St. Croix River Crossing Project Visual Quality Manual ... · St. Croix River Crossing Project Visual Quality Manual Addendum Final Submission PREPARED FOR: MINNESOTA DEPARTMENT OF

St. Croix River Crossing Project Visual Quality Manual Addendum

Final Submission

PREPARED FOR: MINNESOTA DEPARTMENT OF TRANSPORTATION

WISCONSIN DEPARTMENT OF TRANSPORTATION

PREPARED BY: PARSONS BRINCKERHOFF

St. Croix River Crossing Project - Visual Quality Manual Addendum

Final Submittal i

TABLE OF CONTENTS

1.0 INTRODUCTION ......................................................................................................................................... 1 1.1 GENERAL DESIGN INTENT ..................................................................................................................... 2 1.2 VISUAL QUALITY REFINEMENTS ........................................................................................................... 2 2.0 RIVER CROSSING (Mn/DOT Bridge 82045, WisDOT Bridge B-55-224) .................................. 3 2.1 CONCEPT COLUMN DESIGN ................................................................................................................... 3 2.2 APPROVED DESIGN REFINEMENT ........................................................................................................ 3 2.3 COLUMN FORM AND DETAIL ................................................................................................................. 3 2.4 CONCRETE FILL ......................................................................................................................................... 6 2.5 CROSS GIRDER DESIGN AND FORM ....................................................................................................... 7 2.6 MAIN SPAN BOX GIRDER CONFIGURATION AND DEPTH ................................................................... 8 3.0 PEDESTRIAN /BIKE TRAIL ....................................................................................................................11 3.1 CONCRETE PARAPET/RAILING BASE ..................................................................................................12 3.2 METAL RAILING ELEMENTS ................................................................................................................13 3.3 PEDESTRIAN/VEHICLE PROTECTION BARRIER ...............................................................................14 3.4 OVERLOOK PLATFORMS ........................................................................................................................16 3.5 CABLE CONNECTION HOUSING ............................................................................................................19 4.0 NIGHT LIGHTING....................................................................................................................................21 4.1 ROADWAY LIGHTING .............................................................................................................................21 4.2 PEDESTRIAN/BIKE TRAIL LIGHTING .................................................................................................22 4.3 AESTHETIC LIGHTING ...........................................................................................................................23 5.0 MINNESOTA APPROACH STRUCTURES (MN/DOT BRIDGES 82045, 82047 & 82048) ............26 5.1 BOX GIRDER DEPTH TRANSITION .......................................................................................................26 5.2 APPROACH SPANS/ NE, SE RAMP – COLUMN DESIGN ...................................................................27 5.3 MINNESOTA APPROACH SPAN ARRANGEMENT AND PIER PLACEMENT .....................................30 5.4 MINNESOTA APPROACH ABUTMENT ..................................................................................................31 5.5 MINNESOTA NE, AND SE RAMP STRUCTURES AND ABUTMENTS .................................................32 6.0 WISCONSIN ABUTMENT ........................................................................................................................33 7.0 STRUCTURE COLOR ................................................................................................................................34 8.0 ANTI-ICING FACILITIES .........................................................................................................................35


Final Submittal 1

1.0 Introduction

The purpose of this Visual Quality Manual Addendum (VQMA) is to document the design refinements of the St. Croix River Crossing Bridge completed as a part of the engineering contract No. 92530 undertaken from February 2009 through June of 2010. These refinements supplement and supersede the design direction of the original Visual Quality Manual VQM completed in 2007.

During the execution of engineering contract 92530 (the preliminary engineering phase of the project), stakeholder involvement continued through the formation of a Visual Quality Advisory Committee (VQAC). The VQAC comprised the following subset of the original VQRC member organizations:

• City of Bayport, MN • City of Oak Park Heights, MN • City of Stillwater, MN • Town of St. Joseph, WI • Minnesota State Historic Preservation Office • National Park Service

The VQAC performed the following role during the execution of contract No. 92530:

• Perpetuated the work accomplished through the Environmental Process and Visual Quality Process.

