Building ground investigation report (ram core soundings) suitable or excavation?

Possibly also expect that an unexploded ordnance found during the construction work will be found.

Hello Grericht

I would order a 3 m³ container for construction debris. Get yourself a shovel and pickaxe, a (good) wheelbarrow, and start digging. 150cm deep. Two or three hours of work. Then you are down and have the debris in the container. Possibly at another spot as well and you have saved the [Baugrundgutachten].

Steven

Unfortunately, I read Steven's tip too late. I relied on a geologist from the region who was recommended to me. It cost me about 1100 EUR including the LAGA examination. Four boreholes were made, and it was determined that the old basement had been extensively excavated. Unfortunately, everything except about 2.70 m was filled with construction rubble. The foundation recommendation is therefore 2.70 m. Groundwater was found at 3.20 m, and it is suspected that this level depends somewhat on the level of the nearby river.

"Filling
In the boreholes, a stony, silty to highly silty sand-gravel mixture (soil group GU/SU/SU*, formerly soil class 3/4) or a sandy, slightly gravelly to gravelly silt (soil group UL, formerly soil class 4) was drilled to depths of 2.25 m - 2.75 m below ground level. The brown to gray-brown soil horizon showed a loose structure or soft consistency at the time of investigation and was slightly moist to moist.
The horizon contains quartz, granulite and gravel pebbles, as well as varying amounts (5-30%) of construction rubble such as: brick and concrete debris, charcoal, glass shards, slag pieces, and roofing slate.
The filling is a mixture of natural soil materials and construction rubble."

So far so good, this would argue for a new building with a basement, and I could have found that out myself by digging with some work (for which I could have even rented a large excavator for a week!)
The annoying thing: A LAGA examination was also carried out with a composite sample. This was taken from the 4 boreholes and from different depths of the area with fillings (0.10-2.75 m). The results are very sobering:
see picture

We were told that this means the soil has to be disposed of. At 10*10*2.70 m, we are talking about approximately 300 m³.

[*]Is it possible to estimate what this costs? Are there alternatives?

[*]Could it be that only a small lead splinter got into the sample as a solid, and it might be worthwhile for us to do another test, this time not a composite sample? Where can this be analyzed and what does it cost?
[*]If we do not rebuild and do not replace the soil, do these values have a concerning significance? Should we refrain from growing fruit and vegetables in the garden?
[*]What does the Z2 value in the sulfate mean?

Oh oh... looks expensive!

Price trend? Only soils with >Z2 need to be deposited? So is only the lead value too high? Up to 200m³ you don’t need to submit a LAGA? So I could also drive away 200m³ like that and claim I don’t have a LAGA?

In all limit value tables on the internet that I find, zinc and sulfate are only Z1.2 and lead only Z2. Is there a currently valid nationwide list somewhere in Germany?