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Coral sedimentation on the coasts of Puerto Rico.

The quality of the surface and groundwater in Puerto Rico varies from excellent to highly contaminate, depending mainly on the geographical location of the water resources and the time of the year. Even so, most of the waters meet the standards set by the Environmental Quality Board (EQB) and the Environmental Protection Agency (EPA) as sources for the production of drinking water.

The Quality of Surface Waters

Studies carried out by the EQB (Reports 303(d) and 305(b)) and the US Geological Survey (USGS) show that the principal problems of surface water quality in Puerto Rico are the presence of bacteria of fecal origin, nutrients and suspended sediments. The concentrations of these contaminants- for the most part from the segments of rivers, streams and reservoirs that have been studied- exceed the local and federal standards for human contact.

The data from 2002 on concentrations of bacteria of fecal origin in the network of USGS stations in Puerto Rico are summarized in Figure 1 . The concentrations of nutrients in the network of USGS stations in Puerto Rico are presented in Table 1 . Only in isolated areas of the mountains, or in protected forest reserves, does the quality of surface waters remain unaffected by such contaminants. During periods of intense runoff in the rainy season in Puerto Rico the concentration of bacteria and nutrients tends first to increase in the early stages of such events (washout), then decrease as the runoff dilutes the matter. On the other hand, this process increases the concentration of suspended sediment significantly.

The federal Safe Drinking Water Act (SDWA 1974, as amended) does not set quality norms for sources to be used for supply of drinking water. However, it does delegate to the Health Department (HD) the adoption of additional requirements to guarantee the quality of drinking water at the local level.

The Health Department requires the Autoridad de Acueductos y Alcantarillados (AAA, Aqueducts and Sewer Authority) and other entities that propose the development of new water distribution systems to comply with the following norms:

To complete a sanitary survey in the drainage basin or aquiferaquiferous confined and unconfined: a geological formation in which there is a capacity to accumulate underground water that may surface naturally (as in springs) or be extracted artificially for consumption (as with wells). Aquifers may be confined or unconfined. In confined aquifers the water is contained between layers of impermeable material; in unconfined aquifers, the water is located between porous layers. that is to be the source of the water to be treated to serve as drinking water.

To comply with the regulations set out in the SWDA, including the Filtration Rule, Disinfection Products Rule, Total Coliforms Rule from the Safe Drinking Water Act, among others.

To cooperate with the HD and the EQB in evaluating the design of new drinking water treatment plants to assure that the physical and chemical processes provide appropriate treatment to comply with the SDWA.

The EQB has established, as part of the norms for water quality, the maximum concentrations for certain permitted parameters in waters for different human activities (Article 3 of the Regulations on Water Quality Standards, Regulation No. 6616 of May 14, 2003). These regulations set the norms and requirements for maintaining the bodies of water in Puerto Rico so that they will be adequate for the different uses for which they may be designated. The standards established control the water quality to protect the health of the population and to facilitate the economic growth of Puerto Rico.

The EQB norms are the guidelines used by the HD in its review of new drinking water production systems. These norms for water resources should not be confused with the federal drinking water standards, which include another series of water compliance parameters for water already purified for human consumption. In the case of raw waters, the EQB and the EPA require that the water source comply with Regulation No. 6616. These norms were set taking into account the chemical and physical techniques and processes used generally in modern treatment plants water to make water safe to drink. It is possible that if the concentration of a chemical or biological component of the raw waters exceeds a certain limit, the available treatment processes will not be adequate to guarantee that the water will meet the federal standards for drinking water. In such cases, the HD may refuse to issue a permit to use the water as a source of public supply.