Water Sources - Additional Reading PDF

Introduction to Water Sources Chapter 3 What Is In This Chapter? 1. Definition of surface water 2. Examples of surface water 3. Advantages and disadvantages of surface water 4. Surface water hydrology 5. Raw water storage and...

Introduction to Water Sources Chapter 3 What Is In This Chapter? 1. Definition of surface water 2. Examples of surface water 3. Advantages and disadvantages of surface water 4. Surface water hydrology 5. Raw water storage and flow measurements 6. Surface water intake structures 7. The types of pumps used to collect surface water 8. Definition of groundwater 9. Examples of groundwater 10. Advantages and disadvantages of groundwater 11. Groundwater hydrology 12. Three types of aquifers 13. Well components 14. Data and record keeping requirements 15. Transmission lines and flow meters 16. Groundwater under the direct influence of surface water Key Words Aquifer Flume Porosity Surface Water Baseline Data Glycol Raw Water Unconfined Aquifer Caisson Groundwater Recharge Area Water Rights Cone of Depression Impermeable Riprap Water Table Confined Aquifer ntu Spring Watershed Contamination Parshall flume Static Water Level Weir Drainage Basin Permeability Stratum Drawdown Polluted Water Surface Runoff  62 Chapter 3 Introduction to Water Sources Introduction This lesson is a discussion of the components associated with collecting water from its source and bringing it to the water treatment plant. Lesson Content 1 Surface Water – Water on the earth’s This lesson will focus on surface water1 and groundwater2, hydrology, and the ma- surface as distinguished from water underground (groundwater). jor components associated with the collection and transmission of water to the water 2 Groundwater – Subsurface water treatment plant. occupying a saturated geological for- mation from which wells and springs are fed. Sources of Water Three Classifications The current federal drinking water regulations define three distinct and separate sources of water: Surface water Groundwater Groundwater under the direct influence of surface water (GUDISW) This last classification is a result of the Surface Water Treatment Rule. The definition of what conditions constitute GUDISW, while specific, is not obvious. This classifi- cation is discussed later in this lesson. Surface Water Definition Surface water is water that is open to the atmosphere and results from overland flow. 3 Surface Runoff – The amount of It is also said to be the result of surface runoff 3. These are two ways of saying the rainfall that passes over the surface of the earth. same thing. Examples of Surface Water Specific sources that are classified as surface water include the following: Streams, Rivers, Lakes Man-made impoundments (lakes made by damming a stream or river) 4 Spring – A surface feature where, Springs4 affected by precipitation that falls in the vicinity of the spring (af- without the help of man, water issues fected means a change in flow or quality) from rock or soil onto the land or into a body of water, the place of issu- Shallow wells affected by precipitation (affected means a change in level or ance being relatively restricted in size. quality) Wells drilled next to or in a stream or river Rain catchments Muskeg and tundra ponds Advantages and Disadvantages of Surface Water There are both advantages and disadvantages to surface water: Advantages – The primary advantages to using surface water as a water source include the following: It is easily located. It takes no sophisticated equipment to find a surface water source.  Chapter 3 Introduction to Water Sources 63 In many parts of the US, considerable data is available on quantity and qual- ity of existing surface water supplies. Surface water is generally softer than groundwater, which makes treatment much simpler. Disadvantages – The most common disadvantages to using surface water as a water source include the following: Surface waters are easily polluted5 (or contaminated) with microorganisms 5 Polluted Water – Water than con- tains sewage, industrial wastewater, that cause waterborne diseases and chemicals that enter the stream from sur- or other harmful or objectionable face runoff and upstream discharges. substances. The turbidity (measured as NTU6) of a surface water source often fluctuates 6 NTUs – The units of measure of with the amount of precipitation. Increases in turbidity increase treatment turbidity, Nephelometric Turbidity Units, the measurement as made with cost and operator time. a nephelometric turbidimeter. The temperature of surface water fluctuates with the ambient temperature. This makes it difficult to produce consistent water quality at a water treat- ment plant. The intake structure may become clogged or damaged from winter ice, or the source may be so shallow that it completely freezes in the winter. This is a common problem with surface water sources in the arctic. Removing surface water from a stream, lake, or spring requires a legal right, referred to as a water right. Water rights7 in Alaska are obtained from the 7 Water Rights – The rights, acquired under the law, to use the water ac- Department of Natural Resources (DNR). cruing in surface or groundwater, for For many systems in Alaska, the source water is at its worst possible qual- a specified purpose in a given manner ity during the time of the year when the community needs to fill or top off and usually within the limits of a given time period. its storage tank. This happens late in the summer when glacially fed streams have turbidities of 1000 ntu or greater. Using surface water as a source means that the purveyor is obligated to meet the requirements of the Surface Water Treatment Rule (SWTR) of the State Drinking Water Regulations. This rule requires that, in most instances, any surface water source must have a filtration system. Surface waters that are high in color, especially color that is the result of decaying vegetation, have the potential to produce high levels of Total Triha- lomethanes (TTHM). These chemical compounds are formed when chlorine is added to the water. The problem with the TTHM is that some of them are carcinogenic (can cause cancer) and are referred to as disinfection by-prod- ucts (DBP). Surface Water Hydrology Introduction A basic understanding of the movement of water and the things that affect water quality and quantity are important to those who manage and operate water systems. The study of these items is called hydrology. The components of hydrology include 8 Drainage Basin – An area from which the physical configuration of the watershed, the geology, soils, vegetation, nutrients, surface runoff or groundwater re- energy, wildlife, and the water itself. charge is carried into a single drainage system, also called a catchment area, watershed, or drainage area. Drainage Basin 9 Watershed – A drainage basin from The area from which surface water flows is called a drainage basin8. With a sur- which surface water is obtained. face water source, this drainage basin is most often called the watershed9. When we 10 Recharge Area – One from which precipitation flows into the under- are dealing with a groundwater supply, this area is called the recharge area10. The ground water sources. 