REDUCING INFLOW AND INFILTRATION: HELPING TO SAFEGUARD AGAINST SEWER BACKUPS AND KEEP WATER SUPPLIES SAFE
Inflow and Infiltration Facts and Frequently Asked Questions
Inflow and infiltration are terms for the ways that clear water and stormwater make their way into sanitary sewer pipes and eventually get treated, unnecessarily, at wastewater treatment plants.
Typical inflow sources are water from roof downspouts, basement sump-pumps, or foundation drains connected directly to a sanitary sewer pipe. Inflow occurs in direct proportion to rainfall.
Infiltration occurs when groundwater seeps into sewer pipes through cracks, leaky joints, or deteriorated pipes and manholes. Inflow is by far the larger problem, and occurs in direct proportion to rainfall.
Inflow and infiltration are issues within many metro area communities because this water floods the sanitary sewer system during storms and can contribute significantly to sewer backup in homes and send clear water to be unnecessarily treated at the wastewater treatment facility.
Financing Options Available to Correct Inflow and Infiltration Issues
To help property owners with their sanitary sewer needs, the City Council, in partnership with the Urbandale-Windsor Heights Sanitary Sewer District, the Neighborhood Financing Corporation and Polk County, has developed a financial loan program, with a portion that is forgivable up to 50%. In 2010, the Council adopted a program to help homeowners, through their local city, to defray the cost of disconnecting sump pumps and foundation drains, and to repair private sanitary sewer pipes connecting to publicly-owned sewer pipes. The loan program will began September 1, 2011. The program will help with sanitary sewer replacement or sliplining, sump pump disconnection (from the sanitary sewer) and foundation drain separation. Interested property owners apply for a loan to do the work through the Neighborhood Financing Corporation, with a portion of the total loan being forgivable. The amount that is forgivable depends on the property owner’s income. Also, the property owner must be able to credit qualify to participate in this program. (More information on subsequent pages)
How do I know if I have an inflow/infiltration problem?
A home owner can have an inspection done by a plumber to determine if sump pump(s) and/or foundation tiles drains are connected into the sanitary sewer. Additionally, it might be possible to determine by looking in your basement, to see if your sump pump is connected to the floor drain or connected to the sanitary sewer vent stack/pipe. If your footing drain tile is connected, it is not possible to tell without the assistance of a plumber. A sump pump can contribute 7,200 gallons of clear water to the sanitary sewer system in 24 hours, the equivalent of the normal daily flow from 26 homes. State law prohibited these connections in the 1970s, but many remain.
Are there other ways clear water can enter into the sanitary sewer?
Yes, through the collapsing and disintegration of bituminized fiber pipe commonly referred to as “Orangeburg” sewer pipes. If your Orangeburg line is collapsing, you have inflow and infiltration problems.
What is the benefit of addressing inflow and infiltration?
The three main reasons include – safeguard against sewer back up, help keep sewer costs reasonable and help keep our drinking water clean.
Safeguard again sewer back up:
Even if you have not had a sewer back up, it remains a possibility. With changing climate patterns, we are receiving rain in different ways than we have in the past. There has been a significant growth in downpours, instead of light rain and heavy rainfalls have increased. This is when backups are most likely to occur. Nearly every year Windsor Heights receives reports from homeowners complaining about water in basements when it has never happened previously.
Help keep sewer costs reasonable:
Inflow and infiltration takes up fixed capacity in large regional sewer pipes (interceptors) that are needed to convey wastewater through the sanitary sewer system. It can also be costly to our community; once clear water gets mixed in with wastewater, communities are charged for the treatment of all the water.
Why can’t we just continue to have clear water go into the sanitary sewers?
Sending clear water to the sewer plant is cost prohibitive and not a good way of handling the inflow and infiltration problem, for a variety of reasons. First, it is not an environmentally sound practice. Stormwater should ideally be captured where it falls, enabling it to filter through the ground and recharge aquifers for clean drinking water. Second, creating additional capacity for the treatment plant would cost millions of dollars. Additionally, to expand pipe capacity means pipe replacement, which is also extremely expensive and can cause streets and right of ways to be torn up for months. The increased hydraulic pressure also puts more stress on the pipes, wearing them out prematurely.
Inflow during major rainfalls may exceed current sewer capacity, causing system back-ups into homes and overflows into local creeks and rivers, from which we draw our drinking water. This puts public health at risk and violates state and federal regulations. The monitoring of wastewater flows shows a direct correlation between precipitation and the volume of flow through the sanitary sewer system. Thus, customers are being charged to treat water that does not need to be treated. Customers also pay, through the rate structure, for sewer back-ups, whether they experience them personally or not.
