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ARMY TM 5-813-1NAVY

AIR FORCE AFM 88 10, Vol. 1

WATER SUPPLYSOURCES AND GENERAL CONSIDERATIONS

DEPARTMENTS OF THE ARMY, THE NAVY, AND THE AIR FORCE4 JUNE 1987

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REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared by or for the Government and is public property and not subject to copyright.

Reprints or republications of this manual should include a credit substantially as follows: .Joint Departments of the Armyand Air Force USA, Technical Manual TM 5813-1/AFM 88-10, Volume 1, Water Supply, Sources and GeneraConsiderations, 4 June 1987.

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TECHNICAL MANUAL HEADQUARTERSNo. 5-813-1 DEPARTMENTS OF THE ARMYAIR FORCE MANUAL AND THE AIR FORCENo. 88-10, Volume 1 WASHINGTON, DC 4 June 1987

WATER SUPPLYSOURCES AND GENERAL CONSIDERATIONS

Paragraph Page Chapter 1. GENERAL

Purpose...................................................................................................................................... 1-1 1-1Scope......................................................................................................................................... 1-2 1-1Definitions .................................................................................................................................. 1-3 1-1

Chapter 2. WATER REQUIREMENTSDomestic requirements .............................................................................................................. 2-1 2-1Fire-flow requirements ............................................................................................................... 2-2 2-1Irrigation ..................................................................................................................................... 2-3 2-1

Chapter 3. CAPACITY OF WATER-SUPPLY SYSTEMCapacity factors ......................................................................................................................... 3-1 3-1Use of capacity factor ................................................................................................................ 3-2 3-1System design capacity ............................................................................................................. 3-3 3-1Special design capacity ............................................................................................................. 3-4 3-1Expansion of existing systems ................................................................................................... 3-5 3-1

Chapter 4. WATER SUPPLY SOURCESGeneral ...................................................................................................................................... 4-1 4-1Use of existing systems ............................................................................................................. 4-2 4-1Other water systems .................................................................................................................. 4-3 4-1Environmental considerations .................................................................................................... 4-4 4-1Water quality considerations ...................................................................................................... 4-5 4-1Checklist for existing sources of supply ..................................................................................... 4-6 4-2

Chapter 5. GROUND WATER SUPPLIESGeneral ...................................................................................................................................... 5-1 5-1Water availability evaluation ...................................................................................................... 5-2 5-1Types of wells ............................................................................................................................ 5-3 5-3Water quality evaluation............................................................................................................. 5-4 5-6Well hydraulics ........................................................................................................................... 5-5 5-6Well design and construction ..................................................................................................... 5-6 5-9Development and disinfection .................................................................................................... 5-7 5-19Renovation of existing wells ....................................................................................................... 5-8 5-20Abandonment of wells and test holes ........................................................................................ 5-9 5-20Checklist for design.................................................................................................................... 5-10 5-22

Chapter 6. SURFACE WATER SUPPLIESSurface water sources ............................................................................................................... 6-1 6-1Water laws ................................................................................................................................. 6-2 6-1Quality of surface waters............................................................................................................ 6-3 6-1Watershed control and surveillance ........................................................................................... 6-4 6-1Checklist for surface water investigations .................................................................................. 6-5 6-2

Chapter 7. INTAKESGeneral ...................................................................................................................................... 7-1 7-1Capacity and reliability ............................................................................................................... 7-2 7-1Ice problems .............................................................................................................................. 7-3 7-1Intake location ............................................................................................................................ 7-4 7-2

Chapter 8. RAW WATER PUMPING FACILITIESSurface water sources ............................................................................................................... 8-1 8-1Ground water sources................................................................................................................ 8-2 8-2Electric power............................................................................................................................. 8-3 8-2Control of pumping facilities ....................................................................................................... 8-4 8-2

Chapter 9. WATER SYSTEM DESIGN PROCEDUREGeneral ...................................................................................................................................... 9-1 9-1Selection of materials and equipment ........................................................................................ 9-2 9-1Energy conservation .................................................................................................................. 9-3 9-1

*This manual supersedes TM 5813-1/AFM 88-10, Chap. 1; and TM 5-813-2/AFM 88-10, Chap. 2, each dated July, 1965.