64 Chapter 3 Introduction to Water Sources drainage basin is difficult to identify when we are referring to a large river such as the Yukon. However, on a smaller river, stream or lake the area is defined by marking on a map an outline of the basin defined by the ridge of the mountains that surround the basin. AREA OF RECHARGE A T ER S W HED Review 1. What are the three sources of drinking water? 2. What do the letters GUDISW mean? 3. A muskeg pond is an example of what type of water source? 4. What are two of the advantages of surface water sources? 5. The study of the properties of water - its distribution and behavior - is called? 6. What is the area called that directly influences the quantity and quality of surface water? Area Measurements The area of the basin is commonly measured in square miles, sections, or acres. If you are taking water from a surface water source, it is desirable to know the size of the watershed. Location of the Basin A parcel of ground such as a drainage basin can be identified by and described by standard terms used in land descriptions and surveying. This description is based on a series of horizontal and vertical lines that form a rectangle system. The ability to describe properly the location of a drainage basin, well, or surface water intake is important when communicating with the Department of Natural Resources (DNR) and ADEC.  Chapter 3 Introduction to Water Sources 65 Baseline Data Gathering precipitation and flow data plus water quality data is called baseline data11. This data is essential for long-term planning and determining the impact of activities in a drainage basin. Raw Water Storage Purpose Raw water12 storage areas are constructed to meet peak demands and/or to store wa- 11 Baseline Data – The water quality ter to meet demands when the flow of the source is below the demand. data, precipitation data, and stream flow data accumulated from a drainage basin or groundwater supply when Natural Storage there is little or no activity in the area. 12 Raw Water – Water that has not Natural storage can be found in lakes like the one used by Haines and large rivers been treated and is to be used, after like the Yukon used by St. Mary’s. Natural storage includes muskeg and tundra ponds treatment, for drinking water. used by logging camps in the Southeast, in oil field camps, and by resorts in the arctic region. Man-made Storage In many areas, there are no natural storage areas, and dams must be built. These dams can be either masonry or embankment dams. There are three different concrete masonry dam designs: Gravity dam Buttress dam Arched dam Gravity dam Buttress dam Arched dam  66 Chapter 3 Introduction to Water Sources In Alaska, the most common dam used for potable water is a concrete gravity dam less than 30 feet in height. Examples of concrete dams can be found at the City of Craig and Port Alexander. Embankment Dams Embankment dams are made from local materials. The key to an embankment dam 13 Impermeable – Not allowing, or is a tightly compacted impermeable13 clay core. This core is held in place either allowing only with great difficulty, the by rock or earth. When rock is used, the dam is called a rock fill embankment dam. movement of water. 14 Riprap – Broken stones or boulders Riprap14 is placed on the face of the dam to prevent erosion by the water. The major placed compactly or irregularly on advantage to this type of construction is its ability to give with small movements of dams, levees, dikes, etc. for the protec- the earth. tion of earth surfaces against the action of the water. RIPRAP CLAY GRAVEL CORE GRAVEL SAND SAND CLAY PERVIOUS ALLUVIUM CUT-OFF BEDROCK Man made impoundment resulting from an embankment dam An example of an embankment dam is the village of Saxman, which uses a small embankment dam for holding its drinking water. Raw Water Storage Tanks In many locations in the arctic region, it is common to use a large man-made storage tank to store raw water for use during the winter months. These structures normally hold one million gallons or more and are made of wood or steel.  Chapter 3 Introduction to Water Sources 67 Wood tank Steel tank Flow Measurements Introduction The flow in a stream or river can be measured using primary devices such as weirs15 15 Weir – A vertical obstruction, such as a wall or plate, placed in an open and flumes16 on small streams or secondary devices called current meters on larger channel and calibrated in order that a streams. depth of flow over the weir (head) can easily be measured and converted into flow in cfs, gpm, or MGD. Weirs 16 Flume – An open conduit made “V” notch weir A weir is a plate made of wood or metal. These of wood, masonry, or metal and constructed on grade that is used to plates are places in the stream plumb and level. transport water or measure flow. They are identified by their shape. Typical shapes are rectangular, “V” notch, and cipol- letti (a trapezoidal shaped weir), with the “V” notch and the cipolletti shapes being the most common. Flumes Flumes are not as common as weirs. They are useful on very small streams and in loca- tions where the restriction caused by the weir represents a problem to the habitat of the stream. Flumes must be installed perfectly level and plumb. Flume Types There are two common types of flumes used to measure stream flow: rectangular and Parshall17. The Parshall flume is the most common and is used in water and waste- 17 Parshall Flume – A device used to water treatment plants to measure flow. measure flow in an open channel. The flume narrows to a throat of fixed dimension and then expands again. The flow is determined by measuring the difference between the head before and at the throat. Parshall Flume 68 Chapter 3 Introduction to Water Sources Surface Water Intake Structures Location Criteria Regulations and Standards In order to protect high quality drinking water, the water works industry has devel- oped standards and specifications for separation of the intake from potential sources of contamination. In addition, the Alaska Department of Environmental Conservation has established minimum separations distances from sources of contamination. The following listing includes industry standard practices as well as those items included in the ADEC regulations: There can be no wastewater disposal systems, including septic tanks and drain fields, within 200 feet of the intake for CWS, NTNCW, or TNCWS systems and 150 feet for Class C systems. There should be no community sewer line, holding tanks, or other potential sources of contamination within 200 feet