Excess groundwater and stormwater entering sanitary sewer collection systems from private sources through breaks, defective joints, tree root intrusion, cross connections, or porous walls is a common problem in Minnesota communities. This happens in two ways:
Inflow is extraneous/clear water entering a sanitary sewer system by direct connection from roof drains, basement sump pumps, street manhole covers, etc.
Infiltration is water entering a sanitary sewer system through joints and cracks in sewer lines from groundwater.
I/I is the total quantity of water from both inflow and infiltration without distinguishing the source.
Toolkits & Tracking:
See the League of Minnesota Cities' Sewer Toolkit: A Guide for Maintenance Policies and Procedures
The American Water Works Association's free Water Audit Software and manual provides the best management practice tools and guidance water utilities need to efficiently manage their supplies.
Water utilities report water conservation efforts and outcomes through the Water Conservation Reporting System as part of their annual report to MN DNR's MPARS (MN Permitting and Reporting System).
Another powerful free tool is the Alliance for Water Efficiency's Water Conservation Tracking [Cost/Benefit] Tool that can evaluate the water savings, costs, and benefits of conservation programs for a specific water utility. It includes a library of pre-defined conservation activities from which users can build conservation programs.
The League of Minnesota Cities 2019 inflow and infiltration model ordinance prohibits the discharge of clean water into the sanitary sewer system from sump pump connections, defective plumbing, and defective sewer service laterals. The ordinance also allows cities to develop an inspection program (citywide or at point of sale only), require corrections by property owners, and assess penalties for violations.
Create a program backed by ordinance for inspecting household/business gutters, foundation drains, sump pump connections, drain tile, lateral service lines, and/or inspections of city-owned sewer lines; report types of water system preventive maintenance; report drinking water observation well data to show a trend of source water levels (falling, stable, or rising). Report an adopted wellhead protection plan under BPA 6.3.
Make sewer inspections mandatory at the time of property transfers, street reconstructions; require repairs or provide incentives such as 50% reimbursement to property owners to make repairs or enact utility bill surcharges for owners who are non-compliant with I&I standards; report water system leak detection and water meter calibration, replacement and automation.
Report outcomes from I&I and water loss programs, such as miles clay pipes relined, # of disconnects, % clearwater reduction, GPD removed, water supply leaks (unaccounted/non-revenue water loss; should be under 5%), money saved at the wastewater treatment plant, capital costs avoided by being able to defer capacity additions.
Who's doing it
Bloomington - 3 star
Date action report first entered:
Date of last report update:
Year action initially completed:
. To date Bloomington has participated in three MCES I&I grant programs and received just under a half a million dollars for this war against I&I. It’s estimated that Bloomington’s I&I reduction efforts have removed roughly 63 million gallons of annual flow. At the current rate for wastewater treatment paid to the Met Council, the City realizes an annual savings of $157,000. Historic records show a reduction of over one billion gallons, or a 27% decline in annual sewer flow between 1993 and the present. While much of the reduction can be attributed to system wide conversion to low flow plumbing fixtures, a comparison of Bloomington’s annual water use and sewer flow historic trends shows a more pronounced reduction in sewer flows. The extra reduction in sewer flow rates is thought to be a result of the I&I reduction work. One additional benefit of the I&I improvements is that it adds 40 to 70 years of additional life to the affected infrastructure items.
• In 2017, Bloomington hired Barr Engineering Co. to re-evaluate the City’s Comprehensive Sanitary Sewer System Hydraulic Model. The work included evaluation of data from temporary monitoring throughout the city and recalibration of the sanitary sewer model. The analysis of the system indicated very low infiltration and inflow rates throughout the City.
• City Utility Crews now inspect about 200,000 feet of wastewater collection mains annually, via closed circuit television cameras. Any leaks or defects are recorded and scheduled for appropriate maintenance.
• In 2008 the City began a manhole inspection program to collect measurements and evaluate manhole condition. This information is used to schedule and prioritize needed maintenance, repairs, or replacement. Each year Utilities has budgeted roughly $300,000 for manhole rehabilitation within the Street repair project areas. The primary goal of this rehabilitation is to reduce I&I.
• Bloomington’s standard detail for wastewater collection manholes now includes installation of internal chimney seals. The chimney seals are routinely being installed on all manholes located within the City’s annual Street repair project areas.
