Rehabilitation of a large mixed water collector in several sections by means of trenchless sewer rehabilitation using 1200/1800 egg-shaped iMPREGLiner with a wall thickness of 13.1 mm.
Groundwater penetrates combined mixed water collector
Undesired infiltration by invasive groundwater, as well as the risk of waste water escaping outwards into the ground (exfiltration), meant that rapid rehabilitation of the porous mixed water collector was urgently necessary. The 1200/1800 collector in Wilhelmstrasse street is being rehabilitated in a total of four sections, with a total length of 350 m (eight host pipes), and is thus being brought to the state of the art for its future duties. To perform the work, the street was therefore closed in sections, and the resulting waste water was fed into the downstream network by means of pumps. For this, trenchless sewer rehabilitation proves itself the faster construction process by far, compared with the open trench method.
The fitting solution
As specified by Achten & Jansen, the consulting engineers, after the renovation the sewer cross-section was to be maintained as far as possible, in order to ensure the necessary retention volume in the event of heavy precipitation. The pipe-lining process (pipe-in-pipe system cured onsite) was therefore decided on. In the acclaimed and world-renowned iMPREGLiner GL16A, a quality product with very high standards was used for rehabilitation. The pipe liner consisting of multiple layers of fibreglass fabric impregnated with resin in the factory was inserted into the sewer via a manhole, without needing to dig a trench.
Important preliminary tasks performed professionally
A 1200/1800 egg-shaped iMPREGLiner 156.5 m in length and with a weight of around 19 tonnes was installed in the first section. Using this liner, our long-standing customer Aarsleff Rohrsanierung GmbH (Cologne/Bonn branch) set a further milestone for this type of profile.
The construction site was carefully prepared in advance by the client and the consulting engineers, and an above-ground diversionary sewer was implemented so that no waste water could run through the mixed water collector while inserting the liner. A reinforced fabric hose sheathed the usually typical yellow liner. The hose functioned as an additional external protection against the changing groundwater level.
Rehabilitation into the night
The 19 ton (including transport crate) iMPREGLiner was delivered “just in time” to the site in Euskirchen. The heavyweight was inserted into the sewer using an installation aid (conveyor belt with folding system) and a cable winch. In spite of appropriate preparations, penetrating groundwater and installation against the direction of flow hindered the work of the AARSLEFF team, which was supported by Oliver Vorlop (Head of Application Engineering at iMPREG GmbH). Because of the specified curing speed, the process lasted well into the night. It used AARSLEFF’s own UV system and iMPREG’s own light source, consisting of a Jumbo-core 12 x 1000 Watt. And so, within two days, it was possible to rehabilitate the first section of the dilapidated mixed water collector successfully and as planned.
The AARSLEFF team was put to another test during the second installation. In this section, the mixed water collector was traversed by a concrete slab. This problem was already known in advance, and iMPREG GmbH solved it using a special design for the affected section of liner. For the affected section the liner was reshaped to the reduced cross-section by the works in Ammerbuch. In this way, the liner made full contact with the inner surface of the old sewer section, without folds or creases. The second challenge faced by AARSLEFF was drawing the Jumbo-core through the reduced cross-section without damaging the iMPREGLiner. For this, the controllable Jumbo-core was mechanically retracted to the smaller cross-section before the transverse concrete slab and then, after passing through the restricted cross-section, extended again to the 1200/1800 oval profile. An impressive technical feat by the AARSLEFF team.
Successful trenchless pipe rehabilitation
“The team worked very well and delivered a great result,” said Oliver Vorlop. Jürgen Conrad from the municipal office for Civil Engineering and Urban Drainage also confirmed this: “The entire rehabilitation went extremely well. Like well-matched gearwheels, everyone worked hand in hand and thus contributed to the convincing end result.”
Because of the poor weather conditions caused by continuous rain, the work had to be interrupted after the successful rehabilitation of the first two sections. In order to finish the work without delay, it is already planned to continue when the weather is suitable.