Minnesota Department of Transportation (MnDOT) Local Historic Bridge Report

Transcription

1 Executive Summary Bridge carries two-way traffic on Chicago Avenue South over Minnehaha Creek. It is owned by the City of Minneapolis. The bridge was designed by R. Fredrickson for the City of Minneapolis and constructed in It is significant as an example of the earliest period of use of post-tensioned concrete slab design and construction in Minnesota. The bridge is a noncontributing resource to the determined-eligible Grand Rounds Historic District. Bridge is a post-tensioned concrete slab span bridge spanning approximately 51 feet. The slab, abutments, wingwalls and interior bridge railings are comprised of cast-in-place reinforced concrete. The exterior railings are metal and there are two lights built into each exterior railing. The railing height was extended in 1987 to 4 feet 6 inches. The bridge carries a 52-foot-wide roadway and two pedestrian sidewalks. There is a 10-foot-wide trail under the bridge that is located along the south abutment. Bridge is in fair condition and appears to adequately serve its purpose of carrying vehicular and pedestrian traffic. The major defects of the bridge include cracking and spalling of the deck slab, deterioration of the metal railing and spalling of the underside of the sidewalk overhang. With proper maintenance, stabilization and preservation activities it is believed Bridge could continue to serve in its present capacity for 20 years or longer. Any work on Bridge should proceed according to the Secretary of the Interior s Standards for the Treatment of Historic Properties (Standards) [36 CFR part 67] and The Secretary s Standards with Regard to Repair, Rehabilitation, and Replacement Situations, as adapted by the Virginia Transportation Research Council (Guidelines). JULY 2014

2 Bridge Location BR. NO Bridge CHICAGO AVE S over MINNEHAHA CREEK PROJECT LOCATION HENNEPIN COUNTY SEC. 14, TO 028NN, R 24W UTM ZONE: 15 NAD: 27 USGS QUAD NAME: MINNEAPOLIS SOUTH EASTING: ft. NORTHING: ft. JULY 2014 Bridge Location

3 Table of Contents Executive Summary Bridge Location I. Project Introduction II. Historic Data III. Bridge Data IV. Existing Conditions/Recommendations V. Projected Costs Appendices A. Glossary B. Guidelines for Bridge Maintenance and Rehabilitation based on the Secretary of the Interior s Standards C. Documents JULY 2014 Table of Contents - i

4 I Project Introduction This Bridge Report is a product of a comprehensive study performed for approximately 140 historic bridges owned by county, city, township, private and other state agencies besides MnDOT. The study is the second phase of a multi-phased process developed and executed in partnership with representatives from the Federal Highway Administration (FHWA); State Historic Preservation Office (SHPO); MnDOT State Aid; MnDOT Cultural Resources Unit (CRU); the US Army Corps of Engineers (USACE); local public works and county highway departments; county and township boards and city councils; the preservation community and the general public. To perform the study, MnDOT retained the consultant team of LHB Inc., Mead & Hunt Inc., and The 106 Group. The general goals of the study include: Gathering and compiling the existing historic and bridge condition data and other relevant information on the bridges in the study group into bridge reports. National Register nominations for a select number of bridges within the study group which the bridge owner may request a nomination to be prepared. Updating MnDOT s Management Plan for Historic Bridges in Minnesota based on the study s findings. Producing a narrative for the MnDOT Historic Bridge Website to disseminate information regarding locally owned historic bridges in Minnesota. Investigating and preparing a summary regarding how other states have funded historic bridge programs and structured Programmatic Agreements when multiple non-state entities are the owners of historic bridges. The Bridge Reports compile and summarize the historic and engineering information concerning the structures. It is important to note that this report indicates if a bridge is located within a known historic district, but it does not identify all known or potential historic properties. Potential impacts to adjacent or surrounding historic properties, such as archaeological sites or other structures must be considered. Contact MnDOT CRU early in the project planning process in order to identify other potential historic properties. The reports also document the existing use and condition of the bridges along with assessments of the maintenance, stabilization and preservation needs of each structure, including cost estimates. The maintenance activities, along with regular structural inspections and anticipated bridge component replacement activities are routine practices directed toward continued structure serviceability. Stabilization activities address immediate needs identified as necessary to maintain a bridge s structural and historic integrity and serviceability. Preservation activities are near term or long term steps that need to be taken to preserve and in some cases restore a bridge s structural and historic integrity and serviceability. In assessing preservation activities, a design life of 20 years or longer is typically considered. In addition to general restoration activities and dependent on the severity of deterioration, preservation activities may include spot repair, disassembly and reassembly or replacement of specific bridge components. Recommendations within the Bridge Reports are consistent with the Secretary of the Interior s Standards for the Treatment of Historic Properties (Standards). The Standards are basic principles created to help preserve the distinct character of a historic property and its site, while allowing for reasonable change to meet new engineering standards and codes. The Standards recommend repairing, rather than replacing JULY 2014 Project Introduction I - 1

