Engineers who investigated last July’s sewage flooding in Barr Manor have recommended a public awareness program for lot drainage improvements.
Edmonton-based DCL Siemens also suggests Barrhead Town Council take steps to ensure sump pumps discharge to the surface away from homes.
Sump pumps should not be connected to the sanitary system, say the engineers.
Other recommendations for the Town include:
•A request for all homeowners to have backwater valves installed and serviced regularly;
• Sealing all manholes in low-lying areas; and
• Creating an incentive program tied to drainage improvements.
“If the Town is able to educate the general public and take an active lead role in solving the inflow and infiltration problem, then hopefully the incidence of sewage backups will diminish to the rarely category,” the firm says in its eight-page report.
DCL Siemens launched its investigation after several properties – primarily the basements – were flooded by raw sewage in the wake of last summer’s heavy rainfall.
Dean Rau and Veronica Properzi were among those affected.
On the night of July 23 they say effluence streamed in through the floor drain and toilet in their property at 5509 58 Avenue in Barr Manor.
Last Monday, Properzi and two other local residents, Sandra Cober and Dennis Sheridan, were present when the engineers’ findings were delivered at the Town council’s regular meeting.
Two DLC Siemens representatives were present to speak on the report: area field manager Drew Fellers and project engineer Kevin Fitzgerald.
Fellers and Fitzgerald said the sanitary system had been overwhelmed during the rainfall.
“Storm water is entering into the sanitary system, which is not supposed to happen,” said Fellers.
He added that rain leaders off the side of a house were draining into weeping tile tied into the sanitary system; this was not the desired way to get rid of storm water.
“Are you saying that’s the major cause?” asked Mayor Brian Schulz.
“That’s what everything points to,” said Fellers. “What happens when you have a large rainfall event is that you get the initial downfall and it takes about half an hour for water to get into weeping tile and sump pumps and work its way into the sanitary system. It overwhelms the sanitary system.”
After this, backups are prone to occur, said Fellers.
Reading from the report, Fellers said DCL Siemens conducted a topographic survey to determine the elevations of affected houses and sanitary sewer mains. It also estimated the elevations of the sewer service as it left properties.
“Our survey revealed that the home located at 5706-53 Avenue is situated very low on the lot and is the lowest of all the homes along the alley,” the report said.
It added that a survey of the affected residences in Barr Manor revealed that homes on the south side of 58 Avenue between 55 and 56 Street are situated lower on their lots than the homes on the north side.
“Again, any surcharge of the main would cause sewer backup along the south side service lines,” the report continued.
“Shortly after the storm event, water was observed approximately halfway up in the manholes located at the intersections of 55 and 56 Street on 58 Avenue. The high surcharged water level in the manholes, when delineated on the profile of the street, shows the residences on the south side of 58 Avenue would have had sewer backup if they did not have backflow preventers in place.”
The report said the storm impacted the sewage collection system in several different ways. Collectively, this is known as inflow and infiltration.
Studies found that rainfall enters the sanitary system through low-lying sanitary manholes soon after a storm hits.
Residences with poor lot drainage collect proportionately more rainfall around the foundation, which enters the weeping tile system, the report states. In older neighbourhoods, the weeping tile is generally connected to the sanitary sewer, which was a common practice. These additional flows could take about 15 to 20 minutes to enter the main sewer system.
Other findings include:
•Properties with poor lot drainage and sump pumps connected to the sanitary sewer system would start impacting the system in 25 to 40 minutes from the start of a storm;
•Properties with good lot drainage with weeping tile or sump pumps tied to the sanitary sewer system could start to impact the sewer system within 30 to 60 minutes from the onset of a storm;
•Normal sanitary flows, combined with rainfall, may overload the piping system;
•Overland seepage through foundation cracks or joints would begin to occur within 20 to 30 minutes of the storm’s onset; and
•Residences without protective sewer backwater valves in suspect areas would be the first to experience sewage backup.
The engineers say the best way to protect homes is to curtail non-sanitary system flows. This would involve waterproofing manholes in low-lying areas; connecting weeping tiles to sump pumps; ensuring sump pumps discharge onto the surface away from the house; improving lot drainage; and directing roof leaders away from basement walls.
“The sanitary sewer and treatment system is there for the purpose of capturing and treating sanitary sewage flows, not to catch and convey rainfall,” the report says.
DCL Siemens concludes that the sanitary sewer collection system meets all Alberta Environment design criteria. However, it was not designed to deal with problems brought on by heavy rainfall.
Coun. Madelaine Wessel said she liked the idea of sealing manholes and wondered how many were in the area. She was told about three.
Cober expressed concern about a passage in the report that stated “any minor surcharge in the main from extraneous flows would cause sewer back-up along this service line.”
“When I see the word minor it adds a lot of stress,” she said.
She said in the last eight years she had experienced flooding three times following heavy summer rainfall. In the previous 12 years, her property had not been affected.
“To have the word minor in the report is going to make us stressed every day. I’m going to worry all year long,” she said.
Schulz said Cober made a good point.
“I agree minor is not very comforting,” he added.
Fellers and Fitzpatrick agreed the passage was improperly worded and said the report would be amended with the word “unexpected” replacing “minor.”
Town council agreed to send the updated report to Public Works, so the department could look at it and do a cost analysis.
Afterwards, Cober said she needed time to digest the contents of the report.
Schulz said DCL Siemens had not pinned the sewage flooding problem on one area.
“It is a problem that can probably be solved with some landscaping and with some honesty as far as whether your pipes are hooked up to the sewer,” he said. “The public must know that it is putting a tax on our sewer system. We can’t afford to put in a lot of bigger pipes than we have now.
“What we have now should accommodate everything that the weather seems to throw at us, but with the soil settling and this and that we need the homeowners to help out with their landscaping.”
Schulz said the Public Works department would look at issues like sealing manholes, as recommended by the engineers.
“We are going to do everything we can to help alleviate the possibility of this happening again,” he said. “The Town is committed to that.”
