INTERNAL TRAFFIC CIRCULATION PLAN

INTERNAL TRAFFIC CIRCULATION PLAN

SET Engineering

[Email address]

Flatiron Internal Road Design

The purpose of this memorandum is to discuss the design standards applied to the proposed roadway improvements for the Flatiron Montana project. All improvements proposed were designed in accordance with Gallatin County Transportation and Construction Standards (Gallatin County’s Standards) or Madison County Subdivision Standards where possible, and in full coordination with MDT design standards where applicable. Where design elements deviate from County Standards, the most recent version of the AASHTO published Geometric Design of Highways and Streets is utilized.

Project Background

The proposed project is multi-year, mixed-use, development on 473-acres located within Madison and Gallatin Counties and consists of the following uses on site: mixed density residential housing, various commercial lodging options (B&B, hotel rooms, etc.), restaurants, shops, and other uses typical of a ski resort. The discussion herein pertains to Entitlement Exhibit 3a Roads and Trails Plan Overall. The Flatiron design elements are as follows:

• Road Type: All internal roads are designed as Mountainous Local roads.

• Design Speed: 15-20 mph (Deviation from Madison and Gallatin County Standard).

• Maximum Superelevation: e=4-6%.

• Minimum radius: 61 feet (Deviation from Madison and Gallatin County Standard).

o Uses applicable AASHTO Standards with reduced speed (e = 6% and speed = 15 mph).

o Big Sky Fire Department requested minimum of 61-foot residential minimum to accommodate a Type 1 fire engine and 75-foot commercial radius to accommodate a ladder truck.

• Maximum grade: 10%

• All MDT right-of-way approaches consist of 3% grade for at least 150-feet.

For each jurisdiction, these road design elements, as well as terrain and winter weather conditions at the project, are assessed with respect to key elements of design (e.g. Design Speed, Minimum Radii, and Superelevation) Madison County Standards

Per Madison County Subdivision Standards, Section 10: Roadway Design, Material, and Drainage Standards:

Assessment of Design

The design uses a design speed ranging from 15-20 mph. However, where site/topography limitations are present, a design speed lesser than defined in Madison County’s Mountainous terrain classification for high building density is proposed. Appropriate AASHTO standards are maintained for those locations, as allowed in Section 10. a. (2).

The roads as presented in the corresponding preliminary road improvement plans have been designed in accordance with current AASHTO guidelines.

Gallatin County Standards

Per Gallatin County Standards for a local mountainous road, the following roadway design criteria were applied where possible:

Assessment of Design

Consistent curvature and visual cues are used to maintain driver attention and to control travel speeds. Where longer straight sections are necessary, larger curves are used to gradually transition driver expectations before entering a lower speed section of road. Where low speed sections of road are proposed, consistent curves with tangent sections short enough to control speeds and long enough to allow for adequate recovery are used.

The use of design speed and subsequent design elements of superelevation and radii are necessary to accommodate the topography present throughout the project. Superelevation rates are limited due to winter driving conditions. AASHTO recommends no superelevation greater than 6% in urban conditions and 8% in rural winter conditions due to lateral sliding while stopping or accelerating. A maximum superelevation of 6%

is used in the current design.

In areas where sharp horizontal curves were used on steep downgrades of the mountainous topography, design speeds ranging from 15-20 mph and appropriate minimum radii are used. In these locations, proposed design speeds deviate from those defined in Gallatin County Standard’s local mountainous criteria (<25 mph), and AASHTO Standards are applied.

Per AASHTO Section 3.3.3. Minimum Radius, “Sharp horizontal curves (or near-minimum radius curves) on downgrades of 4% or more should not be designed using low speeds (i.e., 30 mph or less). In the event that

SITE

such situations cannot be avoided, warning signs to reduce speeds well in advance of the start of the horizontal curve should be used.”

