Do
you ever wonder what those large pipes by the side of the road are for?
Typically culverts are made of metal and concrete.
(image from http://www.specialtysupply.com/storm-water-management/)
These
are culverts and used for allowing water to pass under a road, driveway, or
embankment. Without them, we would literally be in deep water during the next vigorous
rainstorm. Part of our ability to maintain a safe and comfortable lifestyle
lies in the presence of these large pipes as well as sewer lines which carry
away our wastes for further dispatch.
Newer
sewer pipes can be made of concrete or polyvinyl chloride. Older ones can be made of clay and will last up to ~50
years.
(image by Eric Gaertner http://blog.mlive.com/chronicle/2008/0/laketon_township_sewer_water_p.html)
(image by Eric Gaertner http://blog.mlive.com/chronicle/2008/0/laketon_township_sewer_water_p.html)
Besides
the passage
of time,
factors
such as ground movement, soil conditions, random tree roots, and even ground
excavation for street repair can cause corrosion or damage to these pipes, and
they have to be either repaired or replaced. For a homeowner in Denver, CO,
replacing a sewer main can be costly: anywhere from $3,300 to as high as $17,000.
(image from Karen Schneider, http://coloradodenverinsuranceagent.com/2011/06/20/will-my-home-insurance-company-pay-for-a-new-sewer-line/)
One technology that is more cost-effective and preferred over replacement is CIPP or "Cured-In-Place-Pipe". It was invented in the early 1970s by Eric Wood, an English agricultural engineer, who took a flexible plastic and felt liner and impregnated it with a polymeric resin (either epoxy, polyester, or polyurethane). Placing this inside the sewer line he was trying to repair, he let the material cure in a matter of hours and presented a trenchless solution.
Here
are 2 YouTube
videos about CIPP. The first is an animation of what is involved in its
installation. The second shows
an actual installation in the field.
“The
CIPP program is also far less expensive than replacing sewer mains. Using this
technology costs the Service Authority roughly $31 a foot, which costs around
four times less than constructing a foot of new sewer main," said James McCarroll who is the Inflow and Infiltration Supervisor of the Prince William County Service Authority in northern Virginia.
With the advantages that CIPP provides - no need to dig, shorter timeframe, minimal shutoff of water service, and cheaper cost - we would consider this an ideal solution. But a number of concerns have been raised about the use of styrene which is one of the co-monomers in the resin itself as well as detectable amounts of other chemicals after curing. Hot water or steam is typically used to cure the resin for several hours, and the water would be discharged through the culvert without any processing.
In a 2014 published paper in Environmental Science and Technology, M. L. Tabor, D. Newman, and A. J. Whelton collected condensate after the curing process and analyzed it for aquatic toxicity. One way of determining toxicity was to place some Daphnia magna (a freshwater water flea) in this water:
a female adult Daphnia magna
(image by Hajime Watanabe (PLoS Genetics, March 2011) [CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons
Within 24 hours, they dissolved! Even after diluting by a factor of 10,000 the water fleas still had 100% mortality within 48 hours. Besides styrene, numerous other chemicals were detected that originated from uncured resin, plasticizers, and initiator byproducts. After 35 days some were still detectable.
Note: the red highlighted parts indicate where the monomers react to form polymers.
In a literature review conducted by A. J. Whelton et al., CIPP technology between 2004 and 2010 caused severe enough environmental consequences to result in hospital evacuations and fish kills.
In some cases, its use was temporarily halted.
In response, resin manufacturers like Interplastic Corporation and AOC Resins have developed non-styrene alternatives involving epoxy or vinyl toluene. In other cases, UV-radiation was used instead of hot water or steam in the curing process. There still remains a need to investigate the immediate environmental impact of discharging a large quantity of unremediated curing water. At this time there is no industry-accepted standard procedure that treats or sets the limits on CIPP chemicals to be discharged into the environment.
Note: the red highlighted parts indicate where the monomers react to form polymers.
In a literature review conducted by A. J. Whelton et al., CIPP technology between 2004 and 2010 caused severe enough environmental consequences to result in hospital evacuations and fish kills.
In some cases, its use was temporarily halted.
Precision
Industrial Maintenance Inc. (PIM) was subcontracted to repair culverts in
Upstate
New York. Ultraviolet radiation can be used instead of hot water or steam
in
CIPP resin curing.
For more information:
