Questions about the development plan

In the local new development area, we have made a reservation for one and have received the development plan.

There are three things I am not quite clear about or do not fully understand the consequences (yes, I have used the forum search ):

1. Old Deposits / Contaminated Sites
Within the scope of the development plan is the old deposit site "xxxx" registered under xxxx, which is classified as not suspected to be contaminated based on the evaluation, since only soil excavation mixed with construction debris was used there. Basically, old deposits classified as not suspected to be contaminated are usable for construction, albeit with a residual risk regarding previously unknown contamination and the structural stability of buildings.

A soil report is planned anyway, but is that sufficient or should something else be considered?

2. Radon
The planning area lies within a zone where locally increased and occasionally high radon potential EHU has been determined in individual rock horizons. It is strongly recommended to conduct preliminary radon measurements in the soil air to determine whether and to what extent construction measures should be adapted to the respective local situation. Information on radon protection for new buildings and radon remediation can be found in the "Radon Manual" of the Federal Office for Radiation Protection.
Is the soil report sufficient for this as well? A quick search led me to the conclusion that the main issue is sealing basements against radon (is that the only "problem")? Approximately how much would that cost additionally?

3. Infiltration and Discharge of Rainwater
There is only a compulsory connection to public sewage systems for wastewater generated. According to the Rhineland-Palatinate State Water Act - LWG -, the generation of wastewater is to be avoided as far as possible. In the designated building area, rainwater generated is to be disposed of by surface infiltration. This can include trenches up to 20 cm deep. Furthermore, regardless of any potentially necessary water law permit or approval, it is recommended to reuse roof water on the respective property.
A water law permit is required for infiltration systems and discharge into public waters, which must be applied for by a qualified engineer registered under § 110 of the Rhineland-Palatinate State Water Act - LWG - at the Higher Water Authority.
To me, this doesn’t sound very good at first if you have to let your rainwater infiltrate yourself? Based on the soil, one can relatively well calculate how large the infiltration area must be; is the soil report sufficient for that?
How can one imagine such an area? Would it then not be usable for the garden (lawn or similar)?

Thanks a lot in advance.

Hello,

1. Old Deposits / Contaminated Sites
Within the scope of the development plan lies the old deposit site "xxxx" registered under xxxx, which is classified as not suspected of contamination based on the assessment, since only soil excavation mixed with construction debris was placed there. In principle, old deposits classified as not suspected of contamination are usable for construction, with an existing residual risk regarding previously unknown contaminations and the structural stability of buildings.

A soil report is already planned, but is that sufficient or should something else be considered?

It is sufficient.

2. Radon
The planning area is located within a zone where locally elevated and occasionally high radon potential has been determined at certain rock horizons. It is strongly recommended to carry out preliminary radon measurements in the soil air to determine whether and to what extent construction measures should be adapted to the respective local situation. Information on radon protection for new buildings and radon remediation can be found in the "Radon Handbook" of the Federal Office for Radiation Protection.
Is the soil report sufficient for this as well?

No, here a report is needed that chemically analyzes the excavated material.

A quick search led me to the conclusion that it is mainly about sealing basements against radon (is that the only "problem")? What would that roughly cost additionally?

Radon is encountered wherever uranium lies dormant underground; it migrates from below upwards. To prevent it from entering the building envelope, you must have the basement floor as well as the slab constructed to be "gas-tight." Unfortunately, I cannot reliably tell you what additional costs this entails because I have little to no experience with this particular issue, despite working near an open-pit mine. However, I imagine that additives are added to the soil-contact concrete and special sealing of the sandwich concrete parts of the basement is required; the costs should roughly be comparable to constructing a waterproof basement. Depending on the size of the basement, in my opinion, anything between EUR 8,000 and 15,000 is possible.

If you feed Aunt Gurgle with "Radon + house construction," you will get very good and understandable information on the topic. A deeper description of the problem would go beyond what is reasonable here.

3. Infiltration and drainage of rainwater
There is only a usage obligation for public sewer systems for [logical change of mod] wastewater generated. According to the Rhineland-Palatinate State Water Act - LWG -, the generation of wastewater is to be avoided as far as possible. In the designated building area, rainwater generated must be infiltrated on the surface. For this purpose, basins up to 20 cm deep can also be used. Furthermore, regardless of any possibly necessary water law permit or approval, it is recommended to reuse roof water on the respective property.
A water law permit is required for infiltration systems and discharge into public waters, which must be applied for by an engineer registered according to † 110 of the Rhineland-Palatinate State Water Act - LWG - at the Upper Water Authority.
To me, this does not initially sound so good if you have to infiltrate your rainwater yourself? Based on the soil, one can relatively well calculate how large the infiltration area needs to be; is the soil report sufficient for this?

No, a hydrogeological report is required for this. This report determines how and to what extent the basin/infiltration system should be constructed.

How can one imagine such an area? Would it no longer be usable for the garden (lawn or similar)?

After a certain time, you won’t even see it anymore; however, the basin/infiltration system naturally must not be built over. That would also be pretty pointless

Rhenish greetings

Sounds like a total of two additional expert reports

No, a hydrogeological report is required for that. This report determines how and to what extent the swale/infiltration trench should be constructed.

I have to admit that as a layperson I can’t really imagine it, and even a picture search only helped me to a limited extent. If the swale has to absorb water from a base area of about 100 sqm, then it should be roughly the same size and that would already be quite a large part of the property?

If you are considering using a cistern for garden irrigation, does it make sense to use an infiltration tunnel and connect it to the overflow, or do they eventually clog up over time?

Sounds like a total of two additional expert reports then

YES.

I have to admit that as a layman I can’t really imagine it, and even an image search only helped me to a limited extent. If the depression has to hold water from a base area of ~100 sqm, then it must be roughly the same size and that would already be a considerable part of the property?

It is true that shallow depressions require more space than, for example, infiltration trenches. On the other hand, as a layman you can’t calculate that either; just looking at the formula already makes me dizzy.

The size of an infiltration trench is calculated based on the roof area, the probability of rainfall and in my opinion also how often the trench is allowed to “fill up,” and probably a lot more. It can be 4.5 x 2.50 m, but also 3.00 x 3.00 m; but definitely not in the dimensions you were thinking of.

If someone is considering getting a cistern for garden irrigation, does it make sense to take an infiltration tunnel and connect it to the overflow, or do they eventually clog over time?

Who should answer this question if important parameters are unknown? Honestly, I also don’t know what you mean by an “infiltration tunnel”? If I’m not mistaken, the overflow of a cistern is usually connected to the sewer.

Rhenish greetings