIS) and Record of Decision (ROD). The PEIS and ROD provide extensive background information for the PEL Study and a framework for the analyses through the Context Sensitive Solutions (CSS) program developed for I-70. This PEL Study is a planning document designed to focus the project, to anticipate and avoid future NEPA problems, and to reduce the level of NEPA documentation needed: Environmental Impact Statement (EIS) vs. Environmental Assessment (EA) vs. Categorical Exclusion (CatEx or CE). The PEL Study is valid for as long a time period as the baseline conditions and project assumptions remain valid.

The project Study Area is presented in Figure 1. Figure 2 presents a detailed map of SH 9, US 6, the interchange and the local street network.

Figure 1

Project Study Area

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

Figure 2

Detailed Map of the Interchange Area

Note: References to north, east, south and west within the study area differ from actual compass directions. The direction references are applied to conform to the general understanding that I-70 passes through Colorado in an east/west manner with westbound and eastbound traffic and that State Highway 9 and US 6 generally pass through the area in a north/south manner.

AECOM, a consulting firm, was hired to assist CDOT with the study. The project team, composed of CDOT and AECOM staff members, has gathered information, developed a project purpose and need, developed preliminary improvement alternatives and options, performed feasibility-level, concept-level and detailed-level alternative and option screening analyses. This Planning and Environmental Linkages (PEL) Study describes the overall project feasibility study processes and outcomes. Appendix A presents the project’s PEL Questionnaire. Appendix B presents the project’s Purpose and Need. The project decision making was performed with the support of a Project Leadership Team (PLT).

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

The members of the PLT included: Dan Burroughs, Town of Dillon Town Engineer Bill Linfield, Silverthorne Public Works Director Thad Noll, Summit County Assistant County Manager Steve Swanson, Blue River Watershed Group Melinda Urban, FHWA, Operations Engineer and Civil Rights Program Manager Grant Anderson, P.E., CDOT Region 1 Resident Engineer Peter Kozinski, P.E., CDOT Region 1 Program Engineer Tyler Weldon, P.E., CDOT Region 1 Project Manager Chuck Attardo, CDOT Region 1, Environmental Manager R.A. Plummer, P.E, AICP, AECOM Alan Eckman, P.E., PTOE, AECOM Tom Schilling, Intermountain Corporate Affairs

A wide range of interchange alternatives and improvement options were developed and screened. The screening process was based on the I-70 Mountain Corridor CSS Process, which is the starting point for all new projects on the I-70 Mountain Corridor. These steps are intended to provide a clear and repeatable process that is fair and understandable. The order of the steps is as important as the activities within each step. The six CSS steps were implemented in three phases (See Figure 3).

Figure 3

Six CSS Process Steps and the Three Project Phases: Launch, Evaluate and Deliver

Project Evolution – CSS Process Project Development

Engineering Design

Construction

Project Development Phases Launch 9/10 – 2/11 Establish and charter PLT; endorse project approach; define project objectives, rationale, and goals; develop criteria for evaluating alternatives CSS Steps Accomplished 1. Define desired outcomes and actions 2. Endorse the process 3. Establish criteria

Deliver 3/12 – TBD

Evaluate 3/11 – 3/12 Brainstorm solutions, form Issue Task Forces as necessary, evaluate and refine alternatives using established criteria, select alternative(s), determine NEPA requirements

Complete documentation of the recommendation and decision-making process, finalize conceptual design, prepare NEPA document, evaluate process, identify lessons learned

CSS Steps Accomplished 4. Develop alternatives 5. Evaluate, select, and refine alternatives or option