• To reduce inflow, Bloomington prohibits the discharge of storm water, ground water, roof runoff, surface water, unpolluted drainage, unpolluted industrial cooling water, or unpolluted industrial process water to any public sanitary sewer per City ordinance (City Code Section 11.31(b)(3) see appendix D through G).
• As part of Bloomington’s Time-of-Sale Housing Inspection Program, Utilities Customer Service is notified whenever an illegal sump pump connection is discovered. Staff then works with the owner to eliminate this source of inflow.
• The City of Bloomington closely reviews new parking ramps and garage construction to assure that rainwater is directed to the storm sewer, not floor drains connected to the sanitary sewer.
• The City monitors MCES M500A wastewater flow rates in conjunction with precipitation events.
• The City evaluates lift station performance via SCADA records in conjunction with precipitation events.
• The City will continue to educate property owners on the need for eliminating infiltration and inflow (via public communication) and require the elimination of infiltration and inflow from private property.
• And finally, the City has used Cured-In-Place-Pipe, (CIPP) to repair damaged and leaking wastewater collection mains. Both short, spot-type repairs as well as full manhole to manhole repairs have been completed. (Between January 2003 and December 2009 over 47,500 feet of sewer mains were repaired with CIPP at a cost of just over $1.4 million.) The City continues to monitor TV inspection records searching for potential additional CIPP projects.
Beginning in 2009, the City began the process of updating and relining the City’s water pipes. Nearly all clay pipes in the city are now lined. The City recently developed an I&I program to address sanitary manholes - inspection & repair program. Street reconstruction projects replace sanitary sewer castings and wrapping manholes with I&I barriers. We are also implementing improvements to reduce system water loss (fire fighting protocols, metering public buildings & irrigation systems, etc.).
As part of the 2016 Street Improvement Project, the City implemented an ordinance (attached) requiring the inspection of private sewer lines. The City provides private sewer line inspections free of charge to homeowners to help residents meet the inspection requirement. Property owners that would rather use an alternative inspector have the option to do so, but must provide materials that prove inspection was completed by a certified plumber or inspector.
If the inspection results in a sewer line in satisfactory condition, no further action is required from the homeowner until the next street project affecting the local sewer main. If the inspection finds that the sewer line is in need of repair because of cracks, sags, and other sources of I & I, the homeowner must have the line repaired during the street project. The City helps facilitate repairs by offering financing options to help manage the costs of repairs.
Outcome measures/metrics/money saved:
In 2016, 135 private sewer lines were inspected as part of the project. Inspections exposed failures in 33 sewer lines, and repairs will be completed in conjunction with the street project.
As a result of serious inflow and infiltration issues and subsequent overflows in the early 2000s, the City of Duluth and WLSSD cosigned a decree in 2009 to "cease all wet-weather related sanitary sewer overflow... and resolve 18 separate overflow points" within the following 7 years. The decree was terminated after successful completion a year and a half ahead of time; the city has not experienced an overflow event since 2012, and regular maintenance is conducted to ensure the tightness of Duluth's sewer lines.
All properties in Golden Valley must be inspected for Inflow/Infiltration (I/I) issues and are required to be in compliance with the City’s I/I program before they can be sold or transferred (Section 3.31 of the City Code). I/I issues include clear water connections to the sanitary sewer as well as cracks or leaky joints in the sanitary sewer pipes. Property owners who apply for plumbing permits (when valuation exceeds $10,000), variances, subdivisions, or other planning actions from the City are also subject to an inspection. Properties that do not pass inspection are required by the City to complete repairs within 180 days (Section 3.31 Subdivision 5.B).
The City also conducts voluntary I/I inspections as part of its Pavement Management Program the year prior to reconstructing a street.
The City’s 2017-2021 Capital Improvement Plan allocates $600,000 to address Inflow/Infiltration in the I-394 sewer shed (Project # W&SS-074) and $35,000 to purchase portable sewer flow meters for monitoring inflow and infiltration in the sanitary sewer system (Project # W&SS-076).
The City tracks its progress with the I/I program by monitoring sewer flow at nine sites and monitoring groundwater levels at seven sites.
Outcome measures/metrics/money saved:
In 2017, after ten years of implementing the I/I inspection program, 55% of properties within the City were inspected for compliance with the I/I ordinance. As a result of the City’s program, in 2017, 310 disconnects were made and 47% of properties in the City were known to be compliant with the Metropolitan Council Environmental Services (MCES) directives regarding I/I.
