Capacity Assessment and Mapping of the Municipal
Sanitation Infrastructure in Tobago
Garrick E. Louis, Luna Magpili, Amanda Singleton
University of Virginia
Systems and Information Engineering
July 1, 2005
Abstract: This project was part of an investigation into processes for assuring access to
improved municipal sanitation services in developing communities. The principal
investigator for the project was Dr. Garrick Louis of the University of Virginia. Dr.
Louis was supported by a grant from the National Science Foundation (#9984318) and
assisted by research students Luna Magpili and Amanda Singleton.
The goal of the project was to assess and map the physical infrastructure of Tobago’s
municipal sanitation system, consisting of its drinking water supply, wastewater and
sewage treatment, and municipal solid waste management services. Construction and
demolition debris, and medical and infectious waste were not included in the
assessment. This report presents the results of the assessment of the existing and
projected capacity of drinking water supply (DWS), wastewater and sewage treatment
(WST), and solid waste management (MSW) services in Tobago as of August 31, 2002.
These three services are referred to collectively as municipal sanitation services, and
together they constitute the island’s municipal sanitation system (MSS). The assessment
recorded and mapped the geographical location of all known facilities in the system,
using a Geographical Information System (GIS). Other elements of the assessment
included; i) interviews with facility operators to determine the capacity and operating
status of facilities, ii) estimates of the ratio of supply to demand for service at the parish
level, and for Tobago as a whole, iii) Projecting the ratio of supply to demand for each
service in 5-year increments through 2025, assuming no expansion in capacity. The
report briefly summarizes the institutional context for municipal sanitation services in
Tobago, then proceeds to document an existing surplus in drinking water supply, with
critical shortages in wastewater and sewage treatment, and municipal solid waste
management capacity. The key recommendation of the report is urgent action to address
the shortage of wastewater and sewage treatment capacity in the parish of St. Patrick,
home to the bulk of the island’s growing tourism industry. The assessment was carried
out with the approval of Honourable Orville London, Chief Secretary of the Tobago
House of Assembly, and with the assistance of Mr. Brian Williams and Mr. Cassius
Mills of the Water and Sewage Authority in Tobago.
Garrick E. Louis, PhD., Charlottesville, Virginia, 25th July 2005.
1
1.0
INTRODUCTION
Tobago is situated just 32 kilometers (20 miles) off the northeast coast of Trinidad, and
is the smaller of the two-island nation of Trinidad and Tobago. With an area of 300
square kilometers (116 square miles), Tobago has a central hilly range and a flat area in
the south and west of the island. The island is divided into seven parishes; St. Andrew,
St. David, , St. George, St. John, St. Mary, St. Patrick, and St. Paul. . The Tobago
House of Assembly (THA) was re-established as the island’s local government in 1980.
Its principal administrative center is in the capital, Scarborough, in St. Andrew parish.
Historically the island’s primary source of revenue was agriculture, with is main cash
crops being sugarcane, cocoa, and coffee.1,2 Revenue received from agriculture has
declined, and tourism has become a principal engine for development in Tobago. Much
of the development related to tourism is concentrated in the flat southwest region of the
island, from Plymouth to Scarborough, as illustrated in Figure 1-1.
The tourism sector has grown at an increased rate since 1990 as a result of the policies
of the Central Government and that of the THA, which have promoted tourism as a
primary driver for economic development of the island. The sector grew from an
estimated capacity of 565 rooms employing 4,500 people in 1989, to over 2,200 rooms
employing 5,000 people in 2001. The increase in hotel capacity (including two 18-hole
golf courses) was not accompanied by a proportional increases in the required
infrastructure services, especially water supply, wastewater and sewage management,
and solid waste management. Furthermore, the island hosts a significant number of
yachts and cruise ships each year, which add to the demand for water and sanitation
services, particularly in the ecologically-sensitive coastal zone.
2
Figure 1-1: Tourism Map of Tobago
Source: http://www.optinam2005.com/images/accommodation/tobagomap_lg.jpg
3
2.0
CONTEXT
The institutional actors that govern municipal sanitation services in Tobago lie in the
Central Government in Trinidad, the Tobago House of Assembly, the Health Department,
and the Tobago divisions of organizations responsible for operation of the system;
namely the Water and Sewage Authority (WASA), and the Solid Waste Management
Company Limited (SWMCOL).
2.1
Central Government Ministries
The portfolio of the Ministry of Public Utilities and the Environment includes
responsibilities for environmental management, pollution control, solid waste and
hazardous substances management, water resources, and enterprises; including the Water
and Sewage Authority, and the Trinidad and Tobago Solid Waste Management Company
Limited. The Ministry of Tourism has general responsibility for the tourism industry and
hotel development. Thus this Ministry directly influences the rate and size of growth of
the tourist sector in Tobago, and subsequently determines the demand that this sector
places on municipal sanitation services on the island.
2.2
Tobago House of Assembly (THA)
The Tobago House of Assembly is the local government body responsible for the
operation of government in Tobago. The THA couples its local government role with
many of the responsibilities of the Central government in Tobago, with the exception of
national security, foreign affairs, taxation, legislation, and zoning. The THA was
constituted in 1980 to address the public service needs of the residents of Tobago. Its
Constitution, and responsibilities were most recently defined in the Tobago House of
Assembly Act of 1996. The THA consists of 16 members, 12 of whom are elected, and
four of whom are appointed as councilors. Under the THA Act of 1996, the assembly has
33 area of responsibility of which the following are most relevant to municipal sanitation
services; the environment, infrastructure (including public utilities), land and marine
parks, and tourism.
2.3
The Water and Sewage Authority (WASA)
The Water and Sewage Authority is an enterprise within the Ministry of Public Utilities
and the Environment. The Authority was established in 1965 and is now the largest
public utility in the country, serving over ninety percent (90%) of the population with
pipe borne water through private house connections and standpipes. WASA reports its
water production was 650,000 cubic meters (172 million gallons) in 1990. WASA is also
responsible for wastewater service in Trinidad and Tobago, serving 30% - 40% of the
population with a central sewerage collection and treatment system. Another 40% of the
population is served by cesspool-tank soil-absorption field systems, with the remainder of
the population served by pit latrines.3
4
WASA operates three major dams and reservoirs in Trinidad (Arena Dam, Hollis
Reservoir, and Navet Dam) and one in Tobago (Hillsborough Reservoir). The
Hillsborough Reservoir was completed in 1952, and has an output of roughly 9100 cubic
meters per day (2.4 million gallons per day – mgd).
2.4
Solid Waste Management Company Limited (SWMCOL)
The Solid Waste Management Company Limited is a wholly-owned state enterprise,
established in 1980, with specific responsibility for solid waste management in Trinidad
and Tobago. This was to be effected either by direct supervision or through the provision
of technical and managerial assistance to local authorities and institutions.
[http://www.swmcol.co.tt/]
SWMCOL’s main services are:
ƒ
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ƒ
ƒ
ƒ
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General and liquid waste collection and disposal
Waste reduction, reuse and recycling programs
Environmental audits/assessments
Consultancy services in environmental engineering and management
Design, development, operation, and closure of landfill sites
Environmental public education and awareness programs
SWMCOL manages and operates the three landfill sites in Trinidad, (Beetham, Guanapo,
and Forres Park). The company also designed and constructed services for faecal waste
disposal facilities and currently provides consulting and advisory services to the local
authorities that control these facilities, including those in Tobago.
2.5
Health Authority
There are four regional health authorities in Trinidad and Tobago; North-West, SouthWest, Eastern, and Tobago. Regional Health Authorities are autonomous statutory
bodies that function as the providers of healthcare services to all residents in their
respective regions. The Tobago Health Authority inspects the Studley Park Landfill and
combats illegal dumping on the island. Its work in this area aims to reduce adverse
health impacts, such as dengue fever, arising from waste management issues. The THA
is responsible for waste collection and management of the Studley Park Landfill, which is
the only official landfill in Tobago.
2.6
Hotels/Tourism
According to Prime Minister Patrick Manning, Trinidad and Tobago’s tourism is most
prevalent on Tobago. In 2003, he cited 57,000 tourists having visited Tobago in 2002
with an expected increase the following year. Efforts to expand the industry have been
fueled by establishing a Standing Committee of the Cabinet, chaired by the Prime
Minister himself, to oversee tourism. “We [Trinidad and Tobago] are spending $305
5
million (US $51 million) over the next three years on tourism development,” he said.
