4.2.2.3.2 Population. Evaluate the population factor for the watershed based on three factors: Level I concentrations, Level II concentrations, and potential contamination. Determine which factor applies to an intake as specified in section 4.2.2.3. Determine the population to be counted for that intake as specified in section 4.1.2.3.2, using the target distance limits in section 4.2.1.4 and the hazardous substance migration path in section 4.2.1.2.

4.2.2.3.2.1 Level I concentrations. Assign a value to this factor as specified in section 4.1.2.3.2.2.

4.2.2.3.2.2 Level II concentrations. Assign a value to this factor as specified in section 4.1.2.3.2.3.

4.2.2.3.2.3 Potential contamination. For each applicable type of surface water body in table 4-14, determine the dilution-weighted population value as specified in section 4.1.2.3.2.4. Select the appropriate dilution weight adjustment value from table 4-27 as specified in section 4.2.2.3.1.

Calculate the value for the potential contamination factor (PC) for the watershed as follows:

A=Dilution weight adjustment value from table 4-27. W1=Dilution-weighted population from table 4-14 for surface water body type i. n=Number of different surface water body types in the watershed.

If PC is less than 1, do not round it to the nearest integer; if PC is 1 or more, round to the nearest integer. Enter the value in table 4-25.

4.2.2.3.2.4 Calculation of population factor value. Sum the factor values for Level I concentrations, Level II concentrations, and potential contamination. Do not round this sum to the nearest integer. Assign this sum as the population factor value for the watershed. Enter this value in table 4-25. 4.2.2.3.3 Resources. Assign a value to the

4.2.2.3.4 Calculation of drinking water threat-targets factor category value. Sum the nearest intake, population, and resources factor values for the watershed. Do not round this sum to the nearest integer. Assign this sum as the drinking water threat-targets factor category value for the watershed. Enter this value in table 4-25.

4.2.2.4 Calculation of drinking water threat score for a watershed. Multiply the drinking water threat factor category values for likelihood of release, waste characteristics, and targets for the watershed, and round the product to the nearest integer. Then divide

by 82,500. Assign the resulting value, subject to a maximum of 100, as the drinking water threat score for the watershed. Enter this score in table 4-25.

4.2.3 Human food chain threat. Evaluate the human food chain threat for a watershed based on three factor categories: likelihood of release, waste characteristics, and targets. 4.2.3.1 Human food chain threat-likelihood of release. Assign the same likelihood of release factor category value for the human food chain threat for the watershed as would be assigned in section 4.2.2.1.3 for the drinking water threat. Enter this value in table 4 25.

4.2.3.2 Human food chain threat-waste characteristics. Evaluate the waste characteristics factor category for each watershed based on two factors: toxicity/mobility/persistence/ bioaccumulation and hazardous waste quan

tity.

4.2.3.2.1 Toxicity/mobility/persistence/bioaccumulation. Evaluate all those hazardous substances eligible to be evaluated for toxicity/mobility/persistence in the drinking water threat for the watershed (see section 4.2.2.2.1).

4.2.3.2.1.1 Toricity. Assign a toxicity factor value to each hazardous substance as specified in section 2.4.1.1.

4.2.3.2.1.2 Mobility. Assign a ground water mobility factor value to each hazardous substance as specified for the drinking water threat (see section 4.2.2.2.1.2).

4.2.3.2.1.3 Persistence. Assign a surface water persistence factor value to each hazardous substance as specified for the drinking water threat (see section 4.2.2.2.1.3), except: use the predominant water category (that is, lakes; or rivers, oceans, coastal tidal waters, or Great Lakes) between the probable point of entry and the nearest fishery (not the nearest drinking water or resources intake) along the hazardous substance migration path for the watershed to determine which portion of table 4-10 to use. Determine the predominant water category based on distance as specified in section 4.1.2.2.1.2.

4.2.3.2.1.4 Bioaccumulation potential. Assign a bioaccumulation potential factor value to each hazardous substance as specified in section 4.1.3.2.1.3.

4.2.3.2.1.5 Calculation of toxicity/mobility/ persistence/ bioaccumulation factor value. Assign each hazardous substance a toxicity/mobility factor value from table 3-9 (section 3.2.1.3), based on the values assigned to the hazardous substance for the toxicity and mobility factors. Then assign each hazardous substance а toxicity/mobility/persistence factor value from table 4-26, based on the values assigned for the toxicity/mobility and persistence factors. Then assign each hazardous substance a toxicity/mobility/persistence/bioaccumulation factor value from

table 4-28. Use the substance with the highest toxicity/mobility/persistence/bioaccumulation factor value for the watershed to assign the value to this factor for the watershed. Enter this value in table 4-25.

