xvEPA
United States
Environmental Protection
l Agency
2
3
4 GROUND WATER RULE
6 CORRECTIVE ACTIONS GUIDANCE MANUAL (DRAFT)
7
8
9 June 2008
10 Public Review Draft
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1 DISCLAIMER
2
O
4 This manual provides guidance in meeting corrective actions of the Ground Water Rule
5 (GWR). Corrective actions are an important part of helping water systems protect public health.
6
7 The statutory provisions and U.S. Environmental Protection Agency (EPA) regulations
8 described in this document contain legally binding requirements. This guidance is not a
9 substitute for applicable legal requirements, nor is it a regulation itself. Thus, it does not impose
10 legally-binding requirements on any party, including EPA, States, or the regulated community.
11 While EPA has made every effort to ensure the accuracy of the discussion in this guidance, the
12 obligations of the regulated community are determined by statutes, regulations, or other legally
13 binding requirements. In the event of a conflict between the discussion in this document and any
14 statute or regulation, the statute and regulation, not this document, would be controlling.
15
16 Interested parties are free to raise questions and objections to the guidance and the
17 appropriateness of using it in a particular situation.
18
19 Although this manual describes suggestions for complying with GWR requirements, the
20 guidance presented here may not be appropriate for all situations, and alternative approaches
21 may provide satisfactory performance.
22
23 Mention of trade names or commercial products does not constitute an EPA endorsement
24 or recommendation for use.
25
26 Comments regarding this document should be addressed to:
27
28 Michael Finn
29 U. S. EPA Office of Ground Water and Drinking Water
30 Standards and Risk Management Division
31 1200 Pennsylvania Avenue, N.W. 4607M
32 Washington, DC 20460
33 Finn.Michael@epa.gov
34 202-564-5261
35 202-564-3767 (facsimile)
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1 ACKNOWLEDGMENTS
2
O
4
5
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1 CONTENTS
2
O
4 Exhibits vi
5 Acronyms vii
6
7 1. Introduction to the Ground Water Rule Corrective Action Guidance Document 1-1
8 1.1 The Ground Water Rule (GWR) 1-1
9 1.2 Overview of the Corrective Action Process under the GWR 1-2
10 1.3 Requirements for States and PWSs Related to Corrective Actions in Response to
11 Significant Deficiencies and Fecal Indicator Positives 1-3
12 1.3.1 State Requirements 1-3
13 1.3.2 PWS Requirements 1-4
14 1.4 Goal and Organization of the Guidance Manual 1-5
15
16
17 2. Correcting Significant Deficiencies 2-1
18 2.1 Identifying Significant Deficiencies 2-2
19 2.1.1 Sanitary Surveys 2-2
20 2.1.2 Other Ways of Identifying Significant Deficiencies 2-3
21 2.2 Source Deficiencies 2-3
22 2.2.1 Examples of Significant Deficiencies 2-3
23 2.2.2 Identifying Corrective Actions 2-3
24 2.2.3 Additional Information and Resources 2-4
25 2.3 Treatment Deficiencies 2-4
26 2.3.1 Examples of Significant Deficiencies 2-4
27 2.3.2 Identifying Corrective Actions 2-4
28 2.3.3 Additional Information and Resources 2-5
29 2.4 Distribution System Deficiencies 2-5
30 2.4.1 Biofilm Control 2-5
31 2.4.2 Cross-Connection Control 2-7
32 2.4.2.1 Existing Requirements 2-8
33 2.4.2.2 Choosing a Backflow Preventer 2-9
34 2.4.2.3 Installing and Testing Backflow Preventers 2-10
35 2.4.2.4 Cross-Connection Control and Backflow Prevention Programs 2-10
36 2.4.3 Examples of Significant Deficiencies 2-10
37 2.4.4 Identifying Corrective Actions 2-11
38 2.4.5 Additional Information and Resources 2-11
39 2.5 Finished Water Storage 2-12
40 2.5.1 Correcting Defective Vents 2-13
41 2.5.2 Correcting Inadequate Access Hatches 2-13
42 2.5.3 Correcting Insufficient Overflows 2-14
43 2.5.4 Examples of Significant Deficiencies 2-14
44 2.5.5 Identifying Corrective Actions 2-14
45 2.5.6 Additional Information and Resources 2-15
46 2.6 Pumps 2-15
47 2.6.1 Examples of Significant Deficiencies 2-16
48 2.6.2 Identifying Corrective Actions 2-16
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1 2.6.3 Additional Information and Resources 2-16
2 2.7 Monitoring, Reporting and Data Verification 2-16
3 2.7.1 Examples of Significant Deficiencies 2-17
4 2.7.2 Identifying Corrective Actions 2-17
5 2.7.3 Additional Information and Resources 2-17
6 2.8 System Management and Operations 2-17
7 2.8.1 Identifying Financial Resources 2-18
8 2.8.2 Security Measures 2-19
9 2.8.3 Examples of Significant Deficiencies 2-19
10 2.8.4 Identifying Corrective Actions 2-20
11 2.8.5 Additional Information and Resources 2-20
12 2.9 Operator Compliance with Certification Requirements 2-20
13 2.9.1 Examples of Significant Deficiencies 2-21
14 2.9.2 Identifying Corrective Actions 2-21
15 2.9.3 Additional Information and Resources 2-21
16
17 3. Eliminating Sources of Contamination 3-1
18 3.1 Source Water Rehabilitation 3-1
19 3.1.1 Identifying Contamination Causes 3-1
20 3.1.2 Preventing Contamination from an Abandoned Well 3-3
21 3.1.3 Remediating an Existing Well 3-3
22 3.1.3.1 Correcting Drainage Problems 3-6
23 3.1.3.2 Replacing a Sanitary Well Seal 3-7
24 3.1.3.2 Replacing a Sanitary Well Seal 3-7
25 3.1.3.3 Eliminating a Well Pit / Buried Well 3-9
26 3.1.3.4 Temporary Disinfection of Wells by Applying Shock Chlorination. 3-9
27 3.1.4 Minimizing Contamination after a Flood 3-9
28
29 4. Providing an Alternative Source of Drinking Water 4-1
30 4.1 Providing Bottled Water (Short Term) 4-1
31 4.2 Consolidating/Purchasing Water from Another Utility 4-2
32 4.3 Installing a New Well 4-2
33 4.3.1 Critical Factors in Well Construction 4-2
34 4.3.2 Types of Wells 4-4
35 4.3.2.1 Bored Wells 4-4
36 4.3.2.2 Driven Wells 4-4
37 4.3.2.3 Jetted Wells 4-5
38 4.3.2.4 Drilled Wells 4-5
39 4.3.3 Characteristics of Wells 4-9
40 4.3.3.1 Yields of Different Types of Wells 4-9
41 4.3.3.2 Sanitary Construction of Wells 4-10
42 4.3.3.3 Grouting Requirements 4-11
43 4.3.3.4 Well Screens 4-12
44 4.3.3.5 Well Development 4-13
45 4.3.3.6 Testing Wells for Yield and Drawdown 4-14
46 4.3.4 Disinfect! on of Newly Constructed Wells 4-15
47 4.4 Switching to a Surface Water Source 4-16
48 4.4.1 Requirements for Treating Surface Water 4-16
49 4.4.2 Selecting a Surface Water Source 4-17
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1
2 5. Installing Treatment 5-1
3 5.1 Chemical Disinfection 5-3
4 5.1.1 Temporary Hypochlorination 5-4
5 5.1.2 Chlorine Gas 5-5
6 5.1.2.1 Background 5-5
7 5.1.2.2 SystemDesign 5-6
8 5.1.2.3 Operation and Maintenance 5-6
9 5.1.2.4 Advantages and Disadvantages 5-7
10 5.1.3 Hypochlorite 5-7
11 5.1.3.1 Background 5-8
12 5.1.3.2 SystemDesign 5-8
13 5.1.3.3 Operation and Maintenance 5-9
14 5.1.3.4 Advantages and Disadvantages 5-10
15 5.1.4 Chlorine Dioxide (C1O2) Disinfection 5-10
16 5.1.4.1 Background 5-10
17 5.1.4.2 SystemDesign 5-11
18 5.1.4.3 Operation and Maintenance 5-11
19 5.1.4.4 Advantages and Disadvantages 5-11
20 5.1.5 Ozone (O3) Disinfection 5-12
21 5.1.5.1 Background 5-12
22 5.1.5.2 Operation and Maintenance 5-13
23 5.1.5.3 Advantages and Disadvantages 5-13
24 5.2 UV Radiation Disinfection 5-14
25 5.2.1 Background 5-14
26 5.2.2 Inactivation Mechanism and Effectiveness 5-15
27 5.2.3 SystemDesign 5-15
28 5.2.4 Operation and Maintenance 5-16
29 5.2.5 Advantages and Disadvantages 5-17
30 5.3 Membrane Filtration Technologies 5-17
31 5.3.1 Background 5-18
32 5.3.2 SystemDesign 5-19
33 5.3.3 Operation and Maintenance 5-20
34 5.3.4 Advantages and Disadvantages 5-20
35 5.4 Additional Resources 5-21
36
37 6. References 6-1
38
39 Appendix A: Applications of Various Backflow Prevention Assemblies or Methods A-l
40
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1 EXHIBITS
2
3 Exhibit 1.1 Overview of Corrective Action Process 1-3
4 Exhibit2.1 Typical Ground Storage Tank 2-12
5 Exhibit 2.2 Raised Sill Appropriate for a Hatch 2-14
6 Exhibit 3.1 Pump House and Well Appurtenances 3-4
7 Exhibit 3.2 Submersible Pump with Pitless Adapter 3-5
8 Exhibit 3.3 Example of Correcting Drainage Problems 3-7
9 Exhibit 3.4 Sanitary Well Seal with Expandable Gasket 3-9
10 Exhibit 3.5 Overlapping Exterior Well Seal 3-9
11 Exhibit 3.6 Quantities of Calcium Hypochlorite, 70% for (Rows A) and Liquid Chlorine
12 Bleach*, 5.25 % (Rows B) to Provide a Chlorine Dosage of at Least lOOmg/L 3-9
13 Exhibit 4.1 Well Construction and Condition 4-3
14 Exhibit 4.2 Ten State Standards (2007) Recommendations for Casing 4-3
15 Exhibit 4.3 Drilled Well with Submersible Pump 4-7
16 Exhibit 4.4 Typical Wellhead Design for Submersible Pumps 4-8
17 Exhibit 4.5 Suitability of Well Construction Methods with Different Geological Conditions 4-10
18 Exhibit 5.1 CT Values for Inactivation of Viruses by Free Chlorine (mg-min/L) 5-4
19 Exhibit 5.2 CT Values (mg-min/L) for Inactivation of Viruses 1 by Chlorine Dioxide for pH 6 to
20 9 5-10
21 Exhibit 5.3 CT Values (mg of O3-min/L) for Virus Inactivation by Ozone 5-13
22 Exhibit 5.4 UVDose Requirements for Virus Removal (mJ/cm2) 5-15
23 Exhibit 5.5 Particle Size Removal for Various Membrane Technologies 5-18
24 Exhibit 5.6 Schematic of a Typical RO/NF Treatment System 5-19
25
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ug/L
2D
AG
AOC
AVB
AWWA
AwwaRF
BAT
BL
BMP
CCR
CFR
CT
CWS
DBF
D/DBPR
DCDC
DCIAV
DCV
DEP
DNA
EPA
EPS
FDA
GWR
GWS
GWUDI
HAA
HB
HPC
HSA
HTH
IBWA
ICR
IESWTR
LT1
LT2
MCL
ACRONYMS
micrograms per liter
Twice the Diameter
Air Gap
Assimilable Organic Carbon
Atmospheric Vacuum Breaker
American Water Works Association
American Water Works Association Research Foundation
Best Available Technology
Barometric Loop
Best Management Practice
Consumer Confidence Reports
Code of Federal Regulations
Concentration of Residual Disinfectant (in mg/L) multiplied by Time of Water
Contact (Detention Time) (in minutes)
Community Water System
Disinfection Byproduct
Disinfectants/Disinfection Byproducts Rule
Double Check Detector Check
Double Check Valve with Intermediate Atmospheric Vent
Double Check Valve
Department of Environmental Protection
Deoxyribonucleic Acid
United States Environmental Protection Agency
Extracellular Polysaccharides
United States Food and Drug Administration
Ground Water Rule
Public Water Systems that are subject to the requirements of the Ground
Water Rule (includes PWSs that also deliver surface water and/or GWUDI)
Ground Water Under the Direct Influence of Surface Water
Haloacetic Acid
Hose Bib Vacuum Breaker
Heterotrophic Plate Count
Hydrogeologic Sensitivity Assessment
High-test Hypochlorite
International Bottled Water Association
Information Collection Rule
Interim Enhanced Surface Water Treatment Rule
Long Term 1 Enhanced Surface Water Treatment Rule
Long Term 2 Enhanced Surface Water Treatment Rule
Maximum Contaminant Level
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MF
mg/L
MWCO
NCWS
NOM
NDPES
NF
O&M
PVB
PVC
PWS
RCRA
RDC
RO
RPBA
SDWIS
SMCL
SRF
SWTR
TCR
THM
TOC
TOX
UF
UFTREEO
UIC
USGS
UV
UVT
Microfiltration
milligrams per liter
Molecular Weight Cut Off
Non-community Water Systems
Natural Organic Matter
National Pollutant Discharge Elimination System
Nanofiltration
Operation and Maintenance
Pressure Vacuum Breaker
Polyvinyl Chloride
Public Water System
Resource Conservation and Recovery Act
Residential Dual Check
Reverse Osmosis
Reduced Pressure Principle Blackflow Prevention Assembly
Safe Drinking Water Information System - Federal Version
Secondary Maximum Contaminant Level
State Revolving Fund
Surface Water Treatment Rule
Total Coliform Rule
Trihalomethane
Total Organic Carbon
Total Organic Halogen
Ultrafiltration
University of Florida Training, Research, and Education for Environmental
Occupations
Underground Injection Control
United States Geological Survey
Ultraviolet
UV Transmittance
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1 1. Introduction to the Ground Water Rule Corrective Action Guidance
2 Document
o
4
5 The purpose of this guidance manual is to assist States and Public Water Systems
6 (PWSs)1 to select and implement corrective actions in response to significant deficiencies
7 identified during sanitary surveys or in response to fecal contamination of source water as
8 required under the Ground Water Rule (GWR). Other important aspects of the GWR related to
9 corrective actions are discussed more fully in other guidance manuals, such as:
10
11 The Consecutive Systems Guidance Manual for the Ground Water Rule (USEPA
12 2007b)
13
14 The Source Water Monitoring Guidance Manual (USEPA 2007c)
15
16 The Ground Water Rule Sanitary Survey Guidance Manual (to be published)
17
18 This introduction provides an overview of the portions of the GWR that relate
19 specifically to performing corrective actions.
20
21
22 1.1 The Ground Water Rule (GWR)
23
24 The GWR was signed by the United States Environmental Protection Agency (EPA)
25 Administrator on October 11, 2006 and was published in the Federal Register on November 8,
26 2006 (71FR65574). The primary purpose of the GWR is to provide for increased protection
27 against microbial pathogens in PWSs that use ground water as their source.
28
29 PWSs that are subject to the requirements of the GWR include systems that use only
30 ground water sources, "mixed systems" that use both ground and surface water sources, and
31 wholesale and consecutive systems that serve ground water2.
32
33 The GWR does not apply to "subpart H" systems that combine all of their ground water
34 with surface water prior to treatment and those systems identified as ground water under the
35 direct influence of surface water (GWUDI). The GWR applies to all types of PWSs: community
36 water systems (CWSs), non-transient non-community water systems, and transient non-
37 community water systems.
38
39 EPA has estimated that approximately 147,330 PWSs in the United States serving over
40 114 million people are subject to the requirements of the GWR based on data from the Safe
41 Drinking Water Information System - Federal Version (SDWIS) (USEPA, 2006).
42
1 PWSs are systems that have at least 15 service connections, or regularly serve at least 25 individuals daily at least
60 days out of the year.
2 These systems are referred to as Ground Water Systems (GWSs) throughout this guidance document.
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1 The GWR established a risk-targeting approach to identify Ground Water Systems
2 (GWSs) subject to the rule that may pose a risk of exposure to microbial pathogens to customers.
3 The key provisions of the risk-targeting approach of the GWR are:
4
5 Periodic sanitary surveys of Ground Water Systems (GWSs) focusing on eight critical
6 elements to identify any significant deficiencies that must be addressed through
7 corrective action. States must complete the first of these periodic sanitary surveys by
8 December 31, 2012 for most CWSs and by December 31, 2014 for CWSs with a
9 history of outstanding performance and for all non-community water systems
10 (NCWSs) (40 CRF 141.401).
11
12 Triggered source water monitoring of GWSs that have a total coliform positive of a
13 routine sample in the distribution system under the Total Coliform Rule (TCR) if that
14 GWS does not currently provide treatment that achieves at least 99.99 percent (4-log)
15 inactivation or removal of viruses. Triggered source water monitoring tests for the
16 presence of a microbial pathogen indicator (E. coli, enterococci, or coliphage) as
17 required by the State. A GWS that has microbial pathogen indicator positive
18 identified in the source water may be required by the State to take immediate
19 corrective action or, if not so required, must take five additional source water samples
20 and undertake corrective action if any of those additional samples are positive (40
21 CRF 141.402(a)).
22
23 Assessment source water monitoring may also be required by a State as a
24 complement to triggered monitoring. A State has the option to require systems, at
25 any time, to conduct source water assessment monitoring for fecal indicators to help
26 identify high risk systems. Hydrogeologic sensitivity assessments (HSAs) can be
27 used as an optional tool to identify those high risk systems for assessment source
28 water monitoring (40 CFR 141.402(b)).
29
30 Compliance monitoring for GWSs that currently disinfect to ensure that the treatment
31 technology installed reliably achieves at least 99.99 percent (4-log) inactivation or
32 removal of viruses (40 CFR 141.403(b)).
33
34
35 1.2 Overview of the Corrective Action Process under the GWR
36
37 Under §141.403(a) the GWR, systems must implement a corrective action if one or more
38 significant deficiencies are identified by the State, or if a fecal indicator positive result is
39 detected in a source water sample collected under §141.402(a)(5) or if directed by the State.
40
41
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1
2
Exhibit 1.1 Overview of Corrective Action Process
4
5
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Pathl
Source
Water
Monitoring
State Requires
Corrective Action
Fecal Indicator
Positive Sample (from
1 of 5 additional
samples)
Path 2
Sanitary
Survey
PathS
Other State
Oversight
System
Required to
Take
Corrective
Action
State Identifies
Significant Deficiency
Corrective actions performed under the GWR include one or more of the following
alternatives:
Correct all significant deficiencies;
Eliminate the source of contamination;
Provide an alternate source of water; and
Provide treatment which reliably achieves 99.99 percent (4-log) inactivation or
removal of viruses.
The following briefly summarizes the requirements related to corrective actions that
States and PWSs must take in response to the identification of significant deficiencies or fecal
indicator positives.
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1 1.3 Requirements for States and PWSs Related to Corrective Actions in Response
2 to Significant Deficiencies and Fecal Indicator Positives
3
4
5 1.3.1 State Requirements
6
7 The GWR requires States to provide written notice to the PWS describing all significant
8 deficiencies (i.e., those that require corrective action) identified. The notice may be provided on-
9 site at the time the significant deficiency is identified or it may be sent to the PWS within 30
10 days of identifying the significant deficiency.
11
12 In the cases of either the identification of significant deficiencies or the determination of
13 a fecal indicator positive in source water monitoring, the State may specify the corrective actions
14 and deadlines to the affected GWS, or it may work with the affected GWS to determine an
15 appropriate corrective action plan. The State must approve the corrective action plan and
16 schedule (and must also approve any subsequent modifications to it). The State must also verify
17 corrective actions have been completed through written confirmation or a site visit within 30
18 days after the PWS has reported to the State that the corrective action has been completed.
19
20
21 1.3.2 PWS Requirements
22
23 Within 30 days of receiving written notice from the State of a significant deficiency or
24 written notice from a laboratory of a fecal-indicator positive, the GWS must consult with the
25 State regarding the appropriate corrective action. In some cases, the system may be directed by
26 the State to implement a specific corrective action.
27
28 If the State does not specify a corrective action to be taken by the GWS, then within 120
29 days (or earlier if directed by the State) of receiving written notice from the State of a significant
30 deficiency or written notice from a laboratory of a fecal indicator positive, the GWS must either
31 have completed the appropriate corrective action or be in compliance with a State-approved
32 corrective action plan and schedule.
33
34 The GWS must notify the State that a required corrective action has been completed
35 within 30 days of completion.
36
37 Also, in addition to other public notification requirements under the GWR, community
38 GWSs must provide a special notice to the public of any significant deficiencies uncorrected at
39 the time of the Consumer Confidence Report (CCR) or any fecal indicator positives, and
40 continue to inform the public annually until the significant deficiency or the fecal contamination
41 has been corrected in accordance with the State approved corrective action plan.
42
43 CCRs apply only to community GWSs. Non-community GWSs must provide notice to
44 the public regarding any significant deficiency that has not been corrected within 12 months.
45 Non-community GWSs must repeat notification annually until the significant deficiency is
46 corrected.
47
48
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1 1.4 Goal and Organization of the Guidance Manual
2
3 The next four chapters of this guidance document provide detailed information on the
4 four different general categories of corrective actions that may be required under the GWR for
5 systems that States have identified a significant deficiency.
6
7 Chapter 2 - Correcting Significant Deficiencies
8
9 Chapter 3 - Eliminating Sources of Contamination
10
11 Chapter 4 - Providing an Alternate Source of Drinking Water
12
13 Chapter 5 - Installing Treatment
14
15 The final chapter, Chapter 6, contains a list of references cited within the guidance
16 manual.
17
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1 2. Correcting Significant Deficiencies
2
3
4 The GWR requires States to conduct periodic sanitary surveys at all GWSs, and to
5 identify significant deficiencies during those surveys. Sanitary surveys include reviewing PWS
6 records and monitoring data as well as an onsite evaluation to identify both minor and significant
7 deficiencies. The GWR requires that significant deficiencies identified during sanitary surveys,
8 or during other State field visits or reviews, must be addressed through corrective action.
9
10 Significant deficiencies are not explicitly defined or specified in the final GWR.
11 However, 40 CFR 142.16 of the GWR indicates that significant deficiencies would include,
12 though are not limited to, defects in design, operation, or maintenance, or a failure or
13 malfunction of the sources, treatment, storage, or distribution system that the State determines to
14 be causing, or has the potential for causing, the introduction of contamination into the water
15 delivered to consumers. States are required to define and describe in its primacy package at least
16 one specific significant deficiency in each of the eight elements that 40 CFR 142.16 specifies
17 must be included in sanitary surveys conducted under the GWR:
18
19 1. Source,
20
21 2. Treatment,
22
23 3. Distribution system,
24
25 4. Finished water storage,
26
27 5. Pumps, pump facilities, and controls,
28
29 6. Monitoring, reporting, and data verification,
30
31 7. System management and operation, and
32
33 8. Operator compliance with State requirements.
