Dear Editor,
After considering my responsibilities to my fellow citizens, I am left with no option but to write to you to identify several cases where engineers are failing or have failed to provide minimum standards of service typical to the engineering profession. I am fully aware that my less competent fellow engineers will not see this as the constructive criticism it is intended to be. Nevertheless I firmly believe that these issues must be identified and remedied if the engineering profession is to advance in Guyana.
There are several ongoing projects in which these design flaws are readily obvious. I will begin by identifying the corrective work on the roadway at Hope on the East Bank of Demerara. The designed solution at that location is attempting to apply a geotechnical engineering solution to what is essentially a hydraulic problem. Most fourth form geography students are familiar with the concept of meandering rivers. Meandering rivers erode material from their outer bank and deposit it on their inner bank. There is a meander in the Demerara River at Hope. The collapsed revetment is indicative of erosion on the outer bank of the river. This erosion cannot be stopped by the installation of a revetment. A more appropriate system would have been to monitor the erosion and to conduct periodic land reclamation at that location. That would have precluded the collapse of the revetment initially built at the site. In spite of this, engineer(s) have chosen to install another revetment as a solution to the problem.
While the solution itself may not be appropriate, its effectiveness is compromised by several design flaws. The most obvious design flaw is the location of the anchor piles within the active zone created by the sheet pile wall. The revetment itself will mobilize active forces. The placement of the anchors will not result in transference of that mobilized force to an area outside of the active pressure zone. This will result in failure of the revetment itself. If it is intended that the revetment progresses to depths adequate to mobilize sufficient passive pressures to prevent failure, then there is no need for the anchor piles. Given the high likelihood that the area will continue to erode, the possibility of sustained stabilizing passive pressures and forces is further minimized.
The second ongoing project is work on the establishment of dual carriageways (not four-lane roads) on the East Bank Demerara. The design apparently involves the removal of soil from the ground surface and replacement of that soil with a uniform sand. All geotechnical engineers who have practised in Guyana are aware that the soil stratigraphy in our coastal plain consists of a desiccated crust above a very soft clay. Moisture contents in the desiccated crust can be as low as 25% and the shear strength can be as high as 900 pounds per square foot (I am using imperial units, since everyone may not be familiar with the SI System). Compared to the desiccated crust the moisture content and shear strength of the underlying soft clays can be as high as 85% and as low as 100 pounds per square foot respectively. Coupled with that, total settlement times in the soft clays can exceed 150 years.
Why engineers will remove competent soil and replace that soil with a uniform, difficult to compact, sand is beyond any technical explanation myself and several other geotechnical engineers can fathom. The containment of that sand within a very low permeability clay further compromises the performance of the intended roadway, since the sand creates a ‘bathtub effect‘ which will result in the reflection of loads imposed on the road back to the surface. This is the reason why we are seeing failures on most of the roads built on our coastal plain. It is fair to expect that engineers would have identified and corrected this problem by now. They obviously have not, since it continues.
As I continue on my drive into Georgetown, I come to the junction of Vlissengen Road and Homestretch Avenue/Croal Street. This road was recently widened to enhance traffic flow at that intersection. I think the intent is commendable. However, the intersection was widened by driving piles and building revetments into the canal on the west side of that intersection. This effectively reduced the area of canal available for flow. Constriction of the canal at this point has resulted in creation of a backwater effect upstream of the intersection. At noon on March 1, there was a marked difference in elevation, of about 1 foot, between the areas east and west of the canal. The Castellani compound and portion of Homestretch Avenue, east of the intersection, are now flooded because of that backwater effect. I challenge the engineers who designed that enhanced intersection to say that a slightly elevated roadway would not have achieved the intended purpose while continuing to ensure the passage of the predesign flow volumes into the western side of the canal.
The most obvious failure of the application of sound engineering principles is reflected in the design of the aquatic centre at Liliendaal on the East Coast Demerara. The weight of soil removed to create the pool at that location is approximately one and one-half times the weight of the pool itself (unit weight of soil approximately 105lbs/ft3 and unit weight of water of 62.4lbs/ft3). In spite of the fact that the pool weighs less than the soil displaced, that facility is supported by piles too numerous to count. I suspect I will hear that these are required to prevent the facility from floating out of the ground. If that is the case, the installation of piles is not the optimum solution. Interested individuals only have to look at several pump stations, installed by Booker Tate, within the GuySuCo infrastructure network at significantly greater depths than the pool at Liliendaal, none of which are supported or anchored by piles. Apparently engineering competence in the public sector is evidenced by standing on site in a reflective vest while observing construction works.
I would hate to create the impression that these design flaws are totally the province of engineers in the public sector. Please remember that the new wing of the St Joseph Mercy Hospital had to be underpinned due to excessive settlement. It should be pointed out that the underpinning required the mobilization of equipment from France at significant cost to the hospital. I am quite sure the hospital would have rather spent that money on patient care.
Of more recent vintage in the private sector is the driving of piles to significant depths within close proximity to existing buildings. Some of these piles are spliced to drive them to depths of more than 100 feet. While this may seem an improvement on past practices such as those which occasioned the detrimental settlement and consequent structural distress of the St Joseph Mercy Hospital south extension, it is archaic in terms of alternative solutions available to address transference of loads to foundations. The use of cast-in-place piles will minimize damage to adjacent structure and provide more reliability in terms of foundation performance. The performance of spliced timber piles proceeds further into the realm of the unknown given the absence of the application of pile integrity testing in Guyana.
I have identified just a few of a plethora of instances where these problems in engineering practice are obvious. The silence from the Guyana Association of Professional Engineers, on all of the issues identified above, is deafening. I suspect that we do not have a law to regulate the practice of engineering in Guyana because no one has been able to demonstrate to the public that engineers are performing an engineering function in this country. The time for that to change is now.
Yours faithfully,
Charles P Ceres
Geotechnical Engineer & Groundwater
Hydrologist
