AN article in the Sunday Observer of 14th November 2010 titled ‘Water Foul-Up in Santa Cruz, Authorities blasted for siting well in a swamp’ cited the Water Resources Authority (WRA) as the agency responsible for the siting of the well.

The article quoted one Councillor Donovan Pagan as asking “why would the experts put a well in a swamp?”

In an editorial of Monday 15th November 2010 the Daily Observer quoted Mr Jeremy Palmer, mayor of Black River, as saying that it was not his belief that the experts “did sufficient due diligence or looked at the history of flooding in the area” before establishing the well.

There is clearly a misunderstanding of the factors behind the location of the Santa Cruz #2 well, the issues with the well, and how the well can be brought back into service within a short time.

In this response I will speak to four issues:

1) Siting of the well — who, when, why;

2) Flooding in the area of the well;

3) Water quality; and

4) Restoring the well to full productivity.

Siting of the well

Contrary to the statement attributed to Ava-Marie Ingram of the National Water Commission’s (NWC’s) Western Region, the well was not sited by the Water Resources Authority (WRA). The Santa Cruz #2 well was sited in August 1991 by a hydrogeologist at the NWC. The well is located at the southern boundary but outside the Upper Morass or Black River Swamp. In a report dated 16th August 1991, the NWC’s hydrogeologist detailed the site selection process which included both hydrogeologic and water quality factors.

The hydrogeologic factors include

a) Tapping the productive and highly Karstic limestone aquifer;

b) The availability of adequate resources in the aquifer; and

c) The presence of geologic features/structures to enhance success.

The water quality assessment of the site was based on the location being outside the town limits and the influence of sewage soakaway systems which are used for sewage disposal in Santa Cruz, sparse agricultural development up gradient of the site and data for existing wells tapping the same aquifer.

The then Underground Water Authority (UWA), the predecessor of the WRA, reviewed the site selection and in November 1991 granted a licence to drill the well with conditions for further evaluation of the water quality from samples to be collected during the yield testing of the well.

The well was drilled, yield and water quality tested by 9th December 1991.

The well tapped the limestone formation and was constructed to a depth of 65.5m (215ft) and completed with 40.64cm (16ins) diameter steel casing. The water level was 3.66m (12ft) below ground level. The steel casing was extended 0.6m (2ft) above ground level and the annular space (space between the casing and the limestone formation) sealed with cement extending 1.2m (4ft) below and 0.3m (1ft) above ground to prevent any ingress of surface water such as from flooding.

The yield test confirmed a yield performance of 2,492m3/d/m pumping at 8,730m3/d with a drawdown of 3.5m (11.5ft). The NWC was seeking 9,080m3/d which could be sustained by the well with a 3.6m (11.8ft) drawdown.

The water quality analyses of samples collected during the yield testing of the well indicated typical calcium bicarbonate type water (best water quality type in Jamaica) with all parameters meeting the World Health Organisation (WHO) drinking water guidelines. Turbidity varied from 0.85 to 1.8 Nephelometric Turbidity Units (NTU) which was within the 5 NTU recommended by the WHO. Bacteria quality showed no faecal contamination and the total coliform count was 16MPN/100ml. The water was classified as Class 1 water with simple chlorination required before public use.

The licence was granted on 28 February 1992 to abstract and use 9,080m3/d or 2migd of water to meet the domestic demand of Santa Cruz. The well was completed and capped, waiting commissioning.

The well yielded the volume of water required with no water quality problems

Flooding in the Content area

The NWC/UWA in 1991 recognised the potential for flooding at the well site and took the following steps:

a) Located the well atop a high piece of ground.

b) Extended the casing above ground level and sealed with concrete the annular space preventing any entry of water into the well.

During the recent flooding associated with Tropical Depression 16 (which later became Tropical Storm Nicole) and contrary to reports in the Sunday Observer, the well was not flooded nor was the pump impacted by floodwaters. The access road to the well site was flooded, preventing NWC and WRA personnel from reaching the well.

While the surrounding area was flooded, the subsurface lithology, as proven by the lithologic log of the well and which consisted of nearly 15.25m (50ft) of clay atop the limestone, would prevent floodwaters entering the aquifer at Content.

In 2003, the WRA completed a hydrologic flood analysis of the Upper Morass for the National Irrigation Commission (NIC). The flood maps indicated that the well site was above the floodwaters for various flood events greater than that associated with TD 16 and was at an elevation above the dike at the Black River over which water would flow before the well is flooded. It must be pointed out that the flood levels in the Black River during September were the highest recorded at Newton and Appleton since the collection of data began 56 years ago.