• Assisted the Project Team by interpretation of the Visual Quality Manual in areas where the intent was not fully defined.

• Advised the Project Team regarding refinements to the conceptual design as a result of the preliminary engineering phase.

• Assisted the Project Team in evaluating how newly discovered constraints revealed during preliminary engineering relate to the previously developed concept design.

• Attended VQAC Meetings to provide input and comment on visual quality issues related to the preliminary engineering.

• Reported to their constituency groups how the refinements and advancement of the design compare and contrast with the original VQM design.

In addition to the VQAC efforts, general public involvement was continued through two open houses, where the concept refinement was presented for public input and comment.


Final Submittal 2

1.1 General Design Intent

The VQM defines the selected design theme “Organic” and resulting concept with these descriptors:

• The parts look as if they were found in nature, or shaped by natural forces. • The vertical pier forms are reed-like; the girders are rounded and tapered like bones or

tree branches; and walls, barriers and railings are curved and blended into the larger forms.

• Transitions are gradual and smooth; edges are soft and curved; and colors are unified and natural expressions of their materials.

Maintaining these values were the basis for evaluations and aesthetic alternative design recommendations for the structural elements of the bridges during the execution of the tasks in contract No. 92530.

1.2 Visual Quality Refinements

The Visual Quality refinement activities were performed concurrent with the other engineering and analysis tasks undertaken during the execution of engineering contract No.92530. This concurrent work allowed for interaction of the visual quality team and the engineering teams to evaluate the aesthetic alternatives concurrent with the multiply engineering analysis being conducted under this contract. PB together with representatives from Minnesota Department of Transportation (Mn/DOT) and Wisconsin Department of Transportation (WisDOT) discussed a number of aesthetic design alternatives which were then presented to the Visual Quality Advisory Committee (VQAC) for input and comment. The VQAC provided comment and noted preferences for specific alternatives which are summarized and more fully defined in the following VQMA.


Final Submittal 3

2.0 River Crossing

(Mn/DOT Bridge 82045, WisDOT Bridge B-55-224)

This structure is composed of 8 extradosed supported concrete box girder spans which depart +- 70’ above the Minnesota bank and ascends to a landing point near the top of the bluff on the Wisconsin side of the St. Croix River.

2.1 Concept Column Design

The concept pier design for the river crossing structure included a three-column pier with two exterior columns that extend above the roadway deck to provide an attachment for the stay cables, while an interior column was centered under the cross girder along the centerline of bridge. During development of the VQM, the preference of the VQRC was to have a two-column pier.

2.2 Approved Design Refinement

Through technical analysis of the structure it was possible to confirm that the number of columns at each pier could be reduced from three to two. This was achievable without changing the size, form or proportions of the column.

2.3 Column Form and Detail

In an effort to improve constructability and reduce cost, a number of refinements to the column form were explored. The refined column retains the visual character of the original VQM column while providing for an enhanced level of constructability. The approved column design consists of a uniform sloping and canted exterior on the three outside column faces while the inboard face is vertical and uniformly tapered. To achieve this form, short tangent segments were introduced into the column section on all four sides so that transitional blocking could be more easily introduced into the formwork. The interior face of the twin column sections were closed with a single tangent surface. This was in part to enhance constructability and to reduce cost.


Final Submittal 4

View of River Pier looking east Outside View Inside View Sections

View of River Pier without pedestrian overlook


Final Submittal 5

View of River Pier looking east Looking south Sections

For enlargement of fill at column base see image below.

View of River Pier without pedestrian overlook


Final Submittal 6

2.4 Concrete Fill

Near the base of the river columns, a sloped concrete fill was added between the stems. The top of the fill area at the open side of the column is to be equal in height to the normal pool surface water elevation and slope upward toward the closed portion of the column. The purpose for the fill is to:

• prevent entry of small vessels or persons into the opening in the column. • protect the columns from ice intrusion and reduce lodging of floating debris.

