Environ. Sci. Technol. 2000, 34, 1914-1918
Leakage of Chemicals from Two Grouting Agents Used in Tunnel Construction in Norway: Monitoring Results from the Tunnel Romeriksporten L I N E E . S V E R D R U P , * ,† A X E L E . K E L L E Y , † MONA WEIDEBORG,† KNUT E. ØDEGÅRD,‡ AND EILEN A. VIK† Aquateam - Norwegian Water Technology Centre, P.O Box 6875 Rodeløkka, N-0504 Oslo, Norway, and SINTEF Applied Chemistry, P.O Box 124 Blindern, N-0314 Oslo, Norway
Chemical grouting agents are used to reduce water leakages encountered in tunnel constructions. The object of the work presented in this paper was to study the leakage pattern and the amounts of substances released during use of two different grouting agents. The acrylatebased grouting agent MEYCO MP 307 and the isocyanatebased product TACSS NF/020 were used in the construction of the tunnel Romeriksporten, Norway, in 1998-1999. Drainage water from the tunnel was monitored with respect to the chemicals expected to pose the highest environmental risk. A total of 62 tons of MEYCO and 80 tons of TACSS were used during the monitoring period. The proportion of the products that appeared in the drainage water was estimated from monitoring data, data on water transport out of the tunnel, and the recorded amounts of grouting agents used. Average leakages of acrylic acid, methacrylic acid, and 2-hydroxyethyl methacrylate were estimated to be 1.2%, 0.6%, and 0.5% (w/w), respectively, of the total amount of MEYCO used. Average leakages of di-n-butyl phthalate and hexadecyl dimethyl amide were estimated to be 0.16% and 60% 0.17b->320 0.03b-20
The data are collected from refs 7-10.
b
0.93 86% 41-833 2.5-53
-0.02 84% 227-800 250
4.57 100% 0.8-8 0.1-2.8
4.42 92% 0.2 0.1
AA has been found to be specifically toxic to some species of freshwater microalgae (8).
Water flow out of the tunnel was also measured, and average weekly values were used to estimate leakage rates in kg/ week. By comparing leakage data for the different substances with the amounts of grouting agents used in the tunnel, the proportion of the injected chemicals which appeared in the discharged water could be determined.
Materials and Methods MEYCO. Acrylate-based grouting agents form gels in a polymerization reaction after mixing acrylic monomers with a hardener in aqueous solution. The MEYCO injection grout is made by mixing a component composed of several acrylates (including AA) and acrylate esters (including 2-HEMA) and a component containing an inorganic hardener immediately prior to injection. In Romeriksporten a 1:1 mixture of the two components was used. MAA is not an original component of MEYCO but is formed upon hydrolysis of 2-HEMA. Physicochemical and ecotoxicological data for the monitored components of MEYCO are shown in Table 1. TACSS. The TACSS monomer is diphenylmethane- 4,4′diisocyanate. An accelerator (C852), containing HDMA, is used to initiate polymerization. Polymerization is accelerated when the product is exposed to water. A 10% (w/w) addition of the accelerator was used. In addition to the reacting agents, TACSS contains approximately 50% (w/w) of the softener DBP. Physicochemical and ecotoxicological data for the monitored components of TACSS are shown in Table 1. Sampling. Weekly composite samples of drainage water from the tunnel were collected using a Contronic Development PSW 84 automatic water sampler (Prosesstyring, Drammen, Norway). Subsamples were collected at least once every hour. The composite samples were collected each Monday. If the samples could not be analyzed immediately, they were stored at 4 °C for a maximum of 24 h. All the concentrations referred to in this paper are based on measurements into an on-site treatment plant. During periods of extensive use of microcements in the construction work, a very high pH (10-13) was measured in the drainage water. Laboratory studies showed that the high pH enhanced hydrolysis of DBP during storage in the sampler. Therefore, the water samples were neutralized in the sampler with formic acid to pH ∼3. At this pH all the monitored components were found to be chemically stable. Chemical Analysis. AA, MAA, and 2-HEMA concentrations were quantitatively determined using GC/MS (Ion Trap MS). Prior to analysis, 50 mL of the water sample was acidified (pH < 1) using sulfuric acid, followed by addition of sodium chloride and an internal standard (1,2-dichlorobenzene). Liquid-liquid extraction of the aqueous sample was performed once with diethyl ether. After separation of the two
phases, the ether phase was dried using sodium sulfate, and the solvent was removed by evaporation to a total volume of approximately 1 mL. The analysis was performed by SINTEF Applied Chemistry (Oslo/Norway). Detection limits for AA, MAA, and 2-HEMA varied from 3 µg/L to 5 µg/L during the monitoring period. DBP and HDMA concentrations were quantitatively determined using GC/FID. Prior to analysis, an internal standard (benzyl butyl phthalate) was added to the water sample and extracted using a Supelco SPME-fiber (100 µm polydimethyl siloxane coating) for 30 min. A Shimadzu GC17A Gas Chromatograph with a Chrompack CP-Sil 8 CB/MS column (25 m * 0.25 mm i.d., coating 0.12 µm) and FID detector was used. The analyses were performed by KM Lab (Oslo/Norway). For both DBP and HDMA a detection limit of 2 µg/L was achieved. The measurements showed a linear response for standards in the range 2-300 µg/L.
Results and Discussion In the tunnel Romeriksporten, the results from the initial risk assessment and the monitoring data were used as a control to indicate whether the release of chemicals into the environment was within acceptable limits. The drainage water from the tunnel was released into the river Alna which discharges directly into the Oslofjord. As all the substances used have been found to be readily biodegradable, longterm effects were not expected. Chemical analyses were carried out and reported within 1-2 days after the delivery of water samples to the laboratory. If the environmental concentrations exceeded the acceptance limits, the use of grouting agents was reduced or stopped the following week. Concentrations and Leakage Patterns of High Priority Risk-Associated Components. The measured concentrations of AA and MAA in weekly composite samples of drainage water were compared to the amount of MEYCO used (Figure 1). The highest concentrations of AA (∼5000 µg/L), MAA (∼4000 µg/L), and 2-HEMA (∼4000 µg/L) occurred during injection, after which the concentrations of all the substances rapidly decreased to