The rains and flooding from TD16 had no impact on the Santa Cruz #2 well and pump at Content.

Water Quality Issues

The main water quality issue at the Santa Cruz #2 well has been the turbidity levels. Though they are within the WHO and the Interim Jamaica Standards (IJAM) levels for drinking water (5 NTU) the criterion for disinfection efficiency of 1 NTU was not met.

In June 2004, before the well was commissioned into operations, the WRA recommended to the NWC that the well be telelogged to determine the condition before installation of the pump. A telelog is a diagnostic tool where a camera with a light is use to record the condition of the well (similar to a colonoscopy). The NWC accepted the recommendation and the WRA did the telelog. The telelog report showed the following:

1) Some 3.35m (11ft) of the well had back-filled.

2) Incrustations were seen on the casing of the well which were identified as calcium carbonate deposits (from the calcium enriched water) and black deposits of iron bacteria. The bottom 9m (30ft) of the well had calcium carbonate incrustations with black deposits of suspected iron bacteria.

The WRA recommended action to be taken to clean the well. The NWC executed this action by 12 December 2004.

The final stage in the action plan was to pump the well to waste for 72 continuous hours to remove the chemicals and the back-filled material while monitoring water quality. At the end of the 72 hours pumping, the bacteria count declined from 49 to zero and the turbidity from 7.4 to 2.9 NTU. All other parameters met the drinking water guidelines/standards.

The well was then commissioned into service.

Restoring the well to full production

The WRA is now working with the NWC to restore the well through a programme of telelogging, cleaning, disinfection and development by pumping. This can be completed within 2-3 weeks. The expenditure for the Santa Cruz Water Supply Project will not be lost (as was reported in the article) as once the well is returned to operations the transmission pipeline and all installations will be fully used.

The source of the reported high iron concentration (>1mgl) and smell of hydrogen sulphide (resulting from the iron bacteria) is not harmful to health and can be easily treated. Iron is considered a secondary or aesthetic contaminant and occurs worldwide and in other areas of Jamaica. The proper treatment and disposal of effluent is critical to reducing the incidents of iron bacteria contamination in water resources.

The water quality problem, while it is manifested at the well, is within the aquifer. This has occurred since the well was drilled in 1991. The source could be either from organic matter in the Upper Morass or from industrial effluent discharged into the limestone aquifer up gradient (to the north) of the well site. Groundwater movement is from north to south in the basin.

The Upper Morass is underlain by the peat aquiclude and there is no vertical movement of water through the aquiclude, hence the ponding of water atop the peat to form the morass or swamp. An aquiclude is a rock formation with insufficient permeability and low transmissivity to support perennial well or spring yield. The aquiclude underlying the Upper Morass is one of the reasons for the rapid and frequent flooding of New River.

Industrial effluent from the sugar/rum industry has been discharged into a sinkhole up gradient of the site for many years, contaminating the limestone aquifer and the north Elim River. This industrial effluent would contaminate water resources with high odour, discoloration and bacterial growth (as it moves with the groundwater southerly) as has occurred in the Queen of Spain Valley in Trelawny and at Lluidas Vale.

In the Queen of Spain valley several NWC wells have had to be removed from operations due to the impact of dunder from Hampden Estate. Members of the Jamaica Caving Club can attest to the high hydrogen sulphide concentration in the Riverhead Cave where the Rio Cobre rises after sinking at Lluidas Vale in St Catherine.

The next steps to be taken are:

1) Analyse well water samples to more comprehensively characterise the contaminant and determine the source;

2) Work with NEPA to remove the source of the contaminant;

3) Return the well to service ASAP using chemical treatment and surging while monitoring water quality; and

4) Implement an operational, treatment and maintenance plan to ensure water quality is always of a high level.

Conclusion

The Santa Cruz #2 well was drilled in 1991 and was successful in providing an adequate supply of high quality water. The location of the well is not in a swamp and due diligence has been followed in the location, drilling, yield and water quality testing of the well.

The well can easily be brought back into service and high water quality be ensured by implementing an operational plan with the proper treatment.

The Water Resources Authority will continue to provide strong technical support in the management and development of the island’s water resources.

It is hoped that the above, though lengthy, will have cleared the air on the matter of the Santa Cruz #2 well.

— Basil Fernandez is managing director of the Water Resources Authority