Kent Collins, deputy head of the Facilities Engineering Services Section, wrote this column.
The Main Ring ponds were built back in the 1970s to provide cooling for the Main Ring and the Tevatron systems. By design, these were 24 distinct 7-foot-deep, 65-foot-wide ponds that used a pumping system to move water from one pond to the next and to indirectly cool equipment at the same time.
After 35 years, these ponds have filled in with silt from shore erosion and dying vegetation. The pumping and cooling systems have deteriorated considerably and require frequent service and attention. They’ve clearly led a full and productive life, and now they deserve to retire.
When we turn off the Tevatron, we should also turn off the circulating pumping system to reduce costs and maintenance efforts. But it’s not that simple.
The pond cooling loads will go away when the Tevatron shuts off this fall, except for a small area in the F Sector, the west section of the Main Ring. The initial plan uses the closest pond for this cooling, and we will use the Industrial Cooling Water system to make up for that pond’s evaporative losses.
The sump pump system must also remain in service until the Main Ring tunnel system is decontaminated, decommissioned and emptied. The current sump pumps are also integrated with the pond system, which has its own ecosystem.
The ponds provide a habitat for fish and other wildlife. The ecosystem in the area has adapted to a very shallow underground water table, which we must consider. The pond system also carries rain and snow melt water from the area, but only when the ponds are full and able to overflow toward the eastern outlet near DZero.
Without the continuous flow of heated water, the shallow ponds will quickly change character, and they will be dominated by reeds, cattails and other vegetation.
Fermilab is now working to develop a plan for an orderly transition to shut down the Tevatron surface water cooling system. While we aren’t sure how the landscape will change, we do know that it will. But it won’t happen overnight.