API PUBL 4722:2002 pdf download
API PUBL 4722:2002 pdf download.Access to Additional Content for PUBL 4722.
PURPOSE
Groundwater sensitivity is a key consideration in the development and implementation of appropriate corrective actions at potential release sites, such as leaking underground storage tanks, landfills, and other sources. Experience shows that actual impacts on critical water supply resources have occurred at a relatively small number of sites. Due to the risk of potential exposure, these high-sensitivity sites should warrant a large percentage of the available public and private resources for release prevention, assessment, and remediation
However, practical, site-specific measures of groundwater sensitivity may not be sufficiently considered in release prevention efforts and the development of remediation goals. As a result, low sensitivity and high sensitivity sites may be frequently treated as equivalent concerns. This results in an inefficient allocation of available remediationiprevention dollars.
The Groundwater Sensitivity Toolkit is a decision support expert system that allows a user to enter site-specific parameters to generate a scorecard for that site This scorecard, when compared to the scores for other sites in a portfolio, gives the decision-maker insight into how resources should be allocated amongst the portfolio.
METHOD
This scorecard is based on three separate but related issues for a site:
The first four questions address any policy-based usage of this aquifer. In the toolkit, policy-based considerations override the engineering considerations when determining resource value for an aquifer. The fifth question, in two parts, addresses the two major limitations on water production from an aquifer.
POLICY QUESTIONS
1. If groundwater use is precluded by some type of regulation or law (such as a no-pumping rule) then the Resource Value is defined as LOW as it is not usable as a resource for water-supply purposes.
2. If the water-bearing unit is a sole-source aquifer as defined by federal or state regulations. then the Resource Value is defined as HIGH as the water-bearing unit is a vital water supply resource.
3. If the water-bearing unit is currently being used in the vicinity of the site of interest, then the Resource Value is considered to be HIGH as it is a usable water supply resource. For the purposes of this software, the software development committee used a distance of 2500 ft to determine if water supply wells (either domestic, municipal, irrigation, or industrial) that are screened in the water-bearing unit have the potential for being affected by the site of interest. This distance was based on general experience about the potential conservative (high-end) length of contaminant plumes.
4. If there is a formally adopted water supply plan (adopted by reguLatory body such as a city, county, regional planning board, state, etc.) that indicates that the unit may be used as a
drinking water supply in the near future (i.e.. within a few years), then the Resource Value is automaucally upgraded to MEDIUM,
RESOURCE USABILITY: Well Yield
Determination of well yield addresses the ability of a unit to produce water and is a primary concern when deciding if a water-bearing unit with no production or policy information has the potential to become a water supply resource. The well yield is determined from calculations based on hydraulic conductivity, aquifer thickness, and confining head, The software development committee developed the following rules to define Resource Value as a function of well yield based on regulatory approaches used in several states:
In addition, the software asks the user if a regional contaminant (such as nitrate) is above the
MCL (either secondary or primary)口If it is, then the Resource Value is defined as being LOW.
Examples of regional contaminants include nitrate, radium, coliform, and some wide-scale man-
made contaminants (wide-scale means not from a particular site of interest). In many cases, the
regional contaminant will come from diffuse non-point sources rather than from a particular site.