5 I Project Introduction deteriorated features whenever possible. The Standards apply to historic properties of all periods, styles, types, materials and sizes and encompass the property s location and surrounding environment. The Standards were developed with historic buildings in mind and cannot be easily applied to historic bridges. The Virginia Transportation Research Council (Council) adapted the Standards to address the special requirements of historic bridges. They were published in the Council s 2001 Final Report: A Management Plan for Historic Bridges in Virginia, The Secretary s Standards with Regard to Repair, Rehabilitation, and Replacement Situations, provide useful direction for undertaking maintenance, repair, rehabilitation, and replacement of historic bridges and are included in the Appendix to this plan. Existing bridge data sources typically available for Minnesota bridges were gathered for the study. These sources include: PONTIS, a bridge management system formerly used by MnDOT to manage its inventory of bridges statewide, and its replacement system, SIMS (Structure Information Management System) The current MnDOT Structure Inventory Report and MnDOT Bridge Inspection Report. Reports are available for the majority of the bridges (not available for bridges in private ownership) Database and inventory forms resulting from the 2012 Minnesota Local Historic Bridge Study and other prior historic bridge studies as incorporated into the database Existing Minnesota historic contexts studies for bridges in Minnesota, including Reinforced- Concrete Highway Bridges in Minnesota, , Minnesota Masonry-Arch Highway Bridges, , Iron and Steel Bridges in Minnesota, and Minnesota Bridges Field investigations documenting the general structural condition and determining characterdefining features Additional data sources researched and gathered for some of the bridges as available also included: Files and records at MnDOT offices Original bridge construction plans, rehabilitation plans, and maintenance records of local owners Files and documents available at the SHPO office, including previous inventory forms, determinations of eligibility, studies, and compliance documents Existing historical and documentary material related to the National Register-eligible bridges The Appendix contains the following: a Glossary explaining structural and historic preservation terms used in the report, the Guidelines for Bridge Maintenance and Rehabilitation based on the Secretary of the Interior s Standards, a list of engineering and historic documents available for this bridge, and copies of the MnDOT Structure Inventory and Bridge Inspection Reports current at the time of the report preparation. The Bridge Report will provide the bridge owner and other interested parties with a comprehensive summary of the bridge condition and detailed information related to the historic nature of the bridge. This information will enable historic bridge owners to make informed decisions when planning for their historic properties. JULY 2014 Project Introduction I - 2

6 II Historic Data This narrative is drawn from previous documents, as available for the subject bridge, which may include determination of eligibility (also known as Phase II evaluation), Minnesota Architecture/History Inventory Form, National Register nomination, Multiple Property Documentation Form, and/or applicable historic contexts. See Sources for details on which documents were used in compiling this Historic Data section. Contractor Designer/Engineer Unknown R. Frederickson Description Bridge carries two-way traffic on Chicago Avenue South over Minnehaha Creek. Mature trees line the banks of Minnehaha Creek, and a walking path runs underneath the bridge along the creek. There are residential areas north and south of the bridge off Chicago Avenue South. Bridge 27547, built in 1970, is a post-tensioned concrete slab bridge. It has a span length of 51 feet, deck width of 67 feet, roadway width of 52 feet, and a skew of 11 degrees. Original concrete barriers line the roadway and separate the 6-foot-wide pedestrian sidewalk from vehicular traffic. The barriers have decorative angled end posts featuring a simple geometric design but are otherwise unadorned. A bridge plaque on the southwest end post reads City of/ Minneapolis/ Bridge 27547/ A metal railing lines the sidewalks. At an unknown time, the original 3-foot-tall metal picket railing was extended an additional 18-inch rail above to meet needed railing height. There are two classical revival lamp posts on either side of the bridge along the railing. The light poles are original, though it is unclear if the fixtures have been replaced. The bridge deck is supported by flared, corrugated concrete abutments. The abutments feature vertical incised lines in the concrete. There are retaining walls adjacent to the south side of the bridge at the east and west corners. Grouted rip rap lines the slope along the east and west sides of the north abutment. A paved concrete trail runs underneath the south side of the bridge with a metal railing along the north side of the path. The only change to the bridge is the addition to the metal railing along the sidewalks in Significance Bridge was designed by R. Fredrickson for the City of Minneapolis Public Works Department in The director of public works approved the plans for a post-tensioned concrete bridge to span Minnehaha Creek, adjacent to Minnehaha Parkway, in May of The bridge was constructed in the same year by the city of Minneapolis using state funds. It replaced a previous bridge at the same location, adding sidewalks over Minnehaha Creek and improving the path running along the creek underneath the bridge. Prestressed concrete was first used by the Minnesota Highway Department (MHD) in 1957, a year after the beginning of the Interstate highway program. In the next 13 years, the MHD constructed over 700 prestressed concrete structures on both Interstate and non-interstate routes. The Interstate s need for bridges prompted the construction of specialized facilities to manufacture prestressed concrete beams, JULY 2014 Historic Data II - 3