Also, per AASHTO Section 5.3.1.1 Design Speed: “Design speed is not a major factor for local streets in urban areas because in the typical street grid, the closely spaced intersections usually limit vehicular speeds. For consistency in design elements, design speeds ranging from 20 to 30 mph may be used since the function of local streets is to provide access to adjacent property, all design elements should be consistent with the character of activity on adjacent to the street, and should encourage speeds generally not exceeding 30 mph.”

Conclusion

It is our opinion that the use of AASHTO Standards with the proposed design speeds of 15-20 mph are reasonable in this context with the following conditions being accounted for: advanced warning signage and reduced speed limit signage, managed consistency and driver expectations, and superelevation used to minimize curve severity while not to exceed 6% to mitigate sliding during slippery conditions. Detailed roadside safety/design considerations are to be addressed in final design submittals.

Please contact Anderson Engineering, Inc. directly with any question regarding traffic analyses for the subject project.

Sincerely,

William H. Anderson, P.E., P.L.S.

[email protected] (406) 925-0590

Attachments:

A. Circulation Plan w/ Areas of County Standard Deviation Identified.

B. Supplemental AASHTO Standards and sections of the AASHTO Green Book.

C. Preliminary Plans and Profiles Existing Lone Moose Drive and Proposed Lone Moose Drive.

ATTACHMENT A:

CIRCULATION PLAN

W

TRACT 2

(MINOR SUB 257A) 350.71 ACRES TRACT 1

(COS 1550) 184.582 ACRES

MADISON COUNTY GALLATIN COUNTY

HWY 64

MIDDLE FORK WEST FORK GALLATIN RIVER LOT 1A OF MINOR SUB 257A

EXISTING LONE MOOSE MEADOWS CONDOS

APPROACH A

Road A (Kircher Drive) APPROACH B

LONE MOOSE DRIVE

ROAD B (Middle Fork Drive) ROAD E2

APPROACH C

ROAD C (Toboggan Trail) APPROACH D ROAD D

(Long Gun Drive)

ROAD E1 (THUNDERWOLF LANE )

R=128'

R=130' R=170'

R=140'

R=130' R=85'

R=135' R=145'

R=130'

R=80' HWY 64

HWY 64 HWY 64

R=80' MIDDLE FORK WEST FORK

GALLATIN RIVER

R=110'

R=90' R=75'

Road AB (SIX GUN LANE)

L2 L1 L3

M

N

A B

J C

I G

H E F2

F1

D

K

29 28 32 33

28 27 33 34 28 27 29 28

28 33 29

32

20 21 29 28

W2

W1 V6

V5 V4

V3 V2

V1

U

T

S

R1

R2

Q

P

S

S S

S S

S S S S S S S

S S S S

S

S S

S S S S S

S S S

S S

S S

S S S S S

S S

S

R=140' R=108'

R=75' R=90'

R=95'

LEGEND

PROPERTY LINE

PROPOSED ROAD

BUILDING ENVELOPES

STREAMS

© 2021 ANDERSON ENGINEERING INC., THIS DRAWING AND ASSOCIATED ELECTRONIC FILES ARE THE WORK PRODUCT OF ANDERSON ENGINEERING, INC AND REUSE OF FILES IS BY LIMITED PERMISSION FROM ANDERSON ENGINEERING, INC.

SHEETDate: Drawn By: Checked By: Revisions:

FLATIRON MADISON/GALLATIN COUNTY, MT S28 & S29, T6S, R3E

Filename:MFM BASE MAP 6.14.DWG Sheet:C-102 CIRC Location:C:\USERS\BILL\DROPBOX (ANDERSON ENGINEERING)\ANDERSON ENGINEERING, INC PROJECTS\MIDDLE FORK MEADOWS\CAD Plotted:9/9/2021 Plotted by:BILL 09/08/2021 MS WHA 6.14 3731 Equestrian Lane, Suite 102., Bozeman, MT 59718 Phone: (406) 600-7590

SYNERGY

NOTE: PRELIMINARY PURPOSES ONLY, NOT A FINAL DESIGN

REQUESTED VARIANCES FROM REGULATION:

1. VARIANCE IS REQUESTED FOR RADII LESS THAN 150' IN GALLATIN COUNTY. MINIMUM RADIUS IS BASED ON BIG SKY FIRE DEPARTMENT DEVELOPMENT GUIDELINES. 75' MINIMUM RADIUS FOR ROADS ACCESSING COMMERCIAL BUILDING ENVELOPES AND 61' MINIMUM RADIUS FOR ROADS ACCESSING RESIDENTIAL BUILDING ENVELOPES.