The Prime Minister’s comments can be found in an interview, transcribed on
http://www.internationalreports.net/theamericas/trinidad/2003/primeminister.html
Specific, measurable steps to aid tourism were included in the 2003 Budget (see 1.3,
Budget website). Some of these include:
ƒ
ƒ
ƒ
Expansion of the Crown Point airport terminal building
Revised policy guidelines for Integrated Resort Development, defined to
cover projects with a minimum capital investment of $350 million,
including a hotel of at least 200 rooms as well as amenities such as golf
courses, marinas, etc.
Proposal of a capital allowance of 100% of the cost of building materials
with respect to approved capital expenditure incurred by the owner or
operator in converting existing houses into guest homes. This is to
stimulate new entrepreneurs in the tourism industry, especially in Tobago.
Estimates suggest that the doubling of tourist activity during the decade of the 1990’s
also doubled the demand for water and power and the supply of solid waste. (SEDU,
2003)4
6
3.0
ASSESSMENT OF FACILITIES
3.1
Overview
Municipal sanitation infrastructure is distributed in all parishes across the island, with
water supply facilities in each parish. The majority of wastewater units are modular
(package) sewage treatment systems, used by hotels in the Southwestern parish of St.
Patrick. The Studley Park landfill is located in the parish of St. Mary. Figure 3-1 displays
the location of each type of facility relative to the population of its host parish.
7
Figure 3-1: Distribution of MSS facilities by Parish in Tobago
Tobago Sanitation Infrastructure:
Island Population Density and
Sanitation Infrastructure Sitings
²
St. John
St. Paul
St. David
St. Mary
St. George
St. Andrew
Legend
St. Patrick
!
.
Wastewater System
Water System
#
Solid Waste System
POP_2000
2965
2966 - 3500
3501 - 5500
5501 - 8000
8001 - 16000
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
8
3.2
Drinking Water Supply (DWS)
Tobago’s DWS is obtained from the Hillsboro reservoir, eleven wells, and several rivers
that are direct sources to water treatment plants. The island’s six water treatment plants
have a combined capacity ranging between 29,000-30,000 cubic meters per day (7.667.93 mgd) with an average flow through these six plants of 26,000 m3/day (6.87 mgd).
Three of the eleven wells have known capacities of 2650 m3/day (0.7 mgd). These wells
supplement the water coming from the Hillsboro reservoir and the river sources that enter
the six water treatment plants. There is an operating supply of eight million gallons per
day (mgd) (Value obtained from Brian Williams, WASA Tobago), approximately 30,000
m3/day (7.93 mgd). This yields a 10.9 million m3/yr (2,879 mgy) supply, roughly 73% of
the total inventory of 15 million m3/yr (3,963 mgy) capacity. The distribution of this
supply by parish is summarized in Table 3.1, and illustrated in Figure 3.2.
Table 3.1: Summary of Producing Facilities the Tobago DWS System.
Parish
Source
Source Capacity [m3/yr]
St. Andrew
WELL4&5GF
730,000
St. Andrew
WELL6GF
730,000
St. Andrew
WTP6
2,555,000
4,015,000
St. David
WTP3
2,762,554
St. David
.5*WTP4
310,250
3,072,804
St. George
.5*WTP4
310,250
310,250
St. John
WTP5
690,638
690,638
St. Mary
.5*WTP2
821,250
821,250
St. Patrick
WELL1C
967,250
St. Patrick
WELL2DE
967,250
St. Patrick
WELL3DE
967,250
St. Patrick
WTP1
2,417,234
5,318,984
St. Paul
.5*WTP2
821,250
821,250
Total Supply
15,050,177
9
Figure 3.2: Distribution of Drinking Water Supply Facilities by Parish.
Tobago Sanitation Infrastructure:
DSW Supply by Parish [cubic meters/year]
²
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Facility Type
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Booster or Lift Station
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Storage Tank
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Production Well
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Water Treatment Plant
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Resevoir
MSSInfo
DWS Supply by Parish [cubic met
821250.000
821250.001 - 2244750.00
2244750.01 - 3592388.00
3592388.01 - 5456750.00
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
The geographical coordinates and description of all drinking water supply (DWS)
facilities are provided in Table A1 at the end of this report.
10
3.3
Wastewater and Sewage Treatment (WST)
The sewage treatment system in Tobago is comprised of WASA and other publiclyowned treatment plants in conjunction with private package units. There are five major
sewage treatment plants operated by WASA, the National Health Authority, and the
airport. The other sewage package units exist in the island’s hotels, primarily on the
southwest end of the island (see Table 3.2). Information regarding the location and
management of WST facilities on the island is provided in Table 3.2 and Figure 3.3.
Table 3.2: Wastewater and Sewage Treatment Facilities by Parish
Plant CODE
Parish
PU1*
St. Andrew
PU2
St. Patrick
PU3
St. Patrick
PU4
St. Patrick
PU5
St. Patrick
PU6
St. Patrick
PU7
St. Patrick
PU8
St. Patrick
PU9
St. Patrick
STP1
St. Andrew
STP2
St. Patrick
STP3
St. Patrick
STP4
St. Patrick
STP5
St. Patrick
*PU = package unit
**NHA = National Housing Authority
Ownership
Private
Private
Private
Private
Private
Private
Private
Private
Private
WASA
NHA**
WASA
NHA
NHA
The WASA-operated Smithfield sewage treatment plant (STP) was in good working
order when visited, but the facility was operating at close to its minimum capacity at 950
m3 (250,000 gpd) out of the 8,520 m3 (2,250,000 gpd) rated capacity. Smithfield caters
mainly to the Scarborough area. Connections between this system and Scarborough area
industries are being phased in to promote operation closer to maximum capacity. As of
August 2002 there were only 71 billed sewer connection accounts that fed into the
Smithfield STP.
The Airport sewage treatment plant was the smallest full service treatment plants on the
island. The assessment found algae growth within the aerator but correct management of
sludge in drying beds.
The Bon Accord Integrated Community sewage treatment plant was geo-coded but not
interviewed.
Two other residential community sewage treatment plants, both of which operated by the
National Housing Authority of Tobago, were examined. The first, Milford Court sewage
treatment plant, has two clarifier aerators with sludge removal once per year to Studley
Park Landfill. On the visit in August 2002, the clarifier was completely clogged,
11
resulting in buoyant sludge at the top of both clarifiers. Due to this back up, the system
operates at half of its 60,000 gallon-per-day capacity. The Milford Court sewage
treatment plant serves over 2000 residents. Effluent from the waste reactor is discharged
into a water hyacinth pond for polishing before passing into an adjoining canal. The
discharge point from this canal was not located.
The second NHA operation was the Coral Gardens/Buccoo area sewage treatment plant.
This facility has the same basic operation as Milford Court. Algae growth was found at
the drainage point from this system leading into the canals that drain into Buccoo Bay.
Both of these are located in the Parish of St. Patrick and their maximum combined
capacity is roughly 707m3/day (187,000 gpd).
The other significant portion of Tobago’s wastewater and sewage treatment system
consists of private hotel sewage package units. Nine hotels operating on such units were
visited. Hotels on septic systems were excluded from interviews. The hotel package
units, mainly located in the Parish of St. Patrick, are responsible for 18.2m3/day (4,800
gpd). There are roughly 970 rooms in the hotels with package units. At a standard
consumption rate of 0.38m3/day per room (100 gpd per room), the total sewage treatment
capacity required to serve these hotels would be 367m3/day (97,000 gpd). Thus the
processing capacity of existing package units is only 5% of the required capacity for
hotels. This implies that even if the units were all operating properly and at full capacity,
they would be unable to provide adequate treatment capacity for the wastewater
generated by their establishments. Since all of these hotels are located within yards of
popular beaches, and the majority discharge their effluent into the bays that are bordered
by these beaches, this deficiency in treatment capacity should be of the highest priority
for mitigation if risks to public health and the neighboring coastal ecosystems are to be
avoided.
A significant mitigating factor in this assessment is the likelihood that the package units
receive only black water flow, which is the flow from flush toilets. This assumes that all
other wastewater from showers, sinks, and laundries, collectively referred to as grey
water, is discharged without treatment to land or surface waters. With flush toilets
accounting for 33% of wastewater flow (Qasim, 1999)5, this would mean that the
required treatment capacity for hotels with package units is 121m3/day (32,000 gpd). Of
course, the existing capacity of 4,800 gallons per day is still only 12.5% of this
requirement so the urgency of added capacity is hardly diminished.
The need for additional capacity is made even more urgent by the fact that the assessment
found only one of the nine package units inspected being operated as required and
functioning properly. The other units had aerators operating but no anaerobic digestion or
settling. In some cases chorine disinfection was applied before discharge of the effluent.
