The Job
The Round Valley Reservoir, in Clinton Township, New Jersey is a 2300 acre man-made drinking water reservoir serving extensive portions of New Jersey. It was constructed by damming up two openings in a naturally-curved mountain.
As part of a dam upgrade project, a 1400LF, 36″ inner diameter LLO pipe needed to be grouted to place it out of service.
The Challenge
The pipe had been previously blind flanged, 180′ below the lake surface. There was a single, 12″ riser pedestal. There were numerous significant challenges to face, including:
- 2GPM residual leak from the blind flange buried in 15′ of lake floor debris
- inability to push sacrificial pipes more than 500′ up the pipe
- remote site with limited ready mix service
The Solution
CJGeo worked with the general contractor, diving subcontractor, sacrificial grout pipe installation subcontractor, geotechnical and civil EORs, and the owner, to develop a single stage grouting plan to place approximately 350CY of 68lb/cuft cellular grout from the downstream end.
Venting was achieved by installing a 4″ removable vent pipe from the pedestal riser, 180VF to the lake surface, terminating on a barge. Since there was only one opportunity to do the job correctly, CJGeo had two fully staffed grout plants onsite, and had all cement and mix water staged in onsite storage prior to the start of grouting to avoid any material logistics disruptions affecting the work.
CJGeo placed the 68lb/cuft grout over a period of a few hours, leaving an intentional air pocket at the high end to capture infiltrating lake water long enough for the grout to set prior to seeing lake head.
