Common use of CULVERT INSTALLATION Clause in Contracts

CULVERT INSTALLATION. As noted previously, the till surface elevation at the borehole locations ranges from a low of el. 15.08 at BH- 02 to a high of el. 15.18 m at BH-01. In view of the loose and potentially compressible nature of the topsoil, it is recommended that the topsoil layer be removed from below the replacement culverts. The excavation should extend downward to the till surface and outward a minimum horizontal distance equal to the depth of new pipe bedding. Based on the conditions encountered at the boreholes, it is expected that approximately 700 mm (+/-) of Class A gravel bedding material will be required to establish the specified invert elevations, following topsoil removal. To ensure stable bearing conditions, the bedding should extend outward from the perimeter of the new culverts a horizontal distance at least equal to the depth of bedding placed below the pipes. Excavation to the required level should be possible with conventional earth moving equipment (i.e., large backhoe or excavator). Final excavation to the till surface should be undertaken with a ditching type bucket (i.e., no teeth) so as to minimize disturbance of the till surface. Some temporary lowering of the groundwater table may be necessary to minimize disturbance of the till surface prior to placement of the gravel bedding. Control of groundwater inflow may require pumping from a sump(s) located below the required depth of excavation. A temporary stream diversion may also be required depending on the design details for the new structure. Depending on the insitu conditions encountered, the use of a clean (i.e., no fines) granular bedding layer (e.g., 20 mm concrete stone) could be considered in place of the proposed Class A gravel. Such a granular layer should also assist with the groundwater control. The use of a non-woven geotextile should be used in conjunction with clean granular bedding, to prevent the migration of fines into (or through) the granular layer. The bedding layer (Class A gravel or clean granular fill) should be placed and compacted in lifts; maximum lift thickness should be compatible with the compaction equipment selected for use.

CULVERT INSTALLATION. As noted previously, the till surface elevation at the borehole locations ranges from a low of el. 15.08 at BH- 02 0.91 m to a high of el. 15.18 m at BH-01. In view 1.56 m. Based on the proposed inlet/outlet elevations provided, excavation to the underside of the loose and potentially compressible nature gravel bedding layer will be to about el. 1.0 m (+/-). We would therefore recommend excavating to the underside of the topsoil, it is recommended that the topsoil gravel bedding layer be removed from below the replacement culverts. The excavation should extend downward or to the till surface and outward a minimum horizontal distance equal (whichever is deeper). The gravel thickness can then be increased as necessary to the depth of new pipe bedding. Based on the conditions encountered at the boreholes, it is expected that approximately 700 mm (+/-) of Class A gravel bedding material will be required to establish the specified invert elevations, following topsoil removal. To ensure stable bearing conditions, the bedding should extend outward from the perimeter of the new culverts a horizontal distance at least equal to the depth of bedding placed below the pipesaccommodate any deeper areas. Excavation to the required level should be possible with conventional earth moving equipment (i.e., large backhoe or excavator). Final excavation to to/into the till surface stratum should be undertaken with a ditching type bucket (i.e., no teeth) so as to minimize disturbance of the till bearing surface. Some temporary lowering of the groundwater table may be necessary to minimize disturbance of the till surface prior to placement of the gravel bedding. Control of groundwater inflow may require pumping from a sump(s) located below the required depth of excavation. A temporary stream diversion may also be required depending on the design details for the new structure. Depending on the insitu conditions encountered, the use of a clean (i.e., no fines) granular bedding layer (e.g., 20 mm concrete stone) could be considered in place of the proposed Class A gravel. Such a granular layer should also assist with the groundwater control. The use of a non-woven geotextile should be used in conjunction with clean granular bedding, to prevent the migration of fines into (or through) the granular layer. The bedding layer (Class A gravel or clean granular fill) should be placed and well compacted in lifts; maximum lift thickness should be compatible with the compaction equipment selected for usea plate tamper mounted on a backhoe or excavator.