However these units were not operating in a manner consistent with reduction of the
biochemical oxygen demand of their wastewater. Thus it must be assumed that these
units were discharging nutrient-laden effluent into the receiving streams, and coastal
waters. Dilution and mixing from wave turbulence may provide some natural attenuation
of the risk from this nutrient loading. However, there is a risk that discharge of effluent
12
that is rich in nitrate (and possible phosphates) could lead to anoxic conditions in the
vicinity of the discharge point, with adverse ecological impacts, including fish kills and
death of other marine life, as well as algae blooms. Testing of the effluent from hotel
package units would be necessary to determine its biochemical composition.
Figure 3.3: Distribution of Wastewater and Sewage Treatment Facilities by Parish
Tobago Sanitation Infrastructure:
WST Supply by Parish [cubic meters/year]
²
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Legend
MSSInfo
WST Supply by Parish [cubic meters/year]
0.000000000
0.000000000 - 1000000.00
1000000.01 - 5000000.00
.
!
Sewage Treatmant Facilities
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
13
The geographical coordinates and description of all wastewater and sewage treatment
(WST) facilities are provided in Table A2 at the end of this report.
3.4
Municipal Solid Waste Management (MSW)
In 1983, the Studley Park landfill was constructed under the authority of the SWMCOL
(established in 1980) as part of a master plan for Solid Waste Management in Trinidad
and Tobago (1977). Studley Park, with an area of six acres, continues operation at
present, although a study done in 1989 recommended that the site should be closed and a
new landfill established.6,7 This conclusion was due to problems such as limited capacity
and the potential for groundwater pollution. Approximate throughput is 14.5 metric tons
per day (the capacity of 14 truck-trips per day).
There were three unofficial dumpsites documented in this assessment. They were located
in St. Patrick parish, at Kilgwyn Wetlands, bordering Golden Grove Road, and along
Orange Hill Trace approximately 2 kilometers southwest of the Bucco Road/Mt. Pleasant
Road intersection. These facilities appeared to be inactive, though they contained
significant amounts of discarded bulk goods, such as refrigerators, stoves and bed frames.
14
4.0
DEMAND AND CURRENT DEFICIT
In this section the demand for each municipal sanitation service is estimated and
compared to the documented supply in each parish and for the island as a whole. Neither
drinking water supply (DWS), wastewater and sewage treatment (WST) nor municipal
solid waste management (MSW) is administered at the parish level in Tobago. However,
the parish serve as a convenient accounting unit for analyzing the level at which small
aggregates of villages have local access to municipal sanitation services. A list of the
parishes and their constituent villages in presented in Table A4.
4.1
Drinking Water Supply (DWS)
There are several sources that can be used to estimate the demand for water in Tobago. In
1991, WASA estimated that the water demand for Tobago was 26,000 m3/day (6.87 mgd)
and the supply was 22,000 m3/day (5.81 mgd). This meant a deficit of 15%.8 The
Authority also projected that water demand by 2000 would be 39,000 m3/day (10.3 mgd),
equivalent to 14.2 million m3/yr (3,751 mgy). The United Nations Food and Agricultural
Organization (UNFAO) estimated total water withdrawals for Trinidad and Tobago to be
305 million cubic meters per year (80,572 mgy) in the year 2000.9 Based on its 4.5% of
the total population in the 2000 census, Tobago accounted for 13.1 million m3/year
(3,461 mgy) of the nation’s water withdrawals, a figure that slightly less than WASA’s
projection for the year. This may be taken as the low estimate of the island’s annual water
supply. Using data from the World Resources Institute and the World Bank,
Shiklomanov’s10 hydrodynamic model estimates total water consumption in Trinidad and
Tobago to be 330 million m3/year (87,177 mgy), which is 7.5% higher than the UNFAO
estimate. Based on Shiklomanov’s estimate, Tobago’s share of these water withdrawals
in 2000 would have been 14.1 million m3/yr (3,725 mgy), a figure that is very close to
WASA’s projection for the year. This may be taken as the median estimate of Tobago’s
annual water supply. If demand from the tourism sector is assumed to contribute the
equivalent of 25% of Tobago’s estimated demand, then the island’s share of water
withdrawals in 2000 would have been 17.8 million m3/yr (4,702 mgy), based on
Shiklomanov’s estimate. This may be taken as the high estimate of the island’s annual
water supply. The low, medium, and high estimated demand for potable water, along
with the assessed supply by parish for the 2000 base year, are illustrated in Figure 4.1.
15
Figure 4.1: Low, Medium and High Estimated Water Demand vs. Supply for Tobago: 2000
Water Supply vs. Estimated Demand
6,000,000
5,000,000
Cu M/Yr
4,000,000
Low Demand
Med. Demand
3,000,000
High Demand
2,000,000
Supply
1,000,000
l
au
in
tP
Sa
ri c
k
in
tP
at
ar
y
Sa
in
tM
Sa
in
tJ
Sa
eo
in
tG
oh
n
rg
e
id
av
in
tD
Sa
Sa
Sa
in
tA
nd
re
w
-
Parish
SOURCES United Nations "Urban and Rural Areas 1950-2025, the 1995 Revision" (World Resources Institute data) **
- 1961-1993 Source: FAO FAOSTAT 95 (World Resources Institute data); 1995 – 2025 - SHI forecast . Source: World
Bank World Tables 1994 update (World Resources Institute data)].
Population data from the 2000 Census Report by the Central Statistical Office, Government of Trinidad & Tobago.
http://earthtrends.wri.org/pdf_library/country_profiles/wat_cou_780.pdf
Table 4.1 calculates the ratio of the existing supply of water partitioned by parish to the
maximum estimated demand for each parish in Tobago.
Table 4.1: Summary of Drinking Water Supply and Demand by Parish in Tobago. August 2002
Parish
Supply (m3/y)
Demand (m3/y)
Ratio (S/D)
St. Andrew
4,015,000
5,223,900
0.77
St. David
3,072,803
2,476,320
1.24
St. George
310,250
1,770,120
0.18
St. John
690,638
989,340
0.7
St. Mary
821,250
978,450
0.84
St. Patrick*
5,318,984
4,648,593
1.14
St. Paul
821,250
1,785,960
0.46
Tobago (total)
15,050,175
17,872,683
0.84
* St. Patrick demand includes hotel demand = 26,469 m3/yr
The estimate for St. Patrick includes a demand of 26, 469m3/year (6.99 mgy) from hotels
in the parish. In fact, in the year 2000, the number of rooms was closer to 2200 (SEDU
2003), with an estimated demand of 0.38m3/room day (100Gall/Day) (based on Qasim
1999 estimate for wastewater demand). Thus the demand for St Patrick parish is
16
4,928,770m3/year (1,302 mgy), and Tobago, 18,152,859 m3/year (4,795 mgy), roughly
280,000m3/year (74 mgy) more than originally estimated. This means that the ratio of
supply to demand in St. Patrick is actually 1.08 and the ratio for Tobago is 0.83.
Since water supply in Tobago is not distributed by parish, the ratio of service capacity by
parish provides little useful operative information. However, as planners weigh the
expansion of the water supply system, it would be useful to know the expected demand
from each parish, and design a supply system that is capable of satisfying the demand in
each parish at its point of use. In this planning context, use of the ratio of supply to
demand for each parish becomes informative. Figure 4.2 displays the demand for water
by parish in Tobago as of August 2002.
17
Figure 4.2: Demand for Water by Parish in Tobago (August 002)
Tobago Sanitation Infrastructure:
DWS Demand by Parish [cubic meters/ year]
²
Legend
MSSInfo
DWS_demand cub/m/year
978450.000
978450.001 - 1000000.00
1000000.01 - 2000000.00
2000000.01 - 2500000.00
2500000.01 - 5500000.00
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
18
4.2
Wastewater and Sewage Treatment (WST)
Tobago faces a growing problem of sewage pollution. Sewage systems serve roughly
30% of the total population, mostly in urban areas, while the rest of the urban population
and most of the rural population use septic tanks or pit latrines.11 The 1995 State of the
Environment Report, published by the Environmental Management Authority, identified
sixteen sewage treatment plants in Tobago. Of these, only three were classified as
functioning adequately. Average wastewater flow may vary from 60 to 130 percent of
water consumption in a community (Qasim, 1999).12 Wastewater in Tobago may be
classified into black water from flush toilets, and grey water from showers, sinks,
laundries and all other uses. With the exception of a limited number of connections to the
Smithfield Sewage Treatment Plant in St. Andrew, the package units at hotels, and the
modular sewage treatment plants in St. Patrick, the bulk of black water flows to cesspools
and septic tanks with drainfields. The bulk of grey water is flows untreated overland into
irrigation plots, surface waters, or migrates into the vadose zone as groundwater. Because
of this arrangement, the standard estimates of wastewater flow will not accurately
characterize the current demand for centralized wastewater and sewage service in
Tobago. Thus, the estimates in this report make projections of the expected demand if
90% of all wastewater flows in Tobago were required to receive up to secondary
treatment in a wastewater treatment facility prior to discharge into the environment. The
ratio of supply to demand by parish in Tobago under this assumption is presented in
Table 4.2.