SCALE: 1"=800'

0 800 1200

ATTACHMENT B:

SUPPLEMENTAL AASHTO STANDARDS

Supplemental AASHTO Standards

From A Policy on Geometric Design of Highways and Streets, 2018, 7^th Edition, 2^nd Printing By the American Association of State Highway and Transportation Officials (AASHTO)

Chapter 3 Elements of Design

3.3.3 Minimum Radius

“For two-lane roadways, the difference between the roadway centerline and the center of gravity used in the horizontal curve equations is minor. Therefore, the curve radius for a two-lane roadway may be measured to the centerline of the roadway.”

“Sharp horizontal curves (or near minimum-radius curves) on downgrades of 4 percent or more should not be designed using low design speeds (i.e., 30 mph or less). In the event that such situations cannot be avoided, warning signs to reduce speeds well in advance of the start of the horizontal curve should be used.”

3.4 Vertical Alignment 3.4.6 Vertical Curves

“… the checking of plans is simplified by comparing all curves with the design value for K.”

Crest Vertical Curves

Sag Vertical Curves

5 Local Roads and Streets

“In constrained or unusual conditions, it may not be practical to meet the design criteria presented in this chapter. In such cases, the goal should be to obtain the best practical alignment, grade, sight distance, and drainage that are consistent with terrain, development (present and anticipated), crash reduction, and available funds.”

5.3 Local Streets in Urban Areas 5.3.1.1 Design Speed

“Design speed is not a major factor for local streets in urban areas because in the typical street grid, the closely spaced intersections usually limit vehicular speeds. For consistency in design elements, design speeds ranging from 20 to 30 mph may be used… Since the function of local streets is to provide access to adjacent property, all design elements should be consistent with the character of activity on adjacent to the street, and should encourage speeds generally not exceeding 30 mph.”

5.3.1.2 Design Traffic Volume

“Design traffic volumes in such areas should be forecast for at least 10 years, and preferably 20 years, into the future.”

5.3.1.4 Alignment

“Alignment in residential areas should closely fit with the existing topography to minimize the need for cuts or fills. The function of local streets in residential areas is to provide land access, and therefore these streets should be designed to discourage through traffic. Street alignment in commercial and industrial areas should be commensurate with the topography but should be as direct as possible.

The minimum radius for horizontal curves should be the greater of 100 ft or the minimum radius for the applicable design speed…”

5.3.1.5 Grades

“Grades for local residential streets should be as level as practical, consistent with the surrounding terrain. Grades for local residential streets should be less than 15 percent…

Streets in commercial and industrial areas should have grades less than 8 percent, and flatter grades should be encouraged.”

5.3.1.7 Superelevation

“Superelevation on horizontal curves may be advantageous for local street traffic operations in specific locations, but in built-up areas the combinations of wide pavement areas, proximity of adjacent development, control of cross slope, profile for drainage, frequency of cross streets, and other urban features often combine to make the use of superelevation impractical or undesirable. Therefore, superelevation usually is not provided on local streets in residential and commercial areas; it may be considered on local streets in industrial areas to facilitate operation.

If superelevation is used, horizontal curves should be designed for a maximum superelevation rate of 4 percent. If terrain dictates sharp curvature, a maximum superelevation rate of 6 percent may be justified if the curve is long enough to provide an adequate superelevation transition.”

5.3.1.8 Sight Distance

“Minimum stopping sight distance for local streets should range from 100 to 200 ft depending on the design speed.”