34
35 This chapter discusses the eight different elements of a sanitary survey and some
36 common deficiencies that could be among those considered to be significant deficiencies. It also
37 addresses what States and PWSs should do when a significant deficiency is identified.
38 Correcting significant deficiencies can involve a wide range of technical or managerial changes
39 in the PWS, with a wide range of resource requirements.
40
41 The corrective actions that are proposed in this manual vary from actions that can easily
42 be completed to those that will require a significant amount of time and effort on the part of the
43 water system and the state. In order to ensure public health protection while also allowing for
44 the time needed to design and implement the optimal long-term solution, the State should
45 consider creating a two-phased corrective action if the GWS needs more than 6 monthneeds an
46 extended period of time s to complete the corrective action. The first phase of the corrective
47 action would be designed for the short-term to protect public health while providing the system
48 with the time to implement a permanent solution that finally completes the corrective action.
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1 Throughout this manual, you will see short-term and temporary solutions (providing bottled
2 water, interim disinfection, etc.) as well as long term solutions (constructing a new well).
3
4 EPA expects State drinking water programs to draw on their extensive experience to
5 develop specific criteria for determining which deficiencies are significant and how to correct
6 them in particular cases. This may include the State specifying the corrective action to the PWS
7 or working with the PWS to determine how to correct a particular significant deficiency
8 identified in its sanitary survey. Either way, it is critical that the GWS consult with the State to
9 identify an appropriate corrective action.
10
11
12 2.1 Identifying Significant Deficiencies
13
14 As part of a State's primacy package under the GWR, the State must describe the
15 approach it will use to determine if a deficiency is significant. Based on this approach, States
16 will decide on a case-by-case basis whether an identified deficiency is a significant deficiency.
17 There is a wide range of risks associated with significant deficiencies, ranging from those with a
18 small, but not insignificant likelihood of introducing microbial contamination to the finished
19 water, to those where the continued unaltered operation of the system poses a serious imminent
20 health threat to the population. The GWR requires all deficiencies identified by the State as
21 "significant" to be corrected by the water system. States, therefore, will need to establish
22 procedures for inspectors to use to determine the point where deficiencies become "significant."
23
24
25 2.1.1 Sanitary Surveys
26
27 Sanitary surveys have been conducted by staff or authorized agents of State drinking
28 water programs for decades. Sanitary surveys provide an opportunity for State drinking water
29 officials, or approved third party inspectors, to visit the water system and educate operators
30 about proper monitoring and sampling procedures, provide technical assistance, and inform them
31 of any changes in regulations. At the same time, sanitary surveys are driven by compliance with
32 existing regulations and by efforts to provide public health protection. EPA believes that
33 periodic sanitary surveys, along with appropriate corrective measures, are indispensable for
34 assuring the long-term safety and quality of drinking water. Currently, all States, except for one,
35 conduct sanitary surveys.
36
37 A sound sanitary survey program is an essential element of an effective State drinking
38 water program for PWSs. As required by the GWR, systems must provide all of necessary
39 information and assistance requested from States for conducting sanitary surveys. The GWR
40 requires States to conduct sanitary surveys of ground water CWSs every three years (every five
41 years for CWSs that meet performance criteria) and of ground water NCWSs every five years.
42 States are required to complete the initial sanitary survey cycle by December 31, 2012 for CWSs,
43 except those that meet performance criteria (e.g., 4-log treatment or outstanding performance and
44 no TCR violations), and December 31, 2014 for all NCWSs and CWSs that meet performance
45 criteria. States may conduct more frequent sanitary survey cycles for any GWS as appropriate.
46
47 The EPA Guidance Manual for Conducting Sanitary Surveys of PWSs Served Solely by
48 Ground Water Sources (to be published) contains information on how to perform an onsite
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1 inspection and sanitary survey and can be referenced for guidance on the specifics on conducting
2 sanitary surveys under the GWR.
3
4
5 2.1.2 Other Ways of Identifying Significant Deficiencies
6
7 While significant deficiencies are often identified during sanitary surveys, other
8 situations may also bring them to the attention of regulators. If a water system reports higher
9 levels of contaminants than normal, even if there has not been a violation, the regulator may take
10 the preventative step of visiting the system to try and identify the source of the contamination.
11 When customers complain to regulators of low water pressure or colored water at their water
12 system, the regulator may follow up with a visit to the system to help identify or investigate the
13 problem. Complaints of illness that may be attributable to waterborne pathogens can also prompt
14 a visit by regulators. It is not unusual for deficiencies to be found during such site visits.
15 Sometimes it's a coincidence that a significant deficiency is found; a regulator may be at the
16 water system for another purpose and notice a significant deficiency during his or her visit.
17
18
19 2.2 Source Deficiencies
20
21 A water supply's ground water source can contain contaminants, pathogens, and
22 particles. Preventing source water contamination is an effective way to prevent contaminants
23 from reaching consumers. Source water protection also helps prevent additional, potentially
24 more costly treatment from being necessary for the removal of contaminants. During a sanitary
25 survey, the major components of the well or spring are reviewed to determine reliability, quality,
26 quantity, and vulnerability. The potential for degradation of source water quality is also
27 evaluated.
28
29
30 2.2.1 Examples of Significant Deficiencies
31
32 Well does not meet state-specified setback distances from hazards.
33
34 Well is improperly constructed.
35
36 Well does not have a sanitary seal.
37
38 Spring box is poorly constructed and/or subject to flooding.
39
40
41 2.2.2 Identifying Corrective Actions
42
43 Remove hazards to well or relocate well.
44
45 Address components of well that are not properly constructed (e.g., height of casing
46 above ground, screened vent, grouting).
47
48 Replace or supplement existing well cover with cap that provides a sanitary seal.
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2
3 2.2.3 Additional Information and Resources1
4
5 Bloetscher, F., A. Muniz, J. Largey. 2007. Siting, Drilling, and Construction of Water Supply
6 Wells. AWWA. Denver, CO.
7
8 Recommended Standards for Water Works. 2007. Great Lakes-Upper Mississippi River Board of
9 State and Provincial Public Health and Environmental Managers.
10 http://10statestandards.com/waterstandards.html
11
12
13 2.3 Treatment Deficiencies
14
15 Water treatment facilities are the primary means of preventing unacceptable drinking
16 water quality from being delivered for public consumption. The treatment facilities and
17 processes should be capable of removing, sequestering, or inactivating physical, chemical, and
18 biological impurities in the source water. Water treatment plants should be designed, operated,
19 maintained, and managed in a way that minimizes existing or potential sanitary risks.
20
21 During a sanitary survey, the treatment facilities and processes are evaluated to determine
22 their ability to meet regulatory requirements and to provide an adequate supply of safe drinking
23 water at all times, including periods of high water demand. The distinct parts of the treatment
24 process, including but not limited to disinfection, chemical feed systems, hydraulics, and
25 controls, are inspected. Features of the water treatment process that may pose a sanitary risk,
26 such as inadequate treatment, monitoring, or maintenance, lack of reliability, and cross
27 connections are also identified.
28
29
30 2.3.1 Examples of Significant Deficiencies
31
32 Inadequate application of treatment chemicals.
33
34 Inadequate disinfection contact time.
35
36 No provision to prevent chemical overfeeds.
37
38 Required treatment can be bypassed.
39
40
41 2.3.2 Identifying Corrective Actions
42
43 Written operations and maintenance procedures for water treatment.
44
45 Supplement disinfectant contact time (e.g., additional storage, slower flows, baffling).
1 Many states have well standards that need to be met for newly installed wells. Water systems should make sure
any actions they take to remediate or install wells are consistent with their state's requirements.
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1
2 Add controls to eliminate the possibility of chemical overfeeds (e.g., check valves,
3 day tanks).
4
5 Physically disconnect pipe bypassing treatment.
6
7
8 2.3.3 Additional Information and Resources
9
10 AWWA. 2006. Water Chlorination and Chloramination Practices and Principles (M20), Second
11 Edition. Denver, CO.
12
13 MWH. 2005. Water Treatment: Principles and Design, Second Edition. John Wiley & Sons.
14
15 Recommended Standards for Water Works. 2007. Great Lakes-Upper Mississippi River Board of
16 State and Provincial Public Health and Environmental Managers.
17 http://10statestandards.com/waterstandards.html
18
19 USEPA. 2006. Ultraviolet Disinfection Guidance Manual for the Long Term 2 Enhanced
20 Surface Water Treatment Rule. Office of Water. EPA 815-R-06-007.
21
22 USEPA. 2005. Membrane Filtration Guidance Manual. Office of Water. EPA 815-R-06-009.
23
24
25 2.4 Distribution System Deficiencies
26
27 A well maintained and operated distribution system is an important barrier in protecting
28 water quality. During a sanitary survey, the surveyor would evaluate the condition (to the extent
29 possible) and maintenance of the distribution system.
30
31 All types of ground water systems face the challenge of the introduction of contaminants
32 into finished water in the distribution system. Seasonal ground water systems, in particular, can
33 be at risk. These systems shut down their distribution systems down for extended periods of
34 time before starting them up for the next season. During this period of shutdown, the pressure in
35 the pipe can lower below the pressure outside the pipe (making the distribution system subject to
36 intrusion or structural failure), suspended particulates in the stagnant water settle into pipe
37 sediments, and biofilm can rapidly develop. When the system starts back up, sudden flow
38 increases can cause accumulated biofilm, sediment, and tubercles to be released into the water
39 column. Seasonal systems should work with their state to determine operating procedures for
40 system shut down and start up that minimize the potential for contamination. This could be a
41 combination of disinfecting, flushing the system, and minimizing the magnitude of pressure
42 transients by slowing the rate of opening and closing valves (USEPA, 2006d).
43
44
45 2.4.1 Biofilm Control
46
47 Biofilms may cause total coliform detections, harbor other pathogens, or cause aesthetic
48 problems in water delivered to customers. It is therefore imperative to control biofilm growth in
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1 wells and distribution systems in order to maintain a potable water supply. Biofilms decrease
2 chlorine residuals that can lead to an increase in the levels of coliform counts. Factors that are
3 known to influence biological growth include the following (USEPA, 1992):
4
5 Pipe corrosion,
6
7 Availability of nutrients (organic carbon, nitrogen, and phosphorus),
8
9 Temperature,
10
11 pH,
12
13 Accumul ati on of organi c materi al s,
14
15 Dissolved oxygen supply, and
16
17 Decreased flow velocity.
18
19 Biofilms are made up of microoganisms that attach to pipe surfaces, nourish themselves
20 with nutrients in the water, and finally slough off into the water. Sheer forces generated by fluid
21 velocity and possible effects of disinfectants on extracellular polysaccharides (EPS) anchor the
22 bacteria to the pipe surface (USEPA, 1992). Biomass is largely composed of heterotrophic
23 bacteria (Enterobacter doacae, Klebsiellapneumoniae, and Citrobacter freundii), and smaller
24 proportions of fungi (yeasts), and non-pathogenic protozoa (USEPA, 1992). Total coliforms,
25 which serve as the primary microbial indicator of drinking water quality, are heterotrophic
26 bacteria.
27
28 It is difficult to definitively distinguish between coliforms associated with biofilms and
29 those from other sources. The major indication of biofilm growth is an increase in coliform
30 bacteria. Other factors include the following (USEPA, 1992):
31
32 Increased turbidity,
33
34 Periods of low chlorine residuals,
35
36 Coliform persistence in the presence of a disinfectant residual,
37
38 Changes in the number of non-coliform background bacteria in the membrane filter
39 total coliform test,
40
41 Recent backflow and/or cross-connection events, and
42
43 Warmer temperatures.
44
45 Detection of biofilm is best done through a careful examination of the well and/or pipe
46 distribution system; however, this is costly and burdensome. Measurement of nutrient levels
47 (e.g., a decreasing level of assimilable organic carbon (AOC) throughout the distribution system)
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1 and periodic sampling to assess problems caused by rainfall or increased temperature are good
2 alternatives to monitoring for biofilm growth (USEPA, 1992).
3
4 The following preventive/control measures are suggested (USEPA, 1992):
5
6 Check for adequate free chlorine residual (> 1.5 mg/L).
7
8 Routinely flush out system as a sudden increase in flow can result in increased
9 biolfilm detachment.
10
11 Modify the pH level to 8-9.
12
13 Apply corrosion control chemicals (e.g., sodium silicate or phosphate-based
14 inhibitors that form a molecular layer on the pipe surface, protecting it from the water
15 thereby increasing the effectiveness of free chlorine for disinfection of biofilms on
16 iron pipes).
17
18 Provide a protective barrier between the water and pipe, such as corrosion-resistant
19 linings coating or paints.
20
21 Check for backflows/cross-connections.
22
23 Control nutrient levels by reducing AOC levels with the use of activated carbon or
24 mixed filters that trap organic contaminants.
25
26 Loop dead ends and low-flow areas within the pipe distribution system.
27
28 Replace corroded and tuberculated pipes.
29
30 Careful monitoring of coliform occurrence and maintenance of wells and distribution
31 systems can minimize growth of bacteria.
32
33
34 2.4.2 Cross-Connection Control
35
36 Another public health threat that can arise in the distribution system is contamination
37 introduced through cross-connections (see the Cross-Connection Control Manual (USEPA,
38 2003) for more information). A cross-connection is "any unprotected actual or potential
39 connection or structural arrangement between a public or a consumer's potable water system and
40 any other source or system through which it is possible to introduce into any part of the potable
41 system any used water, industrial fluids, gas, or substance other than the intended potable water
42 with which the system is supplied" (AWWA, 1990a). Cross-connections can also be
43 characterized as irrigation wells, other irrigation water supplies, or private wells.
44
45 Backflow refers to a reverse flow condition created by a difference in water pressures
46 that causes water to flow back into the distribution pipes of a potable water supply from any
47 source or sources other than an intended source (USEPA, 2000). Backflow can occur under two
48 different conditions. The first condition called backpressure exists when a potable system is
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1 connected to a non-potable supply operating under a higher pressure by means of a pump, boiler,
2 elevation difference, air or steam pressure, or other means (AWWA, 1990a). The second
3 condition that causes backflow occurs when there is negative or reduced pressure in the supply
4 piping (i.e., the distribution system's pressure is lower than atmospheric pressure) and is known
5 as backsiphonage (AWWA, 1990a).
6
7 Distribution systems can lose pressure and even experience a partial vacuum when water
8 is withdrawn at a very high rate, such as during fire fighting or when booster pumps are used.
9 Systems also lose pressure during events like main repairs and line breaks. If the system
10 pressure drops sufficiently, the direction of flow within portions of the system will reverse; if
11 there are cross-connections, contaminants can be siphoned into the distribution system (AWWA,
12 1990a). For example, fecal contamination can be introduced into the distribution system anytime
13 during a backpressure or backsiphonage event, if the PWS has a cross-connection with a source
14 containing fecal contamination.
15
16
17 2.4.2.1 Existing Requirements
18
19 All 50 States require cross-connection control through various means such as Plumbing
20 Codes, Health Codes or Environmental Protection Codes. The majority of States require systems
21 or individual localities to implement cross-connection control programs that uphold State
22 regulations; however, other States require individual customers to comply with State regulations
23 that are enforced by a public water supplier.
24
25 There are two methods commonly used to control or eliminate backflow hazards due to
26 cross-connections - physically eliminating the cross-connection or installing a backflow
27 preventer. Several States require systems to physically separate the cross-connections rather
28 than install a backflow prevention assembly (Florida DEP, 1996). Some States only allow
29 installation of a backflow prevention assembly when a physical separation is not possible.
30 Systems that physically separate the cross-connection should do so in a manner that the cross-
31 connection cannot be re-established. Additionally, systems should always check State
32 requirements before considering a backflow prevention assembly.
33
34 If a cross-connection is implicated as the significant deficiency or source of fecal
35 contamination entering the distribution system, a backflow preventer can be used to eliminate
36 further contamination from entering the distribution system. Backflow prevention used in
37 response to a contamination event can be an effective means of eliminating a source of
38 contamination.
39
40 Some jurisdictions regard a cross-connection as a significant deficiency with backflow
41 prevention as the proper corrective action. If the cross-connection is viewed as a significant
42 deficiency, the system is required to correct the significant deficiency as part of the GWR
43 sanitary survey requirements.
44
45
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1 2.4.2.2 Choosing a Backflow Preventer
2
3 Several types of backflow preventers exist; however, not all types are applicable for all
4 situations. Below is a list of the basic types of backflow preventers (USEPA, 1989).
5
6 Air gap (AG),
7
8 Barometric loop (BL),
9
10 Atmospheric vacuum breaker (AVB),
11
12 Pressure vacuum breaker (PVB),
13
14 Double check valve (DCV),
15
16 Reduced pressure principle backflow prevention assembly (RPBA), and
17
18 Double check valve with intermediate atmospheric vent (DCIAV).
19
20 Mechanical backflow preventers should be capable of being tested to determine
21 effectiveness. Several factors must be considered when choosing the right type of backflow
22 prevention assembly. These considerations include the following:
23
24 The degree of hazard protection needed;
25
26 The likelihood that backpressure may result; and
27
28 If the system wants to provide protection inside the customer's premises (isolation) or
29 at the service connection (containment).
30
31 Appendix A presents the applications of various backflow prevention
32 assemblies/methods. Systems deciding to provide backflow prevention against health hazards
33 should use only air gaps, PVBs, AVBs, or RPBAs. Among these, only air gaps and RPBAs
34 should be used to protect against high hazards. Although all backflow prevention assemblies
35 protect against backsiphonage, only AGs, DCVs, and RPBAs should be used to protect against
36 backpressure.
37
38 When choosing a backflow preventer, systems should keep in mind that isolation
39 provides protection within premises and containment devices prevent a contaminant from
40 leaving the premises. Backflow preventers that provide isolation are typically more expensive
41 than containment devices since multiple assemblies may be required for a single customer
42 (USEPA, 2003). Because isolation occurs within a customer's premises, devices can be easily
43 bypassed, eliminating the benefit of the backflow prevention assembly. Alternatively,
44 containment remains under the control of the system, and therefore bypassing is less of a
45 concern.
46
47
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1 2.4.2.3 Installing and Testing Backflow Preventers
2
3 Backflow prevention assemblies should only be installed by certified backflow
4 prevention assembly installers and only tested by backflow prevention assembly testers. There
5 are many organizations that provide training for backflow prevention assembly installers and
6 testers such as the following:
7
8 University of Florida Center for Training, Research & Education for Environmental
9 Occupations (UFTREEO);
10
11 American Water Works Association (AWWA); and
12
13 USC Foundation for Cross-Connection Control and Hydraulic Research.
14
15 A number of organizations including the UFTREEO Center, USC, and the American
16 Society of Sanitary Engineers (www.asse-plumbing.org) provide certification of backflow
17 prevention assembly installers and/or testers.
18
19
20 2.4.2.4 Cross-Connection Control and Backflow Prevention Programs
21
22 Cross-connection control and backflow prevention programs are commonly used as a
23 Best Management Practice (BMP) in many systems to prevent contamination from entering the
24 distribution system. Many States have requirements for cross-connection control and backflow
25 prevention programs for some or all systems or facilities. When a system intends to implement a
26 cross-connection control and backflow prevention program, it is essential to check the specific
27 State regulations to determine what elements may be required in a program. The minimum
28 recommended elements of a cross-connection control and backflow prevention program are as
29 follows (Voorhees, 1999):
30
31 Authority to implement the program (e.g., city ordinance);
32
33 Certification of backflow assembly testers;
34
35 Reporting and record keeping;
36
37 Public notification of backflow events; and
38
39 Authority to enforce the program.
40
41 Other potential elements could include approval of specific devices, specific testing
42 requirements, what types of premises are required to have protection, public education, and
43 others.
44
45
46 2.4.3 Examples of Significant Deficiencies
47
48 Negative pressures that could result in the entrance of contaminants.
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1
2 Inadequate disinfectant residual monitoring, when required.
3
4 Unprotected cross connections.
5
6
7 2.4.4 Identifying Corrective Actions
8
9 Corrective action plan for pressure monitoring and maintenance or capital
10 improvement plan.
11
12 Water quality monitoring plan or operator training.
13
14 Corrective action for cross connections and/or cross connection control program.
15
16
17 2.4.5 Additional Information and Resources
18
19 Asset Management: A Handbook for Small Water Systems Publication Number EPA 816-R-03-
20 016
21
22 American Water Works Association
23 (800)-926-6142
24 www. awwa. org
25
26 AWWA (American Water Works Association). 1995d. Water Transmission and Distribution.
27 Second edition. Denver, Colo.:
28
29 AWWA. Recommended Practice for Backflow Prevention and Cross Connection Control,
30 Manual of Water Supply Practice Ml4, (AWWA 2004)
31
32 Backflow Prevention Theory and Practice. University of Florida, Division of Continuing
33 Education, Center for Training Research and Education for Environmental Occupations.
34 Ritland, Robin L. 1990Kendall/ Hunt Publishing Company, Dubuque, Iowa.
35
36 Cross Connection Control Manual (USEPA, 2003b)
37
38 Recommended Standards for Water Works, 2007, Great Lakes-Upper Mississippi River Board of
39 State and Provincial Public Health and Environmental Managers.
40 http://10statestandards.com/waterstandards.html
41
42 Sacramento State University-Office of Water Programs
43 (916)278-6142
44 http://www.owp.csus.edu/training/onlinecourses.php
45
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
University of Florida, Division of Continuing Education, Center for Training Research and
Education for Environmental Occupations(TREEO Center)
(352)-392-9570
http://www.treeo.ufl.edu/
2.5 Finished Water Storage
Finished water storage facilities should be maintained and regularly inspected to ensure
that distributes water quality is maintained. During a sanitary survey, the surveyor would
evaluate the condition and maintenance of finished water storage facilities. Storage facilities are
designed to protect the quality of the finished water while allowing air to enter and escape as the
water level changes. They are also designed to allow overflow to occur should the pumps fail to
shut down as programmed. There are often penetrations in the tanks to allow access for cleaning
and for water level gauging devices. Exhibit 2.1 shows a typical ground storage tank. It is
important that the storage tank integrity be maintained to keep contaminants from entering.
Deficiencies related to a system's water storage facilities may cause water quality and health-
related problems for PWSs (NETA, 1998). Such deficiencies can be the result of infrequent
inspection or lack of manufacturer-recommended maintenance on the part of the PWS.
Exhibit 2.1 Typical Ground Storage Tank
Tank Materials and Components
Steel Concrete Wood
Source: (NETA, 1998)
25
26
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1 As stated earlier, deficiencies found at storage tanks are frequently associated with
2 insufficient maintenance. Vent screens and flexible sealing materials deteriorate over time and
3 steel eventually corrodes even when properly coated. Each of these problems can cause
4 openings for microbial contaminants to enter the finished water. Often when these defects are
5 found they have progressed to the point where they cannot be quickly and easily corrected in a
6 permanent manner. In these cases, temporary measures must be put in place to minimize public
7 health risk. For example, silicone caulking can sometimes be used to temporarily seal small
8 holes in steel. Noncorrodible screens can be obtained and held in place with stainless steel hose
9 clamps. To accomplish permanent corrective measures, it is advisable to obtain up-to-date
10 construction standards from the primacy agency and bring the storage facility into compliance
11 with those standards. This will often require the use of a licensed professional engineer and
12 submission of plans and specifications for State review and approval.