7 II Historic Data an undertaking that required substantial investment. Prestressed concrete quickly emerged as an important material for Interstate and non-interstate bridges. Prestressed concrete is superficially similar to reinforced concrete in that both employ longitudinal steel elements within a beam of concrete. As T.Y. Lin explained, the steel is pre-elongated so as to avoid excessive lengthening under service load, while the concrete is pre-compressed so as to prevent cracks under tensile stress. Thus an ideal combination of the two materials is achieved. In addition to steel pretensioning, the major difference between reinforced concrete and prestressed concrete, according to Lin, is the latter s use of higher-strength materials, including high-tensile steel and high-strength concrete. Because of the use of high-strength materials, prestressed concrete requires a smaller quantity of steel and concrete to carry the same loads as reinforced concrete and results in more efficient use of materials. Post-tensioned concrete, one form of prestressing (the other, and more commonly used method in Minnesota, is pre-tensioning), refers to the compressing of concrete in a structural member by inserting the steel strand through open recesses or along the outside of the formed concrete member, stretching it, and attaching it with a permanent anchor to maintain stress. Unlike pre-tensioned systems that must be fabricated at a precasting plant, post-tensioned systems can be fabricated at the project site. This is beneficial when it is not cost-effective to transport heavy beams from the precasting plant to the job site. Additionally, it is easier to construct continuous structures with post-tensioned concrete because pretensioned members can only be made as precast units. Pre-tensioned beams are limited straight or circular members with straight, harped, or circular reinforcement tendons. Post-tensioned reinforcement tendons can be configured into almost any shape, which allows greater flexibility to match needed design requirements. Though beams and girders were post-tensioned in the 1950s and 60s, the post-tensioned slab is an innovation in prestressed concrete bridge design which did not develop nationally until the 1970s. Bridge is located within the Minnehaha Parkway park system, which is one part of the City of Minneapolis s park and parkway system called the Grand Rounds. The Grand Rounds is a series of seven segments of interconnected parks and parkways that encircle the city and connect lakes, river, creeks, and other natural features. In 2012 the Grand Rounds was determined eligible for listing in the National Register. However, Bridge was constructed outside of the district s period of significance; as such it is a noncontributing resource. Alterations to the bridge have been minor and include the addition of metal railings along the sidewalk. As such the bridge retains integrity of design, materials, and workmanship. The bridge continues to carry vehicular traffic over Minnehaha Creek at Chicago Avenue South in Minneapolis. It retains integrity of location, setting, feeling, and association. The period of significance for Bridge is 1970 to correspond with its date of construction. Built in 1970, Bridge is significant under Criterion C in the area of Engineering as an example of the early use of post-tensioned concrete slab design and construction in Minnesota. Although prestressed concrete continued to be a prominent bridge building technique, the post-tensioned slab design was, and continues to be, a variation used only in selected circumstances that require its ability to provide the thinnest slab for a specified length. JULY 2014 Historic Data II - 4

8 II Historic Data Historic Context Minnesota Bridges, National Register Status Criterion A Significance Criterion C Significance Historic District SHPO inventory number Eligible (Individually) N/A Engineering: Evolution of type N/A HE-MPC Sources Used to Compile Section II -- Historic Data Mead & Hunt, Inc. Minnesota Bridges, Prepared for Minnesota Department of Transportation Minnesota Department of Transportation. Bridge Structure Inventory Report Cringler, John. Post-tensioning Revisited. Structure Magazine, July 2007, Lin, T.Y. Design of Prestressed Concrete Structures. New York: John Wiley & Sons, Fredrickson, R. Bridge construction plans. Prepared for the City of Minneapolis, City of Minneapolis Department of Public Works. Rail height extension for Bridge No October Field inspection LHB, Inc. and Mead & Hunt, Inc., 18 September JULY 2014 Historic Data II - 5

9 II Historic Data Character-Defining Features Character-defining features are prominent or distinctive aspects, qualities, or characteristics of a historic property that contribute significantly to its physical character. Features may include materials, engineering design, and structural and decorative details. Often, the character-defining features include important historic fabric. However, historic fabric can also be found on other elements of a bridge that have not been noted as character-defining. For this reason, it is important to consider both characterdefining features and the bridge s historic fabric when planning any work. Feature 1: Design and construction of an early prestressed, post-tensioned bridge. JULY 2014 Historic Data II - 6

10 III Bridge Data Date of Construction (remodel) 1970 Common Name (if any) Location Feature Carried: CHICAGO AVE S Feature Crossed: Minnehaha Creek County: Hennepin Ownership: City of Minneapolis MnDOT Structure Data *Data Current (as of): Aug 2014 Main Span Type: P09 PSTNSD SLB SPAN Main Span detail: Substructure Type - Foundation Type: Abutment: 1-Concrete - 3-Footing/Pile Piers: N-Not Applicable - N-Not Applicable Total Length: 53 ft Main Span Length: 51 ft Total Number of Span(s): 1 Skew (degrees): 11L Structure Flared: No Flare Roadway Function: Urban, Collector Custodian/Maintenance Type: City Reported Owner Inspection Date 7/16/2013 Sufficiency Rating 94.1 Operating Rating HS 31.9 Inventory Rating HS 15.8 Structure Status A - Open Posting VEH: SEMI: DBL: Design Load HS20 Current Condition Code Roadway Clearances Deck: 6 Roadway Width: 52 ft Superstructure: 7 Vert. Clearance Over Rdwy: N/A Substructure: 7 Vert. Clearance Under Rdwy: N/A Channel and Protection: 8 Lat. Clearance Right: 0 ft Culvert: N Lat. Clearance Left: 0 ft Current Appraisal Rating Roadway Data Structural Evaluation: 6 ADT Total: 5300 (2008) Deck Geometry: 9 Truck ADT Percentage: Not given Underclearances: N Bypass Detour length: 1 mile Waterway Adequacy: 8 Number of Lanes: 2 Approach Alignment: 8 Fracture Critical No Waterway Data Deficient Status ADEQ Scour Code: I-LOW RISK Non-MnDOT Data Approach Roadway Characteristics **Number of Crashes reported Lane Widths: 13 ft in MnMCAT within 500 feet Shoulder Width: 13 ft of Bridge Site 35 Shoulders Paved or Unpaved: Paved Roadway Surfacing: Bituminous Location of Plans Plans Available City of Minneapolis 1970 Original Plan & 1987 Rail Extension Plan * Non-MnDOT data collected during field survey. All other fields of data collected from MnDOT August of See Appendix C for MnDOT inventory and inspection report data. ** Unless a significant number of crashes are noted on or near a bridge, the accident data is not detailed in this report. JULY 2014 Bridge Data III - 7

