PHYSICAL FACILITY & OPERATIONS
The National Water Commission produces more than 90% of Jamaica's total potable water supply from a network of more than 160 underground wells, over 116 river sources (via water treatment plants) and 147 springs. The Parish Councils, The Runaway Bay Water Company and the Four Rivers Development Company, and a small number of other private water companies provide the rest of the potable water supply, while The National Irrigation Commission provides irrigation services.
Approximately 30% of the water abstracted in Jamaica is used to meet the demand for potable water and the remaining 70% is used for irrigation.
The NWC operates more than 1,000 water supply and over 100 sewerage facilities islandwide. These vary from large raw water storage reservoirs at Hermitage and Mona in St. Andrew and the Great River treatment plant in St. James, to medium sized and small diesel-driven pumping installations serving rural towns and villages across Jamaica.
Approximately 70% of Jamaica's population is supplied via house connections from the National Water Commission and the remaining 30% obtains water from standpipes, water trucks, wayside tanks, community catchment tanks, rainwater catchment tanks and direct access to rivers and streams.
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Approximately 30% of Jamaica's population is served by sewerage facilities operated by the NWC. This includes some small sewerage systems, utilizing package plants, which are associated with housing developments in various locations throughout the country. The disposal of the sewage generated in the remainder of the population is done through various types of on-site systems such as septic tanks, soak-away pits, tile fields and pit latrines or other systems operated by other entities.
The NWC facilities also include over 10,000 kilometres of pipelines and more than 1,000 kilometres of sewer mains across the island. From rivers, springs and wells, the NWC supplies some 190 million gallons of potable water each day to persons across Jamaica.
Water is what the National Water Commission (NWC) is all about. It is its raw material and its end product. We collect, refine and distribute the purified commodity to industrial and domestic consumers over a hilly land area of 10,990 square kilometres. This is a huge and costly responsibility that must be carried out as the Commission seeks to provide potable water supply services for 2.7 million Jamaicans, plus visitors to the island, in addition to the collection, treatment and disposal of wastewater.
The NWC operates within the policy context of the Government of Jamaica's goal of universal access to potable water by the year 2025 and the establishment of sewerage systems in all major towns by 2020. This presents a serious challenge for the NWC because proper water supply and wastewater services are highly involved, complex, and costly, and become even graver when coupled with the difficulties in collecting revenue that limit the availability of funds for timely improvement, expansion and maintenance operations.
This responsibility is also a serious challenge because, despite Jamaica being blessed with excellent and relatively abundant water sources, the areas of high water demand are often far away from the required water resources. A community such as Mandeville, in Manchester, is one example of an area that is without a reliable water source and therefore has to be supplied from water sources near the Clarendon border and in St. Elizabeth. Similarly, Kingston and St. Andrew is provided with much of its water from St. Catherine and St. Thomas. Many water sources also do not provide a guaranteed year-round yield. Additionally, the often mountainous and rugged terrain over which water distribution systems have to operate presents significant challenges and saddles the Commission with very high electricity bills as electrical equipment is used to pump water to these hilly areas.
Despite the many challenges, the NWC recognizes that water is essential for national development and has undertaken a number of projects to continue its drive to bring water to more communities and improve service in existing areas. These projects include the development of new water supply and wastewater treatment plants islandwide as well as the rehabilitation and upgrading of existing facilities. The NWC's infrastructure expansion now facilitates water supply systems that pump water over rugged and wooded terrain, to numerous hilly and low-lying towns and districts, which previously had no piped water service.
Water Supply Facilities and Sewerage Treatment Plants
Gallery
The Constant Spring Treatment Plant
Water Supply Facilities and Sewerage Treatment Plants
In February 1944, the Water Commission recognized the urgent need to find an additional source of supply. As far back as 1939, plans had been prepared for a reservoir on the Mona Commons to meet the growing demands. The design envisaged a basin with a capacity of 700 million gallons flanked by the Long Mountain on one side, the remaining three sides being enclosed by an earthen embankment about 35 feet high. Surplus water from the Hope River was to be conveyed to the reservoir through a tunnel and aqueduct for a distance of about two miles from the river intake.