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Page

Appendix A. REFERENCES ..................................................................................................................... A-1Appendix B. SAMPLE WELL DESIGN...................................................................................................... B-1Appendix C. DRILLED WELLS ................................................................................................................. C-1

BIBLIOGRAPHY ................................................................................................................... Biblio 1Index.............................................................................................................................................................. INDEX 1

List of Figures

Figure Page5-1 Water availability evaluation ................................................................................................. 5-25-2 Driven well ............................................................................................................................ 5-45-3 Collector well ........................................................................................................................ 5-55-4 Diagram of water table well .................................................................................................. 5-75-5 Diagram of well in artesian aquifer ....................................................................................... 5-85-6 Diagrammatic section of gravel-packed well ........................................................................ 5-105-7 Well in rock formation ........................................................................................................... 5-115-8 Sealed well ........................................................................................................................... 5-21B-1 Plan of proposed site ............................................................................................................ B-1

List of Tables

Table Page2-1 Domestic Water Allowances for Army and Air Force Projects .............................................. 2-23-1 Capacity Factors ................................................................................................................... 3-14-1 Water Hardness Classification ............................................................................................. 4-25-1 Types of Wells ...................................................................................................................... 5-35-2 Minimum distances from pollution sources ........................................................................... 5-65-3 Well diameter vs. anticipated yield ...................................................................................... 5-95-4 Change in yield for variation in well diameter ....................................................................... 5-125-5 Characteristics of pumps used in water supply systems ...................................................... 5-17

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CHAPTER 1GENERAL

1-1. PurposeThis manual provides guidance for selecting watersources, in determining water requirements for Army andAir Force installations including special projects, and for

developing suitable sources of supply from ground orsurface sources.

1-2. ScopeThis manual is applicable in selection of all watersources and in planning or performing construction ofsupply systems. Other manuals in this series are:

TM 5-813-3/AFM 88-10, Vol. 3--Water TreatmentTM 5-813-4/AFM 88-10, Vol. 4- Water StorageTM 58135/AFM 88-10, Vol. 5--Water DistributionTM 5-813-6/AFM 88-10, Chap. 6-Water Supply for

Fire ProtectionTM 5813-7/AFM 88-10, Vol. 7-Water Supply for

Special Projects

TB MED-229-Sanitary Control and Surveillance ofWater Supplies at Fixed and FieldInstallations

AFR 161 11 Management of the Drinking WaterSurveillance Program

1-3. Definitionsa. General definitions. The following

definitions, relating to all water supplies, are established.(1) Water works. All construction

(structures, pipe, equipment) required for the collection,transportation, pumping, treatment, storage anddistribution of water.

(2) Supply works. Dams, impoundingreservoirs, intake structures, pumping stations, wells andall other construction required for the development of awater supply source.

(3) Supply line. The pipeline from thesupply source to the treatment works or distributionsystem.

(4) Treatment works. All basins, filters,buildings and equipment for the conditioning of water torender it acceptable for a specific use.

(5) Distribution system. A system opipes and appurtenances by which water is provided fordomestic and industrial use and firefighting.

(6) Feeder mains. The principal pipelines

of a distribution system.(7) Distribution mains. The pipelines thaconstitute the distribution system.

(8) Service line. The pipeline extendingfrom the distribution main to building served.

(9) Effective population. This includesresident military and civilian personnel and dependentsplus an allowance for nonresident personnel, derived asfollows: The design allowance for nonresidents is 50gal/person/day whereas that for residents is 150gal/person/day. Therefore, an "effective-population"value can be obtained by adding one-third of thepopulation figure for nonresidents to the figure forresidents.

Nonresident PopulationEffective Population =

3+ Resident Population

(10) Capacity factor. The multiplier whichis applied to the effective population figure to provide anallowance for reasonable population increase, variationsin water demand, uncertainties as to actual waterequirements, and for unusual peak demands whosemagnitude cannot be accurately estimated in advanceThe Capacity Factor varies inversely with the magnitudeof the population in the water service area.

(11) Design population. The population

figure obtained by multiplying the effective-populationfigure by the appropriate capacity factor.Design Population = [Effective Population]

x [Capacity Factor](12) Required daily demand. The tota

daily water requirement. Its value is obtained bymultiplying the design population by the appropriate percapita domestic water allowance and adding to thisquantity any special industrial, aircraft-wash, irrigationair-conditioning, or other demands. Other demandsinclude the amount necessary to replenish in 48 hoursthe storage required for fire protection and normal

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operation. Where the supply is from wells, the quantityavailable in 48 hours of continuous operation of the wellswill be used in calculating the total supply available forreplenishing storage and maintaining fire and domesticdemands and industrial requirements that cannot becurtailed.