11 IV Existing Conditions/Recommendations Existing Conditions Available information, as detailed in the Project Introduction section, concerning Bridge was reviewed prior to visiting the bridge site. The site visit was conducted to establish the following: 1. General condition of structure 2. Conformation to available extant plans 3. Current use of structure 4. Roadway/pedestrian trail geometry and alignment (as applicable) 5. Bridge geometry, clearances and notable site issues General Bridge Description Bridge is a post-tensioned concrete slab span bridge. The bridge carries Chicago Avenue with a single 51-foot span over Minnehaha Creek in the city of Minneapolis. The slab, abutments, wingwalls and interior bridge railings are comprised of cast-in-place reinforced concrete. The exterior railings are metal and there are two light posts with the fixtures built into each exterior railing. The bridge has an out-to-out width, including sidewalk overhangs, of 67 feet and a clear roadway width of 52 feet. There is a pedestrian sidewalk on each side of the roadway on the bridge and a 10-foot-wide trail under the bridge that is located along the south abutment. The abutment and wingwall footings are supported by steel piles. In 1987, a repair project converted the 3-foot-tall exterior metal rail to a 4-foot-6-inch rail by adding a metal rail extension to the top of the original rail. This is the only known instance of major work that was performed on the bridge. The major defects of the bridge include cracking and spalling of the deck slab, deterioration of the metal railing and spalling of the underside of the sidewalk overhang. Serviceability Observations The bridge is currently open to vehicular and pedestrian traffic with no apparent load posting restrictions from legal loads. Condition Observations Post-tensioned Concrete Slab: The post-tensioned concrete slab appears to be in fair condition. On the top surface, there are open spalls along the longitudinal centerline of the bridge. There is also a longitudinal crack running the entire length of the bridge span located west of the centerline. There is spalling around this crack. Throughout the top side of the slab there are several smaller transverse and longitudinal cracks. At each end of the slab, the sealant in the joint between the approach panel and the deck slab is beginning to fail. On the deck underside, there are two full length longitudinal cracks as well as many fine longitudinal cracks that are showing signs of seepage indicated by the presence of efflorescence. On the edge of the deck at the abutment at the southwest wingwall, there is a large spall in the concrete with exposed reinforcing. Due to the concealment of the post-tensioning system its condition is unable to be assessed. Approach Panels The concrete approach panels are in fair condition. The south approach panel has minor cracking that has been previously sealed. There are pop-outs and areas of scaling throughout the surface of the panel. The north approach has minor pop-outs, some surface scaling, and spalling along both transverse ends JULY 2014 Existing Conditions/Recommendations IV - 8

12 IV Existing Conditions/Recommendations of the panel. Each approach is experiencing minor settling and the compression seals in the joints along the curbs are beginning to fail. Sidewalk The sidewalks are in fair to poor condition. The sidewalks consist of an overhang poured monolithic with the deck slab on each side of the bridge. The top sides of the sidewalks are in good condition with minimal cracking and scaling. On the undersides, there is spalling and delamination occurring along the entire length near the outside edge of the east and west sidewalks. These delaminations are caused by the deteriorating metal rail attached to the sidewalk edge. At each sidewalk joint, where the bridge deck meets the approach panel, there was originally a waterproof material (bituminous felt) in the joint which was topped with sealant. This joint has failed at all 4 corners of the bridge and the joint material has fallen out of the joint in most locations. The last sidewalk panel on the northeast approach has settled more than 1 inch, and the last panel on the southeast has settled about one-half inch. Railings There are two sets of railings on this bridge. The interior concrete railings protect the sidewalk from vehicular traffic. These concrete railings are in fair condition with some vertical cracks throughout (most of which have been sealed). There is also some spalling of the concrete and loss of surface finish at various locations along the railing. The exterior metal railings are attached to the outer edge of the sidewalks and are in poor condition. The original metal rails have been extended with an 18-inch railing extension to increase their height. The paint system on both the original rail and railing extension has failed. The galvanized coating under the topcoat of paint on the rail extension is in good condition (except at the welds). The original railing is showing surface rusting over the entire surface of the rail. The bottom of the metal railing is corroding which is causing the railing to lean inwards towards the sidewalk on both sides of the bridge. Wingwalls and Bridge Slopes All four wingwalls are in good condition with no visible deterioration of the concrete or misalignment of the walls. The slopes in front of the walls are paved with grouted riprap on the north side and are riprapped on the south side with a small retaining wall at the toe of the slope along the trail. These retaining walls appear to be leaning towards the trail. Abutments The concrete abutments are in good condition. No significant defects were observed. Trail under Bridge The trail under the bridge is being undermined by the creek and has begun to settle. Approach/Waterway Observation The waterway appears to be in good condition with no major scour or erosion observed. The roadway is straight at each end of the bridge. Directly north of the bridge there is a signalized intersection (Chicago Avenue and Minnehaha Parkway) which appears to be heavily traveled. There have been 35 reported JULY 2014 Existing Conditions/Recommendations IV - 9

13 IV Existing Conditions/Recommendations accidents on Chicago Avenue within 500 feet of the bridge site. None of these accidents appear to be attributed to the bridge, but rather the high volume of traffic and pedestrians in this location. Date of Engineering Site Visit by LHB September 18, 2013 JULY 2014 Existing Conditions/Recommendations IV - 10

14 IV Existing Conditions/Recommendations Condition 1: West elevation Condition 2: South approach, looking north JULY 2014 Existing Conditions/Recommendations IV - 11

15 IV Existing Conditions/Recommendations Condition 3: Longitudinal crack and spalling in deck Condition 4: South approach panel (note surface scaling and previously sealed cracks) JULY 2014 Existing Conditions/Recommendations IV - 12

16 IV Existing Conditions/Recommendations Condition 5: North approach panel (left), expansion joint (center) & bridge deck/slab (right) Condition 6: Concrete rail (note vertical cracking) JULY 2014 Existing Conditions/Recommendations IV - 13

17 IV Existing Conditions/Recommendations Condition 7: Sidewalk underside (note cracking and spalling near rail connection) Condition 8: Northeast sidewalk panel JULY 2014 Existing Conditions/Recommendations IV - 14

18 IV Existing Conditions/Recommendations Condition 9: Northwest rail (note leaning metal rail) Condition 10: Rail paint condition, typical JULY 2014 Existing Conditions/Recommendations IV - 15

19 IV Existing Conditions/Recommendations Condition 11: Southwest wingwall and slope Condition 12: Southwest spalling of slab at abutment/wingwall joint JULY 2014 Existing Conditions/Recommendations IV - 16

20 IV Existing Conditions/Recommendations Condition 13: Northwest wingwall and slope Condition 14: North abutment and northwest slope JULY 2014 Existing Conditions/Recommendations IV - 17

21 IV Existing Conditions/Recommendations Condition 15: Slab underside Condition 16: South abutment and walk JULY 2014 Existing Conditions/Recommendations IV - 18

22 IV Existing Conditions/Recommendations Overall Recommendations The bridge is currently open to vehicular and pedestrian traffic. The recommendations which follow assume the structure s use will remain the same. Recommended Stabilization Activities 1. The post-tensioned concrete slab should be repaired to prevent further deterioration of both the slab and other elements of the bridge. All visible longitudinal and transverse cracks should be sealed with a poured epoxy sealant (estimated 250 linear feet). 2. After the cracks are sealed, the spalls in the deck and approach panels should be patched along with the large spall on the underside in the southwest corner (estimated 75 square feet). Care in selection of material and forming/ finishing methods will be necessary so that repair material will match in place material in finish, composition, texture and color. Recommended Preservation Activities Post-tensioned Concrete Slab The repair items for the deck are predominately addressed in the stabilization section above. It would also be very beneficial to the substructures if the expansion joints at each end of the deck were re-sealed to prevent water from seeping down to the abutment and wingwalls below. It is also possible, depending on the structure s design, that leaking at the slab ends is leading to corrosion of the post tensioning tendon ends if their detailing is exposed or embedment is shallow in this region. Approach Panels The approach panel spalling is recommended to be repaired, in the stabilization section, at the same time as the deck is patched. There is no repair recommendation for the surface scaling at this time. However, the compression seals at the curbs should be re-sealed in order to keep moisture away from the bridge s wingwalls. Sidewalk The delaminations on the underside of the sidewalk should be repaired following the repair of the metal rail attached to the sidewalk edge (see Railing discussion below). There are approximately 140 square feet of spalled concrete along the sidewalk edges. The concrete surface repair will likely require removal depth of 2 to 4 inches of deteriorated concrete to reach sound concrete, blasting clean and epoxy coating of any rusting or exposed reinforcing steel, and then replacement with repair concrete of color, composition and finish (including the texture from forming) to match the existing concrete. The open joints near the approach panels should be re-sealed. Lastly, the northeast panel of sidewalk that has settled should be removed and replaced to reduce the current trip hazard. The replacement sidewalk panel should utilize material of like color, composition and finish as the original sidewalk. Railings It is recommended that the spalling of the concrete rail be repaired and then the surface finish re-applied to the railings. The original finish of the railings should be investigated and replicated when re-finishing JULY 2014 Existing Conditions/Recommendations IV - 19

