over the south fork of the root river houston county the south fork of the root river . houston...

Historic Bridge Management Plan

Inspection and Maintenance Plan Update

MnDOT Bridge No. 6679

Over the South Fork of the Root River Houston County

Report prepared for

Minnesota Department of Transportation

Report Prepared by

Greg Mathis,

Project Historian

and

Craig Lenz,

Project Engineer

January 2014

Minnesota Department of Transportation Historic Bridge Management Plan Bridge No. 6679

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Table of Contents

1.0 INTRODUCTION .............................................................................................................................. 1

2.0 RECOMMENDED INSPECTIONS FOLLOWING THE 2012-2013 REHABILITATION ................. 6

3.0 RECOMMENDED MAINTENANCE ACTIVITIES FOLLOWING THE 2012-2013 REHABILITATION ........................................................................................................................... 8

4.0 PROJECTED COSTS FOR MAINTENANCE ............................................................................... 10

APPENDIX A: COST DETAILS

APPENDIX B: CONCRETE STAIN REPAIR AND APPLICATION PROCEDURES


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1.0 Introduction

In July 2012, the Minnesota Department of Transportation (MnDOT) let a contract for the rehabilitation of Bridge No. 6679. The rehabilitation was based on recommendations for the bridge contained within the historic bridge management plan (HBMP) prepared by Mead & Hunt and HNTB on behalf of MnDOT in June 2006, and in accordance with Secretary of the Interior’s Standards for the Treatment of Historic Properties and the National Park Service’s Preservation Brief 15: Preservation of Historic Concrete. Construction documents were prepared by the MnDOT Bridge Office with technical assistance from The 106 Group Ltd. (106 Group) on matters related to historic preservation. Construction began in July 2012, concrete work was finished in October 2013, and the project was completed in June 2013.

The following Inspection and Maintenance Plan (IMP) is based on the 2012 rehabilitation and supersedes the inspection and maintenance plans, schedules, and cost estimates included in the 2006 HBMP. The purpose of the IMP is to serve as a guide on how to properly inspect and maintain the rehabilitated bridge to ensure its long-term preservation. The recommendations contained within this plan are based on MnDOT’s Bridge Inspection Field Manual, Version 1.9, MnDOT Engineering Services Division Technical Memorandum No. 11-06-B-03, the Secretary of the Interior’s Standards for the Treatment of Historic Properties, and the Management Plan for Historic Bridges in Minnesota.

Background

Historic Bridges in Minnesota

In 2006, MnDOT completed a statewide inventory and evaluation of bridges in Minnesota constructed before 1956, which resulted in the development of a list of pre-1956 bridges owned by MnDOT and local governments that were eligible for the National Register of Historic Places (NRHP). Bridge No. 6679 was one of the bridges determined eligible for the NRHP as part of this survey. In June of that year, a statewide HBMP was prepared and individual management plans were completed for 23 of 24 state-owned bridges selected for preservation.

In 2008, the Federal Highway Administration (FHWA); the Advisory Council on Historic Preservation (ACHP); the Department of the Army, Corps of Engineers, St. Paul District (Corps); the Minnesota State Historic Preservation Office (SHPO); and MnDOT entered into a programmatic agreement (PA) concerning pre-1956 historic bridges in Minnesota. Among the stipulations of this agreement, NRHP nominations were required to be prepared for all National Register eligible state-owned pre-1956 bridges. The PA also stipulated the preservation of the 24 pre-1956 bridges identified for preservation in 2006 in accordance with the Secretary of the Interior’s Standards for the Treatment of Historic Properties.

Bridge No. 6679

Bridge No. 6679 was built in 1949 to carry the vehicular traffic of Trunk Highway 76 over the South Fork of the Root River southeast of the city of Houston in Houston County. It has an overall structure length of 300 feet and an out-out width of 34.7 feet. The bridge has a continuous/cantilevered, steel-beam design with three main spans, including two 80-foot end spans and a 100-foot center span.