of the intake of a CWS, NTNCW, or TNCWS system or within 100 feet in a Class C system. Fuel not used for on-site emergency pumping equipment or heating cannot be stored within 100 feet of the well for a CWS, NTNCW, or TNCWS system or within 75 feet of the well for a Class C system. Fuel for onsite emergency generators or building heating system can be stored onsite if the total volume is less than 500 gallons. Recommendations The following are recommendations and not regulations: The water purveyor should own or have a restricted area within 200 feet radius of the intake. There should be no roads within 100 feet of the intake. Structures The intake structure is used to collect the raw water from the source and place it into the transmission line. The types of intake structures used in the water industry vary greatly to meet the specific needs and construction conditions of each site. The following discussion will explore a few of the most common types as they apply to small streams, lakes, rivers, and reservoirs. Small Streams Small Dam One of the most common intake structures on a small stream is a small gravity dam placed across the stream. Water behind the dam can be removed by a gravity line or pumps. This type of system is susceptible to ice damage in the winter. Diversion in Stream A second common intake for a small stream is a diversion of some type built next to the stream. Water is collected in the diversion and either carried away by gravity or pumped from a caisson. This type of intake is sometimes called a submerged intake. River Float A common intake on small and large streams is to use an end-suction centrifugal pump or submersible pump placed on a float. The float is secured to the bank, and water is pumped to a storage area. In the winter, the float is replaced with a hole in the ice and a platform for holding the pump controls.  Chapter 3 Introduction to Water Sources 69 Submerged intake Floating intake Johnson Screen One of the simple intake structures used on muskeg ponds and small streams is a sec- tion of Johnson screen placed on the end of a swing joint. The operator can select the best location of the pipe, raising and lowering it by a mechanical arm attached to the swing joint. Johnson screen  70 Chapter 3 Introduction to Water Sources Infiltration Gallery Description There are several uses and designs for the infiltration gallery. These include intake structures for a spring and intake structures placed in the bed of a stream. The most common infiltration galleries are built by placing Johnson well screens or perforated pipe into the streambed or water-bearing strata. The pipe is covered with clean graded gravel. As water percolates through the gravel, a portion of the turbidity and organic material is removed. PUMP HOUSE Caisson STREAM Infiltration gallery Infiltration – Caisson The water collected by the perforated pipe flows to a caisson placed next to the 18 Caisson – Large pipe placed in a stream. The water is removed from the caisson18 by gravity or pumping. vertical position. Other Intakes Springs A common method of collecting water from a spring is to dig back into the mountain and place Johnson screens or perforated pipe into the water-bearing strata. This is then covered with clean washed rock and sealed with clay. The outlet is piped into a spring box. Roof Catchments In various parts of the world, including Southeast and Southwest Alaska, a primary source of water is rainwater. Rainwater is collected from the roof of buildings with a device called a roof catchment.  Chapter 3 Introduction to Water Sources 71 FENCE SURFACE WATER DIVERSION DITCH LOCK CLAY OVERFLOW MAXIMUM WATER LEVEL STEPS PERFORATED PIPE TO STORAGE WATER BEARING GRAVEL WATER STOP SCREENED DRAIN VALVE & BOX Spring box DOWN SPOUT FROM ROOF SCREEN MANHOLE COVER MAXIMUM WATER LEVEL SCREENED DRAIN SCREEN TO PUMP Roof catchment Screens Bar Screens The intake pumps, valves, and piping need to be protected from debris that would normally be drawn into the intake. One of the primary protection devices are large steel or concrete bars set vertically in the flow. This is called a bar screen and is de- signed to protect against large material. 72 Chapter 3 Introduction to Water Sources Screens After the bar screens is usually a smaller screen, designed to remove leaves and other small material that can clog the pumps and valves. The screens can be either self- cleaning or manually cleaned. Manually cleaned screens often require daily cleaning during certain times of the year. SLUICE GATES SCREEN BAR SCREEN Pumps Gas Powered Units In many small villages that use the fill and draw process, a gas pow- ered, end-suction centrifugal, self- priming pump is used to remove the water from the stream, muskeg, or tundra pond. Lineshaft Turbines While not common in Alaska, one of the most common surface water intake pumps in other parts of the country is the lineshaft turbine. These are frequently used in larger facilities and are installed inside a protective caisson. This type of pump cannot be used as a portable device because it must remain in a perfectly plumb vertical posi- tion when it is in operation. Submersible Turbine The submersible turbine is used in a caisson on small streams and in river floats and set through the ice in the winter. The pump operates best and has the longest life if it can be kept in a nearly vertical plumb position when it is operating.  Chapter 3 Introduction to Water Sources 73 CHECK VALVE HOLLOW SHAFT MOTOR DISCHARGE HEAD ELECTRICAL STUFFING CONNECTION DROP PIPE BOX INLET SCREEN DRIVING SHAFT COLUMN BOWLS & IMPELLERS INLET SCREEN PUMP UNIT ELECTRIC MOTOR Lineshaft turbine Submersible turbine Review 1. The ______________ prevents an embankment dam from leaking. 2. What is the function of the bar screen at a surface water intake? 3. The two most common pumps found in small water system surface water and ground- water intakes are the ______________,______________ and the submersible. Safety Concerns Electrical Anytime you are working with electricity, there is a safety concern. A 200-milliamp shock from arm to arm is enough to kill an average person. This current is less than what would run through your body if shocked by 120 volts. To prevent shock, always wear insulated gloves, and never wear metal jewelry or metal eyeglass frames when working with electricity. Latch the panel door open when working inside the panel. Turn the power off when making repairs, and always STOP AND THINK TWICE BEFORE TOUCHING AN ELECTRICAL COMPONENT. Lock-Out When working on a pump, be sure to shut the power off, and “lock-out” the breaker with a padlock. Place a tag on the padlock with a note indicating when and why the unit was turned off.  74 Chapter 3 Introduction to Water Sources Noise When using gas or diesel powered equipment, you should be aware of the noise level. If the noise in the area in which you are working is above 85 db, you