CSS Steps Accomplished 6. Finalize documentation and evaluate process

We are here

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

The Launch Phase Technical Memorandum (Appendix C) summarized the work elements completed as part of the first phase of the project. The Launch Phase included: Defining project rationale Defining the study area Defining project , goals, and evaluation criteria Establishing the project process and conducting initial outreach activities Establishing the existing and future no-build conditions to use as a baseline in analysis Defining next steps for alternative development and evaluation The Evaluate Phase was documented in two reports: 1. Feasibility-Level and Concept-Level Screening Analysis (See Appendix D) 2. Detailed-Level Screening Analysis (See Appendix E) The Public Involvement Process Report (See Appendix F) provides an overview of the public involvement process and activities and presents documentation for the primary outreach efforts that were used to support the Purpose and Need, develop and screen alternatives and options through the feasibility and conceptual-level process. These efforts included the involvement of the Project Leadership Team (PLT), public meetings, small group meetings, and project communications directing participants to the project’s website and opportunities to participate. The small group meetings involved public agencies, business community representatives and other stakeholders, and elected officials. Meeting summaries were prepared to clarify key issues addressed at these meetings and the input obtained from the participants.

Purpose and Need The project’s purpose and need is presented in Appendix B. The following presents the key needs of the project: SAFETY High crash risks exist along SH 9 and US 6, particularly at and near intersections.

Backups onto I-70, particularly from the eastbound off ramp, substantially increase I-70 safety risks and accident rates.

High speeds and speed differences involving merging interchange ramp traffic and through traffic on I-70 create safety issues and accidents, particularly in association with the eastbound off ramp and westbound on ramp.

Cycling on local sidewalks along SH 9 and US 6 and evidence of shortcuts across I-70 ramps and lanes creates safety issues despite the presence of the Blue River Trail.

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

CAPACITY The number and density of signalized and unsignalized local access points and turning movements within close proximity to the I-70 interchange ramps serves existing commercial development, but causes much of the congestion along SH 9 and US 6 as well as difficulty accessing I-70.

Skewed intersections, split phase signals and necessary green time for pedestrian movements, particularly at the SH 9/Wildernest intersection, limit through and left turn movement green times, resulting in reduced traffic capacity along SH 9 and US 6.

Motorists using the westbound off ramp who plan to turn left onto Wilderness at the SH 9/Wildernest intersection are required to weave across two SH 9 through lanes in a short distance.

The southbound left turn movement from SH 9 to eastbound I-70 has inadequate capacity/ storage.

Motorists using the eastbound off ramp turning right onto US 6 are required to negotiate southbound weaving vehicle movements on US 6 associated with the close proximity of the nearest interchange and intersection immediately to the south.

Motorists using the westbound on ramp must weave into one lane over a short distance before merging with I-70 westbound traffic. This weave and merge is complicated by a steep grade.

MULTIMODAL CONNECTIVITY Existing local bus service and future transit service are important and should not be limited or precluded by future improvement plans.

Direct access for pedestrians and cyclists under I-70 is limited because some sidewalks and crosswalk transitions are in poor condition and/or are difficult to use in the winter.

Screening of Alternatives The Feasibility -Level and Concept-Level screening process was performed by project team members and representatives from the Town of Silverthorne, the Town of Dillon, Summit County and stakeholder groups at a workshop on April 21, 2011. The project team compiled the workshop input and refined the analysis. Four interchange alternatives were analyzed: 1.

2.

3.

4.

Improved Diamond Roundabout Single Point Urban Interchange (SPUI) Diverging Diamond (DDI)

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

Eight optional improvements were also analyzed for three interchange improvement types: 1. Eastbound Off Ramp: Options A, B and C 2. Westbound Off Ramp: Options A, B and C 3. Straight Creek: Options A and B The roundabout interchange design, involving four roundabouts was eliminated from further consideration, but roundabouts at the local street intersections next to the ramp intersections were advanced for further consideration. In addition, fatal flaws were found with four of the options: Eastbound Off Ramp Option C Westbound On Ramp Option C Straight Creek Flyover Option Straight Creek Underpass Option The outcome of the Detailed-Level screening analysis provided a clear and distinct advantage for one interchange alternative (Diverging Diamond) relative to the other two, and justification for specific complimentary improvement options to be implemented in concert with the Diverging Diamond design.

