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API PUBL 4722-2002 pdf free download

API PUBL 4722-2002 pdf free download.Groundwater Sensitivity.
The first question is designed to rule out potential transport through aquitards if there is strong hydrogeologiústratigraphic information that the aquitard is likely to prevent vertical transport to this water-bearing unit. The second question provides a quantitative tool to estimate the resulting concentration in this water-bearing unit after groundwater migrating from the upper water-bearing unit through the aquitard mixes with groundwater in this water-bearing unit. This calculation is based on potentiometric level, aquifer thickness, concentration in the contaminated unit, mixing layer thickness, and ultimate length of plume in the upper unit. The equations used in this calculation may be viewed by clicking the “See graphic of flow-through aquitard” button. Once the concentration has been calculated, the user may compare the lower unit concentration to the MCL or other relevant regulatory standard to answer Question 2. Mass flux information associated with transport through the aquitard is also provided.
For Question 1, the software development committee has utilized a distance of 2500 ft to help users decide if there is a municipal water supply well or discharge point close enough to the site of interest that the well might be threatened by a potential release. To answer “yes” to Question 1, the well must be screened in the water-bearing unit that is being analyzed. If a discharge point is being considered, then the site of interest must be located upgradient of the discharge point. Note that 2500 ft is used as an example plume length for a recalcitrant compound. The user may elect to use 1200 ft if the constituent of concern is known to degrade significantly in groundwater or otherwise use a distance that represents the longest plume length for the constituent in concern in that area, assuming that the plume used for reference has stabilized. For Question 2, the user should indicate if the site of interest is located near a fractured bedrock or karst water-bearing unit that is being used for a water supply. This question was adapted from California’s “Guidelines for Investigation and Cleanup of MTBE and Other Oxygenates, 2001 .” Question 3 permits the user to enter data for up to four wells to determine if a plume emanating from the site of interest lies within the capture zone of the well. The capture zone is determined individually for each well, and collective drawdown from a group of wells is not considered in this calculator. The user may view the capture zone for an individual well by clicking the radio buttons below the input column for that well.
The second question, in seven parts, asks for various site parameters to calculate a DRASTIC index for the site. The DRASTIC index is calculated by assigning a weight to each site parameter, then multiplying the DRASTIC rating for that parameter by its weight. The final score is calculated by adding all the weighted ratings. Several parameters have a “Select” button located to the right of the input cell. The user should click the Select button for that parameter to choose the correct input from a list of options. DEPTH TO WATER Depth to water determines the depth of material through which a contaminant must pass prior to reaching the water-bearing unit. Greater depth of material allows more opportunities for attenuation factors, such as biodegradation or adsorption, to prevent a contaminant from entering the aquifer. For confined water-bearing units, this depth corresponds to the depth of the base of confining unit. The developers of DRASTIC derived the following ranking system for depth to water:

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