should wear hearing protection. Damaged hearing cannot normally be repaired. For instance, a gas-powered pump installed in a caisson or on a boat requires hearing protection any- time you are in or directly above the caisson when the pump is running. Confined Spaces Most caisson and valve boxes associated with intake structures are confined spaces and; therefore, require the following: A written permit before you enter The use of an air ventilation system Monitoring the air quality with an oxygen and combustible gas meter every 15 minutes Carbon Monoxide When running the gas-powered pump in a caisson, take special care to ensure that the exhaust is out of the caisson. However, the wind can easily blow carbon monoxide back into the caisson. Check for oxygen and combustible gases before entering the caisson. Records and Data Collection To properly operate and maintain a surface water system, you should keep the follow- ing records: As-built drawings of all facilities Copy of the water rights certificate Copy of the watershed management use agreement 19 Contamination – The introduction Map of drainage basin showing land ownership, potential or existing con- into water of toxic materials, bacteria, or other deleterious agents that make tamination19 sites, activity sites, and location of any water system structures the water unfit for its intended use. Baseline quality and quantity data Water quality survey reports Water monitoring reports Recommended Activities To properly operate and maintain a surface water system, you should routinely obtain the following data and/or perform the following tasks: (Note: The test frequency described below is for CWS or NTNCWS systems and depends on particular system and monitoring summary.) Test turbidity pH and temperature (Daily) If there is color in the water (Daily) Test for bacteriological quality (Monthly) Collect a sample and have it tested for inorganic contaminants (Yearly) Collect a sample and have it tested for organic contaminants (Yearly) Inspect the intake structure (Frequency depends on type of structure but at least weekly) Make an on-site investigation of the drainage basin and waterway looking for existing or potential contamination (Yearly). This contamination can be natural or man-made. This process is called a water quality survey. Collect stream flow and precipitation data (Weekly)  Chapter 3 Introduction to Water Sources 75 Groundwater Definition Groundwater is considered to be water that is below the earth’s crust, but not more than 2500 feet below the crust. Water between the earth’s crust and the 2500-foot level is considered usable fresh water. Examples of Groundwater Groundwater is obtained from the following: Wells Springs that are not influenced by surface water or a local hydrologic event Under the Influence When a well or spring is influenced by an adjacent surface water source or by a local hydrological event, the supply is said to be groundwater under the direct influence of surface water (GUDISW). Advantages and Disadvantages of Groundwater There are both advantages and disadvantages to groundwater. Advantages – The advantages of groundwater sources in relationship to surface water include the following: Groundwater is not as easily contaminated as surface water. The quality of groundwater, while not always as good as would be preferred, is stable throughout the year. Groundwater sources are generally lower in bacteriological count than sur- face water sources. Groundwater is available in most locations throughout the continental US and Alaska. Disadvantages – When comparing groundwater sources with surface water, the following are disadvantages to using groundwater: Once a groundwater source is contaminated, it is difficult for it to recover. There is no easy way to remove the contaminants. Groundwater usually contains more minerals than surface water, including increased levels of hardness. Because groundwater is in contact longer with minerals, there is more time to bring them into solution. Removal of groundwater normally requires a pump, thus increasing operation cost. Groundwater is more susceptible to long-term contamination from fuel spills. Groundwater supplies often have high levels of iron and manganese, thus increasing treatment cost and/or causing stains on plumbing and the clothing of customers. Wells in the coastal areas are subject to salt water intrusion into the aquifer20 20 Aquifer – A porous, water-bearing geologic formation from which surface and well. This contamination is difficult to predict and costly to treat. water is obtained. Sources of contamination can be hidden from sight.  76 Chapter 3 Introduction to Water Sources Groundwater Hydrology Source Groundwater, like surface water, is part of the hydrologic cycle. Groundwater is found in saturated layers under the earth’s surface called aquifers. There are different names given to aquifers, depending upon their type. Three Types of Aquifers There are three types of aquifers: unconfined, confined, and springs. The following is a brief description of the differences between these types of aquifers. Unconfined Aquifers Definition 21 Unconfined Aquifer – An aquifer that The zone of saturation is an unconfined aquifer21. It is not contained, except on the sits on an impervious layer but is open on the top to local infiltration. The bottom. An unconfined aquifer depends on local precipitation for recharge. This type recharge for an unconfined aquifer is of aquifer is often called a water table aquifer. local and is called a water table aquifer. Zones and Belts Unconfined aquifers are composed of unconsolidated strata that are divided into two zones: The zone of aeration contains two belts: the soil-water belt, where plants obtain their water, and the intermediate belt, where there is a mixture of air and water. The zone of saturation is an unconfined or water table aquifer. The top of this 22 Water Table – The average depth or zone of saturation is called the water table22. elevation of the groundwater over a selected area. The upper surface of the zone of saturation, except where that surface is formed by an impermeable body. SOIL- WATER BELT ZONE OF AERATION INTERMEDIATE BELT ZONE OF SATURATION IMPERMEABLE Unconfined Aquifer Wells Wells drilled in an unconfined aquifer are normally called shallow wells and are sub- ject to local contamination from hazardous and toxic material, such as fuel and oil, agricultural runoff containing nitrates and microorganisms, and septic tank discharge of increased levels of nitrates and microorganisms. Groundwater Under the Influence Water taken from wells drilled in an unconfined aquifer is not considered desirable as a public drinking water source. This type of well may be classified as groundwater under the direct influence of surface water (GUDISW) and therefore require treat- ment for control of microorganisms.  