EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

January 2003

APPENDIX B

RECEIVING WATERS
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Appendix B: Receiving Waters

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TABLE OF CONTENTS

1.0 GOALS AND PURPOSE OF THE APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

2.0 REGULATORY AND TECHNICAL BACKGROUND FOR DESIGNING A WATER

QUALITY ASSESSMENT PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2

2.1 Mining Impacts on Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2

2.1.1 Disturbance Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3

2.1.2 Processing Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3

2.1.3 Waste Disposal Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4

2.1.4 Support Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-6

2.2 Water Quality Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-6

2.3 Processes that Affect Contaminant Dispersal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-8

2.3.1 Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-8

2.3.2 Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-8

2.3.3 Surface Water Hydrology and Hydrogeology . . . . . . . . . . . . . . . . . . . . . . . B-9

2.3.4 Aqueous Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-9

2.4 Using the Watershed-Based Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-11

2.4.1 Determining Pre-Mining Background Water Quality . . . . . . . . . . . . . . . . B-11

2.4.1.1 Natural Background in Mineralized Areas . . . . . . . . . . . . . . . . . B-12

2.4.1.2 Effects of Historic Mining and Other Anthropogenic 

Disturbances

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-13

3.0 DESIGNING A WATER QUALITY MONITORING PROGRAM . . . . . . . . . . . . . . . . B-14

3.1 Sampling Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-15

3.1.1 Mixing Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-16

3.2 Sampling Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-16

3.2.1 Sampling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-17

3.2.2 Selecting Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-17

3.3 Sampling Schedule and Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-18

3.4 Assessing the Health and Diversity of Biota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-19

4.0 DATA ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-19

4.1 Contributions of Tributaries and Ground Water to Surface Flow . . . . . . . . . . . . . . B-19

4.2 Translators for Dissolved to Total Recoverable Constituent Concentrations . . . . . B-20

4.3 Computing Metal Loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-20

4.4 Other Characterization and Data Analysis Issues . . . . . . . . . . . . . . . . . . . . . . . . . . B-20

4.4.1 Below Detection Limit Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-21

4.4.2 Using Existing and Historical Data Sets . . . . . . . . . . . . . . . . . . . . . . . . . . B-22

4.5 Geochemical Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-22

4.6 Fate and Transport Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-23

4.7 Other Analysis Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-24
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TABLE OF CONTENTS 

(continued)

5.0 GUIDANCE FOR PREPARATION OF A QUALITY ASSURANCE PROJECT PLAN

(QAPP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-25

5.1 Overview of the Process for Developing a Monitoring Plan . . . . . . . . . . . . . . . . . B-25

5.2 Components of a QAPP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-26

5.2.1 Project Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-28

5.2.2 Measurement and Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-30

5.2.3 Assessment and Oversight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-32

5.2.4 Data Validation and Usability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-33

6.0 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-34

LIST OF TABLES

B-1. Example Reagents Used at Metal Mines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-5

B-2. Water Quality Parameters Typically Measured at Proposed Metal Mining Sites . . . . . B-18

LIST OF FIGURES

B-1. Conceptual physicochemical model of metal transport in a river from Schnoor . . . . . . B-10

B-2. Example flow-chart for developing a monitoring project . . . . . . . . . . . . . . . . . . . . . . . B-27
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1.0 GOALS AND PURPOSE OF THE APPENDIX

The primary goal of this appendix is to outline the rationale and methods to characterize

water quality in and around a proposed mine site. It is intended to be used in conjunction with

other appendices in this source book to which the reader is referred for more detailed

information. Relevant appendices include Appendix A, Hydrology, Appendix E, Wastewater

Management, Appendix F, Solid Waste Management, and Appendix H, Erosion and

Sedimentation. Background materials in this appendix review how mining activities can impact

water quality, describe how water quality standards are developed, outline general processes

related to contaminant dispersal, and summarize important aspects of a watershed-based

evaluation. The background materials are followed by a section that describes practical aspects

of developing a program to monitor water quality. A section on data analysis provides general

information for modeling water quality data. The appendix concludes by reviewing the

important aspects of monitoring and quality assurance as needed for NEPA (EIS) and NPDES

purposes. 

Surface and ground waters that receive treated and untreated discharges from mine sites are

referred to as “receiving waters”. Point source discharges to receiving waters are regulated

under Section 402 of the Clean Water Act, which requires the preparation of National Pollutant

Discharge Elimination System (NPDES) permits. A key aspect of the NPDES permitting

process is protecting the quality and designated uses of receiving waters. To predict the

potential impacts of mining operations on receiving water quality, it is important to have

adequate discharge and baseline receiving water data. Because data needs are varied and many,

it is important to assess the scope of specific water quality data needs and their uses prior to

beginning data collection to ensure that data will serve all intended purposes and that they will

be collected in an efficient manner. Receiving water quality data at mines may be used for a

variety of other purposes including: 

• Establishing baseline conditions to support calculations of NPDES permit limits,

• Providing justifications for site-specific criteria,

• Developing dissolved to total recoverable translators,

• Developing the basis for effluent trading,

• Documenting the quality of the affected environment for NEPA analysis,

• Determining cumulative impacts under NEPA,

• Predicting environmental consequences of the proposed action and alternatives under

NEPA,

• Assisting in conducting watershed analyses, 

• Supporting remedial activity in impaired watersheds, and 

• Monitoring long-term trends. 

This guidance is focused on characterizing water quality at proposed mines. Although the

term “receiving water” is used throughout, the methods and techniques described can be applied

to any surface or ground water and are not restricted to waters that will receive direct discharges

of mine effluent. As part of this analysis applicants may be required to understand the

interactions between surface and ground waters and characterize other physical and biological
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aspects of the aquatic environment. The concepts and guidance presented herein also are

appropriate for surface water and ground water quality monitoring at other stages of a mine’s life

cycle, including operation, closure, and post-closure. In these settings, water quality data can be

used for compliance monitoring, trend monitoring, monitoring the effectiveness of Best

Management Practices (BMPs), and establishing and verifying any permitted mixing zones. 

In 1997, EPA released the “Hardrock Mining Framework”, a document that outlined the

Agency’s approach to dealing with environmental concerns at hardrock mining sites. This

document acknowledged that recent national initiatives were directed toward ensuring that point

sources of pollution were addressed on a watershed basis. In addition, the Framework

recognized that the watershed approach could be an administrative means to reduce pollutant

loadings on a cost-effective basis. Consequently, this appendix stresses the use of the watershed

approach to determine receiving water quality. 

2.0 REGULATORY AND TECHNICAL BACKGROUND FOR DESIGNING A WATER

QUALITY ASSESSMENT PROGRAM

This section briefly discusses technical and regulatory factors that are important to consider

when designing a program to assess water quality. It begins by describing the types of water

quality impacts that can occur as a result of mining activities, then briefly summarizes the

regulatory development of water quality standards, describes processes that affect contaminant

dispersal, and discusses the watershed approach to water quality assessment. Applicants

proposing new or expanded mining projects should be certain to fully characterize the existing

quality of surface and ground water resources at their site, so that an EA or EIS will be able to

fully describe the types of impacts that the mine may create. 

2.1 Mining Impacts on Water Quality

For the purposes of considering impacts to water quality, the diverse activities associated

with hardrock mining can be divided into four main areas. Disturbance activities include the

development of mine pits, shafts, and adits and surface disruptions associated with mine

development and facility construction (e.g., grading, road construction, impoundment

construction, foundation preparation, soil stripping, and pipeline and powerline construction). 

Processing activities include the construction and operation of crushing and milling facilities;

flotation concentrators; smelters and refineries; heap and dump leach facilities; vat and tank

leach plants; water treatment facilities; and carbon stripping, zinc precipitation, and solvent

extraction/electrowinning plants. Waste disposal activities include the construction and

operation of waste rock dumps, overburden piles, tailings impoundments, and slag piles and

other process waste. Support activities include those actions required for day-to-day operation

of the mine such as equipment maintenance, fuel storage, wastewater treatment, and laboratory

analysis. EPA has prepared a series of Technical Resource Documents that summarize the

extraction and beneficiation of lead-zinc, gold, copper, iron, uranium, gold placer, and phosphate

and molybdenite ores. They can be obtained from the EPA Office of Solid Waste webpage

(http://www.epa.gov/epaoswer/other/mining.htm).
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2.1.1 Disturbance Activities

Disturbance activities increase the potential for surface or ground water impact by exposing

mineralized rock, disturbing native soils and vegetation, altering slope angles, and modifying

watershed and aquifer characteristics. Mine pits, adits, shafts, and open cuts that expose

mineralized rock have the potential to produce increased loadings of metals, dissolved solids,

suspended solids, and acidity to surface waters. The construction of roads, utility lines, and

facility foundations and stripping activities associated with the development of mine pits and the

construction of mine processing, disposal, and water management facilities increase the potential

for sediment contamination. These activities alter natural watershed characteristics by

increasing runoff, decreasing soil cohesion and infiltration, and increasing susceptibility to

erosion. Potential mining impacts associated with erosion and sedimentation are described in

more detail in Appendix H, Erosion and Sedimentation. 

The types of constituents that can be released during or following disturbance activities

depend on the nature of the mineralization and the mining operation. Mining disturbances may

increase the concentrations of suspended particles and metals (e.g., Al, As, Cd, Cr, Cu, Fe, Pb,

Mn, Hg, Ni, Se, Ag, Zn), major cations (e.g., ammonia nitrogen, Ca, Mg, K, Na), and anions

(e.g., nitrate, sulfate, chloride, carbonate) that form a large portion of the total dissolved solids in

surface waters. Constituent concentrations can be increased through dissolution or retransport of

naturally occurring compounds or by the dissolution of reagents, such as blasting residues (Table

B-1), that are used during disturbance activities. Importantly, surface and underground

disturbances can result in the production of acid drainage. This phenomenon, referred to as acid

mine drainage or acid rock drainage, results when iron sulfide minerals (pyrite and marcasite),

which commonly occur in mineralized zones, are exposed to the oxidizing environment of the

atmosphere. The acidity produced from exposed pit walls and underground workings can impact

surface water quality for many years after mining ceases by lowering pH and increasing the

amount of metals leached from exposed surfaces and maintained in solution. 

Disturbance activities release contaminants to surface and ground waters primarily through

precipitation runoff, releases of mine water, or disruption of aquifers and their confining layers. 