As part of the statewide survey of pre-1956 bridges conducted by MnDOT in 2006, Bridge No. 6679 was evaluated and determined to be eligible for the NRHP under Criterion C, in the area of engineering. The


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bridge is significant for its 36-inch rolled I-beams, in their continuous and cantilevered construction with pinned connections that allowed for a main span of 100 feet, which was the at the outer limits of the steel technology of the time. The bridge is also significant for its early use of a Modernist bi-rail design for the reinforced-concrete railing. Reflecting the significance of its design, and pursuant to the 2008 PA, Bridge No. 6679 was placed on the NRHP on July 20, 2011.

Since Bridge No. 6679 was determined to be eligible for the NRHP in 2006, it was one of the 23 individual bridges for which a HBMP was prepared in 2006. The HBMP prepared for Bridge No. 6679 in June 2006 assessed the condition of the bridge:

The concrete approach spans have marginal load capacity. The bridge deck has narrow shoulders and substandard railings. The original bridge railing is deteriorated and has been repaired in several locations. Aside from localized deterioration at the superstructure hinge locations, the rolled beams with intermittently welded cover plates are in good condition. The voids incorporated into the abutment design appear to be contributing to the settlement issues at the ends of the bridge. The river has migrated north from Span 2 to Span 3 leaving large silt deposits that are blocking the hydraulic opening in Spans 1 and 2.

Based on an assessment of the overall conditions of Bridge No. 6697, the HBMP recommended that the bridge be “rehabilitated based on the Secretary of the Interior’s Standards for Rehabilitation (Standards) [36 CFR Part 67] and Guidelines for Bridge Maintenance and Rehabilitation Based on the Secretary of the Interior’s Standards (Guidelines)” for continued vehicular use on-site. The HBMP also recommended a number of stabilization and preservation activities. Pursuant to the preservation recommendations in the HBMP, the bridge abutment slab spans were replaced in 2006 and the steel superstructure was zone painted in 2010. 2012-2013 Rehabilitation

Pursuant to the HBMP and the Secretary of the Interior’s Standards for the Treatment of Historic Properties, MnDOT completed a rehabilitation of Bridge No, 6679 in 2012-2013. All structural work was completed in October 2012 and the project was completed in June 2013 (see images of the completed rehabilitation at the end of this section). The rehabilitation included:

1. Replacing the expansion joints at both hinges and abutments.

2. Replacing the bearings at both abutments.

3. Testing and repair of the top flange cover plate welds.

4. Reconstructing the deck with an integral wearing course.

5. Reconstructing the railing to meet TL-3 standards, in accordance with the Secretary of the Interior’s Standards to replicate the general design, color, texture, materials, and feeling of the original railing.

6. Replacing the deteriorated upper portions of abutment wingwalls.


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7. Cutting access door openings into downstream side of the abutment wingwalls.

8. Installing a geotextile filter and riprap on the slope in front of the north abutments.

9. Salvaging and reinstalling existing bridge nameplates on the new railings.

10. Installing new endpost “additions” with sloped tops at the outer ends of the reconstructed endposts to meet NCHRP Report 350 requirements.

11. Installing a new bridge nameplate with the rehabilitation date on the newly constructed endpost “additions.”

12. Staining the new concrete, including the reconstructed railing, deck fascia, and upper portions of the abutment wingwalls to blend the new concrete with the remaining original concrete on the abutment wingwalls.

13. Applying a standard MnDOT vapor permeable, clear, matte finish anti-graffiti protective coat over the stain on the new concrete (railing, deck fascia, and upper portions of abutment wingwalls).

14. Crack sealing the deck on the approach spans.


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2.0 Recommended Inspections Following the 2012-2013 Rehabilitation

The rehabilitation of Bridge No. 6679 was completed in June 2013. Post rehabilitation, the following inspections should be performed to monitor the condition of Bridge No. 6679 starting in 2013. Inspections shall be performed in accordance with current MnDOT requirements found in this plan and the most recent version of the Bridge Inspection Field Manual.

