Matthias Eiswirth

IMPACTS OF SEWER LEAKAGE ON URBAN GROUNDWATER

Leaky sewers have to be considered as potential sources for groundwater contamination in urban areas. The medium-sized city of Rastatt in SWGermany with 50,000 inhabitants was subject of a series of investigations on sewer leakage which are summarized and discussed in this paper. Amongst others factors, the degree of pollution depends on the chemical composition of the wastewater and the amount of exfiltration. The groundwater underneath the city area showed anthropogenic influence resulting in elevated concentrations especially of boron, potassium and sodium as well as a generally increased electrical conductivity. Groundwater in the close vicinity of broken sewers showed typical sewage indicators such as iodated X-ray contrast media and microbiological parameters. Contamination with pharmaceutical residues and gadolinium could not be found in groundwater, despite significant concentrations of pharmaceuticals in wastewater. In autumn, the contents of boron and microbiological pollution were higher than in spring, indicating a higher ratio of wastewater in groundwater during times of less natural recharge. Groundwater monitoring wells near prominent leaks showed short-time fluctuations of EC and groundwater levels which could be correlated to changes of the wastewater composition and the flow regime in

Redox Zones in the Plume of a Previously Operating Gas Plant

Within the framework of a current research program, the fate of BTEX has been investigated in a Quaternary porous aquifer below a former gas plant in south-west Germany. The investigation site is located in the Neckar valley and occupies an area of about 600 m by 400 m (Figure 16.1). Industrial activities in this area started in the year 1875 with the production of gas and other coal-derived oils and tars by hard coal carbonisation. After 1956 gas production was carried out on the basis of heavy oil; starting in 1964, light mineral oil products were used. There was a change from city gas production to the distribution of natural gas between 1969 and 1974.

Field Soil Gas Screening Methods for the Delineation of Subsurface Contamination

Delineation and remediation of subsurface contamination have become a major focus of environmental science during the past five years. Conventional technologies available for subsurface investigations (e.g. monitoring wells) always will be required to confirm and monitor subsurface contamination; however, quicker and less expensive techniques are useful for preliminary site evaluations. Soil-gas surveying is a technique that is applicable to a wide range of volatile organic compounds (VOCs) and other contaminants under a variety of geologic and hydrologic settings. This paper presents the results of the use of soil-gas surveys for evaluation of the magnitude and lateral extent of a BTEX contamination at a former gas plant in Southwest Germany.

Soil-Gas Investigations for the Deliniation of VOC Contaminations in the Subsurface

Delineation and remediation of subsurface contamination have become a major focus of environmental science during the past ten years. Owing to the high cost of installing groundwater wells, soil-gas monitoring is often used as a preliminary technique for determining the presence and extent of underlying groundwater contamination and to assist in the design of monitoring well networks. This practice is based on the assumption that volatile contaminants in groundwater are transported upward in sufficient quantity to be detected in the overlying soil-gas. Several field studies have indicated that mass exchange between the saturated and unsaturated zones does occur (Rivett 1995; Dagvis 1998; Lahvis et al. 1999), but the relationship between contaminant concentrations in the groundwater and the soil-gas is not entirely understood.

Nachweis der Umweltverträglichkeit von Weichgelinjektionssohlen

Tief in das Grundwasser reichende Baumasnahmen erforderte trockengelegte Baugruben. Diese werden mit Hilfe von seitlichen Dichtwanden bzw. Spundwanden erstellt. Zur Verminderung des Grundwasserandrangs von unten kamen in den letzten Jahren verbreitet Weichgelinjektionen zur Anwendung, nicht zuletzt wegen der relativ guten Beherrschbarkeit dieser Bautechnik und auch wegen der Okonomie ihres Einsatzes. Aufgrund des erheblichen Umfanges der Injektionsmasnahmen und der damit moglicherweise verbundenen Boden- und Grundwassergefahrdung hat die in Berlin zustandige Genehmigungsbehorde 1995 einen Zulassungsstopp fur Baumasnahmen mit Weichgelsohlen ausgeprochen. Im Rahmen zweier Fachgutachten konnten 1995 bzw. 1997 bereits entscheidende Bedenken hinsichtlich einer potentiellen Gefahrdung des Bodens und des Grundwassers durch Weichgelinjektionen ausgeraumt und der weitere Einsatz von Weichgelen durch die Gutachter empfohlen werden. Dennoch blieb der Zulassungsstopp seitens der zustandigen Behorden in Berlin bis auf wenige Ausnahmen bestehen, bzw. er wurde sogar von weiteren Stadten ohne nahere Uberprufung der Fakten ubernommen. Der hier vorgelegte Artikel fast die wesentlichen Resultate der Gutachten und Forschungsarbeiten mit dem Ziel zusammen, die Umweltvertraglichkeit von Weichgelinjektionen wissenschaftlich zu beleuchten.