Clareville Water Treatment Plant

Introduction

Limerick City's water treatment plant at Clareville is located on the banks of the Shannon near Castleconnell.  Water has been treated on the site since the end of the 19th century, and the facility has been extended at various times to meet the growing demands of the city.

First Phase

The first phase of the treatment complex was completed in the 1890's and utilized the Shannon as a source of both raw water and power.  It comprised of slow sand filters, a headrace and a tailrace canal and a pumphouse containing water driven turbines and reciprocating pumps, capable of delivering 1.5 million gallons/day (70,000m3/day) to a 5 million gallon (22,000m3) open reservoir at Newcastle, Castletroy.  The site was chosen to make use of the head available on the river to power the pumping plant.  The headrace canal took water from upstream of the Falls of Doonass, a famous beauty spot and salmon fishery, used the water to power the turbines and returned it at the level of the tailrace canal.

The pumping arrangement, while no longer in operation, is still an excellent state of preservation.  It is worth examining the equipment, which was made in Limerick and bears testament to the engineering skills of the city.  The pumphouse has been restored and will be maintained as a record of past achievements.

Second Phase

The second phase came at the end of the 1920's when the pumping arrangement had to give way because of a more spectacular development on the other side of the river.  Most of the flow in the river was now diverted through a headrace canal running parallel to the north bank of the river near Killaloe to the new Ardnacrusha Hydroelectric Scheme.  The reduced flow in the river could no longer be relied on to drive the turbines, which were replaced by electrically driven pumps, powered by the Ardnacrusha Scheme.  The raw water was then delivered by gravity through a pipeline, which passed under the river, from the higher Ardnacrusha headrace.  The slow sand filters were replaced by a horizontal flow settling tank and rapid gravity filters.  Chemical dosing was introduced and the capacity of the plant was increased to 2.5 million gallons/day (11,000m3/day).  Over fifty years later, this plant is still in operation.

Latest Phase

In 1951, a further extension was completed increasing the capacity to 3.6 Million gallons/day (16,000m3/day) to cater for the growing demands of the city.  The extension consisted of twinning the filtration plant and adding a circular clarifier for sedimentation.  This arrangement, with modification to plant and chemical dosing, eventually delivered 7 MGD.  However, the plant severely overloaded and the quality of the treated water occasionally suffered.  This over loading, as well as the need to expand to meet the growing demand, led to the construction to the latest phase.

In the late 1970's work was started on the latest stage.  The first contract undertaken involved the reduction of the level of the section of the site used for this phase to that of around the old plant.  The main civil works contractor then carried out the construction of the buildings, tanks and pipelines.  Most of the structures are of reinforced concrete; the extent of the work is not obvious at first sight as a great deal of the construction is underground.  The mechanical plant was supplied and installed under separate specialist contracts.

Present Position

The Water Treatment Plant at Clareville was in urgent need of upgrading in the early nineties, in order to meet the water demands in the city and in the adjacent count areas of Limerick and Clare.  In addition to increased capacity (50mld to 120mld over a 20 year horizon) the plant was in need of upgrading in terms of:

  • Rationalisation of works on the site to achieve a more efficient water production facility;

     

  • Renewal of existing plant assets including tankage, buildings and equipment in order to secure their future satisfactory operation, thereby ensuring a good quality water at all times.

     

  • Upgrading the control systems at the plant to facilitate a greater degree of automation, monitoring and control in order to improve efficiency and cost;

     

  • Develop sustainable sludge treatment and disposal arrangements in order to secure satisfactory outlets for sludge residues at minimum cost.

Traditional Approach

The traditional approach to implementing the upgrading of the Clareville Water Treatment Plant would have involved the following procedures:

  • The development of a scheme design to meet the project requirements, involving full definition of the necessary works to be constructed.  This design would be developed in a preliminary Report, with detailed costings for approval by the Client and the Department of the Environment and Local Government;

     

  • Following approval, the detailed design of the agreed scheme would be carried out and Contract Documents prepared for the separate civil and mechanical/electrical elements of the scheme;

     

  • Tenders would then be invited for the civil and mechanical/electrical contract works and Contracts awarded on the basis of the outcome of the tender process; and

The construction Phase would have then involved the appointed civil and mechanical/electrical contractors carrying out the work detailed in the contracts under the supervision of Resident Engineers representing the Client's interest.  When completed, the plant would then be commissioned and taken over by the Local Authority who would then operate the plant subsequently.

