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Source Water Protection

Source Water Assessment Report

for the

Acoma Pueblo/Main Water Supply System

Acomita, New Mexico

Source Water Assessment Report for the Acoma Pueblo/Main Water Supply System
Acomita, New Mexico
April 30, 2001

Introduction

The 1996 amendments to the Safe Drinking Water Act authorizes a Source Water Assessment Program to determine the susceptibility of a public drinking water supply to contamination.  Sources of contaminants regulated by the Safe Drinking Water Act (i.e., contaminants with a Maximum Contaminant Level, contaminants regulated under the surface water treatment rule, and the microorganism cryptosporidium) are required to be inventoried during the assessment process.  The EPA Region 6 Source Water Protection Branch in cooperation with your drinking water system operators has conducted this assessment for your drinking water source. 

This one-time only "snap-shot" of the potential for water quality impacts to your source of drinking water is intended to serve as a starting point for you and your water supply system to initiate protection measures that will ensure an adequate quality of drinking water to meet the future needs of your Pueblo.

Background

A complete source water assessment consists of four key elements:

(1)  The first step is for assessment areas to be delineated for each of the system's ground water wells or surface water intakes (see Figure 1).  These delineations use available hydrogeologic factors for determining the areal extent of ground water sources for wells and the entire watershed drainage area for surface water intakes. 

(2)  Once the area to be assessed has been determined, a detailed potential contaminant source inventory is conducted within the delineated area.  A list of potential contaminant sources and their relative risk to ground water and surface water is presented in Appendix A.

(3)  The information gathered during the inventory process is then used to determine the relative susceptibility of the drinking water supply to the contaminant sources inventoried.  This susceptibility determination takes into consideration four factors: (a) the physical integrity of the well/intake structure; (b) the characteristics of the hydrologic system around the well/intake; (c) characteristics of the contaminants inventoried; and, (d) the likelihood of those contaminants to reach the source of the drinking water supply.  (See the "Assessment Summary" section of this report for a summary of your system's susceptibility to contamination.)

(4)  The final step in conducting an assessment is for the customers using the ground water or surface water source of drinking water to be informed about the availability of the complete assessment report.

After determining the susceptibility of the ground water and/or surface water sources of the system's drinking water supply, the system's susceptibility is determined by using the arithmetic mean of the source susceptibilities.  Systems that purchase their drinking water supplies from another drinking water system will share that system's susceptibility.  Table A illustrates how your system's susceptibility was calculated.

Table A - System and Source Susceptibility to Contamination Determination

Source ID	Source Name	High	Medium	Low
W0001	Acomita Lake #1	ü
W0002	Acomita Lake #2	ü
W0004	Acomita Lake #4	ü
W0005	Aanzac #3		ü
W0006	Aanzac #4			ü
W0007	Aanzac #5		ü
W0008	Aanzac #6		ü
	System Score		ü

Assessment Summary

Your drinking water supply primary source is not applicable. Your sources of drinking water come from the Quaternary Alluvial aquifer, the Dakota Sandstone aquifer, the Jurassic Zuni Sandstone Formation aquifer. Based on the four susceptibility factors discussed above, your system was determined to have a MEDIUM susceptibility to contamination.

Systems with a "High" susceptibility rating are strongly encouraged to implement management controls within the source water assessment area to minimize the threat of these potential sources of contamination.  Systems with a "Medium" susceptibility rating should consider implementing control measures that reduce the risk of potential contamination from sources closest to the well/intake.  Systems with a "Low" susceptibility determination should initiate a public education and outreach program that focuses on protecting the drinking water resource and informing the public about activities that threaten the quality of your drinking water supply.

This assessment is intended to serve as a tool for you and your water supply system to use as a start to a source water protection program.  To get further involved in protecting your source of drinking water, please contact your local water supply system operator to volunteer your time and talent.  For additional information about the federal Source Water Assessment Program, please do not hesitate to contact Ken Williams, EPA Region 6 Source Water Protection Program Coordinator at 214.665.7129 or e-mail him at williams.ken@epa.gov.