Section view of column with concrete fill Inside view of column with concrete fill


Final Submittal 7

2.5 Cross Girder Design and Form

The cross girder is an important element which visually and structurally joints a pair of columns to create a typical river pier. The specific width and depths of the cross girder have been established to meet the structural necessities of the member. The engineering analysis has confirmed that the VQM depth and width of the cross girder are sufficient but that the depth can be reduced in proportion to the girder depth reduction as described in section 2.6 . However, it has been determined that the contact surface area of the cross girder with the column must be increased. To achieve a greater contact area it is necessary to reduce the radius on the lower outside edge of the cross girder at the interface with the column or “tower” legs. The original concept of a curved outer edge along the cross girder has been retained. This has resulted in a slightly different but acceptable visual appearance of the cross girder. To further integrate the cross girder with the column the slope of the outer vertical edge of the cross girder will match the slope of the outside column face.

Note:

Vertical edge of cross girder matches slope of outside column face.

Lower edge of cross girder has a radius of (7’-6”)

View of cross girder end along north elevation of overlook

View of cross girder looking east along south side of river structure.


Final Submittal 8

2.6 Main Span Box Configuration and Depth

(Mn/DOT Bridge 82045, WisDOT Bridge B-55-224)

A major design directive of contract No. 92350 was to identify refinements in the design which would provide cost savings while still maintaining the overall appearance of the structure. After detailed analysis it became clear that the application of the extradosed technology to the river spans would allow the box girders on the river crossings to be shallower than originally conceived. A reduction of box girder depth from 20 feet to 16 feet markedly reduced the superstructure weight which translates to a reduction in foundation requirements. These two changes result in lower cost and potentially shorter construction time while making the structure more slender and visually less dominate in the St. Croix River view shed.

In a separate analysis, the use of one box girder for the entire cross-section or using two separate box girders with perpendicular connecting elements called tension struts was also undertaken. After studying numerous 3-D models and illustrations prepared from the most likely viewing locations on and off the water the VQAC determined that both the one box (left) and two box (right) designs would be acceptable as no outstanding adverse visual consequences where observed with either design option. The two box girder option has been used to develop the preliminary bridge plans.

View of one box girder option View of two box girder option

Final Submittal 9

2.6 Main Span Box Configuration and Depth – One Box Girder Option

Typical Cross-Section

Final Submittal 10

2.6 Main Span Box Configuration and Depth – Two Box Girder Option

Typical Cross-Section


Final Submittal 11

3. 0 Pedestrian/Bike Trail

The original “outboard” schematic design for the bike/pedestrian trail located it outside the north cable line on a dedicated cantilevered structure. The November 2008 CRAVE study recommended that an “inboard” trail alternative (located inside the north cable line on a widened roadway girder) be evaluated for cost savings and operational and maintenance advantages.

Both the outboard and inboard trail alternatives were evaluated for constructability, safety, operations and maintenance, cost savings and visual characteristics. Both the inboard and outboard scenarios were modeled with 3-D illustration software and compared and contrasted. This analysis along with input from the VQAC concluded that the inboard trail concept provides superior safety, operations and maintenance characteristics and potentially lower cost. These include ease of construction, superior user safety, i.e. better supervision and access for law enforcement, emergency services, snow removal and other maintenance activities. The inboard trail concept has also been adopted for use on the NE ramp structure Mn/DOT Bridge 82047 which carries the trail from the river crossing back to grade on the Minnesota bank.

With the inboard configuration, pedestrian and bicycle movements are linear, affording trail users a clear sight line along the entire length of the bridge resulting in greater user safety. Night lighting of the path is more easily and efficiently accomplished as the roadway lighting systems are adequate to provide pedestrian lighting needs for most anticipated conditions. In times of higher trail use, and on the overlook platforms, supplemental lighting is easily accomplished with low level lighting fixtures located within the hand rail. The inboard trail concept separates users from the cable systems of the bridge yet still provides ample viewing of the structure and its’ components as well as views to the river beyond.

