In 1952, the Borough of Pleasant Hills created the Pleasant Hills Authority by ordinance to plan and provide wastewater treatment facilities for the Borough of Pleasant Hills.

Between 1952 and 1959, the service area of the Authority was expanded to include portions of the Boroughs of Baldwin and Whitehall and portions of the Township of South Park. Additionally, the sewer system to convey and treat the sewage for these municipalities was planned and constructed. The sewer system included approximately 11.5 miles of interceptor sewer, Lewis Run Pump Station and a 3.0 MGD sewage treatment plant located on Cochran Mill Rd in South Park Township. In 1961 and 1965, the service area was expanded to include portions of the Municipality of Bethel Park and portions of the Borough of Jefferson.

In 1982, the Sunrise Drive Pump Station was constructed to replace a length of interceptor sewer that was crushed and inoperable.
Because of the population growth, additional commercial development and increased regulations, the Lewis Run Pump Station and sewage treatment plant were expanded and upgraded from 1988-1990. The capacity of Lewis Run Pump Station capacity was increased to 4.1 MGD and the sewage treatment plant capacity was increased to 5.0 MGD.

In 1999, chlorine gas disinfection system was replaced with an ultraviolet light (UV) disinfection system to comply with stringent new regulations and to remove the hazards of operating with chlorine gas.

From 2017 to 2020, the treatment plant was upgraded to increase the wet weather treatment capacity from 12.5 mgd to 25 mgd to prevent sanitary sewer overflows.  This was accomplished by changing how the sewage flows through the plant and upgrading the majority of equipment in the plant.  The following changes were made to the plant:

• Added Headworks Building with 2 mechanical bar screens to process 12.5 mgd and 4 raw sewage pumps.
• Modified existing headworks facilites to be used to process wet weather flows from 12.5 mgd to 25 mgd.
• Installed new flights in all primary clarifier tanks
• Installed a flow control chamber to split the flow between the first and second stages
• Installed new fine bubble aeration with new blowers for both first and second stage aeration tanks
• Modified 3 first stage final clarifiers with launder covers and stamford baffles to facilitate settling and prepare flow for UV Disinfection
• Converted 2 fist stage final clarifiers to be wet weather final clarifiers
• Installed new second stage pumping station
• Replaced arms in second stage final clarifiers with stainless steel
• Installed additional UV Disinfection system to handle increased flow.