The story of Mona has often been told, with distortions or inaccuracies creeping in with the repetitions. The following is a brief account of its construction, its vicissitudes and the position today:
Work was started in November, 1940, on the improving the Old Hope River intake works and constructing the necessary conduits, silt traps and tunnel to diver the flood waters of the river to the basin. These undertakings were financed from the Commission's resources and were completed in about eighteen months after which a start was made on clearing the actual site of the reservoir itself. In 1942 a grant from the funds of the project to be completed but under Government control; the Water Commission being relieved of all responsibility in respect to the construction.
Water was first turned into the basin towards the end of 1946 but so dry was the following year that it was not until June, 1948, that the reservoir was filled to capacity for the first time.
Subsequent tests quickly revealed leakage's so serious as to render the structure almost useless for effective water storage. Consulting Engineers, Soil Experts and other Authorities were called in by Government and after exhaustive tests and experiments the entire bottom of the reservoir was lined in 1955 with a specially prepared, compacted soil blanket. The basin was refilled but once again it was found that, although the leakage had been much reduced, it was still greater than could be tolerated.
For three more years Mona's fate was studied and debated by Government and their advisers. Finally in June 1958 Government handed the entire project over to the Commission and divested themselves of all further responsibility. Immediately the Commission commenced the necessary treatment of the sides of the basin and this work was completed by January of the following year. The bottom, however, was found to be still leaking and further repairs to this were necessary before the reservoir could be finally commissioned. These were completed and the reservoir was finally brought into service in October 1959.
The Mona Water Treatment Plant is a 15 migd direct (rapid gravity) filtration plant. Water for treatment can be drawn from the Mona Reservoir through the Drawoff Tower (modified during construction of the project), directly from the Yallahs Pipeline or by a combination of both.
Raw water entering the plant is pre-chlorinated in a flow mixing chamber before it enters the Rapid Mix Chamber. Here the appropriate dosage of alum is added to "coagulate" the particulate impurities (facilities were provided at the plant for dosing of a polyelectrolyte coagulant aid but these have seldom been used and indeed at times these facilities have been used to dose Activated Carbon to assist in dealing with the algal blooms that occur from time to time in the Mona Reservoir). Flocculation follows rapid mixing after which water is led to the 6 filter beds (originally dual sand and anthracite media) where filtration takes place to remove particulate matter. The filters are cleaned via a reverse flow of first air and then treated water.
Filter water is then disinfected with a further chlorine dose and flows to the 2.5 migd clear water post-tensioned reinforced concrete reservoir.
From the reservoir a 36" dia. trunk distribution main conveys water into the overall Kingston water Distribution System (primarily to East Kings House Gate and down Old Hope Road to Stanton Terrace).
Construction of the Yallahs Pipeline Scheme commenced in September 1983 and it was commissioned into service in February 1986. The scheme design provided for an estimated average annual yield of 16.4 million imperial gallons per day (migd). The initial pipeline capacity was proved at 23 migd shortly after commissioning but was expected to reduce on aging to some 20 migd.
The scheme comprises:
Run-of-the-river intakes (i.e. there is no water storage behind the intake structures) on each of the Yallahs and Negro Rivers - at approximate elevations of 900ft. and 930 ft. respectively above mean sea level (amsl). Each intake was designed to abstract up to 20 migd. Both intakes incorporate a Transverse Bottom Intake Section fitted with closely spaced grid bars to exclude larger river "bed-load" particles. The Yallahs Intake was constructed as an earthfill structure founded on river alluvium (with a very low profile so as not to present a major obstruction to the massive flood flows that can be experienced on that river). The Negro Intake is an ogee crest of mass concrete with significant river training works either side (to direct low flows to the short intake grid while allowing flood flows a wide cross section over which to spill).
Water from each intake is transported some 2000 ft. downstream (by 32" and 32'/24" dia. steel pipes respectively) to the "Equalizing Chamber" adjacent to the confluence of the two rivers. Silt basins are located on each intake pipeline to allow sediments entering the transverse intake grids to settle out prior to the water entering the main pipeline at the Equalizing Chamber (at Riverhead, St. Thomas). Any excess flows abstracted at the intakes can be returned to the rivers at either of the two settling basins or at the Equalizing Chamber.
The Yallahs Pipeline - some nineteen (19) miles long from the intakes to the Mona Water Treatment Plant constructed throughout in steel. From the confluence of the two rivers at Riverhead, a 38" dia. steel pipeline transports the water approximately 32,000 ft down the Yallahs Valley and hence westwards up to Cambridge Hill - with three (3) steel truss bridges carrying the pipeline over the Yallahs River en-route. Each pipe bridge is approximately 180 ft. long.
