Reservoir Design at Bronte Park Farm

Introduction:

On Bronte Park Farm, North Yorkshire, the client to M. Lewis Geotechnics Ltd, Beckett Water Authority proposed reservoir construction. The region of the proposed project consists of two main streams which flow into a valley which is high sided. The proposed development was proposed to be carried out at the narrowest region of the valley. Based on the client's specifications, the dam had to be an earth filled dam consisting of a pumping station and two spillways. A factual report (J100/17/E) whose results have been published under separate covers was prepared by the Rogers Geotechnical Services Ltd as part of the information concerning the construction site. The main objective of the general report was to give an outline of the proposed construction site’s structural properties. Additionally, with the aim of offering solutions or an alternative solution, and identifying problems that may be encountered during or after the construction, initial design calculations were included in the report. Some of the sections that have been included in this report include Geology and Ground Conditions, Earth-Filled Dam, Slope Stability, Spillways, Pump House as well as Retaining Wall.

As per the client, Beckett Water Authority the reservoir that is proposed to be built at Bronte Park Farm is to be an earth-filled dam. These kinds of dams are characterized by well-compacted earth and composed of either one type of material or various types of the materials-zoned earth dam. In most cases, locally available and plentiful materials are sourced for the construction of dams. Dam construction usually constitutes of a variety of materials such as metals, concrete, timber, and earth among other materials. The construction of an earth dam is characterized with a watertight clay or even concrete with hydraulic fill to create a watertight core as well as a drain layer which preserves the downstream zone and can also be used in the collection of seep water. This kind of reservoirs is cost effective due to the fact that; they use locally available resources for construction. Unfortunately, great care is required in the engineering and design since consequences of the failure of the design can be fatal and this means that the design should assess all risk that can be involved.

This section consists of the information as published in the Rogers Geotechnical Services’ Factual report - J100/17/E. The primary purpose of this report was to assess the groundwater conditions and obtain information on the ground of the site of the proposed development project. To obtain this information, their boreholes namely ‘SA1', ‘SA2', and ‘SA3’ were drilled using a 1.5 tones capacity light cable percussive. The drilling rig was 150mm in diameter. Based on the report the boreholes were sunk to 25 meters in depth at various regions as per the target of Rogers Geotechnical Services. Additionally, based on the BS1377: 1990: Part 9: 3.3 standard penetration tests were undertaken in regular increment. The obtained samples from the boreholes were taken to be investigated in the laboratory.

Moreover, the pump house had a primary role in ensuring the safety and protection of the pumping station and its equipment. Generally, a pump house is a structure that is built to house the equipment and in most cases, it is secured to prevent theft, damage and unauthorized access. Based on the report, the Beckett Water Authority has not yet proposed the specifications of the pumping equipment though they have predicted that the equipment requires large space that can impose a load of a 35kN/m2 on a raft foundation of 30x20m which has a thickness of 80 cm. Just as the specification of the housing structure are not provided, the 35 kN/m2 load is too characteristic load with both the live and dead loads.

Lastly is the retaining wall. This is a building structure that is constructed to hold back water or earth so as to ensure that the water or earth levels differ on both sides. When retaining the earth, retention wall is useful when the scope required is steeper compared to what the earth would naturally keep. This is based on the materials in question and in most cases, the earth around the site of construction. These retaining walls are mostly used while withholding vertical or near vertical scope or even a steep earth. As per the project, the retaining wall is needed in the northern boundary of the pump structure site for purposes of preventing six-meter high earth from falling entirely and potentially causing damage to the pumping equipment and structures. As per the report, to achieve the purpose of the retaining wall, these are a suggestion of a number of possible options. The two main types of retaining wall are embedded wall which are walls that penetrate into the surface and usually relies on significantly on the resistance of the earth for the support. Another wall is gravity wall which is constructed to overcome the soil lateral pressure when there are desired changes in ground elevation that seem to exceed the repose of the soil.

Some of the features of Embedded Walls include:

Support Earth

Utilized when the retaining height is relatively low

Constructed of steel sheet piling

Used as a permanent/temporary support

Stability results primarily from the passive resistance of the soil over the embedded

On the other hand, gravity walls are;

Regarded as uneconomical beyond the height of 3 meters

Traditionally constructed of mass concrete

Achieve stability as a result of the structure's weight and the resistance to earth pressure.