By Sue-Ann Wayow
THE majority of landslips in Trinidad occur in the central and southern regions and with Government’s limited funding to the Ministry of Works and Transport, there focus in only repairing the major ones.
On Tuesday, the ministry launched its National Landslip Repair Programme for 2021/2022 at the ministry’s headquaters in Port-of-Spain.
Acting Deputy Permanent Secretary Navin Ramsingh gave an in depth analysis of landslips across the country and possible solutions to have them reduced.
He said, “Every year new landslips are formed and existing landslips cannot be repaired due to the issue with lack of funding, worsening with time. The Ministry’s efforts to reduce the backlog of landslips with restricted funding, in most times limits the MOWT to repairing only critical landslips necessary to keep the roads open and passable to the general public. Critical/emergency repairs are executed by the Ministry’s Highways Division and the Programme for Upgrading Road Efficiency (PURE) Unit, whilst the Bridges, Landslips and Traffic Management (BLT) Unit focuses on the design and construction of the other urgent and more technical landslips in an effort to address the backlog.”
A review of the landslips inventory revealed that most of the landslips in Trinidad occur in the central and south region, in predominantly clay soils and along the roads that are located along the ridges that evolved with time, from tracks to what exists today, he said and given the connectivity that roads provide, landslips therefore affects properties and utilities.
Reasons why there are landslips
He explained that based on an analysis of the historical data on landslips there were eight factors that contribute to the formation of landslips in Trinidad.
Trinidad has two types of roads, those that evolved over time from tracks located on ridges that were upgraded without changing the horizontal or vertical alignment of the tracks to roads and those that were properly engineered with proper embankment, drainage and pavement structure.
“Most of the landslips in south occur in these historical roads that were constructed on ridges,” Ramsingh said.
Updated infrastructure was required in some cases.
Excessive rainfall and improper drainage from privately owned properties also contributes to slippages.
“A lot of people do not seek the advice of a qualified Geotechnical Engineer before construction of their properties,” Ramsingh said.
WASA and water to be blamed too
The Water and Sewerage Authority (WASA) is also to be blamed.
Ramsingh said, “ Quite often, our roads are plagued with numerous water leaks and associated deteriorating road conditions caused primarily by WASA’s failure to carry out timely and effective road rehabilitation. WASA has indicated that waterlines that serve residents who have constructed their homes on hills experience a pressure higher than normal and this together with the age of the pipe and other factors contribute to frequent leakages. These leakages, when left unrepaired over time, scour road bases resulting in landslips.”
Deforestation or removal of vegetation along road slopes, climate change resulting in excessive rainfall and soil types were all contributing factors to the increase in landslips.
Ramsingh said, “Climate change results in excess rainfall. June to December is typically the wet season in Trinidad, however due to climate change the country experienced a ‘wet’ dry season this year. This excess rainfall contributes to an increased amount of landslips forming this year, especially in clay soils. Apart from which, the pattern of intense rainfall over a long duration of time would also trigger additional landslips.”
Working with Energy Ministry
Ramsingh said the Works Ministry has approached the Ministry of Energy and Energy Industries around April 2021 to determine if the major landslips in Princes Town (Lengua) are as a result of faulting and the triggers of the major landslips in the Princes Town area and to advise on further studies.
The report prepared suggested that geological issues such as the type of slope, lithology and soil saturation would have contributed to the landslips in the area. There is faulting in the general area, however there were no direct lineations that would have caused slippage locally. These were based on the findings from the site visit and geology literature. The team would have also consulted with other geologists who reaffirmed their findings.
The road forward
Ramsingh said the ministry will be implemented certain measures to reduce landslip formation while attempting to address the backlog.
He said, the Highways Division will embark on a programme to identify landslips at the early stages and carry out preventative maintenance measures associated with drainage and stabilisation of the slope.
Both the PURE and BLT Units will continue to utilise appropriate environmentally friendly and cost effective repair solutions.
The Town and Country Planning Division should implement a policy for development in the Southern Region of Trinidad similar to that of the existing Hillside/Northern Region Policy once finalised.
The authors of the Trinidad and Tobago Small Building Code should make amendments to the code to specify the standards for construction in expansive clays.
Owners of private property should take precaution before construction and hire a qualified geotechnical engineer to design infrastructure to withstand the shrink/swell behaviour of Trinidad’s expansive clays by determining a suitable foundation depth, protecting the soil from excess grey water and rainwater and determining a suitable location for the placement of septic tanks and soak-away.
And attempts will also be made to encourage WASA to address leaks in the critical landslip prone areas in a timely manner and explore the use of different types of pipe (polytubes, plastic welded joints) that do not require flexible couplings, Ramsingh said.