At Cambridge Hill the pipeline enters the 1104 ft. long Cambridge Hill Tunnel at an elevation of some 800 ft. amsl. The 7-ft. dia. tunnel is approximately 150 ft. below the high point of the hill and was hand "drilled" through the Shale formation.
At the western tunnel portal, the pipeline diameter reduces to 36" and this size runs a further 48,000-ft. through the hills abutting the southern coastline into the Hope River Gorge. The pipeline descends from elevations in excess of 600 ft. to cross beneath the Cane and Hope Rivers and terminates at a "high point" in the Gorge at 640-ft. amsl. At the low points along this section of the route operating pressures within the pipeline are close to 750 ft. (some 325 pounds per square inch).
At the "high point" in the Gorge, the pipeline diameter is again reduced - to 32" and some 15,000 ft of pipe runs through the Gorge on the northern slope of Long Mountain and then through August Town to the "Overflow Chamber" on the south-east comer of the Mona Reservoir. From the Overflow Chamber a further 2000 ft of raw water pipeline runs beneath the reservoir crest roadway to the Mona Water Treatment Plant (WTP).
As such raw water flows in the pipeline can either travel directly into the water treatment plant or, by throttling the inlet flow control valves at the plant, where raw water can be made to spill into the Mona Reservoir at the Overflow Chamber. While the Yallahs Pipeline is equipped with air and washout valves throughout its length (the former being essential for proper hydraulic operation and the latter being provided to enable any silt deposits within the line to be washed out), the in-line control valve at the Mona WTP is the only flow control valve on the entire 19 mile gravity pipeline. Within overall basic hydraulic parameters, the total Yallahs Pipeline was constructed on a Fast-Track basis i.e. designs were developed as work progressed from Riverhead towards Kingston - basic right-of-way earthwork designs being produced "just-in-time" for earthmoving activities (as surveys advanced along the route) while pipeline details were subsequently generated from as-built earthworks surveys 'just-in-time' for pipeline construction.
The Roaring River Treatment Plant was built in 1957. Located in the Roaring River district adjacent to Petersfield, Westmoreland, it is a gravity-fed, full treatment plant with a rapid sand filter and five chambers. It has a capacity of three (3) million gallons per day (mgd). The Roaring River Treatment Plant supplies the areas of:
Petersfield, Hartford, Campbelton Gardens, Shrewsbury, Carawina, Amity, George’s Plain, Frome, Farm Pen, Savanna-la-mar, Strathbogie, Bath, Torrington, Three Miles River, Llandilo Housing Scheme, Deans Valley Housing Scheme, Big Bridge and Little Bridge Districts.
Located in the Logwood District of Hanover, the Logwood Treatment Plant it is a full water treatment plant and is operated 24 hours daily. The treatment plant obtains water from two sources - the Blue Hole and Fish River Springs. Its capacity is 3.2 million gallons per day and its water supply is divided between Lucea and Negril. The Logwood Treatment Plant was built in 1957 and supplies the areas of:
West End, Red Ground, Beach Road, Bloody Bay, Green Island, Orange Bay, Santoy, March Town, Salt Spring, Pell River, Cove, Davis Cove, Industrial Cove, Esher, Haughton Court, Lucea, Malcolm Heights, Brissett, First Hill, Johnson Town, Elgin Town, Camel Hill and Logwood District.
Martha Brae No. 1
A rapid gravity filter plant with a treatment capacity of 1.5 million gallons per day. It has six (6) settling tanks and six (6) filters. It is located about two miles south of Falmouth at the bridge in Martha Brae and supplies the areas of:
Martha Brae, Hague, Falmouth, Coopers Pen, Carib Road, Salt Marsh and Wiltshire.
Martha Brae No. 2
Construction started in 1987 and was completed in 1988. It is located two miles south of Falmouth on the road to Good Hope District and has a rapid green leaf filtration system with two clarifiers and one filter of four chambers. Its treatment capacity is 6 million gallons of water per day and supplies the communities of:
Green Park, Granville, Shawfield, Davis Pen, and areas of St. James such as Greenwood, Liliput, Ironshore, Coral Gardens and Flankers.
Brampton, Jackson Town, Samuel, Prospect, Calabar, Rio Bueno.