 

Acomita Lake wells # 1, 2, and 4 have been determined to be under the direct influence of surface water and therefore subject to potential sources of contamination (PSOCs) found in the watershed upstream from the wells (yellow lines delineate watershed boundary).  For assessment purposes, the location of these PSOCs have been identified (red crosses), but only those PSOCs located within 1,320 feet of the wells were used for calculating the well’s susceptibility to contamination.

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

Well Name:  Acomita Lake # 1                     Well Number: W0001

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 37.0 feet and is completed in the Quaternary Alluvial aquifer between the screened intervals of 15.0(*) and 35.0(*) feet. The Quaternary Alluvial aquifer is composed of unconsolidated, alluvial valley traversed by stream and the well is currently active. This type of aquifer is rated as having a HIGH susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
IAW-Inactive Water Well	MED	237	MED
IAW-Inactive Water Well	MED	250	MED
AWW-Abandoned/Improperly Constructed Water Well	HIGH	382	HIGH
MTW-Monitoring or Test Well	MED	529	MED
MTW-Monitoring or Test Well	MED	545	MED
AWW-Abandoned/Improperly Constructed Water Well	HIGH	613	HIGH
MTW-Monitoring or Test Well	MED	731	MED
AFL-Animal Feeding Area / Pens - Low Risk	LOW	813	LOW
SET-Single Family Septic System	MED	975	MED
AFL-Animal Feeding Area / Pens - Low Risk	LOW	1009	LOW
SET-Single Family Septic System	MED	1038	MED
SET-Single Family Septic System	MED	1203	LOW
AFL-Animal Feeding Area / Pens - Low Risk	LOW	1229	LOW
SET-Single Family Septic System	MED	1242	LOW
PGR-Paved/Gravel Local Road	LOW	1293	LOW
PDP-Promiscuous Dump	MED	1310	LOW

The cumulative risk associated with these PSOCs is HIGH.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	Yes
2. Is the casing exposed to surface water runoff?	No
3. Is the well site subject to flooding?	Yes
4. Is the upper termination of the well located outside a secured area?	Yes
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is HIGH.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a HIGH susceptibility to contamination.

(*) Estimated value based on Best Professional Judgement.

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

Well Name:  Acomita Lake # 2                     Well Number: W0002

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 38.0 feet and is completed in the Quaternary Alluvial aquifer between the screened intervals of 15.0(*) and 35.0(*) feet. The Quaternary Alluvial aquifer is composed of unconsolidated, alluvial valley traversed by stream and the well is currently active. This type of aquifer is rated as having a HIGH susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
IAW-Inactive Water Well	MED	324	MED
IAW-Inactive Water Well	MED	333	MED
AWW-Abandoned/Improperly Constructed Water Well	HIGH	425	HIGH
MTW-Monitoring or Test Well	MED	470	MED
MTW-Monitoring or Test Well	MED	498	MED
AWW-Abandoned/Improperly Constructed Water Well	HIGH	540	HIGH
MTW-Monitoring or Test Well	MED	651	MED
AFL-Animal Feeding Area / Pens - Low Risk	LOW	778	MED
AFL-Animal Feeding Area / Pens - Low Risk	LOW	998	LOW
SET-Single Family Septic System	MED	1012	MED
SET-Single Family Septic System	MED	1033	MED
SET-Single Family Septic System	MED	1223	LOW
AFL-Animal Feeding Area / Pens - Low Risk	LOW	1239	LOW
SET-Single Family Septic System	MED	1244	LOW
PGR-Paved/Gravel Local Road	LOW	1279	LOW
PDP-Promiscuous Dump	MED	1316	LOW

The cumulative risk associated with these PSOCs is HIGH.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	Yes
2. Is the casing exposed to surface water runoff?	No
3. Is the well site subject to flooding?	Yes
4. Is the upper termination of the well located outside a secured area?	No
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is MEDIUM.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a HIGH susceptibility to contamination.

