The bridges of Nassau County

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  • Recently, the U.S. Department of Transportation’s Federal Highway Administration publicized a vast database on Long Term Bridge Performance – LTBP – for bridges across the country, in every state and county, including Nassau. The database goes back two decades, in some cases, on each of the bridges in reference to the condition rating and evaluation; structure type and materials; inspection; load rating; and traffic and roadway data. Federal Highway Administration
    Recently, the U.S. Department of Transportation’s Federal Highway Administration publicized a vast database on Long Term Bridge Performance – LTBP – for bridges across the country, in every state and county, including Nassau. The database goes back two decades, in some cases, on each of the bridges in reference to the condition rating and evaluation; structure type and materials; inspection; load rating; and traffic and roadway data. Federal Highway Administration
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Bridges and their physical condition matter, and safe and efficient travel over them should be taken for granted. But according to the American Road & Transportation Builders Association, “More than one third (37 percent) of U.S. bridges – nearly 231,000 spans – need repair work. More than 46,000 bridges are rated in poor condition and classified as ‘structurally deficient’ ….” Of the 12,518 bridges in the state of Florida, “2.9% are classified as structurally deficient.”

According to the Florida Department of Transportation, as of September, Nassau County owns and maintains 36 bridges, FDOT owns and maintains 66 bridges in Nassau County, and three bridges are maintained by another entity, either another government agency or a private party.

Recently, the U.S. Department of Transportation’s Federal Highway Administration publicized a vast database on Long Term Bridge Performance – LTBP – for bridges across the country, in every state and county, including Nassau. The database goes back two decades, in some cases, on each of the bridges in reference to the condition rating and evaluation; structure type and materials; inspection; load rating; and traffic and roadway data.

Seeking to understand the current condition of the bridges in the county, the News-Leader reviewed bridge inspection reports in the database from as recently as 2018 and 2019, specifically looking for “scour analysis.”

What is ‘scour’?

Scour is defined on the FHA’s website as “the result of the erosive action of flowing water, excavating, and carrying away material from the bed and banks of streams. Different materials scour at different rates. Loose granular soils are rapidly eroded by flowing water, while cohesive or cemented soils are more scour resistant. However, ultimate scour in cohesive or cemented soils can be as deep as scour in sand-bed streams. Under constant flow conditions, scour will reach maximum depth in sand- and gravel-bed material in hours; cohesive bed material in days; glacial till, sandstones, and shale in months; limestone in years, and dense granite in centuries. Under flow conditions typical of actual bridge crossings, several floods may be needed to attain maximum scour.”

The database contains two alarming codes associated with eight bridges in Nassau County: Code 3 – “Bridge is scour critical; bridge foundations determined to be unstable for calculated scour conditions;” and Code 2 – “Bridge is scour critical; field review indicates that extensive scour has occurred at bridge foundations. Immediate action is required to provide scour countermeasure.”

These two code descriptions, along with other conditions that led many local bridges to be rated as being in “poor” condition, were reviewed with local and state government authorities to determine the status of the bridges as of September 2020.

An email sent to the Florida Department of Transportation requested information on eight county bridges classified in the FHA’s public database as Code 2 or Code 3.

Tracy Hisler-Pace, the communications manager for FDOT’s District Two, said Nassau County, the maintaining agency for the bridges, is the appropriate party to answer questions about maintenance “being completed or will be completed” and when those activities will be completed on specific bridges. “We do complete the inspections of the bridges and recommend repairs, but we are not the owners of the bridges and therefore do not complete the repairs on the bridges,” Hisler-Pace explained.

The county’s response

The News-Leader also contacted County Engineer Robert T. Companion with a request for the current status of county-maintained bridge conditions. Responding via email, Companion wrote, “All 36 bridges are inspected bi-annually by FDOT. Maintenance work, repairs, and total replacement projects are planned and scheduled based on these biannual inspection findings.”

Companion also referred to the information contained on the LTBP website.

“The website you referenced is a public site that gives an overview of each structure and the County also receives a more detailed inspection report that is not public due to security reasons. ... We do take very seriously the condition of the bridges in Nassau County and have completed maintenance to address inspection findings of five bridges already in 2020 and are currently performing maintenance on a sixth bridge.”

‘Scour critical bridges’

The following is a list of the county-maintained bridges tagged with the two “scour critical” codes in the federal database, and Companion’s responses.

• Structure No. 744006 Hill Road at Little Mills Creek

Inspection: June 2018.

Structure: Wood or timber. Constructed 1982. The following items were coded “does not meet currently acceptable standards: bridge railings, transitions, approach guardrail; bridge guardrail ends, substructure condition fair: scour critical foundations unstable.” Companion responded: “Maintenance to this bridge was completed in 2018 including erosion control measures. Additional maintenance is scheduled for the 2021 fiscal year which (began) October 1, 2020. Work is expected to be completed in 2021.”

• Structure No. 740069 CR 200A (Pages Dairy Road) over Lofton Creek

Inspection: June 2018.

Structure: Concrete. Constructed 1958. The following items were coded “does not meet currently acceptable standards: bridge railings, transitions, approach guardrail; bridge guardrail ends, substructure condition poor: scour condition critical, foundations unstable.”

