McHenry Wastewater Treatment Facility Central Pump Station

HR Green has completed several projects over the past twelve years evaluating and upgrading the City of McHenry’s Central Plant, South Plant, and Sanitary Sewer System. This work has been leading up to the elimination of the aging Central Plant. The main phase of the project, the McHenry Wastewater Treatment Facility Consolidation, upgraded the South Plant processes and created a new wastewater pump station next to Central Plant. A 24” Force main extension phase simultaneously completed an earlier force main project and allows the City to reroute all flow from the new Central Wastewater Pump Station to the upgraded South Plant. The consolidation and force main extension projects cost $33 million. The existing Central Plant is intended for demolition in the future.

The Central Wastewater Pump Station was an important part of the McHenry Wastewater Treatment Facility consolidation project. The pump station was designed to convey all of the flows the City’s Central Wastewater Treatment Facility treated to the City’s upgraded South Wastewater Treatment Facility. The flows range from average day flows up to 1.5-4 MGD to peak/storm flows up to 10 MGD. To accommodate this range of flows, the pump station was designed with three different size pumps. The station has one low flow pump (1-2 MGD), one medium flow pump (2-3.5 MGD), and two high flow pumps (4.75-11 MGD).

The average day flows are pumped to the head of the South Wastewater Treatment Facility through a 14” force main. While the peak/storm flows are pumped directly to the high rate clarification unit through a 24” force main. Normal operation is to have the low and medium flow pumps pump through the 14” force main and the high flow pumps pump through the 24” force main. There are interconnections to allow the low and medium pumps to pump through the 24” force main to either the head of the South Wastewater Treatment Facility or the high rate clarification unit.

The normal sequence of operations is to have a low flow pump to handle the average daily flows.  The medium flow pump can handle the normal daily peaks the low flow pump cannot.  If the medium pump cannot maintain the level in the Central Wastewater Pump Station, the high flow pumps are started to handle the peak/storm flow.