ATTACHMENT C:

PRELIMINARY PLANS AND PROFILES

L1

M

B J

C

I G

H E F2

F1

D

K 0+00

5+00

10+00

15+00

20+00

25+00

30+00 35+00

40+00 42+76

R=148

R=146 R=184

R=123

LEGEND

PROPERTY LINE

EXISTING LONE MOOSE DRIVE PROPOSED LONE MOOSE DRIVE BUILDING ENVELOPES

WATERCOURSE SETBACK

Elevation

Station

6750 6800 6900 7000 7100 7200 7300

6750 6800 6900 7000 7100 7200 7300

0+00 5+00 10+00 15+00 20+00 25+00 30+00 35+00 40+00 42+76

-6.91%

-3.78%

-0.27%

-11.82%

-11.61%

-9.56%

-10.31%

-9.25%

-6.24%

-5.55%

-3.81%

SCALE: 1"=500'

0 250 500

NOTE: PRELIMINARY PURPOSES ONLY, NOT A FINAL DESIGN

PLAN VIEW EXISTING LONE MOOSE DR.

PROFILE OF EXISTING LONE MOOSE DR.

© 2021 ANDERSON ENGINEERING INC., THIS DRAWING AND ASSOCIATED ELECTRONIC FILES ARE THE WORK PRODUCT OF ANDERSON ENGINEERING, INC AND REUSE OF FILES IS BY LIMITED PERMISSION FROM ANDERSON ENGINEERING, INC.

SHEET

FLATIRON MADISON/GALLATIN COUNTY, MT S28 & S29, T6S, R3E

Filename:MFM BASE MAP 6.12.DWG Sheet:E LONE MOOSE DR. PROFILE Location:C:\USERS\SPEAK\SEAK DROPBOX\SEAK PROJECTS\MFM\CAD Plotted:3/22/2021 Plotted by:SPEAK 03/22/2021 MS WHA 6.12 3731 Equestrian Lane, Suite 102., Bozeman, MT 59718 Phone: (406) 600-7590

SYNERGY

L1

M

B J

C

I G

H E F2

F1

D

K L16 L17

L18 L19

W

25+00

30+00

35+0035+23

0+00

5+00

10+00 0+00

5+00

10+00

15+00

20+00

25+00

30+00

35+00

40+00 45+00

50+00

55+00 56+66

35+00 40+00

45+00

47+62

0+00 5+00

10+00

LEGEND

PROPERTY LINE

EXISTING LONE MOOSE DRIVE PROPOSED LONE MOOSE DRIVE BUILDING ENVELOPES

Elevation

Station

6750 6800 6900 7000 7100 7200 7300

6750 6800 6900 7000 7100 7200 7300

0+00 5+00 10+00 15+00 20+00 25+00 30+00 35+00 40+00 45+00 50+00 55+00 56+66

-5.77%

-8.12%

-8.02%

-8.20%

-4.71%

PLAN VIEW LONE MOOSE DR.

PROFILE OF PROPOSED ALIGNMENT LONE MOOSE DR.

© 2021 ANDERSON ENGINEERING INC., THIS DRAWING AND ASSOCIATED ELECTRONIC FILES ARE THE WORK PRODUCT OF ANDERSON ENGINEERING, INC AND REUSE OF FILES IS BY LIMITED PERMISSION FROM ANDERSON ENGINEERING, INC.

SHEET

FLATIRON MADISON/GALLATIN COUNTY, MT S28 & S29, T6S, R3E

Filename:MFM BASE MAP 6.14.DWG Sheet:LONE MOOSE DR. PROFILE Location:C:\USERS\MARLENE\DROPBOX (ANDERSON ENGINEERING)\ANDERSON ENGINEERING, INC PROJECTS\MIDDLE FORK MEADOWS\CAD Plotted:9/10/2021 Plotted by:MARLENE 09/08/2021 MS WHA 6.14 3731 Equestrian Lane, Suite 102., Bozeman, MT 59718 Phone: (406) 600-7590

SYNERGY

SCALE: 1"=500'

0 250 500

PROPOSED