OR/15/009 Recommendations

Lapworth D J, Carter R C, Pedley S and MacDonald A M. 2015. Threats to groundwater supplies from contamination in Sierra Leone, with special reference to Ebola care facilities. British Geological Survey Internal Report, OR/15/009.

Appropriate designs to increase the protection of Ebola healthcare facility water supplies

• To protect groundwater sources from pathogenic pollution there are three broad design and construction responses possible:
• Define and protect “catchments” of springs, wells and boreholes from diffuse pollution (by way of protection zones);
• Contain and treat human wastes effectively on- or off-site (by appropriate sanitation technology choices);
• Address design, location and construction aspects of hand-dug wells and boreholes in order to reduce or eliminate the risk of localised pollution directly to the water point.

Comprehensive source protection of catchment zones is challenging and is not a realistic option for most water points in Sierra Leone, and therefore remains a long term option. Improved sanitation and improved water point construction are more attainable in the short-to medium term and this is where efforts should be focussed now.

Sanitation

In the absence of any realistic short- to medium-term possibility of developing sewerage and sewage treatment, only two options remain: septic tanks with drain fields or constructed wetlands; or conventional on-site sanitation using pit latrines. The first of these is a relatively high-cost option which demands significant space. It is only realistically possible in limited circumstances.

Given Sierra Leone’s extremely low levels of improved sanitation coverage (Table 1), an ambitious target would be to reduce the presence of human excreta in the environment by significantly improving access to improved latrines at the household level and shared latrines in dense settlements. From a purely technical viewpoint, ecological sanitation at household level in dense settlements would appear to be an attractive possibility, but its success would depend greatly on public perceptions and attitudes. A few organisations have implemented ecosan projects in Sierra Leone, and it would be important to review their outcomes and sustainability to inform any subsequent activities.

Water supply from groundwater

The most common water point type in Sierra Leone is the hand-dug well (64% of all improved water points), with or without a handpump. Design and construction guidance tailored for the Sierra Leone context was recently published (Ministry of Water Resources 2014a). Issues such as location relative to latrines (guide distance of 30m or more), timing of construction in relation to seasons, use of dewatering pumps, and construction of protective headworks are all addressed. Major issues regarding hand-dug wells in Sierra Leone are:

• The high proportion which are seasonal (approximately 50%). The implication is that consumers are driven to alternative (possibly inferior) sources, including surface water and swamps, in the dry season;
• The large proportion (45%) which are accessed by bucket-and-rope (without a winch), easily permitting pollution directly via the well shaft;
• The high breakdown rate of handpumps (the water-point mapping revealed 60% ‘snapshot’ functionality for handpumps), so adding even more to the number of wells which are accessed by bucket-and-rope.
• The high rates of pathogenic contamination found in hand dug wells in some studies

We do not know (and it would be difficult to ascertain) what proportion of hand-dug wells have adequate low-permeability annular backfill.

Boreholes make up 7% of the nearly 29 000 water points which were mapped by WSP (2012). Recent activity by Swiss consultancy Skat under the umbrella of RWSN and funded through DFID’s WASH Facility has included the promotion of RWSN’s Cost-effective Boreholes Code of Practice. A number of training activities have been carried out, and a guidance document published (Ministry of Water Resources, 2014b).

Issues related to Sierra Leone’s water supply boreholes include:

• The challenges around handpump maintenance, as for hand-dug wells;
• The 34% of boreholes with handpumps which are reported as being seasonal. This may be partly an issue regarding siting, and partly due to the commissioning of low-yielding boreholes which should not have been put into service;
• The very likely poor construction standards, given the absence of adequate supervision, and an Africa-wide tendency to undervalue the importance of sanitary seals.

The design and construction details of spring boxes are well-known. Only 1% of water points surveyed in the 2012 water point mapping (WSP, 2012) fell into this category, although a further 26% of water points are described as ‘standpipe or tapstand’. How many of these are spring-fed is not known.

A key recommendation of this report is for donors and Government to invest urgently in extending and improving sanitation through tried-and-tested technology options. Over time this would significantly reduce the pathogen load in the urban and rural environment, leading to the possibility of reduced faecal-oral disease. Priority recommendations for groundwater supply in Sierra Leone are to focus on issues pertaining to siting, design, construction quality and maintenance of hand-dug wells and boreholes with and without handpumps. Extending safe, reliable and sustainable groundwater services will reduce the present high dependence on unsafe surface water sources. High priority should be given to extending the coverage of improved water supply from well- sited, designed and constructed groundwater sources. At least as much effort will need to be expended on ensuring the effective utilisation, repair and maintenance of the services provided by such infrastructure. Operational research should focus on the institutional, governance, political, cultural, financial and socio-economic obstacles to achieving scale-up of truly sustainable services.