(13) Peak domestic demand. For systemdesign purposes, the peak domestic demand isconsidered to be the greater of-

(a) Maximum day demand, i.e., 2.5times the required daily demand.

(b) The fire flow plus fifty percent ofthe required daily demand.

(14) Fire flow. The required number ofgal/min at a specified pressure at the site of the fire for aspecified period of time.

(15) Fire demand. The required rate offlow of water in gal/min during a specified fire period.Fire demand includes fire flow plus 50 percent of therequired daily demand and, in addition, any industrial orother demand that cannot be reduced during a fire

period. The residual pressure is specified for either thefire flow or essential industrial demand, whichever ishigher. Fire demand must include flow required forautomatic sprinkler and standpipe operation, as well asdirect hydrant flow demand, when the sprinklers areserved directly by the water supply system.

(16) Rated capacity. The rated capacity ofa supply line, intake structure, treatment plant orpumping unit is the amount of water which can bepassed through the unit when it is operating underdesign conditions.

(17) Cross connection. Two typesrecognized are:

(a) A direct cross connection is aphysical connection between a supervised, potable watersupply and an unsupervised supply of unknown quality.An example of a direct cross connection is a pipingsystem connecting a raw water supply, used for industrialfire fighting, to a municipal water system.

(b) An indirect cross connection isan arrangement whereby unsafe water, or other liquidmay be blown, siphoned or otherwise diverted into a safewater system. Such arrangements include unprotectedpotable water inlets in tanks, toilets, and lavatories thatcan be submerged in unsafe water or other liquid. Undeconditions of peak usage of potable water or potablewater shutoff for repairs, unsafe water or other liquid maybackflow directly or be back-siphoned through the inletinto the potable system. Indirect cross connections areoften termed "backflow connections" or "back-siphonageconnections." An example is a direct potable wateconnection to a sewage pump for intermittent use forflushing or priming. Cross connections for Air Forcefacilities are defined in AFM 8521, Operations andMaintenance of Cross Connections Control and BackflowPrevention Systems.

b. Ground water supply definitions. Themeanings of several terms used in relation to wells andground waters are as follows:

(1) Specific capacity. The specific

capacity of a well is its yield per foot of drawdown and iscommonly expressed as gallons per minute per foot ofdrawdown (gpm/ft).

(2) Vertical line shaft turbine pump. Avertical line shaft turbine pump is a centrifugal pumpusually having from 1 to 20 stages, used in wells. Thepump is located at or near the pumping level of water inthe well, but is driven by an electric motor or internacombustion engine on the ground surface. Power istransmitted from the motor to the pump by a verticadrive shaft.

(3) Submersible turbine pump. Asubmersible turbine pump is a centrifugal turbine pump

driven by an electric motor which can operate whensubmerged in water. The motor is usually locateddirectly below the pump intake in the same housing asthe pump. Electric cables run from the ground surfacedown to the electric motor.

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CHAPTER 2

WATER REQUIREMENTS

2-1. Domestic requirementsThe per-capita allowances, given in table 2-1, will beused in determining domestic water requirements.

These allowances do NOT include special purpose wateruses, such as industrial aircraft-wash, air-conditioning,irrigation or extra water demands at desert stations.

2-2. Fire-flow requirementsThe system must be capable of supplying the fire flowspecified plus any other demand that cannot be reducedduring the fire period at the required residual pressureand for the required duration. The requirements of eachsystem must be analyzed to determine whether thecapacity of the system is fixed by the domesticrequirements, by the fire demands, or by a combinationof both. Where fire-flow demands are relatively high, orrequired for long duration, and population and/or

industrial use is relatively low, the total required capacitywill be determined by the prevailing fire demand. Insome exceptional cases, this may warrant considerationof a special water system for fire purposes, separate, inpart or in whole, from the domestic system. However,such separate systems will be appropriate only underexceptional circumstances and, in general, are to beavoided.

