Safety issues for remote bridge

An old bridge with weight restrictions that stopped a fire truck from getting to a callout could cost $2.76 million to replace.

The deteriorating state of the bridge, in a remote area on the northwest side of Lake Tekapo, and a number of safety concerns have been highlighted in a report going to the Mackenzie District Council tomorrow.

The report examines the possible replacement of the 124m, single-lane, multiple span timber structure, at an estimated total cost of $2.76m.

Compiled by David Adamson, general manager of operations, planning and regulatory services, the report says Godley Peaks Station, Timaru Boys’ High School (TBHS), the Department of Conservation (DOC), Land Information NZ (LINZ) and the public are all users of the bridge.

Adamson said weight restrictions were first placed on the bridge in 2005 and more recently height-restriction barriers were erected. ‘‘The bridge is now heavily restricted, with the latest inspection in December 2020 stating that the axles are restricted to a weight of 3000kg and the gross weight to 5000kg with a speed restriction of 10kph. This level of restriction essentially reduces the bridge to only providing light vehicle access.’’

Adamson said the only way heavy vehicles could cross was via a ford about 400m downstream. The council had a 30-year resource consent that allowed it to undertake works in the riverbed to maintain the ford. That work was largely carried out by Verity Farms, the current lessee/owner of the station. ‘‘The ford cannot be used in bad weather conditions, after which it has to be cleared by Verity Farms. The weight restriction also prevents access by emergency vehicles, resulting in safety concerns.’’ An event on January 28, 2021, had highlighted those concerns. Adamson said a fire broke out 400m north of the bridge, and the fire brigade was hesitant to cross via the ford.

A decision was made to empty the tank to cross the bridge, which took 35-40 minutes.

‘‘A collision of the tanker with the entrance of the bridge resulted in additional delays before they filled the tank and reported to the fire. By this time, the fire was under control by Godley Peaks staff. Verity Farms expressed significant safety concerns due to the lack of emergency services coverage.’’ Adamson said that at times the only way to get heavy vehicles through the ford was to tow them.

‘‘There are risks associated with the ford as loads include dangerous chemicals, potential contaminants if released, plus some recreational users also take the opportunity to drive down the fan which threatens birds and other natural values.’’

Adamson said the bridge had deteriorated over time and was nearing the end of its useful life.

‘‘The use of the ford by Verity Farms has slowed the degradation of the bridge, extending its life.’’

Adamson said a replacement bridge was necessary to ensure ongoing access and the council needed to consider replacing it with a heavy vehicle accessible bridge. ‘‘There are about 100 heavy vehicle movements (50 return trips) in and out of the station annually through the ford which is equivalent to two movements a week.

‘‘New trucks with technological advances and electronics don’t cope well in deep river crossings.

‘‘Hot oils in gearboxes and differentials can contract when cooled rapidly in the icy water, thus drawing water past the seals.

‘‘This contaminates the oils and other lubricants, leading to premature failure and other problems.’’ Adamson also said trucks were getting larger and axle loadings were typically balanced, meaning they did not have good traction in the riverbed.

‘‘Typically, the ford must be maintained prior to vehicles

crossing to ensure a sufficiently stable base over the main flow, given the bed is constantly shifting given it is an alluvial base.’’ Adamson said the council had no legal obligation to replace the bridge but it was an integral part of its network and the decision was considered significant.

‘‘The current condition, height and weight restrictions have created many issues for Verity Farms.

‘‘It is unable to shift livestock, fertiliser, wool, diesel fuel, logs, silage and agricultural gear via the bridge. As a result, Verity Farms must use the ford to allow for heavy vehicles to access the property and run a working farm.’’

Adamson said Verity Farms was responsible for the maintenance of the ford, which was estimated to be costing about $50,000 annually. Adamson said if the bridge replacement was placed within council’s roading programme, it could attract a 51% subsidy and suggested it went into the next Long Term Plan for the public to be consulted.

High-level discussions had been had regarding the possibility of Verity Farms contributing financially to the replacement of the bridge to ensure its suitability for its needs. ‘‘While Verity Farms has expressed a strong willingness to contribute financially, no proposal has been made as of yet.’’

DOC and LINZ both indicated they could not contribute financially to the project, while TBHS would not commit to a financial contribution to the bridge that provides access to its John Scott Lodge.