During the 1970’s, federal legislation was passed to ensure that the wastewater and drinking water systems be maintained.  Both the Clean Water Act (CWA) and the Safe Drinking Water Act (SDWA) provide a standard for municipalities to follow in the maintenance of their aging infrastructures.  Additionally, the Resource Conservation and Recovery Act (RCRA) provides the standard for industrial facilities infrastructures.

The current problem is system overload, especially during heavy rain events.  In many cases, hydraulic overload is relieved by completely bypassing the treatment system and releasing the contaminated excess water into adjacent water bodies.  Annually, thousands of beaches on rivers, lakes and coasts are closed due to high fecal coliform bacteria counts following heavy rain events.  The system overload has been attributed to Infiltration and Inflow (I/I) of basically clean rainwater into the infrastructure system.  The reason I/I gets into the system is due to the deteriorated condition of the pipelines and manholes.  The costs associated both directly and indirectly to this I/I problem run into the tens of millions of dollars.

The infrastructure system is composed of four basic parts; Treatment facilities, mainlines, manholes and service laterals.  Because the system was built over a period of two centuries, many different materials were used in its construction.  The primary construction material is concrete, but also brick, concrete block and even wood was used.

Though these materials have high tensile strength, they all are very rigid and have no elongation.  Over time, compression forces, geo-tectonic forces and chemical corrosion have resulted in cracking, erosion of physical properties and even collapse of many infrastructure components. 

Historically, many of these broken components went undiscovered due to limited diagnostic capabilities.  Recent developments in robotic camera evaluation, data collection and interpretation have only illustrated the enormity of the deterioration.  Municipalities today are faced with the dilemma of allocating limited financial resources to repair a system that has been neglected for centuries.  Many agencies have come to the realization that the most cost effective approach to repair is twofold; rehabilitation and replacement.

The rehabilitation aspect of the repair of infrastructure uses the existing or “host” structure as a mold or template.  For example, in mainline rehabilitation, an epoxy soaked felt tube is inverted or pulled into the sewer line, then expanded and finally cured against the host sewer line.  The result is building a seamless and structurally sound pipeline within the broken pipeline.  In polyurea manhole rehabilitation, we use the existing broken manhole as a template to build a seamless elastomeric manhole within the manhole. 

The patented Polyurea manhole rehabilitation consists of four parts; evaluation, cleaning, priming and polyurea application.  Evaluation is a critical step.  All manholes are not candidates for rehabilitation.  Some are so deteriorated or structurally deficient that replacement is the most cost effective method of repair.  Coordination with the local municipal personnel and the licensed polyurea manhole applicator during all aspects of the manhole rehabilitation project is crucial.

Important considerations to the manhole survey are; breaks actively leaking ground water (infiltration), structural collapse under the iron manhole frame and line blockage due to bricks having fallen from the wall.  All manholes within the scope of work must be evaluated and recorded.  Active infiltration is effectively remediated by pressure chemical injection, commonly referred to as grouting.  Cleaning of most municipal manholes can be accomplished by high-pressure water blasting of all surfaces to be coated.  Water pressure in excess of 3000 psi should be sufficient.  In industrial applications, degreasers, detergents and abrasives may be added to the high-pressure water to augment the cleaning process.  Priming is a critical step to ensure adhesion of the polyurea coating to the host manhole.  The primers, which incorporate a silane adhesion promoter and are low viscosity, provide consistent and reliable performance.  The polyurea coating is applied when the primer is tack free. 

The polyurea we use is a white pigmented aromatic system supplied by Polyurea Coating Systems, Incorporated.  The product; PCS-325 has the following physical properties:

In some cases municipalities have opted to stretch rehabilitation dollars by using polyurea coatings on the upper 4 feet of the manhole.  We call this technique a Chimney Seal©.  The Chimney Seal© is specifically adapted to structurally stabilizing the top section of a  manhole, especially brick manholes.  Brick manholes have a specific problem.  As bricks are loosened by vibration and tectonic stresses, the brick drops into the sewer line running through the bottom of the manhole.  The result is a blockage of the sewer line and restricts flow.  Repair of these blockages is costly and can be quite difficult as the bricks can be washed deep into the sewer line, necessitating excavation of the line.  The Chimney Seal© process we’ve developed is a fast preventative measure that stabilizes the problematic top 4 feet of brick manholes.

Other below grade structures that benefit from polyurea coating are lift stations, utility vaults and the wastewater treatment facilities themselves.  Polyurea coatings are actually manufactured in the field to the specific geometry of the host structure.  Therefore, the polyurea coating is custom made to the structure.  Polyurea coatings when applied by trained applicators exhibit excellent adhesion to many materials used in infrastructure construction, including; concrete, brick, iron and concrete block.