Companion responded: “A replacement structure is currently under design for this bridge. Construction of the new structure will coincide with the Pages Dairy Road widening project and is estimated to be completed in 2021/2022. Regular inspections will continue to be performed on the existing structure.”

‘Poor’ condition or not meeting ‘standards’

Four more county-maintained bridges were listed in the federal database as being in poor condition or not meeting standards. Companion responded to each one when asked about the status.

• Structure No. 744001 – Stokes Road over the St. Marys River

Inspection: June 2018.

Structure: Pre-stressed concrete. Constructed 1978. The following items were coded “does not meet currently acceptable standards: transitions, approach guardrail; bridge guardrail ends. Substructure poor. Deck geometry intolerable: high priority replacement.”

Companion responded: “Maintenance is currently being performed on this bridge to address any inspection findings with an estimated completion date of December 2020.”

• Structure No. 744304 – Crandall Road at McQueen Swamp

Structure: Steel. Constructed 1973. “Channel remediation severely damaged, culvert condition significant deterioration.”

Companion responded: “Maintenance is scheduled for this bridge for the 2021 fiscal year which (began) October 1, 2020. Work is expected to be completed in 2021.”

• Structure No. 740041 – CR 108 over Branch of Little St. Marys River

Inspection: June 2018.

Structure: Concrete. Constructed 1950.The following items were coded “does not meet currently acceptable standards: bridge railings, transitions.”

Companion responded: “Maintenance began on this bridge in August 2020 and was completed in September 2020 to address inspection findings.”

• Structure No. 740050 – CR 121 over Deep Creek

Inspection: June 2018.

Structure: Concrete. Constructed 1949. The following items were coded, “does not meet currently acceptable standards: bridge railings, transitions.”

Companion responded: “Maintenance was completed by the FDOT in October 2019. The structure is listed as a candidate to be replaced by the FDOT for the 2026 fiscal year but has not been confirmed.”

The state’s bridges

The News-Leader followed up with Hisler-Pace to determine the status of the six “scour critical bridges” in Nassau County that have the “owned by state” designation. Two of the bridges in the database – 74001 and 7400082 – cross Lofton Creek on S.R. 200 and were replaced as part of the ongoing widening and upgrade project, but there were four other structures with “scour critical” codes in the federal database: 

• Structure No. 740008 – St. Marys River and U.S. 17

Inspection: 2018.

Structure: Steel. Constructed 1927. The following items were coded “does not meet currently acceptable standards: bridge railings, deck geometry; intolerable, high priority replacement, approach alignment appraisal; intolerable; high priority replacement, scour condition critical, foundations unstable.” Hisler-Pace responded: “740008 – All required phases of scour analysis have been completed. There are no plans for construction at this time. Structure is inspected every 12 months and following any severe storm events.

• Structure No. 740011 – Braddock Creek and US-SB (S.R. 15)

Inspection: June 2018.

Structure: Concrete. Constructed 1924. 

The following items were coded “does not meet currently acceptable standards: scour condition critical, foundations unstable.” Hisler-Pace responded: “740011 – All required phases of scour analysis have been completed. There are no plans for construction at this time. Structure is inspected every 24 months and following any severe storm events.”

• Structure No. 740014 – Car Seat Creek and U.S. 1 SB (S.R. 15)

Inspection June 2018.

Structure: Concrete. Constructed 1924.

The following items were coded “does not meet currently acceptable standards: “scour condition critical, foundations unstable.” Hisler-Pace responded: “740014 – All required phases of scour analysis have been completed. There are no plans for construction at this time. Structure is inspected every 24 months and following any severe storm events.

• Structure No. 740043 – Cushing Creek and S.R. 115

Inspection: April 2017.

Structure: Concrete. Constructed 1948.

The following items were coded “does not meet currently acceptable standards: deck geometry; intolerable, high priority replacement, scour condition critical, foundations unstable.” Hisler-Pace responded: “740043 – All required phases of scour analysis have been completed. There are no plans for construction at this time. Structure is inspected every 24 months and following any severe storm events.

The state responds to ‘scour critical’ codes

Asked for a more detailed explanation of the “scour critical” codes for the four state-maintained bridges, Hisler-Pace said they are “closely monitored.”

“Although a bridge is classified as scour critical, it does not mean the structure is in immediate danger of failure. All bridges are assessed for stability at the 100-year scour storm event. If the bridge is unstable as a result of this evaluation, a point (ground elevation) at which the bridge becomes unstable is established and the bridge is classified as scour critical. As part of the Bridge Safety Inspection Program, scour conditions are monitored. If a structure approaches this scour critical ground elevation threshold, action is taken by the department for state-owned bridges.”

Hisler-Pace also sent an attachment with the following explanation: “Attached is an example profile where the point of instability is set for a structure. This profile is created and verified for changes as part of the routine safety inspection. In the attached document, the bridge is approximately 11-14 feet away from the point of instability. Since the bridge has not reached the point of instability, no immediate action is required other than monitoring. There are structures you have in Nassau County which are scour critical by definition and are closely monitored as part of the Bridge Safety Inspection Program.”