Risk assessment of water points for Ebola care facilities and community water points down gradient of healthcare facilites

A simple site assessment is currently being used to assess risks within close proximity to water points at and around Ebola care facilities (see Ministry of Water Resources 2015b). The proposals outlined below build on and extend this approach.

Based on the evidence from this desk study we recommend that local risk assessments are carried out for water points that supply care facilities and community water points down gradient or in close proximity (possibly up to 200 m) to the treatment facility. This larger radial search reflects the potentially rapid pathways in shallow horizons and the need to better quantify the density of hazard sources in the vicinity of water points. We suggest that an initial assessment is carried out as soon as possible, ideally within the next 3-6 months that includes a sanitary risk assessment and water quality assessment. Longer term monitoring (6-24 months) for water quality should be carried out during the wet and dry season for a minimum of two seasons to establish water quality from these water sources, seasonal water table fluctuations and an assessment of risks from rapid pathways should be also carried out.

A framework for the risk assessment to characterise the sources and pathways for contamination of water points in the short and longer term is outlined below:

In the short term (3-6 months): A full sanitary risk inspection (targeting sources within a 30 m radius of the water point) and pollution assessment should be made at each water point during both the wet and dry season. This should be undertaken by assessors after appropriate training An assessment of hazard sources within a 200 m radius of the water point, including point and multi-point sources such as open defecation, to identify the key contamination sources and their densities. This should be carried out in both the wet and dry season. An assessment of the design, construction and integrity of the water point, paying particular attention to protection against rapid surface and sub-surface transport routes. This could include examining drilling and construction reports or using downhole cameras to inspect casing integrity. Water quality analysis of key water quality parameters at each water point should be undertaken, including as a minimum: TTC, turbidity, specific electrical conductivity and pH, which then continues for a minimum of two dry and two wet season sampling rounds. In the longer term (6-24 months): An assessment of the seasonal changes in depth to groundwater should be undertaken for a minimum of one full hydrological cycle, ideally using automatic water level loggers to capture rapid seasonal changes in response to rainfall as well as regular manual dips. An assessment of rapid shallow subsurface pathways within a 200 m radius. This includes an assessment of the geological and soil conditions paying particular attention to shallow permeable layers that can be activated during the wet season under intense rainfall and high water table conditions. Continued water quality analysis for at least two wet and dry seasons. A full inorganic chemical analysis should be carried out on at least one occasion.

In the short term, if water points are found to have faecal contamination then either treatment or the provision of an alternative safe source for drinking water is required. For community water points, household treatment is recommended, while for larger sources, such as boreholes for care facilities, treatment at source may be required. In the long term alternative water points such as deep boreholes that have less risk of contamination need to be considered.

Evidence gaps for understanding risks to groundwater sources

This desk study has highlighted the that there are few high quality combined hydrogeological and water quality studies that have been carried out in Africa, and there is limited evidence from local studies in Sierra Leone on hydrogeological conditions from which to draw strong conclusions. As a consequence, this report has relied heavily on evidence from analogous regions. Groundwater monitoring is now being undertaken in Sierra Leone as part of the DFID funded Water Security project and is beginning to generate some useful data on links between rainfall, groundwater levels and river flow.

Given the important role rapid horizontal (and vertical) pathways in tropical soils have in the migration of contaminants in the subsurface, and their widespread occurrence in this region, and Africa more generally, this is a key topic that warrants further investigation.

Even by African standards, the failure rate of water sources is high in Sierra Leone. Research focused on understanding the factors controlling the high failure rates (hydrogeological or otherwise) of shallow groundwater sources in the dry season would be beneficial.

A baseline assessment of water quality status and sanitary risks in Sierra Leone using a robust survey approach is needed to address the limited local evidence currently available. For example, this could take the form of wet and dry season campaigns for wells vs boreholes, improved vs unimproved sources in contrasting high risk and low risk hydrogeological terrains in Sierra Leone.

Tracing and quantifying residence times and pathogen occurrence in the subsurface, including in shallow groundwater systems as well as deeper systems is key to making a robust assessment of the vertical separation required between sources of pollution and groundwater points.

New techniques such as molecular marker methods (e.g. Mattioli et al., 2012) for fingerprinting pathogens, fluorescence sensors for rapidly mapping microbiological contamination of water sources (e.g. Sorensen et al., 2015b), and attention on type/depth of water point may help resolve key sources and pathways for contamination of groundwater points in this region.