2.1.2 Processing Activities

Processing activities increase the potential for surface water impact by creating facilities in

which metals are concentrated to values significantly above those in the ore, dissolving metals

into solution, grinding metal-rich ore into fine particle sizes, and storing and using large

quantities of reagents that can potentially degrade surface water quality. Depending on the type

of milling and concentrating process employed, a mine may construct ore stockpiles to assure

consistent feed to a mill. Pad and dump leaching facilities have associated impoundments to

store barren and pregnant leach solutions, pipelines to transfer solutions between storage ponds

and leach pads, and leachate and seepage collection facilities. 
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Contamination from processing facilities can occur in many forms that depend on the type

of ore being processed, the type of on-site processing, and the specific mine design. 

Consequently, the list of chemicals used at a mine site can be extensive and may include

flotation reagents, frothing and collection agents, scale inhibitors, flocculents, thickeners, leach

solutions, and leachate neutralizing solutions. Table B-1 gives examples of the types of

processing reagents that may be used by mining operations; it should be recognized that this

table does not provide a comprehensive listing.

Processing activities can release contaminants to surface waters in a variety of ways that

include spills of reagent materials or processing fluids (e.g., pipeline ruptures), leaks at

processing facilities (e.g., liner tears), storage pond overflows (e.g., during storm events), and

facility failures (e.g., slope failure of a leach dump). Contaminant pathways can be direct

(release directly to surface waters) or indirect. Examples of indirect contaminant pathways

include infiltration to ground water that exchanges with surface water, seepage to soil or bedrock

which discharges to surface water, and seepage through or below impoundment dams and berms.

2.1.3 Waste Disposal Activities 

Waste disposal activities increase the potential for surface water impact by creating

permanent features in which waste materials are stored. Waste materials can serve as sources of

leachable metals, acidity, cyanide or other toxic constituents, and fine-grained sediment for

many years after mining ceases. Examples of these facilities include waste rock dumps,

impoundments, and spent ore piles. Descriptions of the types of waste disposal facilities used at

mines sites are given in Appendix F, Solid Waste Management. 

Waste disposal facilities can impact receiving waters through the release of sediment,

metals, and other contaminants. In part, the types of contaminants available to the environment

depend on the character of the waste materials (e.g., grain size and mineralogy), the means by

which these materials were processed (e.g., cyanide or acid leach), and the types of closure

procedures that were employed (e.g., rinsing, neutralization, capping and revegetation). Finegrained materials such as tailings piles are a significant source of erodible sediment that

potentially can be mobilized and redeposited in stream beds by surface runoff. Over the long

term, waste rock dumps, tailings impoundments, and spent ore piles that contain sulfide-bearing

material can contribute acidity to receiving waters through the oxidation of pyrite and marcasite

as described in Appendix F, Solid Waste Management. Acid leachates produced from these

materials facilitate the dissolution of the metals listed in Section 2.1.1, Disturbance Activities.

Closed cyanide and acid heap leach units may contain residual cyanide and cyanide by-products,

or acidity that can be released to receiving waters if the heaps are not properly rinsed and

neutralized (Simovic et al., 1985).

Contaminants can be released to surface waters in a variety of ways that include physical

failure (e.g., breach or sloughing of a tailings impoundments), seepage (e.g., below an

impoundment dam), saturation and overflow of lined facilities (i.e., the “bathtub” effect), and

erosion by wind and water (e.g., gully formation during storm events). Contaminant pathways

can be direct (release directly to surface waters) or indirect. Examples of indirect contaminant 
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Table B-1. Example Reagents Used at Metal Mines

Disruption Activities

Blasting Agent Ammonium nitrate & fuel oil (ANFO)

Processing Reagents

Flotation Reagents Alkaline sulfides

Sodium cyanide

Sodium ferrocyanide

Aliphatic alcohol

Phenol

Ethyl and amyl xanthates

Alkyl dithiophosphate

Methyl isobutyl carbinol

Aerofloats

Copper sulfate

Zinc sulfate

Sodium sulfide

Kerosene

Phosphorous pentasulfide

Sulfuric acid

Sodium hydroxide

Pine oil

Polyglycol ether

Sodium isopropyl xanthate

Sodium diethyl phosphorodithioate

Thiocarbamate

Pine oil

Dichromate

Zinc hydrosulfate

Sodium bisulfate

Solvent Extraction - Electrowinning Reagents Sulfuric acid

Oxime compounds

Amphoteric fluoroalkylamide

derivative

Hydrocarbon distillates

Cobalt sulfate solution

Diethylene glycol butyl ether

Miscellaneous Concentrator Reagents Anionic polyacrylamide

Polyacrylate

Polyphosphate

Polymeric and organophosphorous

compounds

Leaching Reagents Sulfuric acid Sodium cyanide

Leach Processing Reagents Sodium hydroxide

Hydrochloric acid

Nitric acid

Lead nitrate

Zinc

Sodium sulfide

Leach Neutralizing Reagents Hydrogen peroxide

Chlorine

Sodium hypochlorite

Lime

Sulfur dioxide

Copper

Support Activities

Petroleum Products Gasoline

Diesel fuel

Gear oil, motor oil, hydraulic oil

Lubricating grease and oil

Antifreeze

Paraffinic, napthenic, and aromatic

hydrocarbons (solvent)

Propane

Wastewater Treatment Reagents Ion Exchange Regenerants:

Hydrochloric acid 

Sulfuric acid

Sodium chloride

Descalants:

Calcium sulfate

Calcium carbonate

Silicon dioxide

Sodium hexametaphosphate

Chemical Precipitation Reagents:

Lime

Alum

Sodium hydroxide

Calcium hydroxide

Hydrogen sulfide

Calcium sulfide

Sources: Coeur Alaska, Inc., 1997; U.S. EPA, 1994a, 1994b, 1994c, 1998a; Knorre and Griffiths, 1985; Montgomery Watson,

1996; Scott, 1985; Viessman and Hammer, 1993.
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pathways include infiltration to ground water that exchanges with surface water, seepage to soil

or bedrock which discharges to surface water, and seepage through or below impoundment dams

and berms.

2.1.4 Support Activities

Support activities can increase the potential for receiving water impacts through facilities

that use and store chemicals and generate waste materials. Support activities can release

contaminants to surface waters through a variety of means that include spills and leaks from fuel

handling and storage facilities, seepage from solid waste landfills, and seepage and runoff from

equipment maintenance facilities. Contaminant pathways may be direct or indirect. Examples

of indirect contaminant pathways include seepage to soil or bedrock from above-ground fuel

storage tanks and runoff from soils contaminated with solvents or degreasing agents.

2.2 Water Quality Standards

An important aspect of mine review for EPA is evaluating whether a project will adversely

affect water quality. One measure of this analysis is the potential to cause exceedances of water

quality standards. This type of analysis involves characterizing potential discharges to streams

and determining the impacts they would cause to water quality. Prior to evaluating the potential

for water quality impacts, the water quality standards that apply to the receiving water must be

determined. Water quality standards are provisions of State or Federal law which consist of

three components: (1) designated beneficial uses for all Waters of the U.S., (2) water quality

criteria (which may be numeric or narrative) for the waters based upon their uses, and (3)

antidegradation policies. State water quality standards and implementing provisions are

approved by EPA and are codified in State regulations. It is essential for a mine to obtain the

most up-to-date state water quality standards and regulations since they often change on a

periodic basis. Many of these regulations are now available on-line. More information

regarding water quality standards is provided in EPA’s Water Quality Standards Handbook (U.S.

EPA, 1994d).

Under the Clean Water Act, each State must classify all of the waters within its boundaries

by their intended use [see §303(c)(2)]. Once designated beneficial uses have been determined,

the State must establish numeric and narrative water quality standards to ensure the attainment

and/or maintenance of the use. Designated beneficial use classifications include the use and

value of water for public water supplies; protection and propagation of fish, shellfish, and

wildlife; recreation in and on the water body; and agricultural, industrial and navigational

purposes (see 40 CFR §131.10 for more detail on the designation of uses). For a specific water

body, a mine can determine the applicable standards based on the designated use classifications. 

Where multiple use classifications apply to a water body (e.g., recreational and aquatic life uses),

the most sensitive use designations generally apply. Water bodies, especially minor tributaries,

may not be identified in State regulations along with their designated beneficial uses. In these

cases, States may assign to tributaries the same designated uses as the larger water body that they

flow into. Alternatively, they may have a general set of classifications that apply to all

unspecified water bodies.
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EPA recently published an updated listing of nationally recommended water quality criteria

for 157 pollutants (U.S. EPA, 1998b). States may either adopt these criteria or develop

alternative criteria that protect the designated uses of their waters. In such cases, the Clean

Water Act requires States to use sound scientific rationale to develop their water quality criteria. 

Criteria may be expressed as constituent concentrations, levels, or narrative statements that

represent a quality of water that supports a designated use. Criteria may be developed for acute

and chronic toxicity to aquatic organisms, agricultural and industrial uses, and human health

effect protection. Criteria, which are developed for both fresh waters and saline waters, may be

designated in the form of dissolved, total recoverable, and/or total constituent concentrations. 

Acute criteria are based on one-hour average concentrations that cannot be exceeded more than

once every three years on average, whereas chronic criteria are based on four-day average

concentrations that cannot be exceeded more than once every three years on average. While

some States use the same water quality standard values for all streams assigned an individual

designated use, others depend on stream-specific conditions. For example, some metals are

more toxic under low hardness conditions and the applicable standards depend on the hardness

of the receiving water. Other standards (e.g., turbidity and temperature) may be based on

deviation from natural conditions. For carcinogenic constituents, applicants should check with

State authorities to determine the human health risk factors that apply. The need for

representative baseline data for water quality parameters, especially as they relate to changes in

flow, is obvious and should be considered in developing baseline and operational monitoring

programs. 

Many states have specific procedures to establish “mixing zones,” which allow for the

natural dilution of discharges by stream flow, taking into consideration background levels of

individual pollutants and contributions from other dischargers. A mixing zone is a limited area

or volume of water where initial dilution of a discharge takes place and where numeric water

quality criteria can be exceeded but acutely toxic conditions are prevented (U.S. EPA, 1994d). 

Mixing zones typically are granted based on low-flow conditions (e.g., the 7Q10 flow in a

stream). Since mines often discharge to streams where 7Q10 conditions approach zero, many do

not qualify for mixing zones and water quality standards must be met at points of discharge. 

