Ylöjärvi needs to make a new plan so that water does not spread from the waste area to the neighbor’s side. Some of the ditches were not made during the renovation.
A surprising flooding problem has appeared in the waste area of \u200b\u200bthe former Haveri gold mine located in Ylöjärvi. More water accumulates than expected at the edges of the tailings area rehabilitated by the city of Ylöjärvi.
Pirkanmaa’s ely center has asked Ylöjärvi for a new plan to control the waters of the area.
This fall, the city of Ylöjärvi already had time to rejoice at the results of the renovation work, even though some of the ditches were still unfinished. Ylöjärvi and ely center announced in October that the ground-breaking renovation of the Viljakkalan Haveri mining waste area was completed.
– The exceptional renovation project of the Haveri mining waste area ended in Ylöjärvi in \u200b\u200bthe summer of 2022, at least according to expectations, if not even better, the release said.
According to the release, the cost estimate of 5.6 million euros was exceeded, and the costs remained below 4 million euros.
A thick ground cover squeezes water out
During the renovation, the tailings area was covered with dense, poorly permeable soil. The goal was that, thanks to the ground cover, the transport of harmful substances in the tailings with stormwater to the nearby Kirkkojärvi would be reduced.
However, not all ditches have been built yet. This is why the area floods, according to Pajunen, especially in autumn.
– We have asked for a more detailed plan than before on how to manage the ditch waters better than at present.
The Ely Center wants a water treatment system as comprehensive as possible for the area, so that the flood waters do not cause additional harm to the owner of the neighboring property and to the waterway.
Pajunen says that mainly the water goes into the ditches already on the border of the area, but the amount of water has also increased around the ditches.
According to Pajunen, the compression of water from the tailings area caused by the soil cover was expected, but perhaps more water came at once than expected.
Plans changed on the way
Even before the renovation work, the plan included water management and related ditches.
However, according to Chief Inspector Emmi Pajunen, the city of Ylöjärvi implemented the covering of the area slightly differently than in the original plan.
– It is typical that additional studies are obtained during the work and the original plans have to be changed a little, says Pajunen.
– Edge ditches were not implemented at that stage, so that it could be ensured that they do not need to be dug into the tailings. This would have made the situation worse, says Jokihaara.
The ditches are to be built in the base soil outside the tailings area, so that the storm water does not come into contact with the contaminated soil.
A ditch has already been made on one edge of the area.
Jokihaara says that after the actual renovation, follow-up will begin. The soil piled on top of the tailings sand and the subsoil beneath it will be compacted in the coming years. This causes dents that need to be repaired.
– The area is shaped over and over again in a shape that can drain away water.
Ylöjärvi has not yet made a cost estimate for the follow-up work. According to Jokihaara, the original cost estimate will not be exceeded.
– Drainage and surface shaping are smaller works than the previously done renovation works.
Jokihaara estimates that at least the shaping will be done in the summer, some of the ditches possibly in the winter. Even next winter, we will hardly be able to get to work.
A big flood in the summer of 2021
The tailings area had problems related to water management already during the renovation works.
Jokihaara says that in the summer of 2021, water began to rise on the edges of the area and even in the area to be renovated. This too was probably due to the compression caused by the land mass.
At that stage, about a third of the tailings area was covered.
A hot and dry period hit that part of the summer. This caused concern that the solution coming out of the tailings is very concentrated, as there was no rainwater to dilute it.
It was the summer holiday season. Samplers were not readily available.
– The fear was that if that water is released into Kirkkojärvi, the fish will start swimming with their ventral fins upwards, Jokihaara says.
Because of this, water was withheld in the area. Finally, the long-lasting heavy rains started. They made the situation even worse.
– There was water everywhere. The water also spread somewhat wider in the surroundings, because the ditches were partly unfinished and the renovation work was in progress.
Later in the fall, water could be released into Kirkkojärvi when the samples could finally be taken. According to Ari Jokihaara, nothing unusual has been seen in the samples taken from the lake.
Ylöjärvi continues to monitor Kirkkojärvi’s water quality in order to understand the effects of the renovation.
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