Chapter 3 Introduction to Water Sources 77 Confined Aquifers Definition At various locations in the earths crust are layers of saturated material that are con- tained between two layers of impermeable material such as rock, clay, or permafrost. This type of aquifer is called a confined aquifer23. 23 Confined Aquifer – An aquifer sur- rounded by formations of less perme- able or impermeable material. Artesian Aquifers Confined aquifers are also called artesian aquifers. Naturally a well drilled in an arte- sian aquifer is called an artesian well. An artesian well is described as any well where the water in the well casing rises above the saturated strata. There are two types of artesian wells: flowing and non-flowing. Water Quality – Confined Aquifers Confined aquifers commonly yield large quantities of high-quality water. One excep- tion is water confined by permafrost layers. This water is very poor quality. The aqui- fer may be relatively short or may extend several hundred miles into the mountains. Recharge of Confined Aquifers A confined aquifer is recharged by snow or rain in the mountains where it is close to the surface of the earth. Because the recharge area is away from the area of contami- nation, the possibility of contamination of a confined aquifer is very low. However, once contaminated, it may take hundreds of years before it recovers. Wells in Confined Aquifers A well in a confined aquifer is normally referred to as a deep well. If the well is prop- erly installed, the water quality is not impacted by local hydrological events. ANNUAL RECHARGE NATURAL SPRING UNCONFINED AQUIFER CONFINED AQUIFERS CONFINING LAYERS Springs Types Water that naturally exits on the crust of the earth is called a spring. The water in a spring can originate from a water table aquifer or from a confined aquifer. When a spring comes from a confined aquifer, it is commonly the result of a geological fault (a break in the confining layer). Only water from a confined aquifer spring is consid- ered desirable for a public water system.  78 Chapter 3 Introduction to Water Sources Water Movement Through an Aquifer Composition of an Aquifer An aquifer is made up of a combination of solid material, such as rock and gravel, and open spaces called pores. Regardless of the type of aquifer, the water in the aqui- fer is in motion. This motion is caused by gravity or by pumping. The flow of water through the aquifer is influenced by the size of the material, the number of pores, and the connection between the pores. Volume of Water The volume of water in an aquifer is dependent upon the amount of space available between the various grains of material that make up the aquifer. The amount of space 24 Porosity – The ratio of pore space available is called porosity24. to total volume. That portion of a cubic foot of soil that is air space and therefore can contain moisture. All grains approximately the same size. Mixed grain sizes. Interconnecting pores High Porosity Low Porosity High Porosity Ease of Movement Some material, such as clay, can hold a lot of water and has a high porosity, but the pores are not connected. It is therefore difficult for the water to move through the clay. The ease of movement through an aquifer is dependent upon how well the pores are connected. Below are three sections of different aquifers. The porosity of all three is the same. Section three (3) offers far less friction to the water and thus allows 25 Permeability – The property of a greater flow. The ability of an aquifer to pass water is called permeabillty25. material that permits appreciable movement of water through it when it is saturated and the movement is Low Permeability Medium Permeability High Permeability actuated by hydrostatic pressure of the magnitude normally encountered in natural subsurface water. Water Quality The most ideal public water system is one that offers high quality and high quantity. This is commonly an aquifer composed of a mixture of sand and gravel. This pro- vides adequate quantity and filters out unwanted material.  Chapter 3 Introduction to Water Sources 79 Cone of Depression Whenever a well is placed in a water-bearing stratum26 and pumped, water will flow 26 Stratum – A layer of the earth’s crust. toward the center of the well. In a water table aquifer, this movement causes the wa- 27 Cone of Depression – The de- ter table to sag toward the well. This sag is called the cone of depression27. pression, roughly conical in shape, produced in a water table or other Shape of the Cone piezometer surface by the extraction of water from a well at a given rate. The shape and size of the cone depends on the relationship between the pumping rate and the rate at which water can move toward the well. If the permeability is high, the cone will be shallow, and its growth will stabilize. If the permeability is low, the cone will be sharp and continue to grow in size. Zone of Influence The area that is included in the cone of depression is called the zone of influence. Any contamination in this zone will be drawn into the well. WELL HEAD SOIL WATER BELT AND WATER TABLE AQUIFER ZONE OF INFLUENCE CONFINING LAYER CONFINED AQUIFIER CONE OF DEPRESSION Static Water Level As a pump operates in a well, the depth of water will move up and down. If the pump were shut off for several hours and that water level allowed to recover and stabilize, the level would be called the static water level28. 28 Static Water Level – The water level in a well when the pump is not running. Drawdown When a well pump operates, the level of water in the well drops. The difference be- tween the static level and the level that a pump operates to is called the drawdown29. 29 Drawdown – The distance between the static level and the pumping level. Specific Yield The drawdown level depends on the pumping rate and the transmissibility of the aquifer. One standard test that is used to compare the performance of a well from year to year is to determine the specific yield of the well. This is done by pumping the well at a set rate for a specific period of time and measuring the drawdown. The flow is then divided by the drawdown to give a value in gpm/ft of drawdown. 80 Chapter 3 Introduction to Water Sources STATIC WATER LEVEL DRAWDOWN WATER LEVEL WHEN PUMP STOPS Well Location Criteria Regulations and Standards In order to protect the groundwater source and provide high quality safe water, the water works industry has developed standards and specifications for wells. In addi- tion, the Alaska Department of Environmental Conservation has established mini- mum construction criteria for municipal wells. The following listing details industry standard practices as well as those items included in the ADEC regulations: There can be no wastewater disposal systems, including septic tanks and drain fields, within 200 feet of the well for CWS, NTNCW, or TNCWS sys- tems and 150 feet for Class C systems. There should be no community sewer line, holding tanks, or other potential sources of contamination within 200 feet of the well in a CWS, NTNCW, or TNCWS system or within 100 feet of the well in a Class C system. Fuel not used for onsite emergency pumping equipment or heating cannot be stored within 100 feet of the well for a CWS, NTNCW, or TNCWS system or within 75 feet of the well for a Class C system. Fuel for onsite emergency generators or building heating system can be stored onsite if the total volume is less than 500 gallons.  