Advantages of Traditional Approach

Historically, this approach was the most satisfactory way of delivering major infrastructure for the following reasons:

  • The client had full control over the design of the plant, which it could specify to its exact requirements;
  • Schemes generally were smaller and involved relatively low level technology so that the correct solution could normally be easily identified by the Engineering Designer on behalf of a Client;
  • The Contracting organisations for both civil and mechanical/electrical works did not usually possess a design capability and their skills were confined to implementing a design provided to them; and
  • By fully specifying the works, it was possible to get prices from all available Contractors in the market with the result that very economic schemes were delivered.

    Disadvantages of Traditional Approach

    In recent years, the traditional approach has been considered less than satisfactory for the delivery of certain projects such as water or wastewater treatment, involving complex process plant and equipment.  The following factors are relevant in this regard:

    • Treatment plants have had to become increasingly sophisticated in order to meet more rigorous performance standards and to take advantage of equipment development and process automation.
    • As new technologies have been developed, proprietary systems have become available which are restricted by patent and may not be covered by a traditional engineering design;
    • The separation of design, construction and operational functions does not lend itself to achieving the best overall solution, when the performance of the scheme over its whole life (construction and operating design life) is considered.  In other works, if the Operator is involved from the beginning with the Builder and Designer, the expertise and experience of each is brought to bear on the solution, bringing benefits which may not be obtained in the traditional arrangement; and
    • Because of the separate design, construction and operational elements, in the traditional approach, claims for additional costs frequently arise, associated with the division of responsibility between the parties and disputes over the level of risk to be catered for in the different Contracts.

    Public Private Partnership

    For these reasons and to satisfy other objectives of public policy, alternative procedures for implementing major schemes such as the Clareville development have evolved.  These comprise Public/Private Partnership (PPP) Contract arrangements whereby the private sector enters into contractual arrangements with the Public Sector Client in order to deliver a more integrated service.   The PPP options which could be used in this case are described as follows:

    • Design and Build (DB) - a contractual relationship between the Public Sector Client and A Private Sector Contractor for the Design and Construction of the facility which is then handed over to the Public Sector to operate that it has been proven to be satisfactorily completed.  In this arrangement, the Contractor is responsible for both the design and construction of the facility to satisfy prescribed criteria laid down in the Contract Document;
    • Design, Build and Operate (DBO) - a contractual relationship between the Public Sector Client and a Private Sector Contractor for the Design, Construction and Operation of the Treatment Plant.  The construction of the plant would be financed by the Public Sector but responsibility for the operation of the plant would rest with the Contractor for a defined period of time.  Ownership of the plant would always remain with the Public Sector; and
    • Design, Build Operate and Finance (DBOF) - a contractual relationship between the Public Sector Client and a Private Sector Contractor for the Design, Construction, Operation and Financing of the plant.  In this case, the Contractor would be responsible for Designing, Building and Operating the plant as for a DBO Contract but would also arrange for the financing to cover the construction cost of the facility, which would be paid back over the operating life of the project.  Ownership of the plant would remain with the Public Sector but the Contractor would have a licence to operate the plant for a defined period which should enable it to recover its investment, repay the financing and meet the operating cost.

    These PPP alternatives to the traditional approach have been considered in a PPP Assessment in order to select the optimum arrangement for the Clareville WTP upgrading, particularly in terms of best value for money.

    The DBO option was preferred for Clareville Water Treatment Plant and a contractor has been in operation on the site since 2007.  The upgrading of the Plant was officially opened on 25th June 2010.  For Further information please read the attached brochure.

   Clarville Water Treatment Plant Refurbishment DBO Project (PDF - 1,676 Kb)
    Brochure for Clareville Water Treatment Plant Refurbishment

   The Limerick Waterworks Extension (EPS - 5,059 Kb)
    Extract from Historical Publication by The Institute of Civil Engineers of Ireland, 1954

David Keane
Senior Engineer
Water Services Department
Phone: (061) 407179
email: dkeane@limerickcity.ie


Last update:26/04/2013

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