INFILTRATION BOXES TO THE GROUND

Infiltration boxes to the ground

Rainwater, treated sewage in domestic treatment plants, emergency overflows of retention tanks are just a few cases that require proper infiltration to the ground. If our property has no rainwater system or combined sewage system, we need to consider the beneficial and effective drainage of rainwater or treated sewage into the ground. An alternative to drainage of water in the ground is to transfer its excess to a river or pond, for which a water permit is required.

Accordance with the law

Pursuant to the Water Law Act of 18 July 2001, discharging sewage into waters or into the ground requires a water permit. The Act defines wastewater, among others as discharge into water or soil:

• used water, in particular for domestic or economic purposes,
• liquid animal excrements, with the exception of liquid manure and slurry intended for agricultural use in the manner and on the terms specified in the Act of 26 July 2000 on fertilizers and fertilization (Journal of Laws No. 89, item 991 and of 2004, No. 91, item 876),
• rainwater or snowmelt, included in open or closed sewage systems, coming from polluted surfaces with durable surfaces, in particular from cities, ports, airports, industrial, commercial, service and storage areas, transport bases, roads and parking lots,
• effluent waters from landfills and their storage sites, used brines, healing and thermal waters.
  
  

Pursuant to the Act, a permit must be obtained for the discharge of domestic sewage or rainwater over 5 m³ per day into waters (rivers, canals, lakes) or into the ground (absorbent wells, infiltration boxes, drainages). If we do not discharge more than 5 m³ during the day, a permit is not required.

Ways of infiltration

Currently, there are many different ways of infiltrating sewage into the ground within your own property on the market. Examples are infiltration boxes, absorbent wells, drainage tunnels, gravel wells, and more. Systems are selected according to the catchment area, according to the purpose and type of soil. Currently, the infiltration boxes are the most popular choice of the infiltration system. The reason for their popularity is their versatility:

• several versions: boxes for pedestrian traffic, cars or trucks,
• boxes dedicated to light, heavy or poorly permeable soils,
• low price compared to traditional gravel infiltration methods,
• 3 times greater capacity than standard gravel systems - reduction of drainage area,
• little effort during assembly, easy and quick installation,
• possibility of any arrangement and cutting of boxes.

Igloo absorption well, drainage tunnel, Geodek absorbent boxes

Infiltration boxes are intended for the management of rainwater as well as treated in biological reactors sewage. Rainwater collected from roofs is discharged through gutters to drain pipes and sewage pipes, and then to boxes. The same happens in home sewage treatment plants. The use of a infiltration box system ensures optimal sewage management in urbanized areas.

The strengths

Filled infiltration boxes drain without pressure the accumulated water. The specificity of the work of infiltration boxes brings many benefits:

• reduces the dynamics of the outflow,
• increases the efficiency of the treatment plant,
• avoids oversizing the rainwater network,
• reduces the shock load of the sewage receiver from combined or separate sewage system,
• construction of modern underground absorbent devices can contribute to the protection of groundwater and surface waters.
  
  

For and against

Traditional gravel systems, unlike modern gravel systems, such as infiltration boxes, require much more space. Their volume is up to 3 times greater. In the case of gravel ditches, the accumulative capacity is only 150 - 300 liters per m³. While the drainage boxes have an accumulation capacity of up to 950 liters per m³ of boxes. Over time, fallen leaves, as well as garbage collected by the gutter system, contribute to the clogging of the gravel system. Cleaning such a system is very costly and laborious. In the case of infiltration boxes there is no such problem as they are wrapped in geotextile that prevents clogging.

Selection of drainage boxes

In order to select the appropriate number and type of boxes, we must take into account:

• the type and permeability of the land present on the plot; boxes dedicated to heavy soils differ from boxes for permeable soils,
• groundwater level,
• the way of using the space above the boxes; boxes dedicated to pedestrian traffic differ from boxes for road traffic,
• catchment area from which water will be collected and drained,
• geographic location.

Below is an overview table for selecting the number of boxes. In order to calculate the exact number of boxes, use a special ATV equation.

Calculation of the number of crates according to the ATV equation.

Where:
L - length of infiltration boxes [m]
A_n - reduced area [m²]
r_d - rd - rain intensity [l/s·ha]
D - duration of rain [min]
b - width of infiltration boxes [m]
h - height of infiltration boxes [m]
s_r - accumulation factor
k_f - soil filtration factor

A_n = Ʃ(A·Z)
where:
Z - runoff coefficient
A - area [m²]

Calculation example

• Roof area: 100 m²
  
• Runoff coefficient, tile: 0,8
• Rain intensity: 130 l/s·ha
• Duration of rain: 15 min
• Width of infiltration boxes: 0,6 m
• Height of infiltration boxes: 0,6 m
• Length of infiltration boxes: 1,2 m
• Accumulation factor: 0,95
• Permeable soils, medium-grained sands: 0,2·10^-3
  

2 skrzynki = 2 boxes

Location

The legal act that defines all the distances to be kept when installing the drainage boxes is the ordinance of the Minister of Infrastructure of April 12, 2002 on the technical conditions to be met by buildings and their location (with later changes and corrections):

• the minimum distance of the mounted boxes from the plot border is 2 meters,
• the minimum distance of drainage from the nearest well is 30 meters,
• the minimum distance of the boxes from the residential building is 3 meters,
• the minimalna odległość montowanych skrzynek od drzew i krzewów wynosi 3 metry.