23 IV Existing Conditions/Recommendations the surface of the concrete railings. To repair the metal railings, they will need to be removed from the bridge. The railings are currently secured to the edge of the walk with welded joints between the rail base plate and an embedded metal plate along the vertical face of the sidewalk overhang edge. Once the railings are removed, they should be blasted clean of all corrosion and re-coated. Any steel to remain on the bridge should also be cleaned and repainted. The railing should be re-attached to the sidewalk in a fashion that will discourage future corrosion and also be sympathetic to the historically welded connection. Wingwalls and Bridge Slopes There are no repair recommendations for the bridge slopes or wingwalls. The retaining walls at the toe of the north slopes should be monitored for further movement as they appear to be leaning, however it is unknown whether this is a dynamic or stabilized condition. Abutments There are no repair recommendations for the concrete abutments. Trail under Bridge Due to the trail not being a structural element of the bridge, repairs to the trail have been excluded from the cost estimate/recommendations. Recommended Annual Maintenance Activities 1. Flush bridge structural slab, sidewalks and railings each spring with water to remove salt residue. Low pressure spray, less than 400 psi, should be used to ensure there is no damage to surface finishes. Test flushing method and water pressure to ensure it does not damage or abrade the bridge surfaces. 2. Replace approach panel, deck, sidewalk, and rail joint sealant on an approximate 5 year cycle. Costs in estimate are annualized at 20 percent of the one-time cost. JULY 2014 Existing Conditions/Recommendations IV - 20

24 V Projected Costs Summarized Maintenance, Stabilization and Preservation Construction Cost Estimates It is important to recognize that the work scope and cost estimates presented herein are based on a limited level assessment of the existing structure. In moving forward with future project planning, it will be essential to undertake a detailed structure assessment addressing the proposed work for the structure. It is also important that any future preservation work follow applicable preservation standards with emphasis to rehabilitate and repair in-place structure elements in lieu of replacement. This includes elements which are preliminarily estimated for replacement within the work scope of this report. Only through a thorough review of rehabilitation and repair options and comprehensive structural and historic assessment can a definitive conclusion for replacement of historic fabric be formed. The opinions of probable construction and administrative costs provided below are presented in 2013 dollars. These costs were developed without benefit of a detailed, thorough bridge inspection, bridge survey or completion of preliminary design for the estimated improvements. The estimated costs represent an opinion based on background knowledge of historic unit prices and comparable work performed on other structures. The opinions of cost are intended to provide a programming level of estimated cost. These costs will require refinement and may require significant adjustments as further analysis is completed in determining the course of action for future structure improvements. A 20 percent contingency and 7 percent mobilization allowance has been included in the construction cost estimates. Administrative and engineering costs are also presented below. Engineering and administrative costs are also to be interpreted as programming level only. Costs can be highly variable and are dependent on structure condition, intended work scope, project size and level of investigative, testing and documentation work necessary. Additional studies, evaluation, and historical consultation costs not exclusively called out may also be incurred on a case-by-case basis. Maintenance, Stabilization, and Preservation Costs (refer to the work item breakdown on the next page) Opinion of Annual Cost- Maintenance Activities: $ 4,740 Opinion of Construction Cost- Stabilization Activities: $ 21,000 Opinion of Construction Cost- Preservation Activities: $ 99,520 Estimated Preliminary Design, Final Design, Construction Administration Costs Preliminary Design and Assessment $ 3,000 Final Design and Plans $ 12,000 Construction Administration $ 15,000 JULY 2014 Projected Costs V - 21

25 V Projected Costs MAINTENANCE, STABILIZATION & PRESERVATION COST ESTIMATE (2013 DOLLARS) Bridge No July 31, 2014 ESTIMATED QUANTITIES AND COST ITEM NO. ITEM UNIT QUANTITY UNIT COST TOTAL ESTIMATE MAINTENANCE COSTS 1 FLUSH BRIDGE OF SALTS IN SPRING LUMP SUM 1 $1, $1, REPAIR/REPLACE DECK JOINT SEALANT LIN FT 244 $10.00 $2, %- 5 year cycle) 20% CONTINGENCY LUMP SUM 1 $ $ STABILIZATION COSTS ESTIMATED MAINTENANCE COSTS $4, SEAL CRACKS/JOINTS IN DECK LIN FT 250 $16.00 $4, PATCH SPALLS IN TOP OF DECK & APPR. PANELS SQ FT 75 $ $13, % CONTINGENCY LUMP SUM 1 $3, $3, ESTIMATED STABILIZATION COSTS $21, PRESERVATION COSTS 7% LUMP SUM 1 $3, $3, REPLACE SEALANT AT DECK EXP. JOINTS & CONC RAIL LIN FT 140 $40.00 $5, REPLACE COMPRESSION JOINTS AT APPR. PANEL LIN FT 80 $80.00 $6, CONCRETE SURFACE REPAIR - WALK UNERSIDE SQ FT 140 $ $30, REPLACE SIDEWALK SEALANT JOINT AT APPROACHES LIN FT 24 $50.00 $1, REPLACE SIDEWALK PANEL - NE SQ FT 35 $60.00 $2, CONCRETE SURFACE REPAIR - CONC RAIL SQ FT 30 $ $3, SURFACE FINISH - CONCRETE RAILINGS SQ FT 1260 $7.00 $8, REMOVE AND REATTACH METAL RAIL LUMP SUM 1 $10, $10, CLEAN AND REPAINT METAL RAIL LIN FT 180 $60.00 $10, % CONTINGENCY LUMP SUM 1 $16, $16, ESTIMATED PRESERVATION COSTS $99, JULY 2014 Projected Costs V - 22