According to a 2016 meter review and analysis published by the Metropolitan Council, between 2004 and 2015, Golden Valley reduced its peak flow from 12.9 million gallons per day (MGD) to 9.8 MGD (3.1 MGD or 24%) and reduced its I/I flow from 10.9 MGD to 7.8 MGD (3.1 MGD or 28%). These reductions have resulted in savings at the wastewater treatment plant of up to approximately $2,772,175/year (cost to treat water approximately $2.45/1000 gallons x I/I flow reduction of 3.1 million gallons daily x 365 days/year).
The City has routinely implemented inspections of private properties to ensure there are not prohibited connections of sump pumps and perimeter drains into the sanitary sewers. There are educational materials available and guidance is provided to citizens who are unaware of the ordinance preventing such connection and how the should be operated.
Televising of City sanitary sewer is conducted on a rotating schedule. Necessary repairs are made when sources of infiltration are identified in the sanitary system.
Outcome measures/metrics/money saved:
Since 2001 there have been over 800 improperly connected sump pumps and perimeter tiles that have been rerouted from discharging to the sanitary sewer.
We have an annual maintenance program to decrease inflow and infiltration into sewer lines. Annually, the City surveys 70,000 lines to determine which need to be re-lined.
To reduce losses in drinking water systems, we complete a city wide leak detection process that takes about three weeks to complete. This process allows the City to survey for water leaks throughout the City's water pipes and identify areas that need to be fixed. This reduces the City's un-metered water loss. Due to the losses being u-nmetered it is difficult to measure how much is lost through pipe leakage. However, because the City of Inver Grove Heights is able to complete the leakage detection and repair for the entire city on an annual basis, we estimate that the water losses are less than 5%.
For the last 25 years, the City of New Prague has budgeted for and replaced aging infrastructure throughout the City. This includes the replacement of all sewer and water lines. If the City is able to hold the course, within four years, all underground infrastructure will have been replaced City-wide to be current, modern piping.
In 2009, Rush City implemented an ordinance (attached) requiring the inspection of private sewer lines. Sewer inspections are mandatory at the time of property transfer and/or street constructions. The City provides private sewer line inspections for a reduced fee to homeowners to help residents meet the inspection requirement. Property owners that would rather use an alternative inspector have the option to do so, but must provide materials that prove inspection was completed by a certified plumber or inspector. If the inspection results in a sewer line in satisfactory condition, no further action is required from the homeowner. After 10 years, it has to be reinspected. If the inspection finds that the sewer line is in need of repair because of cracks and other sources of I & I, the homeowner must have the line repaired within six months. The City helps facilitate repairs by offering a loan program to help manage the costs of repairs. A penalty is added to the utility bill if repair is not completed within six months. The program also includes inspections of household/business roof drains , foundation drains, sump pump connections, drain tile, lateral service lines, and/or inspections of city-owned sewer lines.
Outcome measures/metrics/money saved:
As of April 15, 2020 -
484 Applications for inspections have been submitted (that’s over half of the properties in the City)
463 Sewer laterals have been inspected
82 Sewer laterals have failed and been fixed (most had roots in the pipe, which means that there are cracks so ground water can get into the City’s sewer system)
27 sump pumps/foundation drains have been disconnected from the City sewer and re-routed
3 roof drains have been disconnected from the City sewer and re-routed to the storm sewer
4 laterals have failed and not been fixed yet
In 2007 the City of Albert Lea launched Engineering Project 0701. This project targets 5,500 homes with potential I/I compliance issues. This project has reduced energy consumption at the WWTP and increased efficiency. This project is ongoing, there are 50 homes remaining in noncompliance with I/I standards.
The City of Granite falls has undertaken over the past few years I and I projects that have decreased water into the wastewater treatment plant.
The Following are I & I projects completed this year:
Minnesota Avenue, Washington Street to Baldwin Street, sanitary sewer was slip lined and all manholes repaired and relined (I & I was present from river and abandoned services).
Alley west of Prentice Street, from 8th Avenue to 7th Avenue. Sanitary sewer, storm sewer and watermain were all replaced. Cross connection had been indicated during smoke testing.
6th Street, from T.H. 212 to 12th Avenue. Replaced watermain and sanitary sewer and plugged catch basins that were thought to flow into sanitary sewer.
School corrected a MASSIVE cross-connection from their roof drains into the sanitary sewer.
All their roof water was draining into the sanitary sewer system. Since this was completed very recently we want to wait to publish data but so far it appears to have a significant decrease into the system.