View looking west along inboard trail at north edge of bridge


Final Submittal 12

3. 0 Pedestrian/Bike Trail-continued

Additional considerations for the inboard trail design are:

The outer most railing along the north edge of the bridge and off-ramp structures be designed to protect pedestrian and bicycle trail users

• A barrier be placed to separate and protect pedestrian/bicycle users from vehicle traffic. • Designated rest /overlook platforms for trail users be provided outside of the flow of trail activity. • Separately controlled supplemental lighting be provided for safe night time use of the trail and

resting areas for likely use conditions.

To protect the pedestrian and bicyclist from leaving the bridge and off-ramp decks, an appropriate custom concept rail design has been developed for this project. The railing consists of two parts, the concrete parapet and the metal work; comprised of posts, infill panels and top hand rail.

3.1 Concrete Parapet /Railing Base

The concrete parapet /railing base has been designed to a specific height of 24 inches for two reasons.

• By establishing the height of the concrete base such that the height of the bottom rail of the infill panels is +- 27-1/2 inches above the path surface allows the use of uniform <6 inch openings in the infill panel and;

• The increased concrete base height will enhance the protection of the metal railing from impact damage from maintenance vehicles especially when snow removal is required.

The interior face of the base is plumb in the vertical axis while the top of the base is parallel to the bridge deck and slopes 1% toward the inside face of the bridge. The outer face of the base has a common arch to that of the metal work above.

Perspective of concrete parapet supporting pedestrian railing with design notations

NOTE:

The <6 inch grill work opening criteria is in force at the time of this writing. However, the grill work opening criteria must be verified and the design adjusted to the appropriate standard in force at the time of final design.


Final Submittal 13

3.2 Metal Railing Elements

The railing is supported two styles of cut plate steel posts, a minor (single) plate and major (double) plate with horizontal spacers. Both post types have base plates which are attached to the top of the concrete base with concrete anchors. The infill grill work is fabricated from square steel bar stock which has be rolled to the proper arc to match the outer edge of the cut steel supports. All of these components are finished in hot dipped galvanized coating after fabrication. The use of stainless steel for the railing and grill work was discussed but due to difficultly and cost to repair/replace elements it was not selected for this project. At approximately 12 foot on center, the major posts provide a location for the nesting of an LED light fixture. The spaces below the fixture and at the back side of the double post behind the fixture are closed off with stainless steel panels. The electrical connection for the lighting is provided to the fixture through a conduit located in the concrete base. Power is distributed to each fixture through the base at each major post. The stainless steel panel below the light fixture is removable providing access to an electrical work box at the base of each fixture. Atop the post a continuous ADA compatible tubular handrail will be attached along the length of the bridge. All fasteners on the handrail are stainless steel.

The outside arch of the metal post and infill grill work is common to the outside face of the concrete curb creating one continuous form from top of rail support to top of deck.

Perspective view of pedestrian railing and concrete parapet


Final Submittal 14

3.3 Pedestrian/Vehicle Protection Barrier

The inboard trail location (on the roadway box girder and west-bound off ramp) will necessitate the use of a pedestrian/vehicle protection barrier. In an effort to provide as open a view to the trail for safety and maintenance and to the river for the motorist as possible, a combination Mn/DOT standard tube railing (Type T-1) mounted on a Mn/DOT concrete parapet (Type P-2) has been chosen. Given the proximity of the barrier to the travel lanes it is intended that this railing be finished with the standard galvanized coating. This will likely result in lower maintenance cost and more timely repairs and replacement when needed.

Perspective view of pedestrian/vehicle protection barrier (left) and pedestrian railing (right).

Mn/DOT standards: tube railing (Type T-1) mounted on (Type P-2) concrete parapet.


Final Submittal 15

As the extradosed spans join to the approach transition span the exterior barrier rail will be modified from that of a type P-2 with metal tube rail T-1 to that of concrete barrier TL-4. A 20 foot long transitional segment will be introduced to make a smooth transition between the two rail types. The TL-4 rail with the concrete fill ( to create the arched exterior) will be used on the mainline and NE and SE ramps except along the pedestrian trail location.

Side view of railing in the area of transition. Sections through rail are illustrated below.