2-3. IrrigationThe allowances indicated in table 2-1 include water forlimited watering or planted and grassed areas. However,these allowances do not include major lawn or other

irrigation uses. Lawn irrigation provisions for facilities,such as family quarters and temporary structures, in allregions will be limited to hose bibbs on the outside ofbuildings and risers for hose connections. Wheresubstantial irrigation is deemed necessary and water isavailable, underground sprinkler systems may beconsidered. In general, such systems should receiveconsideration only in arid or semiarid areas where rainfallis less than about 25 inches annually. For ArmyProjects, all proposed installations require specificauthorization from HQDA (DAEN-ECE-G), WASH, DC20314. For Air Force projects, refer to AFM 88 15 andAFM 8810, Vol. 4. Each project proposed must include

thorough justification, detailed plans of connection towater source, estimated cost and a statement as to theadequacy of the water supply to support the irrigation

system. The use of underground sprinkler systems wilbe limited as follows: Air Force Projects-Areas adjacento hospitals, chapels, clubs, headquarters andadministration buildings, and Army Projects-Areasadjacent to hospitals, chapels, clubs, headquarters andadministration buildings, athletic fields, parade groundsEM barracks, Boos, and other areas involving improvedvegetative plantings which require frequent irrigation tomaintain satisfactory growth.

a. Backflow prevention. Backflow preventiondevices, such as a vacuum breaker or an air gap, will beprovided for all irrigation systems connected to potablewater systems. Installation of backflow preventers will bein accordance with AFM 85-21, Operation and

Maintenance of Cross Connection Control and BackflowPrevention Systems (for Air Force facilities) and theNational Association of Plumbing-Heating-CoolingContractors (NAPHCC) "National Standard PlumbingCode," (see app. A for references). Single or multiplecheck valves are not acceptable backflow preventiondevices and will not be used. Direct cross connectionsbetween potable and nonpotable water systems will notbe permitted under any circumstances.

b. Use of treated wastewater. Effluent fromwastewater treatment plants can be used for irrigationwhen authorized. Only treated effluent having adetectable chlorine residual at the most remote

discharge point will be used. Where state or locaregulations require additional treatment for irrigationsuch requirement will be complied with. The effluenirrigation system must be physically separated from anydistribution systems carrying potable water. A detailedplan will be provided showing the location of the effluenirrigation system in relation to the potable watedistribution system and buildings. Provision will be madeeither for locking the sprinkler irrigation control valves oremoving the valve handles so that only authorizedpersonnel can operate the system. In

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addition, readily identifiable "nonpotable" or"contaminated" notices, markings or codings for allwastewater conveyance facilities and appurtenances willbe provided. Another possibility for reuse of treatedeffluent is for industrial operations where substantialvolumes of water for washing or cooling purposes arerequired. For any reuse situation, great care must beexercised to avoid direct cross connections between thereclaimed water system and the potable water system.c. Review of effluent irrigation projects. Concept plansfor proposed irrigation projects using wastewatertreatment plant effluent will be reviewed by the engineerand surgeon at Installation Command level and the AirForce Major Command, as appropriate. EM 1110-1-501will serve as the basic criteria for such projects, asamended by requirements herein. This publication isavailable through HQ USACE publications channels (seeapp. A, References). Such projects will only beauthorized after approval by HQDA (DAEN-ECE-G),WASH DC 20314 and HQDA (DASG-PSP-E), WASHDC 20310 for Army projects and by HQUSAF (HQ

USAF/LEEEU), WASH DC 20332 and The SurgeonGeneral, (HQ AFMSC/SGPA), Brooks AFB, TX 78235for Air Force projects.

Table 2-1. Domestic Water Allowances for Army and AirForce Projects.

1

Gallons/Capita/Day2

Permanent Field TrainingConstruction Camps

USAF Bases and Air ForceStations 150

3-

Armored/Mech. Divisions 150 75Camps and Forts 150

450

POW and InternmentCamps - 50

4

Hospital Units5

600/Bed 400/BedHotel

670 -

Depot, Industrial, Plant 50 gal/employee/8-hr shift;and Similar Projects 150 gal/capita/day for

resident personnelNotes:1For Aircraft Control and Warning Stations, Nationa

Guard Stations, Guided Missile Stations, and similaprojects, use TM 5-813-7/AFM 88-10, Volume 7 fowater supply for special projects.2The allowances given in this table include water used

for laundries to serve resident personnel, washingvehicles, limited watering of planted and grassed areasand similar uses. The allowances tabulated do NOTinclude special industrial or irrigation uses. The pecapita allowance for nonresidents will be one-third thaallowed for residents.3An allowance of 150 gal/capita/day will also be used

for USAF semi-permanent construction.4For populations under 300, 50 gal/capita/day will be

used for base camps and 25 gal/capita/day for branchcamps.5Includes hotels and similar facilities converted to

hospital use.6Includes similar facilities converted for troop housing.

