Middletown Wastewater System


Based on the results of a 1987 study sponsored by the Lake County Environmental Health Department, the Board of Supervisors adopted a moratorium on new septic systems and Assessment District 2-2 (AD 2-2) was established for the purposes of constructing a wastewater collection and treatment facility. The Middletown wastewater collection and treatment facility was constructed and started serving the downtown and surrounding residential areas of Middletown in 1992. In 1999, metered wastewater service to Harbin Hot Springs was added to the system.

Customer Statistics & Infrastructure

The Middletown Wastewater Collection and Treatment System currently include:

  • 492 Connections (808) Single Family Dwelling (SFD) equivalents. The system also accepts flow from the Harbin Hot Springs area.
  • Over 225 manholes and over 10 miles of pipe within the gravity collection system.
  • 3 Lift Stations and over 3 miles of force main piping conveying wastewater flows to the Middletown Wastewater Treatment Plant.


The Middletown facility was originally constructed 22 years ago for a much smaller community. Over the years, the number of customers has grown and the treatment plant and facilities are currently operating near capacity. The 12-month average change (Fiscal Year 2011 to 2012) in the Middletown customer base was less than 1%.


Expansion of the treatment capabilities is one of the focuses of the system. Other "efficiency improvements" and treatment refinements are being looked at to safely accommodate flows into the system for the existing customer base and reasonable future growth. In 2014 an application was made to the State Water Resources Control Board for project funding. To become eligible for low-interest loans or grants, a significant rate increase will be necessary. A preliminary design report was completed in September 2010.

The devastating Valley Fire of 2015 destroyed 140 connections to the system. To protect the collection system and treatment plant from excessive I/I and toxic materials, a lateral "cap and seal" project was completed in October 2015. As customers rebuild they will re-connect to the collection system.

The District is considering a move toward the development of a Network Hydraulic Model for the area. The model would provide a tool to better evaluate structure, capacity, and flows within the collection system. The model would also identify the areas within the collection system where infrastructure improvements are necessary including:

  1. Improvements to lift stations/force mains to safely convey additional flows, contribute to the capital improvement program (CIP) based on the development's percentage of use.
  2. Improvements to collection system piping/manholes to safely accommodate flows, contribute to CIP based on the development's percentage of use.
  3. Mitigate I/I to offset the additional flow impacts within key areas of the system.

Treatment Plant: Middletown

Type: Facultative Pond
Dry/wet flow: 0.128/0.24 million gallons per day  (MGD)

  • Collection area: Middletown (AD 2-2)
    Connections: 492 (pre-Valley Fire)
    Population: 1,193

Sanitary Sewer Maintenance Plan (PDF)