Section C - C Section A - A Section B – B

C

C

A

A B

B


Final Submittal 16

3.4 Overlook Platforms

As a result of the analysis conducted on the outboard trail system, it became clear that the original design did not provide dedicated resting or viewing spaces for trail users. In order to provide a safe resting area and capitalize on the views of the river valley from the bridge it was decided to include pedestrian overlook platforms at select piers. The proposed crescent overlook shape follows the organic theme of the columns. The platforms (plan view) extend in radial form out from the edge of the bridge deck surrounding the pier towers and (in section) are saucer shaped beneath the bridge deck as they join the cross girder below. The overlook platforms will provide a generous activity space for both day and night time use.

The overlook platforms are of a sufficient size to accommodate small groups of pedestrians with strollers and bicycles as well as permanent street furniture and interpretive kiosks/ placards should they be desired. The deck surface of the overlook platforms might also be finished with decorative materials. It was decided that the selection of theses elements should be determined as a part of the final design phase of the project. Trail users are protected along the north elevation of the bridge by a continuous railing (as described above). The rail extends continuously along the north elevation of the bridge and flows out around the edge of the overlook platforms providing unobstructed pedestrian access to the platforms while visually integrating the overlook platforms with the north edge of the bridge.

After evaluating several options for overlook placement, the preference of the VQAC was the placement of overlook platforms at Pier lines 9, 11, and 13; (a generally symmetrical arrangement) along the north face of the bridge. The location of the platforms provides a safe area for users to rest and view the engineering/ architectural elements of the bridge as well as have commanding views of the river valley to the north. They also provide for easier maintenance access to the cable housing between the columns.

Bridge layout plan indicating preferred locations for overlook platforms


Final Submittal 17

OUTER EDGE RADIUS 7’-6” TYPICAL

Section B-B View through Overlook Platform along centerline of Cross Girder and Pier (looking east) Section A-A Plan view of Overlook Platform


Final Submittal 18

Perspective of typical pedestrian overlook platform along north face of bridge.

View of underside of platform with smooth conical soffit


Final Submittal 19

3.5 Cable Connection Housing

As a part of the Visual Quality Refinement the detail by which the cable stays engage the bridge deck was evaluated. The original design included exposed cable brackets along the outside face of the deck. An alternative design was suggested in which the cable brackets are concealed behind a fascia panel. This results in the cable/deck attachment only being visible from beneath the bridge. The VQAC unanimously chose the covered cable alternative because it more clearly supported the linear form of the main bridge elements. This approach also provides some protection of the cable attachments from weather events and is anticipated to be more cost effective to construct.

Perspective view of north bridge elevation with fascia covering the outer face of the cable connection brackets.


Final Submittal 20

Close-up of fascia covering the cable connection brackets.

Along the top of the bridge deck the form of the cable connection pods was also studied and a preference was expressed by the VQAC for a tapered cylindrical form that transitions the cable and protective housing into the top of the deck.

Perspective of tapered cylindrical cable housing intersecting the top of bridge deck


Final Submittal 21

4.0 Night Lighting There are three types of lighting discussed during the Visual Quality Refinement and preliminary engineering phases of the project. The following summarizes the lighting strategy for roadway, pedestrian/trail and aesthetic lighting to be used on the project (Note: While aviation hazard and river level navigation lighting of the structures has been simulated in the illustrations the determination of fixture quantity, type and location will be completed during final design.)

4.1 Roadway Lighting The roadway will be lighted using pole mounted LED fixtures. The poles and arms will be standard Mn/DOT design with LED capable fixtures within Cobra Head style exteriors. The lighting will be located atop of the center vehicle barrier which will provide symmetrical lighting of the roadway as well as provide some lighting of the pedestrian/bike trail.