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CHAPTER 3

CAPACITY OF WATER-SUPPLY SYSTEM

3-1. Capacity factorsCapacity factors, as a function of "Effective Population,"are shown in table 3-1, as follows:

Table 3-1. Capacity Factors.Effective Population Capacity Factor

5,000 or less 1.5010,000 1.2520,000 1.1530,000 1.1040,000 1.05

50,000 or more 1.00

3-2. Use of capacity factorThe "Capacity Factor" will be used in planning watersupplies for all projects, including general hospitals. Theproper "Capacity Factor" as given in table 3-1 is

multiplied by the "Effective Population" to obtain the"Design Population." Arithmetic interpolation should beused to determine the appropriate Capacity Factor forintermediate project population. (For example, for an"Effective Population" of 7,200 in interpolation, obtain a"Capacity Factor" of 1.39.) Capacity factors will beapplied in determining the required capacity of the supplyworks, supply lines, treatment works, principal feedermains and storage reservoirs. Capacity factors will NOTbe used for hotels and similar structures that areacquired or rented for hospital and troop housing.Capacity factors will NOT be applied to fire flows,irrigation requirements, or industrial demands.

3-3. System design capacityThe design of elements of the water supply systemexcept as noted in paragraph 32, should be based on the

"Design Population."

3-4. Special design capacityWhere special demands for water exist, such as thoseresulting from unusual fire fighting requirementsirrigation, industrial processes and cooling water usageconsideration must be given to these special demands indetermining the design capacity of the water supplysystem.

3-5. Expansion of existing systemsFew, if any, entirely new water supply systems will beconstructed. Generally, the project will involve upgradingand/or expansion of existing systems. Where existingsystems are adequate to supply existing demands, plusthe expansion proposed without inclusion of the CapacityFactor, no additional facilities will be provided excepnecessary extension of water mains. In designing mainextensions, consideration will be given to planned futuredevelopment in adjoining areas so that mains will beproperly sized to serve the planned developmentsWhere existing facilities are inadequate for currenrequirements and new construction is necessary, theCapacity Factor will be applied to the proposed totaEffective Population and the expanded facilities plannedaccordingly.

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CHAPTER 4

WATER SUPPLY SOURCES

4-1. GeneralWater supplies may be obtained from surface or groundsources, by expansion of existing systems, or by

purchase from other systems. The selection of a sourceof supply will be based on water availability, adequacy,quality, cost of development and operation and theexpected life of the project to be served. In general, allalternative sources of supply should be evaluated to theextent necessary to provide a valid assessment of theirvalue for a specific installation. Alternative sources ofsupply include purchase of water from U.S. Governmentowned or other public or private systems, as well asconsideration of development or expansion ofindependent ground and surface sources. Acombination of surface and ground water, while notgenerally employed, may be advantageous under somecircumstances and should receive consideration.

Economic, as well as physical, factor must be evaluated.The final selection of the water source will be determinedby feasibility studies, considering all engineering,economic, energy and environmental factors.

4-2. Use of existing systemsMost water supply projects for military installationsinvolve expansion or upgrading of existing supply worksrather than development of new sources. If there is anexisting water supply under the jurisdiction of theDepartment of the Army, Air Force, or other U.S.Government agency, thorough investigation will be madeto determine its capacity and reliability and the possible

arrangements that might be made for its use with orwithout enlargement. The economics of utilizing theexisting supply should be compared with the economicsof reasonable alternatives. If the amount of water takenfrom an existing source is to be increased, the ability ofthe existing source to supply estimated waterrequirements during drought periods must be fullyaddressed. Also, potential changes in the quality of theraw water due to the increased rate of withdrawal mustreceive consideration.

