U.S. 231 between Hill Road and Huskey Mountain Road on Brindlee Mountain in Morgan County was closed in February when large cracks appeared in the pavement after heavy rainfall triggered movement of a landslide deep underground, about 50 feet below the road surface. Both the northbound and southbound roadways are closed, and all pavement has been removed from the roughly 1,000-foot areas impacted by the slide.

The repair is a two-phase process. The first phase, which is now complete, consisted of removing 220,000 cubic yards of loose rock and soil to significantly reduce the mass of the landslide and the depth to solid rock. The second phase is the construction of two 1,000-foot bridges crossing the slide area on the existing roadway alignments. These bridges will stand on thick piers anchored in the solid bedrock beneath the landslide.

ALDOT engineers and geotechnical consultants reviewed various options to find a solution that is not only safe, but permanent. Constructing bridges on drilled shafts will allow traffic to overpass the slide on structures that remain unaffected by future slide activity. Each pair of 9.5-foot-wide shafts will be further reinforced by a grade beam, or strut, providing resilience against lateral force.

The Phase 1 contractor has completed the excavation of the slide area, removing 220,000 cubic yards of loose material over the course of two months. ALDOT awarded the bridge construction contract on May 8. The bridge contractor mobilized May 14 to perform preparatory work, with bridge work slated to begin June 1. ALDOT has set a calendar day target of Dec. 2, 2020, six months after work begins, for both bridges to be complete and the highway fully reopened to traffic. If the contractor completes the project on time, the closure of U.S. 231 will have lasted less than 10 months. ALDOT is offering the contractor a substantial monetary incentive for early completion to further reduce that time frame.

The official detours are as follows:

• Northbound commercial traffic is detoured to Alabama 67 to Interstate 65.
• Southbound commercial traffic is detoured to Alabama 36 to Alabama 67.
• Northbound passenger traffic is detoured to Union Hill Road to Alabama 36.
• Southbound passenger traffic is detoured to Alabama 36 to Union Hill Road

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Bridge construction (Phase 2) is anticipated to cost between $18.8 and $21.3 million total. InMay 2020, the Alabama Department of Transportation awarded Brasfield &Gorrie of Birmingham a $14.6 million contract to construct the bridges. Not included in the contract were $4.2 million in custom-fabricated bridge materials ALDOT ordered in advance. ALDOT also attached financial incentives to the contract for early completion that could total nearly $2.5 million.

ALDOT anticipates much of the repair cost being covered by federal aid, which exists for emergencies such as this. The Federal Highway Administration on March 11released $5 million in “quick release” aid. This early round of emergency funds provided a starting point for ALDOT to address damages, including those to U.S.231, caused by the wettest winter on record. We anticipate additional federal emergency funds will be made available as part of the ongoing federal assistance process.

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ALDOTis handling this project under emergency procedures and taking every available measure to reduce the time involved every step of the way — from design, to bidding, to construction.

Repair work began the day after the road was closed, when ALDOT contracted ReedContracting to begin removing pavement from the slide area to facilitate Investigation of the underlying issue.

After investigating the issue, ALDOT evaluated various proposed mitigation measures to find one that could be designed and constructed within the shortest timeframe. The bridge plan was chosen not only because it offers the highest level of safety, but also because it is an efficient and permanent fix.

ALDOT secured Reed’s services to continue with excavation of the slide, the first step of the solution, and that work is now complete. While Phase 1 excavation work was underway, ALDOT worked diligently to develop the Phase 2 bridge concept and design within a five-week window so that contractors would be prepared to submit bids for the project for a May 8 bid opening. Having received federal approval, ALDOT expedited bid review awarded the contract that same day to low-bidder Brasfield & Gorrie.  

ALDOT attached a nearly $2.5 million total incentive to the contract for early completion of the bridges and fully reopening the highway to traffic. ALDOT also took steps to procure in advance more than $4 million in custom-fabricated bridge materials, including girders, bearing pads and casings, to tighten the timeline by reducing the risk of delays for material fabrication during construction.

The steps taken have drastically reduced the anticipated timeline for bridge construction from the original estimate of one year to the current estimate of six months or less.

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Phase1 (excavation) was performed by Reed Contracting with project management byALDOT. The contract for Phase 2 (bridge construction) was awarded to Brasfield& Gorrie of Birmingham. Engineering firm Volkert and Associates will provide construction engineering and inspection services.

