STORM WATER REHABILITATION, TEXASPROJECT PROFILE
Client:Harris County, Texas
Distributor: Nukote Coating Systems
System: Nukote Aegis®; Nukote ST-M®, Nukote HLT®, Nukote SPU Foam
Area: 76,000 ft2
Location: USA/ Texas
The project purpose was to repair the existing storm sewer line along the median of Space Centre Boulevard, in Harris County, Texas. In May 2015, a sinkhole was observed within the median of Space Center Boulevard at Station 105+32. A Closed-Circuit Television (CCTV) study was performed inside the storm sewer which consists of 24 to 66 inch diameter Reinforced Concrete Pipe (RCP), with invert depths from 6.2 to 13.5 feet below grade. Based on the CCTV inspection, most of the pipes and manholes have experienced joint infiltrations and broken pipes, with the most damaged segment of the storm sewer located between Station105+00 to 108+00.
In the past an emergency repairs, utilizing urethane injections were performed to: (i) seal broken RCP joints; (ii) to lift the storm sewer back to its original flowline; and (iii) to perform soil stabilization beneath the existing storm sewer. The urethane injections were not able to lift the storm sewer to its original flowline and were also unable to lift the sinkhole area back to its original ground surface. Harris County Engineering Department (HCED) Architecture & Engineering. Division (AED) requested Cone Penetration Tests (CPT) soundings along the storm sewer alignment to develop storm sewer repair options, in conjunction with the soil information from the borings, as well as the boring logs. According to the information provided by HCED, AED understands that the severely damaged segment of the storm sewer located between Station 105+00 and 108+00 would be replaced, while other portions of the storm sewer be repaired depending on the associated costs.
Based on the geotechnical reports, the system to be used for rehabilitation of sewer line, is specially related to denying ingress of ground water into the system and denying egress of the collected storm water into the ground surrounding the system. There is a substantial amount of ground water constantly present in a most locations. The ground water table increases during and after heavy rains, and significantly increases when the nearby Houston water treatment plant dumps excess water into the swamp to alleviate process water over supply. There are at least 10 Lateral pipes and catch basins that have eroded and become unstable with the pipes significantly out of alignment due to settling. There are 12-15 more of these lateral pipes that have significant breaches at the RCP joints, which are pumping water from ground water below the pipe, even when catch basins are dry. This is due to high water table ground water directly under and surrounding the lateral pipes and due to minor RCP joints alignment due to settling.
25 years of misalignment and heavy ground water flow outside of the collection system, has created water migration pathways surrounding the storm water system. After review of the Geo Technical report, Drawings, the CCTV Report laterals and pipes, Site Inspection Reports, and Detailed Analysis of the project and its historical repair history, the water table and probable soil condition; Nukote Coating Systems International confirmed that the proper installation of a tube in tube lining system would completely resolve the water ingress and egress issues experienced historically. As the erosion and deformation of the area surrounding the pipe was caused by exfiltration from the storm water system, washing away larger granular soil structures, and the system Nukote recommended included guarantees of no infiltration or exfiltration it is logical to conclude that further erosion from system will not occur.
The system proposed would resist any potential hydrostatic pressures possible in this location and eliminate further erosion issues caused by water from the pipe debilitating the surrounding soil causing substantial settling of the pipe and manhole system. The installed system proposed would remain intact even with substantial movement of the pipe and structures.
The project consists of installing 5,850 linear feet of The Nukote Aegis® System including Colloidal Silica concrete treatment sealer, Polyurethane Foam, and Pure Polyurea liner, on the existing storm sewer along Space Center Boulevard, including all RCPs, RBCs, inlets and manholes. RCP sizes varies from 24” to 66” and RBC size is 4’x7’.
The lining system specified is Nukote ST(M) Pure Polyurea, with a range of dry film thickness levels (240 mils to 480 mils) dependent on the severity and condition of the pipe structure. The Polyurea liner is applied on a concrete substrate pre-treated with Nukote HLT® Colloidal Silane penetrating sealer.
Warranties from Nukote
Nukote Coating Systems warrants the installed Aegis® system will perform as specified for 25 years from the date of project completion.
Benefits of Nukote Aegis® Liners
➢ Fast Reaction Time (sets between 5 and 15 Seconds)
➢ Eliminates delay and assists faster project execution
➢ Moisture and Temperature Insensitivity
➢ Monolithic and Seamless Application
➢ Excellent Adhesion and Abrasion Resistance.
➢ Superior Tensile Strength (>3500 psi).
➢ Impact Resistance and High Elongation (>350 %)
➢ Superior Tear Resistance (>2700 lbs/inch)
➢ Heat & Fire Resistance (UBC – Class2)
➢ Long Term Stability & Chemical Resistance
➢ No V.O.C, Environmental Friendly
Fast Reaction Time
The Nukote ST-M® fast gel time (4-5 seconds) , which is not effected by temperature, humidity or moisture in substrates, can be readily applied over cold or damp substrates, such as steel, concrete, or PU foam.
Moisture and Temperature Insensitivity
In underground applications where moisture and humidity is always a concern, Nukote ST-M® will outperform any product on the market today. Most coatings are sensitive to temperature, high humidity and substrate moisture. They will react with atmospheric moisture or high humidity to produce carbon dioxide gas and cause foaming or pin holing in the surface. In contrast, Nukote ST-M® is not affected by moisture and can also be applied at virtually any temperature with minimal application complications.