4-3. Other water systemsIf the installation is located near a municipality or othepublic or private agency operating a water supply

system, this system should be investigated to determineits ability to provide reliable water service to theinstallation at reasonable cost. The investigation musconsider future as well as current needs of the existingsystem and, in addition, the impact of the military projecton the water supply requirements in the existing waterservice area. Among the important matters that must beconsidered are: quality of the supply; adequacy of thesupply during severe droughts; reliability and adequacyof raw water pumping and transmission facilitiestreatment plant and equipment; high service pumpingstorage and distribution facilities; facilities fotransmission from the existing supply system to themilitary project; and costs. In situations where a long

supply line is required between the existing supply andthe installation, a study will be made of the economicsize of the pipeline, taking into consideration cost ofconstruction, useful life, cost of operation, and minimumuse of materials. With a single supply line, the on-sitewater storage must be adequate to support the missionrequirement of the installation for its emergency periodA further requirement is an assessment of the adequacyof management, operation, and maintenance of thepublic water supply system.

4-4. Environmental considerationFor information on environmental policies, objectives

and guidelines refer to AR 200-1, for Army Projects andAFRs 19-1 and 19-2 for Air Force Projects.

4-5. Water quality considerationsGuidelines for determining the adequacy of a potentiaraw water supply for producing an acceptable finishedwater supply with conventional treatment practices aregiven in paragraph A-2 of TM 5-813-3/AFM 88-10, Vol3.

a. Hardness . The hardness of water suppliesis classified as shown in table 4-1.

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Table 4-1. Water Hardness Classification.

Total Hardness Classification mg/1 as CaCO3

0-100 Very Soft to Soft100-200 Soft to Moderately Hard200-300 Hard to Very Hard

over 300 Extremely Hard

Softening is generally considered when the hardnessexceeds about 200 to 250 mg/1. While hardness can bereduced by softening treatment, this may significantlyincrease the sodium content of the water, where zeolitesoftening is employed, as well as the cost of treatment.

b. Total dissolved solids (TDS). In addition tohardness, the quality of ground water may be judged onthe basis of dissolved mineral solids. In general,dissolved solids should not exceed 500 mg/1, with 1,000mg/1 as the approximate upper limit.

c. Chloride and sulfate. Sulfate and chloridecannot be removed by conventional treatment processes

and their presence in concentrations greater than about250 mg/1 reduces the value of the supply for domesticand industrial use and may justify its rejection ifdevelopment of an alternative source of better quality isfeasible. Saline water conversion systems, such aselectrodialysis or reverse osmosis, are required forremoval of excessive chloride or sulfate and also certainother dissolved substances, including sodium andnitrate.

d. Other constituents. The presence of certaintoxic heavy metals, fluoride, pesticides, and radioactivityin concentrations exceeding U.S. EnvironmentalProtection Agency standards, as interpreted by the

Surgeon General of the Army/Air Force, will makerejection of the supply mandatory unless unusuallysophisticated treatment is provided. (For detaileddiscussion of EPA water standards, see 40 CFR-Part141, AR 420-46 and TB MED 229 for Army Projects andAFR 161-44 for Air Force Projects.)

e. Water quality data. Base water qualityinvestigations or analysis of available data at or near theproposed point of diversion should include biological,bacteriological, physical, chemical, and radiologicalparameters covering several years and reflectingseasonal variations. Sources of water quality data areinstallation records, U.S. Geological Survey District orRegional offices and Water Quality Laboratories, U.S.Environmental Protection Agency regional offices, stategeological surveys, state water resources agencies, stateand local health departments, and nearby water utilities,including those serving power and industrial plants,

which utilize the proposed source. Careful study ohistorical water quality data is usually more productivethan attempting to assess quality from analysis of a fewsamples, especially on streams. Only if a thoroughsearch fails to locate existing, reliable water quality datashould a sampling program be initiated. If such aprogram is required, the advice and assistance of anappropriate state water agency will be obtained. Speciaprecautions are required to obtain representativesamples and reliable analytical results. Great cautionmust be exercised in interpreting any results obtainedfrom analysis of relatively few samples.