Table 4.2: Summary of Wastewater Supply and Demand by Parish in Tobago. August 2002
Demand (m3/yr)
Ratio (S/D)
Parish
Supply (m3/yr)
St. Andrew
3,108,808
4,701,510
0.66
St. David
0
2,228,688
0
St. George
0
1,593,108
0
St. John
0
890,406
0
St. Mary
0
880,605
0
St. Patrick*
133,684
4,161,267
0.03
St. Paul
0
1,607,364
0
Tobago
3,242,492
16,062,948
0.2
* St. Patrick’s demand includes hotel demand = 26,500 m3/yr (7 mgy)
** St. Patrick’s supply includes 25% of hotel demand and 25% of residential demand for the communities of Milford
Court and Coral Gardens/Buccoo.
Data are for the year 2000
As noted in Section 3.2 of this report, there is an urgent need to address the shortage of
wastewater and sewage treatment capacity in St. Parish parish because of the high
demand from hotels, the density of housing in the Canaan, Bon Accord area, and the risk
to human health and the environment from inadequately treated wastewater discharges in
the parish. Upgrading the performance of hotel package sewage treatment units alone will
do little to mitigate this risk, as this action will add no more than 13% to the total
wastewater treatment capacity needed. Figure 4.3 displays the demand for wastewater
treatment service by parish in Tobago as of August 2002.
19
Figure 4.3: Demand for Wastewater Treatment by Parish in Tobago (August 002)
Tobago Sanitation Infrastructure:
WST Demand by Parish [cubic meters/ year]
²
St. John
St. Paul
St. David
St. Mary
St. George
St. Andrew
St. Patrick
Legend
MSSInfo
WST Demand by Parish [cubic meters/year]
880605.000
880605.001 - 1000000.00
1000000.01 - 2000000.00
2000000.01 - 3000000.00
3000000.01 - 5000000.00
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
4.3
Municipal Solid Waste Management (MSW)
One of the most serious environmental concerns in Tobago is that of inadequate solid
waste management. Littering was observed from Charlotteville to Crown Point and from
the Main Ridge to the beaches, indicating deficits in the collection of solid waste at the
point of generation, and inadequate frequency and/or coverage of waste removal from
20
collection points to the landfill. A lack of rubbish receptacles on beaches was observed in
this assessment. Transfer stations are not employed, thus collection vehicles must make
the round trip from the last location on which their vehicle became filled to the landfill.
This is time-consuming and uneconomical, and could contribute to incomplete collection
on routes that are distant from the Studley Park landfill. The actual number, type,
ownership, and condition of collection vehicles deployed in Tobago could not be
ascertained for this assessment report. It remains an item of continuing work. Thus, the
capacity of the collection system could not be evaluated relative to the quantity of waste
generated. Using an estimated generation rate of 0.45kg/person/day (~1 pound/day)
(UNEP 2000)13, Table 4.3 summarizes the MSW generation by parish for Tobago. As
explained earlier, MSW collection capacity could not be ascertained, thus the column
remains blank in Table 4.3. The distribution of this demand for solid waste collection
service by Parish is illustrated in Figure 4.4.
Table 4.3: Summary of Solid Waste Generation (Demand) by Parish in Tobago. August 2002
Parish
St. Andrew
St. David
St. George
St. John
St. Mary
St. Patrick
St. Paul
Tobago
Population (2000)
15,830
7,504
5,364
2,998
2,965
14,011
5,412
54,084
MSW
(tons per year)
2,849
1,351
966
540
534
2,522
974
9,735
MSW Collection
The composition of the solid waste stream in Tobago is reported to be changing from
predominantly wet bio-degradable organic matter to higher percentages of plastics,
metals, glass, and paper. (UNEP 2000). However, there were no materials recycling
facilities (MRF) or programs evident during this assessment. There may be opportunities
to compost the vegetative portion of the waste for local use as a soil conditioner. A
detailed characterization of the waste from markets and fruit stands could determine the
feasibility and type of composting program that would be appropriate. Recycling of
plastics, aluminum, glass, and paper, would be subject to the economics of collecting
these materials in sufficient quality and quantity for profitable sale. This assumes that
there is an infrastructure in place in either Tobago or Trinidad to utilize recycled
materials. Such an infrastructure was not included in this assessment.
21
Figure 4.4: Demand for Wastewater Treatment by Parish in Tobago (August 002)
Tobago Sanitation Infrastructure:
MSW Demand by Parish [metric tons/year]
²
St. John
St. Paul
St. David
St. Mary
St. George
St. Andrew
St. Patrick
Legend
MSSInfo
MSW_demand by Parish [metric tons/year]
534.000000
534.000001 - 550.000000
550.000001 - 975.000000
975.000001 - 1500.00000
1500.00001 - 3000.00000
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
22
4.4
Summary of Tobago’s Municipal Sanitation System
Table 4.4 summarizes the estimated demand and assessed supply of each municipal
sanitation service by parish in Tobago as of August 2002. Data on solid waste collections
were not available.
Table 4.4: Summary of Municipal Sanitation Service Supply & Demand by Parish in Tobago. Aug 0
Demand
Supply
Population
DWS
WST
MSW
DWS
WWS
MSW
3
3
Parish
Year 2000
ton/yr
m /yr
m /yr
ton/yr
St. Andrew
15,830
5,223,900
4,701,510
2,849
5,456,750 3,108,808
St. David
7,504
2,476,320
2,228,688
1,351
3,072,804
0
St. George
5,364
1,770,120
1,593,108
966
2,244,750
0
St. John
2,998
989,340
890,406
540
3,592,388
0
St. Mary
2,965
978,450
880,605
534
821,250
0
St. Patrick
14,011
4,648,593
4,183,734
2,522
5,318,984
133,684
St. Paul
5,412
1,785,960
1,607,364
974
821,250
0
Tobago
54,084 17,872,683 16,085,415
9,736 21,328,176 3,242,492
5,220
Access (S/D)
1.2
0.2
0.54
23
5.0 SUMMARY OF SURPLUS IN EACH SERVICE
For planning purposes it is useful to know the ratio of supply to demand, and the gap
between supply and demand for each municipal sanitation service. The surplus in each
service was calculated as the difference between the minimum measured supply and the
maximum estimated demand. The surplus was also calculated as a ratio of the minimum
measured supply to the maximum estimated demand. Thus a negative surplus, or a ratio
less than 1.0, indicates a deficit of supply to demand. This measurement is conservative
in its attempt to estimate the maximum estimated need for each service under conditions
in August 2002.
Table 5.1 summarizes the surplus for drinking water supply by parish.
Table 5.1: Water Supply Surplus by Parish as of August 2002
Demand (m3/yr).
Parish
Supply(m3/yr).
St. Andrew
5,456,750
5,223,900
St. David
3,072,804
2,476,320
St. George
2,244,750
1,770,120
St. John
3,592,388
989,340
St. Mary
821,250
978,450
St. Patrick
5,318,984
4,648,593
St. Paul
821,250
1,785,960
Tobago
21,328,176
17,872,683
Ratio (S/D)
1.04
1.24
1.27
3.63
0.84
1.14
0.46
1.19
Surplus (S-D)
232,850
596,484
474,630
2,603,048
-157,200
670,391
-964,710
3,455,493
The current water supply from reservoirs, wells, and storage tanks exceeded demand in 5
of the 7 parishes and for Tobago as a whole in August 2002. Deficits existed in parishes
of St. Mary (157,200 m3/yr) (41.5 mgy) and St. Paul (964,710 m3/yr) (255 mgy). The
aggregate assessed supply of 21.3 million m3/yr (5,627 mgy), exceeded demand by 3.5
million m3/yr (925 mgy), or by 19%. The distribution of the surplus of water supply by
parish is presented in Figure 5.1.
24
Figure 5.1: Surplus of Water Supply by Parish in Tobago. August 2002
Tobago Sanitation Infrastructure:
DWS Deficit by Parish [cubic meters/year]
²
Legend
Deficit in DWS
(-) values for deficit indicate a surplus
-3000000
-3000000- -500000
-499999.999 - 0
0 - 500000
500000 - 1000000
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
25
Table 5.2 summarizes the wastewater treatment surplus by parish for August 2002. All
parishes show deficits for wastewater treatment, even St. Andrew and St. Patrick, the
only two parishes with installed wastewater treatment capacity.
