Plant Upgrade

In 2011 the Water Pollution Control Division began a major rehabilitation of the treatment plant. Many of the Plant's facilities were 60 years old and in need of repair or replacement. That upgrade was completed in 2015.    

Project Goals:

  • Protect public health and the environment
  • Avoid costly emergency repairs to infrastructure
  • Expand operational options to improve efficiency
  • Add redundancy to improve safety & reliability

The project was funded through a loan from the State Revolving Fund. See below for more details about the project.

Project Overview

The areas in red below are new facilities constructed as part of the upgrade.

Click the arrow at the right to see more.

Overview of plant detailing new construction


The original headworks and influent pump station was constructed in 1939 and was not updated until this upgrade completed in 2015. The concrete was deteriorating, and the pumps were old and inefficient. Because of the limited flow capacity design of the original headworks, the pumps could not be upgraded. During heavy storms, the headworks would flood, coming dangerously close to electrical boxes. For safety and efficiency, the headworks needed to be completely replaced. The new headworks includes a new screenings removal facility that removes rags and solid objects to improve downstream pumping efficiency, to increase personnel safety and to protect downstream equipment.


Grit Facility

The new grit facility was installed to improve efficiency and to extend the life of Plant mechanical equipment. Sending heavy inorganic material such as sand and pebbles through both the wastewater and solids process streams is very inefficient. Grit falls out and fills tanks up to 25% capacity, and then the process has to be taken out of service and cleaned - a time consuming and expensive procedure. In addition large particles score the inside of pumps, valves, pipes, and other equipment and diminish their useful life. The new grit removal capability has made a noticeable difference in the efficiency of Plant equipment.

Grit Facility

Primary Clarifiers

Primary Clarifier #1 was built in 1938 and Primary Clarifier #2 was built in 1947. The concrete in both tanks had deteriorated from constant exposure to wastewater. The mechanical equipment was at the end of its useful life, and the two primaries were severely overloaded during wet weather. Primary treatment improvements were to rehabilitate Primary Clarifiers 1 and 2 to repair the damaged concrete and to increase the useful life of the structures by 40 years. In addition, a new primary clarifier was built to provide adequate primary treatment during wet weather flows.

Primary Clarifier

Fixed Film Reactor

A new Fixed Film Reactor (FFR) was constructed to replace the older one that was at the end of it's service life. In addition, all new piping and pumping were installed as well as a new biofilter to help control odor from the new FFR.

Fixed Film Reactor after construction

Flow Equalization

Before October 2011, in really heavy rain events, the Plant could blend effluent from the primary clarifiers with the effluent from the secondary clarifiers and discharge the blended water. After October 2011, that was no longer permitted by the State Water Board. In 2010, the Plant had about 1.1 million gallons of storage, but 3.8 million gallons was going to be required. The upgrade included the construction of a new 3 million gallon lined storage lagoon to store wet weather flows. We also rehabbed three existing tanks to reduce costs. The processes were automated to reduce staff attention and lower operation and maintenance costs.

Equalization Pond after construction

Electrical Upgrade

In 2010, the electrical system for the Plant was quite limited. The main switchboard did not provide isolation between breakers. The 12kV/480 volt transformer was ungrounded. The voltage drop prevented extension of the 480V system to new facilities. Underground duct banks had no spare conduits. Aging equipment was unreliable and unsafe, and there were frequent electrical failures and surges that damaged equipment. The electrical system upgrade replaced the obsolete main switchboard and MCCs with new equipment. It simplified isolation of the electrical system components to improve safety. It modernized the Plant control system to improve function and reliability of the Plant. It also included an upgrade of the emergency generator and generator fuel storage facilities.

Main Electrical Building

Administration, Control and Laboratory Building

Administration, control and office space were inadequate for staff levels in 2010. The laboratory was inadequate for current regulatory requirements, and there was no lab storage space. There was no dedicated work area for Environmental Services Pretreatment staff. The building overall was non-compliant with ADA. With the upgrade, the administration and control areas were expanded for current staff levels. The complete facility was upgraded to make it ADA compliant. The lab was upgraded to enable the use of modern equipment required to perform mandated analyses. A new dedicated work area was created for Environmental Services staff. The existing building was gutted and brought up to code. A reception area and conference room were built, and a completely new laboratory was built. We're proud to say that the new building is LEED Silver certified.

Picture of the new admin building