26 Appendices Appendix A. Glossary JULY 2014 Appendices - 23

27 Glossary Abutment Component of bridge substructure at either end of bridge that transfers load from superstructure to foundation and provides lateral support for the approach roadway embankment. Appraisal ratings Five National Bridge Inventory (NBI) appraisal ratings (structural evaluation, deck geometry, under-clearances, waterway adequacy, and approach alignment, as defined below), collectively called appraisal ratings, are used to evaluate a bridge s overall structural condition and loadcarrying capacity. The evaluated bridge is compared with a new bridge built to current design standards. Ratings range from a low of 0 (closed bridge) to a high of 9 (superior). Any appraisal item not applicable to a specific bridge is coded N. Approach alignment One of five NBI inspection ratings. This rating appraises a bridge s functionality based on the alignment of its approaches. It incorporates a typical motorist s speed reduction because of the horizontal or vertical alignment of the approach. Character-defining features Prominent or distinctive aspects, qualities, or characteristics of a historic property that contribute significantly to its physical character. Features may include structural or decorative details and materials. Condition, fair A bridge or bridge component of which all primary structural elements are sound, but may have minor deterioration, section loss, cracking, spalling, or scour. Condition, good A bridge or bridge component which may have some minor deficiencies, but all primary structural elements are sound. Condition, poor A bridge or bridge component that displays advanced section loss, deterioration, cracking, spalling, or scour. Condition rating Level of deterioration of bridge components and elements expressed on a numerical scale according to the NBI system. Components include the substructure, superstructure, deck, channel, and culvert. Elements are subsets of components, e.g., piers and abutments are elements of the component substructure. The evaluated bridge is compared with a new bridge built to current design standards. Component ratings range from 0 (failure) to 9 (new) or N for (not applicable); elements are rated on a scale of 1-3, 1-4 or 1-5 (depending on the element type and material). In all cases condition state 1 is the best condition with condition state 3, 4 or 5 being the worst condition. In rating a bridge s condition, MnDOT pairs the NBI system with the newer and more sophisticated Pontis element inspection information, which quantifies bridge elements in different condition states and is the basis for subsequent economic analysis. Corrosion The general disentegration of metal through oxidation. Cutwater The wedge-shaped end of a bridge pier, designed to divide the current and break up ice.

28 Decay Deterioration of wood as a result of fungi feeding on its cell walls. Delamination Surface separation of concrete, steel, glue laminated timber plies etc. into layers. Deck geometry One of five NBI appraisal ratings. This rating appraises the functionality of a bridge s roadway width and vertical clearance, taking into account the type of roadway, number of lanes, and ADT. Deficiency The inadequacy of a bridge in terms of structure, serviceability, and/or function. Structural deficiency is determined through periodic inspections and is reflected in the ratings that are assigned to a bridge. Service deficiency is determined by comparing the facilities a bridge provides for vehicular, bicycle, and pedestrian traffic with those that are desired. Functional deficiency is another term for functionally obsolete (see below). Remedial activities may be needed to address any or all of these deficiencies. Deficiency rating A nonnumeric code indicating a bridge s status as structurally deficient (SD) or functionally obsolete (FO). See below for the definitions of SD and FO. The deficiency rating status may be used as a basis for establishing a bridge s eligibility and priority for replacement or rehabilitation. Design exception A deviation from federal design and geometric standards that takes into account environmental, scenic, aesthetic, historic, and community factors that may have bearing upon a transportation project. A design exception is used for federally funded projects where federal standards are not met. Approval requires appropriate justification and documentation that concerns for safety, durability, and economy of maintenance have been met. Design load The usable live-load capacity that a bridge was designed to carry, expressed in tons according to the AASHTO allowable stress, load factor, or load resistance factor rating methods. An additional code was recently added to assess design load by a rating factor instead of tons. This code is used to determine if a bridge has sufficient strength to accommodate traffic load demands. A bridge that is posted for load restrictions is not adequate to accommodate present or expected legal truck traffic. Deterioration Decline in condition of surfaces or structure over a period of time due to chemical or physical degradation. Efflorescence A deposit on concrete or brick caused by crystallization of carbonates brought to the surface by moisture in the masonry or concrete. Extant Currently or actually existing. Extrados The upper or outer surfaces of the voussoirs which compose the arch ring. Often contrasted with intrados.