Chapter 3 Introduction to Water Sources 81 The well casing must extend one foot above the ground. The top of the well casing must extend 12 inches above the well house slab. The ground around the well must be sloped away from the well 10 feet in all directions. The well must have a sanitary seal. The well casing must be grouted for at least 10 feet within the first 20 feet below the surface. The well head must be protected against flooding. Well pits are prohibited. Recommendations The following are recommendations and not regulations: To reduce the possibility of the well being classified as being under the influ- ence of surface water, it should not be located within 200 feet of a surface water source. The water purveyor should own or have a restricted area within 200 feet radius of the well. There should be no roads within 100 feet of the well. If the well is drilled within 100 feet of a road, the well must be protected against contamination from runoff from the road. To avoid the well being classified as GUDISW, you should review the deter- mination criteria and discuss the location with the ADEC. COMMUNITY SEWER LINE HOLDING TANK DRAINAGE FUEL FIELD SEPTIC TANK 200ft. 100ft. FUEL (less than 500 gal. WELL used for heat and emergency power only) 82 Chapter 3 Introduction to Water Sources Well Components Overview The components that make up a well system can be divided into three categories: the well itself, the building and the pump, and the related piping system. Well Casing A well is a hole in the ground called the bore hole. The hole is protected from col- lapsing by placing a casing inside the bore hole and securing the casing to the bore hole in a way that protects the aquifer from contamination. The most common casing material is steel. The casing should extend one foot above the ground and down into the impermeable layer above the aquifer. SOUNDING TUBE 12" Minimum 10 Ft Minimum 6" CONCRETE TOP SOIL WATER TABLE WATER BEARING SAND CEMENT GROUT 10 ft in first 20 ft CASING WATER LEVEL CLAY WATER BEARING SAND DRIVE SHOE SCREEN  Chapter 3 Introduction to Water Sources 83 Grout To protect the aquifer from contamination, the casing is sealed to the bore hole near the surface and near the bottom where it passes into the impermeable layer. The Alaska Department of Environmental Conservation minimum is 10 feet of continuos grout within the first 20 feet of the well casing. Ground Seal The ground around the casing is sealed with a reinforced concrete slab. This concrete is usually connected to the grout that extends down the well. Pitless Adapter In some instances, it is desirable to have the discharge from the well exit below ground level. This reduces the possibility of freezing and allows more flexibility in the location of the pump house. The device that allows the line to pass through the casing wall is called a pitless adapter. The casing vent is an internal part of the pitless adapter cover. Grouting a Pitless Adapter Wells with pitless adapters are also required to be grouted at the top. This grouting should start just below the pitless adapter and extend down at least 10 feet. SANITARY WELL COVER (VENTED) PLUG LIFT-OUT DEVICE SUBMERSIBLE CABLE LOCKING DEVICE CONDUIT PITLESS ADAPTER DISCHARGE FITTING FROST LINE CHECK VALVE FLEXIBLE CONNECTION SNIFTER VALVE or GROUT AIR CHARGER Well Head The well head is merely the top of the well casing. Sanitary Seal SUBMERSIBLE To prevent contaminationPUMP of the well, a sanitary seal is placed at the top of the casing. The type of seal varies depending upon the type of pump being used. CEMENT GROUT 84 Chapter 3 Introduction to Water Sources Sanitary Seal – Submersible Pump For submersible turbines, the sanitary seal is typically composed of a rubber-like ma- terial placed between two pieces of metal. When bolts are tightened on the sanitary seal, the rubber is compressed and expands to seal against the casing and the pump discharge pipe. Drop Pipe – Riser The line leading from the pump to the well head is called a drop pipe or riser pipe. This pipe is either steel or PVC. Steel is the most desirable. Well Screen Screens can be installed on the end of a well casing or on the end of the inner casing on a gravel-packed well. These screens perform two functions: one is the support of the bore hole, and the second it to reduce the amount of sand that enters the casing and the pump. Casing Vent The well casing must have a vent. On a PIPE PLUG typical casing, this vent is a double 90° WELL VENT Ell that is pointed toward the ground. DISCHARGE LINE The opening of the vent should be screened with a #24 mesh stainless WIRE MESH steel screen. Sampling Tap POWER CABLE TO SUBMERSIBLE PUMP A sampling tap or valve should be SANITARY SEAL installed to allow for sampling raw water. This tap must be far enough DROP PIPE FROM SUBMERSIBLE PUMP from any chemical injection point so that the chemicals do not contaminate the sample. Master Meter A master meter should be installed on the discharge from the well. The meter is the only reliable means of determin- ing the production of the well. Check Valves On lineshaft turbines, there is commonly a check valve assembly on the discharge of the pump. The check valve prevents water from running back into the well. On small submersible pumps, there is usually a check valve at the top of the pump. On deep well submersibles, there may be additional check valves in the riser pipe. These check valves prevent water from running back through the pump and causing it to be turned in the opposite direction that could damage the pump. Air Vacuum Relief Valve An air vacuum relief valve is installed on the discharge line to reduce water hammer and prevent air in the column from being forced into the water. The casing is protect- ed from collapse by a double 90° vent with #24 mesh stainless steel screen.  