The City has been active for the past 12 years in budgeting and executing a program for addressing inflow and infiltration within the sanitary sewer system. Initial efforts focused on televising and lining specific segments of pipe and sealing manhole structures that indicated the potential for, or were active in, allowing groundwater infiltration. As part of its inflow and infiltration mitigation efforts, flow meters were placed in areas considered most likely to produce higher sewer flows. Evaluation of collected data has allowed the City to televise and inspect specific sewer lines to monitor for both inflow and infiltration. In instances were inflow is suspected, the City approached the property owner to educate them on proper hookups for sump pumps and rain leaders. Subsequent years have seen a steady increase in the City's budget for inflow and infiltration mitigation and larger-scale projects to address issues throughout the City rather than being limited to a single area in any given year. Additional emphasis has also been placed on complete manhole sealing or rehabilitation to ensure that the structures do not contribute to the problem. The City also purchased a sewer camera truck to aid in the monitoring and management of the sanitary sewer system. The City is a participant in MCES grants for projects to mitigate inflow and infiltrations.
Mankato requires inflow & infiltration ("I&I") inspections at time of private property transfer. City Public Works staff has regular inspection & maintenance schedule for City sewer and water lines, including televising of lines. Wastewater Treatment Plant staff is urrently working with private engineering firm on establishing radio reading equipment on all municipal flow meters so trending of I/I can be recorded and guidelines and improvements can be established.
As described in the stormwater plan the city annually checks their sewer system for damage using cameras and other standard monitoring measures. This program includes a quarterly review of flow reports to identify critical I/I areas. The City is making annual investments to address I/I problems. These investments have included sewer main lining, sealing manholes, and the replacement of sections of sanitary sewer mains.The Living Streets program will also help identify critical I/I problems during construction projects.
With the new Living Streets program, extra care is taken to make sure there are updates to decrease the amount of storm run off infiltrating into sewer lines. This is done by increasing rain gardens to keep run off on site. This increased look at run-off occurs at all construction and reconstruction projects.
There is also grant money available to increase the umber of rain gardens along streets that are not being currently worked on.
The Citys current Capital Improvement Program (CIP) includes annual improvements to address illegal sump pump connections.
The Mounds View City Code - Title 907 makes is unlawful to discharge storm water into the sanitary sewer system. Connections from sump systems to the sanitary system were inspected within they last 10 years. Public Works Operators review sanitary lines via camera on a routine basis with a goal of inspecting approximately 1/4 to 1/3 of the city annually. During this inspection the operators will regularly note any areas where I/I is apparent as well as any services that appear to be discharging clean, clear water on a regular basis.
I/I is being addressed by an ongoing sanitary sewer lining project that lines appoximately 5,000 feet per year. The goal is to complete the lining of all vitrified clay tile pipe by 2028. Those areas exhibiting the highest I/I are being addressed first. In addition, as our street program continues those areas with sewer in poor condition are seeing the VCT replaced with PVC sewer pipe to eliminate the I/I issues experienced in the past.
Additionally, the City implemented its point of sale ordinance requiring homeowners to scope and repair their lateral sewer line at the point of sale, since January, over 65 homes have had their lines scoped and many repaired. Climate change has caused more frequent rain events with heavier amounts which, via infiltration can cause sewer back ups. This program will work to prevent that. Lastly, with the COVID-19 initial phase coming to an end, we will be starting to advocate voluntary scoping and lining and making available zero interest loans to homeowners who rehabilitate their lines.
The City of St. Anthony has completed a door to door inspection program aimed at reducing draintile and sump pump connections discharging to the sanitary sewer. Annually, the City replaces portions of its existing clay tile sanitary sewer infrastructure with PVC sewer and manholes to reduced I/I.
The city has done an inflow and infiltration reduction program. A sump pump ordinance has been put in place as well. In 2005, the city built a 2.5 million gallon equalization basin to contain excess flows when wet weather events occur. This excess water is fed back into the water treatment plant when flows subside.
When we do a street reconstruction project we televise private lines that run into the sanitary and require the home owner to re-plumb the system if their foundation tile is running into the sanitary system.
The city has done an inflow and infiltration reduction program. A sump pump ordinance has been put in place as well. In 2015 and 2016, the city budgeted $10,000 in I&I monitoring (televising, identifying, remediation). During the current Street & Utility Improvement project, two areas of I&I were identified and repaired.
