Carrying out ground investigation work, hydrogeological and soil mechanical borehole tests for the replacement of the Herbrum lock

CONSTRUCTION PROJECT The Ems-Nordsee Waterways and Shipping Office (WSA) as the client and project owner plans the replacement of the Herbrum lock. The Herbrum lock is located in the northwest of Lower Saxony in the Emsland district and serves as the entrance lock of the Dortmund-Ems Canal (DEK) from the North Sea, forming part of the DEK. The lock consists of two chambers, with the newer western chamber being in operation and the old eastern chamber having been decommissioned. The closed eastern lock chamber has neither been dismantled nor backfilled. The replacement construction of the Herbrum lock is to take place in this area. Corresponding ground investigations are required for the dismantling of the old lock chamber and the replacement construction. These are the subject of the present tender. GEOLOGY, GROUNDWATER AND SOIL TYPES For the tender of drilling work according to DIN 18301:2023-09, the following homogeneous areas are defined according to Section 2.2: Homogeneous area A: Fillings / Overlying soils / Loose rock, non-cohesive, partly cohesive, partly organic Groundwater is expected at a depth of 0.0 to 2.5 m below ground level according to HK 50. It is assumed that the groundwater level is coupled to the water level of the Ems River. According to HÜK 500, the aquifer is a pore groundwater aquifer. The project area is located in a documented area with saline lower groundwater. CONTRACTOR'S SERVICES Investigation methods and field tests: - Land-based core drilling (D >= 100 mm) as vertical drilling, partly with groundwater monitoring well installation (BK/GWM) - Water-based core drilling (D >= 100 mm) as vertical drilling (BK_w), in the lower approach channel with tidal influence - Land-based and water-based cone penetration tests (CPT & CPT_w), in the lower approach channel with tidal influence - Borehole tests (pumping tests, SPT tests) - Small-diameter percussion drilling (BS) - Heavy dynamic probing (DPH) In addition, the contractor (AN) is required to carry out professional geotechnical and environmental sampling. Construction site setup and sample storage: The client cannot provide any areas and/or premises. The contractor will rent suitable properties/areas for the construction site setup, core storage, sample storage, and for offices/office containers, preferably centrally located in the construction site area, and keep them available for the duration of the measure. The procurement of storage and work areas is the responsibility of the contractor. The contractor must arrange for the necessary connections (water, electricity, etc.) as well as for site security, the provision of barriers, and lighting. All drilled cores and samples taken must first be stored on the construction site or in its immediate vicinity in a dry, securely lockable, and frost-proof room (core storage). The core storage must be operational from the start of drilling. The core storage must be designed so that parallel work can be carried out dry at all times without mutual interference. There must be sufficient space in the core storage to accommodate the laying out of 1,200 core meters. Surveying of investigation points: The land-based and water-based investigation points will be surveyed by the contractor before the investigation begins and handed over digitally. Applicable height and position reference system: - Official height reference system DHHN2016 (height status 170) - Official position reference system ETRS89 / UTM Zone 32N Digital representation and handover to the geotechnical expert for integration into the geotechnical model in the BIM context. Drilling work: The core drilling must be carried out as liner drilling. The water-based drilling must be carried out from a pontoon. This must be a floating unit (pontoon) with at least 4 retractable legs to ensure a secure footing. The local mud accumulations in the approach channels must be taken into account. The planned investigation depth varies between approx. 20 m on the water side and 30 m on the land side. The drilling methods used must guarantee perfect exposure of the subsoil and perfect sampling. Boundary conditions for water-based drilling: The smooth operation of the ABz. Lathen (Herbrum support point) and the safety and ease of navigation must always be guaranteed. When using the contractor's floating equipment, restrictions due to the tide in the downstream section and consequently limited lockage time windows must also be considered. Small-diameter percussion drilling: In addition to core drilling, small-diameter percussion drilling will also be carried out. Sample transport: Samples must be transported to the core storage regularly. Collection of groundwater and surface water samples: Qualified collection of groundwater and surface water samples. Soundings with the heavy dynamic penetrometer: Soundings with the heavy dynamic penetrometer (DPH) are planned to determine the density of the existing soils. Cone penetration tests: Land-based and water-based cone penetration tests are planned for the subsoil investigation. Groundwater monitoring wells: Some of the ground investigation boreholes tendered for the investigation of subsoil conditions will be developed as groundwater monitoring wells. Water level measurements: The water levels in the completed groundwater monitoring wells must be recorded by the contractor using data loggers for 3 years. Standard Penetration Tests (SPT): Standard Penetration Tests (SPT) are to be carried out as percussion drilling in the borehole from the borehole bottom over a defined penetration depth. Short-term pumping tests: In addition to de-sanding or clear pumping, pumping tests will be required in the boreholes. These are single pumping tests.