Based on the evaluation and observations made in the analysis, the following improvements were recommended for consideration: Diverging Diamond Intersection, Alternative C Westbound On Ramp -Improved Grade, Options A and C* SH 9/Wildernest Intersection, Options A and C* A continuous eastbound auxiliary lane from the Frisco Interchange to the Silverthorne/Dillon Interchange is also evaluated, but at a lesser level of detail than the interchange area alternatives and options. The auxiliary lane is a stand-alone project that could be phased. The auxiliary lane requires further study. *The Westbound On Ramp Option A (improved grade) and Option C (improved grade and two-lane on ramp over the Blue River) are related in that Option A provides a phased implementation that allows early action that can later be expanded to include Option C buildout. This offers flexibility to implementation depending on the construction funding available. At the SH 9/Wildernest intersection, Option A is the ultimate buildout design and Option C (interim) is the phased implementation that allows early action that can later be expanded to include Option C buildout.

The rationales for selecting the Diverging Diamond alternative, associated options and packaging strategy are described in Section 3.2.2 of the Detailed-Level Screening Analysis. In summary, the Diverging Diamond resolves many of the issues at the interchange for conditions anticipated in 2035, and when combined with the selected options fully addresses the project’s purpose and need at a far lower cost than other possibilities with very low impacts, and can be constructed in several phases as funding becomes available.

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

2035 Levels of Service with the proposed improvements are provided in Table 1.

Table 1

2035 Level of Service (LOS) with the Proposed Improvements

Location WB I-70 On Ramp

2035 LOS C

EB I-70 Off Ramp

C

WB I-70 Off Ramp

C

EB I-70 On Ramp

C

WB I-70 and SH 9 Ramp Intersection

C

EB I-70 and US 6 Ramp Intersection

C

6th and SH 9 Intersection

B

5th and SH 9 Intersection

A

4th and SH 9 Intersection

B

3rd and SH 9 Intersection

A

Nike Driveway and SH 9 Intersection

A

Wildernest and SH 9 Intersection

C

Stephens and US 6 Intersection

A

Little Beaver Trail and US 6 Intersection

B

Anenome Trail and US 6 Intersection

A

Dillon Ridge Road and US 6 Intersection

D

Proposed Action Figures 4, 5 and 6 present the preliminary design layouts for the recommended improvements. A design layout has not been prepared for the continuous eastbound auxiliary lane from the Frisco interchange to the Silverthorne interchange. The auxiliary lane is a stand-alone project that requires further study.

Conceptual narratives and additional drawings for the recommended improvements are provided in the Detailed-Level Screening Analysis (See Appendix E).

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WB ON RAMP PLAN SHEET OPTION A - 2 LANES

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File Name: 6300RDY_DETAIL_SH9_WILDERNEST_INTERSEC_Ultimate_A_02.dgn Date: Horiz. Scale: 1:50 Unit Information

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

II

ENVIRONMENTAL CONSEQUENCES, MITIGATION COMMITMENTS AND MITIGATION MEASURES OF THE PROPOSED ACTION

Summary of Consequences and Anticipated Mitigation Based on the package of improvements recommended by the study, Table 2 summarizes the environmental consequences and anticipated mitigation measures for all improvements together.

Table 2 Summary of Environmental Consequences and Anticipated Mitigation Measures

ENVIRONMENTAL CONSEQUENCES

MITIGATION MEASURES

1. Air Quality: Inconsequential effects on pollutant concentrations and existing attainment status 2.Geologic Resources and Soils: None 3. Water Quality: Construction and postconstruction discharges of stormwater into Straight Creek and the Blue River from excavation, grading, pavement removal and paving would present the potential to increase contaminant levels in stormwater.

Impervious surface area and runoff quantities would increase.

4. Floodplains: Minor fill within the channel of Straight Creek would be required, but no residual floodplain or adverse stormwater flow effects would be expected. The new westbound on ramp bridge over the Blue River may include construction within or near the floodplain.

