Health Risks Assessment from Cured-in-Place Pipe Lining Fugitive Styrene Emissions in Laterals | Journal of Pipeline Systems Engineering and Practice | Vol 14, No 1

Field Study Design and MeasurementA mock sewer network was designed and constructed to represent a sanitary sewer with lateral connections. This network consisted of a 200-mm clay pipe with 21 100-mm PVC laterals with P-traps at the end of each lateral. P-traps on Laterals 1 to 11 were water-filled, while P-traps on laterals 12 to 21 were dry (air filled). Fig. 1 shows the field study layout.The sewer main was constructed using 22 clay pipe sections that were 200-mm in diameter and 910-mm long. The clay pipe sections were laid at 1% grade to represent a typical sewer with laterals. At the end of each pipe length, a 100×610-mm long clay-T section was installed. The main sewer pipe was designed to be below the ground surface, so all laterals were fully buried.Figs. 1 and 2 show that the laterals were spaced at an interval of 1.52 m along the main pipe and at an interval of 3.05 m on either side of the main. In a typical sewer network, laterals have only one lateral on a property and a spacing that is much greater than 1.52 m. Thus, this mock layout is not deemed to represent typical industry practice. The short spacing of laterals was used to validate styrene concentrations using different measurement methods and to assess measurement variability along the CIPP lined main. Each lateral was created by connecting a 1.52-m long and 100-mm diameter PVC pipe segment to the clay-T. Additional 100-mm diameter PVC pipe segments were added to create a lateral length of 10.06 m. This lateral length was deemed to be typical construction practice. PVC pipe risers of 100-mm diameter were added to create surface styrene and VOC sampling locations at 4.57 and 7.62 m from the clay main. These locations are labeled as A and B, respectively, in Fig. 2. At the end of each lateral, a 100-mm diameter PVC P-trap with a PVC riser was added. The P-trap riser is labeled C in Fig. 2. P-traps were labeled as PTW to indicate water-filled and PTD to indicate a dry P-trap. All PVC pipe sampling points were extended 906 mm above the ground surface and capped with removable PVC caps. OATEY Heavy Duty Clear Cement, purchased at a local hardware store, was used to glue all PVC joints.For styrene emissions monitoring, two approaches were used: (1) onsite direct read PIDs; and (2) laboratory analysis of passive air samples collected using the 3M Organic Vapor Monitor (OVM) and the WMS.Fig. 3 shows sampler locations during the CIPP installation and steam-curing. PIDs were placed in Laterals 4, 9, and 15, OVMs in Laterals 14, 18, and 19, and WMS in laterals 1, 2, 5, 6, 10, 11, 12, 13, 16, 17, 20, and 21.Construction of the mock network occurred during the week of May 27, 2019, in an open field west of Cepi Drive in Chesterfield, Missouri, which is northeast of Aegion corporate head office (see Fig. 4). The CIPP liner was installed on June 5, 2019, and field site monitoring performed from June 4 to 6, 2019. Fig. 5 shows the CIPP installation and termination locations. The weather on June 5 was mostly cloudy with temperature low of 21°C and high of 32°C, and wind speeds that ranged from 14 to 42  km/h. Around 6:00 p.m., a thunderstorm occurred that had wind gusts as high as 46  km/h. The weather on June 6, 2019, was similar to that of June 5, but the wind speed ranged only from 0 to 11  km/h.The CIPP liner was composed of a felt tube and polyester resin. The felt tube was constructed of two needled polyester fiber felt layers with a thin thermoplastic coating on the outside. Tube dimensions were 200-mm in diameter by a nominal 6-mm thickness, with a total length of 53.3 m. The tube was vacuum impregnated (wet-out) with resin in Indianapolis and shipped to Chesterfield in a refrigerated truck. The resin was a filled, isophthalic polyester resin specially formulated for use with CIPP. No excess resin was added to the tube.The wet-out tube (liner) was installed by the inversion process using a flow-through air inversion device. Air pressure during the installation was held at or slightly above Insituform’s recommended installation pressure. Steam was used to cure the liner followed by a cool-down period. Liner pressure during cure was held at or slightly above recommended pressure, with the termination end interface and internal air/steam temperatures reaching 82°C and 115.5°C maximum, respectively. The cured liner (CIPP) was cooled to an external interface temperature of 37.2°C and the ends of the CIPP terminations were cut and trimmed. A blower was then installed at the liner installation end, to blow VOCs and styrene out of CIPP-lined pipe and the termination pit. Laterals 2, 6, 9, 11, 13, 17, 20, and 21 were robotically cut open within 60 min of cutting the liner open. During lateral opening, uncured resin was noted in laterals 6, 9, 11, and 17.All laterals were numbered and labeled using the labeling scheme shown in Fig. 6.Onsite Direct Read Photoionization DetectorsIn this