Who Should Conduct the Inspections?

Prior to conducting the inspection, the Bridge Inspection Team Leader (BITL) shall review the 2006 HBMP and this update to become familiar with the significance of the bridge and its character defining features. After completing the inspection, and prior to preparing the inspection report, if the inspector noted any issues that pertain to the historic features on the bridge, the inspector will consult with the MnDOT Cultural Resources Unit (CRU). The goal of this consultation shall be to ensure that the issues identified during the inspection that may affect the long-term preservation of the structure and its historically significant features are given proper consideration in the inspection report.

Inspections

The following schedule should begin based on a substantial project completion date of October 2012.

Routine:

1. Conduct routine inspections every 24 months in accordance with MnDOT standards as described in the most current versions of Bridge Inspection Field Manual. Perform any recommended maintenance activities identified as part of the routine inspection within a 12-month period.

2. Conduct special inspection of hinge pins with MnDOT standards at 4-year intervals. Conduct maintenance and repair activities identified as part of the special inspection within 24 months.

3. If underwater elements of the bridge cannot be visibly evaluated during periods of low flow or by feel for condition, integrity and safe load capacity, due to excessive water depth and turbidity, conduct an underwater inspection in accordance with MnDOT standards at 5-year intervals. Implement resulting recommended maintenance or repair efforts within a 24-month period.

Special:

1. Inspect piers and abutments for scour damage after flood events.

2. As the 2012-2013 rehabilitation addressed all major structural issues, no special inspections are anticipated. However, should any develop during the current life cycle, monitor fatigue hot spots during routine and in-depth inspections as indicated by fatigue life assessment.

3. In the event that a critical deficiency or hazardous deficiency is discovered during an inspection, the Bridge Inspector shall immediately notify the MnDOT Inspection Engineer. Upon receiving notification, the MnDOT Inspection Engineer shall consult with the MnDOT Cultural Resources Unit as part of their effort to prepare a strategy for corrective action to resolve the deficiency.


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4. During the 2012-2013 rehabilitation curing compound was applied to the curb. Since the curb was

not blasted to remove the curing compound prior to application of stain and anti-graffiti coat, the finishing system may potentially delaminated from the concrete. Inspect the curb as part of routine inspections to determine if cure compound and finishing system (stain and anti-graffiti coats) are still adhered to the concrete. If not, restain the curb to match deck fascia and rail, and then apply an anti-graffiti coating over the stain per the application procedures described in Appendix B.


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3.0 Recommended Maintenance Activities Following the 2012-2013 Rehabilitation

Subsequent to the rehabilitation completed in June 2013, the following maintenance activities should be performed on Bridge No, 6679, with 2013 being year one:

Annually

1. Power wash the railings, fascia beams, abutments, wing walls, and piers with water, preferably in the spring.

2. Power wash and flush the deck and expansion joints, preferably in the spring.

3. Clean the drainage system of debris.

4. Remove any soil and vegetation accumulated in concrete joints and cracks.

5. Clean the bridge seats.

6. Perform any recommended maintenance activities identified as part of the annual inspection within a 12-month period.

Every Five Years

1. Reset and lubricate the bearings with a petroleum product.

2. Lubricate the superstructure hinges with a petroleum product.

3. Spot paint the steel superstructure following standard MnDOT procedures when the paint system begins to fail.

4. Seal any cracks in the historic original concrete by injection with a two component epoxy resin or caulk, that when cured has a matte finish and matches the color of the concrete.

5. Spot stain previously stained concrete on the reconstructed upper portions of abutment wingwalls curb, deck fascia, and railing in accordance with Appendix B.

a. After stain has dried, apply standard MnDOT vapor permeable, clear, matte finish anti-graffiti coat over stain per Appendix B.

b. No stain or anti-graffiti coat shall be applied to unstained original concrete.