Table 5.2: Wastewater Treatment Surplus by Parish as of August 2002*
Parish
Supply (m3/yr)
Demand (m3/yr)
Ratio (S/D) Deficit (S-D) (m3/yr)
St. Andrew
3,108,808
4,701,510
0.66
-1,592,702
St. David
0
2,228,688
0
-2,228,688
St. George
0
1,593,108
0
-1,593,108
St. John
0
890,406
0
-890,406
St. Mary
0
880,605
0
-880,605
St. Patrick
133,684
4,161,267
0.03
-4,027,583
St. Paul
0
1,607,364
0
-1,607,364
Tobago
3,242,492
16,062,948
0.2
-12,820,456
*Deficit calculated for wastewater treatment capacity only. Estimate does not include existing service
provided by septic tanks and pit latrines.
The deficits calculated for wastewater and sewage service do not account for the existing
capacity of septic tank, cesspool systems, and pit latrines. The majority of households and
guest houses in Tobago, as well as four of its oldest hotels, use septic systems for their
sewage disposal. A small but significant number of units use pit latrines. Thus, the
estimate of a deficit in WST service that is based primarily on the supply of public
wastewater treatment service yields an overestimate of this deficit relative to the
dominant practice on the island.
If the size and density of housing units increases over time, the continued use of
cesspools and septic drainage fields could lead to saturation of the vadose zone in
surrounding soils, with the risk of flooding from sewage waters and possible
contamination of the underlying water table. The imminence of this situation is not
known, though there are anecdotal reports of flooding of raw sewage from septic tanks in
the Village of Charlottesville after heavy rainfall. The assessment was unable to verify
these reports. Testing the degree of saturation of the vadose zone and chemistry of
subsurface water in soils around the more densely populated areas, could provide
evidence of the viability of current sewage management practices in Tobago. In parishes
where the use of individual household septic systems is no longer viable, estimates of the
deficit in service, based on the supply of public wastewater treatment service would be
appropriate. In that case the values in the table above would be relevant. As this estimate
illustrates, every parish in Tobago is deficient in wastewater treatment capacity, including
St. Andrew, which hosts the under-utilized Smithfield wastewater treatment plant. In
aggregate, current wastewater treatment capacity in Tobago is only 20% of demand.
Even with a heavy reliance on domestic septic systems and runoff of grey water, this low
percent capacity should be cause for concern to planners in Tobago. As demand grows
with population and economic development, the deficit in public wastewater treatment
capacity will worsen if new supplies are not added. The deficit in wastewater treatment
service by parish is displayed in Figure 5.2.
26
Figure 5.2: Deficit in Wastewater Supply by Parish in Tobago. August 2002
Tobago Sanitation Infrastructure:
WST Deficit by Parish [cubic meters/year]
²
Legend
Deficit in WST
[cubic meters/year]
880605
880605 - 1000000
1000000 - 2000000
2000000 - 3000000
3000000 - 4027583
Map Created By: Amanda Singleton for CIMSS research
University of Virginia Department of Systems and Information Engineering
Data from: CIMSS GPS field study, Trinidad and Tobago WASA,
Trinidad and Tobago Central Statistical Office
Created: 4/2003
As noted earlier, Studley Park is the island’s sole official landfill. It is located in St.
Mary’s parish, and provides disposal capacity for the entire island. Since it is unlikely
that disposal capacity could be sited by parish, a table of such capacity is not presented
for municipal solid waste, as it was for water supply, and wastewater and sewage
27
treatment. However, in this regard, it is noteworthy that no materials recovery facilities
(MRF) or composting facilities (CF) were identified in any of the parishes. These are
activities that could be organized on the parish or even village level. Depending on the
composition of the waste, these activities could reduce the total MSW burden for disposal
in the landfill, and provide a marketable product in the form of clean recyclables, and
compost for agricultural use. Characterization of the MSW generated by village or parish
would be necessary to assess the feasibility of materials recovery activities.
28
6.0
PROJECTED DEFICITS
6.1
Methodology
As an aid to planning for Tobago’s municipal sanitation needs, projections of the surplus
or deficit in each service were made in 5-year increments from the year 2000 to the year
2005. The supply of each service was assumed to remain fixed over the interval, with
investments made only to maintain current supply without expansion. The demand for
service was projected by a simple linear growth in per capita demand model, based on
year 20000 population data from the Central Statistical Office (CSO) of Trinidad14 and
Tourism data from the 2003 SEDU report. This model used a demand growth rate of
1.1%, calculated directly from the change in population from 1990 to 2000. The
residential data concerning the 2000 population can be found at
www.geohive.com/cd/link/phg?xml=tt&xsl=xs2. A linear growth rate produces a low
estimate of the demand for services over time. In fact, it is customary to use
compounding when forecasting the future demand for service based on a known
population growth rate when the per capita consumption is fixed over the forecast period.
This produces a nonlinear projected growth in demand, with estimates that are
significantly higher than those derived from a linear growth model. Since the choice of
the population growth rate from 2000 to 2025 is uncertain, and the initial estimated
demand was the high end estimate for the year 2000, the investigators used the linear
growth estimate to dampen the effect of the deficit estimates likely to be produced by a
nonlinear growth model. Thus, the reader is cautioned that the deficit values obtained
from the model employed in these projections are optimistic. In fact, with a more
common compounding model for future demand, the deficits in supply are likely to occur
earlier in the planning period, and be larger at the end of the 25-year horizon.
6.2
Drinking Water Supply (DWS)
The projected demand for water supply by parish over the 25-year planning horizon from
the year 2000 to the year 2025 is presented in Table 6.1.
Table 6.1: Total Forecasted DWS demand (Residential and Tourist, m3/yr)
Parish
2000
2005
2010
2015
2020
St. Andrew
5,223,900
5,511,215
5,798,529
6,085,844
6,373,158
St. David
2,476,320
2,612,518
2,748,715
2,884,913
3,021,110
St. George
1,770,120
1,867,477
1,964,833
2,062,190
2,159,546
St. John
989,340
1,043,754
1,098,167
1,152,581
1,206,995
St. Mary
978,450
1,032,265
1,086,080
1,139,894
1,193,709
St. Patrick*
4,928,770
5,199,852
5,470,935
5,742,017
6,013,099
St. Paul
1,785,960
1,884,188
1,982,416
2,080,643
2,178,871
Tobago*
18,152,860
19,151,267
20,149,675
21,148,082
22,146,489
*Values amended from Tables 4.1, 4.4, and 5.1 to reflect true estimated hotel demand.
2025
6,660,473
3,157,308
2,256,903
1,261,409
1,247,524
6,284,182
2,277,099
23,144,897
29
Assuming that demand remains constant at year 2000 levels (actually set at the levels
measured in August 2002), the ratio of supply to demand over the planning horizon is
summarized in Table 6.2.
Table 6.2: DWS forecasted service gap in terms of access ratio
Year
Parish
2000
2005
2010
St. Andrew
1.04
0.99
0.94
St. David
1.24
1.18
1.12
St. George
1.27
1.20
1.14
St. John
3.63
3.44
3.27
St. Mary
0.84
0.80
0.76
St. Patrick
1.08
1.02
0.97
St. Paul
0.46
0.44
0.41
Tobago
1.17
1.11
1.06
2015
0.90
1.07
1.09
3.12
0.72
0.93
0.39
1.01
2020
0.86
1.02
1.04
2.98
0.69
0.88
0.38
0.96
2025
0.82
0.97
0.99
2.85
0.66
0.85
0.36
0.92
The aggregate deficit projections for Tobago are presented in graphic form in Figure 6.1.
As discussed earlier, none of the municipal sanitation services is administered at the
parish level in Tobago. Thus from an operations perspective, the deficit projections at the
parish level are of little value. However, the aggregate values for Tobago show that the
capacity of the drinking water system goes from an estimated surplus of 17% in the year
2000, to a deficit of 4% by the year 2020, and 8% by the year 2025. This assumes an
average annual growth rate of 1.1%.
Figure 6.1: Tobago Projected Water Demand Versus Fixed Supply 2000 – 2025
Linear Projected Water Demand vs Fixed Supply 2000 - 2025.
140%
Supply as % of Demand
120%
117%
111%
106%
101%
100%
96%
92%
80%
60%
40%
20%
0%
2000
2005
2010
2015
2020
2025
Year
30
6.3
Wastewater and Sewage Treatment (WST)
The projected demand for water supply by parish over the 25-year planning horizon from
the year 2000 to the year 2025 is presented in Table 6.3.