Outcome measures/metrics/money saved:
Last year's televising did not produce any recorded area of I&I. As noted above, in June, during the construction of a storm manhole at 2nd Ave & Douglas, an overflow pipe was discovered and removed. Another area of I&I was identified and fixed.
Columbia Heights has been working on decreasing inflow and infiltration into the sanitary sewer system since 2004. The city replaced all low lying manhole covers and included an inspection of manhole structures and sewer mains. The City also completed a sump pump inspection program that inspected every property in the city and removed sump pump and roof drain cross-connections to the sanitary sewer. The City annually lines sewer mains in priority based on engineering studies (distance lined is limited by annual budget amounts). The City is also conducting smoke testing in problem areas to check service lines as well.
We do not have a strong issue with inflow and infiltration on our sanitary sewer system, and therefore it is not a focus of our CIP budgeting work. Nevertheless, during the course of infrastructure project, we specify water-tight piping systems for new installations and rehabilitation projects aim at this same goal. It is an inherent part of what we do as we engineer our systems.
Year action initially completed: Ongoing. Full official plan adopted by City Council began in earnest in 2020.
Completed: The City has an on-going program to tackle its inflow and infiltration issues, which include televising, sump pump programs (gutters and foundation drains), and smoke testing; with followup action to remedy any situations.
Outcome measures/metrics/money saved:
The overall goal of the proposed Sanitary Sewer Inflow and Infiltration Implementation Backup Project is to reduce the amount of rainwater and groundwater entering the sewer system. Removing this clear water will reduce the sewage handling and treatment costs, minimize sanitary sewer overflows and extend the life of upgrades made to the sewer system and treatment facilities.
Camered our existing sewer lines and cleaned our lift stations as part of our ongoing efforts to maintain our sewer system1/8/2016
Outcome measures/metrics/money saved:
All of the citys manholes have been inspected for infiltration. Those manholes that had infiltration were repaired by raising the manholes above the ground level in order to avoid rainwater infiltration. All of the city's sewer lines have been televised in order to seach for leaks and root infiltration. All of the problem areas have been repaired or on a schedule to be repaired. The final leak in the sewer line was repaired in October 2012.
New Ulm Public Utilities included the addition of sump pump regulations within its Commission Regulations
(Subd. 8. Sump pumps, water discharge, and inspections). In 2015, New Ulm Public Utilities Commission
approved additional wordage within the regulation and began sump pump inspections with the City of New Ulm
to identify illegal sump pump connections in homes. All homes within the city were inspected and those homes
found to be illegally connected to the sanitary sewer had reasonable time for correction. A fine was added to the
utility bill if corrective action was not taken by the homeowner.
New Ulm Public Utilities Wastewater Department owns a sewer inspection truck that allows them to utilize a
camera and software to conduct field inspections of sewer lines. The City of New Ulm’s Public Works
Department’s Sewer Jetter Truck additionally helps with this process for cleaning sewer lines for accurate
The City has established an on-going budget and program for decreasing inflow and infiltration into sewer lines and losses in drinking water systems. Please see the City's Comprehensive Plan Water Chapter, p. W30 on I&I.
Annually budgeted expense for sewer system I/I remediation issues to include televising of gravity sewer lines and manholes in project areas– repairs are initiated annually at these sites to minimize I/I issues. Our water distribution system is scheduled annually for a leak survey. Any deficiencies are corrected at that point.
Outcome measures/metrics/money saved:
Reduction in the gallons of clean water treated at the downstream wastewater treatment plant.
To reduce the amount of infiltration and inflow into the sewer system, the City:
1. Prohibits the discharge of any roof drainage, storm water, surface water or groundwater into the municipal sewer system.
2. Evaluates and upgrades the municipal sewer infrastructure to reduce infiltration and
inflow as part of road reconstruction projects.
3. Annually televises the sewer system to determine if and where repairs are needed.
4. Actively uses pipe relining and other trenchless technologies to rehabilitate segments of the sewer system.
The City has created Residential Sump Pump and Non-Residential Roof Drain Inspection Programs in response to the concern for infiltration and inflow. These programs are intended to result in a reduction in clear water entering the City’s sanitary sewer system. The City has developed strategies for reducing I&I, and corresponding Metropolitan Council Environmental Service surcharges associated sewage treatment of I&I.
The City of Woodbury has been in the process of pre-televising Road Rehabilitation Projects to inspect sanitary sewer lines of any Inflow/Infiltration issues that may arise. And using the information collected from the televising report to make necessary repairs and set the budget.