study, Hoenywell MiniRae 30000 and ToxiRae Pro handheld PIDs were used to take measurements and record data. PIDs are industry recognized and established broadband sensors that respond to a large variety of VOCs. VOCs are measured with PIDs provided that the ionization potential of a compound is lower than the UV lamp energy. The VOC-measurable concentrations are typically in the range of 0.01–10,000, while being most accurate in the lower end of that range up to about 2,000 ppm (Rae 2013). The response time of PID instruments (typically a few to several seconds) is usually determined by the rate at which the sample is pumped across the photoionization chamber and out of the device. Isobutylene is commonly used to calibrate PIDs because its response factor is about the midpoint in the range of sensitivity of the PIDs. PIDs can also be calibrated using a specific gas, but this is rarely done. The Rae manual states, “The monitor should be calibrated every time it does not pass a bump test, but no less frequently than every six months, depending on use and exposure to gas and contamination, and its operational mode.” In this study, all PIDs were calibrated using isobutylene gas before use.PID isobutylene VOC readings can be converted to another gas by multiplying the PID reading by the appropriate unit manufacturer-determined correction factor(s). According to Honeywell Technical Note TN-106 (Honeywell Technical Note 2016), all Rae PIDs with a 10.8-eV lamp have a styrene correction factor of 0.43. Thus, a PID VOC isobutylene reading of 100 ppm would have a styrene reading of 43 ppm (100 ppm * 0.43) if calibrated using styrene gas. Rae (2013) provides guidance on the PID readings when the gas being measured contains several different gases.Sendesi et al. (2017) reported that, during the CIPP lining process, VOC emissions can contain approximately 30% to 50% styrene, with equal parts heptane and ether. Using correction factors of 0.43 for styrene, 4.3 for heptane, and 1.0 for ether, a PID VOC isobutylene reading of 100 ppm would correspond to an actual styrene reading of only 25 to 33 ppm. In this study, the actual composition of VOC chemicals released during the CIPP installation and steam cure was not known. Thus, for this study, a conservative correction factor of 0.43 was applied to the PID VOC isobutylene readings to estimate the maximum possible styrene concentration in the air emissions.PID readings were obtained continuously before, during, and after the CIPP liner was installed and steam-cured. Each PID was connected to a Teflon tube that had a filter placed near the bottom of a lateral riser. All lateral risers were capped and sealed to ensure that no air flowed up the riser during the PID monitoring process.Waterloo Membrane SamplersHere, we will only discuss the WMS measurement method and results. No OVM results will be presented.The WMS is a patented permeation passive sampler developed at the University of Waterloo and commercially available from SiREM (Guelph, ON, Canada). Fig. 7 shows the WMS components.Unlike all other sorbent samplers on the market, the WMS has a well-defined uptake rate that is not sensitive to the presence of water vapor. The sampler is activated by removing it from the packaging vial and exposing it upside-down to allow the sorbent to meet the polydimethylsiloxane (PDMS) membrane. After a defined period, the sampler is moved into a sealed glass vial and then packaged in a sealed foil packet containing activated carbon adsorbent to prevent cross-contamination. Standardized procedures are developed to desorb the contaminants for gas chromatographic (GC) analysis, which can be completed by any standard laboratory. The WMS provides time-weighted average (TWA) concentrations of all chemicals adsorbed during the exposure time. By capping the WMS at different time intervals (i.e., 1, 2, 6, 8 h, etc.), the public and worker styrene air concentration, in mg/m3, can be determined using the following equation: (1) WMS styrene air concentration (mgm3)=Styrene sampled (μg)Uptake rate (mlmin)×Exposure time (min)×1,000The WMS styrene air concentrations can be converted to ppm using the following equation: (2) Styrene air concentration (ppm)=Styrene concentration(mgm3)24.45  L/mole104.15  g/molewhere 104.15 = styrene molar mass (g/mole); and 24.45 = molar gas volume (L/mole) for an air fraction at 25°C. Salim et al. (2017, 2019a, b) and Salim and Górecki (2019) provided details on the dynamic process of sampling using permeation passive samplers that utilize adsorbents as receiving phases and validate the sampler using test data and a mathematical model.The WMS was calibrated and validated by exposing it to known concentrations of styrene for specific periods under controlled laboratory conditions. This calibration was performed at temperatures between 60°C and 78°C, which was the estimated lateral temperature range during the CIPP lining cure process. This calibration determined a constant styrene uptake rate of 2.9 mL/min.



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