13
14
15 2.5.1 Correcting Defective Vents
16
17 Defective vents should be repaired or replaced according to the Ten States Standards
18 (2007) to prevent the entrance of surface water and rainwater and exclude birds, animals, and, as
19 much as possible, insects and dust. Ground level tanks should be corrected so that vents
20 terminate in an inverted U fashion (see Exhibit 2.1) with the opening 24-36 inches above the
21 roof or sod cover with a noncorrodible screen installed within the pipe at a location least
22 susceptible to vandalism. The vent should also be protected from ice formation. Vents should
23 not be replaced by overflows because a storage tank should have both a vent and an overflow
24 pipe; an overflow pipe is not a reliable way to ventilate a tank because the overflow pipe might
25 be in use at the same time that ventilation is needed. (Ten States Standards, 2007).
26
27
28 2.5.2 Correcting Inadequate Access Hatches
29
30 In some cases, the State may find defective access hatches that allow insects and dust to
31 enter the storage tank or allow the storage tank to be vandalized. As shown in Exhibit 2.2,
32 finished water storage areas should have access hatches designed to allow entry for cleaning and
33 maintenance.
34
35
June 2008 Ground Water Rule 2-13 Public Review Draft
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1 Exhibit 2.2 Raised Sill Appropriate for a Hatch
2
3
4
5
6 These hatches should be framed four to six inches above the surface of the roof and the
7 opening and be fitted with a solid watertight cover that overlaps the framed opening and extends
8 down the sides at least two inches. The system should also install hatches that are hinged on one
9 side, have a gasket to keep out insects and dust, and have a locking device to prevent vandalism.
10
11
12 2.5.3 Correcting Insufficient Overflows
13
14 Insufficient overflows may also pose a problem for PWSs. PWSs should ensure that all
15 finished water storage facilities have an overflow that is brought down to an elevation between
16 12 and 24 inches above the ground surface and discharges over a drainage structure or splash
17 pad. The PWSs needs to makes sure that the discharge point is visible and cannot be connected
18 to any waste water structure. The discharge pipe should also be screened with 24-mesh
19 noncorrodible screen (Ten States Standards, 2007).
20
21 2.5.4 Examples of Significant Deficiencies
22
23 Inadequate internal cleaning and maintenance of storage tanks.
24
25 Lack of screening of overflow pipes, drains or vents.
26
27 Storage tanks roofs or covers need repairs ( e.g. holes, hatch damage or improper
28 construction, failing floating cover).
29
30
31 2.5.5 Identifying Corrective Actions
32
33 Corrective action plan for cleaning and maintenance.
34
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1 Corrective action schedule for repairs.
2
3 Asset management or maintenance plan.
4
5
6 2.5.6 Additional Information and Resources
7
8 Asset Management: A Handbook for Small Water Systems Publication Number EPA 816-R-03-
9 016
10
11 American Water Works Association
12 (800)-926-6142
13 www.awwa.org
14
15 AWWA (American Water Works Association). 1987b. AWWA Standard for Factory-Coated
16 Bolted Steel Tanks for Water Storage. AWWA D103-87. Denver, Colo.: AWWA.
17
18 AWWA (American Water Works Association). 1995a. AWWA Standard for Circular
19 Prestressed Concrete Water Tanks with Circumferential Tendons, AWWA D115-95.
20 Denver,Colo: AWWA.
21
22 AWWA (American Water Works Association). 1995b. AWWA Standard for Wire- andStrand-
23 Wound Circular Prestressed-Concrete Water Tanks. AWWA Dl 10-95. Denver, Colo:
24 AWWA.
25
26 AWWA (American Water Works Association). 1996a. AWWA Standard for Flexible-Membrane
27 Lining and Floating-Cover Materials for Potable- Water Storage. AWWA D13 0. Denver,
28 Colo.: AWWA.
29
30 AWWA (American Water Works Association). 1996. AWWA Standard for Welded Steel Tanks
31 for Water Storage. AWWA D100-96. Denver, Colo.: AWWA.
32
33 AWWA (American Water Works Association). 1998. AWWA ManualM42Steel Water-
34 Storage Tanks. Denver, Colo.: AWWA.
35
36 Kirmeyer, G.J., L. Kirby, B.M. Murphy, P.P. Noran, K.D. Martel, T.W. Lund, J.L. Anderson,
37 and R. Medhurst. 1999. Maintaining and Operating Finished Water Storage Facilities.
38 Denver,Colo.: AWWA and AWWARF.
39
40 Recommended Standards for Water Works, 2007, Great Lakes-Upper Mississippi River Board of
41 State and Provincial Public Health and Environmental Managers.
42 http://10statestandards.com/waterstandards.html
43
44
45 2.6 Pumps
46
47 For many public water systems, pumps are a critical component of the distribution.
48 During a sanitary survey, the conditions of pumps/pump facilities and controls would be
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1 reviewed. The surveyor would evaluate the operation and maintenance as well as safety practices
2 to determine that water supply pumping facilities are reliable.
O
4
5 2.6.1 Examples of Significant Deficiencies
6
7 Lack of redundant pumps or emergency power at critical facilities.
8
9 Cross connections to auxiliary supplies or cooling water.
10
11 Lack of maintenance.
12
13
14 2.6.2 Identifying Corrective Actions
15
16 Corrective action plan for redundant pumps or emergency power.
17
18 Remove cross connection or install backflow protection.
19
20 Asset management or maintenance plan.
21
22
23 2.6.3 Additional Information and Resources
24
25 Asset Management: A Handbook for Small Water Systems Publication Number EPA 816-R-03-
26 016
27
28 American Water Works Association
29 (800)-926-6142
30 www.awwa.org
31
32 Recommended Standards for Water Works, 2007, Great Lakes-Upper Mississippi River Board of
33 State and Provincial Public Health and Environmental Managers.
34 http://10statestandards.com/waterstandards.html
35
36
37 2.7 Monitoring, Reporting and Data Verification
38
39 All PWSs are required to perform water quality monitoring to determine compliance with
40 NPDW standards. The constituents monitored and the monitoring frequency vary with system
41 size and source. Compliance with NPDW standards is based on self- monitoring and reporting
42 and the sanitary survey provides an opportunity to review these procedures.
43
44
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1 2.7.1 Examples of Significant Deficiencies
2
3 Failure to monitor water quality or treatment.
4
5 Failure to monitor water quality in accordance with required monitoring plans.
6
7 Failure to report water quality monitoring.
8
9 Operators are using improper procedures and/or methods when collecting samples or
10 conducting onsite analyses.
11
12
13 2.7.2 Identifying Corrective Actions
14
15 Monitoring plans or revisions to monitoring plans.
16
17 Training plan for system staff.
18
19 Contracts with certified laboratories.
20
21
22 2.7.3 Additional Information and Resources
23
24 The Standardized Monitoring Framework: A Quick Reference Guide Publication Number EPA
25 816-F-04-010. www.epa.gov/safewwater/regs.html
26
27 Lead and Copper Rule: A Quick Reference Guide, Publication Number EPA 816-F-04-009.
28 www. epa. gov/safewwater/regs .html
29
30 Analytical Methods for Drinking Water
31 http://www.epa.gov/safewater/methods/methods.html
32
33 EPA's Interactive Sampling Guide for Drinking Water System Operators Publication Number
34 EPA 816-C-06-001. http://yosemite.epa.gov/water/owrccatalog.nsf/
35
36 A Small System Guide to the Total Coliform Rule, Publication Number EPA 816-R01-017A.
37 http://yosemite.epa.gov/water/owrccatalog.nsf/
38
39
40 2.8 System Management and Operations
41
42 PWSs need access to technical managerial and financial resources to provide a reliable
43 supply of drinking water meeting State and federal standards and to maintain public health
44 protection. Smaller systems, many of which are groundwater systems, face unique challenges in
45 providing drinking that meets standards and in operating and maintaining treatment and
46 distribution systems.
47
48
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1 2.8.1 Identifying Financial Resources
2
3 Small communities may be unable to maintain even low-cost ground water technologies
4 without adequate management and revenues. Fee structures should take into account operating
5 funds and revenues for capital improvements. In some communities, insufficient funding is the
6 result of a small population and very low average per capita income. Unfortunately, without
7 adequate funding, small systems have difficulty hiring skilled managers who could increase
8 revenues and ensure effective business planning.
9
10 State and local governments may be available to assist small systems with identifying and
11 overcoming these deficiencies. Some States have performance appraisal programs that require
12 each regulated water system to assess its short-and long-term ability to:
13
14 Provide adequate quantities of water;
15
16 Meet water quality standards; and
17
18 Operate and maintain the plant.
19
20 States can also require PWSs to achieve levels of performance prior to issuing operating
21 permits. The performance appraisal by either the State or PWS may include evaluating the
22 following:
23
24 The system's record of responses to previous significant deficiencies, orders, or
25 outbreaks.
26
27 Compliance with water quality standards, including monitoring requirements.
28
29 Regulators historically have considered waterborne disease outbreaks, compliance with
30 drinking water standards, operator certification, and sanitary surveys when evaluating small
31 systems. According to the National Research Council (1997), an area that has been overlooked is
32 comprehensive short-term (less than 5 years) and long-term financial planning (20 years). PWSs
33 should engage local governments to provide information on future trends in the service area,
34 population, land use policies, and water demands to evaluate the need for system improvements.
35 Costs for future improvements can be compared to current and future budgets enabling the GWS
36 to project the future rates that would be needed to sustain these budgets.
37
38 If funding problems affecting a system's future fiscal viability are discovered; the system
39 must restructure on its own or involve outside entities such as regional water authorities, local
40 government, or private water systems to plan for and solve the problems. Financial restructuring
41 fits one of four categories (National Academy Press, 1997):
42
43 Direct ownership where the PWS agrees with another authority to take over system
44 ownership or to join with another system to form a regional water authority or
45 agency.
46
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1 A regulatory takeover where the State takes responsibility for transferring
2 management of a failing utility to another entity, or where the owner does not
3 voluntarily relinquish control of the PWS.
4
5 Contract service where O&M, monitoring, emergency assistance, and routine
6 administration are handled by a contractor.
7
8 Support from another utility in the form of training, or purchasing supplies or water
9 to receive high volume discounts.
10
11 Each of these options must be designed to reduce consumer costs by consolidating one or
12 more PWS responsibility within a larger agency or system. The unwillingness of an entity to
13 take over a PWS with problems because of the potential for financial burdens for system
14 improvements, or the fear of liability for water quality standards violations can become a barrier
15 to financial restructuring. States should develop incentives for consolidation or restructuring
16 where appropriate, and limit the use of State Revolving Funds (SRFs) to circumstances where all
17 other possibilities have been exhausted (as determined from State performance appraisals).
18 American Water Works Association Research Foundation (AwwaRF) project #4075 (expected to
19 be finalized in 2008) will present benefits of system consolidation and other regional solutions to
20 water services, including case studies.
21
22
23 2.8.2 Security Measures
24
25 Systems may have areas that are potentially susceptible to security breaches such as at a
26 system's wells, storage facilities, and pumping stations. Vulnerable areas include un-manned or
27 temporarily un-manned areas with finished water. If a system is notified of potential areas for
28 vandalism, it should install appropriate security measures. Security measures may include
29 surrounding the facility with barbed wire-topped, chain link fences with locked gates. Systems
30 should also ensure that all buildings such as well houses and pump stations are locked with
31 secure locking systems. Facility staff should also remove ladders to storage facilities and/or lock
32 the ladder access opening. Systems should padlock access hatches, ensure that vents are secure,
33 and, include an internal or in-line check valve for design overflows. In the rare cases where
34 vandalism is a real problem and presents a significant risk, the system may need to provide a
35 security staff.
36
37
38 2.8.3 Examples of Significant Deficiencies
39
40 Failure to meet water supply demands/interruptions in service.
41
42 Inadequate technical, managerial and financial resources to continue to reliably
43 operate the system.
44
45 Inadequate resources for emergency response or lack of emergency response plan.
46
47
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1 2.8.4 Identifying Corrective Actions
2
3 Additional source of supply, new service limits, interconnections or cooperative
4 agreements with nearby systems.
5
6 TMF capacity development improvement plan.
7
8 Asset management plan, operations plan, and/or business plan.
9
10 Emergency response plans, cooperative agreements.
11
12
13 2.8.5 Additional Information and Resources
14
15 USEPA
16 Technical: http://www.epa.gov/safewater/smallsystems/technical help.html
17 Managerial: http://www.epa.gov/safewater/smallsystems/managementhelp.html
18 Financial: http://www.epa.gov/safewater/smallsystems/fmancialhelp.html
19 Compliance: http://www.epa.gov/safewater/smallsystems/compliancehelp.html
20 Emergency/Response Planning: http://cfpub.epa.gov/safewater/watersecurity
21
22 Sources of Technical and Financial Assistance for Small Drinking Water Systems Publication
23 number EPA 816-K-02-005
24
25 Asset Management: A Handbook for Small Water Systems, Publication Number EPA 816-R-03-
26 016
27
28 Strategic Planning; A Handbook for Small Water Systems, Publication Number EPA 816-R-03-
29 015
30
31 Drinking Water State Revolving Fund-http://www.epa.gov/safewater/dwsrf7
32
33
34 2.9 Operator Compliance with Certification Requirements
35
36 Operator certification programs establish minimum professional standards for the
37 operation and maintenance of public water systems. In 1999, EPA issued operator certification
38 program guidelines specifying minimum standards for certification and recertification of the
39 operators of community and nontransient noncommunity public water systems. While the
40 specific requirements vary from state to state, operator certification programs generally set
41 minimum certification requirements based on criteria such as system size and the type of
42 treatment provided.
43
44 All States have operator training programs for PWS operators through workshops,
45 informal instruction, equipment vendors, and technical schools and universities. Management
46 and administration of the system are essential to system sustainability, but many training
47 programs do not address these areas, even though many operators of small systems are
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1 responsible for them (National Academy Press, 1997). The training areas necessary to run a
2 small water system include the following:
3
4 Metering,
5
6 Customer service,
7
8 Financing,
9
10 Administration,
11
12 Budget management (unless another entity is responsible for it),
13
14 Water treatment,
15
16 Water distribution, and
17
18 Public health.
19
20 Several types of training are necessary and should be part of an on-going and coordinated effort
21 to meet the needs of small systems. A PWS design may be quite advanced even where a service
22 area is small. Therefore small system operators need site-specific training to operate their
23 system from either the equipment manufacturer or other means to ensure that they are thoroughly
24 knowledgeable about the system
25
26
27 2.9.1 Examples of Significant Deficiencies
28
29 No certified operator where one is required by the State.
30
31 Operator is not certified at the level required by the State.
32
33
34 2.9.2 Identifying Corrective Actions
35
36 Corrective action plan or compliance plan/agreement for certification.
37
38 Assistance from other PWSs.
39
40 Contracts or other formal arrangement for certified operator support.
41
42
43 2.9.3 Additional Information and Resources
44
45 EPA Operator Certification Information www.epa.gov/safewater/operatorcertification/index.html
46
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1 AWWA Operator Certification Information
2 (800)-926-6142
3 www.awwa.org
4
5 University of Florida TREEO Center
6 (352) 392-9570
7 www.treeo.ufl.edu/
8
9 Sacramento State University-Office of Water Programs
10 (916)278-6142
11 www.owp.csus.edu/
12
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1 3. Eliminating Sources of Contamination
2
O
4 This chapter presents some of the corrective actions a PWS can employ to eliminate,
5 remove, or remediate causes and sources of contamination. The purpose of these corrective
6 actions is to eliminate existing potential sources of microbial contamination within water supply
7 sources, distribution systems, storage tanks, or as a result of vandalism, and to minimize the
8 impact of flooding and to eliminate cross-connections that can contaminate a PWS. This chapter
9 will discuss the following corrective actions:
10
11 Source Water Rehabilitation
12
13 - Identifying Contamination Causes,
14
15 - Preventing Contamination from an Abandoned Well,
16
17 - Rehabilitating an Existing Well, and
18
19 - Minimizing Contamination after a Flood.
20
21
22 3.1 Source Water Rehabilitation
23
24
25 3.1.1 Identifying Contamination Causes
26
27 Salvato (1998) identified four probable causes of fecal contamination of ground water
28 used as a source for drinking water:
29
30 1. Lack of proper disinfection of a well following repair or construction;
31
32 2. Failure or lack of a sanitary seal at the place where the pump line goes through the
33 casing;
34
35 3. Failure to seal the annular space between the drilled hole and the outside of the
36 casing; and
37
38 4. Contamination by surface water or wastewater from the surrounding soil or the
39 aquifer.
40
41 For situations where the appropriate corrective action is not obvious, or where the
42 sanitary survey does not provide enough information, the State should fill in the information
43 gaps as necessary to identify the most effective actions that can be taken in the least amount of
44 time and at the lowest cost. Where needed, extra time may be required to determine the direction
45 of ground water flow under static and pumping conditions. County or local health department
46 records may have to be reviewed and landowners interviewed to determine potential
47 underground sources of contamination.
48
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1 Additionally, multiple contamination sources may complicate identification or
2 elimination of the contaminant sources. Even if a source of contamination is eliminated, there
3 may be a period of time that a well will continue to be contaminated. Therefore, systems should
4 verify results of corrective actions with further source water microbial monitoring.
5
6 Additional detail about item one (the lack of proper disinfection) is provided in Section
7 3.1.3.4; the remaining items are discussed in more detail in this section.
8
9 Failure or lack of a sanitary seal at the place where the pump line goes through the casing
10
11 If the suspected cause of contamination is an underground leak where a pump line goes
12 through the casing, a dye or salt solution can be poured around the casing, and samples taken for
13 visual or chemical analysis. The seal can also be excavated to visually inspect for damage. If
14 contamination is through holes in the casing or if there are channels leading to the casing from a
15 source of contamination, dyes can be used to trace the flow path. A light source or mirror can be
16 lowered into the casing to see if light coming through cracks in the casing is visible outside the
17 casing (Salvato, 1998).
18
19 Failure to seal the annular space between the drilled hole and the outside of the casing
20
21 Depending on the results of dye tests and other investigation, some sources can be
22 remediated with simple repairs. Other deficiencies, such as an unsealed annular space, are more
23 difficult to correct. An experienced well-driller should be contacted to investigate the possibility
24 of grouting the annular space and installing a new casing or inner casing in rock or other tight
25 sealing material (Salvato, 1998). If the casing is not a problem, then pollutants are most likely
26 flowing to the well through the aquifer. In some cases, although this is costly, the well casing
27 could be sealed at some depth to seal off the polluted stratum, or drilled deeper to a new water-
28 bearing layer. Unless the polluted layer of water-bearing material is effectively sealed off, future
29 contamination cannot be prevented.
30
31 Contamination by surface water or wastewaterfrom surrounding soil or the aquifer
32
33 Shallow wells and wells near a surface water body in an aquifer that is loosely
34 consolidated can experience contamination from surface water. If a ground water source is
35 experiencing contamination from surface water, then it should be evaluated to determine if it is
36 GWUDI. If classified as GWUDI, the system would be considered a subpart H system and must
37 provide treatment and meet the other requirements of the SWTRs. If not classified as GWUDI
38 or an underground aquifer is contaminated by leaking septic tanks or other contamination
39 sources and the source of contamination cannot be eliminated, the system may need to replace,
40 rehabilitate, or abandon the well and fill it with neat cement grout or puddled clay to contain the
41 contamination.
42
43
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1 3.1.2 Preventing Contamination from an Abandoned Well
2
3 Abandoned wells can offer a near-perfect conduit for contaminants from the surface (i.e.,
4 runoff water, waste disposal) or below-grade (i.e., septic systems, class 5 shallow injection wells,
5 overlaying contaminated aquifers) to migrate into underground sources of drinking water. Some
6 abandoned wells have had the casing removed leaving the entire bore hole open for passage of
7 fluids. Larger, open wells also pose safety hazards for small children and animals. Often these
8 abandoned wells are old and poorly constructed with no grout seal around the casing and/or no
9 cap on the casing. This allows water and contaminants to move down the casing through the
10 annular opening or casing and contaminate the aquifer that supplies drinking water to the nearby
11 PWS.
12
13 When a system has concluded that an abandoned well is the source of contamination it
14 should contact the State primacy agency to obtain information on the correct procedures for
15 proper abandonment. Currently, the majority of States have detailed construction standards for
16 well abandonment that are crafted to keep water and contaminants from migrating up or down
17 the bore hole. In most cases, when a well is to be permanently abandoned, the State will require
18 it to be completely filled in such a manner that vertical movement of water within the well bore,
19 including vertical movement of water within the annular space surrounding the well casing, is
20 effectively and permanently blocked. All fluids within the well should be confined to the
21 specific strata that they were originally encountered in and the controlling geologic conditions
22 restored to those of pre-well construction.
23
24 Artesian wells, free-flowing artesian wells, and gravel pack wells can present special
25 abandonment problems. Often States have specific standards for abandoning these kinds of
26 wells. If the State does not have such standards, the system should seek advice from an engineer,
27 well driller, hydrologist, or other professional.
28
29
30 3.1.3 Remediating an Existing Well
31
32 Damaged or improperly constructed wells have a significantly higher potential for virus
33 occurrence and/or higher concentrations of viruses than properly constructed wells. As a point of
34 reference, Exhibit 3.1 shows an example of a properly constructed pump house and its
35 appurtenances. Exhibit 3.2 shows an example of a submersible pump with pitless adapter. Prior
36 to making significant investments in well remediation, systems should consider hiring a well
37 qualified contractor to assess the well integrity and condition. Remediating an existing well that
38 is at the end of its useful life may not be cost effective.
39
40 The pump room floor should be watertight, preferably made of concrete and should slope
41 away from the well casing in all directions (Ten States Standards, 2007). It is unnecessary to use
42 an underground discharge connection if an insulated, heated pump house is provided. If the
43 pump room is not continuously manned, it is not necessary to maintain the temperature at typical
44 room conditions, only warm enough to prevent freezing. For individual installations in rural
45 areas, a thermostatically controlled electric heater will generally provide adequate protection for
46 the equipment when the pump house is properly insulated.
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1
2
Exhibit 3.1 Pump House and Well Appurtenances
3
4
5
6
VENTILATON^ M WARNING BELL
n
Source: USEPA, 2003
Well House
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1
2
Exhibit 3.2 Submersible Pump with Pitless Adapter
3
4
5
Pitless Adapters
SANITARY'WELL COVER
(VENTED)
SUBMERSIBLE CABLE
CONDUIT
PPFLESS ADAPTER
f\ PI SCH AR GE F ITT I NG|
FLEXIBLE CONNECTION
SNIFTER VALVE or
AIR CHARGER
CEMENT GROUT
FOR MAT ION.SEAL
Source: USEPA, 2003
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1 In some cases, the transport of microorganisms occurs due to improper well seals or
2 casings that can result in large, open conduits for fecal contamination to pass unimpeded into the
3 water supply. This is particularly true of small systems and older systems that were not
4 originally constructed in accordance with their respective State's design and construction
5 standards (Linsley et al., 1992).
