Vistabella River Retaining Wall
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CLIENT: Water and Sewage Authority (WASA) St. Joseph Trinidad LOCATION: Central, Trinidad START DATE: September 2011 COMPLETION DATE: March 2014 |
Alpha was engaged by Trinidad Contractors Limited as part of their design build team to carry out engineering designs for the rehabilitation of the Vistabella Trunk Sewer, of which approximately 200 meters has failed along the Vistabella River, to achieve the project objectives required by the Client, WASA.
The San Fernando Wastewater System was constructed in the early 1960’s by the Lock Joint Company and consists of approximately 70 kilometres of sewers of diameters ranging from 200 millimetres to 900 millimetres of concrete pipe. Land slippage along the Vistabella River has resulted in the dislodging of a section of approximately 200 linear metres of the 762 millimetres diameter trunk sewer main. This section of the Vistabella trunk sewer runs along the southern bank of the Vistabella River from a point South of the intersection of Elizabeth and Sapphire Streets, where the Vistabella River intersects with the Pointe a Pierre Road to a point between manhole 80 and 80A west of Smart Street.
The scope of works include the following:
The San Fernando Wastewater System was constructed in the early 1960’s by the Lock Joint Company and consists of approximately 70 kilometres of sewers of diameters ranging from 200 millimetres to 900 millimetres of concrete pipe. Land slippage along the Vistabella River has resulted in the dislodging of a section of approximately 200 linear metres of the 762 millimetres diameter trunk sewer main. This section of the Vistabella trunk sewer runs along the southern bank of the Vistabella River from a point South of the intersection of Elizabeth and Sapphire Streets, where the Vistabella River intersects with the Pointe a Pierre Road to a point between manhole 80 and 80A west of Smart Street.
The scope of works include the following:
- Site reconnaissance, data collection and review of existing information.
- Topographical surveys and establishment of control points, easements, determination of river setbacks and the establishment of right of ways; and sewer reserves.
- Bathymetric survey to tie in the river bathymetry with the topographical surveys to establish the critical river bank sections.
- Geotechnical investigations and review of Geotechnical Report to determine groundwater flow, slope failure analyses and contributing factors.
- Site investigations to determine the existence of pipelines, existing utilities, existing drainage in the way of the works and the need for relocation from the vicinity of the works.
- Horizontal and vertical geometric designs for the final alignment within the established sewer reserve.
- Structural design of pipe and backfill requirements.
- Slope stability analysis and identification of concept designs for review and approval of recommended alternative.
- Structural analysis of the proposed retaining wall solution including foundation design; pile designs and all associated works.
- Drainage design (hydrological studies and hydraulics) for treating surface runoff and consideration of high water flows in the river during storm runoff.
- Cadastral surveys/ right of way and sewer reserve redefinition surveys.
- Detail design drawings for the recommended/approved solution inclusive of associated details.
- Supporting engineering design calculations.