Driver’s eye view of roadway lighting a long river crossing - looking east

View of Roadway along river crossing from atop center median- looking east


Final Submittal 22

4.2 Pedestrian /Bike Trail Lighting

The lighting fixture types and pole heights proposed for the roadway will provide adequate lighting for most pedestrian/bicycling activity occurring on the inboard trail on the river crossing and NE ramp structures. The overlook platforms will be lighted by fixtures housed in the perimeter railing and if required recessed in the underside of the cable connection housing on the towers. In times of greater pedestrian and bicycle use levels, supplemental lighting of the trail may be required. The supplemental trail lighting will be accommodated through low level LED fixtures located within the pedestrian rail posts along the north face of the bridge structures. It is in intended that this supplemental lighting system be circuited and controlled such it can be turned off and on as needed based upon lighting conditions and user levels.

View of Pedestrian platform with night lighting.

View of night lighting along pedestrian trail, note supplemental lighting fixtures integrated into post forms along north elevation.


Final Submittal 23

4.3 Aesthetic Lighting

Although the original VQM did not discuss the aesthetic lighting concepts for the bridge in any detail it did recognize the concerns of stakeholders for the design to minimize the spillage of light into the adjacent river valley. As a part of contract No. 92530 the following lighting scenarios were studied.

1. No aesthetic lighting 2. Limited amount of accent lighting to accentuate tower columns and overlook platforms 3. Significant aesthetic lighting on all elements of the bridge.

Through presentations of the alternatives the VQAC expressed a preference for approach 2; a lighting scheme that would provide for the basic functional lighting and subtlety highlight the unique tower features of the structure without creating a significant amount of light spill to the sky, the river valley below or to adjacent residential properties.

To accomplish this, lighting fixtures are located between the column stems and positioned such that they direct light upward to gently wash the interior walls of the columns and underside of the overlook platform structures. The preferred lighting source is LED for its low operating cost, lower maintenance characteristics and ease of control and manipulation.

The support cables of the extradosed structure are lighted only from the roadway lighting. This provides an interesting contrast between the cable lines on the south side which are generally lighted verses the cable line on the north side which does not receive significant lighting. This effect is the result of the asymmetry of the roadway deck which is wider on the north to carry the trail. Since the light fixtures are located on the center of the roadway the light spreads evenly over the roadway but does not reach as far to the north line of cables. To further enhance this effect the cables will be covered with a white HDPE protective sleeve.

View of night lighting of river spans – looking south note cable definition on south side


Final Submittal 24

No aesthetic lighting is proposed for the approach spans or ramp structures. Lighting will be required beneath the mainline span 1 to light the roadway for TH 95 travelers. Lighting for this area will be determined as a part of the final design phase of the project.

View of typical river pier column with pedestrian overlook –looking south


Final Submittal 25

View of typical river pier without pedestrian overlook –looking south


Final Submittal 26

5.0 Minnesota Approach Structures

(MN/DOT Bridges 82045, 82047 & 82048)

The Minnesota approach includes the confluence of three structures; the continuation of the mainline structure Bridge 82045 merging with the NE Ramp Mn/DOT Bridge 82047 and the SE Ramp Mn/DOT Bridge 82048.

5.1 Box Girder Depth Transition The location of span 1 passing over the travel lanes of relocated TH 95 requires that adequate overhead clearance is maintained between the underside of span 1 and the TH 95 roadway surface. As in the original design a transition in girder depth will occur between Piers 1 and 2. The location of the girder depth transition begins from a 10 foot deep structure within Span 1 to the east of TH 95 and west of Pier 1 to the full 16 foot depth structure at Pier 2. This girder transition is similar to and follows the sloping ground beneath the approach spans. With the main river crossing spans and back spans of bridge 82045 reduced to 16 feet deep girders in place of the 20 foot deep girders in the VQM design, the transition to a box girder depth of 10 feet becomes less abrupt and visually superior.

Girder transition from 10’ to 16’depth between pier 1 and 2 along the mainline Minnesota approach


Final Submittal 27

5.2 Approach Spans/ NE,SE Ramp - Column Design After studying three column forms for the approach spans the preference of the VQAC was to use a single column which provides consistent visual character as desired by the intent of the VQM. The chosen approach column is similar in form to the river columns in that it is a tapered shaft with convex outer surfaces on the north-south axis and reveals along the east-west axis of the column. The reveals emulate the original twin stem concept of the VQM design. The mainline approach spans the NE, and SE ramps use a similar column form however each is adjusted to match the bottom flange width of the box girder and modified as necessary to accommodate special conditions such as bearing seat locations. (Piers 5R, 7W, 7E, 7R) In addition to providing acceptable visual quality, the chosen form performs well structurally and is expected to be more cost effective to construct. The solid form also reduces some security concerns voiced about the space between the stems with the original twin stem column design.