What is Orangeburg?
Orangeburg is bituminized fiber pipe made from layers of wood pulp and pitch pressed together. The name comes from Orangeburg, New York, the town in which most Orangeburg pipe was manufactured. The pipe is made of a combination of cellulose and asbestos fibers impregnated with a bituminous (coal tar) compound.
When Was “Orangeburg” Pipe Used?
There are no specific records to determine the exact time span for the use of this type of pipe, however, Orangeburg pipe was commonly used in housing construction from the mid 1940’s to the early 1970’s. After that, PVC piping became the most commonly used material for sewer line construction. If your home was built during this time frame and the sewer has not been replaced, there is a greater likelihood that you have Orangeburg pipe. There is, however, no consistent pattern of building with or without this type of pipe. In order to be certain, you can have your pipes inspected (or televised) by a licensed plumber.
Why Does “Orangeburg” Fail?
Though sewer pipes of cast iron or plastic also fail, the preponderance of failures of sewer pipes over the past twenty years or so has been associated with bituminized fiber piping (Orangeburg). The system may fail for several reasons:
- The bedding around the piping may shift or be disturbed over time, causing the pipes to shift and break apart (generally at the joints).
- Tree roots may invade the pipes, usually at the joints, and loosen or break apart pipe sections and restrict flow.
- The piping material itself may deteriorate over time. As the material deteriorates, it flattens due to the earth pressure around it and loses its circular cross section. This circular shape is particularly needed at the bottom of the pipe where most material will flow.
- The deterioration may also be caused by the effects of improper disposal of cleaners and solvents. Since the piping material is held together with bitumen, any type of solvent, paint thinner, mineral spirits or adhesive cleaner dumped into the pipes will cause deterioration. Especially where laminated piping is concerned, this has the effect of weakening the pipe bottom, causing it to bow upward from the bottom due to earth pressure and reducing (or eliminating) the ability of the pipe to properly flow. Ironically, in this failure mode the interior layers fail first and the pipe then continues to “rot” from the inside out. Inspectors have seen Orangeburg piping which still maintained a circular outer shape but with an interior cross section out of round and failing. The inside-to-out failure mechanism seems to be particularly unique to Orangeburg bituminous fiber piping.
The City Council, working with the Urbandale-Windsor Heights Sanitary Sewer District and local engineers, determined that the most cost-effective solution would be to remove stormwater from the system by disconnecting sump pumps and foundation drains connected to sanitary sewers, and by repairing leaky sewer pipes. The first step is the City side of the sanitary sewer system. This work begins this summer (Summer 2011) when sliplining the City’s sewer pipes is undertaken. However, reducing inflow and infiltration problems on the City side of the sanitary sewer system, only addresses approximately 40% of the problem. The remainder of the problem is coming from the private side – the property owner side. This requires action to be taken by individual homeowners to reduce inflow and infiltration.
Helping Property Owners
In 2010, the Council adopted a program to help homeowners defray the cost of disconnecting sump pumps and foundation drains and to repair private pipes connecting to local sewer pipes. The loan program will begin September 1, 2011.
The program will help with sanitary sewer replacement or sliplining, sump pump disconnection (from the sanitary sewer) and foundation drain separation. Sliplining is one of the oldest methods for trenchless rehabilitation of existing pipelines. Sliplining is used to repair leaks or restore structural stability to an existing pipeline. Sliplining is completed by installing a smaller, “carrier pipe” into a larger “host pipe,” grouting the annular space between the two pipes and sealing the ends. Sliplining has been used since the 1940’s.
What kind of assistance can I expect?
Following is a table to help you figure out what portion of a loan could be forgivable.
|Median Income Limits||$8,500 Estimated cost of repair/replacement|
Family of 2
|0 - 50 % of median income||50.01 - 80% of median income||80.01% + of median income|
|Up to $29,300||$29,301 - $46,850.||Over $46,851|
Family of 4
|0 - 50 % of median income||50.01 - 80% of median income||80.01% + of median income|
|0 - $36,600||$36,601 - $58,550||Over $58,551|
Where can I go for help?
For information on the loan program, contact Neighborhood Financial Corporation at 515-246-0010, 1912 6th Ave. Des Moines, IA 50314-3331.
Are there internet resources I can search?
You can internet search Orangeburg to research more information. There are also several videos on youtube about Orangeburg.
This material presents information on bituminous fiber or “Orangeburg” pipe gathered from records, construction literature, building and plumbing codes, and other sources of empirical data. Material herein is not warranted to be consistent for all locations and addresses. The intent is to help people understand the bituminous fiber pipe (“Orangeburg”) problem and present information as potential source of reference in addressing sewer drainage problems.