Operators wishing to use mixing zones must submit an application following procedures outlined

in the State water quality standards. Such applications require applicants to work closely with

the permitting authority.

States have a wide range of antidegradation requirements that prohibit discharges from

degrading existing water quality except under specific conditions. These policies are designed to

protect existing instream uses and water quality and to maintain and protect waters of

exceptional quality that represent an outstanding National resource. In cases where water quality

would be diminished, States are required to assure that water quality would remain adequate to

fully protect existing designated uses.

Most State water quality regulations include provisions for developing site- or streamspecific standards and reclassifying (i.e., changing the designated uses of) water bodies. 

However, there is almost always a significant burden on the applicant to demonstrate the need
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for such changes. Operators are encouraged to work closely with States and EPA in determining

whether site-specific standards/reclassifications are possible for a site and the supporting

information that would be required. EPA must approve all changes to State water quality

standards, including site-specific standards and reclassifications. 

2.3 Processes that Affect Contaminant Dispersal

The processes that affect contaminant dispersal depend in part on site-specific factors such

as climate, geology, surface and ground water hydrology, and water chemistry. These factors

control runoff, infiltration, weathering and erosion, and the dissolution and attenuation of metals. 

One goal of watershed-based analysis is to identify the processes that have a primary controlling

influence on water quality throughout the watershed. 

2.3.1 Climate

Climatic factors determine seasonal flow in a watershed and affect seasonal infiltration and

ground water recharge (see Section 3.3). Changes in infiltration and runoff can impact water

quality by affecting the extent to which metals are diluted during downstream flow, the degree to

which sediment and metal-bearing particles are eroded and transported downstream, and the

impact that may be caused as oxidation products are periodically flushed from waste rock dumps

and tailings piles. These effects need to be quantified so that natural and mining-induced

contributions to water quality can be distinguished. 

2.3.2 Geology

Surficial geology in mineralized areas should be expected to vary at the watershed scale. 

Variations can be manifested as changes in rock type, depth and character of soils, degree and

character of alteration, nature of mineralization, and extent of fracturing. Surface waters flowing

over and through different rock and soil types may have different constituent concentrations,

particularly with regard to major ions, pH, and alkalinity (e.g., Stumm and Morgan, 1996). For

example, where limestone or dolomite are present in a watershed, surface waters may contain

significant bicarbonate alkalinity and high concentrations of dissolved Ca and Mg. However, in

a different portion of the same watershed that is underlain by granite, waters may have much

lower bicarbonate, Ca, and Mg concentrations. 

In most mine areas, both the intensity of mineralization and the types of metallic minerals

present are likely to change with location in a watershed. Variations in the style of rock

alteration (e.g., phyllic vs. propylitic) can cause portions of a watershed to produce surface and

ground waters with different water quality characteristics (Smith et al., 1994; Mast et al., 1998). 

Mountainous terrains may expose the transition from primary hydrothermal sulfide minerals to

secondary oxide and carbonate minerals. The different solubilities and acid generating

capabilities of sulfide and oxide minerals may produce waters with significantly different pH and

metals and sulfate concentrations (e.g., Stumm and Morgan, 1996; Langmuir, 1997). Variations

in the intensity and style of fracturing, which should be expected in watersheds that host
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structurally controlled mineral deposits, can lead to changes in infiltration, ground water flow,

and ground water discharge within a watershed. 

2.3.3 Surface Water Hydrology and Hydrogeology

A detailed discussion of characterization and measurement of surface water hydrology and

hydrogeology is presented in Appendix A, Hydrology. Hydrological and hydrogeological

processes and their accurate characterization are inherently related to the characterization and

identification of potential impacts to important resources such as receiving water quality, aquatic

life, vegetation, and wetlands. Watershed hydrology and hydrogeology need to be well

understood prior to finalizing a program to characterize receiving water quality. Important

watershed characteristics that should be evaluated include peak storm flow, infiltration-runoff

relations, sediment load, surface water-ground water exchange, water table elevation, ground

water recharge and discharge, aquifer confinement, and the extent of dewatering activities.

2.3.4 Aqueous Chemistry

The extent to which receiving waters disperse contaminants through the environment

depends partly on water chemistry and soil character (Hutchinson and Ellison, 1991). Under

equilibrium conditions, surface and ground waters will acquire constituent concentrations that

depend on local physical and chemical conditions, the rate at which secondary phases precipitate

from solution, and the tendency for dissolved constituents to sorb onto particle surfaces

(Schnoor, 1996). Figure B-1 shows a conceptual physicochemical model of metal transport in a

surface water system illustrating the complex interactions affecting concentration. In general,

waters with comparatively low pH can retain higher concentrations of metals in solution than

neutral waters (Salomons, 1995). Consequently, downstream changes in pH, redox potential, or

other chemical parameters (e.g., in mixing zones) can lead to dissolution or precipitation of

metal-bearing phases or their adsorption or desorption from bottom sediments or from colloidal

precipitates (Oscarson, 1980; Moore et al., 1988; Langmuir, 1997). 

The precipitation of colloidal particles is known to be an important process that should be

evaluated when assessing water quality (Church et al., 1997; Schemel et al., 1998). Colloids are

solid particles with diameters smaller than 1 micron that remain suspended in water due to

Brownian motion (particles move as a consequence ionic attraction and molecular collision). 

Colloidal deposition can occur when particles aggregate into larger masses that can no longer be

suspended by molecular forces. Aggregated particles that have settled to the bed of a stream can

be resuspended during high flow, causing water quality to decline (Boult et al., 1994).

Importantly, most colloidal particles will pass through a 0.45 micron filter and will report as

“dissolved” constituents in water quality analyses. Colloidal particles, particularly iron

oxyhydroxides, readily sorb dissolved metal ions from the water column (e.g., Chapman et al.,

1983; Langmuir, 1997). Although the formation of oxyhydroxide minerals may improve water

quality by facilitating sorbtion of other dissolved metal ions, deposition of colloidal particles

may degrade aquatic habitat quality by coating substrate materials. 
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Figure B-1. Conceptual physicochemical model of metal transport in a river from Schnoor

(1996).
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The stability of colloidal precipitates is a function of chemical parameters such as pH and

redox potential. Consequently, chemical changes occurring in a receiving water, such as in a

mixing zone, can cause colloidal particles to precipitate or to redissolve and release their

adsorbed metal constituents to solution (Church et al., 1997). For example, acidic, metal-bearing

water draining an area of quartz-sericite alteration that flows into a stream with significant

buffering capacity that is draining an area of propylitic alteration can cause iron- and aluminum

hydroxide minerals to precipitate (cf., Chapman et al., 1983; Boult et al., 1994). Even under

natural conditions, water quality in a receiving stream above a mixing zone may have metals

concentrations, alkalinity, pH and redox potential that are different from water below a mixing

zone (Walton-Day, 1998). 

2.4 Using the Watershed-Based Approach

Mine facilities potentially can impact aquatic ecosystems for considerable distances

downstream by dispersing contaminants through receiving waters (Salomans, 1995). To

anticipate the environmental impact that future mining operations may have and to determine the

impact that past and present operations have had on aquatic ecosystems requires an

understanding at the watershed level (Hughes, 1985). The utility of the watershed approach

recently was recognized in an initiative to remediate abandoned mine lands led by the U.S.

Geological Survey (Buxton et al., 1997) and in EPA’s Hardrock Mining Framework (EPA,

1997a).

Water quality may vary within a watershed in response to differences in factors such as

surficial geology, hydrogeology, infiltration-runoff relationships, seasonal variation, vegetation,

land use, and anthropogenic disturbance. As a result, water quality in the downstream portion of

a watershed is a mix of the components contributed from each upstream tributary. The

watershed-based approach seeks to identify how changes occurring in one or several upstream

tributaries impact downstream water quality. It is important to note that the term “watershed”

does not necessarily refer to an enormous expanse beyond the reach of the operation. In general,

the "watershed" of concern is the upstream portion of a drainage basin that contributes surface

and shallow ground water flows to the project area and the downstream portion(s) whose water

quality or quantity may be affected by mining-related activities. Under the generally accepted

clarification system established by the U.S. Geological Survey, cataloging units appear to be the

most appropriate size of "watershed" that may need to be evaluated for the majority of mining

projects (see USGS Information Sheet Hydrologic Units, February 1999). 

2.4.1 Determining Pre-Mining Background Water Quality

Prior to developing a program to characterize baseline conditions, it is important to

recognize the physical variables that may influence water quality in potentially affected

watersheds. Among the most important of these are the presence of mineralized exposures, the

history and nature of existing disturbances that have caused impacts to water quality, and

changes in watershed hydrology. “Natural background” is a term used to describe the water

quality of a watershed that has not been disturbed by the actions of man (U.S. EPA, 1997b). In

contrast, “anthropogenic background” is a term used to describe the water quality existing in all
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B-12 January 2003

or a portion of a watershed that has been disturbed by human actions. The term “baseline” is

used to describe the water quality measured at a given point prior to future disturbance and from

which departures can be measured. Baseline values may include components of both natural and

anthropogenic background.

2.4.1.1 Natural Background in Mineralized Areas

Natural background levels of metals can be high and pH can be low in streams draining

watersheds with exposed mineralized rock (Runnells et al., 1992, Bowers and Nicholson, 1996;

Mast et al., 1998; Runnells et al., 1998). These characteristics generally are attributed to the

weathering and erosion of metal-bearing ores at the earth’s surface (Runnells et al., 1992;

Bowers and Nicholson, 1996). In some cases, weathering locally produces streams that are

discolored with precipitating metal phases such as ferric hydroxide and zinc carbonate (Runnells

et al., 1992). Runnells et al. (1992) compared metals values in stream waters draining areas with

exposed metallic mineral deposits to worldwide averages determined for streams draining

nonmineralized areas. They found that streams in mineralized areas can have natural pH values

of less than 3 and metals values that are 3 to 4 orders of magnitude higher than streams draining

nonmineralized areas.

Determining natural background values in a watershed requires knowledge of the geological

relationships throughout the watershed, including the distribution, intensity and character of

mineralization and alteration, water quality as it relates to natural variations in stream flow,

precipitation-runoff relationships, downstream changes in water quality, interactions between

surface and ground waters, and the forms in which metals occur in surface and ground waters. 