6
7 If a system must remediate a well, it may need to repair or replace the well screen, well
8 casing, well seal, or even the well pump. The well casing should extend above ground, and the
9 system should grade the ground surface at the well site to drain away from the well. If a new
10 well casing is needed, the system should consult with applicable State or local standards, or
11 where no regulations exist, consult with other national criteria such as the AWWA Standards
12 (1997) or the Ten States Standards (2007) (Chapter 3.2).
13
14 The following subsections contain information regarding well rehabilitation, including
15 correcting drainage problems, replacing a sanitary well seal, eliminating a well pit, and
16 disinfecting wells and applying shock chlorination.
17
18
19 3.1.3.1 Correcting Drainage Problems
20
21 Wells should be located in areas with good drainage to prevent surface water runoff from
22 entering the well casing where it may find its way into the ground water via the annular opening
23 around the casing. Drilling in an area of low elevation allows the driller to penetrate the aquifer
24 at a shallower depth from ground surface and reduces drilling costs. Unfortunately, it can also
25 make the well subject to contamination from surface runoff.
26
27 Exhibit 3.3 depicts how a drainage problem can be corrected by placing fill material
28 around the well casing, compacting the fill, and grading it away from the casing. In some cases
29 the well casing may need to be extended to ensure that it terminates a minimum of 18 inches
30 above the final ground surface (Ten States Standard, 2007). EPA recommends that systems pour
31 a concrete pad around the casing to ensure drainage away from the well.
32
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1
2
Exhibit 3.3 Example of Correcting Drainage Problems
Sanitary Well Seal
(a)Well with drainage toward casing
(b) Well casing exetended and fill placed
to direct water away from well.
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
3.1.3.2 Replacing a Sanitary Well Seal
Well seals are used to cover the top of a well casing pipe to prevent surface runoff from
entering the casing (Purdue, 1997). In some cases sanitary well seals must be replaced to prevent
additional contamination from entering the well through the top of the casing.
Well seals are provided with vents to allow air movement in and out of the casing as the
water level fluctuates with pumping. The vents are screened to exclude insects and have
openings turned downward in order to keep out dust. Systems should check seals and vents
regularly, however, because insects and mice may enter in the event that a power cable opening
is unprotected, a vent is unscreened, or a well cap overlaps with, but does not completely seal,
the well casing.
The sanitary well seal pictured in Exhibit 3.4 is designed for use on wells that are
terminated within well houses. As the bolts are tightened, the two plates are pulled together,
expanding the gasket material located between the plates. This seals the openings around the
casing, the pump drop pipe, the inverted U-type screened vent, and the electrical conduit.
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1
2
Exhibit 3.4 Sanitary Well Seal with Expandable Gasket
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
The well seal shown in Exhibit 3.5 is more commonly used in outdoor applications with
submersible pumps and pitless adapter units. This seal has no openings on its top and is sloped
so that rainwater will run off. The vents are located on the underside of the lip surrounding the
casing, and gasket material seals all openings around the casing and conduit.
Exhibit 3.5 Overlapping Exterior Well Seal
The replacement well seal must be of the proper size and type to fit the casing and
accommodate other well appurtenances. Systems should coordinate with the State to make sure
that the type of replacement well seal chosen is approved by the State.
3.1.3.3 Eliminating a Well Pit / Buried Well
In the northern parts of the United States, many older wells were terminated within pits in
order to keep them from freezing during colder months. Such pits are dangerous to enter
because of confined space safety issues, and are subject to flooding that can cause loss of service
and contamination of the aquifer. Well pits are not considered a method of sanitary construction.
June 2008 Ground Water Rule
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1 To eliminate the well pit, the system should extend the casing so that it will terminate at
2 least 18 inches above the finished grade or 12 inches above the pump house slab (Ten States
3 Standards, 2007). The pit then needs to be backfilled with suitable material and compacted.
4 Bentonite or other grout material should be placed around the casing as backfilling occurs in
5 order to keep water from moving down the casing. A pump house should be constructed around
6 the well if the original pit well was constructed to keep the top of the well below the frost line.
7
8
9 3.1.3.4 Temporary Disinfection of Wells by Applying Shock Chlorination
10
11 If a system is found to have a serious deficiency or fecal contamination, it may take time
12 for the system to design and install a corrective action. In the meantime, the system cannot serve
13 the contaminated water to its customers. The primacy agency may require the system, as part of
14 its corrective action, to apply chlorination until the contamination is eliminated or a corrective
15 action is put in place. Hypochlorination will generally be used because it is easier to install and
16 operate than gaseous chlorination or other disinfection methods and is the least costly of the
17 treatment methods.
18
19 It is important to note that temporary disinfection is meant to deal with a single
20 contamination event, such as a flood, or maintenance on a well. Shock chlorination is not
21 intended to deal with a chronic problem, such as a cracked casing or a well next to a failed septic
22 system.
23
24 Shock chlorination can be effectively used to treat iron- and sulfate-reducing bacteria in
25 PWSs and to treat PWSs contaminated with high levels of heterotrophic plate counts (HPC) or
26 coliform bacteria (Alberta, 1999). Disinfection should occur promptly in order to reduce the
27 possibility of growth of undesirable biofilms within the well and reduce the potential for
28 migration of the microbial contaminants.
29
30 It is essential to make sure that the disinfecting agent comes in contact with all portions
31 of the well, pumping equipment, and plumbing during shock chlorination. To be effective, shock
32 chlorination must disinfect the following (Alberta, 1999):
33
34 The entire well depth;
35
36 The formation around the bottom of the well;
37
38 The pressure system;
39
40 Some water treatment equipment; and
41
42 The distribution system.
43
44 Disinfection with Calcium Hypochlorite
45
46 Calcium hypochlorite solution (approximately 65 percent available chlorine by weight) is
47 an effective and widely used method of disinfecting wells (USEPA, 1982). Calcium
48 hypochlorite is available in tablet and powder form. Exhibit 3.6 shows quantities of calcium
49 hypochlorite to be used in treating wells of different diameters and water depths.
June 2008 Ground Water Rule 3-10 Public Review Draft
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
When disinfecting newly constructed wells or disinfecting wells after maintenance,
calcium hypochlorite is added to provide a dosage of at least 100 milligrams per liter (mg/L) of
available chlorine in the well water. For wells with chronic biofouling problems, much higher
concentrations of chlorine and repeated applications may be necessary. Additional chemicals
and treatment techniques may be needed if biological growth has caused encrustation of the well
(see Borch, et al., 1993 for details). While preparing a stock solution of calcium hypochlorite,
the percent available of chlorine by weight must be taken into account during the weighing of the
chemicals. It is useful to prepare a stock solution first (e.g. mixing 2 ounces of hypochlorite with
2 quarts of water). To prevent corrosion problems, the solution should be prepared in thoroughly
cleaned glass containers.
Exhibit 3.6 Quantities of Calcium Hypochlorite, 70% for (Rows A) and Liquid
Chlorine Bleach*, 5.25 % (Rows B) to Provide a Chlorine Dosage of at Least
100 mg/L
Well
Diam. Inches
Depth(feet)
5A
5B
10A
10B
ISA
15B
20A
20B
30A
30B
40A
40B
60A
60B
80A
SOB
100 A
100B
150 A
150B
2
IT
1C
IT
1C
IT
1C
IT
1C
IT
1C
IT
1C
IT
1C
IT
1C
2T
1C
3T
2C
3
IT
1C
IT
1C
IT
1C
IT
1C
IT
1C
IT
1C
2T
1C
3T
1C
3T
2C
5T
2C
4
IT
1C
IT
1C
IT
1C
IT
1C
2T
1C
2T
1C
3T
2C
4T
2C
5T
3C
8T
4C
5
IT
1C
IT
1C
IT
1C
2T
1C
3T
1C
4T
2C
5T
3C
7T
4C
8T
1Q
4oz
2Q
6
IT
1C
IT
1C
2T
1C
3T
1C
4T
2C
6T
2C
8T
4C
9T
1Q
4 oz
1.5 Q
6 oz
2.5 Q
8
IT
1C
2T
1C
3T
2C
4T
2C
6T
4C
8T
1Q
4 oz
2Q
5 oz
2Q
7oz
2.5 Q
10 oz
4Q
10
2T
1C
3T
2C
5T
3C
6T
4C
3oz
1.5 Q
4 oz
2Q
6 oz
3Q
8oz
3.5 Q
10 oz
4Q
lib
6Q
12
3T
1C
5T
2C
8T
4C
3oz
1Q
4 oz
2Q
6 oz
2.5 Q
9oz
4Q
12 oz
5Q
lib
6Q
1.5 Ib
2.5 G
16
5T
2C
8T
1Q
4oz
2C
5oz
2.5 Q
8oz
4Q
10 oz
4.5 Q
20
6T
4C
4oz
2Q
6 oz
2.5 Q
8oz
3.5 Q
12 oz
5Q
lib
7Q
24
3oz.
1Q
6 oz
3Q
9oz
4Q
28
4 oz
2Q
8oz
4Q
12 oz
5Q
32
5 oz
3Q
10
4Q
lib.
6Q
42
7oz
3Q
13 oz
6Q
1.5 Ib.
2G
48
9oz
3Q
1.5 Ib
8Q
1.5 Ib
3G
20
21
22
23
24
25
26
27
Source: (USEPA, 1982)
* That meets NSF Standard 60.
Notes: Quantities are T = tablespoons; oz = ounces (by weight); C = cups; Ib = pounds; Q = quarts; G = gallons.
Values corresponding to rows A are solid calcium chloride required; those corresponding to rows B are
amounts of liquid household bleach.
Operators of systems using calcium hypochlorite need to be cautious when handling and
storing the chemical and should always carefully read and follow all safety and storage
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1 instructions. Calcium hypochlorite should always be added to water (i.e., water should never be
2 added to calcium hypochlorite). Calcium hypochlorite will release chlorine gas on contact with
3 acids and should be stored separately. Also, since the chemical exhibits caustic and corrosive
4 properties, operators should wear goggles, gloves, and respirators when working with calcium
5 hypochlorite, and should only work in areas with suitable ventilation.
6
7 Protocols for disinfecting new or recently repaired wells can be found in American Water
8 Works Association (AWWA) C654-03. A simpler procedure that can be used for smaller wells is
9 as follows (USEPA, 1982):
10
11 Determine the volume of water in the well based on the casing diameter, static water
12 level, and depth of casing. Calculate the amount of chlorine solution or granular
13 chlorine necessary to bring that volume of water, and the water in the plumbing, to
14 the required concentration (see Exhibit 3.5). Before disinfection, the well must be
15 purged of any accumulated sediment and debris and be free of turbidity for
16 disinfection to be effective.
17
18 Add the correct amount of chlorine to 5 - 10 gallons of fresh water and pour the water
19 down the casing. Try to make sure the chlorinated water contacts the inside of the
20 casing and outside of the drop pipe as it enters the well so it can clean and disinfect
21 those surfaces.
22
23 Operate the pump until the odor of chlorine can be detected or use a DPD test kit (a
24 kit which uses test reagents and color charts) to measure the chlorine residual in
25 addition to detecting chlorine odor.
26
27 Shut off the pump and allow the chlorinated water to remain in the well and plumbing
28 for 24 hours.
29
30 After 24 hours, turn on the pump and flush the chlorinated water from the well and
31 plumbing equipment. Make sure the chlorinated water is not discharged to surface
32 water or to any other area where the chlorine could cause damage or violations of the
33 Clean Water Act. Continue flushing for at least one hour after the odor of chlorine has
34 dissipated.
35
36 Collect one coliform sample at the well head for three consecutive days. If any of the
37 three samples are coliform positive, repeat the process.
38
39 Once the source water is tested free of chlorine residual, the operator should collect a few
40 samples of water for water quality analysis from a clean non-leaking tap. Water should be
41 flushed from the tap for a few minutes before sampling. The number of bacteriological samples
42 collected depends on State guidelines; samples are sent to a State-approved laboratory for
43 analysis.
44
45 Make sure to contact the laboratory for the proper sample collection and storage
46 procedures. Analyses can be run on several chemical, physical, and biological parameters such
47 as nitrogen, lead, manganese and other metals, sulfates, cyanide, pH, and/or coliforms. Most
48 States designate the specific parameters required for analyses. Samples should not indicate the
49 presence of an inorganic contaminant above EPA's maximum contaminant level (MCL),
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1 secondary maximum contaminant level (SMCL), or exceed a count of zero for the
2 bacteriological indicators. If tests conducted after disinfection indicate that the water is not safe
3 for use, the disinfection procedure needs to be repeated until tests show that water samples are
4 satisfactory.
5
6 One of the concerns with disinfecting a newly developed or rehabilitated well is the
7 potential risk of discharging chlorinated waters directly into surface water bodies. Since high
8 levels of chlorine (prior to discharge) can be harmful to aquatic life, chlorinated waters may need
9 to be dechlorinated to reduce the chlorine in the water to acceptable levels. Dechlorination can
10 be achieved by applying dechlorination chemicals such as thiosulfate or ascorbic acid. If the
11 amount of water to be dechlorinated is small, passive techniques such as discharge through hay
12 bales or other natural structures and detention in holding ponds can be used (Tikkanen et al.,
13 2001).
14
15 In some cases, the discharge may be regulated by a National Pollutant Discharge
16 Elimination System (NPDES) or a State permit. PWSs should contact their primacy agency for
17 more information about applying for an NPDES or a State permit. Some utilities may inject the
18 chlorinated water and other waste streams into the ground by underground injection wells. The
19 underground injection control (UIC) program regulates the discharge of such units and ensures
20 that the water is discharged below the lowest level of any aquifer serving as a source of potable
21 water and that the migration of the injectate into pristine ground waters is avoided.
22
23
24 3.1.4 Minimizing Contamination after a Flood
25
26 After a flood, PWSs should inspect, clean, and pump wells, and then disinfect wells that
27 have been flooded and test the water prior to use. Flood precautions issued by the State and local
28 health department should be followed in addition to EPA guidelines (USEPA, 2005a).
29 Additionally, a PWS should address why the flooding occurred and determine whether the cause
30 of flooding can be eliminated, mitigated, and/or minimized. A system is much better off
31 preventing the contamination by managing the risk of flooding rather than responding to
32 contamination from a flood after the fact.
33
34 Floods may cause some wells to collapse; therefore, conditions at the wellhead should be
35 checked. Swiftly moving flood water can carry large debris that could loosen well hardware,
36 dislodge well construction materials, or distort casing. Coarse sediment in flood waters could
37 erode pump components. If the well is not tightly capped, sediment and flood water could enter
38 the well and contaminate it. Wells that are more than 10 years old or less than 50 feet deep are
39 likely to be contaminated, even if there is no apparent damage
40 (http://www.epa.gov/safewater/privatewells/whatdo.html).
41
42 Electrical systems should not be turned on until after flood waters have receded and the
43 pump and electrical system have dried. The wiring system should be checked by a qualified
44 electrician, well contractor, or pump contractor. If the pump's control box was submerged
45 during the flood, all electrical components must be dry before electrical service can be restored.
46 Pumps and their electrical components can be damaged by sediment and floodwater. The pump,
47 including the valves and gears, will need to be cleaned of silt and sand.
48
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1 To avoid damage to drilled, driven, or bored wells, remove mud, silt and other debris
2 from around the top of the well. If excessive mud, silt or sediment has entered the well, the
3 pump may need to be removed or bailers used to remove mud and silt from the bottom of the
4 well. It is not recommended to attempt to disinfect or use a dug well after it has been flooded.
5
6 To minimize contamination after a flood, pump the well until the water runs clear to rid
7 the well of flood water. Depending on the size and depth of the well and extent of
8 contamination, pumping times will vary. If the water does not run clear, further investigation
9 into the cause of the problem is necessary before attempting to disinfect.
10
11 Emergency disinfection after a flood should be performed according to the shock
12 chlorination procedures described in Section 3.1.3.4. Wells can remain contaminated even after
13 disinfection procedures are followed, so sampling and testing the water are necessary to ensure
14 safe drinking water. In extensive flood areas, the speed and direction of ground water flow can
15 cause wells to remain contaminated for months. Septic systems should not be used immediately
16 after floods because drain fields will only work once the ground is no longer saturated.
17 Additionally, water systems should avoid pumping of a septic tank when the soil is saturated to
18 prevent the tank from collapsing due to a static pressure differential. In such cases, long range
19 precautions such as testing should be used to protect drinking water.
20
21 Since well disinfection does not provide protection from pesticides, metals, or other types
22 of non-biological contamination, further cleanup and analyses are necessary when such
23 contamination is suspected. Also, if drums or barrels are moved by the flood within the wellhead
24 protection area, special treatment may be required. For specific questions on various
25 contaminants, the EPA Safe Drinking Water Hotline (1-800-426-4791) or the Superfund Hotline
26 (1-800-424-9346) can be contacted.
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1 4. Providing an Alternative Source of Drinking Water
2
O
4 If remediating an existing source of drinking water is not an option, the next step is to
5 consider alternative sources of drinking water. If a well is contaminated, abandoning the well
6 and connecting to another public water supply, or consolidating with another utility are options
7 for providing safe drinking water. In some cases bottled water can be used as a short-term
8 solution. Another choice is to install a new well that is properly constructed, cased, and sealed
9 to prevent ground water contamination. This chapter provides detailed descriptions of the types
10 of new wells and well characteristics to consider when installing a new well. The alternative
11 source options addressed in this chapter are:
12
13 Consolidating/purchasing water from another utility (Section 4.1);
14
15 Providing bottled water (Section 4.2);
16
17 Installing a new well (Section 4.3); and
18
19 Switching to a surface water source (Section 4.4).
20
21
22 4.1 Providing Bottled Water (Short Term)
23
24 Another option for a utility to ensure safe drinking water to its customers is to provide
25 them with bottled water. The use of bottled water in lieu of piped water for direct consumption
26 and cooking purposes is used only as a short-term solution to a contamination problem while
27 other permanent solutions are being implemented for the following reasons (40 CFR 141.101):
28
29 Relative expense of bottled water;
30
31 Demanding logistics of distribution; and
32
33 Does not provide safe water for other household uses.
34
35 Water systems have little to no control over the quality of bottle water. Bottled water is
36 regulated by the United States Food and Drug Administration (FDA) under the Federal Food,
37 Drug, and Cosmetic Act (21 U.S.C. 301 et seq.) if sold in interstate commerce and the State if
38 sold only in intrastate commerce. Bottled water manufacturers must abide by all applicable
39 federal and State standards, including following the FDA's Good Manufacturing Practices and
40 meeting quality and labeling standards before bottled water is sealed in a sanitary container and
41 sold for human consumption. The bottled water standard of quality establishes allowable levels
42 for substances in bottled water, including coliform and lead and other physical, chemical,
43 radiological, and microbiological standards (21 CFR 165.110). The International Bottled Water
44 Association (IBWA) lists the FDA product definitions for bottled water on its website
45 (http://www.bottledwater.org/public/pdf/IBWA05ModelCode Mar2.pdf) (IBWA, 2005).
46
47 In addition to FDA's extensive regulatory requirements, the bottled water industry is also
48 subject to State regulatory requirements. States are responsible for inspecting, sampling,
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1 analyzing, and approving sources of water. States also conduct the certification of testing
2 laboratories. In some instances there are drinking water utilities that bottle their own water. In
3 all instances, only approved sources of water can be used to supply a bottling plant.
4
5
6 4.2 Consolidating/Purchasing Water from Another Utility
7
8 Consolidating with another public water utility may be the only option for a utility with
9 extremely limited financial and technical resources. Such utilities may not be able to invest in
10 new infrastructure for providing their customers with an alternate source of drinking water.
11 Consolidating with a utility that has greater resources at its disposal can help ensure a safe and
12 alternative drinking water supply source to customers.
13
14 Purchasing water from another PWS may be a sound economical solution to providing an
15 alternate source of safe drinking water. However, the purchasing utility may have to disinfect
16 the water before bringing the purchased water into the distribution system. Deciding to disinfect
17 depends on whether the purchased water has an adequate disinfectant residual to control
18 microbial re-growth in the distribution system and whether disinfection is necessary at all. If
19 disinfection is needed, the purchasing utility may need to install or modify existing contactor
20 and/or clearwell capacity to post-disinfect the water.
21
22
23 4.3 Installing a New Well
24
25 In many cases, the primacy agency and ground water system may find the best corrective
26 action for a contaminated well or significantly deficient well is to install a new well. There are
27 many types of wells -bored, driven, jetted, drilled - which are discussed in this section. In
28 addition, there are basic construction components to wells, such as the well casing (typically
29 steel, plastic, or PVC), grout (typically cement, concrete, or clay), surface seal, and screens.
30 This section provides an overview of some of the issues that the primacy agency and system
31 should discuss when considering installing a new well as part of a corrective action. The
32 specific standards for design, testing, and installation vary from state to state.
33
34
35 4.3.1 Critical Factors in Well Construction
36
37 If a decision has been made to install a new well, the availability of adequate quantity
38 and quality of water is the first critical factor. Other critical factors controlling well suitability
39 include well casing and grouting, surface seals, and the potential for flooding (Jorgenson, et al.,
40 1998). These assumptions regarding what constitutes an acceptable well are shown in Exhibit
41 4.1. Section 4.3.3 provides additional information on sanitary construction of wells.
42
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1
2
Exhibit 4.1 Well Construction and Condition
Acceptable
The well is cased and grouted to the confining layer
or production zone
The casing is steel, plastic, PVC, or other non-
porous material
The well has a surface seal
Well should be of adequate depth and distance from
a body of surface water to prevent it from being
classified as a GWUDI
Unacceptable
The casing, grouting, or surface seal is damaged or
leaking
The well is subject to periodic flooding
Shallow well or well under the direct influence of
surface water
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Source: Jorgenson, et al./USEPA, 1998
Casing
All wells should be cased and grouted or otherwise sealed. The casing should extend
from the surface through a confining layer (if there is one) or to the production zone in the
aquifer. The casing should be composed of a nonporous material such as steel or plastic (Ten
States Standards, 2007).
All wells should be constructed in accordance with State and local requirements;
common State standards are shown in Exhibit 4.2.
Exhibit 4.2 Ten State Standards (2007) Recommendations for Casing
Steel Casing
Nonferrous Casing
Temporary steel casing used for construction
must be capable of withstanding the structural
load imposed during its installation and
removal.
Permanent steel casing pipe should:
o Be a new single steel casing pipe meeting
AWWA Standard A-100, ASTM, or API
specifications for water well construction;
o Have specified minimum weights and
thickness;
o Have additional thickness and weight if
minimum thickness is not considered
sufficient to assure reasonable life
expectancy of a well;
o Be capable of withstanding forces to which
it is subjected;
o Be equipped with a drive shoe when driven;
and
o Have full circumferential welds or threaded
coupling joints.
