Utilization of the Infiltration Facility Installation Decision Map

The "Infiltration Facility Installation Judgment Map" shows whether or not the area can install an infiltration facility from the judgment factors of topography, soil quality, and groundwater level.
Rainwater infiltration facilities can be installed when it is determined to be a "possible place" in the "infiltration facility setting judgment map", but cannot be installed if sufficient separation from buildings and retaining walls cannot be secured.

1. Confirmed the installation judgment ("possible land" and "impossible land") was confirmed by the "Infiltration Facility Installation Judgment Map".
2. For each installation decision at the installation location, the following field surveys are conducted to determine whether or not the final installation is possible.

• a.Check the separation between the building and rainwater infiltrate the outside crushed stone.
• b.Check the separation between the adjacent boundary and retaining wall and rainwater infiltration masu outside crushed stone.
• c.If there is a slope or retaining wall on the adjacent boundary, check the separation according to the height.

About separation of rainwater infiltration masu with buildings (PDF: 136KB)

It is a district where rainwater infiltration facilities are restricted, or even if the rainwater infiltration masu is installed, the function is not fully demonstrated.

The judgment factors in the "Infiltration Facility Installation Judgment Map" are as follows.
Based on the situation of each element, areas that are not suitable for installation are designated as "impossible land" and other areas are designated as "possible land".

Infiltration facility setting decision map (PDF: 8,493KB) [April 2011 edition]

Is it a steep slope collapse danger zone? → Not available: Steep slope collapse danger zone

Is the soil that is difficult to penetrate? → Not suitable for penetration: Kazusa Group (consolidated silt)

Is it possible to demonstrate the penetration capacity of infiltration facilities? → Not suitable for penetration: Groundwater level is less than 2m from the ground