Fluorescent Rubber Bag
Hole filling bags / big packs
Use fluorescent rubber bags filled with light environmentally friendly filling material to fill the excavation holes simply up to the top, so that nobody can fall into the hole.
The hole filling bags are similar to sand bags, just filled with lighter environmentally material like https://www.baehr-verpackung.de/polstermaterial-und-fuellmaterial/verpackungschips/flo-pak-green-verpackungschips/, so that the excavation holes can be easily filled with the bags every night and removed in the morning. The weight of the filling material is 1,9 kg je 500 l-Sack - so one big pack (https://www.boxonbulk.com/download) with 1 cbm would require 3.8 kg filling material puls some smaller bags like 100 l for smaller areas/corners. Everything is made 100% of recycled material.
Cost effective, simple and would the solve the problem.
Suitable to fill holes temporarily