(*) Estimated value based on Best Professional Judgement.

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

Well Name:  Acomita Lake # 4                     Well Number: W0004

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 32.0 feet and is completed in the Quaternary Alluvial aquifer between the screened intervals of 23.0 and 31.0 feet. The Quaternary Alluvial aquifer is composed of unconsolidated, alluvial valley traversed by stream and the well is currently active. This type of aquifer is rated as having a HIGH susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
MTW-Monitoring or Test Well	MED	364	MED
AFL-Animal Feeding Area / Pens - Low Risk	LOW	446	MED
MTW-Monitoring or Test Well	MED	630	MED
IAW-Inactive Water Well	MED	634	MED
IAW-Inactive Water Well	MED	650	MED
SET-Single Family Septic System	MED	690	MED
AWW-Abandoned/Improperly Constructed Water Well	HIGH	696	HIGH
AFL-Animal Feeding Area / Pens - Low Risk	LOW	708	MED
AWW-Abandoned/Improperly Constructed Water Well	HIGH	773	HIGH
MTW-Monitoring or Test Well	MED	783	MED
SET-Single Family Septic System	MED	976	MED
PGR-Paved/Gravel Local Road	LOW	976	LOW
AFL-Animal Feeding Area / Pens - Low Risk	LOW	994	LOW
SET-Single Family Septic System	MED	1016	MED
DWW-Domestic Water Well	MED	1051	MED
PDP-Promiscuous Dump	MED	1060	MED
SET-Single Family Septic System	MED	1104	LOW
JKY-Junk Yard (domestic)	MED	1124	LOW
SET-Single Family Septic System	MED	1132	LOW
PGR-Paved/Gravel Local Road	LOW	1198	LOW
SHW-State/Federal Highway	MED	1255	LOW

The cumulative risk associated with these PSOCs is HIGH.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	Yes
2. Is the casing exposed to surface water runoff?	No
3. Is the well site subject to flooding?	Yes
4. Is the upper termination of the well located outside a secured area?	Yes
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is HIGH.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a HIGH susceptibility to contamination.

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

 

Well Name:  Aanzac # 3                    Well Number: W0005

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 160.0 feet and is completed in the Dakota Sandstone aquifer between the screened intervals of 103.0 and 152.0 feet. The Dakota Sandstone aquifer is composed of sandstone and the well is currently active. This type of aquifer is rated as having a LOW susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
SET-Single Family Septic System	MED	410	MED
SET-Single Family Septic System	MED	495	MED
SET-Single Family Septic System	MED	515	MED
JKY-Junk Yard (domestic)	MED	548	MED
AFL-Animal Feeding Area / Pens - Low Risk	LOW	948	LOW
SET-Single Family Septic System	MED	1010	MED
SET-Single Family Septic System	MED	1071	LOW
SET-Single Family Septic System	MED	1103	LOW
SET-Single Family Septic System	MED	1104	LOW
PGR-Paved/Gravel Local Road	LOW	1130	LOW
SET-Single Family Septic System	MED	1255	LOW

The cumulative risk associated with these PSOCs is HIGH.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	No
2. Is the casing exposed to surface water runoff?	No
3. Is the well site subject to flooding?	No
4. Is the upper termination of the well located outside a secured area?	No
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is LOW.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a MEDIUM susceptibility to contamination.