The contractor will be eligible to receive a payment of $50,000 for every day the project is complete prior to Dec. 2, up to a maximum of 30 days, and a payment of $33,000 for every day the project is complete prior to Nov. 2, up to a maximum of 30 days. If both bridges are complete and the highway is fully reopened to traffic by Oct. 3, 60 days prior to Dec. 2, the contractor stands to receive the total incentive of $2.49million. The additional cost of the incentives, though substantial, could prevent the extension of losses to motorists in time, fuel, and vehicle wear caused by detours and delays. The contract also includes disincentives for late completion — a deduction of $33,000 per day the project is not complete afterDec. 2, increasing to a deduction of $50,000 per day the project is not complete after Jan. 1, 2021.

Early discussions with industry professionals indicate that it will take contractors about the same length of time to complete one bridge as it will to construct both bridges simultaneously. The total closure of the highway will also speed construction by giving the contractor free rein over the construction zone, rather than working around traffic and maintaining traffic control.

More limited cracking occurred in February 2019. The damage to the roadway in both events was the result of the landslide being activated by heavy rainfall, but the damage in February 2020 was far more extensive, necessitating long-term closure of the highway. The 2019 crack, which primarily affected the outside southbound lane, was able to be temporarily repaired by filling it and repaving the road surface.

Measures to address the landslide were not undertaken in 2019 because the problem had yet to be fully identified. More in-depth repairs to the damaged pavement were not made at that time because, without a way to fix the underlying issue, the possibility of further subterranean movement meant potential repeat damage to the road. Realizing that an underlying geotechnical issue was at work, ALDOT installed instruments to monitor the area and gain a better understanding of the extent, cause, and ways to potentially address the problem. While some additional minor repairs were necessary as the new pavement over the crack settled, the instruments installed on-site detected very little movement during the remainder of 2019. If ALDOT had more information about the problem in February 2019, the prescribed repair then would have been the same as it is today.

The real issue is not that the pavement cracked, but that both roadways sit atop a sizeable landslide. A simple rebuild would remain vulnerable unless the slide is somehow mitigated. Simply excavating to the depth of the slide, refilling it and reconstructing the road would provide no guarantee against reoccurrence.

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Moving the road to an entirely new location would be impractical and cost-prohibitive and would take years to complete. The planALDOT is pursuing will permanently address the slide area, making U.S. 231 safe for motorists, and do so within a relatively brief timeframe, considering the magnitude of the problem. ALDOT’s plan focuses on addressing the roughly 1,000feet of affected roadway, whereas rerouting the road would require new construction of possibly miles of roadway. That would involve time-consuming surveying and plotting of a new route, acquiring right of way, and obtaining environmental approvals, all before design and construction could even begin.

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Engineers considered realigning the roadways through the slide area to place both in an area where the colluvial layer is shallower, meaning bedrock is nearer to the surface. This plan was not pursued for several reasons. Despite the shallower colluvium, the area of the proposed alignment (around the current site of the northbound roadway) was nevertheless heavily impacted by the recent slide activity and would remain susceptible to future movement. This approach would still have required construction of deep-foundation structures to mitigate the slide, and would have also involved blasting and/or drilling of a nearby rock bluff, potential impacts to residences in the area, and time-consuming construction of additional roadway and retaining walls (in addition to any walls constructed to retain the slide) to reconnect to the existing roadways.

For many, the most efficient routes using strictly state-maintained roads are the detour routes already established. However, depending on your base and destination, you may find another alternate route that is better suited to your needs. Please be aware that using local roads as shortcuts is discouraged and can increase your delays due to the high volume of traffic on the official detour routes, particularly at peak travel times. Commercial traffic is restricted from using non-state routes, including the passenger detour on Union Hill Road.ALDOT entered an agreement with Morgan County to allow use of Union Hill Road as part of the official passenger detour only.

To improve traffic flow, ALDOT has made various improvements on the detour routes, including installation of temporary and semi-permanent signals, striping, reflectors, widening turn radii, and major adjustments to timing and functionality of permanent signals. ALDOT engineers and traffic engineering consultants continue to study traffic flow on the detour to identify issues and potential improvements. However, the two-lane roads composing the detour routes are carrying substantially higher traffic volume than normal, and their inherent capacity limitations cannot be completely overcome with temporary measures. Please expect delays and plan additional travel time. Motorists are also asked to remain mindful of speed limits and school zones along the detour routes. Law enforcement agencies are working to ensure the safety of motorists by monitoring detour routes for speeding and aggressive driving.

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