4-6. Checklist for existing sources of supplyThe following items, as well as others, if circumstanceswarrant, will be covered in the investigation of existingsources of supply from Government-owned or othersources.

a. Quality history of the supply; estimates ofuture quality.

b. Description of source.

c. Water rights.d. Reliability of supply.e. Quantity now developed.f. Ultimate quantity available.g. Excess supply not already allocated.h. Raw water pumping and transmission

facilities.I. Treatment works.

j. Treated water storage.k. High service pumping and transmission

facilities.l l. Rates in gal/min at which supply is available

m. Current and estimated future cost per 1,000

gallons.n. Current and estimated future cost per 1,000gallons of water from alternative sources.

o. Distance from military installation site toexisting supply.

p. Pressure variations at point of diversion fromexisting system.

q. Ground elevations at points of diversion anduse.

r. Energy requirements for proposed system.s. Sources of pollution, existing and potential.t. Assessment of adequacy of management

operation, and maintenance.u. Modifications required to meet additiona

water demands resulting from supplying water to militaryinstallation.

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CHAPTER 5

GROUND WATER SUPPLIES

5-1. GeneralGround water is subsurface water occupying thesaturation zone. A water bearing geologic formation

which is composed of permeable rock, gravel, sand,earth, etc., is called an aquifer. Unconfined groundwater is found in aquifers above the first impervious layerof soil or rock. Confined water is found in aquifers inwhich the water is confined by an overlying imperviousbed. Porous materials such as unconsolidatedformations of loose sand and gravel may yield largequantities of water and, therefore, are the primary targetfor location of wells. Dense rocks such as granite frompoor aquifers and wells constructed in them do not yieldlarge quantities of water. However, wells placed infractured rock formations may yield sufficient water formany purposes.

a. Economy . The economy of ground water

versus surface water supplies needs to be carefullyexamined. The study should include an appraisal ofoperating and maintenance costs as well as capitalcosts. No absolute rules can be given for choosingbetween ground and surface water sources. Wherewater requirements are within the capacity of an aquifer,ground water is nearly always more economical thansurface water. The available yield of an aquifer dictatesthe number of wells required and thus the capital costs ofwell construction. System operating and maintenancecosts will depend upon the number of wells. In general,ground water capital costs include the wells, disinfection,

pumping and storage with a minimum of other treatmentSurface water supply costs include intake structuressedimentation, filtration, disinfection, pumping and

storage. Annual operating costs include the costs ochemicals for treatment, power supply, utilities andmaintenance. Each situation must be examined on itsmerits with due consideration for all factors involved.

b. Coordination with State and LocaAuthorities. Some States require that a representative othe state witness the grouting of the casing and collectan uncontaminated biological sample before the well isused as a public water supply. Some States require apermit to withdraw water from the well and limit theamount of water that can be withdrawn.

c. Artic well considerations. Construction owells in artic and subartic areas requires speciaconsiderations. The water must be protected from

freezing and the permafrost must be maintained in afrozen state. The special details and methods describedin TM 5-852-5/AFM 88-19, Chap. 5 should be followed.

5-2. Water availability evaluationAfter water demand and water use have beendetermined, the evaluation of water availability and watequality of ground water resources will be made. Thefollowing chart is used to illustrate step-by-stepprocedures.

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Figure 5-1. Water availability evaluation.

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5-3. Types of WellsWells are constructed by a variety of methods. There isno single optimum method; the choice depends on size,depth, formations encountered and experience of localwell contractors. The most common types of wells arecompared in table 5-1.

Table 5-1. Types of Wells.

Maximum Lining or Method ofType Diameter Depth (ft) Casing Suitability Disadvantages Construction

Dug 3 to 20 40 wood, ma- Water near sur- Large number of Excavation fromfeet sonry, con- face. May be con- manhours required within well.

crete or structed with for construction.metal hand tools. Hazard to diggers.

Driven 2 to 4 50 pipe Simple using Formations must be Hammering a pipeinches hand tools. soft and boulder into the ground.

free.

Jetted 3 or 4 200 pipe Small dia. wells Only possible in High pressureinches on sand. loose sand forma- water pumped

tions. through drill pipe.

Bored up to 36 50 pipe Useful in clay Difficult on loose Rotating earth au-inches formations. sand or cobbles. ger bracket.

Collector 15 feet 130 Reinforced Used adjacent to Limited number of Caisson is sunkconcrete surface recharge Installation Con- into aquifer. Pre-caisson source such as tractors formed radial

river, lake or pipes are jackedocean. horizontally

through portsnear bottom.

Drilled Up to 60 4000 pipe Suitable for vari- Requires experi- a. Hydraulic ro-

inches ety of forma- enced Contractor & tary*tions. specialized tools. b. Cable tool per-

cussion*c. reverse circula-

tion rotaryd. hydraulic-per-

cussione. air rotary

*For detailed description, see Appendix C.