Table 6.3: Total Projected Wastewater and Sewage Treatment Demand (m3/yr) by Parish 2000-2025
Parish
2000
2005
2010
2015
2020
2025
St. Andrew
4,701,510
4,960,093
5,218,676
5,477,259
5,735,842
5,994,425
St. David
2,228,688
2,351,266
2,473,844
2,596,422
2,718,999
2,841,577
St. George
1,593,108
1,680,729
1,768,350
1,855,971
1,943,592
2,031,213
St. John
890,406
939,378
988,351
1,037,323
1,086,295
1,135,268
St. Mary
880,605
929,038
977,472
1,025,905
1,074,338
1,122,771
St. Patrick*
4,435,893
4,679,867
4,923,841
5,167,815
5,411,789
5,655,764
St. Paul
1,607,364
1,695,769
1,784,174
1,872,579
1,960,984
2,049,389
Tobago*
16,337,574
17,236,146
18,134,717
19,033,289
19,931,860
20,830,432
*Amended from Tables 4.2, 4.4, and 5.2 to reflect 90% of true hotel water demand.
Assuming that demand remains constant at year 2000 levels (actually set at the levels
measured in August 2002), the ratio of supply to demand over the planning horizon is
summarized in Table 6.4.
Table 6.4: WST Projected Access Ratio (supply/demand), Assuming Fixed Supply 2000 – 2025
Parish
2000
2005
2010
2015
2020
2025
St. Andrew
0.66
0.63
0.60
0.57
0.54
0.52
St. David
0.00
0.00
0.00
0.00
0.00
0.00
St. George
0.00
0.00
0.00
0.00
0.00
0.00
St. John
0.00
0.00
0.00
0.00
0.00
0.00
St. Mary
0.00
0.00
0.00
0.00
0.00
0.00
St. Patrick
0.03
0.03
0.03
0.03
0.02
0.02
St. Paul
0.00
0.00
0.00
0.00
0.00
0.00
0.20
0.19
0.18
0.17
0.16
0.16
Tobago
The aggregate deficit projections for Tobago are presented in graphic form in Figure 6.2.
The aggregate values for Tobago show that the capacity of the wastewater treatment
system goes from an estimated deficit of 80% (supply is only 20% of demand) in the
year 2000, to a deficit of 84% by the year 2025. This assumes an average annual growth
rate of 1.1%. As noted earlier, the actual demand for wastewater service in Tobago is
likely to be significantly less than projected because of the pervasive use of cesspools and
septic drainfields across the island. However, as the density of housing increases, the use
of individual septic systems will become less viable and the need for wastewater
treatment capacity will increase. In the case of St. Patrick, the demand from the hotel
sector has already created a critical demand for a centralized wastewater treatment
facility with at least secondary treatment.
31
Figure 6.2: Projected Wastewater Demand Versus. Fixed Supply 2000 – 2025
Linear Projected Wastewater Demand vs. Fixed Supply 2000 - 2025.
25.0%
Supply as % of Demand
20.0%
19.8%
18.8%
17.9%
17.0%
16.3%
15.6%
15.0%
10.0%
5.0%
0.0%
2000
2005
2010
2015
2020
2025
Year
6.4
Municipal Solid Waste Management (MSW)
The absence of collection data by parish precluded the presentation of deficit projections
for this service by parish. The projected demand for municipal solid waste management
by parish over the 25-year planning horizon from the year 2000 to the year 2025 is
presented in Table 6.5.
Table 6.5: Projected Demand for MSW Service by Parish 2000-2025
Parish
2000
2005
2010
2015
St. Andrew
2,849
3006
3162
3319
St. David
1,351
1425
1500
1574
St. George
966
1019
1072
1125
St. John
540
570
599
629
St. Mary
534
563
593
622
St. Patrick
2,522
2661
2799
2938
St. Paul
974
1028
1081
1135
Tobago
9,735
10270
10806
11341
2020
3476
1648
1179
659
651
3077
1188
11877
2025
3632
1723
1232
689
681
3216
1242
12412
32
The aggregate deficit projections for Tobago are presented in graphic form in Figure 6.3.
These projections show that for the island as a whole, there was a deficit in disposal
capacity in the year 2000. With no additional capacity added, and an annual linear
increase in per capita demand of 1.1%, this deficit will grow 46% (supply is 54% of
demand) in year 2000 to 58% (supply is 42% of demand ) by 2025. Compounding would
have resulted in even larger projected deficits.
Figure 6.3: Projected MSW Demand vs. Fixed Supply 2000 – 2025
Linear Projected MSW Demand vs Fixed Supply 2000 - 2025
60%
54%
51%
Supply as % of Demand
50%
48%
46%
44%
42%
40%
30%
20%
10%
0%
2000
2005
2010
2015
2020
2025
Year
33
7.0 CONCLUSION AND RECOMMENDATIONS
7.1
Conclusions
The goal of this project was to assess the location, operating status, and capacity of the
physical facilities in Tobago’s municipal sanitation system. That system consists of
potable (drinking) water supply (DWS), wastewater and sewage treatment (WST), and
municipal solid waste management (MSW). The assessment did not include construction
and demolition debris, or medical and infectious waste. The assessment consisted of
recording and mapping the geographical location of all known facilities in the system,
using a Geographical Information System (GIS), interviewing facility operators to
determine the capacity and operating status of facilities, estimating the ratio of supply to
demand for service at the parish level, and for Tobago as a whole, and projecting the ratio
of supply to demand for each service from 2000 to 2025, assuming no expansion in
capacity. The assessment was conducted in August 2002.
The assessment of facilities included mapping 31 facilities in WASA’s water supply
system, 16 facilities in the wastewater and sewage system, and 8 facilities in the
municipal solid waste management system. As of August 2002, annual water supply was
calculated at 21.3 million m3/year (5,630 million gallons per yer - mgy) against a demand
of 17.9 million m3/year (4,730 mgy), a surplus of 19%. In the case of wastewater
treatment, total potential demand was estimated at 3.2 million m3/year (845 mgy) against
a demand of 16.1 million m3/year (4,250 mgy), a deficit of 80%. This deficit must be
qualified by noting that the majority of wastewater and sewage demand in Tobago is
currently supplied by septic tank systems and by direct discharges of wastewater into
drains that lead to land or surface water. Thus the true ratio of supply to demand for
wastewater and sewage treatment service in Tobago was not determined in this
assessment. Municipal solid waste generation totaled 9,740 tons per year against landfill
disposal receipts of 5,200 tons per year, a deficit of 46%. This deficit is also an estimate
since data on total MSW collections were not available, and collection vehicles were not
consistently weighed upon arrival and departure from the Studley Park Landfill.
Projections of the ratio of supply to demand were made over a 25-year planning horizon
from 2000 to 2025 using a conservative linear growth estimate in per capita demand, and
assuming that supply remained fixed at year 2000 levels. The results indicated that at a
1.1% annual population growth rate, water supply would go from surplus to deficit status
between 2015 and 2020, and would be at an 8% deficit in 2025. If it became necessary to
supply wastewater service to all users in the island, the current supply could meet only
20% of demand, and would drop to 16% by the year 2025. As housing density increases
the use of individual septic systems will become less viable, requiring a shift to public
wastewater treatment. Monitoring of groundwater quality for coliform contamination,
and strategic sampling of the vadose zone for the presence of coliform will provide useful
indicators of the time to shift from household septic systems to public sewer with
34
secondary treatment. In the case of municipal solid waste, the deficit in disposal capacity
increased from 46% in 2000 to 58% in the year 2025.
Assessment of the operating status of facilities revealed that all components of the
WASA water supply system were operating at their design capacity. Significant silting
was observed at the Hillsborough Reservoir, though the actual loss from its 852,000m3
(225 million gallon)15 design capacity was not determined. The operators of the
Richmond, Kings Bay, Moriah, and Courland water treatment facilities gave impressive,
detailed explanations of the operation of their respective facilities. The tour of the
Richmond Water Treatment Plant conducted by Mr. Ian Robley was outstanding.
The wastewater treatment facilities were more troubling. The Smithfield Wastewater
Treatment Plant was operating as designed, though at only 11% of its 8,250m3 per day
(2,250,000 gpd) capacity. Mr. Cassius Mills, engineer and chief operator of the facility
conducted an outstanding and informative tour of every aspect of the facility’s operation.
