RiverRenew Lightweight Fill

Alexandria, Virginia

The Job

The City of Alexandria’s RiverRenew project is its largest in history. The project includes installation of new interceptors, and a large CSO/conveyance tunnel.

The Challenge

A pile-supported, concrete-encased interceptor needed to be backfilled. Due to the pile support capacity, the maximum allowable density of the backfill was 90lb/cuft.

The Solution

To bring the average backfill density to 90lb/cuft, CJGeo proposed filling between the SOE & concrete encasement with 30lb/cuft CJFill-High Permeability (HP). CJFill-HP has very high permeability, so reduces buoyancy when saturated when compared to other lightweight fill materials. CJGeo successfully filled between the concrete encasement and SOE with 145CY of CJFill-HP18. The placements was done in a single, 6′ deep lift in less than an hour.

The use of very low density material then allowed the client to backfill on top of the structure with normal unit weight material while maintaining the average 90lb/cuft density through the full depth of the fill column.