③ Hydrology
There are five major river systems in Beijing, from west to east in order the Daqing
River System, the Yongding River System, the Beiyun River System, the Chaobai
River System and the Jiyun River System. These rivers generally flow from the
northwest to the southeast and finally converge into the Bohai Sea.
(2) Overview of geological environment
The tectonic pattern of the Beijing area was formed in the Mesozoic, and was
further modified since the Cenozoic. The predominant characteristic is faults and
fault-controlled block activities. The faults active in the Cenozoic mainly include
two groups, one group extends from north-northeast to northeast and the other from
northwest to east/west. Most of these are positive faults and controlled the fault
basins developed in different periods of the Cenozoic to varied degrees. Most of the
faults are distributed in belts in a concentrated manner, forming mainly four
structural belts extending from north-northeast to northeast and another one
extending in the northwest direction. The ones extending from north-northeast to
northeast include the Huairou-Beijing-Zhuozhou structural belt, the Pinggu-Sanhelangfang structural belt, the Tianjin structural belt and the Yanqing-Huailai structural belt. The one extending from northeast to the west is the west section of the
Zhangjiakou-Beijing-Yantai structural belt, which crosses the north sections of the
aforementioned four belts diagonally.
2. Investigation of the informal landfill
(1) Overview of wastes in the informal landfill
The investigation showed that the informal landfill was formed by filling wastes
into a pond originally formed from a sand pit that exposed groundwater. The filling
of wastes into the pond started at the end of 2014. The wastes included domestic
refuse and construction spoil, which were filled in a mixed manner. The investigation scope is shown in Fig. 5.52.
(2) Investigation by construction of monitoring wells
① Setup and sampling of monitoring points
A total of 17 exploration holes and 3 monitoring wells were drilled in the investigation,
including 9 general exploration wells, 2 waste soil and environmental soil sampling
wells, 6 hydro-geological exploration holes, 1 waste soil and environmental soil
sampling well that also serves as leachate monitoring well, and 2 environmental
hydro-geological exploration wells that also serve as groundwater monitoring wells (to
monitor the 1st layer of groundwater exposed by exploration). The exploration hole
and monitoring wells have a depth of 4.00–22.50 m and total footage of 171.00 m; The
setting-out, exploration, construction and elevation measurement of the above 17
exploration holes and 3 monitoring wells were completed at the same time.
A total of 31 samples were collected for this investigation. These included 3
waste soil samples from the landfill site, 6 samples of the underlying natural soil,
264
5 Application Cases
There are five major river systems in Beijing, from west to east in order the Daqing
River System, the Yongding River System, the Beiyun River System, the Chaobai
River System and the Jiyun River System. These rivers generally flow from the
northwest to the southeast and finally converge into the Bohai Sea.
(2) Overview of geological environment
The tectonic pattern of the Beijing area was formed in the Mesozoic, and was
further modified since the Cenozoic. The predominant characteristic is faults and
fault-controlled block activities. The faults active in the Cenozoic mainly include
two groups, one group extends from north-northeast to northeast and the other from
northwest to east/west. Most of these are positive faults and controlled the fault
basins developed in different periods of the Cenozoic to varied degrees. Most of the
faults are distributed in belts in a concentrated manner, forming mainly four
structural belts extending from north-northeast to northeast and another one
extending in the northwest direction. The ones extending from north-northeast to
northeast include the Huairou-Beijing-Zhuozhou structural belt, the Pinggu-Sanhelangfang structural belt, the Tianjin structural belt and the Yanqing-Huailai structural belt. The one extending from northeast to the west is the west section of the
Zhangjiakou-Beijing-Yantai structural belt, which crosses the north sections of the
aforementioned four belts diagonally.
2. Investigation of the informal landfill
(1) Overview of wastes in the informal landfill
The investigation showed that the informal landfill was formed by filling wastes
into a pond originally formed from a sand pit that exposed groundwater. The filling
of wastes into the pond started at the end of 2014. The wastes included domestic
refuse and construction spoil, which were filled in a mixed manner. The investigation scope is shown in Fig. 5.52.
(2) Investigation by construction of monitoring wells
① Setup and sampling of monitoring points
A total of 17 exploration holes and 3 monitoring wells were drilled in the investigation,
including 9 general exploration wells, 2 waste soil and environmental soil sampling
wells, 6 hydro-geological exploration holes, 1 waste soil and environmental soil
sampling well that also serves as leachate monitoring well, and 2 environmental
hydro-geological exploration wells that also serve as groundwater monitoring wells (to
monitor the 1st layer of groundwater exposed by exploration). The exploration hole
and monitoring wells have a depth of 4.00–22.50 m and total footage of 171.00 m; The
setting-out, exploration, construction and elevation measurement of the above 17
exploration holes and 3 monitoring wells were completed at the same time.
A total of 31 samples were collected for this investigation. These included 3
waste soil samples from the landfill site, 6 samples of the underlying natural soil,
264
5 Application Cases