Review of the groundwater monitoring and alarm system connected with the construction of the ‘Metro 4’ underground railway line in Budapest

Abstract

This paper summarizes the mathematical and logical model of an operating groundwater monitoring and alarm
system in connection with the construction ‘Metro 4’ underground railway line in Budapest. The monitoring system
consists of numerous water level (i.e. potentiometric level), temperature and flow measure points. In this process
automatic data loggers detect data and send them to a database where they are recorded as time series. The time series are
applied to real time by a smart alarm monitoring system which was developed to detect and filter negative accidental
artificial effects on the groundwater (these are in connection with the construction works).
Beside many other purposes, the system serves two main goals: one is to help preserve the condition of buildings near
the line of Metro 4, the other is to protect the geothermal water system in Budapest. The protection of the geothermal
water system has a high priority due to its high environmental and economic value.
The essence of the system is that, if a suspected artificial impact is detected, an alarm signal is initiated. The method
of making an alarm signal depends on the time series observed so far in the relevant measure points.
The water level of the River Danube has an obvious direct influence on the groundwater in Budapest, moreover the
flow of groundwater is in strong relation with the natural water fluctuation of the river. The river causes a large water level
fluctuations at several measure points which may hide some non-desired artificial effects. To avoid a situation in which
natural movements or events might cause alarm and interfere with the results of non-natural activities, some calculations
and reference time series are needed to filter the data and provide new time series which are free from these usual natural
changes. It is these calculated time series together with the raw measured data that are used to apply for detection.
Different alarm levels can be initiated (e.g. primary, secondary, tertiary), depending on the magnitude and span of the
changes.