6. Seal or patch cracks in wearing course.

Every 10 Years

1. Spot paint steel deck drains following standard MnDOT procedures.


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Every 20 Years

1. Replace expansion joints.

Every 25 Years

1. Remove and replace wearing course

Every 30 years

1. Clean, reprime and repaint the steel superstructure in accordance with standard MnDOT procedures.

2. Clean and restain previously stained concrete on the reconstructed upper portions of abutment wingwalls curb, deck fascia per Appendix B.

a. After stain has dried, apply standard MnDOT vapor permeable, clear, matte finish anti-graffiti coat over stain in accordance with Appendix B.

a. No stain or anti-graffiti coat shall be applied to unstained original concrete.

3. Clean, reprime and repaint the steel deck drains in accordance with standard MnDOT procedures.

Every 50 years

1. Repair the deck.

Specialized Maintenance

1. Stream stabilization to account for shifting stream alignment and mitigate degradation of stream bed.

2. Debris removal, erosion repair and protection, and clean up due to flood events. Assume a 5-year cycle.

3. Remove graffiti.

4. If curing compound applied to curb during the 2012-2013 rehabilitation fails, clean curb and apply three-part finishing system in accordance with Appendix B.

5. Replace neoprene strip seal glands if damaged.

6. Repair scour damage to substructure units.

7. Patch spalled areas of concrete and apply three-part finishing system in accordance with Appendix B.

8. Straighten deformed steel members.


4.0 Projected Costs for Maintenance

Appendix A presents the maintenance schedule for Bridge No. 6679. The schedule includes activities and costs associated with maintenance activities.


Appendix A: Cost Details


Appendix A-1

MnDOT Maintenance Schedule for Bridge No. 6679 Bridge No. 6679 Maintenance Activity Listing and Costs – January 2014

Notes: 1. Costs are presented in 2014 dollars. 2. Unit costs are presented to the dollar or cent depending on the precision of the specific value.

COST SUMMARY: ANNUALIZED MAINTENANCE

REF. No. ITEM ANNUAL

COSTS

1 INSPECTIONS $1,350

2 SUPERSTRUCTURE $6,260

3 SUBSTRUCTURE $7,935

4 RAILINGS $1,170

5 DECK $3,926

TOTAL $20,641

1.00 INSPECTIONS

REF. No. ITEM / DESCRIPTION OF WORK

EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

5.05 Routine inspection 2 Each 1 $850 $850 $425

5.10 Arm’s length inspection 4 Each 1 $1,700 $1,700 $425

5.15 Underwater inspection 5 LS 1 $2,500 $2,500 $500

TOTAL $5,050 $1,350

2.00 SUPERSTRUCTURE


EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

1.05 Flush fascia beams with water 1 SF 600 $0.33 $200 $200

1.10 Reset and lubricate bearings 5 Each 6 $800 $4,800 $960

1.15 Lubricate hinges 5 Each 12 $500 $6,000 $1,200

1.20 Spot paint steel 5 SF 1,500 $13 $19,500 $3,900

TOTAL $30,500 $6,260


Appendix A-2

3.00 SUBSTRUCTURE REF.

No. ITEM / DESCRIPTION OF WORK EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

