Offer to build a wastewater treatment plant, okay?

Hello, we have received an offer from our shell construction company for the site drainage and I wanted to ask if you think it's reasonable. We are building near Nuremberg, so Franconia, the nicer part of Bavaria. ;)

The following items are offered:

- Remove topsoil in the area of standing space, garage = lump sum 160€

- Create crane parking area with mineral concrete paving = lump sum 650€

- Deliver backfill material for sewer pipes = 50 cbm 940€

- Excavation for SW inspection shaft 3.40m deep = 699€

- Excavation for RW inspection shaft 2.30m deep = 595€

- Supply and install SW inspection shaft = 2200€

- Supply and install RW inspection shaft = 2090€

- Create fall protection at shaft = 650€

- Supply and install kettled valve flap = 160€

- Excavate driveway to garage, supply, install and compact mineral concrete = lump sum 350€

- Rainwater cistern 6 cbm monolithic concrete tank supply and installation = 2800€

In total, the gross amount is 13,439€. Is the price reasonable?
We do have an offer from another company which was more expensive, but maybe I visited two pharmacies.
Many thanks for your opinion.

Regards

Without a cistern - just the two inspection shafts we paid 5,500 net including excavation removal and all the piping

Edit: also Middle Franconia ;) Eckental

You get a cistern and then also an inspection shaft which costs about 2700 € more with installation. I wonder if this shaft is really necessary.

We also have a cistern and no inspection shaft. However, it must be said that we are no longer connected to the rainwater drainage but instead the water infiltrates on our property. Thus, the corresponding fee is no longer due.