4.2.3.2.2 Hazardous waste quantity. Assign the same factor value for hazardous waste quantity for the watershed as would be assigned in section 4.2.2.2.2 for the drinking water threat. Enter this value in table 4-25. 4.2.3.2.3 Calculation of human food chain threat-waste characteristics factor category value. For the hazardous substance selected for the watershed in section 4.2.3.2.1.5, use its toxicity/mobility/ persistence factor value and bioaccumulation potential factor value as follows to assign a value to the waste characteristics factor category. First, multiply the toxicity/mobility/persistence factor value and the hazardous waste quantity factor value for the watershed, subject to a maximum product of 1×108. Then multiply this product by the bioaccumulation potential factor value for this hazardous substance, subject to a maximum product of 1x1012. Based on this second product, assign a value from table 2-7 (section 2.4.3.1) to the human food chain threat-waste characteristics factor category for the watershed. Enter this value in table 4-25.

4.2.3.3 Human food chain threat-targets. Evaluate two target factors for the watershed: food chain individual and population.

For both factors, determine whether the target fisheries are subject to Level I concentrations, Level II concentrations, or potential human food chain contamination. Determine which applies to each fishery (or portion of a fishery) as specified in section 4.1.3.3, subject to the restrictions specified in sections 4.2.1.3 and 4.2.1.4.

4.2.3.3.1 Food chain individual. Assign a value to the food chain individual factor as specified in section 4.1.3.3.1 with the following modification. When a dilution weight is used, multiply the appropriate dilution weight from table 4-13 by the adjustment value selected from table 4-27, as specified in section 4.2.2.3.1. Use the resulting product, not the value from table 4-13, as the dilution weight in assigning the factor value. Do not round this product to the nearest integer. Enter the value assigned in table 4-25.

4.2.3.3.2 Population. Evaluate the population factor for the watershed based on three factors: Level I concentrations, Level II concentrations, and potential human food chain contamination. Determine which of these factors is to be applied to each fishery as specified in section 4.2.3.3.

4.2.3.3.2.1 Level I concentrations. Assign a value to this factor as specified in section 4.1.3.3.2.1. Enter this value in table 4-25.

4.2.3.3.2.2 Level II concentrations. Assign a value to this factor as specified in section 4.1.3.3.2.2. Enter this value in table 4-25.

4.2.3.3.2.3 Potential human food chain contamination. Assign a value to this factor as specified in section 4.1.3.3.2.3 with the following modification. For each fishery being evaluated, multiply the appropriate dilution weight for that fishery from table 4-13 by the adjustment value selected from table 4-27, as specified in section 4.2.2.3.1. Use the resulting product, not the value from table 4-13, as the dilution weight for the fishery. Do not round this product to the nearest integer. Enter the value assigned in table 4–25.

4.2.3.3.2.4 Calculation of population factor value. Sum the factor values for Level I concentrations, Level II concentrations, and potential human food chain contamination for the watershed. Do not round this sum to the nearest integer. Assign this sum as the population factor value for the watershed. Enter this value in table 4-25.

4.2.3.3.3 Calculation of human food chain threat-targets factor category value. Sum the food chain individual and population factor values for the watershed. Do not round this sum to the nearest integer. Assign this sum as the human food chain threat-targets factor category value for the watershed. Enter this value in table 4-25.

4.2.3.4 Calculation of human food chain threat score for a watershed. Multiply the human food chain threat factor category values for likelihood of release, waste characteristics, and targets for the watershed, and round the product to the nearest integer. Then divide by 82,500. Assign the resulting value, subject to a maximum of 100, as the human food chain threat score for the watershed. Enter this score in table 4-25.

4.2.4 Environmental threat. Evaluate the environmental threat for the watershed based on three factor categories: likelihood of release, waste characteristics, and targets.

4.2.4.1 Environmental threat-likelihood of release. Assign the same likelihood of release factor category value for the environmental threat for the watershed as would be assigned in section 4.2.2.1.3 for the drinking water threat. Enter this value in table 4-25.

4.2.4.2 Environmental threat-waste characteristics. Evaluate the waste characteristics factor category for each watershed based on two factors: ecosystem toxicity/mobility/per

sistence/bioaccumulation and hazardous waste quantity.

4.2.4.2.1 Ecosystem toxicity/mobility/persistence/bioaccumulation. Evaluate all those hazardous substances eligible to be evaluated for toxicity/mobility/persistence in the drinking water threat for the watershed (see section 4.2.2.2.1).

4.2.4.2.1.1 Ecosystem toxicity. Assign an ecosystem toxicity factor value to each hazardous substance as specified in section 4.1.4.2.1.1.