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9
DARDILLY
THE BASINS AT GODEFROY
When the Noyeraies district was created in Dardilly, Grand Lyon
built a system of landscaped retention basins integrated
in the natural dale of the Ruisseau de la Liasse. They are
intended to temporarily store the district’s run-off water
and to feed it back to the Ruisseau de la Liasse at a moderate
flow. Two basins comprise the containment works at Godefroy:
the first, a low-capacity storage basin, is shallow, takes
the rainwater (routed there by ditches and pipes), holds it
and allows it to settle. The water is then routed, via works
which restrict the flow, towards a second basin with a larger
storage capacity before being returned to the Ruisseau
de la Liasse. Overflow systems ensure that the works function
properly during heavy rainfall. Designed as wetlands with a weak
horizontal flow, these basins have allowed the original
biodiversity of the dale to be restored, to the delight of biologists
and walkers. The works are now managed by the Syndicat
du Vallon de Serres et Planches and are regularly reviewed
by the parish and by Grand Lyon.
DARDILLY
THE BASINS AT LA BEFFE
Located to the west of Dardilly, the district of La Beffe lies
in a dale characterised by a dispersed habitat and private
on-site sewerage. At the start of the project, the dysfunctional
operation of these independent sewerage systems resulted
in the deterioration over time of the Ruisseau de la Beffe
immediately downstream of this district. A general
rehabilitation project for the individual on-site sewerage
systems and the rainwater management of the district
was carried out with the local residents, the town hall,
the Agence de l’Eau Rhône Méditerranée Corse and Grand
Lyon. A new central main sewer was built under the La Beffe
road to take rainwater and the water discharging from
the independent sewerage systems which could not be allowed
to percolate. Downstream from the main sewer, a cascade
of retention basins using the techniques of reed-bed filters
provide an additional treatment for the individual systems
in dry periods, and the containment and treatment of runoff
water in rainy periods. This «rustic” process, requiring
little in the way of maintenance, is well-suited to the site’s
architectural and landscape constraints and guarantees
the quality of the wastewater discharged into the natural
environment. Just downstream, the Ruisseau de la Beffe
can now see its lively and natural course restored
and can continue on its way to the River Yzeron.