It appears that there were serious deficiencies in the design of the Supenaam stelling

Dear Editor,

For over 75 years the Ministry of Public Works (MPW) with its Transport and Harbours Division has been responsible for the ferries and facilities that accommodate them to meet river transportation needs along coastal Guyana. During these years it was expected that they had acquired the skills needed to design and build stellings and wharves to generally accepted standards and the evidence suggests that indeed they had in many cases. However, in SN of May 15, it was reported with astonishment that the Ministry of Local Government (MLG) was responsible for supervision of the design and construction of the Good Hope/Supenaam Stelling (GHSS) but after its completion operational difficulties were encountered which necessitated design changes beyond its capability to rectify the problems and the project belatedly was given to the MPW to fix without recourse to the designers, construction manager or contractor.

The unfolding events in this saga have raised a number of troubling questions. Firstly, information giving details of the experience of the design engineers, their terms of reference and the persons responsible to review the project design at the MLG and give their approval to its details as it was being developed, should be made available for public scrutiny as it appears there were serious deficiencies in the design which failed to meet generally accepted engineering codes and standards as well as fulfilling the needs of users of the facility.

Vessels of the Malali type were built with on/off drawbridges but their effectiveness was limited by the ramps on the stellings on which they rested for loading and unloading and since the functioning ramps were fixed their elevations could not be adjusted to vary with tide levels. Hence they were only useful within a limited tidal range. For other tidal ranges, planks linked together to form stages were used to bridge the gap between vessel and stelling – a slow, labour intensive and often perilous method. Unfortunately, this is how it is today to load and unload berthed vessels operated by the MPW as the drawbridges on the ferries have all disappeared.

Apparently, the GHSS was originally designed to accommodate vessels of the Malali type with their built-in on/off drawbridges. However, in Yr 2010, the MPW realized that there were changes in river transportation and in order to facilitate a quick turn around of vessels of varying types and sizes, loading ramps with on/off drawbridges had to be built onshore to reflect these characteristic necessary changes. Hence the need for modification to the design of an already built GHSS and thus avoid obsolescence.

The preliminary evidence suggests that failure of the re-designed ramp by the MPW with a hinged on/off drawbridge at the GHSS was due to a number of design errors with insufficient attention to the details of connections and support for the steel I beam to which the drawbridge is hinged.
At low tide levels, the non-uniform live loads of heavy vehicles on the drawbridge create uneven flotation movements of the pontoons and moored vessel supporting it thereby causing extreme stress variations and torsion on the drawbridge which are then transferred to the supporting steel I beam to which it is hinged.

Unfortunately under this scenario the eccentric loading on the drawbridge is not uniformly transferred to the supporting I beam but manifests itself as concentrated loads as could be seen from the indentations at two/three locations on the upper flange of the supporting steel I beam and since concentrated loads could cause as much as three times more stresses on a beam than uniform loads, the apparent cause for the beam’s upper flange to compress and buckle under extreme stress variations and inadequate beam support seemed evident. There are also the inadequate hinged connections and anchoring for load transfer between the loading ramp supported on two floating pontoons and the fixed concrete pier, to contend with.

Finally, it is unconscionable that the MLG was assigned to execute this project when it lacked the experience, skilled technical personnel and management capability to undertake an assignment of such complexity which eventually it could not satisfactorily complete and the project had to be given to the MPW to finish but likewise they also seemed to have stumbled because of poor design, lack of construction ingenuity and loose site supervision and with fingers pointing blame everywhere, taxpayers will eventually have to pay the extra millions of dollars to fix the GHSS to make it operational and probably get the answers to this fiasco later.

Yours faithfully,
Charles Sohan

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