For example, variations in the distributions and abundances of metallic minerals will influence

the concentrations of metals in surface waters. This is especially true of partially oxidized

hydrothermal deposits in which natural weathering processes have converted primary sulfide

minerals to variably soluble secondary oxide, hydroxide, or carbonate minerals. Moreover,

watersheds in which mineralization occurs in a structurally complex geologic setting may have

tributary streams with distinctive water quality characteristics that may be due to the exposure of

different rock types in different portions of the watershed. Metals are transported in streams

either as dissolved constituents or as suspended particles. The predominance of one form or the

other partly reflects the solubility and erodibility of the metal-bearing minerals and the surface

water chemistry (e.g., redox state, pH, speciation, adsorptive properties, and degree of

saturation). Consequently, changes in stream discharge may have different effects on the

concentrations of dissolved and suspended constituents. Typically, increased flow dilutes the

concentrations of dissolved metals but increases the concentrations of suspended metals by

entraining metal-bearing particles. 

The recently documented Red Dog Mine area, located in northwestern Alaska, provides an

example of surface waters with naturally high concentrations of metals. The main ore deposit,

located in the Red Dog Creek watershed, is a massive lead and zinc sulfide orebody exposed in

the upper portions of the Middle Fork of Red Dog Creek sub-basin. Studies conducted prior to

mining found that a large portion of the watershed comprising the North Fork tributary was

unaffected by the mineral deposit. However, these studies also found that water quality was
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degraded in the portion of the watershed downstream of the ore deposit as a result of weathering

and erosion of the exposed mineralized rock. Seasonal effects on water quality were apparent. 

Studies by Dames & Moore (1983) showed that dilution decreased the natural concentrations of

cadmium and zinc, which were present primarily as dissolved constituents, as flow increased

from snowmelt and precipitation runoff. In contrast, the concentrations of aluminum and lead,

which were present primarily as particulates, increased with increasing stream flow because

metal-bearing particles were mobilized and carried in suspension by high flows. A clear

understanding of the natural background conditions at the proposed mine site proved critical in

the preparation of the EIS and NPDES permit for the Red Dog project. 

The Red Dog site provides an example of extremely elevated natural background metals

concentrations. In most locations, the effects of mineralization on natural background are

expected to be much more subtle. Nevertheless, even small departures are important to

recognize for the EIS and NPDES permitting processes.

2.4.1.2 Effects of Historic Mining and Other Anthropogenic Disturbances

In many mining areas, historic mining disturbances greatly complicate efforts to determine

background geochemical values (Church et al., 1998; Mast et al., 1998). Historic mining

activities or other anthropogenic disturbances can alter natural background constituent

concentrations in a watershed by disturbing soils and slopes, altering runoff and stream

characteristics, and creating mine pits, adits, waste rock dumps, tailings piles, spent leach pads,

and other facilities that are sources of metals and other pollutants. These activities lead to

increased sediment loads (e.g., by removing vegetation); seeps, runoff, and surface discharges

(e.g., from an adit) with elevated levels of acidity and/or metals; and downstream transport and

deposition of leachable materials (e.g., tailings solids). 

In watersheds with numerous historic facilities, it may be difficult to find surface or ground

water sites that have not been affected. A program designed to acquire samples from

undisturbed sites may provide data that apply only to the local area or sub-basin from which the

samples were collected and not to the entire watershed (Mast et al., 1998). In fact, historic

mining disturbances may be so extensive in some areas that it is nearly impossible to fully

characterize background values. Runnells et al. (1998) review methods that can be used to

determine background at extensively disturbed sites. The most desirable of these is to use

historical water quality data. Unfortunately, such data are rarely available or sufficiently

complete that they provide an accurate assessment of pre-mining values. Consequently, three

indirect methods have been developed to provide some measure of understanding of natural

background conditions. One method extrapolates data from an analog site in a nearby

undisturbed watershed (Hughes, 1985; Runnells et al., 1992; Bowers and Nicholson, 1996). 

Such sites must have geological and hydrological characteristics that are similar to those of the

watershed of interest. Although analog sites can provide useful data, it is usually difficult to find

an exact hydrologic and hydrogeological match (Runnells et al., 1998). A second method uses

equilibrium geochemical models to predict the maximum constituent concentrations that can

occur in water that is in equilibrium with rock and metallic ore minerals (Runnells et al., 1992;

Nordstrom et al., 1996). Geochemical models require that users establish boundary conditions
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and make other assumptions (e.g., regarding pH, redox state, etc.) that cannot be easily tested or

verified (Runnells et al., 1998). A third method uses a statistical approach to identify the natural

background component in water from disturbed areas (Runnells et al., 1998). For example,

probability graphs (Stanley, 1987) have been used to identify natural background values in

anthropogenically impacted ground waters at the Bingham Canyon Mine in Utah (Runnells et

al., 1998). Although statistical methods are capable of identifying multiple concentration

populations, the process can become very complicated for areas where surface waters are

impacted by numerous mining features. Some of these challenges are described by Moore and

Luoma (1990) for the Clark Fork River drainage in Montana.

Church et al. (1998) describe an innovative, indirect approach for determining the extent to

which historic mining activities may have affected baseline metals concentrations in a

watershed. Their method is to collect and analyze sediment cores from stream deposits formed

prior to the onset of mining activities and to compare these values to those obtained from

recently formed deposits. In addition to metals and other constituents, sediments can be

analyzed for signs of biotic life. This approach provides data only about stream sediment

compositions and does not provide direct information on water quality.

In addition to mining, there can be a wide range of other existing disturbances in a

watershed that affect water quality. Understanding the effects of all disturbances is essential to

producing an adequate characterization of baseline conditions. Depending on the specific

setting, this may necessitate collecting samples of runoff and seepage, pore waters, and solids. 

In some cases, water quality may be controlled by a set of interactive processes that need to be

recognized in order to predict future water quality changes. For example, Paschke and Harrison

(1995) describe an area of historic mining in Colorado in which metal transport in a stream is

affected by ground water interaction and seasonal recharge of a natural wetland. Without such

information, it may be impossible to predict and measure the incremental effects of new

operations.

3.0 DESIGNING A WATER QUALITY MONITORING PROGRAM

Several factors must be considered when designing and establishing programs to sample and

characterize baseline water quality conditions and to conduct long-term water quality

monitoring. These factors include: (1) the location of the proposed or existing mine site and its

support and waste disposal facilities in relation to the watershed, natural drainages, aquifers, and

ground water flow; (2) the location of proposed or existing discharges and expected areas of

infiltration; (3) the type of mineral to be mined and the mineralogy of associated waste rock and

ore; (4) the type of process chemicals and hazardous materials that will be associated with the

operation; (5) the designated uses of all surface waters in the watershed; and (6) the utilization of

ground water in potentially impacted aquifers. A complete water quality data set will expedite

establishing water-quality-based effluent limits and total maximum daily load allocations, which

may be required by a National Pollutant Discharge Elimination System (NPDES) permit (EPA,

1996a).
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In general, monitoring programs should achieve the following objectives:

C Define spatial differences in water quality parameters and constituents throughout the

watershed.

C Define temporal differences in water quality that result from general changes in

seasonal flow.

C Define differences in water quality that can occur during major climatic events, such

as low probability storms or droughts.

C Define the effects of mining operations and associated accidental or permitted

discharges on water quality.

C Define and monitor the effectiveness of applied Best Management Practices and

mitigation measures used by the operation to protect water quality.

3.1 Sampling Locations

A surface water sampling program should define the number and locations of monitoring

stations on a watershed basis. Monitoring stations should be established on all major tributaries

in a watershed to quantitatively measure spatial changes in water quality that result from

variations in geology, soils, mineralization, and land cover and from historic mining operations

and other land use disturbances. Existing water quality should be well characterized in potential

mixing zones and at downstream points of compliance. Consequently, monitoring stations

should be established above and below a proposed or existing mine site and immediately below

the confluences of all major tributaries. These locations will provide the types of data needed to

define the contributions of different flows to downstream water quality and the water quality

changes that occur as two flows mix together. To the greatest practical extent, monitoring

stations should be located on straight, hydraulically stable stream reaches that are free of pools

and large depositional areas. This will minimize the possibility that samples may vary over time

due to streambank erosion, sediment aggradation, and channel (thalweg) migration. 

Surface water monitoring stations also should be established above and below permitted

discharge points and all hydrologic control structures, such as stream diversions, storm water

detention/retention facilities, tailings disposal facilities, or process ponds. These stations are

usually required for compliance monitoring. It is important to note that ambient and compliance

monitoring programs should be established with common objectives, measured constituents,

sampling frequency, laboratory procedures, and detection limits.

Ground water quality monitoring locations should be established in each potentially affected

aquifer after considering the lithology and permeability of the aquifer; how, in what direction,

and at what speed water flows through it; and whether exchanges occur with surface or other

ground waters. Special considerations may be required for shallow aquifers that exhibit seasonal

flow in response to spring snowmelt or winter freeze. In general, ground water monitoring

requires that data be collected from wells that are located both up-gradient and down-gradient of

potential contaminant sources. Existing water quality should be well established in areas that

could be impacted by seepage from mine facilities. Numerous publications are available that
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B-16 January 2003

describe the design and construction of monitoring wells and provide guidance on programs to

monitor ground water (e.g., Nielson, 1991; U.S. EPA, 1993a; 1993b). 

Lakes, estuaries, bays, and other tidal areas have unique chemical, physical, and biological

characteristics that need to be identified prior to establishing sampling locations. For lakes, this

likely will require applicants to complete limnological studies that characterize seasonal

biological processes and identify physical phenomena such temperature stratification,

evaporation, degree of mixing, sediment-water chemical exchange, chemical stratification

(particularly dissolved oxygen), retention time, and ground water inflow (e.g., Thomann and

Mueller, 1987; U.S. EPA, 1990). Additional factors such as tidal currents and temperature,

salinity, and density gradients are important in estuaries, bays and other near-shore waters (e.g.,

Thomann and Mueller, 1987; U.S. EPA, 1992). These types of data are fundamental for

establishing sites that will provide representative samples and they form a basis for interpreting

the results of water quality analyses.