View of Minnesota approach (as viewed from the river)


Final Submittal 28

5.2 Approach Spans, NE and SE Ramp - Column Design

Elevation view of typical approach columns Side View Section Views


Final Submittal 29

5.2 Approach Spans, NE and SE Ramp - Column Design

Elevation view of column with bearing seat Side View Section Views

5.3 Minnesota Approach - Span Arrangement and Pier Placement


Final Submittal 30

Along with the box girder depth reduction and introduction of a single column pier, the span arrangement of the mainline and the two ramps has been refined to reduce wetland impacts, improve constructability, accommodate the reduced girder depth, and to better integrate the piers into the supporting landscape. Pier spacing for the mainline vary from 164-feet 6 inches at the span closet to the main spans to 195-feet at TH 95 with maximum pier spacing of 300-feet at interior spans. Pier spacing for Ramp NE varies from 195-feet to 245-feet, and pier spacing for Ramp SE varies from 125-feet to 199-feet. These pier spacing arrangements provide required horizontal clearances to roads and railway beneath the bridge, while minimizing wetland impacts. The two piers of the mainline are aligned transversely, and while the pier spacing for the ramps is not aligned with the mainline piers, the offset of the ramp piers from the mainline piers is sufficient to allow a more random arrangement of piers that is more in line with the varying landscape of the wooded wetland setting along the bridge alignment

Plan Layout of Mainline Approach and NE and SE Ramps


Final Submittal 31

5.4 Minnesota Approach Abutment

The Minnesota approach is supported on the west end by an abutment structure which incorporates a decorative stem wall. The functional goals of this element are to provide a continuous wrap of the abutment, beam seat and support the earth fill cone beyond. The visual goals are to create a single continuous form that surrounds the abutment, concealing the girder seat and smoothly transition from a tall structure back to finished grade.

To achieve these objectives, the abutment face is aligned perpendicular to the end of the approach spans. Beyond the limits of girders the abutment wall extensions curve back becoming generally parallel to the mainline centerline. The wall extensions are aligned along a smooth radius +- 35 feet as measured from the edge of pavement on both sides of the bridge approach. The face of the abutment wall is sloped back at a 1:33 ratio. The center line of the girder seat is recessed back from the receiving ledge of the abutment face approximately 4 feet so that the girder appears to be an extension of the wall thus visually unifying the two elements. The exposed surface of the wall is to be textured similar to a natural chiseled stone material with a dry stacked appearance. This will likely be achieved through the use of form liner materials. At this time the final textures for the form liner have not been determined.

5.5 MINNESOTA NE, AND SE RAMP STRUCTURES AND ABUTMENTS

View of Minnesota abutment looking south-west from north bound lanes of TH95


Final Submittal 32

The two ramp structures connecting to the Minnesota approach are constructed of similar shaped box girders with a depth of 10 feet. Each ramp has a girder depth transition from 10-foot to 16-foot depth in the span closest to the junction of the mainline box girders. This provides a consistent and smooth transition between the structures. The structures remain elevated on piers to straddle a number of land use conditions associated with the rail road, quarry activities, site access roadways and the preservation of wet land resources.

The NE and SE ramp structures touchdown near the east edge of relocated TH 95. The abutments proposed at these touchdown points are comprised of simple vertical stem walls with common wing walls which wrap the soil supporting the approach. The intent is to treat these abutments as the simple structures that they are. Given that they face away from TH 95 traffic and can only be seen from adjacent industrial sites they do not warrant extra ordinary treatment. To maintain a consistent palette it is recommended that these ramp abutments and wing walls be textured and finished similar to the primary Minnesota abutment.