Chapter 3 Introduction to Water Sources 85 AIR RELIEF VALVE MASTER CHECK SAMPLING METER VALVE TAP CASING VENT SOUNDING TUBE COLUMN WELL CASING Check Valves and Freezing In some cases, it may be desirable to allow a portion of the water to run back down the riser pipe on a submersible pump installation. This is accomplished by drilling a “weep hole” in the side of the pipe or in the disk of the check valve. This is done to remove water from the top of the drop pipe and thus reduce the possibility of freez- ing. Building Function of Building The building is designed to protect the pump and piping from freezing. Protection from freezing may require the installation of heat trace tape on the drop pipe. The building should also be designed to allow easy removal and replacement of the pump and pump motor. Electrical Equipment All electrical components should be protected from weather damage. Heat and Lights The building must be heated and contain proper lighting to allow for maintenance. Chlorine The chlorine and fluoride systems should not be in the same room with electric mo- tors and control panels. If they must be housed with the electrical system, all the electrical fixtures and motors must be corrosion-resistant. 86 Chapter 3 Introduction to Water Sources Pumps Two Types There are two types of pumps that are commonly installed in groundwater systems: Submersible Turbine Components – With the submersible turbine pumping installation, the pump motor is below the pump. The water intake is between the motor and the pump. The pump is a series of impellers called stages. Water moves from stage to stage up through the pump and into the riser pipe. Water exits the casing through the discharge head at the top of the well cas- ing. Electrical connections are made above the casing in an electrical box. As with other types of wells, there is a casing vent installed in the sanitary seal. Lineshaft Turbine Components – With the lineshaft turbine installation, only the pump is placed into the water. The pump is similar to the submers- ible pump. There are a series of impellers called stages or bowls. The water flows from stage to stage up through the pump and into the column and exits the well through the discharge head. The discharge head is mounted to the base plate and sealed with a rubber-like sanitary seal. The pump is driven by a drive shaft that extends from the pump to the motor. The drive shaft is supported by bearings approximately every 20 feet. These bearings can be lubricated with water or with food-grade oil. CHECK VALVE HOLLOW SHAFT MOTOR DISCHARGE HEAD STUFFING BOX INLET SCREEN DRIVING SHAFT COLUMN BOWLS & IMPELLERS PUMP UNIT ELECTRIC MOTOR Submersible Turbine Lineshaft Turbine  Chapter 3 Introduction to Water Sources 87 Data and Record-keeping Requirements Records A properly operated and managed water works facility keeps the following records concerning their well: Well log – Documentation of what materials were found in the bore hole and at what depth. The well log should include the depths at which water was found, the casing length and type, the depth and type of soils, testing proce- dure, well development techniques, and well production. Pump and motor name plate data, as well as maintenance history. Water quality data on the physical, chemical, and bacteriological testing results. Quantity of water pumped from the well. Static and drawdown water levels. Data Collection and Testing Treated water should be tested for the following at the stated intervals (type and frequency depends on particular system and monitoring summary.): Temperature (Daily) pH (Daily) Amount of water pumped (Daily) Pumping hours (Daily) Pump discharge pressure (Daily) Iron or manganese, if a problem (Daily) Conductivity (Weekly) Total coliform (Monthly) Gallons per minute that pump produces (Monthly) Raw water fluoride, if feeding fluoride (Quarterly) Depth of water in well (Quarterly) Motor amperage and voltage (Quarterly) Specific yield (Twice a year – winter and summer) Collect sample and have it tested for Nitrate (Annually) Collect sample and have it tested for inorganics (Every three years) Collect and sample for pesticides (Every three years) Collect sample and have it tested for radioactivity (Every four years) Collect sample and have it tested for VOCs (Every five years) Review 1. List two of the advantages of groundwater sources and two for surface water. 2. For each of the following items, give the proper separation from a well for a CWS, NT- NCW, or TNCWS system: Community sewer _______; Fuel oil, less than 500 gallons used for heating _______; Septic tank _______. 3. The well casing should extend _______ above the ground or well house floor. 4. A well casing should be grouted for at least _______ feet, within the first _______ feet.  88 Chapter 3 Introduction to Water Sources Transmission Lines Function Transmission lines are installed in order to move the water between the well or intake and the treatment plant or storage tank. A transmission line is used to transfer raw water only and should have no service connections. Transmission lines can serve as a chlorine contact chamber. Types Of Transmission Lines Piped The most popular type of transmission line is the buried pipe. These lines are com- monly DCIP or HDPE, although in the past, PVC, wood, and steel pipe have also been used. The City of Craig uses 12-inch DCIP from its surface water reservoir to its treatment plant seven miles away. Arctic Pipe In the arctic regions, a special piping material called arctic pipe is buried, or laid above ground in permafrost areas, instead of the standard piping material. Arctic pipe is composed of three components. The line that carries the water is called the carrier pipe and is commonly made of PVC or HDPE. HDPE is the most common in new installations. The carrier is protected with several inches of high-density polyurethane insulation and covered with a metal jacket. METAL JACKET CARRIER - PVC or HDPE HIGH DENSITY POLYURETHANE Above-Ground Utilidors Utilidors have been used in the arctic for a number of years. The older utilidors were made of insulated plywood. The newer installations are made of large-diameter arctic pipe, insulated with high-density polyurethane or polystyrene and covered with 16- and 12-gauge steel. The carrier pipe on new utilidors is PVC or HDPE. The above- 30 Glycol – Common name for pro- ground utilidors are commonly heated using a HDPE pipe loop of heated glycol30. pylene glycol, a colorless, thick, sweet liquid used as antifreeze. The glycol is heated with a low-pressure water boiler and circulated with a pump through the loop. Below-Ground Utilidors Due to cost, below-ground walk-through utilidors are not very common. They can be found in Barrow, Nome, and Fairbanks. The most common below-ground utilidors are made of wood or concrete insulated with a polystyrene foam. The water, sewer, and electrical utilities are placed on racks in the utilidors. Heat is provided by a gly- col heating loop or electric heaters.  