He noted the need for an additional trained operator, for funds to paint and maintain the
equipment as protection from rust (the plant is located less than I kilometer from the
ocean), and a system to remove residual chlorine from the effluent discharged from the
facility into a drain that empties into Rockly Bay. The facilities at Crown Point and
Buccoo/ Coral Gardens were operating within tolerable limits, but showed evidence of
algae growth around the discharge points, with significant odor emanating from the
Crown Point unit. The Bon Accord Integrated sewage treatment plant was visually
inspected during a tour conducted by Mr. Cassius Mills. The facility appeared to be
operating within tolerable limits, though there were questions raised about the frequency
with which accumulated sludge was removed from the aerator and settling tank. The
Milford Court sewage treatment plant was choked with accumulated sludge, and was not
providing effective digestion of influent wastewater. A lack of removal of sludge from
this unit was blamed on the interruption of pumping service by the Solid Waste
Management Company. Effluent from this facility must be assumed to be discharged to
the environment without adequate treatment for the removal of nutrients, and the
destruction of pathogenic bacteria. The consistency of chlorination of the effluent was not
determined for this facility. Only 1 of the 9 hotel package sewage treatment units
inspected was operating within design parameters by a trained operator. None of the other
units had an operator that was trained in the proper use of the unit. This was reflected in
the complete failure of the remaining units to provide digestion of nutrients from their
influent wastewater, and inconsistency in the application of chlorine to the effluent from
the units. This is a potentially dangerous public health situation, and a grievous
ecological insult to the bodies of water and land that receive the effluent from these units.
This deficit requires immediate remediation. Indeed, all of the non-functional package
sewage treatment systems were located in the parish of St. Patrick, which has an urgent
need for expanded wastewater and sewage treatment capacity to handle the volume of
wastewater being produced and discharged into its environs.
The municipal solid waste system was also found to be in trouble. Based on receipts
derived from a count of the number of vehicles arriving at the Studley Park landfill over a
4-day period, the total tonnage of disposal provided annually amounted to only 54% of
35
MSW generated island-wide. Littering of plastic, beverage cans and bottles was
pervasive around Scarborough and the more popular beaches. A contributing factor to
this is the shortage of rubbish receptacles within easy access to the public. Another factor
may be the lack of regular collection and removal of the solid waste from the units that
are available, and from residences in general. No data on MSW collections were
available, and time did not permit the investigators to document the frequency and route
of collection vehicles in each village across the island. There were no transfer stations in
use to shorten the route of collection vehicles prior to hauling to the landfill. No MSW
recycling or composting programs were documented. Some leachate from the Studley
Park Landfill was collected and evaporated in a sludge pond near the entrance to the
facility. The dried sludge from this pond was applied to the land as a means of disposal.
Other than the single drain observed, there is no leachate drainage and collection system
designed into the Studley Park Landfill. Thus it is reasonable to assume that there is
significant fugitive leachate draining from the facility. This could be migrating into
groundwater and into other nearby streams, which ultimately empty into Bay that is
within 1 kilometer of the landfill entrance. This situation requires urgent attention, as
fishermen were observed to be drawing nets in that Bay on multiple occasions. There was
no landfill gas management system evident at the landfill, despite the likely high
putrescible content in the waste disposed at the facility. This poses the risk of explosions
and damage to workers at the landfill, especially in the presence of open flames. At
minimum, workers at the landfill should be educated about this risk. It would be better,
thoug costly, to build a landfill gas management system at the facility.
The mapping component of this project was completed successfully. The coordinates of
all facilities are available on CD for use by WASA and the Health Department. Capacity
and operating status assessment was generally favorable for the water supply service but
troubling for the wastewater and solid waste services. Urgent attention is required to the
wastewater treatment needs of St. Patrick parish, where the majority of Tobago’s hotels
are located. Urgent attention is also required to trace, collect, and treat leachate from the
Studley Park landfill.
7.2
Recommendations
7.2.1
Water Supply
Wells are an important component of the water supply system in Tobago, providing more
than 25% of its total daily output. This role warrants careful monitoring of the
groundwater resource from which these wells are fed. Monitoring of seasonal variations
in the static water level and studies of the consumption versus recharge rate of the
supporting aquifer are critical to planning the conservative use of this resource. The
absence of such studies poses the risk that rate of consumption of water from the wells
could exceed the recharge rate of their supporting groundwater source, resulting in the
ultimate depletion of the resource. For those wells, like those at the government farm,
36
that are located close to the ocean, an excessive drawdown of the groundwater could lead
to saltwater intrusion, a difficult, if not permanent, compromise to the well water supply.
Thus, it is recommended that a groundwater monitoring program be instituted to assess
the rate of consumption of well water relative to the recharge rate of each unit.
The simple linear model projected a deficit in the water supply to the island around the
year 2015, if demand grows at the modest rate of 1.1% per year. In order to avoid a
shortage, it is recommended that steps to add new storage capacity and potential
groundwater sources commence no later than 2010, allowing 5 full years to identify,
build, and connect the new sources to the existing infrastructure.
7.2.2
Wastewater and Sewage Treatment
The recommendation for wastewater and sewage treatment is direct and concise. There is
a troubling shortage of wastewater treatment capacity in St. Partick parish that must be
corrected with urgency. Simply fixing the performance of existing hotel package units is
not likely to meet more than 20% of the total wastewater and sewage treatment demand
in the parish. In order to minimize the risk to human health and the environment from
inadequately treated wastewater and sewage discharges in the parish, it is recommended
that detailed studies begin immediately of alternatives to either minimize the flow of
wastewater, or provide at least secondary treatment of these discharges. A public
wastewater treatment plant is one of the options in this set of alternatives.
It is also recommended that hydrological studies begin to assess the impact of
septic systems on coliform contamination of groundwater and the vadose zone in parts of
Tobago where there are dense concentrations of houses with single septic systems. This
monitoring would provide information on the need to move from the individual
household septic system to alternatives, such as sewerage, for these areas.
7.2.3
Municipal Solid Waste Management
A quick intervention for the littering problem is to provide more rubbish receptacles
within easy access of the public, particularly in areas where crowds congregate, such as
throughout Scarborough, the popular beaches, and in social centers in villages. Tracking
the routes and loading of collection vehicles would provide information on the benefit of
building transfer stations to which these vehicles could dump their partial loads after
short segments of their route, to ensure that they always made fully loaded trips from the
transfer station to the landfill.
Studies to characterize Tobago’s MSW are needed to determine the exact quantity of
waste generated, the composition of the waste stream, and the changes in the quantity and
composition of the waste stream over time. This characterization could be accomplished
by weighing all trucks when they enter and as they exit the Studley Park landfill,
provided there is no significant illegal dumping. The waste entering the landfill could be
separated into its main components; paper, plastic, glass, aluminum, other metal, bulk
37
goods, and putrescibles. With each component weighed on a dry and wet basis.
Conducting this assessment at least once each wet and dry season would provide dynamic
data on the quantity and component of the MSW stream. This information could then be
used to determine the feasibility of a recycling program and or a composting program for
putrescible material.
Though it will be difficult to control leachate passing into groundwater from the unlined
Studley Park Landfill, it is feasible to identify and control leachate discharges into
streams that adjoin the landfill. This is urgent because of the potential for harmful organic
acids and metals in the leachate, and the proximity of the landfill to the Bay at Studley
Park, where there is regular fishing activity.
7.3
Other Issues
The issue of pleasure crafts cuts across all services. Yachts were observed docked at the
Bay in Charlottesville, at Store Bay, At Englishman’s Bay in Castara, and off Roackly
Bay in Scarborough. These vessels, along with larger cruise ships, are potential sources
of wastewater and sewage, and solid waste discharges into the coastal waters in and
around the areas they frequent. Ideally, a consistently enforced ordinance banning the
discharge of wastewater, sewage, and/or solid waste within a sufficient distance of the
shore to ensure safety, would be enacted to minimize any risk of pollution from these
vessels. Neither the ordinance nor the enforcement were evident during the period of
August 2002, when these vessels were observed. Considering their ability to discharge
pollutants into the treasured waters of Tobago’s coast, it is important that a program be
instituted to assess the size of the risk posed by discharges from these vessels, and to
control these discharges, by providing a waste collection and disposal service.
38
8.0
ACKNOWLEDGEMENTS
This study could not have been conducted without the approval and support of the Chief
Secretary of the Tobago House of Assembly, Mr. Orville London. The investigators
thank him and his office for their gracious support.
The study was greatly facilitated by the coordination of WASA water engineer, Mr. Brian
Williams. Mr. Williams arranged the site visits to all of the WASA water facilities, and
was infinitely patient in explaining the organization, administration, and operation of the
island-wide water distribution system. The investigators thank him and all the members
of the staff at Lowlands for their friendly and helpful support.