Nukote ST-M® chemically bonds to itself, producing a monolithic or seamless coating membrane. Coating applications typically fail at seams. Without seams, there is nowhere for failures to occur or where fluids, bacteria, or other contaminants can pool or penetrate.
An industrial protective coating will only perform as well as its ability to adhere to the substrate requiring protection. Nukote ST-M® adhesion dramatically outperforms other traditional coating products
High Abrasion and Impact Resistance
In highly abrasive environments, Nukote ST-M® performs extremely well and is commonly specified in projects where superior elongation, high abrasion resistance and impact resistance are demanded, including in liquids with heavy particulate content.
Superior Elongation and Tensile Strength
In lining applications, a low modulus and a high elongation elastomer is required to meet the challenge. Nukote ST-M®, is formulated to allow for structural movement and thermal cycling, while vigorously resisting punctures and tears. These attribute make it ideal in lining applications where there will be some shifting of the substrate. The excellent elongation and tensile strength properties allow it to bridge cracks and gaps in the substrate preventing failures.
In storm water applications resistance to chemicals is another key-factor for any product used. Storm water includes fuel, oil and other hydrocarbons which can be detrimental to long term performance of the installed liner system. Nukote ST-M® resistance to these contaminants assure extended performance
of the system
Method of Application
The Nukote ST-M® is applied using plural spray proportioning systems giving production rates more than 300 Lineal feet of pipe per day, while achieving high builds in single applications due to the fast gel and cure time of the product chemistry
The Nukote Aegis® products recommended here are based on aromatic isocyanate pre-polymers that are highly chemical and abrasion resistant and are UV stable. Tests have shown that after the equivalent of 10 years exposure to UV cycles, our coatings exhibit a high percentage of original physical properties, usually greater than 85%. This is much higher than alternative solutions. The lining system chemistry is not biodegradable and is completely inert, providing complete resistance to degradation from direct ground contact in immersion. These factors provide 100% assurance that the performance of the liner will not be effected by environmental conditions and continue you to perform well beyond its design life.
Nukote Aegis® products are the choice of infrastructure managers as linings in a variety of applications that include; potable water, waste water, storm water, alkali, salt solution, organic solvents and oils. Polyurea provides a strong barrier to spills from reaching the environment. In this type of application, the products readily conforms to vaults, pipes and protrusions to form a complete seal. The products are not harmful and do not pollute the environment through its production, storage, transportation, application, or disposal.
Benefits of Nukote Aegis® Colloidal Silica concrete treatment
➢ Environmentally friendly with zero VOC
➢ Reduces the porosity and increases durability of the concrete surface
➢ Densifies and hardens new and old concrete
➢ Improves chemical resistance and reduces water absorption
➢ Improves resistance to staining and dusting
➢ Improves concrete quality, durability, liquid repellency
➢ Effective chloride and electrolyte barrier
➢ Re-alkalizes carbonated concrete
➢ Reduces risk of moisture out-gassing, pin-holing, and blisters in polyurea, polyurethane elastomers, or other top coats
Nukote HLT® is a unique surface treatment for concrete consisting of specialized reactive chemicals, a lithium-colloidal silica matrix, and a super duty siliconate water repellent. HLT® can be used as a concrete surface treatment to reduce micro porosity in cementitious materials, or as a complementary pre-primer treatment for Nukote unique advanced polymer coatings. When applied to concrete or any pozzolanic material, Nukote HLT® penetrates to seal, densify and thereby harden cementitious surfaces. Nukote HLT® is formulated to penetrate and block capillaries, voids, and fine shrinkage cracks by reacting with free calcium hydrates to form an insoluble, permanent barrier. It improves water resistance, water repellency, and surface properties of cementitious materials – including concrete. Nukote HLT®-SR also reduces the risk of coating failures associated with moisture migration and outgassing. Concrete surfaces treated with Nukote HLT® last longer, cost less to maintain, and resist wear, abrasion and dusting.
Nukote HLT® is recommended for use as a pre-priming surface treatment on floorings, liners in immersion application, and adhered waterproofing membranes – including structures under hydrostatic pressure.
Nukote HLT® may be used as a standalone surface treatment in certain applications.
Benefits of Nukote 360 Ringtech® Robotics
➢ Perfect DFT compliance with specification
➢ Lower material consumptions while meeting specified DFT
➢ Faster application speeds
➢ Data for use in QA/ITP records and warranty documents
➢ Higher performance in applied lining systems
The Nukote Aegis® System specified will
- Meet the design life expectation of 75 years.
- The system is warrantable for 25 years based on the system’s ability to deny both ingress or ground water or egress of the storm water within the pipeline and manhole system.
- The system proposed will be contiguous from start point to end with no joints or seems providing a completely stable elastomeric system allowing for movement of the pipe or structure while maintaining a complete water tight liner denying egress or ingress of water from the installed system.
- Pipe structure linings are applied as tube in tube, spray applied to the substrate directly utilizing a plural component proportioner and Nukote 360 Ringtech® Robotics
- Cracks, joints and defects in the pipe will be lined directly as the lining is structural and small spans of missing pipe or defects are irrelevant to the systems performance.