2.05 Flush substructure with water 1 SF 16,253 $0.33 $5,400 $5,400

2.10 Clean bridge seats 1 Each 24 $50 $1,200 $1,200

2.15 Debris removal and clean up due to floods 5 LS 1 $2,500 $2,500 $500

2.20 Erosion repair and protection 5 LS 1 $2,500 $2,500 $500

2.25 Spot stain previously stained concrete on abutments and wingwalls 5 SF 50 $3.50 $175 $35

2.30 Seal cracks in concrete 5 Gallon 2 $750 $1,500 $300

TOTAL $13,275 $7,935

4.00 RAILINGS


EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

3.05 Flush railings with water 1 LF 600 $0.75 $450 $450

3.10 Seal cracks in concrete 5 Gallon 2 $750 $1,500 $300

3.15 Spot stain previously stained concrete 5 SF 600 $3.50 $2,100 $420

TOTAL $4,050 $1,170

5.00 DECK


EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

4.05 Flush deck with water 1 LS 1 $1,050 $1,050 $1,050

4.10 Clean drainage system of debris 1 LS 1 $425 $425 $425

4.15 Seal/patch cracks in wearing course 5 LF 3000 $3.00 $9,000 $1,800

4.20 Spot stain previously stained curb and deck fascia 5 SF 830 $3.50 $2,905 $581

4.25 Spot paint steel deck drains 10 LS 1 $700 $700 $70

TOTAL $14,080 $3,926


Appendix A-3

COST SUMMARY: LONG-TERM MAJOR MAINTENANCE BY BRIDGE CREWS OR CONTRACTORS

REF. No. ITEM TOTAL

COSTS ANNUALIZED

COSTS

6 SUPERSTRUCTURE $231,036 $8,301

7 SUBSTRUCTURE $5,250 $175

8 RAILINGS $19,950 $665

9 DECK $123,036 $4,101

10 OTHER $99,000 $3,300

TOTAL $478,272 $16,542

6.00 SUPERSTRUCTURE


EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

6.05 Replace expansion joint glands 20 LF 180 $200 $36,000 $1,800

6.10 Complete repainting of steel 30 SF 16,253 $12 $195,036 $6,501

TOTAL $231,036 $8,301

7.00 SUBSTRUCTURE


EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

7.05 Complete restaining of previously stained concrete on abutments and wingwalls

30 SF 1,500 $3.50 $5,250 $175

TOTAL $5,250 $175

8.00 RAILINGS REF.


(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

8.05 Complete restaining of previously stained concrete 30 SF 5,700 $3.50 $19,950 $665

TOTAL $19,950 $665


Appendix A-4

9.00 DECK REF.


(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

9.05 Complete replace wearing course 30 SF 9,418 $11.15 $105,011 $3,500

9.10 Complete restaining of previously stained concrete curb and deck fascia 30 SF 4,150 $3.50 $14,525 $484

9.15 Complete repainting of steel deck drains 30 LS 1 $3,500 $3,500 $117

TOTAL $123,036 $4,101

10.00 OTHER


EXPECTED LIFE CYCLE

(YEARS) ITEM QTY

QTY UNIT

UNIT COST

ITEM TOTAL

ANNUAL COST

10.05 Stream stabilization 30 LS 1 $99,000 $99,000 $3,300

TOTAL $99,000 $3,300


Appendix B: Concrete Stain Repair and Application Procedures


Appendix B-1

Concrete Stain Repair and Application Procedures

As part of the 2012-2013 rehabilitation, a three-part finishing system was applied to the surfaces of newly placed concrete that replicated historic features on the bridge, including the upper portions of the abutment wingwalls, the deck fascia, curb, and railing. The purpose of the finishing system was to blend the aesthetic appearance of the new concrete with the remaining historic concrete in terms of color and weathering. The finishing system utilized MnDOT approved standard materials; however, the finishing system was applied using a customized, non-MnDOT standard process to achieve the desired aesthetic effect.

The finishing system included the application of two very light coats (base coat and overspray coat) of a thinned, vapor permeable water-based, matte-finish acrylic stain using a high-pressure spray gun. In order to blend the color and appearance of the new concrete with the remaining original concrete, different colors and coverage rates were used. The third part was a standard MnDOT vapor permeable anti-graffiti coat with a matte-finish that is intended to protect the stain, reducing the need for periodic maintenance of the stain. A two-part finishing system was applied to the endpost “additions.” This system included the application of a vapor permeable water-based, matte-finish acrylic stain base coat and a top coat of a standard MnDOT vapor permeable anti-graffiti coat with a matte-finish. Both were applied at 100% coverage. The purpose of the different treatment for the endpost “additions” was to meet the Secretary of the Interior’s Standards by differentiating these new features from the historic features of the bridge.

The following products were used for the finishing system and should be used to repair the finishing system:

• Stain: H&C Concrete Stain: Solid Color Water Based (matte-finish) o Replicated historic concrete features (upper portions of the abutment wingwalls, deck

fascia, curb, and railing) Base coat color: Bombay Overspray color: Sandstone

o Endpost “additions” Base coat color: Gray

• Anti-Graffiti Coat: TK Products TK-Permaclean: Anti-Graffiti Coating (clear, matte-finish)

Prior to application, all stain was thinned approximately 5% in order to reduce its opacity and improve absorption by the concrete, thereby reducing the potential for a “painted concrete” effect. On all new concrete that replicated historically significance features, the base coat was applied at a coverage rate that varied between 80%-95%. The second, overspray coat was applied at a coverage rate that varied between 10%-25%. The total coverage rate for both coats combined, on average, varied between 80%-100% on the reconstructed upper portions of the abutment wingwalls, 85% -95% on the deck fascia and railing, and 75%-90% on the curb.

Repairing the Concrete Stain

The following procedures only apply to areas that were stained as part of the 2012-2013 rehabilitation (reconstructed upper portions of the abutment wingwalls, deck fascia, curb, and railing). Original concrete comprising the abutments that were coated with a standard special surface finish in 2006 shall also be stained in accordance with the following procedures in the event the existing special surface finish is in


Appendix B-2

need of repair. However, original uncoated concrete shall never be stained. An anti-graffiti coat should also not be applied to uncoated original concrete.

If the stain on the new concrete is damaged, or needs repair due to age, utilize the following process to repair the finishing system:

• If needed, repair concrete. • Power wash area to be restained with water at 5,000 PSI to remove contaminants and any loose

stain, and allow concrete to dry. • If the repairs include the endposts or endpost “additions,” cover bridge nameplates prior to

staining. • Reconstructed upper portions of the abutment wingwalls, deck fascia, curb, and railing:

o Thin stain approximately 5%-10% percent with clean water (19:1 to 9:1 ratio of stain to water).

o After concrete is dry, use a high-pressure spray gun to apply a very light base coat of thinned Bobay colored stain.

Apply stain using a vertical motion (horizontal application not permitted except for on the underside of rails).

Apply stain at a somewhat irregular coverage rate, ranging between 75%-90%. Initially, apply at a 70%-80% coverage rate, lightly applying additional stain as needed after the initial application to blend repaired area with adjacent concrete.

Allow stain to dry per manufacturer’s recommendations. o Use a high-pressure spray gun to apply an extremely light overspray coat of thinned

Sandstone colored stain. Apply stain using a vertical motion (horizontal application not permitted except for

on the underside of rails) Apply stain at a somewhat irregular coverage rate, ranging between 10%-25%.

The overspray coat should be no more than a light mist and should not result in any solid coverage of the concrete. If needed, apply very light accent streaks to replicate weathering patterns found on the original concrete and to blend the repair with adjacent concrete.

Allow stain to dry per manufacturer’s recommendations. o Use a high-pressure spray gun to apply a clear, matte finish anti-graffiti coat. Coat shall

be applied at 100% coverage rate in accordance with the manufacturer’s recommendations. Care shall be taken to not exceed the recommended coverage rate.

• Endpost “additions” o After concrete is dry, mask and cover adjacent reconstructed original endpost and deck

fascia to prevent accidental coverage and to maintain a clean, crisp vertical line between the historic endpost and the endpost “addition.”

o Use a high-pressure spray gun to apply a coat of Gray colored stain. Apply stain using a vertical motion. Apply stain to achieve 100% coverage, in accordance with the manufacturer’s

recommendations for coverage rate. Allow stain to dry per manufacturer’s recommendations.


Appendix B-3

o Use a high-pressure spray gun to apply a clear, matte finish anti-graffiti coat. Coat shall be applied at 100% coverage rate per manufacturer’s recommendations. Care shall be taken to not exceed the recommended coverage rate.

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