Why Expand the Plant?

Expanding the wet weather treatment capacity by enlarging existing plant facilities has been a cornerstone in ALCOSAN’s strategy for reducing sewer overflows. This strategy dates to the 1996 Act 537 Plan which envisioned phased plant expansion and upgrades to reduce overflows.

As a result of expanding, the current capacity of 250 million gallons per day (mgd) will be increased to 480 mgd by the end of 2025 and to 600 mgd by the end of 2027. This additional capacity will help reduce the number of overflows caused by excess stormwater entering the system.

About the Expansion

The expansion of ALCOSAN’s treatment plant was designed in two major phases. Phase 1 was completed in 2005 and ALCOSAN has begun phase 2 which is expected to be completed in 2027.

Phase 1 included the construction of new operation and maintenance facilities and the upgrading and expansion of the main pump station. This station lifts the wastewater from ALCOSAN’s deep tunnel conveyance, or transport system to the surface for treatment.

Phase 2 of the treatment plant expansion focuses on wet weather treatment capacity to allow more sewage to be captured and treated, thereby reducing overflows during periods of rain and snowmelt. 

2 phases of plant expansion.


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Phase 2 Will Include

  • Wet weather pump station to provide 120 mgd of additional wet weather pumping capacity.
  • Wet weather preliminary treatment to provide for upgraded capacity of 600 mgd.
  • Two additional primary sedimentation tanks to provide 600 mgd of capacity.
  • The addition of two final settling tanks to boost secondary treatment capacity to 295 mgd.
  • New secondary treatment and wet weather treatment disinfection facilities using sodium hypochlorite and dechlorination to protect aquatic life in the Ohio River.
  • Construction of a new primary discharge outfall and using the existing outfall for wet weather.

Phase 1 Included

  • Expansion of primary (physical) and secondary (biological) treatment capacities.
  • Conversion of the gaseous chlorine disinfection system to safer liquid sodium hypochlorite.
  • Upgrading of the biosolids processing and handling facilities.
  • Extensive odor control system upgrades.
  • Various upgrades to the plant’s electrical system.
  • Expansion of the treatment plant capacity from 200 mgd to 250 mgd. 

Plant Expansion Projects

Quick Links

Clean Water

Assistance Fund

Are You Eligible?
Stormwater protection with native plants and gravel
ALCOSAN’s GROW Program Announcement

Grants available up to $10 million per project.

See Press Release for Details