Chapter 3 Introduction to Water Sources 89 12 Gauge steel top 16 Gauge steel 4 inch Polyurethane 12 inch PVC Vacuum sewer PVC Water Copper heat trace pipe Wood beam and supports Above ground utilidor Flow Meters Purpose A flow meter placed in the raw water line is the only method of tracking daily use, monthly average, and peak demands. These meters can also be useful in evaluating the amount of leakage in a water system. Types There are six types of meters used in raw water lines: propeller, turbine, magnetic, displacement, orifice, and venturi meters. Turbine and displacement meters are the most common in the small systems in Alaska. Turbine – On lines 3 to 12 inches in diameter, turbine meters are common and practical. These meters use a bypass technique to divert a portion of the flow through a turbine wheel. The turbine is connected via a magnet to the register. This type of meter is quite accurate over a wide flow range and of- fers low headloss to the flow. Displacement Meters – Displacement meters are used on pipes from 3/4 inch through four inch. They are the most accurate over a wide range of flows. There are two common types of displacement meters: the rotating piston and the nutating disc. In each case, the flow of water causes a device to move in a chamber with a fixed volume. As the device moves, it rotates. The rotating device is connected by a magnet to a register that records the flow. 90 Chapter 3 Introduction to Water Sources Turbine meter Displacement meter Groundwater Under Direct Influence of Surface Water Background When surface water can infiltrate a groundwater supply, there is a high possibil- ity that the groundwater may be contaminated with Giardia, viruses, turbidity, and organic material from the surface water source. As a result, the Surface Water Treat- ment Rule of the Safe Drinking Water Act requires that each state determine which groundwater supplies are influenced by surface water. When a groundwater supply is identified as being under the direct influence of surface water, it is no longer called a groundwater supply, but is referred to as groundwater under the direct influence of surface water (GUDISW). When a supply is designated as GUDISW, the State’s surface water rules apply to the source rather than the groundwater rules. Involvement of the ADEC It is the responsibility of the ADEC to identify and categorize all groundwater sup- plies into either groundwater or GUDISW. It is the responsibility of the utility to perform the analysis required for this determination. Evaluation Process To determine whether a groundwater supply is under the direct influence of surface water, the EPA has developed procedures that focus on significant and relatively rapid shifts in water quality characteristics such as turbidity, temperature, and pH. When these shifts can be closely correlated with rainfall, breakup, or other surface water conditions or when certain indicator organisms associated with surface water are found, the source is said to be under the direct influence of surface water. Procedure – More Details The procedure for springs, infiltration galleries, and wells includes the following steps: 1. Review of records to determine the method of well construction and wa- ter quality conditions, distance from well to nearby surface water, coliform contamination history, and history of known or suspected waterborne disease outbreaks associated with organisms normally found in surface water.  Chapter 3 Introduction to Water Sources 91 2. An on-site inspection to look for evidence that surface water can enter through defects with the well head, casing, or underground connections with the aquifer. 3. An analysis of the well water to identify organisms that normally occur in surface waters but are not normally found in groundwater sources. When Evaluation is not required Utilities are not required to perform extensive evaluations if the system meets the fol- lowing criteria: Well is deeper than 50 feet. Well is more than 200 feet from a surface water source. Well was constructed properly with screens or perforated intake below a confining layer. There is no history of significant shifts in water quality. There is no history of coliform contamination or waterborne disease out- breaks in the system. Importance of Organisms Although a significant and relatively rapid shift in groundwater quality can indicate the influence of surface water, it is the analysis for surface water organisms that determines whether the supply falls under the requirements of the SWTR. The intent of the analysis is to identify organisms that are likely to occur only in surface waters. The presence of such organisms in groundwater indicates that at least some surface water has been mixed with the groundwater. Sampling The sampling for surface water organisms generally involves filtering 100 to 500 gallons of water through a one micron cartridge filter over a 4 to 8 hour period. At least two samples must be collected during the time the source is most susceptible to surface water influence (during heavy rainfall or runoff). Review 1. What are the two most common arctic pipe carriers? 2. A spring and a shallow well are examples of what type of water source? 92 Chapter 3 Introduction to Water Sources Introduction to Water Sources Quiz 1. The primary advantages to using surface water as a water source include: A. Usually higher in turbidity B. Generally softer than groundwater C. Easily contaminated with microorganisms D. Can be variable in quality 2. Which source of water has the greatest natural protection from bacterial contami- nation? A. Shallow well B. Deep well C. Surface water D. Spring 3. A disadvantage of groundwater is that it is: A. Easily located B. Higher in turbidity C. Usually higher in minerals D. Not easily contaminated by microorganisms 4. What safety measure must an operator follow prior to working on electrical equipment? A. Lock out and tag out all electrical switches. B. Put on canvas gloves. C. Remove fuses from switch box. D. Tell one co-worker not to turn on the switch. 5. A weir should be used to measure water in which of the following locations? A. Above-ground storage tanks B. Household service lines C. Open channels D. Water mains 6. Infiltration galleries are more commonly used for: A. GUDISW systems B. Wells C. Streams or rivers D. Filters 7. Wells must not be located within _______ feet of a wastewater disposal system. A. 50 B. 100 C. 200 D. 500 8. In a(n) ____________ aquifer, groundwater is under pressure. A. Unconfined B. Open C. Closed D. Confined  Chapter 3 Introduction to Water Sources 93 9. The difference between the static level and the level that a pump operates to is called the: A. Operating level B. Suction head C. Well yield D. Drawdown 10. A well casing should extend at least _______ inches above the ground. A. 6 B. 8 C. 12 D. 24 11. The water level in a well after the pump has been shut down for a long period is called: A. Recovery level B. Drawdown level C. Shutdown head level D. Static level 12. If water is drawn out of a well, a _______________ will develop. A. Saturation zone B. Cone of depression C. Zone of influence D. Static head 13. The space between the inner or protective casing and the outer casing or drill hole should be filled with cement grout to a minimum of how many feet? A. 10 feet within the first 20 B. 15 feet within the first 25 C. 20 feet within the first 30 D. 35 feet within the first 45