Built in 1962, the White River Treatment Plant is situated in the western section of St. Mary near the border of St. Ann and St. Mary. It is a full-scale treatment plant with 24-hour operation. It has two settling tanks, three filter beds, a clear well and three re-lift pumps. A rapid gravity filter, it produces 1.1 million gallons of water per day. Areas supplied include:
Charleston, Three Hills, Spring Valley, Balmoral, Caribbean Park, Jamaica Beach, Pampano Bay, Cascade, Labrynth, Rose Street, St. Mary Country Club.
Commissioned in 1974, the Grants Level Treatment Plant is supplied with water from four wells. It is capable of producing 3.5 million gallons of water per day. Located in the Grants Level District, this treatment plant supplies the following areas:
Barrydale, Fellowship, Stanton, Rivers View, Sections of Windsor, Snow Hill, Wayne Road, Mt. Oakley, Red Hazel Road, Passley Gardens, San San, Titchfield, Naylors Hill, Boundbrook, Dolphin Bay, Port Antonio and the Anchovy Housing Scheme.
This facility consists of two wells:
Well No. 1 was built in 1969 and has a depth of 60 feet and an output of 1.2 million gallons per day. It is used as a standby supply.
Well No.2 was built in 1982 and is 65 feet deep with an output of 1.7 million gallons per day. Both wells pump water into a reservoir from which three lift pumps carry water into the distribution system. The Springfield Pumping Station supplies water to:
Morant Bay, Duhaney Pen, Church Corner, Lyssons, Summit Road, Retreat, Highbury, Crescent and Sections of York.
The Spanish Town Treatment Plant is a rapid gravity facility, which initially had a capacity of 2 million gallons per day (mgd) and was expanded to 4 mgd in the early 1990's. Raw water is obtained from the Rio Cobre River via the National Irrigation Commission's irrigation canal. Located at Jobs Lane in Spanish Town, the treatment plant provides the following areas with water:
Brunswick Avenue, Jobs Lane and environs, St. Johns Road and environs, Valdez Road and environs, Willowdene, Horizon Park, Sydenham, Villa Nueva, Hopedale, Cromarty and environs, Old Harbour Road to McCooks Pen, Homestead, Sunnyside, Hartlands, Westmore Gardens and Metropolitan Spanish Town.
Built in 1962, the Hayes Well has a designed output capacity of 2.0 million gallons per day. Located in the northern section of Hayes District, the pumping station serves the areas of:
Top Hill, Corn Piece, Raymonds, Savannah and White Road.
This system was built in 1986 and funded by a loan from the Inter-American Development Bank and the Government of Jamaica. It has an output capacity of 3.6 million gallons of water per day and supplies the following areas:
Mandeville, Gutters, Downs, Newport, Old England, Decarteret, Hillside and Dunsinane.
Commissioned in 1982, the Malvern/Munro Pumping Station is supplied with water from two wells at Parklee. One well has a capacity of 1 million gallons of water per day and the other 0.8 million gallons of water per day. The pumping station provides an adequate supply of potable water to the following districts:
Malvern, Munro, Hampton, Bethlehem, Torrington, St. Mary’s, Epping Forest, Corby, Top Hill, Belleview H/S, Yardley, Chase, Lovers Leap, Southfield, Seaview, Congo Hole, Mountainside, Knoxwood, Round Hill and Brownberry Lane.
Sewerage Treatment Plants
The NWC operates nearly 100 sewerage (wastewater) treatment plants islandwide. The types of sewerage treatment facilities used in Jamaica include oxidation ditch, activated sludge, waste stabilization pond and primary treatment. Central sewerage systems are located in Kingston and St. Andrew, South-east St. Catherine (Portmore), Montego Bay in St. James, Ocho Rios in St. Ann, and Negril in Westmoreland. In addition, the NWC has the responsibility for small sewerage systems, which are associated with housing developments in various parts of the country. A packaged sewerage treatment plant is a part of most of these small systems.
The table below provides information on some of the sewerage treatment facilities operated by the NWC.
The NWC has recently completed comprehensive sewerage systems for Ocho Rios (St. Ann) and Negril (Westmoreland) to meet the increasing need for sewerage services in these areas. Similarly, the Montego Bay system in St. James has been upgraded and expanded to meet the long-term requirements for sewerage in that city. |
