General Nile Company for Roads & Bridges/Dott Services JVTANROADSTARAKEA-ROMBO-MKUUUpgrading Project,Tender No: THQTB/DD/01/004/2004/2005CLARIFICATIONS & CONFIRMATION FOR CONTRACT NEGOTIATIONS

PIPE CULVERT CONSTRUCTION PROCEDUREConstruction works for pipe culverts Installation shall be carried out upon completion of the following activities.a) Top soil strippingb) Clearing and grubbingc) Setting outd) Completion of Cut and Fill sections (Profile).e) Relocation of existing natural drainagef) Detours (as may be necessary)g) Protection of existing structures and utilities Making temporary traffic diversion at pipe culvert location at allow work be done full width.

Excavation pipe culvert locationThis shall be carried out to the required widths and depths to the invert using appropriate tools and equipment for excavation in both soft and hard materials. Adequate knowledge of the subsurface conditions shall be put into consideration for any type of excavation.

Spoil PlacementWhere excavated material does not comply with the requirements for backfilling material as specified hereinafter or is surplus to backfilling requirements, such excavated material shall be removed from the site and used for rehabilitation of borrow pits or at other places as directed by the Engineer

Material suitable for use in the works, however, shall be used as prescribed by the Engineer.

DewateringWhere surface water or groundwater conditions exist, the site and trench shall be dewatered using appropriate tools and equipment. Placing and filling the foundationThe bottom of excavation shall be filled with 300mm gravel and compacted to the required specifications.

Casting concrete beddingThe foundation shall be replacement with selected materials, such as concrete, sand, gravel, crushed rock, slag, or suitable earth backfill or as may be recommended by the Engineer prior to pipe culvert installation.

Pipe culvert placement and JointingUnless otherwise instructed by the Engineer, the laying of culvert sections on the prepared bedding shall be started at the outlet and with tongue end pointing downstream and shall proceed toward the inlet end with the abutting sections properly matched, true to the established gradient. Pipe joints shall be sealed to prevent infiltration of soil fines or water. Casting concrete surrounding Excavation for Toe beam, Apron, head wall and wing wallsThis shall also be carried out to the required widths and depths using appropriate tools and equipment for excavation in both soft and hard materials. Adequate knowledge of the subsurface conditions shall also be put into consideration. Placing and filling the foundationThe bottom of excavation shall also be filled with 300mm gravel and compacted to the required specifications. Casting concrete blinding for the apron Assembling and placement of reinforcement for the toe beam, apron, head walls and wing walls. Supporting the formwork and strengthening Casting concrete for the toe beam, apron, head walls and wing walls. Maintenance and curing of concrete with water shall be done to an appropriate period of time. BackfillingAfter the solidarity period as per the specifications, backfill shall be done. The backfilling material shall be approved excavated material or imported selected material in accordance to the required technical specifications.The material shall be watered and compacted to provide a firm earth cushion or handled accordingly as may be instructed by the Engineer. Then shall remove the temporary diversion and open the water channel and outfall channel to let the flood water and finish the whole structure. Opening to TrafficAs may be determined by the Engineer, the completed section shall be opened to public traffic.