29 Footing The enlarged, lower portion of a substructure which distributes the structure load either to the earth or to supporting piles. Fracture Critical Members Tension members or tension components of bending members (including those subject to reversal of stress) whose failure would be expected to result in collapse of the bridge. Functionally obsolete The Federal Highway Administration (FHWA) classification of a bridge that does not meet current or projected traffic needs because of inadequate horizontal or vertical clearance, inadequate load-carrying capacity, and/or insufficient opening to accommodate water flow under the bridge. An appraisal rating of 3 or less for deck geometry, underclearance, approach alignment, structural evaluation or waterway adequacy will designate a bridge as functionally obsolete. Gusset plate A plate that connects the horizontal and vertical members of a truss structure and holds them in correct position at a joint. Helicoidal Arranged in or having the approximate shape of a flattened coil or spiral. Historic fabric The material in a bridge that was part of original construction or a subsequent alteration within the historic period of the bridge (i.e., more than 50 years old). Historic fabric is an important part of the character of the historic bridge and the removal, concealment, or alteration of any historic material or distinctive engineering or architectural feature should be avoided if possible. Often, the characterdefining features include important historic fabric. However, historic fabric can also be found on other elements of a bridge that have not been noted as character-defining. Historic bridge A bridge that is listed in, or eligible for listing in, the National Register of Historic Places. Historic integrity The authenticity of a bridge s historic identity, evidenced by the survival and/or restoration of physical characteristics that existed during the bridge s historic period. A bridge may have integrity of location, design, setting, materials, workmanship, feeling, and association. Inspections Periodic field assessments and subsequent consideration of the fitness of a structure and the associated approaches and amenities to continue to function safely. Intrados The innner or lower surface of an arch. Often contrasted with extrados. Inventory rating The load level a bridge can safely carry for an indefinite amount of time expressed in tons or by the rating factor described in design load (see above). Inventory rating values typically correspond to the original design load for a bridge without deterioration. Keystone Wedge-shaped stone, or voussoir, at the crown of an arch.

30 Load Rating The determination of the live load carrying capacity of a bridge using bridge plans and supplemented by field inspection. Maintenance Work of a routine nature to prevent or control the process of deterioration of a bridge. Minnesota Historical Property Record A documentary record of an important architectural, engineering, or industrial site, maintained by the Minnesota Historical Socitety as part of the state s commitment to historic preservation. MHPR typically includes large-format photographs and written history, and may also include historic photographs, drawings, and/or plans. This state-level documentation program is modeled after a federal program known as the Historic American Buildings Survey/Historic American Engineering Record (HABS/HAER). National Bridge Inventory Bridge inventory and appraisal data collected by the FHWA to fulfill the requirements of the National Bridge Inspection Standards (NBIS). Each state maintains an inventory of its bridges subject to NBIS and sends an annual update to the FHWA. National Bridge Inspection Standards Federal requirements for procedures and frequency of inspections, qualifications of personnel, inspection reports, and preparation and maintenance of state bridge inventories. NBIS applies to bridges located on public roads. National Register of Historic Places The official inventory of districts, sites, buildings, structures, and objects significant in American history, architecture, archaeology, and culture, which is maintained by the Secretary of the Interior under the authority of the National Historic Preservation Act of 1966 (as amended). Non-vehicular traffic Pedestrians, non-motorized recreational vehicles, and small motorized recreational vehicles moving along a transportation route that does not serve automobiles and trucks. Includes bicycles and snowmobiles. Operating rating Maximum permissible load level to which a bridge may be subjected based on a specific truck type, expressed in tons or by the rating factor described in design load (see above). Pack rust Rust forming between adjacent steel surfaces in contact which tends to force the surfaces apart due to the increase in steel volume. Pier A substructure unit that supports the spans of a multi-span superstructure at an intermediate location between its abutments. Pointing The compaction of mortar into the outermost portion of a joint and the troweling of its exposed surface to secure water tightness and/ or desired architectural effect (when replacing deteriorated mortar).

31 Pony truss A through bridge with parallel chords and having no top lateral bracing over the deck between the top chords. Posted load Legal live-load capacity for a bridge which is associated with the operating rating. A bridge posted for load restrictions is inadequate for legal truck traffic. Pontis Computer-based bridge management system to store inventory and inspection data and assist in other bridge data management tasks. Preservation Preservation, as used in this report, refers to historic preservation that is consistent with the Secretary of the Interior s Standards for the Treatment of Historic Properties. Historic preservation means saving from destruction or deterioration old and historic buildings, sites, structures, and objects, and providing for their continued use by means of restoration, rehabilitation, or adaptive reuse. It is the act or process of applying measures to sustain the existing form, integrity, and material of a historic building or structure, and its site and setting. MnDOT s Bridge Preservation, Improvement and Replacement Guidelines describe preservation differently, focusing on repairing or delaying the deterioration of a bridge without significantly improving its function and without considerations for its historic integrity. Preventive maintenance The planned strategy of cost-effective treatments that preserve a bridge, slow future deterioration, and maintain or improve its functional condition without increasing structural capacity. Reconstruction The act or process of depicting, by means of new construction, the form, features, and detailing of a non-surviving site, landscape, building, structure, or object for the purpose of replicating its appearance at a specific period of time and in its historic location. Activities should be consistent with the Secretary of the Interior s Standards for the Treatment of Historic Properties. Rehabilitation The act or process of returning a historic property to a state of utility through repair or alteration which makes possible an efficient contemporary use, while preserving those portions or features of the property that are significant to its historical, architectural, and cultural values. Historic rehabilitation, as used in this report, refers to implementing activities that are consistent with the Secretary of the Interior s Standards for the Treatment of Historic Properties. As such, rehabilitation retains historic fabric and is different from replacement. MnDOT s Bridge Preservation, Improvement and Replacement Guidelines describe rehabilitation and replacement in similar terms. Restoration The act or process of accurately depicting the form, features, and character of a property as it appeared at a particular period of time. Activities should be consistent with the Secretary of the Interior s Standards for the Treatment of Historic Properties. Ring stone One of the separate stones of an arch that shows on the face of the headwall, or end of the arch. Also known as a voussoir.