The following guidelines are for nonferrous
casing materials:
o Approval of any nonferrous well-casing
material is subject to special determination
by the reviewing authority before
submissions of plans and specifications; and
o Nonferrous well-casing material must be
resistant to:
- Water corrosivity,
- Stresses of installation, and
- Grouting and operation.
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1
2 Surface Seal
3
4 The surface seal should be installed around the well to protect it from contamination that
5 could enter between the casing and the borehole wall. The seal should fill the space between the
6 casing and borehole wall and extend to a depth at least below the frost line. In some cases, the
7 cement grout can be extended to the surface to form the surface seal (Massachusetts DEP, 2004).
8
9 Protection from Flooding
10
11 The well should be protected from flooding. A well located in a periodic floodplain or in
12 a topographic depression that collects surface runoff can become contaminated by either direct
13 flow or seepage around the seal. To prevent flooding, the casing can be extended to a height
14 above the expected flood level and surface seals and grout can be used to seal it (Ten States
15 Standards, 2007).
16
17
18 4.3.2 Types of Wells
19
20 This section describes different types of wells and how each is constructed. Most wells
21 constructed today are drilled wells. However, bored wells may also be installed or constructed.
22 According to Ten State Standards (2007), drilling fluids and additives should not impart any
23 toxic substances to the water or promote bacterial contamination. Minimum protected depths of
24 drilled wells provide watertight construction to such depths as may be required by the State to
25 exclude contamination and seal off formations that are or may be contaminated.
26
27
28 4.3.2.1 Bored Wells
29
30 Bored wells are usually constructed with earth augers turned by hand or power
31 equipment (USEPA, 1973). These wells can be constructed to a depth of up to 100 feet if the
32 water requirement is low and the overlying material contains few large boulders and has non-
33 caving properties (Purdue Research Foundation, 2001). Because the bore holes for these wells
34 must remain open until the casing is installed, the construction of bored wells is most successful
35 in fine-textured soils (Purdue, 1997).
36
37 Once the well is bored, casing should be inserted into the hole. Bored wells are cased
38 with vitrified tile, concrete pipe, standard wrought iron pipe, steel casing, or other suitable
39 materials capable of sustaining imposed loads (Purdue Research Foundation, 2001). The well is
40 usually completed by installing well screens or perforated casing in the water bearing strata. A
41 gravel layer (approximately 4 inches) is placed around the casing from 10 feet below the land
42 surface to the well bottom. Cement grouting up to adequate depth is necessary to protect the
43 well from surface drainage. The upper 10 feet of the well must be protected from surface
44 contamination by approved construction methods (Purdue, 1997).
45
46
47 4.3.2.2 Driven Wells
48
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1 The simplest and often least expensive method of well construction is to drive a drive-
2 well point that is fitted to the end of a series of pipe sections (USEPA, 2006a). Well-drive points
3 come in a variety of designs and materials. Drive points are usually 1.25 inches or 2 inches in
4 diameter and are driven with the aid of a maul, or a special drive weight. For deeper wells, the
5 well points are sometimes driven into the water bearing strata from the bottom of a bored well
6 (Kansas Geological Survey, 2004). If they can be driven to an appreciable depth below the
7 water table, they are no more likely than bored wells to be seriously affected by water table
8 fluctuations. The most suitable locations for driven wells are areas containing alluvial deposits
9 of high permeability.
10
11 When driving a well, it is common practice to use a hand auger slightly larger than the
12 well point to prepare a pilot hole that extends to the maximum practical depth. The assembled
13 point and pipe are then lowered into the hole. The pipe is driven by directly striking the drive
14 cap that is threaded to the top of the protruding section of the pipe. A maul, a sledge, or a
15 "special driver" may be used to hand drive the pipe. The "special driver" may consist of a
16 weight and sleeve arrangement that slides over the drive cap as the weight is lifted and dropped
17 in the driving process (Department of the Army, 1994)
18
19
20 4.3.2.3 Jetted Wells
21
22 The jetted well technique is a rapid and efficient method of sinking well points (USEPA,
23 1973). A source of water and a pressure pump are needed to use this technique.
24
25 Water is first forced under pressure down the riser and comes out of a special washing
26 point. The well point and pipe are then lowered as material is loosened by the impact of the
27 water jet. Often the riser pipe is used as the suction pipe for the pump. In such cases, surface
28 water may be drawn into the well if the pipe develops holes. An outside protective casing may
29 have to be installed to an adequate depth to ensure protection from the possible entry of
30 contaminated surface water run-off The space between the casings is also filled with cement
31 grout. It is recommended that the system install the protective casing as an auger hole and to
32 drive the point inside it.
33
34
35 4.3.2.4 Drilled Wells
36
37 Exhibit 4.3 shows the layout of a drilled well with a submersible pump. Exhibit 4.3
38 shows a typical wellhead design for submersible pumps. Construction of drilled wells is
39 accomplished by either percussion or rotary drilling.
40
41 Percussion (Cable-tool) Method: This method is accomplished by raising and dropping a
42 heavy drill bit and stem. The impact of the bit crushes and dislodges pieces of the formation.
43 The reciprocating motion of the drill tools mixes the drill cuttings with water into a slurry at the
44 bottom of the hole. This is periodically brought to the surface with a bailer (a 10-20 foot long
45 pipe equipped with a valve at the lower end). Caving is prevented as drilling progresses by
46 driving or sinking a casing slightly larger in diameter than the bit. When good drilling practices
47 are followed, water-bearing beds are readily detected in cable holes because the slurry does not
48 tend to seal off the water bearing formation. A rise or fall in the water level in the hole during
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1 drilling or increased recovery water during bailing indicates that the well has entered a
2 permeable bed.
3
4
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1
2
Exhibit 4.3 Drilled Well with Submersible Pump
= -H SANITARY WE LL SEAL I
7 t
WATER TABLE I
WATER BEARING SAND |
CEMENT GROUT
FORMATION SEAL
SUBMERSIBLE PUMP |
PUMP MOTOR|
WATER BEARING SAND |
DRIVE SHOE |
SCREEN
I
5
6
Source: USEPA, 2003b
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1
2
Exhibit 4.4 Typical Wellhead Design for Submersible Pumps
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
POWER CABLE TO
5UEWERSIBLE PUMP
DROP PIPE FROM
SUBhEP.SIBLEPl.MP
Source: USEPA, 2003a
Hydraulic Rotary Drilling Method
The hydraulic rotary drilling may be used in almost all formations. The drilling
equipment consists of the following:
Derrick,
Hoist,
Revolving table through which the drill pipe passes,
Series of drill pipe sections,
Cutting bit at the lower end of the drill pipe, and
Pump for circulating the drilling fluid and a power source.
The bit breaks up the material as it rotates and advances while the drilling fluid (mud)
that is pumped down the drill pipe picks up the drill cuttings and carries them up the space
between the rotating pipe and the wall of the hole. The mixture of mud and cuttings is
discharged to a settling pit where the cuttings decant to the bottom and the mud is recirculated to
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1 the drill pipe. Once the hole is completed the drill pipe is withdrawn and the casing is placed.
2 The drilling mud is usually left in place and pumped out after the casing and screen are
3 positioned. The space between the hole wall and the casing is generally filled with cement grout
4 in non-water bearing sections, but may be enlarged and filled with gravel at the level of the
5 water-bearing strata (NOWA, 2007).
6
7 Air Rotary Drilling Method
8
9 The air rotary drilling method uses similar equipment to that used for the rotary hydraulic
10 rotary drilling method. The major difference between the two methods is that the air rotary
11 method uses air and the hydraulic rotary drilling method uses mud and water.
12
13 The air rotary method is well adapted to rapid penetration of consolidated formations and
14 is especially popular in regions with limestone aquifers. Penetration rates of 20-30 feet per hour
15 are usually achieved in very hard rock formations. To remove cuttings, upward velocities of at
16 least 3000 feet per minute are required. The air rotary method usually is not suitable for
17 unconsolidated formations where careful sampling of rock materials is required for well-screen
18 installation.
19
20
21 4.3.3 Characteristics of Wells
22
23
24 4.3.3.1 Yields of Different Types of Wells
25
26 Driven wells can be sunk to 30 feet or more below the static water level. Because of
27 their small diameters (2 to 12 inches) they can have relatively small yields. Combining several
28 driven wells can offset the small yield of a single well. Deeper wells with large available
29 drawdowns tend to have higher yields. Drilled and jetted wells can usually be sunk to such
30 depths that the available drawdown can be hundreds of feet (Purdue Research Foundation,
31 2001).
32
33 Exhibit 4.3 provides details about penetrating various types of geological formations
34 using different well drilling methods.
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1
2
3
Exhibit 4.5 Suitability of Well Construction Methods with Different Geological
Conditions
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Characteristics
Range of practical depths
Diameter
Type of geologic formation
Clay
Silt
Sand
Gravel
Cemented gravel
Boulders
Sandstone
Limestone
Dense igneous and
metamorphic rock
Bored
0-1 00 ft
2-30 inches
Yes
Yes
Yes
Yes
No
Yes, if less than
well diameter
Yes, if soft and/or
fractured
Yes, if soft and/or
fractured
No
Driven
0-50 ft
1 .25-2 inches
Yes
Yes
Yes
Fine
No
No
Thin layers
No
No
Jetted
0-1 00 ft
2-12 inches
Yes
Yes
Yes
%" pea gravel
No
No
No
No
No
Characteristics
Range of practical depths
Diameter
Type of geologic
formation
Clay
Silt
Sand
Gravel
Cemented gravel
Boulders
Sandstone
Limestone
Dense igneous and
metamorphic rock
Percussion
0-1 ,000 ft
4-18 inches
Yes
Yes
Yes
Yes
Yes
Yes, when in firm
bedding
Yes
Yes
Yes
Drilled
Rotary Hydraulic
0-1 ,000 ft
4-24 inches
Yes
Yes
Yes
Yes
Yes
Difficult
Yes
Yes
Yes
Rotary Air
0-750 ft
4-10 inches
No
No
No
No
No
No
Yes
Yes
Yes
Source: Grundfos, 2007
4.3.3.2 Sanitary Construction of Wells
When a well penetrates a water-bearing formation, it provides a direct route for potential
contamination at the source. To prevent contamination from reaching the ground water, the
following basic sanitary guidelines should always be followed during the construction of wells
(USEPA, 1992).
Fill the open space outside the casing with a watertight cement grout from a point just
below the frost line (or deepest level of excavation near the well) to as deep as
necessary to prevent entry of surface water. See Section 4.3.3.3 for a detailed
description of grouting requirements.
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1 For artesian basins, seal the casing into the overlying impermeable formations to
2 retain artesian pressure.
3
4 When a water-bearing formation containing poor quality water is penetrated, seal off
5 the formation to prevent infiltration of water into the well and aquifer.
6
7 Install a sanitary well seal with an approved vent at the top of the well casing to
8 prevent the entrance of contaminated water or other objectionable material.
9
10 It is difficult to provide a sanitary seal for large diameter wells. Therefore, a
11 reinforced concrete slab should be installed that overlaps the casing and seals to it
12 with a flexible sealant or rubber gasket.
13
14
15 4.3.3.3 Grouting Requirements
16
17 According to Ten State Standards (2007), all permanent well casing, except driven
18 Schedule 40 steel casing with the approval of the reviewing authority, shall be surrounded by a
19 minimum of 1.5 inches of grout to a depth required by the reviewing authority. Temporary
20 construction casings need to be removed. If it is not possible or practicable to remove the
21 temporary construction casing, it has to be withdrawn by at least 5 feet to ensure grout contact
22 with the native formation.
23
24 The following types of grout mixes are recommended by Ten State Standards (2007):
25
26 Neat cement grout
27
28
29
30
31
32
33
34
- Consists of cement (conforming to ASTM standard C150) and water.
- No more than six gallons of water per sack of cement are to be added.
- Additives may be used to increase the fluidity of the grout, subject to approval by
the reviewing authority.
~>~-T
35 - Can be used for only 1.5 inch openings and not for larger openings.
^
36
37 Concrete grout
38
39
40
41
42
43
44
45
Ll^lCUC glVJUU
Equal parts of cement (conforming to AWWA A100 Section 7) and sand with no
more than six gallons of water per sack of cement may be used for openings
larger than 1.5 inches.
When an annular opening larger than four inches is available, gravel not larger
than 0.5 inch in size may be added.
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1 Clay seal
2
3 - Where an annular opening of greater than six inches is available, a clay seal of
4 local clay mixed with at least 10 percent swelling bentonite may be used when
5 approved by the reviewing authority.
6
7 Ten State Standards (2007) also stipulates that the following requirements should be met
8 prior to or during the application of the grout mix:
9
10 Sufficient annular space should be provided to permit a minimum of 1.5 inches of
11 grout around permanent casings.
12
13 Bentonite or similar materials may be added to the annular opening prior to grouting
14 through fractured geological formations.
15
16 Grout should be installed under pressure using a grout pump. When the annular
17 opening is less than four inches, the annular opening should be filled in one
18 continuous operation.
19
20 Gravity placement can be performed using a grout pipe installed at the bottom of the
21 annular opening, in one continuous operation when:
22
23 - The annular opening is four or more inches and less than 100 feet deep, and
24
25 - Concrete grout mix is being used.
26
27 A clay seal placed by gravity may be employed when the annular opening is greater
28 than six inches and less than 100 feet deep.
29
30 Work on the well should be discontinued until the cement or concrete grout sets
31 properly with no air pockets.
32
33
34 4.3.3.4 Well Screens
35
36 Screens (slotted casings) are installed in wells to permit sand-free water flow into wells
37 and to prevent unstable formations from caving in. The slot size for screens is based on a sieve
38 analysis of carefully selected samples of the water bearing formation. If the slots are too large
39 the well may pump significant quantities of sand. If the slots are too small they become easily
40 plugged with fines, which results in reduced yield. In a drilled well, the screens are normally
41 placed after the casing has been installed. However, in a driven well, the screen is a part of the
42 drive assembly and is sunk to its final position as the well is driven.
43
44 Well screen manufacturers provide tables of capacities and other information to aid in
45 selecting the most economical screen size. According to the Ten State Standards, the following
46 minimum standards are applicable to well screens:
47
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1 They should be constructed of materials that are resistant to damage by the chemical
2 action of ground water or those of cleaning operations.
3
4 Their installation should ensure that the pumping water level remains under the
5 screen for all operating conditions.
6
7 Where applicable, they should be designed and installed to allow easy removal and
8 replacement without adversely impacting water-tight construction of the well.
9
10 They should be provided with a bottom plate or washdown bottom fitting of the same
11 materials as the screen.
12
13
14 4.3.3.5 Well Development
15
16 Before a well becomes operational, it is essential to remove all the silt and fine sand next
17 to the well screen by employing a process called "well development." Development unplugs the
18 formation and produces a natural filter of coarser and more uniform particles of high
19 permeability surrounding the well screen (Purdue Research Foundation, 2001). After
20 development is completed, a well-graded, stabilized layer of coarse material will enclose the
21 entire well screen and facilitate the flow of water into the well. Surging and high-velocity
22 hydraulic jetting are two common methods for conducting well development and are described
23 below.
24
25 Surging
26
27 This process agitates the silt and sand grains by a series of rapid reversals in the direction
28 of water flow, which cause the silt and sand grains to be drawn toward the screen through larger
29 pore openings. One method of surging a well is to move a plunger up and down the well,
30 resulting in water moving in and out of the formation alternately. When water containing the
31 fines flows into the well the particles settle into the bottom of the screen and are then removed
32 by pumping or bailing. (Purdue Research Foundation, 2001)
33
34 High-Velocity Hydraulic Jetting
35
36 Water under high pressure is ejected through the slot openings and violently agitates the
37 aquifer material. Sand grains finer than the slots move through the screen and either settle at the
38 bottom or are washed out to the top. Water pressures in the vicinity of 150 psi are required.
39 High-velocity jetting is most useful for screens having continuous horizontal slot design. It is
40 also effective in washing out drilling mud and crevice cuttings in hard-rock wells. However, it is
41 less useful for slotted or perforated pipes.
42
43
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1 4.3.3.6 Testing Wells for Yield and Drawdown
2
3 A pumping test should be performed on a developed well to determine its yield and
4 drawdown. The results of a pumping test can help select what type of pumping equipment should
5 be used. The pumping test should include the following (Purdue Research Foundation, 2001):
6
7 Volume of water pumped per minute or hour;
8
9 Depth to the pumping level as determined over a period of time at one or more
10 constant rates of pumping;
11
12 Recovery of water level after pumping is stopped; and
13
14 Length of time the well is pumped at each rate during the test procedure.
15
16 According to Ten State Standards (2007), yield and drawdown tests need to be performed
17 on every production well after construction and prior to the placement of the permanent pump.
18 Test methods should be clearly indicated in the project specifications. The test pump capacity at
19 maximum anticipated drawdown should be at least 1.5 times the quantity anticipated. The yield
20 and drawdown tests should provide for continuous pumping for at least 24 hours at the design
21 pumping rate or until stabilized drawdown has continued for at least six hours when pumped at
22 1.5 times the design pumping rate. There may also be State requirements for testing and
23 stabilization. Ten State Standards (2007) recommends that the following data be provided by
24 any yield/drawdown test:
25
26 Test pump capacity-head characteristics;
27
28 Static water level;
29
30 Depth of test pump setting;
31
32 Start and end time of each test cycle; and
33
34 Zone of influence of the well.
35
36 The test should also provide hourly readings of the following parameters:
37
38 Pumping rate,
39
40 Pumping water level,
41
42 Drawdown, and
43
44 Water recovery rate and levels.
45
46 When testing a well for yield and drawdown, it is best to test it near the end of the dry
47 season. When this cannot be done it is important to estimate the additional seasonal decline in
48 water levels from wells tapping the same formations. This additional drawdown should be added
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1 to the drawdown determined by the pumping test in order to arrive at the maximum pumping
2 water level. Additional information regarding testing wells for yield and drawdown can be
3 obtained from the United States Geological Survey (USGS), the State health department, and
4 manufacturers of well screens and pumping equipment.
5
6
7 4.3.4 Disinfection of Newly Constructed Wells
8
9 All newly constructed wells should promptly be disinfected to destroy disease-causing
10 microorganisms that may have been introduced into the well during construction, hookup,
11 maintenance, or as a result of faulty well construction. The system should follow all applicable
12 State requirements and can also consult AWWA standard C-654-03 for well disinfection.
13
14 All elements of the well should be disinfected including the gravel pack, casing, and
15 pump. Disinfection can be performed using liquid chlorine, sodium hypochlorite, or calcium
16 hypochlorite. If liquid chlorine is used it should conform to ANSI/AWWA standard B301. If
17 hypochlorite is used it should conform to ANSI/A WWA standard B300.
18
19 Similar to the shock chlorination procedures discussed in Chapter 3 (section 3.1.3.4), the
20 following procedures for disinfecting newly constructed wells (AWWA 2003) can be followed
21 to disinfect the well and its components. Individual States may have standards which deviate
22 from these and should be consulted prior to performing any disinfection.
23
24 To disinfect the gravel pack, one quarter to one half a pound of calcium hypochlorite
25 tablets can be mixed per ton of gravel prior to the gravel being placed. Care should be taken to
26 ensure that the gravel is free from organic material. Alternatively, chlorinated water can be
27 added to the well after the gravel is in place and the drilling mud has been displaced.
28 Chlorinated water should be added until the concentration is 50 mg/L or greater throughout the
29 entire volume of the well.
30
31 Equipment such as pumps, meters, and valves should be disinfected just prior to
32 installation by spraying with a solution containing at least 200 mg/L of chlorine.
33
34 The procedure to disinfect the well after all the components have been installed is as
35 follows (AWWA, 2003):
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1 Add chlorine until the water throughout the well volume is 50 mg/L or greater. If
2 calcium hypochlorite is used it can be dribbled down the casing vent. Sodium
3 hypochlorite should be pumped using a tube down the casing vent to the bottom of
4 the well.
5
6 Surge the well at least 3 times to provide mixing.
7
8 Leave the chlorine solution in contact with the well for 12 to 24 hours.
9
10 Establish at least a 2 inch pressure tight connection from the pump discharge piping
11 to the casing vent.
12
13 Operate the pump against a throttled discharge valve to return several hundred
14 gallons per minute flow to the casing vent, not to exceed one half the well's capacity,
15 while the rest is discharged to waste. Be sure the throttle is not so extensive as to
16 cause damage to the well or piping.
17
18 Continue the discharge until no chlorine residual is detected for at least 15 minutes.
19
20 After there is no detectable residual, the well should be tested for coliform bacteria.
21 If coliform bacteria are detected, the well should be pumped for another 15 minutes
22 and re-sampled. If still positive for bacteria it must be re-disinfected or undergo
23 corrective action to correct the contamination source.
24
25
26 4.4 Switching to a Surface Water Source
27
28 It may become necessary for a utility to switch to a surface water source if alternate
29 reliable and safe ground water sources are not available. In comparison to ground water sources,
30 additional factors must be considered when selecting and using surface water as a supply source,
31 since surface waters are usually not as clean as most ground waters. Alternatively, a water
32 system can also consider adding surface water treatment or other treatment equipment to the
33 existing impaired well instead of switching completely to surface water.
34
35
36 4.4.1 Requirements for Treating Surface Water
37
38 Surface waters are open to chemical and microbial contamination and must be treated
39 before serving to the public. Utilities using surface water sources must comply with the
40 provisions of the Surface Water Treatment Rule (SWTR) and Interim Enhanced Surface Water
41 Treatment Rule (IESWTR), as well as Long Term 1 Enhanced Surface Water Treatment Rule
42 (LT1) and Long Term 2 Enhanced Surface Water Treatment Rule (LT2). As a result, switching
43 to a surface water source may not be economically practical. Some SWTR provisions are:
44
45 The system must demonstrate that existing treatment is capable of removing or
46 inactivating at least 99.9 percent of Giardia lamblia cysts and 99.99 percent of
47 viruses and removing 99 percent ofCryptosporidium. Additional Cryptosporidium
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1 removal or inactivation may be required under the LT2 rule.
2
3 All systems will be required to disinfect and may also be required to filter if certain
4 source water quality criteria and site-specific conditions are not met.
5
6 Comply with standards that determine if treatment (including turbidity removal and
7 disinfection) is adequate for filtered systems.
8
9 All systems must be operated by qualified personnel as determined by the individual
10 States.
11
12 Systems using surface water sources must file reports with the States to demonstrate
13 compliance with treatment and monitoring requirements.
14
15 A source water protection plan for continued protection of the watershed from potential
16 sources of contamination is also required in many States. According to Ten State Standards
17 (2007) a sanitary survey shall be made of the factors that affect water quality. Such a survey,
18 among other things, should include:
19
20 Assessing all point and non-point sources of water pollution and activities that could
21 affect water supply. The location of each waste discharge should be shown on a scale
22 map.
