Wednesday, March 3, 2021

Three-Mile Bridge broken?

50-year-old span rated structurally deficient

Three Mile Bridge, which averages nearly 50,000 vehicle trips a day, is significant less structurally sound than it was just three years ago. Transportation officials think salt-water saturation and intrusion during tropical storms might be to blame.

Three Mile Bridge, which averages nearly 50,000 vehicle trips a day, is significant less structurally sound than it was just three years ago. Transportation officials think salt-water saturation and intrusion during tropical storms might be to blame.

Work plan now required to either fix or replace the connector

Three Mile Bridge has been deemed structurally deficient, and plans to repair or replace the aging highway connector that links Gulf Breeze to Pensacola must be devised and implemented within six years.

Florida Department of Transportation representative Jim DeVries dropped the bombshell news during a recent meeting of the Florida- Alabama Transportation Planning Organization (TPO) when he revealed that Three Mile Bridge is rated at a startling 41 percent sufficiency, down 32 percent in the past three years.

Once the sufficiency rating of a bridge dips below 50 percent, and is therefore declared “structurally deficient,” a work plan must show a series of repairs or replacement within six years, according to DeVries.

Discussion of the bridge, which opened to traffic in 1960, was not listed on the agenda for the Jan. 13 meeting in Pensacola. However, DeVries, FDOT District Three Manager of the Pensacola Urban Office, explained that concerns about the bridge’s decline were raised after the agenda was prepared. He said the announcement needed to be made at the meeting before all the participants.

“The TPO meets approximately every other month,” DeVries explained. “I didn’t want the topic to wait. When we found out about it, District Three Secretary Tommy Barfield talked to Gulf Breeze Mayor Bev Zimmern, and we wanted to let everyone else know about it.”

In August 2007, post-hurricanes Ivan and Dennis, the FDOT announced the bridge rating was determined to be 73 percent. On Jan. 5, 2009, FDOT rated the bridge at 57 percent sufficiency. Last week’s announcement of a deficiency rating at 41 percent was significantly lower, based upon an inspection performed Nov. 4, 2009.

That’s a 16-percent plunge in 10 months.

“Bridges are rated at two basic levels – structurally and functionally,” DeVries explained. “The last Project Development and Environment (PD&E) Study in 2002 indicated that the bridge was already functionally obsolete; now we have renewed concerns regarding structure.”

“Our concerns include several questions,” Gulf Breeze City Manager Edwin “Buz” Eddy said. “Is a replacement bridge in everyone’s best interests? How did a bridge ranking drop from 73 to 41 in a few short years? Will a replacement bridge be the right size and in the right place for the city?”

“It’s not acceptable to answer these questions without asking all the residents who will be impacted. A lot has changed since the 2002 PD&E. How much have traffic volumes changed? Is our population still growing?”

In 2002, record population growth would have affected the PD&E study. According to the U.S. Census Population Estimates for the 100 fastest growing U.S. counties with 10,000 or more population in 2005, Santa Rosa County ranked 85th with a 21.5 increase from April 1, 2000 to July 1, 2005.

Rick Harper, Ph.D., Director of the Haas Center for Business Research and Economic Development at the University of West Florida, sees continued, slow population growth for Santa Rosa County. However, he forecasts a population decline in Escambia County that began after 2006 will continue. Escambia County population could stabilize around 2016 according to Harper’s forecasts. He does not see the Escambia County population rates to regain 2006 levels until 2040.

There are indications that Santa Rosa County School Board staggering of school start times due to budget cuts already has greatly decreased congestion on U.S. Highway 98 in Gulf Breeze. The TPO even passed Resolution 09-03 in March of 2009 to suggest such a move for other school boards based upon the successes in Santa Rosa County.

“Anecdotal evidence suggests – and feedback and comments support – that staggering school start times have a great benefit to traffic on Highway 98,” said Mary Robinson, TPO Director of Transportation. “There are no studies to prove this, however.”

According to FDOT records, Three Mile Bridge averages nearly 50,000 vehicle trips daily, and the topic of bridge replacement has come up in the past. In 2002, the FDOT ordered a PD&E to study the topic.

“We hope a good portion of the data collected in the 2002 PD&E will carry forward,” DeVries said. “We realize there will be some major updates, but much of the data is still good and will help jumpstart the planning process.

“The PD&E is a multi-year process, and the FDOT will ensure a very thorough process.”

DeVries admitted that there are defined federal guidelines to involve the public in the decision making process, even with a deficiency rating in effect.

FDOT sources assert that the precipitous 32-percent drop in only three years could be attributed to salt-water saturation and intrusion during the storms that took effect over time, speeding up the deterioration of the structure. During the storms, surge can increase the salinity of the somewhat brackish bay and sound waters.

“I live in Villa Venyce,” DeVries said. “My wife rides the bridge to work every day, and I ride the Garcon Bridge every day. I know that every citizen from Gulf Breeze and Pensacola that drives the bridge must be considered. We must minimize impacts where we can.

“I know a prime concern for Gulf Breeze is additional lanes. This is not going to happen over night.”

HOW BRIDGE RATINGS ARE DETERMINED

Florida Department of Transportation maintenance office publications assert that Florida “ranks among the lowest in the nation for the percent of bridges that are considered ‘structurally deficient.’ In Florida, this does not mean a bridge is unsafe; if a bridge is unsafe, FDOT does not hesitate to close it immediately.”

A sufficiency rating is a tool that is used to help determine whether a bridge that is structurally deficient or functionally obsolete should be repaired or just replaced.

Rating considers a number of factors, only about half of which relates to the physical condition of the bridge. Such ratings are part of a formula used by the Federal Highway Administration when it allocates federal funds to the states. One-hundred percent represents a bridge that is entirely sufficient, and zero would designate a bridge as entirely insufficient or deficient.

Sufficiency rating is based upon the formula ‘S1 + S2 + S3 – S4 = rating’ when the following considerations are

applied: ¦ S1 – Structural adequacy – with a maximum potential

rating of 55 percent of total value ¦ S2 – Serviceability and functional obsolescence – 30 percent maximum of total value (includes average daily traffic, appropriate roadway width, structure type, bridge roadway width, deck condition, structural evaluation, defense highway designation, etc.) ¦ S3 – Essentiality for Pubic Use – 15 percent max (detour length, average daily traffic, defense highway designation*) ¦ S4 – Special Reductions – limited to 13 percent maximum reduction, based upon detour length, safety features and structure type

A complicated list of calculations and formulas is applied within each category to get the rating, and four separate factors are calculated to obtain the numeric value assigned to indicate bridge sufficiency or deficiency.

Note:
U.S. 98 west of Hurlburt Field is not on the STRAHNET as a defense highway, according to DeVries. In Pensacola, the designation comes down I-110 and stops at 9th Avenue.

 

 

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