- Created on Sunday, 27 November 2011 15:48
I am writing this in connection with the ongoing construction taking place within Nyayo Highrise Estate off Mbagathi road in Nairobi Kenya. Any normal construction would not raise concern however this particular construction site has been hived out of an active dam wall and foundation of the same.
To view the site you can on any terrain satellite go to 1019’01.15” (1.31698) south and 36048’21.22” (36.80589) east.
The purpose of this article is to inform, to document i.e. To have some record of this committed to file and to raise pertinent concerns that trouble my mind as a concerned Kenyan and resident of Highrise estate below the dam wall.
I would like to state that I am not an expert in engineering, architecture, hydrology or any related field, so I will be making comments as a layman but this is why this communication has been copied not only to the director of NEMA, but one of NEMA’s leading consultants who happens to be an engineer and hydrologist of international repute (http://ke.linkedin.com/pub/sean-avery/1b/51a/8b3 ). It has also been sent to various concerned persons, organizations and bodies with whom I
communicated at the start of this construction several months ago who continue to follow this construction with ever increasing alarm and it has been copied to the fourth estate.
I have attached some pictures to illustrate the gravity of the situation, but seeing is believing, and so I would recommend if you are able, to see the construction with your own eyes.
Construction commenced in the month of July 2011, within the walls of Block H7 of Nyayo Highrise Estate off Mbagathi road. There was no separate access road to the site and so all excavated material had to pass directly through the estates roads. This soon caused confrontation between the residents and the contractor as the contractor initially worked 24 hours explaining they needed to beat the rain season. The residents called in National Environmental Management Authority (NEMA) who stopped construction briefly and stopped the night work, but also set a limit to the extent of excavation of the dam wall. The contractor was instructed to compress earth in an area they had exceeded in terms of excavation.
In August the contractor then began dumping soil in a field adjacent to the rear parking in agreement with the National Housing Corporation management which was explained to the residents as works leading to a playground for the estate. Hundreds of truckloads of excavated soil have been dumped in this area. Of alarm is the quantity and type of soil removed from the dam and its foundation. As two excavators worked to remove the soil, much of it clay like in nature, a third excavator had to scrape the wet clay-like soil off the tippers in the dump area. Throughout there was seepage of water into the excavated areas and was standard for the contractor to continuously pump water from the depression. This state continued as they put down the foundation in the waterlogged clay soil and have continued to lay and build to this day.
Of great apprehension is the accelerated erosion of the dam wall caused by the construction and the onset of the rains. As may be seen in the pictures attached. Also of grave concern is the casual safety regulation of its workers observed by the contractor. Twice the earth has collapsed into the ongoing works smothering some of the works yet even as this is ongoing the workers are made to fill sand bags and deposit them on the unstable dam wall, in the same breadth trying to assure concerned residents that all is well.
MY PERTINENT CONCERNS AS A LAYMAN
How construction of such illogical proportions was authorized and approved having had to pass through scrutiny of architects, engineers, hydrologists, the city council and NEMA. It is interesting that National Geographic channel ran a series on world dam disasters earlier this year and they are following this one with great concern. (http://en.wikipedia.org/wiki/Dam_failure#List_of_major_dam_failures).
There are many concerns that come to light in view of watching mega structures courtesy of the Discovery channel and knowing that this is an ENGINEERING FIRST in the history of construction. At NO TIME UNTIL NOW has construction ever been carried out on the face of an earth dam wall. I do not intend to display my ignorance but will humbly pose 3 questions and an observation should the dam wall give way.
At no time was any investigation carried out on the site prior to the commencement of construction to my knowledge and many residents that I enquired of.
No coring to establish the soil substructure and suitability for supporting the five storey structure intended to be built.
No thought of the effect of excavation of the dam wall and subsequent support needed for the same especially in regard to the volume and weight of water that lies behind the dam. I fear that should we have a recurrence of heavy sustained rainfall in the catchment area of the dam within a short time span this dam will be breached. A clear example is the El Nino rains that fell a couple of years ago which flooded Mbagathi road from the Bridge below Nyayo Estate all the way to the Nairobi West flyover. Several estates, businesses, a Kenya Power substation to name a few were swamped.
Most of the water that caused this was directly from the dam. The overflow was so great that it cut its own channel outside of the spill way, fortunately into the hill away from the estate. What would the effect be today should this dam wall fail; given that with the little rainfall that has fallen, the wall is collapsing, there is continuous seepage possible occurrence of internal erosion (http://en.wikipedia.org/wiki/Internal_erosion ) and the dumping of soil that has created a narrow funnel for the water to flow, directly into the estate Blocks 8, 9, 10, 11 and 12, notwithstanding the path that the course of water as evidenced by past flooding will follow.
I hope that this email will be read and the urgency of timely action be known by the readers. It is my hope that for those who may have thought of buying property in the face of such inherent peril to think twice. This sadly reminds me of a childhood story of a mouse, a pig, a cow and the farmer’s wife.