23
24 Determining degree of control of watershed by owner.
25
26 Ground water systems switching to an alternate surface water source often require large
27 investments in modifying their relatively less complex treatment trains and setting up additional
28 unit processes (along with the necessary instrumentation, controls, and monitoring systems).
29
30
31 4.4.2 Selecting a Surface Water Source
32
33 Surface water sources include rainwater catchments, ponds or lakes, and surface streams.
34 In areas where ground water is inaccessible or too highly mineralized for domestic use,
35 controlled catchments and cisterns may be necessary. A control catchment is a defined surface
36 area from which rainfall runoff is collected. The collected water is then stored in a constructed
37 covered tank called a cistern or a reservoir.
38
39 A pond or a lake should be considered a water supply source only if ground water
40 sources and controlled catchment systems are inadequate or unacceptable. Careful consideration
41 of the location of the watershed and pond site reduces the possibility of contamination. If
42 considering using a lake as a source (or in some cases, a pond), water systems should consult
43 their primary agency.
44
45 Stream intakes should be located upstream of sewer outlets and other sources of
46 contamination. Data indicate that flowing streams are more likely to be microbiologically
47 contaminated than reservoirs and lakes (Information Collection Rule (ICR) Water Quality Data).
48
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1 The following guidance manuals discuss surface water treatment in more detail:
2
3 Surface Water Treatment Rule Guidance Manual (AWWA, 1991),
4
5 Long Term 1 Enhanced Surface Water Treatment Rule Implementation - Turbidity
6 Provisions Technical Guidance Manual (USEPA, 2004), and
7
8 Guidance Manual for Compliance with the Interim Enhanced Surface Water
9 Treatment Rule: Turbidity Provisions (USEPA, 1999a).
10
11
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1 5. Installing Treatment
2
3 Ground water systems that choose to install treatment to correct significant deficiencies
4 or fecal contamination must provide at least 99.99 percent (4-log) inactivation (disinfection) or
5 removal (filtration) of viruses. EPA has determined that the treatment technologies or
6 combination of technologies that have demonstrated the ability to achieve 4-log inactivation of
7 viruses are chlorine (chlorine gas or hypochlorite), chlorine dioxide, ozone, ultraviolet (UV)
8 radiation, anodic oxidation, reverse osmosis (RO), and nanofiltration (NF). Though these last
9 two, RO and NF, are filtration methods that have demonstrated the ability to remove 4-log of
10 viruses (AWWA, 1990b; USEPA, 2006b; USEPA, 2006c), these technologies will have different
11 impacts on cost, operation, maintenance, and reporting requirements for systems. Selecting the
12 most appropriate treatment technology (or combination of technologies) to achieve 4-log
13 treatment is a site-specific decision best left to utility personnel and State agencies.
14
15 Americans expect tap water to be available at reasonable costs, with minimal to no
16 associated health risks. In some cases, however, those served by small systems may face
17 significantly higher per capita costs both to install and operate new treatment and to employ
18 qualified operators needed to ensure compliance with drinking water standards than the per
19 capita costs for those served by larger systems.
20
21 Small systems should exhaust all possible options (including switching to higher quality
22 source water such as another ground water well or a surface water source) before installing new
23 technologies. Purchasing water from another system is another potentially lower cost option for
24 small systems. If full water treatment is necessary, a package treatment plant may be a lower-
25 cost option. In general, disinfection technology designs are readily available without need for
26 pilot studies prior to installation. The effectiveness of disinfection systems is based on
27 laboratory results that are applicable to all systems.
28
29 This chapter describes the types of treatment that can be used to achieve 4-log
30 inactivation or removal of viruses. It is organized in three main sections:
31
32 Chemical disinfection (Section 5.1);
33
34 UV light disinfection (Section 5.2); and
35
36 Membrane technologies-filtration (Section 5.3).
37
38 This chapter provides an overview discussion of each treatment technology along with
39 advantages and disadvantages of each to help systems and States with the selection process. In
40 addition, Section 5.4 provides a list of additional references where systems and States can find
41 more detailed information.
42
43 GWSs that install disinfection or filtration treatment must demonstrate (through
44 compliance monitoring as specified in 40 CFR 141.403(b) of the GWR), that their treatment
45 reliably and effectively achieves 4-log virus inactivation, removal, or a State-approved
46 combination of inactivation and removal before or at the first customer. Existing GWSs that
47 provide such 4-log treatment and want to avoid triggered source water monitoring must notify
48 the State in writing of their treatment status by December 1, 2009, and include engineering,
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1 operational, or other information requested by the State to evaluate the submission. GWSs with
2 a new ground water source going into service after November 30, 2009, that provide 4-1 og
3 treatment must also notify the State in writing to that effect (and also include engineering,
4 operational, or other information requested by the State to evaluate the submission). GWSs with
5 new ground water sources that are disinfected must initiate compliance monitoring within 30
6 days of placing the source in service.
7
8 The requirements for systems choosing to conduct compliance monitoring or required to
9 conduct compliance monitoring vary depending on the type of treatment provided and, for those
10 systems using chemical disinfection, the size of the system. In addition, the exact treatment
11 technique standards (e.g., disinfectant concentration level) will be defined by each State and may
12 differ significantly from State to State.
13
14 GWSs using chemical disinfection must maintain the State-determined residual
15 disinfectant concentration every day the system serves water from the ground water source to the
16 public. Disinfectant residual monitoring must be conducted in accordance with 40 CFR 141.74
17 (a)(2):
18
19 GWSs serving more than 3,300 people and using chemical disinfection must monitor
20 the residual disinfectant concentration continuously at a location approved by the
21 State. Systems doing continuous monitoring must record the lowest residual
22 disinfectant concentration each day. If there is a failure in the continuous monitoring
23 equipment, the system must conduct grab sampling every four hours until the
24 equipment is returned to service. Continuous monitoring must resume within 14
25 days.
26
27 GWSs serving 3,300 or fewer people and using chemical disinfection must either take
28 a daily grab sample during the hour of peak flow (or at another time specified by the
29 State) or monitor the residual disinfectant concentration continuously. For systems
30 taking grab samples, if a daily grab sample is below the State-determined residual
31 disinfectant concentration, the system must take follow-up samples every four hours
32 until the residual disinfectant concentration is restored to the State-determined level.
33
34 A GWS that uses membrane filtration to achieve 4-log virus removal must monitor and
35 operate the membrane process in accordance with all State-specified requirements. The system
36 is in compliance if:
37
38 1. The membrane has an absolute MWCO (or an alternate parameter describing the
39 membrane's exclusion characteristics) that can reliably achieve 4-log removal of
40 viruses;
41
42 2. The membrane process is operated in accordance with State-Specified compliance
43 requirements; and
44
45 3. The integrity of the membrane is intact.
46
47 A GWS that uses an alternative State-approved treatment (i.e., other than chemical
48 disinfection or membrane filtration) must monitor and operate the alternative treatment in
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1 accordance with State-specified requirements that the State determines are necessary to achieve
2 at least 4-log virus inactivation, removal, or a combination of inactivation and removal before or
3 at the first customer.
4
5
6 5.1 Chemical Disinfection
7
8 Chemical disinfection of viruses involves maintaining a certain disinfectant concentration for
9 a period of time. Desirable properties for a chemical disinfectant include:
10
11 High germicidal power,
12
13 Stability,
14
15 Solubility,
16
17 Non-toxicity to humans and other animals,
18
19 Dependability,
20
21 Residual effect,
22
23 Ease of use and measurement,
24
25 Availability, and
26
27 Low cost.
28
29 In general, the level of inactivation depends on water quality parameters such as temperature,
30 pH, and TOC.
31
32 The CT value is the residual disinfectant concentration (in milligrams per liter (mg/L))
33 multiplied by the contact time (the time in minutes it takes the water to move between the point
34 of disinfectant application and a point downstream before or at the first customer during peak
35 hourly flow) (AWWA 1991). The system compares the CT value achieved to the published CT
36 value for a given level of treatment to determine the level of treatment attained. As long as the
37 CT value achieved by the system meets or exceeds the CT value needed for 4-log inactivation or
38 removal of viruses, the system meets the treatment technique requirement of the GWR. Exhibit
39 5.1 presents the required CT values identified by the SWTR that achieve 2-, 3-, and 4-log
40 inactivation of viruses with chlorine. Note that much higher CTs are required to achieve 4-log
41 inactivation at pH 10 than at pH 6 to 9.
42
43
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1
2
Exhibit 5.1 CT Values for Inactivation of Viruses by Free Chlorine (mg-min/L)
Temperature
(°C)
0.5
5
10
15
20
25
Log Inactivation1
2.0
pHG-9
6
4
3
2
1
1
pH10
45
30
22
15
11
7
3.0
pHG-9
9
6
4
3
2
1
pH10
66
44
33
22
16
11
4.0
pHG-9
12
8
6
4
3
2
pH10
90
60
45
30
22
15
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
Presents data for inactivation of Hepatitis A virus (HAV) at pH = 6 - 9, and 10 and temperature = 0.5, 5, 10, 15, 20,
and 25 degrees centigrade (°C). CT values include a safety factor of 3. To adjust for other temperatures, simply
double the CT value for each 10°C drop in temperature.
Sources: AWWA, 1991
The Guidance Manual for Compliance with the Filtration and Disinfection Requirements
for Public Water Systems Using Surface Water Sources (AWWA 1991) presents a detailed
description of the application of the CT concepts to disinfection practices.
In addition to inactivation of viruses and harmful microbes, chemical disinfection serves
other useful purposes in water treatment including:
Taste and odor control;
Prevention of algal growths;
Maintenance of clean media filter;
Removal of iron and manganese;
Destruction of hydrogen sulfide;
Bleaching of certain organic colors;
Maintenance of distribution system water quality;
Restoration and preservation of pipeline capacity; and
Restoration of well capacity, water main sterilization.
Chemical disinfection technologies discussed in this chapter include chlorine (applied in
the form of chlorine gas or hypochlorite solution), chlorine dioxide, and ozone. The most
commonly used disinfectants in small systems are chlorine gas or hypochlorite solution.
5.1.1 Temporary Hypochlorination
If a system is found to have a significant deficiency or fecal contamination, it may take
time for the system to design and install a corrective action. In the meantime, the system should
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1 not serve the contaminated water to its customers. The Primacy Agency may require the system
2 to apply 4-log virus disinfection until the contamination is eliminated or a corrective action is put
3 in place. For most applications, hypochlorination should be used because it is easier to install
4 and operate than gaseous chlorination or other disinfection methods and is the least costly of the
5 treatment methods. Although hypochlorination may be a viable temporary solution, systems
6 should remember that there is an ongoing cost of operation, maintenance, and reporting for water
7 that remains unsafe, so eliminating contamination or completing a corrective action as soon as
8 possible is recommended.
9
10
11 5.1.2 Chlorine Gas
12
13
14 5.1.2.1 Background
15
16 Disinfection using chlorine gas is less common at water utilities than in the past, but is
17 still widely used. This process involves the addition of elemental chlorine (Cb) to the water
18 supply at one or more locations within the treatment train. Elemental chlorine is typically
19 supplied as a liquefied gas. It comes in high-pressure containers that typically weigh between
20 100-2000 Ibs.
21
22 Onsite generation of chlorine gas has recently become practical. Chlorine gas can be
23 generated by a number of processes including the electrolysis of alkaline brine or hydrochloric
24 acid, the reaction of sodium chloride and nitric acid, or the oxidation of hydrochloric acid.
25 About 70 percent of the chlorine produced in the United States is manufactured from the
26 electrolysis of salt brine and caustic solution in a diaphragm cell (White, 1999).
27
28 Although it is extensively used for many purposes, there are some safety and security
29 issues associated with the use of chlorine gas. Facilities storing more than 1,500 pounds of
30 chlorine are subject to the Process Safety Management standards regulated by the Occupational
31 Safety and Health Administration under 29 CFR 1910 and the Risk Management Program Rule
32 administered by EPA under Section 112(r) of the Clean Air Act. All of these regulations (as well
33 as local and State codes and regulations) should be considered during the design and operation of
34 chlorination facilities at a water treatment plant. Systems should have their own safety
35 equipment and operators should take the following precautions when using or handling chlorine
36 gas:
37
38 Chlorine gas is poisonous and corrosive; therefore, adequate exhaust and ventilation
39 should be used when applying chlorine for water treatment. The ventilation should be
40 positive at the floor level because chlorine gas is heavier than air. Operators should
41 wear proper personal protective equipment including goggles, gloves, and respirators.
42 Each operator should also have access to a self-contained breathing apparatus.
43
44 Liquid and gaseous chlorine must be delivered using rubber lined or polyvinyl
45 chloride (PVC) piping with hard rubber (using rubber lined or PVC piping will
46 increase the life of the piping system and decrease maintenance costs).
47
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1 Cylinders should be placed on platform scales that are flush with the floor and
2 continuously monitored for leaks. Loss of weight of the cylinders should be directly
3 recorded as chlorine dosage.
4
5
6 5.1.2.2 System Design
7
8 The design criteria for chlorine disinfection usually encompass a variety of factors to
9 ensure proper chlorine dose application. Some of these factors are chlorine gas application (gas
10 delivery), contact time, contact tank design, contact tank baffling, and residual effluent water
11 concentrations.
12
13 The chlorinator is a supply-metering device for chlorine gas controlled by regulated
14 pressure and/or variable orifices. The chlorine feed rate can be manually or automatically
15 regulated. It is also convenient to use an electronic or mechanical scale to measure the chlorine
16 gas usage. A scale will allow the system to determine a cylinder's content level. Scales are
17 intended for use in chlorination and other gas feeding applications and can be used to measure
18 liquefied chlorine, sulfur dioxide, ammonia, hydrogen chloride, or carbon dioxide packaged in
19 cylinders. Small systems may choose to use manual chlorination to control chlorine dosage.
20
21 Since chlorine is hazardous and corrosive, systems should store chlorination equipment
22 away from other treatment facilities and chemicals.
23
24 Contact time, contact tank design, and baffling are all interrelated in the area of chlorine
25 gas treatment of the finished water supply. All of these areas of scenario design are important in
26 ensuring that the chlorine gas is allowed adequate contact time with the contaminated water in
27 order to inactivate viruses and other microorganisms. When chlorine is added to the water
28 supply, it reacts with other chemicals in the water (e.g., iron, manganese, hydrogen sulfide, and
29 ammonia) and is not fully available for disinfection. The amount of chlorine that reacts with the
30 other chemicals plus the amount required to achieve disinfection represents the chlorine demand
31 of the water. Chlorine demand may change with dosage, time, temperature, pH, and nature and
32 amount of the impurities in the water. The chlorine dose (in mg/L) is the amount of chlorine
33 added to satisfy the chlorine demand and provide a free chlorine residual up to the end of the
34 contact period:
35
36 Chlorine dose = chlorine demand + free available residual chlorine (the "C" in "CT")
37
38 Within the distribution system, free chlorine residuals range from 0.2 mg/L to as high as
39 3-3.5 mg/L in some systems. Most US systems maintain a chlorine residual above 0.2 mg/L in
40 the distribution system (AWWA, 1990b). Systems experiencing high levels of disinfection
41 byproducts (DBFs) in their distribution systems should work with the state or their engineer to
42 identify compliance options. See the Simultaneous Compliance Guidance Manual (USEPA,
43 2007a) for more information.
44
45
46 5.1.2.3 Operation and Maintenance
47
48 Normal operation of gas chlorination includes both routine observation and preventive
49 maintenance. On a daily basis the operator should:
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1
2 Read the chlorination rotameter;
3
4 Record the reading time, date, and initial entries;
5
6 Read flow meters and record the number of gallons of water pumped;
7
8 Check the chlorine residual and increase or decrease the chemical feed rate of the
9 chlorine gas; mixture based on the residual concentration; and
10
11 Calculate and record the chlorine usage.
12
13 On a weekly basis the operator should:
14
15 Clean all of the equipment and the chlorine storage and housing area; and
16
17 Perform any necessary preventive maintenance on the application equipment and
18 piping.
19
20
21 5.1.2.4 Advantages and Disadvantages
22
23 Chlorine has many attractive features that contribute to its wide use in the industry. The
24 use of chlorine gas is highly advantageous because it is readily available. There is an abundance
25 of chlorine gas for continuous plant operation without any significant chemical mixing, which
26 makes the process much easier to apply. Chlorine leaves a residual that is easily measured and
27 controlled. Chlorine is also economical and has an excellent track record of successful use in
28 improving water treatment operations.
29
30 There are also disadvantages in using chlorine as a disinfectant. The use of chlorine
31 promotes the formation of chlorinated organic compounds, such as trihalomethanes (THMs),
32 which are potentially harmful to humans. CWSs and NTNCWSs must comply with DBF MCLs
33 and monitoring requirements if chlorine or other disinfectants are used. In addition, high
34 chlorine doses can cause taste and odor problems.
35
36 Chlorine gas has specific hazards associated with its use or misuse and requires special
37 handling and response programs. Chlorine gas combines with the mucous membranes in the
38 nose and throat, as well as the fluids in the eyes and lungs, irritating and inflaming those areas.
39 Therefore, a very small percentage of chlorine gas in the air can irritate the lungs and cause
40 severe coughing; heavy exposure can be fatal (White, 1999). Systems should ensure that safety
41 equipment (e.g., eye wash, shower, chlorine gas detectors) is routinely available, routinely check
42 for leaks in the chlorine cylinders, and routinely clean interior parts of the gas chlorination
43 system. For emergency purposes, self-contained breathing apparatuses should be available
44 outside the chlorine gas cylinder storage area.
45
46
47 5.1.3 Hypochlorite
48
49
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1 5.1.3.1 Background
2
3 Many properties of hypochlorite are similar to those of chlorine gas as far as oxidizing
4 principles and corrosiveness of the substance; however, since storage of hypochlorite is generally
5 safer than storage of chlorine gas, many small systems choose to use hypochlorination instead of
6 gaseous chlorination to treat their drinking water. Hypochlorite compounds are non-flammable;
7 however, they can cause fires when they come in contact with certain organic compounds or
8 easily oxidizable substances. If a spill occurs, then it should be washed with a large amount of
9 water and cleaned up immediately. Skin contact with hypochlorite can burn the skin and may
10 cause damage to the eyes.
11
12 Systems typically use either sodium hypochlorite (NaHOCl) or calcium hypochlorite
13 (CaHOCl). Sodium hypochlorite, which is produced when chlorine gas is dissolved in a sodium
14 hydroxide solution, is most commonly used in aqueous form. Calcium hypochlorite, which is
15 formed from the precipitate that results from dissolving chlorine gas in a solution of calcium
16 oxide (lime) and sodium hydroxide, is more commonly used in dry solid form (White, 1999).
17
18 Sodium hypochlorite is available in concentrations of 5 to 15 percent, and typically
19 contains 12.5 percent available chlorine (White, 1999). One gallon of 12.5 percent sodium
20 hypochlorite solution typically contains the equivalent of one pound of chlorine. Sodium
21 hypochlorite (commonly referred to as liquid bleach or Javelle water) can be purchased in bulk
22 quantities ranging from 55-gallon drums to 4,500-gallon truckloads. Bulk loads can be stored in
23 fiberglass or plastic tanks. The stability of the sodium hypochlorite solution depends on
24 hypochlorite concentration, storage temperature and duration, impurities of the solution, and
25 exposure to light. Decomposition of hypochlorite over time can affect the feed rate and dosage,
26 as well as produce undesirable byproducts such as chlorite ions or chlorate (Gordon et al., 1995).
27 Because of these storage problems and high transport cost, many systems are investigating onsite
28 generation of hypochlorite instead of purchasing it from a manufacturer or vendor (USEPA,
29 1998).
30
31 Calcium hypochlorite has a high oxidizing potential and typically comes in the powdered
32 form of high-test hypochlorite (HTH). Calcium hypochlorite also comes in tabular and granular
33 forms containing at least 65 percent available chlorine and dissolves easily in water (USEPA,
34 1991). This means that 1.5 pounds of calcium hypochlorite contains the equivalent of one pound
35 of chlorine. Similar to sodium hypochlorite solution, the addition of calcium hypochlorite to
36 water yields hydroxyl ions that will increase the pH of the water. One option for continuous
37 chlorination is the use of HTH tablet erosion feeders. These are devices containing HTH tablets.
38 As water feeds through the device, the HTH erodes and dissolves it into solution, which is then
39 reintroduced to the raw water.
40
41 Calcium hypochlorite is stable under proper storage and is therefore favored for most
42 hypochlorite disinfection schemes. Calcium hypochlorite should be stored in a cool dry location
43 in corrosion-resistant containers away from heat sources or organic materials such as wood,
44 cloth, and petroleum products (USEPA, 1998).
45
46
47 5.1.3.2 System Design
48
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1 The application of hypochlorite in potable water achieves the same result as chlorine gas.
2 Therefore, similar contact times and concentrations are used in design (White, 1999). Systems
3 apply hypochlorite by injecting a stock solution into the water supply using chemical metering
4 pumps (hypochlorinators). Typically, positive displacement meters and pumps are employed as
5 feed mechanisms for hypochlorite. These types of hypochlorinators are designed to pump an
6 aqueous chlorine solution into the water being pumped and treated and are usually available at a
7 modest price. These pumps are typically designed to operate against pressures up to 100 psi but
8 can also be used to inject chlorine on the suction side of the pump. These pumps are quite
9 accurate and have been found to maintain a constant dose as long as the water flow is relatively
10 constant. If this is not the case, a metering device is placed on the pump to vary the dosage in
11 conjunction with the flow rate of the water being treated.
12
13
14 5.1.3.3 Operation and Maintenance
15
16 In general, hypochlorination facilities are easier to operate than gas chlorination facilities.
17 Operation and maintenance (O&M) costs include daily, weekly, and monthly operations,
18 preventive maintenance, and personnel training and certification. Activities regularly conducted
19 at hypochlorination facilities are listed below.
20
21 On a daily basis the operator should:
22
23 Read and record the level of the solution tank at approximately the same time
24 everyday;
25
26 Read meters and record the amount of water pumped;
27
28 Check the free chlorine residual and adjust as necessary; and
29
30 Observe chemical pump operation by reading the dial that indicates chlorine feed
31 rate. The pump should be operated in the upper ranges of the dial for optimum
32 performance. Also, frequency of piston or diaphragm strokes should be such that
33 hypochlorite is constantly being supplied to the water that is being treated.
34
35 On a weekly basis the operator should:
36
37 Clean the building and all application equipment; and
38
39 Replace chemicals and wash all chemical storage equipment.
40
41 On a monthly basis the operator should:
42
43 Check the operation of all delivery equipment and examine all safety devices such as
44 check valves and backup power devices; and
45
46 Perform all preventive maintenance on system, and check for leaks and corrosion.
47
48 Small system hypochlorinators typically have a limited number of repairable parts.
49 Therefore, it is often advisable to replace all essential parts at the time of any single part failure.
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Minor maintenance, such as oil changes and lubrication of all moving parts, can significantly
increase the life span of small system hypochlorinators.
