Zambia

Click here to download the full report - an analysis of the cost-effectiveness of borehole drilling in Zambia.

The executive summay is given below:

Executive Summary

Context

The National Rural Water Supply and Sanitation Programme, (NRWSSP) in Zambia intends to construct over 10,000 new water points by 2015 of which UNICEF alone intends to construct 3,650 water points in the next five years. The Danish Government through Danida will also contribute a similar number. Boreholes in rural areas are normally drilled for handpump supplies. Drilling can take place for most of the year, to tap relatively shallow aquifers (between 24m and 85m).

Responsibility for rural water resource development is with the Ministry of Local Government and Housing (MLGH). The Department of Water Affairs (DWA) of the Ministry of Energy and Water Development still owns drilling equipment and there is a considerable knowledge base in the organisation (e.g. in hydrogeology and records). No guidelines and procedures have been developed to direct borehole drilling in Zambia although standard ways of borehole construction have been developed and adopted as a good practice by DWA.

Geology and Hydrogeology

The geology of Zambia, comprises various rock formations consisting of igneous, sedimentary and metamorphic rocks from Precambrian to recent times. In Zambia, aquifers can be broadly categorised into three groups:

• Aquifers where Groundwater flow is mainly in fissures, channels and discontinuities, which are subdivided into highly productive and locally productive aquifers;
• Aquifers where intergranular groundwater flow is dominant
• Low yielding aquifers with limited potential:

The price of a completed borehole in Zambia tends to be in the range of $4,000 to $5,000 although it can be double this for some donor-aided projects.

Analysis of the Cost-Effectiveness of Current Drilling Practices

Who Drills?:

DWA owns over 30 sets of drilling equipment, including rigs recently received from JICA. DWA drills throughout the country, including for private clients. DWA charges $3,000 to $3,500 to drill 100m, but the equipment costs have been undervalued; a sum of $500 goes to DWA for the equipment. As this is below market rates, DWA private drilling is effectively subsidised.

There are many national private water well drilling contractors in Zambia but no register or licensing of drillers. It is reported that many “brief case consortia” have been formed in response to tenders. Regulation of the drilling industry is seriously lacking. There is also no drillers association.

Procurement:

Presently, substantial drilling programmes let out large contracts (of > 100 boreholes) which tends to favour larger companies and excludes small, yet competent drilling enterprises. A mechanism to enable small companies to participate would be to promote a drillers pool, with roll-over packages of work. This would enable contractors to work for more work as high quality and timely construction would win new work. Contractors with multiple rigs can take on several packages; those with one rig can work according to their capacity. Tender meetings to informed drilling contractors of expected conditions and describe the categories of risk are not currently utilised in Zambia.

Contract Management, Supervision and Payment:

With the exception of UNICEF’s standard “service orders”, tender and contract documents for borehole drilling in Zambia are long, complex, and thus unlikely fully understood or even read entirely by the drilling contractor. Such contracts are un-appropriate and not necessary and could be significantly simplified. Boreholes which have been signed off as successful sometimes becomes dry within a short time due to poor quality construction. Unlike in other countries, there is generally no defects liability for borehole drilling in Zambia and the process of acceptance of the borehole drilling works varies.

In cases where contracts are paid under a “no water no pay” agreement, it is importance that the risk of the borehole being dry is determined.  The study proposes a mechanism whereby three categories are used to define the risk: high (>90% success rate); medium (60-90% success rate) and low (<60% success rate). Each category has a particular proposed payment mechanism.

Poor supervision is one reason for borehole failure and in Zambia itself UNICEF has been criticised for ineffective supervision. In Zambia there is a lack of competent and experienced drilling supervisors and there appears to be a continual reduction in their numbers over time.

In order to obtain the minimal yield of 0.2 litres per second specified for handpumps in the Zambian national standard it is not always necessary to use geophysical equipment in order to maximise the yield. Under current procedures in Zambia (MLGH DISS Supplementary module 2f Borehole Standard and Construction Details 2002) the community selects areas in which the hydrogeologist identifies the actual drill site. However, there is scope to further strengthen this.