The investigators also thank Mr. Cassius Mills, WASA wastewater engineer, for his
extraordinary helpfulness and patience in explaining and providing a guided tour of
Tobago’s wastewater and sewage system.
The investigators thank all the water treatment plant operators for their patient and
forthright explanation of the operation of their facilities, and for the guided tours of these
facilities they provided. The knowledge and conscientiousness of these operators was
impressive.
The investigators thank the hotel sewage system personnel for providing access to the
facilities, and for providing frank answers to all questions to the best of their knowledge.
This study was supported by a research grant from the National Science Foundation (BES
#9984318), and from a travel grant provided by the Virginia Engineering Foundation.
The investigators thank these agencies for their generous support.
39
Table A1. Geographical Coordinates of Tobago Water Supply Facilities
FULL NAME
LAT
LON
King Peters Bay Booster
+11.2518900
-60.7138300
Parrot Hall Booster #2
+11.2972000
-60.6563200
Parrot Hall Booster #1
+11.3010400
-60.6350100
Bloody Bay Lift Station
+11.3022400
-60.6259000
L'anse Forum Booster
+11.3106400
-60.6263200
Bloody Bay Booster #1
+11.2933900
-60.6288100
Bloody Bay Booster #2
+11.2905000
-60.6259700
Craig Hall Intake
+11.2276000
-60.7164100
Fort Cambleton Well
+11.3213100
-60.5486600
Hillsboro Resevoir
+11.2259800
-60.6696900
Richmond Holding Tank
+11.2338300
-60.6032300
Courland Holding Tank
+11.2096200
-60.7611000
Bloody Bay
+11.2845000
-60.6258100
Signal Hill Holding Tank
+11.1767700
-60.7673600
Charlotteville Well #1
+11.3213900
-60.5442200
Belmont Well
+11.2118900
-60.6996400
Daniel Trace Well
+11.1676300
-60.7851000
Diamond Estate Well #1
+11.1700200
-60.7718600
Diamond Estate Well #2
+11.1698400
-60.7694200
Government Farm (2 wells)
+11.1797900
-60.7490900
Government Farm #2
+11.1787700
-60.7491300
Bacolet Well (Stadium)
+11.1832600
-60.7171400
Bloody Bay Well
+11.3013900
-60.6268600
Charlotteville Well #2
+11.3215600
-60.5457000
Charlotteville Well #1
+11.2127200
-60.6999700
Hillsborough Water Treatment
+11.2239900
-60.6696200
Richmond Water Treatment
+11.2252800
-60.6111100
Courland Water Treatment
+11.2164400
-60.7696100
Highland Water Treatment
+11.2368200
-60.7185300
King's Bay Water Treatment
+11.2848800
-60.5449600
Hillsborough West Water Treatment
+11.1974700
-60.6932600
CODE NAME
BSTR1
BSTR2
BSTR3
BSTR4
BSTR5
BSTR6
BSTR7
CRGHALL
FRTCMB
RES1
TANK1
TANK2
TANK3
TANK4
WELL10
WELL11
WELL1C
WELL2DE
WELL3DE
WELL4GF
WELL5+6GF
WELL7BA
WELL8
WELL9
WELLXYZ
WTP1
WTP2
WTP3
WTP4
WTP5
WTP6
40
Table A2. Geographical Coordinates of Tobago Wastewater Treatment Facilities
LONGNAME
LAT
LON
Blue Haven Hotel
+11.1725600
-60.7243300
Hilton Resort
+11.1472700
-60.7873200
Grafton Beach Resort
+11.2031300
-60.7848800
Turtle Beach
+11.2136300
-60.7761000
Sandy Point Hotel
+11.1521300
-60.8442200
Tropikist Hotel
+11.1527500
-60.8446700
Crown Point Beach Hotel
+11.1539300
-60.8418400
Coco Reef Resort
+11.1573900
-60.8378600
The Palms Hotel
+11.1834300
-60.7542300
Store Bay Public Beach Facilities
+11.1556500
-60.8387600
Smithfield Sewer Treatment Plant
+11.1833300
-60.7414100
Bon Accord Integrated
+11.1615000
-60.8301700
Airport STP
+11.1515100
-60.8417200
Milford Court
+11.1601400
-60.8203300
Coral Gardens/Bucoo
+11.1802300
-60.8028900
Charlotteville Bay Area
+11.3245600
-60.5486200
CODE NAME
HTL1
HTL2
HTL3
HTL4
HTL5
HTL6
HTL7
HTL8
HTL9
SBBEACH
STP1
STP2
STP3
STP4
STP5
YACHT1
41
Table A3. Geographical Coordinates of Tobago Solid Waste Disposal Facilities
LONGNAME
LAT
LON
Kilgwyn Beach Dump
+11.1520100
-60.8137100
Goldon Grove Dump
+11.1722400
-60.8025800
Orange Hill Trace Dump
+11.1843100
-60.7536200
Entrance Studley Park
+11.1958500
-60.6643100
Smithfield Sludge Ponds
+11.1829300
-60.7422000
Studley Park Sludge Ponds
+11.1966400
-60.6644700
Richmond Sludge Ponds
+11.2257000
-60.6102600
Courland Sludge Ponds
+11.2170600
-60.7697600
CODE NAME
DUMP1
DUMP2
DUMP3
LNDFL
SLDGEP1
SLDGEP3
SLDGP2
SLDGEP4
42
Table A4. Villages by Parish in Tobago.
ST. ANDREW
Patience Hill
1724
Scarborough/extended
14106
15830
ST. DAVID
Arnos Vale
277
Bethesa
1071
Castara
590
Culloden
574
Golden Lane/Les Coteaux
1171
Mary's Hill
363
Moriah
1898
Plymouth
1163
Whim
397
7504
ST. GEORGE
Belmont
702
Concordia
668
Easterfield
670
Hope Farm/Blenheim
949
Mason Hall
1000
Mount St. George
1375
5364
ST. MARY
Glamorgan
636
Goodwood
1228
Pembroke, Studley Park
1101
2965
ST. JOHN
Bloody Bay
Campbleton/Charlotteville
Charlotteville
L'anse Fourmi
Lucy Vale
Parlatuvier
Speyside
Top Hill
ST. PATRICK
Black Rock/Mt. Irvine
Bon Accord
Bucco/Coral Gardens
Canaan
Carnbee/Mt. Pleasant
Crown Point
Lowlands
Milford Court
Old Grange/Bethel
Orange Hill
ST. PAUL
Argyle/Kendal
Belle Gardens/Zion Hill
Besty's Hope/Delaford/Louis D'or/Lands Sett.
Delaford
King's Bay
Roxborough
145
267
992
219
331
290
59
695
2998
1941
2247
1090
1706
1726
525
1110
799
2490
377
14011
524
809
1258
700
309
1812
5412
1
The Tobago Region Development Plan, Town and Country Planning Devision, Sept. 1, 1999.
EMA, Annual Report 1999, Environmental Management Authority, 1999.
3
http://www.wasa.gov.tt/index.php?temp=general&main=dsp_companyinfo1&nav=1
4
SEDU 2003. Environmental Management Insertion in Tourism Sector Policies in the Caribbean – Final
Report to the Inter American Development Bank. The Sustainable Economic Development Unit. University
of the West Indies Department of Economics. St. Augustine, Trinidad. 15 May 2002.
5
Qasim, S., Wastewater Treatment Plants: Planning, Design, and Operation, 2 ed., Technomic Publishing,
Lancaster, PA. 1999
6
Handover Document for The Studley Park Integrated Waste Disposal Facility, December, 1988.
7
The Trinidad and Tobago Solid Waste Management Company Limited, Studley Park Landfill Interim
Development Plan, 1989.
8
Akili, Kamaui, The Sustainable Management of Tobago's Water Resources, Environment TOBAGO,
October 23, 2000.
2
43
9
UNFAO Aquastat Information Service 2003
http://webworld.unesco.org/water/ihp/db/shiklomanov/part'3/HTML/Tb_21'TT.html
11
Akili, Kamaui, 2000.
12
Qasim, 1999)
13
United Nations Environment Program, Global Environmental Outlook 2000 Report. Chapter 2: The State
of the Environment in Latin America and the Caribbean, UN, 2000.
14
CSO 2000. Trinidad and Tobago 2000 Housing and Population Census, Central Statistical Office,
Ministry of Planning and Development, Government of the Republic of Trinidad and Tobago. May 2002.
15
Water and Sewage Authority official website.
http://www.wasa.gov.tt/index.php?temp=general&main=dsp_damsinfo2&nav=4
10
44