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Project: Mill Creek Wet Weather Storage

NOTICE - updated 6/12/24

  • Due to recent weather, the Contractor is anticipated to do excavation on Saturday, June 15th. Work will begin at 8 a.m. Additional Saturday work may be needed and will be communicated on a week-by-week basis.

  • The Clear Creek Trail temporary bypass is operational and will be for the remainder of the project.

Project Drivers and Benefits: 

JCW is providing storage for wet weather flows during major storm events, to provide capacity for continued growth and reduce the need for more expensive and disruptive downstream improvements.


What is happening with construction:

Excavation of the site is ongoing. Service water line and electric is being installed.

Construction Timeframe: 

Winter 2023-Summer 2025


6555 Vista Drive, Shawnee, KS 66218


Public Meeting and Open House held June 2023


to view materials and videos presented at the Open House and Virtual Public Meeting - June 13 & 14.

Mill Creek WWS-OpenHouse-PostcardNotification-20230517-Website.jpg
Wet Weather and Why it is a Concern

Wet weather—rain and snowmelt—can significantly increase flows at wastewater treatment facilities, creating operational challenges and potentially affecting treatment efficiency, reliability, and endangering the environment. As communities grow and current infrastructure ages, this can create additional stress on the system.

Sewage flows within a sanitary collection system are divided into two major categories: dry weather flows and wet weather flows.  

  • Dry weather flows represent all flows within the collection system on a typical day without precipitation. This includes sewage collected from customers along with normal groundwater that enters through defective pipe joints, connections and/or manhole walls.

  • Wet weather flows include the dry weather flows AND additional rain and snowmelt runoff that enters the collection system during a storm event. Johnson County has separate collection systems for stormwater and wastewater, but during large rain events, stormwater and increased amounts of groundwater can find its way into the wastewater collection system through defects within the system and private sewer laterals, as well as illicit building connections from stormwater sources such as sump pits and driveway drains. This results in wet weather flow that can be several times greater than flow during dry weather.  The additional flow dilutes the normal dry weather flow significantly.

While JCW continually works to fix defects within the system and eliminate these sources of flow into the system, there is no cost effective and practical way to remove all sources. Sometimes flows are still too high during peak wet weather, and collection system overflows can occur, overloading treatment plants and endangering the environment. One option to reduce peak weather flows (which is being planned for Mill Creek) are storage facilities (Wet Weather Storage) that temporarily store the excess flow and release it after the rainfall event, when downstream collection system capacity becomes available. 

Wet Weather Storage

JCW evaluated this and other alternatives and determined the storage option is the most cost-effective option for handing these wet weather flows. Constructing the facility eliminates the need for a two-mile parallel construction system that would be required to run along Mill Creek from the site all the way to the Mill Creek Regional Wastewater Treatment Facility.  It also reduces the magnitude and costs of future wet weather treatment capacity expansions at the treatment facility. 


Dry weather flows will bypass the storage facility, it will only activate during wet weather events, and only when the event is large enough to exceed the capacity of the sewer pipe. As such, the storage facility will be empty the vast majority of the time, and when it does activate it will store the diluted flows associated with wet weather.  

JCW, working with Johnson County Parks and Recreation District (JCPRD) and The Parks and Recreation Foundation of Johnson County (TPRFJC), has identified and procured property to place an underground Wet Weather Storage Facility for the Mill Creek Watershed and Mill Creek Wastewater Treatment Facility. The location will be just north of the JCPRD’s Vista Drive maintenance facility. While a large part of the facility will be underground, portions of it will be visible above ground. Working with the JCPRD, JCW will landscape the area to preserve the look and feel of the surrounding area. In addition, JCW and the JCPRD will collaborate on development of native plantings and habitat-enhancing features on the facility property. District access to the nearby trail system for maintenance activities will be maintained. 


The potential for odorous air in the facility will be mitigated by a ventilation and scrubbing system, along with an automated cleaning system to move material out of the tank when not in use.


Schedule and Engagement

The project is currently in the design phase.  

The construction timeline 

  • Anticipated contract for construction to be executed December 2023, and the work taking approximately 18 months. 

  • Virtual pre-bid meeting is on 10/11 and the site visit is on 10/12  


A public meeting and open house were held on June 13 & 14, 2023. To view the materials presented CLICK HERE


Keep checking back, updated information will be posted on this website. You can also sign up for notifications.


  • What is an Integrated Plan?
    An Integrated Plan (IP) supports strategic and financial planning by examining an organization’s existing resources and future needs. It is a thoughtful, equitable and collaborative resource that promotes efficiency and reliability, identifies high priority needs for capital investment, prioritizes human health and quality of life, and minimizes unnecessary social and environmental impacts.
  • What is JCW’s Integrated Plan?
    In 2019, JCW initiated a system-wide planning effort aimed at developing a long-term, prioritized infrastructure investment strategy that addresses wastewater needs and meets US Environmental Protection Agency and Kansas Department of Health and Environment requirements over the next 25 years. This Integrated Plan (IP) identified approximately $2.1 billion (in 2018 dollars) of projects that need to be implemented to meet these goals. JCW intends to continuously review and update the IP to address the community’s service needs as they evolve over time. Projects identified in the initial 25-year planning period include: Individual capital projects, such as those needed to build new treatment facilities and support regional growth; and Ongoing improvement initiatives focused on getting the most use out of our existing infrastructure. Now that the projects have been identified in the 25-year IP, JCW’s Integrated Plan Program is focused on providing the day-to-day staffing, communication, resources, and planning needed to implement the projects.
  • Why did JCW develop an Integrated Plan?
    Over the years JCW has made significant investments to improve and maintain our wastewater systems. However, aging infrastructure needs, increasingly complex water quality and regulatory compliance issues, wet weather capacity concerns, and growing service demands will continue to require major capital investments into the future. The Integrated Plan (IP) allows JCW to move forward with these critical projects in a way that minimizes impacts to our financial resources, staff, and customers. The IP approach is authorized by the Clean Water Act and provides municipal wastewater utilities like JCW with a framework to establish implementation schedules that meet state and federal regulatory requirements. By developing and implementing the IP, JCW can stay in compliance with the regulations while continuing to provide cost-effective services to our customers.
  • What are the goals of the Integrated Plan and associated Program?
    JCW developed the Integrated Plan (IP) to establish a prioritized and balanced infrastructure investment strategy that meets regulatory requirements and serves existing and future customer needs. The goals of the IP align with JCW’s mission to: Protect our environment, Serve our customers, and Enhance our communities. In doing so, the plan seeks to implement projects that solve the most critical infrastructure, environmental, and public health needs first, while allowing adequate time to develop a deeper understanding of future system needs. JCW is now focused on implementing projects through the IP Program. The goal of the IP Program is to provide JCW’s project managers, staff, engineering consultants, and outside contractors with the appropriate resources and tools needed to complete the identified projects on time and on budget.
  • How will the Integrated Plan improve our quality of life?
    The Integrated Plan (IP) focuses on implementing projects that improve water quality in our streams and rivers, provide important human health protections for our citizens, and maintain a high level of service for our customers. Specifically, the IP outlines JCW’s approach for: Rehabilitating old pipes, manholes, pumping, and treatment facilities to continue to effectively convey and treat wastewater for our existing customers. Resolving precipitation-related flow management challenges that currently cause occasional sewer overflows, building backups, and other unplanned discharges throughout the system during major wet weather events. Proactively preparing for system expansion and improvement efforts needed to support continued growth and redevelopment; and Beneficially reusing waste byproducts to minimize environmental impacts, reduce operating costs, and more efficiently use resources.
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