3.1.1 Mixing Zones

Proposed mixing zones, as defined in Section 2.2, should be characterized as part of the

monitoring program. Importantly, mines may be located in areas with highly variable flow

conditions that can cause the effects and extent of mixing to change significantly with time. In

this regard, water quality immediately above a proposed outfall and mixing zone should be

assessed at the time of highest risk. For many dissolved constituents, this typically occurs under

conditions of low flow. In contrast, highest risk for constituents carried as suspended particles

occurs under conditions of high flow. Developing an accurate understanding of high risk

conditions requires that data be collected for as long as possible to adequately characterize

seasonal and annual variations in runoff and stream flow that occur in all environments. 

Applicants requesting mixing zones in lakes, estuaries, bays, or other tidal areas may need to

conduct limnological or oceanographic studies that characterize the physical and chemical nature

of these environments. 

Most States allow mixing zones as a matter of policy, but limit the spatial dimensions of

permissible zones. Each is reviewed on a case-by-case basis. State regulations regarding the

dimensions permitted for flowing waters (rivers and streams) may differ from those for stillwater bodies (lakes, estuaries, coastal waters). Applicants should check with State personnel

early in the NEPA and CWA processes to determine the types of data that will be required for a

mixing zone application. More information on mixing zones is available in U.S. EPA (1991).

3.2 Sampling Considerations

The data that are used to assess the quality of surface and ground waters form the

foundation upon which all interpretations of potential impacts rest. Consequently, it is vital that

these data accurately portray water quality. For ambient waters, it may be necessary to use

special sample collection and analysis techniques to measure very low concentrations of trace

constituents. 
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3.2.1 Sampling Methods

A variety of techniques can be used to collect samples of flowing or still surface waters and

ground water from the vadose and saturated zones. Depending on their intended use, samples

may be taken as grab samples, depth integrated samples, composite samples, or continuous

samples. Descriptions of sampling techniques and evaluations of the utility of each are not

presented herein. Instead, the reader should consult one of the many sources dedicated to these

topics such as Hamilton (1978), Canter (1985), Nielson (1991), U.S. EPA (1990; 1992; 1993a;

1993b), or U.S. Geological Survey (1998). 

Many EPA analytical methods require that samples be filtered in the field through a 0.45

:m filter. Depending on the constituents that will be analyzed, samples are then treated to

prevent precipitation of metal compounds, volatilization of organic constituents, or the

production of hydrogen cyanide. These methods are outlined in U.S. EPA (1983; 1986) and

briefly described in Appendix C, Characterization of Ore, Waste Rock, and Tailings.

Importantly, the quality of trace metal data, especially for metals concentrations below 1

part per billion, can be compromised by contamination that occurs during sample collection,

preparation, storage, and analysis. EPA has developed Method 1669 specifically for collecting

samples of ambient waters that will be analyzed for trace metals (U.S. EPA, 1996i). The method

outlines procedures for collecting, filtering, and preserving samples and field blanks that will be

analyzed using low-detection-limit techniques (see Appendix C, Characterization of Ore, Waste

Rock, and Tailings). 

3.2.2 Selecting Parameters

The specific water quality parameters that should be measured by a given operation depend

on the site geology, soils, climate, and vegetation; the mineralogy of the mined ore and waste

rock materials; process methods and chemicals used in the operation; and the designated uses of

and the water quality criteria that apply to the receiving waters. These factors must also be

considered when selecting sampling protocols and laboratory analysis procedures. The suite of

metals analyzed should be based on knowledge gained from baseline sampling and site geologic

studies, including the mineralogy of the ore and waste rock. Table B-2 lists constituents

typically measured at metal mining operations.

The adsorptive behavior of metals in water varies as a function of pH and redox potential,

and soils have different cation and anion exchange capacities. Due to changes in soil

characteristics across a watershed, metals attenuation by soils and sediments will also vary. For

these reasons, a mining operation may need to analyze samples for both total recoverable and

dissolved metals. These data will help to delineate the chemical behavior of specific metals in

the environment and they can be used to define spatial variations in metal loads within the

watershed. These data are required to adequately assess impacts to receiving waters that could

be associated with an accidental discharge of pollutants.
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Table B-2. Water Quality Parameters Typically Measured at Proposed Metal Mining

Sites

 TCLP Metals Other Metals 

Arsenic

Barium

Cadmium

Chromium

Lead

Mercury

Selenium

Silver

Aluminum

Antimony

Beryllium

Cobalt

Copper

Iron

Manganese

Molybdenum

Nickel

Thallium

Zinc

 Major Cations Major Anions 

Boron

Calcium

Magnesium

Potassium

Sodium

Ammonia Nitrogen

Bicarbonate

Carbonate

Chloride

Fluoride

Hydroxide

Nitrite Nitrogen

Nitrate Nitrogen

Orthophosphate

Sulfate

 Other Constituents Other Parameters 

Acidity

Dissolved Oxygen

Total Alkalinity

Free Cyanide

Total Cyanide

WAD Cyanide

Conductivity

Eh

pH

Temperature

SAR

Total Dissolved Solids

Total Hardness

Total Suspended Solids

Turbidity

3.3 Sampling Schedule and Frequency

Sampling of all monitoring stations should occur at a frequency that permits accurate

definition of the changes to water quality that occur seasonally and in response to short-lived

changes in flow. Several years of sampling data typically are required to accurately define

monthly, seasonal, and annual variations. In general, a sampling schedule should be designed to

ensure that water quality data are collected from the range of flows that occur. This will provide

a representative set of data that can be used to support NEPA and CWA requirements. Typically

programs will need to utilize a combination of periodic and opportunistic sampling. Periodic

samples are collected on a regular schedule, for example, monthly. Opportunistic samples,

which should be collected throughout the year, are used to define water quality that occurs

during extremes in the seasonal hydrograph or during short-lived events. For example,

opportunistic sampling should be conducted during high runoff events to determine those

parameters that are diluted by high flow (typically dissolved constituents) and those that occur at

increased concentrations (typically suspended constituents). Opportunistic sampling also can

help to define differences in water quality that occur between high and low stream flow
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conditions and to define water quality on ephemeral and intermittent streams. During high

runoff events, opportunistic sampling can be used to establish a baseline from which to evaluate

the effectiveness of water control structures and BMPs designed to minimize impacts from

erosion and sedimentation.

For some locations, applicants may find it useful to link sampling schedules to stream flow

as defined by seasonal hydrographs. This approach could prove especially beneficial in

watersheds that host a variety of climatic zones due to topographic factors or proximity to

coastal waters and in watersheds with severe climates. For example, orographic effects, which

cause precipitation to increase with elevation in a watershed, are especially important to consider

in coastal and mountainous areas, such as southeast Alaska. Alternatively, mines that are located

in mountainous terrain or in northern climates may experience winter periods with extremely

low stream flows or freeze-over, followed by periods with excessive runoff during the spring

thaw. Mines located in arid or semi-arid areas may experience summer periods with low flow

and short periods of intense rainfall that locally produce large discharges. These effects can

impact water quality and contaminant dispersal as described in Section 2.3.1. 

3.4 Assessing the Health and Diversity of Biota

In addition to characterizing the chemical and physical quality of surface and ground waters,

applicants will need to provide an analysis of the health and diversity of biota in receiving

waters. These analyses are described in more detail in Appendix G, Aquatic Resources. For

proposed mining operations, existing streams may be severely impacted by historic activities. 

Hughes (1985) presents a methodology for determining the health and quality of aquatic life in

streams in which this has occurred. His technique relies on identifying control streams in nearby

unimpacted watersheds that have similar watershed characteristics to the impacted stream. 

Control streams are used as analogs from which the potential biotic and habitat conditions of the

impacted stream are estimated. 

4.0 DATA ANALYSIS

Preparation of Environmental Impact Statements and NPDES permits will require an

analysis of water quality and potential impacts that could result from the proposed project. This

section describes the types of data analyses that may be required under NEPA and the CWA. 

4.1 Contributions of Tributaries and Ground Water to Surface Flow

Applicants may be required to conduct an analysis that constrains the contributions of

tributary drainages and ground waters to surface flow. The objective of this type of analysis is to

identify whether changes in water quality are related to inflows, particularly in sensitive areas

such as proposed mixing zones. Ground water contributions to gaining systems may be

especially difficult to assess since the influent sources may not be amenable to direct sampling

(i.e., ground water seeps into the stream beneath flowing water). The analysis can be further

complicated in historic mining areas located in mountainous terrain where contaminated seepage
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flows through shallow soils in response to seasonal climatic changes or short-lived storm events. 

In cases such as these, the use of dye or salt tracers may provide a clearer understanding of

ground water contributions to stream discharge (e.g., Kimball, 1997). Accurate discharge

measurements are important for computing metal loadings (Section 4.3).

4.2 Translators for Dissolved to Total Recoverable Constituent Concentrations

Applicants and regulatory personnel may encounter the need to express water quality data in

both dissolved and total recoverable (dissolved plus particulate) forms for NPDES permits and

Total Maximum Daily Load (TMDL) allocations. NPDES regulations typically require permits

to list metals limits in total recoverable form (there are exceptions, so applicants should check

with State and Federal agency personnel). On the other hand, EPA may be required to perform

TMDL calculations in which metals are expressed in dissolved form to ascertain that water

quality standards are being met. Accepted methods for translating between dissolved and total

recoverable forms are described in U.S. EPA (1996j).

4.3 Computing Metal Loadings

Constituent concentrations, which are subject to dilution in downstream surface water flows,

provide limited information about the behavior of metals in streams. EPA (1996a) suggests that

this shortcoming can be overcome by considering metals loads, in which the instantaneous load

equals concentration multiplied by discharge:

 L = C * Q

where L is the instantaneous load, C is metal concentration, and Q is stream discharge. The

constituent load downstream of a tributary inflow (LD) is equal to the sum of the upstream loads

(LU) and contributing tributary (LT) loads:

 LD = LU + LT

(EPA, 1996a). An increase or decrease in load reflects an increase or decrease in the mass of the

constituent being transported per unit time. Increases in load along a stream reach can point to

sources of contamination that may be recognized (i.e., tributary inflow) or unrecognized (i.e.,

ground water inflow) during conventional sampling. In contrast, decreases in load suggest that a

constituent is being removed by one or more physical, chemical, or biological processes. 

Physical processes such as sedimentation and sediment transport, chemical processes such as

adsorption and colloidal precipitation, and biological processes such as uptake can cause changes

in metals loads. 