5.1.3.4 Advantages and Disadvantages
Hypochlorite has many of the same advantages and disadvantages of gaseous chlorine as
described in Section 5.1.1.4, including DBF compliance requirements for CWSs and NTNCWSs.
However, hypochlorite may be more advantageous than chlorine for small systems because spills
and leaks of hypochlorite can be more easily managed and contained than chlorine gas leaks.
Additional advantages and disadvantages associated with the use of hypochlorite are discussed
below.
Sodium hypochlorite is easier to handle than chlorine gas or calcium hypochlorite,
however, it is very corrosive and should be stored with care and kept away from equipment that
can be damaged by corrosion. It also must be stored in a cool, dark, and dry area and cannot be
stored longer than one month.
Calcium hypochlorite is very stable when properly packaged and can be stored up to a
one year. Since it is a corrosive material with a strong odor, it must be properly handled and
stored. Reactions with organic material can generate enough heat to cause an explosion. Since it
readily absorbs moisture, forming chlorine gas, shipping containers must be emptied completely
or carefully resealed. Also, using calcium hypochlorite in dust form requires dust control
practices to guard against breathing the dust and minimizing skin exposure.
5.1.4 Chlorine Dioxide (ClOi) Disinfection
5.1.4.1 Background
Chlorine dioxide is one of the most powerful oxidizing agents used for water treatment.
It is also used to control taste and odor, iron, manganese, hydrogen sulfide, and phenolic
compounds. The SWTR Guidance Manual (AWWA, 1991) provides CT values for inactivation
of viruses as shown in Exhibit 5.2.
Exhibit 5.2 CT Values (mg-min/L) for Inactivation of Viruses1 by Chlorine Dioxide
for pH 6 to 9
Inactivation
2-Log
3-Log
4-Log
Temperature
<1°C
8.4
25.6
50.1
5°C
5.6
17.1
33.4
10°C
4.2
12.8
25.1
15°C
2.8
8.6
16.7
20°C
2.1
6.4
12.5
25°C
1.4
4.3
8.4
41
42
43
44
1 Studies pertain to the Hepatitis A virus.
Sources: AWWA, 1991
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1 Chlorine dioxide is a highly unstable material and is typically generated onsite for the
2 disinfection of water. Chlorine dioxide gas is yellow/red, has a noticeable odor, and is more
3 explosive than in the liquid form.
4
5 It exists in solution without the need for hydrolysis and disinfects by oxidation, not by
6 chlorination. Since free chlorine species are not the reactants, the production of THMs in the
7 distribution system are highly unlikely; however, total organic halogen (TOX) may be produced.
8 Waters with high alkalinity reduce the yield and effectiveness of chlorine dioxide by reducing
9 the oxidation-reduction potential and give rise to potentially harmful byproducts.
10
11
12 5.1.4.2 System Design
13
14 Chlorine dioxide is most frequently generated using aqueous sodium chlorite solution
15 (White 1999). Sodium chlorite is used in the liquid or solid form along with a high level acid
16 mixture to create chlorine dioxide that is used to treat the influent water. The formation reaction
17 for chlorine dioxide is more effective at a lower pH.
18
19 If mixed properly, the production of chlorine dioxide will generate a 95 percent yield
20 with no more than 5 percent excess chlorine in the effluent. If this is the case, there is minimal
21 potential for THM and haloacetic acid (HAA) formation in the effluent plant flow.
22
23
24 5.1.4.3 Operation and Maintenance
25
26 O&M of a chlorine dioxide generation system requires significant knowledge of the
27 system. Therefore, it is important have highly trained personnel operating and maintaining
28 sodium chlorite storage and feed systems and chlorine dioxide generator and feed equipment.
29 Chlorine dioxide generation requires constant monitoring and tweaking of the chlorine dioxide
30 production amount, based on any changes in the original amount of water being treated and the
31 flow rate of the water being treated. Also, the volatility of the chlorine dioxide generation
32 process, which can create a risk of explosion, must be taken into account when working with
33 chlorine dioxide generation.
34
35 On a daily basis, operators should adjust flow meters and rotameters that control all gas
36 flow within the plant. Also, constant monitoring of all delivery equipment must take place to
37 ensure the highest amount of chlorine dioxide yield efficiency. For example, operators should
38 take measures to prevent crystallization (that can go through the pipes and plug valves and
39 generator equipment) or stratification (i.e., more dense material shifts to the bottom of the bulk
40 (storage) tank causing an inappropriate level of feed) of sodium chlorite. Operators must be
41 trained in the areas of equipment calibration as well as start-up and shut-down procedures for the
42 plant in the event of an emergency. Proper calibration of all application equipment keeps the
43 cost of operation down as well.
44
45
46 5.1.4.4 Advantages and Disadvantages
47
48 Systems have found that there are many advantages to using chlorine dioxide to disinfect
49 water supplies. Chlorine dioxide is more effective than chlorine for inactivation ofGiardia and
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1 Cryptosporidium. Also, it does not react with ammonia or nitrogen to form unpleasant tastes and
2 odors or react with any oxidizable materials that aid in the formation of THMs and HAAs. In
3 fact, chlorine dioxide destroys as much as 30 percent of all DBF precursors allowing free
4 residual chlorination to be used without the production of unwanted THMs and HAAs within the
5 distribution system (Lagerquist et al., 2004). Chlorine dioxide is also advantageous because its
6 biocidal properties are not affected by the pH at levels from 6 to 9. Chlorine dioxide is also
7 superior to chlorine in the oxidation of iron and manganese from water, and it provides a
8 residual, although the residual is limited with high levels of total organic carbon (TOC).
9
10 There are several disadvantages to chlorine dioxide use. Chlorine dioxide is not as cost-
11 effective as chlorination since the chemical cost of chlorine dioxide is several times that of
12 chlorine (White, 1999). Chlorine dioxide also forms chlorite, a regulated DBF. The MCL for
13 chlorite was set at 1.0 mg/L and the MRDL was set at 0.8 mg/L by the Stage 1
14 Disinfection/Disinfectants Byproducts Rule (D/DBPR). All systems (including transient
15 systems) using chlorine dioxide must comply with an intensive compliance monitoring schedule
16 that includes monitoring daily at the entrance to the distribution system for both chlorine dioxide
17 and chlorite. If either exceeds the federal standard, the system must collect 3 follow-up samples
18 the next day in the distribution system. They must also collect 3 chlorite samples per month in
19 the distribution system. As much as 70 percent of the chlorine dioxide added to water can break
20 down to form chlorite. This limits the dose of chlorine dioxide that can be used and therefore the
21 amount of inactivation that can be achieved.
22
23 Due to its high volatility and explosive nature, chlorine dioxide must be generated on-site
24 and cannot be transported. There are also high costs associated with containing the compound
25 and proper operator/maintenance training. Storage of the compound must be monitored very
26 carefully since chlorine dioxide decomposes in sunlight.
27
28 Additional information on advantages and disadvantages of chlorine dioxide are available
29 in the Simultaneous Compliance Guidance Manual (USEPA 2007a) and the Alternative
30 Disinfectants Guidance Manual (USEPA 1999b).
31
32
33 5.1.5 Ozone (Os) Disinfection
34
35
36 5.1.5.1 Background
37
38 Ozone is used to inactive bacteria and viruses and oxidize organic compounds in water
39 treatment plants. Ozone treatment is known to reduce problems with taste, odor, and color in
40 drinking water. Ozone is injected into the flow of the water being treated by mechanical mixing
41 devices, counter-current and co-current flow columns, porous diffusers, or jet injectors. Typical
42 ozone dosages range from 3-10 mg/L (AWWA, 1990b).
43
44 Ozone forms highly reactive and highly potent free radicals such as OH-, which are very
45 strong oxidizing species. These act quickly to inactivate bacteria and viruses. Because of its
46 quick germicidal action, ozone needs relatively short contact time to disinfect most waters,
47 provided the initial turbidity of the water being treated is low at the time of ozone addition.
48 Exhibit 5.3 provides CT values for virus inactivation by ozone.
49
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1
2
3
Exhibit 5.3 CT Values (mg of O3-min/L) for Virus Inactivation by Ozone
Inactivation
2-Log
3-Log
4-Log
Temperature
<1°C
0.9
1.4
1.8
5°C
0.6
0.9
1.2
10°C
0.5
0.8
1.0
15°C
0.3
0.5
0.6
20°C
0.25
0.4
0.5
25°C
0.15
0.25
0.3
4
5
6
1
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19
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22
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25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Sources: AWWA, 1991
Ozone is a powerful oxidant of organic materials, breaking them into smaller chain
organic molecules. These smaller chain particles, sometimes measured as AOC are an easily
degradable food source for microorganisms in the distribution system. Biological filtration
following ozonation can effectively remove these materials to create biologically stable finished
water and reduce the occurrence of microbial growth in the distribution system (USEPA 2007a).
5.1.5.2 Operation and Maintenance
The general O&M needs for an ozonation facility are labor, energy, and materials. The
three O&M cost categories are daily operation, preventive maintenance, and personnel training.
The time spent on operation activities varies by the size of the facility. Although ozone
generators are complex, they use complete automation and require modest amounts of time for
routine maintenance. Well-trained technicians require preventive maintenance and repair
training to operate the ozone generator. This includes checking the generator and keeping
system parts clean. Ozone is a strong oxidizer; therefore, the system parts require cleaning to
prevent corrosion. Parts requiring occasional cleaning are the ozone contacting unit and the
ozone exhaust gas destruction unit. Other parts for the dehumidifying process also require
cleaning and maintenance. In addition, users must clean the air preparation or oxygen feed and
dehumidify the saturated desiccant.
Ozone leaks in and around the ozone generation facility may create a health hazard to
operators of the treatment plant and may destroy or enhance the wear of other equipment
materials. Therefore, facilities must apply strict safety measures, install an ozone gas detector,
and periodically check alarms.
The materials needed to ensure the equipment functions adequately comprise the final
O&M component of the ozonation facility. Materials include cleaning chemicals, replacement
parts, and additional necessary supplies for periodic maintenance, system cleaning, and
unanticipated breakdowns.
5.1.5.3 Advantages and Disadvantages
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1
2 Ozone has powerful disinfection capabilities. Its high diffusion characteristics make it
3 one of the most efficient chemical disinfectants with its contact time of only a few minutes
4 Ozone inactivates microbes without forming chlorinated DBFs. Ozone also oxidizes iron and
5 manganese and improves the taste, odor, and color of raw water. It enhances the
6 biodegradability of natural and synthetic organic compounds and destroys many organic
7 compounds. Production of ozone from air requires no storage space for chemicals. Due to its
8 relatively short half-life and safety issues, ozone requires on-site production. Due to the
9 difficulty in determining an adequate dose, ozone is most beneficial to systems with a constant
10 demand or little demand fluctuation, such as ground water systems.
11
12 Disadvantages of ozone include its relatively high cost and complexity in its use
13 (AWWA, 1990b). Relative to other treatment technologies, ozone also requires higher skilled
14 operators. Ozone decomposes quickly in water with high pH levels (about 8-9) and therefore
15 does not provide an adequate residual to protect against recontamination in distribution or water
16 storage systems (USEP A, 1999b). Therefore, secondary disinfection may be required. If the
17 source water has a high bromide concentration, ozone can react with bromide to form bromate, a
18 regulated DBF. The Stage 1 D/DBPR requires PWSs to comply with a 10 microgram per liter
19 (ug/L) MCL for bromate. Ozonation in conjunction with chlorination could result in high
20 concentrations of brominated DBFs.
21
22 Water containing large amounts of organic matter and bromide may increase ozone
23 demand and the potential for byproduct formation. However, high natural organic matter
24 (NOM) content in raw waters is generally not an issue for most ground water systems.
25
26
27 5.2 UV Radiation Disinfection
28
29
30 5.2.1 Background
31
32 UV radiation disinfection continues to grow in popularity as new reliable equipment
33 becomes available. UV radiation is generated artificially through a wide variety of arcs and
34 incandescent lamps. Low pressure mercury-vapor lamps produce UV radiation as a result of an
35 electron flow between the electrodes in an ionized mercury vapor. The principle behind
36 inactivating microorganisms is based on photochemical reactions that take place in the
37 deoxyribonucleic acid (DNA) molecule of the microbe, disrupting the reproductive system. UV
38 radiation has proven to work well in small water treatment scenarios and has given good results
39 on the inactivation of several waterborne organisms such as Giardia, E.coli, and most recently,
40 Cryptosporidium (USEPA, 2006b).
41
42 Unlike chemical disinfection, UV leaves no residual that can be monitored to determine
43 UV dose and inactivation credit. The UV dose depends on the UV intensity (measured by UV
44 sensors), the flow rate, and the UV transmittance (UVT)1. The very high dose requirements for
45 3- and 4-log virus inactivation have presented challenges during validation testing of UV
46 reactors (USEPA, 2006b). Exhibit 5.4 presents UV dose requirements for virus removal.
47
1 UV intensity measurements may account for UVT depending on sensor locations.
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Exhibit 5.4 UV Dose Requirements for Virus Removal (mJ/cm2)
UV Dose
Log Inactivation
1.0
58
2.0
100
3.0
143
4.0
186
Source: 40 CFR 141.720 (d)(1)
5.2.2 Inactivation Mechanism and Effectiveness
Proteins and nucleic acids absorb invisible shortwave UV light. The photochemical
changes induced by molecular absorption are very harmful to living cells. The most effective
spectral region of maximum absorption by nucleic acids lies around 254 nm (USEPA, 2006b).
UV affects the cell replication process by promoting the dimerization reaction of two thymine
nucleotides. Inhibition of replication results in inactivation and the death of cells. The
effectiveness of UV increases with decreasing cell complexity and decreasing cell wall
thickness.
5.2.3 System Design
Detailed guidance on UV system design can be found in the 2006 UV Disinfection
Guidance Manual (USEPA, 2006b). The design should include a UV reactor with accessible
modules so that maintenance of the lamps can be accomplished. The modules should include the
UV lamps encased within quartz sleeves for protection, and ballasts that control power to the UV
lamps. By isolating these portions of the UV disinfection reactor, it is easier to access the critical
parts of the UV disinfection chamber, thereby allowing for minimal off-line operation of the UV
disinfection portion of the treatment scheme. Also, the design of a UV disinfection chamber
should always contain redundant modules for proper microbial inactivation.
UV lamps emit UV light rays that pass through the quartz sleeve and into the water to be
treated. The microorganisms are inactivated by the UV radiation that transmits through the
water, into the cell, and makes contact with the microorganism DNA. As a result, the water's
turbidity and turbulence are the main factors that affect the UV transmittance through the water.
For design purposes, it is important that turbulence occurs (to allow all elements of fluid
to come sufficiently close to the lamp surfaces), but short circuiting is minimized. Turbulent
flow and the consequent good mixing helps reduce the non-uniformity of the intensity field. In
some cases, within the chamber, there are baffles that force the flowing water being treated to
travel tangentially through the chamber in a spinning motion around the quartz sleeves. This
increases the light versus water contact time and therefore increases the level of disinfection
achieved.
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1 UV has been employed in a variety of physical configurations. In two of these
2 configurations, the UV lamps are surrounded by quartz sheaths and the jacketed lamps are
3 immersed in the flowing water. In a third configuration, the water flows through Teflon tubing
4 (that is relatively transparent to UV) surrounded by UV lamps. Quartz sleeves absorb only five
5 percent of the UV radiation, while Teflon sleeves absorb 35 percent (USEPA, 1999b).
6
7 Things to consider when designing a UV disinfection system include:
8
9 Backup and existing power supply-Continuity, to ensure that there is always some
10 form of power to support the demand of the UV lamps and provide constant
11 disinfection.
12
13 UV equipment availability and reliability-What is available? Safety Tradeoffs - Is
14 UV safer to use than the current disinfection that is being used within the plant?
15
16 UV exposure indices-Is it possible to achieve the proper amount of UV exposure to
17 the water being treated, or are there factors affecting the current plant conditions that
18 make UV impossible?
19
20 Cost-Are total suspended solids, color, and turbidity a problem in the plant? If so, it
21 may not be economically wise to choose UV disinfection.
22
23
24 5.2.4 Operation and Maintenance
25
26 Operators should always wear UV filtering goggles, as well as be aware of potential
27 hazards such as skin cancer and acute eye irritations associated with UV light.
28
29 Accumulation of solids onto the surface of UV sleeves can reduce the applied UV
30 intensity and, consequently, disinfection efficacy (USEPA, 1999b). If the water being treated
31 contains biofilms and/or buildup of inorganics, the lamps are susceptible to scaling. In addition,
32 the quartz sleeves can be fouled by organic and inorganic debris in the water. Scaling and
33 fouling reduce the amount of UV radiation reaching the water. Therefore, it is important to
34 minimize inorganic and dissolved organics upstream, preventing scaling and increasing UV
35 efficacy.
36
37 The lamps should be maintained by cleaning the quartz sleeves to prevent fouling. If the
38 source water is fairly clean, the lamps need not be cleaned as often, and vice versa. Approaches
39 for cleaning include on-line mechanical cleaning, on-line mechanical/chemical cleaning, and off-
40 line chemical cleaning. On-line systems usually use wipers to remove scale from the sleeves.
41 For off-line systems, the reactor is shut down, drained, and flushed with a cleaning solution
42 (USEPA, 2006b).
43
44 One of the main operational concerns involving UV disinfection is the need for a constant
45 and reliable power source to power the ballasts. It is imperative that an alternate, dependable
46 power source be supplied to provide continuous disinfection of the water supply.
47
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1 The life expectancy of a typical UV lamp varies in the range of 4,000 to 12,000 hours
2 (USEPA, 2006b). Because lamp output decays over time, UV lamps need to be replaced
3 regularly. The replacement schedule should be based on lamp decay characteristics and the
4 guaranteed lamp life (USEPA, 2006b). Because lamps contain mercury, they are often
5 considered a hazardous waste under Subtitle C of the Resource Conservation and Recovery Act
6 (RCRA) and should be disposed of accordingly.
7
8
9 5.2.5 Advantages and Disadvantages
10
11 UV has many advantages for primary disinfection. Since there is no chemical
12 consumption, there is no need for large-scale storage facilities, transportation, or chemical
13 handling. UV requires low contact time to inactivate most microorganisms, and forms no known
14 harmful byproducts. UV disinfection is not dependent upon temperature or pH. Finally, low
15 doses of UV are effective against Giardia and Cryptosporidium.
16
17 There are, however, disadvantages to using UV radiation for ground water disinfection.
18 A UV treatment system can loose power in the event of a power interruption, voltage fluctuation,
19 or power quality anomaly. UV light also does not work significantly well within highly turbid
20 waters and cleaning costs can be significantly increased with poor source water quality. Since
21 UV radiation does not provide a residual disinfectant to prevent microbial buildup in the
22 distribution system, a secondary disinfectant may be required. Also, very high doses are needed
23 for 4-1 og inactivation of viruses. It is important to note that UV treatment alone does not meet the
24 GWR treatment requirements.
25
26
27 5.3 Membrane Filtration Technologies
28
29 For the purposes of the GWR, the term "membrane filtration technologies" includes RO
30 and NF because they can achieve 4-log removal of viruses. Ultrafiltration (UF) and
31 microfiltration (MF) are two other membrane technologies. However, these technologies are
32 incapable of achieving 4-log removal of viruses, and therefore will not be discussed further.
33 Also, bag and cartridge filters cannot achieve virus removal credit.
34
35 All membrane filtration technologies employ similar filtration mechanisms (including
36 sieving, repulsion due to like charges at the membrane/liquid interface, etc.), similar materials,
37 and similar module configurations. Their difference lies in their ability to separate particles and
38 ions of different sizes and molecular weights. Exhibit 5.5 illustrates the ability of each type of
39 membrane process to remove various drinking water contaminants based on size.
40
41 The factors affecting membrane performance include pore size, molecular weight cutoff
42 (MWCO), material and geometry, removal of targeted materials, and the quantity (and quality)
43 of the treated water. Membrane pore sizes vary with differing technologies; RO systems have a
44 smaller pore size than that of NF systems. Membrane performance is measured by recovery.
45 Recovery represents the percentage of feed converted to product:
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feed rate - brine rate
Recovery Rate = /eeJ rate x 100
1
2
3
4
I
7
Exhibit 5.5 Particle Size Removal for Various Membrane Technologies
See dim) 0.0001 0,001 0.01 0.1 1.0 10 too
Molecular Weight '
(Da tons)
Drinking Water
Pattegens
Membrane Filtration
Process
i
2C
» 20,
i
000 200
cm
Viruses
i
000
i i
| Bacteria |
tosporidium
| Qardia \
HHI
MCF
MF
| UF
i
NF
i
RO
i
Source: USEPA2005
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Generally, the higher the recovery rate, the greater the product water yield from the feed
water. Factors that determine the recovery rate are water quality and the saturation percentage of
critical membrane foulants such as calcium and barium sulfates in the concentrate.
A number of different types of membrane materials, modules, and systems are used by
different classes of membrane filtration system. In general, MF and UF systems use hollow-fiber
membranes, while NF and RO systems use spiral-wound membranes (USEPA 2005). A spiral
wound membrane consists of two flat sheets of membrane separated by a porous support.
5.3.1 Background
In drinking water applications, RO is usually employed by systems to reduce the salinity
of brackish ground water. However, it is also very effective in removing organic and dissolved
solids, bacteria, and viruses. Well maintained and properly operated RO systems can provide
complete protection against pathogens found in ground waters (AWWA, 1990b).
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
In RO, the water to be treated is forced by high pressure through the membrane (usually
cellulose acetate or aromatic polyamide) into the product water. Operation pressures vary
between 300 and 1500 psi, with atypical range of 600-800 psi (Viessman, 1998).
NF units operate under pressures between 70-150 psi and use thin film
membranes to filter particles of sizes greater than 1 nm. Typical NF systems employ an MWCO
of approximately 200 to 800 daltons, but NF membranes used for potable water applications use
MWCOs of 200 to 400 daltons (USEPA, 2005). NF systems are typically used for water
softening and removal of NOM. Because of its very small pore size, NF can remove
exceptionally high levels of microorganisms, including viruses.
5.3.2 System Design
The key components of an RO or NF plant include:
Chemical feed system for pretreatment and pH adjustment;
Cartridge filter to remove large particles (greater than 1 micron) that could potentially
foul the membrane;
Medium to high pressure booster pumps for the feed-water;
Membrane vessels; and
Disposal system for concentrate.
Exhibit 5.6 shows a schematic for a typical RO/NF treatment system
Exhibit 5.6 Schematic of a Typical RO/NF Treatment System
muooc
now
POSIW*
DQPUCQIEMT
PUMP
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1 Source: USEPA 2005
2
3
4 5.3.3 Operation and Maintenance
5
6 Operation of an RO or NF unit requires disinfecting and cleaning the membrane to
7 prevent fouling. Depending on the influent water quality, systems should clean the membrane
8 every few days to every few months. Membrane concentrates are usually discharged to:
9
10 Surface waters such as lakes, rivers, or oceans (requiring a NPDES permit);
11
12 Injection wells (under the UIC program);
13
14 Sanitary sewers (possibly requiring State or Local Permits); or
15
16 Evaporation ponds.
17
18 Federal, State, and local authorities, regulations, and permitting requirements regulate
19 disposal methods.
