Members of the diaspora can draw critical attention to topical concerns, provided information is not withheld. I make reference to the Ministry of Agriculture’s (MoA) web publication of selective documents on the preliminary draft report of the northern relief canal for the East Demerara Water Conser-vancy. The website information on the proposed bridge over the canal at the Hope/Douchfour Public Road is limited to two sections: a part longitudinal section and a cross-section. The submission of a preliminary draft report suggests that it is not the first time the Ministry of Public Works, Roads Division, would be seeing the vertical profile (geometric design) of the bridge. It can be inferred that the vertical profile consists of an ascending approach at 5% from the existing road (say vertical curve 1) to the toe of the bridge (say vertical curve 2) and then a 7.5% slope to the centre span (say vertical curve 3). The bridge is symmetrical, therefore, similar curves would be repeated on the descending side. Generally 7.5% slopes are considered steep, and in this situation, I foresee traffic congestion and safety concerns. On temporary structures, like the floating bridges, 7.5% slopes may be accepted, but this bridge cannot be classified as temporary. Vertical curve calculations were not published and as such, I cannot determine the designer’s intent at fitting vertical curves 1, 2 and 3 at the change of slope points, given the dimensions stated on the longitudinal section, unless the design calls for the use of a very low design speed, far less than 25 mph. At higher speed, drivers would experience a heavy bump at the sag curves (curves 1 & 2) and be airborne at the crest curve (curve 3). In conclusion, I would urge the MoA to review the geometric design of the bridge at the Hope/Douchfour Public Road.
Yours faithfully,
Ralph V Seegobin