5. Wetlands: The proposed improvements will require fill of 0.175 acres of wetlands.

6. Vegetation: Fill slope grasses along the Westbound On Ramp, landscaped areas, and vegetation associated with minor fills near the Straight Creek Crossing of US 6 will be displaced.

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Standard construction phase measures to control dust and minimize air pollutant emissions will be applied.

Geotechnical engineering requirements for foundations and retaining walls will be applied.

Specific mitigation measures resulting from the required Clean Water Act (CWA) Section 402 Stormwater Permit, the CWA Section 404 Nationwide Permit, the Colorado Discharge Permit System (CDPS) Construction Storm-Water Permit and from the CDOT Storm Water Management Plan (SWMP) will be applied.

Detention ponds and drainage improvements based on hydraulic analyses will be part of the final design to address floodwater flows.

Detention ponds and drainage improvements based on hydraulic analyses will be part of the final design to address floodwater flows.

Foundations for the bridge over the Blue River would be located to avoid and/or minimize impacts on the Blue River’s 100-year floodplain.

Clean Water Act Section 404 Nationwide Permit requirements and corresponding mitigation measures will apply. The Final Design process would be expected to avoid and minimize wetlands impacts to the extent possible, and incorporate wetland features to compensate for wetland disruption and losses.

Disrupted areas will be landscaped or revegetated with approved seed mixes.

STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

ENVIRONMENTAL CONSEQUENCES

MITIGATION MEASURES

7. Noxious Weeds: Earthwork for the project presents the potential to encourage the spread of noxious weeds.

8. Fish and Wildlife: Construction and shading effects under the new bridge over the Blue River present the potential to adversely impact habitat conditions for fish and wildlife. Sunny fishing sites would be replaced with shaded sites.

Standard construction phase measures to control noxious weeds will be applied.

The improvements present the potential to impact Migratory Birds.

Foundations for the bridge over the Blue River would be located to avoid and/or minimize impacts on the Blue River’s 100-year floodplain.

SB40 Wildlife Certification requirements and standard water quality control practices for construction adjacent to stream channels will be applied in relation to impacts on the Blue River and Straight Creek.

Construction work affecting migratory birds will comply with the requirements of the Migratory Bird Treaty Act and will be performed according to CDOT specifications to avoid impacts to migratory birds before and during construction.

Also, mitigation of protected bird and fish species will comply with South Platte Water Related Activities Program, the Platte River Recovery Implementation Program, and the Colorado River Recovery Implementation Program.

Seasonal limitations on construction may apply.

These requirements would be based on the findings of required field surveys for active nest sites performed prior to construction activities.

An Initial Biological Resources Report will be prepared as a technical appendix to NEPA documentation to verify this finding or to address any issues that exist.

9. Threatened and Endangered Species: Based on the project footprint and environmental commitments and requirements, no threatened or endangered species, or critical habitat, would be adversely impacted.

10. Tribal Resources: None 11. Archaeological Resources: The potential exists to encounter archaeological resources during excavation, but no significant resources are known to exist in areas to be disrupted.

12. Historic Properties: None

-An Archaeological Survey and coordination with the SHPO in accordance with Section 106 of the National Historic Preservation Act will occur during the NEPA process.

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

ENVIRONMENTAL CONSEQUENCES

MITIGATION MEASURES

13. Paleontological Resources: Excavation associated with the auxiliary lane and bridge foundations for the Westbound Two Lane On Ramp present the potential to encounter paleontological resources.

All construction in areas of moderate or high paleontological sensitivity will include preconstruction survey and evaluation, construction monitoring, implementation of a Worker Awareness Training Program, and spotcheck monitoring of sensitive formations during construction. All work will be overseen by the CDOT staff paleontologist or other qualified and permitted paleontologist and will follow CDOT’s Paleontology Analysis and Documentation Procedures (CDOT, 2006). In the event of discovery of unanticipated fossil remains, such as unexpected concentrations of fossils, unusually large specimens, or unexpected discoveries in sediments, all ground disturbances in the area will cease immediately. The qualified paleontologist and appropriate project personnel will be notified immediately to assess the find and make further recommendations.