Drilling Technology:

There has been experience gained in Zambia of rehabilitating and further developing hand-dug wells by drilling a further 10 or 20 meters within the well to pick up more water. The large diameter open well in the upper area still serves as enhanced water storage.  With the deepening complete then a reinforced cover slab and hand-pump is installed.

With aquifers at depths between 24m and 85m, borehole drilling in Zambia is relatively shallow, to a depth of 60m on average, and certainly less than 100m. Drilling in rural areas is mostly undertaken for hand-pump supplies. However most of the drilling rigs presently active are heavier than required as they are suited to drill larger diameters to several hundred meters. Only two lightweight PAT rigs were found operating in the country. Through the consultants discussions it was clear that stakeholders in Zambia have little awareness of light rigs.

Hydro-fracturing: is a system where water under extremely high pressure is forced into an otherwise dry or near dry bore which opens then up fractures and fissures to improve yields. This technology has been proven in several countries. There are areas of Zambia which would benefit from it but it is not well known. 

Borehole Design and Construction:

There is no national standard borehole specification for Zambia. The handbook entitled “Borehole Standard Construction and Details” 2002 indicates that finished diameters should be 4 inch for handpumps and 6 inch for motorised units. In practice, most specifications are 4 inch diameter casing in a 6.5 inch (165 mm) diameter hole but Danida and German Government funded projects both currently specify 8 inch (312 mm) diameter drilled boreholes and the current JICA-funded programme formation, specifies drilled diameters of 7.8 inch (200mm) to 9.75 inch (250mm). One of the reasons for these large diameters is apparently lack of confidence in the drillers to do a good job and in the ability of supervisors to ensure that satisfactory work is achieved. This raises fundamental questions about the pre-qualification and contract management processes being followed, as well as the skills and management of drilling supervision.

There are three general drilling techniques to achieve boreholes suitable for hand-pumps in Zambia:

• Mud-circulation boring 6.5”diameter drilling and 4” diameter casing to full depth in unconsolidated (sedimentary) ground.
• Air-percussion boring 6.5”diameter drilling and 4”diameter casing to full depth in consolidated (rock) ground; in certain fractured ground it is feasible to bore 6.5” install 5” permanent surface casing then drill 4.5” open hole (i.e. uncased) to final depth.
• Combination boring Mud-circulation drilling at 6.5” diameter through collapsible over-burden to rock, install 5” casing then air percussion drill at 4.5” diameter open hole (i.e. uncased).

There is currently no consensus as to whether all boreholes should be cased to the bottom irrespective of natural rock lining, although the common practice is to case fully. Many professionals are of the opinion that aquifers above 20m are not likely to yield sustainable supplies throughout the year but there are areas where shallow wells and hand drilled tube-wells do supply water throughout the year.

Some 30% of Zambia’s land area, has very fine grain “Kalahari Sands” which are particularly difficult to drill and case. Historically drilling in these areas has involved large diameter, mud-circulation drilling with large diameters specified to enable good gravel packing without bridging. However experience from other countries shows that such fine grained material can also successfully be completed when bored at a smaller diameter.

The “tremmie pipe” is reportedly not used in Zambia to install gravel pack. In addition filter socks are not well known in Zambia. 

Well Development, Test Pumping and Water Quality Analysis:

There appears to be a tendency to over-specify borehole development and test pumping requirements although these aspects are not always adequately undertaken by the drillers. If the driller does not properly flush the screen and gravel pack area, this can result in reduced borehole efficiency and lead to blocking of the screen over time.

Data and Reporting:

Presently, various drilling programmes and entities in Zambia use their own format for drilling completion and a standardised drilling completion format for the country has yet to be established.

Database and Record Keeping:

A pilot project to establish a database of all borehole drilling is presently being piloted for Southern Province under German funding. Specific key data is abstracted from the Completion Reports and entered onto the Database. This pilot needs to be reviewed and extended nationally. It should be obligatory that all drilling programmes collate and present input for database entry. The national database needs to be properly established, kept up to data, be readily accessible to all, and ensure that there is no duplication of data entry (i.e. by using the individual borehole identification number and GPS information). 

Conclusions and Recommendations

Please download the full report for a list of the specific conclusions and recommendations.

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