Civil Engineering Reference
In-Depth Information
Evaluation of water quality to determine whether different or additional water
treatment is needed for existing and potential sources to meet current and future
water quality requirements.
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Changing Regulations
In its evaluation of water quality issues, a utility must consider and try to anticipate
changing regulations. For example, current water quality evaluations should consider
what changes in source of supply and / or treatment strategies may be required as a
result of implementing new federal Safe Drinking Water Act (SDWA) and state reg-
ulations for both surface water and groundwater. Chapter 1 provides a discussion of
anticipated water supply regulatory changes.
Existing Sources
As specified earlier in this chapter, existing sources of supply have already been listed
in the description of existing facilities. Thus, this section of the source-of-supply eval-
uation should briefly summarize the capacities and water quality characteristics of each
of the existing sources of supply.
Quantity
The total reliable capacity of each of the sources should be clearly defined.
For example, if the capacity of a well has been degrading over time, the actual firm
capacity of the well should be listed. For wells, any available water table depth infor-
mation should be summarized. Some surface water sources may have restrictions on
summer pumping because of low flows or minimum in-stream flow requirements in
the stream or river. The maximum and sustainable withdrawal rates, age, condition,
and estimated remaining life of each source should be listed.
Water Quality
The utility should summarize the raw and, if applicable, treated water
quality characteristics of each of the existing sources of supply. Any developing water
quality trends, such as increasing turbidity or more frequent positive coliform tests,
should be described. In addition, current applicable federal and state regulations re-
garding water quality of the system sources should be listed. Generally, the water
system will have to comply with provisions of the SDWA. Various states have codified
provisions of the SDWA in different ways and in some cases have added some of their
own, more stringent water quality requirements. The utility should make a brief eval-
uation of how well each of the sources complies with the provisions of the governing
water quality law.
Needs Assessment
The goal of this evaluation of existing sources is to determine
the need for additional sources of supply. The total firm capacity of the existing sources
should be compared to the range of projected demands to assess whether any additional
sources of supply will need to be developed. This comparison will determine both the
volume required and the schedule of development of new sources, if they are needed.
Finally, the needs assessment should state whether additional treatment of existing
sources is needed. In some cases, treatment can also serve to increase the firm capacity
of existing sources. For example, in cases where unfiltered surface water sources are
shut down because of high-turbidity events, filtration could add significantly to the
firm capacity of the sources.