Mitigation will follow the Society of Vertebrate Paleontology Standard Guidelines (Society of Vertebrate Paleontology, 1995) for treatment of sensitive paleontological resources and CDOT Paleontology Analysis and Documentation Procedures (CDOT, 2006).

-Acquisition of ROW involves following established procedures of the Uniform Act. Fair market values will be determined and compensation for real estate losses will be determined and paid.

14. Land Use: None (See ROW) 15. Residential/Business ROW Relocation: The improvements in total would require acquisition of 0.73 acres of private property for new CDOT ROW. The ROW acquisition would not require business displacement, but would hinder six access points and eliminate two access points (details to be resolved during the final design process).

16. Social Resources: None 17. Environmental Justice: None

-The NEPA documentation will evaluate the 2010 Census data to confirm local conditions within and adjacent to the Study Area. The reevaluation will determine if the project will cause disproportionately high and adverse effects on any minority or low-income populations in accordance with the provisions of Executive Order 12898 and FHWA Order 6640.23.

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

ENVIRONMENTAL CONSEQUENCES

MITIGATION MEASURES

18. Bicycle and Pedestrian Facilities: See Section 4(f) 19 Transportation Resources: Construction period delays and detours would be expected. Long term effects would be beneficial.

20. Section 4(f): The construction of the westbound on ramp bridge foundations adjacent to the Blue River Trail and overhead construction would present the potential to temporarily block the trail, temporarily disrupt the aesthetic qualities of the trail during construction, and incrementally increase shading and decrease aesthetic qualities associated with the trail after bridge construction.

The Diverging Diamond interchange requires 0.024 acres of ROW from a Town of Silverthorne open space (approximately 3 acres) that may be a protected resource under Section 4(f). This unavoidable impact involves less than one percent of the open space area and would not have a substantive impact on its roles or functions.

21. Section 6(f) Resources: See Section 4(f) for Blue River Trail effects. There would be no effects to Rainbow Park 22. Farmlands: None 23. Noise: No sensitive receptors would be subject to more than a 2.5 dBA increase in noise as an impact of the proposed improvements.

Six (6) sensitive receptors are already exposed to noise levels that exceed the NAC. Five (5) additional sensitive receptors would be subject to noise levels that exceed the NAC under 2035 No Build and Build conditions. Noise abatement in these areas should be analyzed.

The difference between the noise levels under Build and No Build conditions is minimal with a maximum difference of only 1.3 dBA.

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See Section 4(f) Standard measures to address construction period traffic flow requirements and business access needs would be implemented.

The Section 4(f) de minimis documentation would be prepared as part of the NEPA process.

This documentation and the Section 404 Nationwide permit process would define avoidance, minimization and mitigation measures for the anticipated effects on these resources.

See Section 4(f)

-A complete noise analysis will be performed as part of the NEPA documentation to verify or revise these findings and to determine what, if any, mitigation is needed due to I-70 traffic from milepost 202.7 (Frisco Interchange) to milepost 207.5 (Upper end of residential area along Straight Creek). The noise analysis should comply with CDOT’s recently adopted noise guidance.

STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

ENVIRONMENTAL CONSEQUENCES

MITIGATION MEASURES

24. Visual Resources/Aesthetics: The improvements would involve temporary aesthetic impacts associated with construction disruption and the removal of existing landscape features.

Revegetation plans, landscape details and final design features would be proposed in a manner that complies with the I-70 Mountain Corridor Context Sensitive Solutions (CSS) requirements and guidelines along with local policies. These details and the need to address bridge paint and other existing features would be addressed in the Final Design process. The “Silverthorne – Area of Special Attention Report” will be one basis for developing Final Design details.

None required or recommended.

25. Energy: The improvements require the use of energy for construction and operation of the proposed facilities and would increase energy efficiency associated with motor vehicle travels by increasing capacity and improving traffic operations.

26. Hazardous Materials: Numerous hazardous waste sites occur within the study area. The planned improvements may encounter contaminated soil and or groundwater.