4.4 Other Characterization and Data Analysis Issues

This section briefly describes issues that applicants should be aware of when preparing

summaries of water quality data and when analyzing and interpreting historical water quality.
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4.4.1 Below Detection Limit Values

Water quality data sets characteristically contain analyses in which some constituent

concentrations are reported at values below the method detection limit (MDL). Non-detected

values complicate statistical presentations of summary data and can result in statistically

unsupported biases being incorporated into summary data presentations. The latter occurs

whenever mean and standard deviation values are computed using assumed values (e.g., zero or

one-half MDL) for analyses reported as below the detection limit. Further statistical challenges

are presented by water quality data sets that include multiple detection limit values. 

Computational methods have been developed to deal with data sets containing below

detection limit (BDL) values (Gilliom and Helsel, 1986; Helsel and Cohn, 1988; Helsel, 1990;

Travis and Land, 1990). In general, these approaches assume that constituent values have a

normal or log-normal distribution. Based on this assumption, portions of the distribution

reported with BDL values can be reconstructed using either regression order statistics (Gilliom

and Helsel, 1986), probability plotting methods (Helsel and Cohn, 1988; Travis and Land, 1990),

or maximum likelihood estimations (Cohen, 1959). Extrapolated values are then used to

compute mean and standard deviation values for the constituent populations (Helsel and Cohn,

1988; Helsel, 1990). Appendix B of Helsel and Cohn (1988) describes a probability plotting

method to extrapolate data sets that include multiple detection limits. The method has gained

widespread acceptance for analyzing data with BDL values (e.g., Runnells et al., 1998).

The success with which a substitution method accurately determines the true statistical

parameters of a population depends on how closely the data fit an assumed distribution (Helsel,

1990). Bias and imprecision can be introduced whenever data depart from the assumed

distribution or when data are transformed (e.g., when means and standard deviations are

computed for log-transformed data and then converted back to original units) (Helsel, 1990). 

Helsel and Cohn (1988) and Helsel (1990) compared root mean square errors of the statistical

parameters computed using six methods, including simple substitution for BDL values (e.g., onehalf MDL). They concluded that a robust probability plotting method, in which a distribution fit

to data above the reporting limit is used to extrapolate values below the MDL, provides the best

assessment of population mean and standard deviation. Helsel and coworkers also concluded

that percentile values are best estimated using maximum likelihood estimation procedures. 

Software to compute summary statistical parameters for data that include BDL values using

Helsel’s method is available on the worldwide web at http://www.diac.com/~dhelsel/. 

Simple substitution for non-detected values continues to be widely used and EPA accepts

summary data that are prepared in this manner. Most commonly, values of one-half the

detection limit are used for non-detected values. However, in cases where numerous parameters

are reported as below the detection limit, or where a constituent routinely is not detected, EPA

prefers that applicants use techniques that provide the lowest available detection limits. 
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4.4.2 Using Existing and Historical Data Sets

Water quality data may exist in published and unpublished sources for some mining sites. 

In many cases, these data can provide valuable insight into water quality prior to, and subsequent

to historical land disturbance activities, including historical mining operations. The Agency uses

the term “secondary data” to describe data obtained from other sources. Before using such data,

the data user needs to determine the reliability or quality of the data. It is often difficult to

determine the quality of secondary data because original laboratory reports are not included in

published documents and the analyses were conducted prior to the acceptance of standard

laboratory protocols (see Appendix C, Characterization of Ore, Waste Rock, and Tailings). 

Interpretations of receiving water quality that are based entirely or partly on existing data should

be made cautiously when one or more of the following parameters is unknown: exact sample

location, sample collection method, surface or ground water flow, sample preservation, sample

handling (chain-of-custody), analytical method, analytical detection limit, and lab accuracy and

precision. 

It is important for applicants to recognize that secondary data may not have been collected

pursuant to a Quality Assurance Project Plan (QAPP), which often leads to problems with its

use. In general, applicants should assume that the use of historical or existing data sets, in the

absence of a QAPP or other supporting QA/QC documentation, is unlikely to be adequate to

support permitting and decision-making on a mining proposal. More detail on quality assurance

issues is provided in Section 5.0 of this appendix.

4.5 Geochemical Modeling

The extent to which receiving waters disperse contaminants through the environment

depends partly on water chemistry and soil character (Hutchinson and Ellison, 1991). Under

equilibrium conditions, surface and ground waters will acquire constituent concentrations that

depend on local physical and chemical conditions, the rate at which secondary phases precipitate

from solution, and the tendency for dissolved constituents to sorb onto particle surfaces

(Schnoor, 1996). Figure B-1 shows a conceptual physicochemical model of metal transport in a

surface water system illustrating the complex interactions affecting concentration. In general,

waters with comparatively low pH can retain higher concentrations of metals in solution than

neutral waters (Salomons, 1995). Consequently, downstream changes in pH, redox potential, or

other chemical parameters (e.g., in mixing zones) can lead to dissolution or precipitation of

metal-bearing phases or their adsorption or desorption from bottom sediments or from colloidal

precipitates (Oscarson, 1980; Moore et al., 1988; Langmuir, 1997). Dissolved metals

concentrations also may change through adsorption onto or desorption from the surfaces of soil

particles, especially clays (Hutchinson and Ellison, 1991; Salomons, 1995). The adsorptive

behavior of metals in water commonly varies nonlinearly as a function of pH due to pH control

of precipitation and complexation reactions (Salomons, 1995). Soils have different cation and

anion exchange capacities (which measure of the amount of adsorption that can occur) that are a

function of the amount and type of clay and organic content (Hutchinson and Ellison, 1991). 

Due to changes in soil character across a watershed, metals attenuation by soils also is likely to

vary. 
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Geochemical models can be used to determine the stability of phases in aqueous solutions

under equilibrium conditions, identify whether metals are likely to be adsorbed onto or desorbed

from co-existing solid phases, and calculate the equilibrium composition of natural waters. 

These programs are particularly useful for understanding how changes in pH can affect metals

contents, determining whether metals are likely to precipitate, be adsorbed, or remain as

dissolved constituents, and predicting water quality in mixing zones. Brief descriptions of two

of the more commonly used models are provided below.

MINTEQA2/PRODEFA2

MINTEQA2 (Allison et al., 1991) is an equilibrium geochemical speciation model for dilute

aqueous systems. It can be used to compute the mass distributions between dissolved, adsorbed,

and solid phases under a variety of conditions. The software includes an interactive program

(PRODEFA2) to create input files. MINTEQA2 can be obtained from EPA’s Center for

Exposure Assessment Modeling, ftp://ftp.epa.gov/epa_ceam/wwwhtml/minteq.htm. 

PHREEQC

PHREEQC (Parkhurst and Appelo, 1999) is designed to perform a variety of aqueous

geochemical calculations based on an ion-association aqueous model. The software can be used for

calculations of speciation, saturation index, reaction path, and advective transport and to conduct

inverse modeling. PHREEQC is available from the EPA Robert S Kerr Environmental Research

Lab, Center for Subsurface Modeling Support.. 

4.6 Fate and Transport Modeling

Numerical chemical fate and transport models are useful for analyzing spatial changes in

water quality parameters in receiving waters. In general, fate and transport models employ

finite-difference or finite-element techniques to route hydrographs and pollutants through surface

water or ground water systems. These simulations couple equilibrium chemical speciation

models with physical transport equations to calculate downstream or down-gradient changes in

constituent concentrations. These models are especially useful for evaluating the fate and

transport of pollutants from point and non-point sources through a watershed. For mining

operations, such studies can be used to evaluate and model potential operational releases in

conjunction with a NPDES permit application. Brief descriptions of some of the more

commonly used models are provided below.

Enhanced Stream Water Quality Model with Uncertainty Analysis (QUAL2EU)

QUAL2EU is a chemical fate and transport model for conventional pollutants in branching

streams and well-mixed lakes. The program, which is intended to be used as a water quality

planning tool, can be operated in either the steady state or dynamic mode. The software is

available on the world wide web through EPA’s Center for Exposure Assessment Modeling

(ftp://ftp.epa.gov/epa_ceam/wwwhtml/softwdos.htm).
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One-dimensional Transport with Inflow and Storage (OTIS)

OTIS is an equilibrium transport model developed by the U.S. Geological Survey that has

been applied to small streams in Colorado that have been contaminated by mine drainage

(Runkel et al., 1996). The program allows users to subtract the effects of one or more input

sources from downstream water quality. 

Hydrologic Simulation Program FORTRAN (HSPF)

HSPF simulates hydrologic and water quality processes on pervious and impervious land

surfaces, in the soil profile, and in streams and well-mixed impoundments. The operational

connection between the land surface and the instream simulation modules is accomplished

through a network block of elements. Time series of runoff, sediment, and pollutant loadings

generated on the land surface are passed to the receiving stream for subsequent transport and

transformation simulation. Water quality and quantity can be evaluated at different segments or

outflow points within a watershed. Given appropriate input data and constraints, the model can

account for degradation (i.e., decay) or retardation of pollutants. HSPF is available on the world

wide web through EPA’s Center for Exposure Assessment Modeling,

ftp://ftp.epa.gov/epa_ceam/wwwhtml/softwdos.htm.

Finite Element Model Water (FEMWATER)/Finite Element Model Waste (FEMWASTE)

FEMWATER is a numerical ground water model that uses a finite-element solution to solve

the governing equations for ground water flow. It can be used to create two-dimensional areal or

vertical models as well as three-dimensional models in both saturated and unsaturated media. 

Because of its numerical approach, it can be used to model transient flow or steady-state flow

under anisotropic and layered aquifer conditions. FEMWASTE is a two-dimensional transient

model for the transport of dissolved constituents through porous media. Modeled transport

mechanisms include convection, hydrodynamic dispersion, chemical sorption, and first-order

decay. The waste transport model is compatible with the water flow model (FEMWATER) for

predicting convective Darcy velocities in partially saturated porous media. Outputs from ground

water fate and transport modeling can be used to develop pollutant input parameters for point or

non-point sources to surface water fate and transport models such as QUAL2EU or HSPF. 

FEMWATER is available on the world wide web through EPA’s Center for Exposure

Assessment Modeling (ftp://ftp.epa.gov/epa_ceam/wwwhtml/softwdos.htm).