20
21 The feed-water supply should be checked routinely for changes in water quality (e.g.,
22 increased concentration of chemical ions like calcium that can cause scaling). Water quality
23 parameters, both chemical and biological, should be monitored and the trends charted. Silt and
24 iron oxides are common ground water contaminants. The acid injection system consisting of
25 bulk storage tanks, chemical feeders, ratio controllers, and injection lines should be routinely
26 checked for maintenance and safety related conditions. Acid quality should be verified on the
27 shipments and certified analyses reviewed. Operators should routinely calibrate and check pH
28 controllers and clean pH probes weekly.
29
30 Cartridge filter vessel drains should be flushed daily, and the pressure drop across the
31 filters should be checked and recorded. Upon filter changeout, proper seating of the cartridges
32 should be ensured (USEPA 2005). Residual particulate matter inside the cartridge filter vessel
33 should not be allowed to enter downstream piping during filter cartridge changeout. Maximum
34 flow rates per individual cartridge should not be exceeded. Membrane block feed-water, brine
35 and product conductivity, flows, pH, and pressure should be logged daily. Any unusual changes
36 in preset membrane block operating conditions may require adjustment to the system. High-
37 pressure pumps and motors require routine maintenance as recommended by the manufacturer.
38
39 All instrument systems associated with fail-safe or shutdown conditions must be kept
40 operational. Minimum spare parts inventory recommended by the manufacturer should be kept
41 at hand. The degasifier packed tower or tray aeration system requires periodic inspection and
42 cleaning. Slime buildups occur in degasifiers and require cleaning. Degasifier blowers and
43 motors require routine maintenance.
44
45
46 5.3.4 Advantages and Disadvantages
47
48 RO and NF systems are advantageous because they are extremely efficient in viruses,
49 bacteria, and DBF precursors.
June 2008 Ground Water Rule 5-20 Public Review Draft
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1
2 There are several disadvantages associated with the use of RO and NF, including the high
3 cost of the process. Both processes are highly energy-intensive and require a large amount of
4 power to sustain proper removal levels of viruses and bacteria. They also require highly skilled
5 personnel to operate and maintain the filters and to ensure that proper cleaning of the filters is
6 conducted. RO and NF do not provide any residual to control microbial regrowth in the
7 distribution system. A disadvantage of RO is that the feedwater may be wasted as brine when
8 the goal is to lower ion concentrations by reducing the permeate recovery. This is especially
9 significant in areas with limited water supplies.
10
11
12 5.4 Additional Resources
13
14 More detailed guidelines can be found in other publications, including but not limited to:
15
16 Alternative Disinfectants Guidance Manual (USEPA, 1999b)
17
18 Handbook of Chiorination and Alternative Disinfectants (White, 1999)
19
20 Ultraviolet Disinfection Guidance Manual for the Long Term 2 Enhanced Surface
21 Water Treatment Rule (USEPA, 2006b)
22
23 Water Quality and Treatment (AWWA, 1990b)
24
25 Membrane Filtration Guidance Manual (USEPA, 2005)
26
27 Simultaneous Compliance Guidance Manual (USEPA 2007a)
June 2008 Ground Water Rule 5-21 Public Review Draft
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1 6. References
2
3
4 Alberta Agriculture. Food and Rural Development. 1999. Shock Chlorination and Control of
5 Iron Bacteria. Adapted from Agdex FS716 (D12). Available at:
6 http://wwwl.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdexll42.
7
8 AWWA (American Water Works Association). 1987b. AWWA Standard for Factory-Coated
9 Bolted Steel Tanks for Water Storage. AWWA D103-87. Denver, Colo.: AWWA.
10
11 AWWA. 1990a. Recommended Practice for Backflow Prevention and Cross Connection
12 Control. AWWA Manual M14. Denver: AWWA.
13
14 AWWA. 1990b. Water Quality and Treatment. F.W. Pontius (editor). AWWA. New York:
15 McGraw-Hill.
16
17 AWWA. 1991. Guidance Manual for Compliance with the Filtration and Disinfection
18 Requirements for Public Water Systems Using Surface Water Sources. Available from:
19 AWWA, 6666 West Quincy Avenue, Denver, CO 80235.
20
21 AWWA. 1995a. AWWA Standard for Circular Prestressed Concrete Water Tanks with
22 Circumferential Tendons, AWWA D115-95. Denver,Colo: AWWA.
23
24 AWWA. 1995b. AWWA Standard for Wire- and Strand-Wound Circular Prestressed-Concrete
25 Water Tanks. AWWA D110-95. Denver, Colo: AWWA.
26
27 AWWA. 1995d. Water Transmission and Distribution. Second edition. Denver, CO
28
29 AWWA. 1996. A WWA Standard for Welded Steel Tanks for Water Storage. AWWA D100-96.
30 Denver, Colo.: AWWA.
31
32 AWWA. 1996a. A WWA Standard for Flexible-Membrane Lining and Floating-Cover Materials
33 for Potable-Water Storage. AWWAD130. Denver, Colo.:AWWA.
34
35 AWWA (American Water Works Association). 1998. AWWA ManualM42Steel Water-
36 Storage Tanks. Denver, Colo.: AWWA.
37
38 AWWA. 2003. AWWA Standard for Disinfection of Wells. C-654-03.
39
40 Backflow Prevention Theory and Practice. University of Florida, Division of Continuing
41 Education, Center for Training Research and Education for Environmental Occupations.
42 Ritland, Robin L. 1990Kendall/ Hunt Publishing Company, Dubuque, Iowa.
43
44 Bloetscher, F., A. Muniz, J. Largey. 2007. Siting, Drilling, and Construction of Water Supply
45 Wells. AWWA. Denver, CO.
46
47 Borch, M.A., S.A. Smith, and L.N. Noble. 1993. Evaluation and Restoration of Water Supply
48 Wells. Denver: AWWA/AwwaRF.
49
June 2008 Ground Water Rule 6-1 Pub lie Review Draft
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50 Florida Department of Environmental Protection (DEP). 1996. The State of Florida's Evaluation
51 of Cross-Connection Control Rules/Regulations in the 50 States. Tallahassee: Florida DEP.
52
53 Department of the Army. 1994. "Chapter 9: Alternative Well Construction." Multiservice
54 Procedures for Well-Drilling Operations. Field Manual 5-484. Available at
55 GlobalSecurity.org.: http://www.globalsecuritv.org/militarv/librarv/policv/army/fm/5-
56 484/Ch9.htm.
57
58 Gordon, G., L. Adam, and B. Bubnis. 1995. Minimizing Chlorate Ion Formation in Drinking
59 Water when Hypochlorite Ion is the Chlorinating Agent. Denver: AWWA/AwwaRF.
60
61 Grundfos Engineering Manual Water Systems Engineering Manual for Groundwater Supply and
62 Special Applications. Available at:
63 http://www.burdickandburdick.com/Grundfos%20Manuals/L-SP-TL-500.pdf
64
65 IBWA. 2005. Bottled Water Code of Practice. Available at:
66 http://www.bottledwater.org/public/pdf/IBWA05ModelCode Mar2.pdf
67
68 Jorgenson, D., M. Wireman and D. Olsen. Spring 1998. USEPA Update: Assessing the
69 Vulnerability of Public Water Supply Wells to Microbial Contamination. GWMR.
70
71 Kansas Geological Survey. 2004. "Ground Water: Recovery." Marshall County Geohydrology.
72 Available at: http://www.kgs.ku.edu/General/Geology/Marshall/05_gw3.html.
73
74 Kirmeyer, G.J., L. Kirby, B.M. Murphy, P.F. Noran, K.D. Martel, T.W. Lund, J.L. Anderson,
75 and R. Medhurst. 1999. Maintaining and Operating Finished Water Storage Facilities.
76 Denver,Colo.: AWWA and AWWARF.
77
78 Lagerquist, J.M., and R.S. Summers. 2004. Disinfection Byproduct Control with Chlorine
79 Dioxide and Other Alternative Oxidant Strategies. Presented at the 2005 AWWA WQTC
80 conference.
81
82 Linsley, R.K., J.B. Franzini, D.L. Freyburg, and G. Tchobanoglous. 1992. Water-Resources
83 Engineering. Fourth Edition. Boston: Irwin McGraw-Hill.
84
85 National Academy Press. 1997. Safe Water from Every Tap. National Academy of Sciences.
86 Washington, DC. Available at: http://www.epa.gov/safewater/mdbp/word/alter/app_b.doc.
87
88 National Environmental Training Association. 1998. Learner's Guide: How to Conduct a
89 Sanitary Survey of Small Water Systems. Phoenix: NETA.
90
91 National Groundwater Association. 2007. Water Well Basics: Types of Wells. Available at:
92 http://www.wellowner.org/awaterwellbasics/typesofwells.html.
93
94 National Research Council (NRC). 1997. Safe Water from Every Tap, Improving Water Service
95 to Small Communities. Washington, DC: National Academy Press.
96
97 Purdue Research Foundation (Purdue). 2001. Well Drilling Methods. Available at:
98 http://abe.www.ecn.purdue.edu/~epados/farmstead/private/src/drill.htmtfbored.
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99
100 Purdue University. 1997. Well Water Location and Condition Tutorial. Information gathered
101 from the Farmstead Assessment Program, a cooperative project of the University of
102 Wisconsin-Extension, Minnesota Extension Service, and the United States Environmental
103 Protection Agency Region V. Available at:
104 http://abe.www.ecn.purdue.edu/~epados/farmstead/well/src/title.htm.
105
106 Recommended Standards for Water Works. 2007. Great Lakes-Upper Mississippi River Board of
107 State and Provincial Public Health and Environmental Managers.
108 http://10statestandards.com/waterstandards.html
109
110 Salvato, J. 1998. Environmental Engineering and Sanitation. Fourth Edition. John Wiley and
111 Sons, Inc.
112
113 Ten States Standards. 2003. Recommended Standards for Water Works (Ten States Standards).
114 Great Lakes Upper Mississippi River Board of State Public Health and Environmental
115 Managers. Available from: Health Education Services, PO Box 7126, Albany, NY 12224.
116 Available at: www.hes.org.
117
118 Ten States Standards. 2007. Recommended Standards for Water Works (Ten States Standards).
119 Great Lakes Upper Mississippi River Board of State Public Health and Environmental
120 Managers. Available from: Health Education Services, PO Box 7126, Albany, NY 12224.
121 Available at: www.hes.org.
122
123 Tikkanen, M., J.H. Schroeter, L.Y.C. Leong, and R. Ganesh. 2001. Guidance Manual for
124 Disposal of Chlorinated Water. Denver: AWWA/AwwaRF.
125
126 UFTREEO Center (University of Florida Training, Research and Education for Environmental
127 Occupations Center). 1998. Learner's Guide: How to Conduct a Sanitary Survey of Small
128 Water Systems, (developed under EPA Training Grant T902854). Available from: National
129 Environmental Training Association, 2930 East Camelback Road, Suite 185, Phoenix, AZ
130 85016-4412, Phone: 602-956-6099.
131
132 USEPA. 1973. Manual of Individual Water Supply Systems. USEPA-43 0-9-73-003.
133 Washington, DC.
134
135 USEPA. 1982. Manual of Individual Water Supply Systems. USEPA 570-9-82-004.
136 Washington, DC.
137
138 USEPA. 1989. Cross Connection Control Manual. USEPA 570-9-89-007. Washington, DC.
139
140 USEPA. 1992. Seminar Publication: Control of Biofilm Growth in Drinking Water Distribution
141 Systems. USEPA 625-R-92-001. Washington, DC.
142
143 USEPA. 1998. Technologies and Costs for Control of Disinfection Byproducts. Prepared by
144 Malcolm Pirnie, Inc for USEPA, Office of Ground Water and Drinking Water, PB93-
145 162998. Washington, DC.
146
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147 USEPA, 1999a. Guidance Manual for Compliance with the Interim Enhanced Surface Water
148 Treatment Rule: Turbidity Provisions. EPA 815-R-99-010 . USEPA. Washington DC.
149
150 USEPA. 1999b. Alternative Disinfectants and Oxidants Guidance Manual. EPA 815-R-99-
151 014.USEPA. Washington DC.
152
153 USEPA. 2000. Drinking Water Glossary; A Dictionary of Technical and Legal Terms Related to
154 Drinking Water. Office of Ground Water and Drinking Water. May 30. USEPA.
155 Washington. DC. Available at: http://www.epa.gov/OGWDW/Pubs/gloss2.html.
156
157 USEPA. 2001. A Small System Guide to the Total Coliform Rule, Publication Number EPA
158 816-RO1-017A. http://vosemite.epa.gov/water/owrccatalog.nsf/.s
159
160 USEPA. 2002. Sources of Technical and Financial Assistance for Small Drinking Water Systems
161 Publication number EPA 816-K-02-005
162
163 USEPA. 2003. Cross-Connection Control Manual. USEPA. EPA 816-R-03-002. Washington,
164 DC. Available at: http://www.epa.gov/safewater/crossconnection.html.
165
166 USEPA 2003a. Drinking Water Inspector's Field Reference: For Use When Conducting a
167 Sanitary Survey of a Small Ground Water System. EPA 816-R-03-023. Washington, DC.
168
169 USEPA 2003b. How to Conduct a Sanitary Survey of Small Water Systems: A Learner's Guide.
170 EPA 816-R-03-012. Washington, DC.
171
172 USEPA 2003c. Asset Management: A Handbook for Small Water Systems. EPA 816-R-03-016.
173 Washington, DC.
174
175 USEPA. 2003d. Strategic Planning; A Handbook for Small Water Systems, Publication Number
176 EPA816-R-03-015
177
178 USEPA. 2004. Guidance Manual for Compliance with the Long Term 1 Enhanced Surface
179 Water Treatment Rule - Turbidity Provisions. USEPA. EPA 816-F-02-001. Washington,
180 DC.
181
182 USEPA. 2004a. The Standardized Monitoring Framework: A Quick Reference Guide
183 Publication Number EPA 816-F-04-010. www.epa.gov/safewwater/regs.html
184
185 USEPA. 2004b. Lead and Copper Rule: A Quick Reference Guide, Publication Number EPA
186 816-F-04-009. www.epa.gov/safewwater/regs.html
187
188 USEPA. 2005. Membrane Filtration Guidance Manual. Office of Water. USEPA. EPA 815-R-
189 06-009. Washington, DC.
190
191 USEPA. 2005a. What to Do After the Flood. Office of Water. USEPA. EPA 816-F-05-021.
192 Washington, DC.
193
194 USEPA. 2006a. Basic Well Information. USEPA. Washington, DC. Available at:
195 http://www.epa.gov/safewater/privatewells/basicinformation.html.
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196
197 USEPA 2006b. Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced
198 Surface Water Treatment Rule. Office of Water. USEPA. EPA 815-R-06-007. Washington
199 DC.
200
201 USEPA. 2006c. Technology and Cost Document for the Final Ground Water Rule. EPA 815-R-
202 06-015.
203
204 USEPA. 2006d. Distribution System Indicators of Drinking Water Quality. Office of Water.
205 USEPA. December 2006.
206
207 USEPA. 2006e. EPA's Interactive Sampling Guide for Drinking Water System Operators
208 Publication Number EPA 816-C-06-001. http://yosemite.epa.gov/water/owrccatalog.nsf/
209
210 USEPA. 2007a. Simultaneous Compliance Guidance Manual for the Long Term 2 and Stage 2
211 DBF Rules. Office of Water. EPA 815-R-07-017.
212
213 USEPA. 2007b. Consecutive Systems Guidance Manual for the Ground Water Rule. Office of
214 Water. EPA 815-R-07-020.
215 http://www.epa.gov/safewater/disinfection/gwr/pdfs/guide gwr consecutive-guidance.pdf
216
217 USEPA. 2007c. Source Water Monitoring Guidance Manual. Office of Water. EPA 815-R-07-
218 019.
219 http://www.epa.gov/safewater/disinfection/gwr/pdfs/guide gwr sourcewatermonitoring.pdf.
220
221 Viessman Jr., W., and MJ. Hammer. 1998. Water Supply and Pollution Control. Sixth Edition.
222 Menlo Park: Addison-Wesley.
223
224 White, G.C. 1999. Handbook of Chlorination and Alternative Disinfectants. New York: Van
225 Nostrand Reinhold.
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Appendix A
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1
2
Appendix A. Applications of Various Backflow Prevention Assemblies or Methods
Description
Advantages/Disadvantages
Protects
Against
Backpressure
Protects
Against
Backsiphonage
Hazard
Type
High
Hazard1
Containment/
Isolation
Air Gap
- A physical separation between the free
flowing outlet of a potable water pipe and
an unpressurized receptacle
(USCFCCCHR, 1993).
- Physical separation should be at least
twice the diameter (2D) of the outlet pipe
and no less than one inch (USEPA,
2003).
- The only means of absolute separation
between plumbing systems, and should
be used whenever possible and not
bypassed (USPHS, 1966).
-Well-designed and properly maintained
air gaps are AWWA's recommended
method of protection against backflow for
extremely hazardous installations
(AWWA, 1990a).
- Mainly used at the end of a service line
(USEPA, 2003), an air gap is the
recommended protection for sewage
pumps and ejectors, sewer pipe
connections, trap primers, and swimming
pools.
Advantages
-Non-mechanical
-Highly effective and easy to integrate into
a current system
-Provides maximum protection
Disadvantages
- Pressure loss can lead to the need for
secondary pumping requirements in
continuous piping systems (USEPA,
1989).
- Frequent inspection is needed to
maintain 2D physical separation and
prevent backsplash (USEPA, 2003).
- Water exposure to the surrounding
atmosphere can lead to contamination by
airborne contaminants and can allow
disinfectant residuals to escape (USEPA,
1989).
Yes
Yes
Health
Yes
Isolation
Barometric Loop
- Continuous section of pipe installed in
existing piping that usually extends 35
feet vertically from the highest fixture and
returns to its original height.
Advantaqes
Non-mechanical
Disadvantages
- Limited by the need for a 35 foot vertical
space. Installing a pipe loop at this height
is usually expensive and difficult and as a
result not commonly used (USPHS, 1966).
No
Yes
Non-health
No
Isolation
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Description
Advantages/Disadvantages
Protects
Against
Backpressure
Protects
Against
Backsiphonage
Hazard
Type
High
Hazard1
Containment/
Isolation
Pressure Type Vacuum Breaker
- Under normal flow conditions, the inlet
water pressure opens the check valve
allowing flow to continue, while pushing
the PVB's air inlet valve against the air
inlet canopy preventing air from entering.
However, when normal flow is interrupted
due to at least a partial vacuum, the
check valve closes preventing backflow.
If the check valve is fouled and does not
close, the air inlet valve acts as a second
check and opens, allowing air to enter the
system (AWWA, 1990a).
- Must be installed only in a vertical
position, above grade with a minimum of
12 inches of vertical clearance above the
highest point in the downstream piping,
and must be accessible for testing and
repair (BMI, 1996).
- PVBs are available for piping ranging
from one-half to 10 inches in diameter
and are widely used in agricultural and
industrial applications (USEPA, 1989).
Advantages
- Can be used under constant pressure
and can be tested in line (USEPA, 2003).
-Available in sizes ranging from one-half
to ten inches (USEPA, 2003)
Disadvantages
- Some manufacturers may have pressure
or temperature limitations placed on their
assemblies (BMI, 1996).
No
Yes
Health/Non-
Health
No
Either
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Description
Advantages/Disadvantages
Protects
Against
Backpressure
Protects
Against
Backsiphonage
Hazard
Type
High
Hazard1
Containment/
Isolation
Double check valve
- Consists of two check valves in one
body located between two tightly closing
gate valves. The check valves are
spring-loaded and require approximately
one pound of pressure to open (USEPA,
2003).
- Under normal flow conditions in excess
of one pound of pressure, the water
pressure will hold the check valves open
allowing water to flow through the
assembly. When backflow conditions
occur, the check valves close and prevent
backflow.
Modified DCVs
- Double check detector check (DCDC), is
commonly used forfireline installations.
DCDC differs from the DCV in that it has
a metered bypass line for low flow
situations (USEPA, 1989).
- Residential dual check (RDC) that
differs from the DCV in that it has no test
cocks or gate valves. RDCs were
designed to provide inexpensive
protection against backpressure and
backsiphonage from household hazards
(USEPA, 1989). They are available in
sizes ranging from one-half to one inch
(USEPA, 1989).
Advantages
- Can be installed in pits or vaults, and, in
some cases can be installed vertically
(BMI, 1996).
-The internal loading or weighting allows
the check valve to seal even in the
presence of small debris (USEPA, 2003).
-Ability to be used under constant
pressure(USEPA, 2003)
Disadvantages
-should only be used for low to medium
hazard situations
Yes
Yes
Non-health
No
Either
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Description
Advantages/Disadvantages
Protects
Against
Backpressure
Protects
Against
Backsiphonage
Hazard
Type
High
Hazard1
Containment/
Isolation
Reduced pressure principle backflow prevention device
- Consist of two independent check
valves - one is a differential relief valve
between the two check valves and the
other is located below the first check
valve (AWWA, 1990a). Both valves are
equipped with gate valves and test cocks.
- Under normal flow conditions, water
pressure forces both check valves open.
When the water passes through the first
check valve a slight predetermined
pressure drop results (USEPA, 1989).
The space between the first and second
check valves is normally maintained at
two psi lower than the inlet pressure. The
second check valve is lightly loaded to
allow the water pressure to hold it open
and results in a pressure drop of one psi.
When reduced pressure from the inlet, or
increased pressure downstream occurs,
the check valves close and the pressure
differential between the inlet and the
space between the two check valves
forces the flow out of the differential relief
valve (USEPA, 1989).
- RPBAs are available for service lines
ranging from three-fourths to 10 inches
and can be installed in pits or vaults.
Advantages
- Provides maximum protection (USEPA,
2003).
- Discharge of flow out of the differential
relief valve also acts as an indication of a
backflow
event.
-The differential relief valve also provides
backflow protection in the event that the
second check valve becomes fouled.
Disadvantages
- Some models can only be installed
horizontally and have temperature and
pressure limitations (BMI, 1996).
- More expensive than the other backflow
preventers.
Yes
Yes
Health
Yes
Either
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Description
Advantages/Disadvantages
Protects
Against
Backpressure
Protects
Against
Backsiphonage
Hazard
Type
High
Hazard1
Containment/
Isolation
Double check valve with intermediate atmospheric vent
- Similar in construction and function to a
DCV in that it has double check valves
within a single body. However, it also has
an atmospheric vent located between the
two check valves, which adds extra
protection (USEPA, 2003).
Advantages
- Compact with protection for moderate
hazards
-Can be used under constant pressure
-Available in sizes ranging from one-half to
three-fourths of an inch (USEPA.2003).
Yes
Yes
Non-health
No
Either
2 1A high hazard is when a cross connection endangers human health. Low hazards may result in contamination but generally not affect human health
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