27. Cumulative Effects: The incremental impacts of the planned improvements contribute similar effects from past, present and reasonably foreseeable projects. These effects were identified and described in detail in the I-70 Mountain Corridor Final PEIS.

A Phase I Initial Site Assessment (Form 881), a MESA, or a Phase I Environmental Site Assessment will be prepared prior to right of way acquisition. These studies will determine the need for Phase II analysis and the need for project specific mitigation measures. Standard practices associated with worker safety during earthwork and dewatering will be required.

Mitigation from the I-70 Mountain Corridor Final PEIS and Record of Decision will be implemented to address cumulative effects from the proposed action. No additional mitigation measures are required or recommended.

Water quality and wetland issues are being addressed by the implementation of Sediment Control Action Plans, water quality monitoring programs and the Stream and Wetland Ecological Enhancement Program (SWEEP). With the propose improvement, similar measures will be implemented for project specific effects.

The primary incremental effects of the proposed project contributing to cumulative effects in the area include: Degraded Water Quality in Straight Creek and the Blue River (sediment and total annual phosphorus loading) Incremental Losses of Wetland and Riparian Areas 28. Public Controversy: None

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29. Anticipated Permits: The following permits are

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

ENVIRONMENTAL CONSEQUENCES

MITIGATION MEASURES

anticipated: Clean Water Act Section 402 Stormwater Permit Clean Water Act Section 402 Dewatering Permit Colorado Discharge Permit System (CDPS) Construction Storm-Water Permit Clean Water Act Section 404 Nationwide Permit Municipal Permit (Wastewater Discharge) 30. Significant Effects: None

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

III NEPA PROCESS RECOMMENDATION Overview Based on the characteristics of the proposed improvements, their potential environmental consequences, and applicable procedural requirements, a documented Non-Programmatic Categorical Exclusion (CatEx) may be the appropriate level of NEPA documentation for the proposed improvements.

Non Programmatic Categorical Exclusion: Applicability and Requirements A Non-Programmatic CatEx is for actions that meet the criteria for a CatEx in the CEQ regulations (CEQ, 40 CFR ยง 1508.4) if they are appropriately analyzed, documented, and approved by FHWA. The documentation must demonstrate that the specific conditions or criteria for the CatEx are satisfied and that significant environmental effects will not result. The proposed improvements have characteristics consistent with non-programmatic action.

Non Programmatic Categorical Exclusion: Tasks to Complete the Process CDOT staff, typically the CDOT Regional Planning and Environmental Manager (RPEM), decides the appropriate class of NEPA documentation needed for a project in consultation with FHWA once funding for the project is available. However, FHWA makes the final determination on class of action.

If a CatEx is prepared, CDOT Form 128 will be completed and supporting documentation will be prepared, as needed. The CatEx would be prepared once funding for one or more of the improvements is secured. If the process moves forward, CDOT and FHWA will discuss and resolve final details associated with the Final CatEx process. The responsibilities for individual tasks will be determined by CDOT. An overall summary of the Non Programmatic CatEx steps is provided as follows: Internal Scoping Project Planning and Programming Environmental Clearances/Documentation Field Inspection Review (FIR) Form 128 FHWA Non-Programmatic Categorical Exclusion Environmental Review Summary Final Office Review (FOR) Final Check Environmental Project Certification Construction

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STATE HIGHWAY 9 AND US HIGHWAY 6 IMPROVEMENT PROJECT AT THE INTERSTATE 70 SILVERTHORNE/DILLON INTERCHANGE

IV

NEXT STEPS

Funding for recommended improvements has not been secured so the next step in the process is to secure some or all of the funding needed for project construction. Once funding is available, the funded portions of the project would be subject to the NEPA clearance process. The outcome of the NEPA process would lead to a final decision about the proposed action. If a build alternative is selected, final design and construction would follow.

CDOT will continue to evaluate opportunities to advance the final design, NEPA clearance, and Construction Phasing strategy based on funding availability.

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