4.7 Other Analysis Techniques

Plots of water quality data can reveal potentially significant changes in constituent

concentrations and mass loading that occur downstream through a watershed (spatial trend) or

that occur with seasonal changes in discharge at a given point within a watershed (temporal

trend). Mass loading profiles (constituent load vs. distance downstream) are particularly useful

for identifying reaches of a stream in which metals are being removed by chemical reaction or

reaches affected by contaminant inflow (for example, ground water impact in a gaining stream)

(Walton-Day, 1998). Mass loading profiles are being used by scientists at the U.S. Geological
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Appendix B: Receiving Waters

B-25 January 2003

Survey to identify and rank contaminant sources and to guide efforts to remediate abandoned

mine lands in the Arkansas drainage in Colorado (Kimball, 1997). Plots of constituent

concentration vs. discharge or total suspended solids (TSS) for a given sampling point can

distinguish elements that are transported as dissolved constituents from those present primarily

as suspended particles. 

Although not a widely used technology, water quality data are amenable to analysis using a

geographic information system (GIS). GIS technology is being incorporated into the U.S.

Geological Survey’s National Water Quality Assessment Program where it is used to manage

large water quality databases and produce graphical data presentations (Qi, 1995; Qi and

Sieverling, 1997). At the watershed scale, a GIS can facilitate analysis of spatial variations in

water quality and the relationships of water quality to rock, soil, and mine waste compositions. 

5.0 GUIDANCE FOR PREPARATION OF A QUALITY ASSURANCE PROJECT PLAN

(QAPP)

This section describes the need for and preparation of a Quality Assurance Project Plan

(QAPP) for monitoring receiving waters. The section provides an overview of the planning

process that is used to develop a QAPP and describes the major components of a QAPP. EPA

QA/G-5 Guidance on Quality Assurance Project Plans (EPA/600/R-98/018, February 1998)

provides guidance on developing Quality Assurance Project Plans (QAPPs) that will meet EPA

expectations and requirements. This document provides a linkage between the Data Quality

Objective (DQO) process and the QAPP. It contains tips, advice, and case studies to help users

develop improved QAPPs. 

5.1 Overview of the Process for Developing a Monitoring Plan

The Agency QA Division recommends the use of a systematic planning process when

developing a monitoring program. One such systematic process is the Data Quality Objective

Process (U.S. EPA, 1994e). MacDonald et al. (1991) and Dissmeyer (1994) also provide

examples of systematic planning approaches that may be applicable to mining projects. Figure

B-2, taken from Dissmeyer (1994), is an example of the process used to develop a program to

monitor receiving water quality. The two steps most critical to developing a sound plan are to

identify specific monitoring goals and objectives and to determine whether the plan, when

implemented, meets those objectives. For example, one objective of a surface water monitoring

plan might be to define temporal differences in water quality that result from general changes in

seasonal flow (see Section 3.0).

Monitoring plans will vary depending on the particular monitoring situation. In general,

they include goals and objectives; sampling locations and schedules; a list of water quality

parameters that will be monitored and their required detection limits; a brief description of

stream morphology at surface water sampling points; sample collection, handling, and analysis

procedures; sample transport and chain-of-custody procedures; quality assurance/quality control

protocols; and data analysis and reporting procedures. 
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Appendix B: Receiving Waters

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The time period from mine planning and permitting to reclamation and post-operational

monitoring typically is measured in decades. During this time, environmental conditions, mine

operations, monitoring requirements, and sampling and analysis protocols are likely to change. 

Therefore, establishing comprehensive quality assurance and quality control (QA/QC) protocols

will help to minimize the impacts of these changes by ensuring that a consistent and accurate

approach is used to collect and analyze receiving water data. Implementing these protocols

through a written plan will help to ensure that the collected data can be used to evaluate both the

short- and long-term quality of receiving waters. 

Although there are numerous approaches for ensuring long-term data quality assurance and

control, the most common (and often required) approach is the development of a either a

Sampling and Analysis (SAP) plan, Quality Assurance Project Plan (QAPP), or both. The SAP

and QAPP can be combined into one document, the purpose of which is to establish sound and

defensible sampling and analysis protocols that can be used to generate unbiased data with

known and traceable accuracy and precision. For the purposes of this appendix, the combined

QA/QC document is referred to as the QAPP. The QAPP should be prepared in a manner that

promotes acceptance and use by field and laboratory personnel. It should serve as a resource

tool and reference manual for all sampling and analytical procedures. The QAPP should be

modified when changes occur that significantly alter the applicability or effectiveness of the

document.

5.2 Components of a QAPP

The primary elements of an acceptable QAPP include comprehensive discussions regarding

Project Management, Measurement and Data Acquisition, Assessment and Oversight, and Data

Validation and Usability. Each of these are described in the ensuing subsections. A complete

explanation of and prescribed format for all required elements is presented in U.S. EPA (1998c;

1998d). Both documents are available on the world wide web

(http://www.epa.gov/r10earth/offices/oea/qaindex.htm). Although monitoring programs initially

are developed to support decision-making and permitting of proposed mining projects, the

formal monitoring programs that are documented in a QAPP can be later used or amended to

support other objectives during various stages of a mine life cycle, including operation, closure

and post-closure. For example, NPDES permits generally include specific requirements for the

preparation of QAPPs to guide collection of water quality data during mine operation. Typically

NPDES permits specify that QAPPs adhere to the two guidance documents cited above.
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Figure B-2. Example flow-chart for developing a monitoring project (from Dissmeyer, 1994).
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B-28 January 2003

5.2.1 Project Management 

The project management portion of the QAPP includes an introduction and sections that

describe the project schedule, training and certification, expected data quality, and data quality

objectives. 

Introduction

The introduction should be informative and provide the foundation for solid QA/QC

procedures. The section should address plan approval, modification, distribution, and project

organization. The introduction should establish procedures for plan modification and identify by

name the individuals responsible for project management, overall project quality assurance, field

work, and laboratory quality assurance. This should be followed by a detailed presentation of

project background information and a brief problem statement. Maps and/or figures should be

provided where appropriate. 

Project Schedule

An overall project schedule should be developed that highlights key project dates, if

applicable. The schedule should be developed in an easily readable format and all projectassociated staff should be aware of its presence, content, and key dates. 

Training and Certification

The QAPP should address staff sampling and safety training and should include a listing of

certifications held by the laboratory. If a commercial laboratory is contracted, it should hold the

relevant certifications for the planned analyses from the state where the project is located. 

Expected Data Quality

Data quality refers to the level of uncertainty associated with a particular data value (i.e.,

how sure are you that the value of the data point is what the analysis has determined it to be?). 

Data quality is affected by all elements of the sampling event, from the sampling design through

the laboratory analysis and reporting. Early in the QAPP development process, the acceptable

and appropriate levels of uncertainty must be determined through the use of a systematic

planning process. Such decisions will depend on the contaminant of concern, the effect it has on

human and environmental health, and the levels at which concerns arise. 

Decisions regarding acceptable levels of uncertainty should consider the following

questions:

• What chemical(s) are expected to be found at the site?

• Approximately what level of contamination is expected (high = >10 ppm; medium =

10 ppm to 10 ppb; low = <10 ppb)? 
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• What is the action level or level of concern for the contaminant for human health? 

For the environment? 

• Based on the answers to questions 1 through 3, which analytical methods are

appropriate to achieve needed detection limits?

• How was the sampling design developed (e.g., area vs. number of samples; frequency

of sampling; random or biased sampling)? 

• How many of the samples will be field quality control samples (i.e., field duplicates,

field blanks, equipment blanks, trip blanks, field spikes or split samples)? 

• How many samples will be laboratory quality control samples?

 

Data Quality Objectives and Data Quality Indicators

After a decision has been made regarding the expected data quality, the QAPP should

address data quality objectives and measurement criteria. Data Quality Objectives (DQOs) are

quantitative and qualitative objectives that define usable data for meeting the requirements of the

project. Data Quality Indicators (DQIs) are specifications for the quality of data needed for the

project, such as sample measurement precision, accuracy, representativeness, comparability, and

completeness. DQOs and DQIs define the quality of the services required from the laboratory

and are used in any quality assurance reviews of the field and laboratory data. Review of the

quality control data against the DQOs and DQIs determines if the data are fully usable,

considered estimates, or rejected as unusable. 

Precision is the degree of mutual agreement between or among independent measurements

of a similar property (standard deviation [SD] or relative percent difference [RPD]). This

indicator relates to the analysis of duplicate laboratory or field samples. 

Accuracy is the degree of agreement of a measurement with a known or true value. To

determine accuracy, a laboratory or field calibration value is compared to the known or true

concentration. The laboratory, by developing a database of instrument runs using performance

samples, should be able provide information regarding this objective.

Completeness compares the data actually obtained to the amount that was expected to have

been obtained. Due to a variety of circumstances, analyses may not be completed for all

samples. The percentage of completed analyses required will depend on the sampling design and

data use. Expectations of completeness should be higher when fewer samples are taken per

event or site.

Representativeness expresses the degree to which data accurately and precisely represent a

characteristic of an environmental condition or a population. It relates both to the area of interest

and to the method of taking the individual sample. The idea of representativeness should be

incorporated into discussions of sampling design. 

Comparability expresses the confidence with which one data set can be compared to

another. The use of standard, published methods allows straightforward comparisons of data

collected during multiple sampling events. 
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Data quality indicators for field and laboratory measurements should be stated in

measurement performance criteria. Field measurements should be made with calibrated

instruments; laboratory measurements should be specified by individual method criteria or by

laboratory control limits. 

5.2.2 Measurement and Data Acquisition

The measurement and data acquisition section describes in detail how, where, and when

data will be collected and analyzed and provides supporting quality control information related

to sample handling; equipment calibration, testing, and repair; analytical methods and quality

control requirements; and data management. This section is particularly applicable to all field

personnel insofar as it establishes required procedures for sample collection and field

measurements. Where possible, information should be presented in tables or other easily

understandable formats and should clearly identify prescribed sample locations; maps are

strongly encouraged. Tables should be created that list the sample site by assigned identifier

(e.g., station 102), common name (e.g., Dry Creek below mill), intended purpose (e.g., assess

effectiveness of treatment), and sample types (e.g., pH, flow, turbidity, etc.). The QAPP should

provide the reason for including specific sample sites and, where necessary, detailed descriptions

of the sample location. Sampling and measurement schedules should be included; tables are

recommended in cases where multiple parameters are sampled on varied schedules. 