6.0 Wisconsin Abutment

View of typical NE, and SE ramp abutment


Final Submittal 33

The main structure of the St. Croix River Crossing lands on the bluff on the Wisconsin side of the river supported by a simple vertical faced abutment. The abutment and relatively short wing walls which wrap the abutment do not present a major visual element which needs to be modified to any significant extent. The abutment is removed from the river a horizontal distance of over 550 feet and is over 120 feet higher in elevation than eye level at the river’s edge makes viewing of the abutment structure difficult at best. In addition, there are no public spaces beneath or adjacent to the Wisconsin abutment location so there will be no opportunity to approach the bridge in this location by the public. However, since there is at least one single family residence which will remain proximate to the abutment and to maintain consistency with the overall visual quality of the project it is recommended that the exposed faces of the abutment and wing walls receive a similar texture as is to be used on the Minnesota approach structures.

View of Wisconsin Abutment looking to the north east end of the bridge


Final Submittal 34

7.0 Structure Color

Throughout this addendum there are numerous images depicting the structures to be earth tone in color. This has been done only to maintain consistency with previous VQM documentation. It has been the intent of the design from its inception that a single color be applied to all exposed surfaces of the structures. The selection of a specific color for the project has not been advanced during contract No. 92530 as it was deemed appropriate to include this decision as a part of the final design phase of the project.

However, it was the preference of the VQAC that the protective cover (HDPE pipe) placed over the extradosed cables be white. The justification for this selection is as follows.

• It was felt that a striking color would bring more visual attention to the structure which was deemed undesirable.

• Colored covers will fade over time and it was felt that for this reason it may be more difficult to match in the future when repair or replacement is necessary.

• It was anticipated that white will hold up better as it is exposed to dirt and sunlight as it ages, and;

• The white cover will enhance the ability of the roadway lighting to highlight the cables achieving the aesthetic objectives for lighting mentioned above.

Likewise it was also determined that the metal railing elements of the bridge be treated with hot dipped galvanized coating to provide for corrosion protection and ease in replacement if and when damage occurs to various elements. No painting of the galvanized surface is desired as it was deemed to be an undesirable maintenance item.


Final Submittal 35

8.0 Anti-icing Facilities

The St. Croix River crossing will need to be operational year round and in all weather conditions. To that end it has been determined that an automated anti-icing system may be installed on the bridge. The delivery of anti-icing solution to the roadway surface will be through deck mounted spray nozzles which will be flush with the pavement surface and generally invisible to the motoring public. However, the support facilities which store the anti-icing solution and the pumping facilities will be of modest size and need to proximate to the bridge and visually harmonize with the structures and the surrounding environment.

The general site location has been selected and is illustrated on the following graphic. The anti-icing solution storage and pumping station is positioned south of the east bound on ramp on the Minnesota bank. Access to the building for maintenance and resupply is via the King Plant access road, and serviced along its east elevation. Entrance of materials and equipment is accomplished via a 10 foot x 10 foot metal roll-up door located on the south side of the building with additional access to the interior via a 3 foot wide metal service door located along the east elevation.

The following elevation drawings describe the exterior appearance of the building including surface textures and materials.

It is in intended that the roof and exterior walls will be finished with a weather resistance coating. The color of the finishes will be defined as a part of the final bridge design.

The building will be enclosed with a wire fence and include a 4’ wide swinging pedestrian gate and an 18’wide rolling gate along the east side of the building as generally indicated on page 37 below. The final fencing and gate locations will be determined in the final design phase of the project.

Conceptual Deicing Facility Site Plan

A. King Plant Access Road B. 12 Foot wide Gravel Drive C. Brine Storage and Pumping Building

C

B

A

D


Final Submittal 36


Final Submittal 37

Anti-Icing Fence Enclosure Plan

Documents

St. Croix River Crossing Project Visual Quality Manual ... · St. Croix River Crossing Project Visual Quality Manual Addendum Final Submission PREPARED FOR: MINNESOTA DEPARTMENT OF