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

 

Well Name:  Aanzac # 4                    Well Number: W0006

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 440.0 feet and is completed in the Jurassic Zuni Sandstone Formation aquifer between the screened intervals of 230.0 and 410.0 feet. The Jurassic Zuni Sandstone Formation aquifer is composed of sandstone and the well is currently active. This type of aquifer is rated as having a LOW susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
OUM-Other Land Use Source - Medium Risk	MED	109	MED
WST-Storage Tanks for PWS	NONE	867	NONE

The cumulative risk associated with these PSOCs is LOW.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	No
2. Is the casing exposed to surface water runoff?	No
3. Is the well site subject to flooding?	No
4. Is the upper termination of the well located outside a secured area?	No
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is LOW.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a LOW susceptibility to contamination.

 

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

 

Well Name:  Aanzac # 5                    Well Number: W0007

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 1065.0 feet and is completed in the Jurassic Zuni Sandstone Formation aquifer between the screened intervals of 100.0 and 1030.0 feet. The Jurassic Zuni Sandstone Formation aquifer is composed of sandstone and the well is currently active. This type of aquifer is rated as having a LOW susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
OUM-Other Land Use Source - Medium Risk	MED	108	MED
WST-Storage Tanks for PWS	NONE	803	NONE

The cumulative risk associated with these PSOCs is LOW.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	No
2. Is the casing exposed to surface water runoff?	Yes
3. Is the well site subject to flooding?	Yes
4. Is the upper termination of the well located outside a secured area?	Yes
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is HIGH.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a MEDIUM susceptibility to contamination.

Water Supply System Name:  Acoma Pueblo/Main

PWS ID:  063501001

 

Well Name:  Aanzac # 6                    Well Number: W0008

The well depicted below was completed on an unknown date. The well was drilled to a total depth of 1075.0 feet and is completed in the Jurassic Zuni Sandstone Formation aquifer between the screened intervals of 885.0 and 1065.0 feet. The Jurassic Zuni Sandstone Formation aquifer is composed of sandstone and the well is currently active. This type of aquifer is rated as having a LOW susceptibility to contamination.

An inventory of potential sources of contamination  (PSOC) within a 1/4 mile (1,320 feet) radius of the well reveals the following contaminant sources and their relative risk to the well:

Potential Source of Contamination (PSOC) Description	PSOC Risk	Distance From Water Source (ft)	Overall Risk
CTP-Chlorine Treatment for Water Supply Well	NONE	28	NONE
SET-Single Family Septic System	MED	512	MED
SET-Single Family Septic System	MED	658	MED
SET-Single Family Septic System	MED	862	MED
DWW-Domestic Water Well	MED	910	MED
SET-Single Family Septic System	MED	1125	LOW
SET-Single Family Septic System	MED	1146	LOW
OPH-Other Point Source - High Risk	HIGH	1238	MED

The cumulative risk associated with these PSOCs is MEDIUM.

The overall risk posed by a particular PSOC is based on the type of PSOC (1=low, 2-medium, 3=high), and the risk due to the proximity of the PSOC to the water source.  The distance factor is considered high (3) if the PSOC is within 810 feet, medium (2) if from 811 feet to 1070 feet, and low (1) if from 1070 feet to 1320 feet. These two components (type and distance) are summed to give the overall risk posed by the individual PSOC (low=2, 3; medium=4, 5; high=6). To determine the cumulative risk to the water source posed by all of the PSOCs, the overall risk from each source is summed and a scale is applied.  If the sum is 0 to 6, the risk is low; a sum of 7 to 12 yields a medium risk; and a sum greater than 12 represents a high risk of contamination of the water source.

Source Integrity Parameter	Assessment
1. Is the top of the screened interval within 100 feet of ground level?	No
2. Is the casing exposed to surface water runoff?	No
3. Is the well site subject to flooding?	No
4. Is the upper termination of the well located outside a secured area?	Yes
5. Is the upper termination of the well located in a pit?	No

Based on the questions above, the Source Integrity Susceptibility Score is MEDIUM.

Based on the character of the hydrogeologic factors around the setting; the nature of these potential contaminant sources, and their proximity to the well; and the physical integrity of the well; this well has been determined to have a MEDIUM susceptibility to contamination.

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