Critical and Non-Critical Samples

In some instances, certain samples may be determined to be less critical than others (e.g.,

informational samples versus compliance samples). The collection of critical samples may be

required at all times, while sampling for non-critical samples may be postponed or excluded

based on weather or safety considerations. Criteria for such should be clearly identified. 

Sample Collection

Field sampling and measurement procedures should be completely described at a level that

would permit a new employee to read and implement these activities without jeopardizing the

quality of data. The QAPP should specify methods for collecting different types of samples,

using field equipment, and preparing, preserving, and handling samples. In addition, it should

present information regarding approved sample containers, preservation methods, holding times,

and analytical methods. Proper chain of custody procedures and an example of the form to be

used should be provided. The citation and attachment of Standard Operating Procedures to the

QA plan can reduce the amount of writing that must be done to properly document the details for

a project. For guidance on the preparation of Standard Operating Procedures, refer to U.S. EPA

(1995). Field staff should be thoroughly trained on all elements of field sampling and

measurement and one or more trial events should be conducted prior to initiating unsupervised

sampling.
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Analytical Methods and Quality Control Requirements

The QAPP should specify laboratory analytical methods and quality control procedures. A

preferred approach is to include a table that presents the analytical methods, method detection

limits (MDLs), reporting limits or minimum levels, laboratory precision (in relative percent

difference (RPD)) and accuracy (in % recovery), sample holding times, sample container type,

sample preservation method, and completeness requirements. The table provides a reference for

field teams and allows for easy review of the data deliverables package provided by the

laboratory. EPA has established preferred analytical methods for surface water, ground water,

soils, sediment, and other media (EPA, 1983; 1986; 1996b-i); other methods are described in

APHA et al. (1992) and ASTM (1996) (see Appendix C, Characterization of Ore, Waste Rock,

and Tailings). Method detection limits are specified in the individual method, while reporting

limits or minimum levels are based either upon desired data accuracy and/or regulatory

requirements (e.g., NPDES permit limits). Although precision and accuracy guidelines typically

vary depending on the specific analysis and/or sample media, <10 to <30% RPD and 85 to 115

% recovery are commonly applied values for water samples. 

In addition, the QAPP should specify sample preparation methods and sampling handling

procedures as described in the laboratory’s QA/QC manual or plan. The lab QA/QC plan or

manual should be included with the QAPP as an appendix and pertinent information should be

extracted and included in the text of the QAPP. 

Field Quality Control

Quality control checks of field sampling procedures and laboratory analyses should be used

to assess and document data quality, and to identify discrepancies in the measurement process. 

Field blanks, equipment decontamination blanks, field duplicates (or replicates), trip blanks, and

standard reference samples can be used to assess sample representativeness, sample collection

and handling procedures, field equipment decontamination procedures, and laboratory precision

and accuracy. Field blank samples, which are used to evaluate whether contaminants have been

introduced into the samples by the sampling process, are created by pouring deionized water

through a field filter into a sampling container at the sampling point; the field blanks are

analyzed for metals and other constituents. In some cases, trip blanks may be needed to evaluate

whether shipping and handling procedures introduce contaminants into the samples, or if crosscontamination (e.g., migration of volatile organic compounds) has occurred between the

collected samples. Duplicate samples, which are collected simultaneously with a standard

sample from the same source under identical conditions and placed into separate sample

containers, should be used to assess laboratory performance. One or more duplicate samples

should be collected and analyzed for every 20 samples (5%) or once per sampling event,

whichever is more frequent. The duplicates should be labeled in a way that does not reveal their

status to the laboratory. 
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Laboratory Quality Control

Laboratories routinely monitor the precision and accuracy of their results through analysis

of laboratory quality control samples (EPA Region 10 provides a document for laboratories

entitled “Guidance on Preparation of Laboratory Quality Assurance Plans,” available on the

world wide web at http://www.epa.gov/r10earth/offices/oea/qaindex.htm). The QAPP should

provide a reference to the specific QC protocols used by the labs that will conduct analyses. The

typical frequency specified for laboratory QC samples (e.g., matrix spikes, matrix spike

duplicates, method blanks, lab control samples) is one of each QC sample that is appropriate for

the method per batch of samples. A batch of samples is defined as 20 or fewer samples that are

received by a laboratory within a 14 day period for the specific project. If deemed necessary for

the project, a higher frequency of QC samples can be designated. 

Corrective Action

If nonconformance with any QAPP element is identified, corrective action should be taken

to remedy, minimize, or eliminate the nonconformance. Sampling and measurement system

failures include an inability to collect a sample, sample collection errors, field measurement

errors, and laboratory errors. The QAPP should prescribe remedies for each of these possible

system failures.

Calibration

Field equipment should be calibrated regularly and records should be kept in a field

calibration log. The QAPP should include a list of all equipment requiring calibration (e.g., pH

meters, DO meters, etc.) and appropriate calibration procedures. 

Data Management

Data management requirements should be established for field and laboratory data. They

should include acceptable field documentation procedures, laboratory data deliverables, data

validation techniques and requirements, data entry, electronic data management, and records

retention. The QAPP should present a list of the steps that will be taken to ensure that data are

transferred accurately from collection to analysis to reporting. Discussions should focus on the

measures that will be taken to review the data collection processes, including field notes or field

data sheets; to obtain and review complete laboratory reports; and to review the data entry

system, including its use in reports. 

Chain-Of-Custody

Chain-of-custody records are used to document sample collection and shipment to

laboratories for analysis. All sample shipments for analyses must be accompanied by a

chain-of-custody record. Form(s) should be completed and sent with the samples for each

laboratory and each shipment (i.e., each day). 
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5.2.3 Assessment and Oversight

The QAPP should adequately describe all monitoring program assessment and oversight. 

Oversight evaluates how well the specifications contained within the QAPP are being

implemented and the types of information needed to continuously improve the monitoring

program. It also verifies that the quality assurance guidelines for sampling and analysis are

being met. The QAPP should identify the individual(s) responsible for ensuring that sampling

and QA activities are being implemented as described in the QAPP. The primary elements of an

acceptable assessment and oversight program include audits of field data and sample acquisition,

laboratory audits, and audits of data management. 

Audits of Field Data and Sample Acquisition

Data quality audits assess the effectiveness and documentation of the field and laboratory

data collection processes. In particular, these audits evaluate whether the DQOs established for

the project are being met. Additionally, they determine whether the QAPP is still applicable to

the current project. The frequency of these audits, which may range from daily to annually,

depends on the scope and complexity of the monitoring program. The audit should be performed

by someone who is not associated with the day-to-day implementation of the monitoring plan. 

Laboratory Audits

A review of the laboratory facility, its equipment, personnel, organization, and management,

evaluates the reliability of the data produced by the laboratory. The laboratory, as a system, is

verified against the documentation provided in their QA manual and standard operating

procedures. 

Data Management Audits 

Data management reviews evaluate whether the standard procedures in the QAPP are being

followed and if the integrity of the data is being maintained. Audits should be conducted at least

every other year, but may be conducted more frequently if needed.

5.2.4 Data Validation and Usability

This section of the QAPP states the criteria for deciding whether a data element has met its

quality specifications as described above. Data validation is the process by which data are

compared with DQOs to determine which data points are accepted, rejected, or qualified. 

The data validation and usability determination evaluates sampling design, sample collection

procedures, sample handling, analytical procedures, quality control, calibration, and data

reduction and processing.
EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

Appendix B: Receiving Waters

B-34 January 2003

Validation and Verification Methods

Upon receipt from the laboratory, data should be compared with the specified DQOs and

analytical methods. Corrective actions should be selected to prevent or reduce the likelihood of

future nonconformances and, to the greatest extent practical, address the causes of

nonconformance. Prescribed corrective actions should already exist in the QAPP and these

should be implemented first. Future audits should ensure that similar errors do not recur. 

Reconciliation with DQOs and DQIs

The QAPP should clearly identify the actions that will be taken to reconcile any deviations

from the DQOs and DQIs. Resolution should be made by identifying the elements of the

sampling and data collection process that are in question and addressing the situation that caused

the qualification. 

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EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

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EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

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EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

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EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

Appendix B: Receiving Waters

B-39 January 2003

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R-94-011, June 1994.

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U.S. Environmental Protection Agency, 1994c. Technical Resource Document, Extraction and

Beneficiation of Ores and Minerals, Volume 4, Copper, EPA Report 530-R-94-031.

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Edition, EPA 823-B94-005a, August 1994.

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Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry, Office of

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Inorganic Arsenic in Water by Hydride Generation Flame Atomic Absorption, Office of

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821/R-96-003.
EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

Appendix B: Receiving Waters

B-40 January 2003

U.S. Environmental Protection Agency (EPA), 1996e. Method 1637: Determination of Trace

Elements in Ambient Water by Chelation Preconcentration with Graphite Furnace Atomic

Absorption, Office of Science and Technology, Report 821/R-96-004.

U.S. Environmental Protection Agency (EPA), 1996f. Method 1638: Determination of Trace

Elements in Ambient Waters by Inductively Coupled Plasma-Mass Spectrometry, Office of

Science and Technology, Report 821/R-96-005.

U.S. Environmental Protection Agency (EPA), 1996g. Method 1639: Determination of Trace

Elements in Ambient Waters by Stabilized Temperature Graphite Furnace Atomic

Absorption, Office of Science and Technology, Report 821/R-96-006.

U.S. Environmental Protection Agency (EPA), 1996h. Method 1640: Determination of Trace

Elements in Ambient Waters by On-Line Chelation Preconcentration and Inductively

Coupled Plasma-Mass Spectrometry, Office of Science and Technology, Report 821/R-96-

007.

U.S. Environmental Protection Agency (EPA), 1996i. Method 1669: Sampling Ambient Water

for Trace Metals at EPA Water Quality Criteria Levels, Office of Science and Technology,

Report 821/R-96-011.

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EPA 823-B-96-007, June 1996.

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Assurance Project Plans, EPA 600-G-98-018.

U.S. Environmental Protection Agency, 1998d. EPA QA R-5 EPA Requirements for Quality

Assurance Project Plans, Draft Interim Final Report.
EPA and Hardrock Mining: A Source Book for Industry in the Northwest and Alaska

Appendix B: Receiving Waters

B-41 January 2003

U.S. Geological Survey, 1998. National Field Manual for the Collection of Water-Quality Data,

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EPA, Denver, CO, August 24 to September 4, 1998.