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Figure 5-2. Driven well.

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Figure 5-3. Collector well.

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5-4. Water quality evaluationBoth well location and construction are of majorimportance in protecting the quality of water derived froma well.

a. Sanitary survey . Prior to a decision as towell or well field location, a thorough sanitary survey ofthe area should be undertaken. The followinginformation should be obtained and analyzed:

(1) Locations and characteristics ofsewage and industrial waste disposal.

(2) Locations of sewers, septic tanks andcesspools.

(3) Chemical and bacteriological quality ofground water, especially the quality of water fromexisting wells.

(4) Histories of water, oil, or gas wells ortest holes in area.

(5) Industrial and municipal landfills anddumps.

(6) Direction and rate of travel of usableground water.

Recommended minimum distances for well sites, underfavorable geological conditions, from commonlyencountered potential sources of pollution are as shownin table 5-2. It is emphasized that these are minimumdistances which can serve as rough guides to goodpractice when geological conditions are favorable.Conditions are considered favorable when the earthmaterials between the well location and the pollutionsource have the filtering ability of fine sand. Where theterrain consists of coarse gravel, limestone ordisintegrated rock near the surface, the distance guidesgiven above are insufficient and greater distances will berequired to provide safety. Because of the wide

geological variations that may be encountered, it isimpossible to specify the distance needed under allcircumstances. Consultation with local authorities will aidin establishing safe distances consistent with the terrain.

Table 5-2. Minimum Distances from Pollution Sources.

MinimumSource Horizontal Distance

Building Sewer 50 ft.Septic Tank 50 ft.Disposal Field 100 ft.Seepage Pit 100 ft.Dry Well 50 ft.Cesspool 150 ft.

Note: The above horizontal distances apply to all depths ofwells.

b. Sampling and analysis. It is mandatory toreview the stipulations contained in the current U.SEnvironmental Protection Agencys drinking watestandards and state/local regulations as interpreted bythe Surgeon General of the Army/Air Force and to collecsamples as required for the determination of alconstituents named in the drinking water standards. Themaximum chemical concentrations mandated in thedrinking water standards are given in TM 5-813-3/AFM88-10, Vol. 3.

Heavy metals are rarely encountered in significanconcentrations in natural ground waters, but may be aconcern in metamorphic rock areas, along with arsenicRadioactive minerals may cause occasional highreadings in granite wells.

c. Treatment . Well water generally requiresless treatment than water obtained from surfacesupplies. This is because the water has been filtered bythe formation through which it passes before being takenup in the well. Normally, sedimentation and filtration arenot required. However, softening, iron removal, pH

adjustment and disinfection by chlorination are usuallyrequired. Chlorination is needed to provide residuachloride in the distribution system. The extent otreatment must be based upon the results of thesampling program. For a detailed discussion otreatment methods, see TM 5813-3/AFM 88-10, Vol. 3and Water Treatment Plant Design.

5-5. Well hydraulicsa. Definitions . The following definitions are

necessary to an understanding of well hydraulics:-Static Water Level. The distance from the ground

surface to the water level in a well when no water is

being pumped.-Pumping Level. The distance from the groundsurface to the water level in a well when water is beingpumped. Also called dynamic water level.

-Drawdown. The difference between static watelevel and dynamic water level.

-Cone of Depression. The funnel shape of thewater surface or piezometric level which is formed aswater is withdrawn from the well.

-Radius of Influence. The distance from the well tothe edge of the cone of depression.

-Permeability. The rate of flow through a squarefoot of the cross section of the aquifer under a hydraulicgradient of 100 percent at a water temperature of 60F.

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(The correction to 60F is usually neglected.) Usuallymeasured in gallons per day per square foot.

b. Well discharge formulas. The followingformulas assume certain simplifying conditions.However, these assumptions do not severely limit theuse of the formulas. The aquifer is of constantthickness, is not stratified and is of uniform permeability.The piezometric surface is level, laminar flow exists andthe cone of depression has reached equilibrium. Thepumping well reaches the bottom of the aquifer and is100 percent efficient. There are two basic formulas(Ground Water & Wells) one for water table wells andone for artesian wells. Figure 5-4 shows the relationshipof the terms used in the following formula for availableyield from a water table well:

Where:Q = well yield in gpmP = permeability in gpd per square footH = thickness of aquifer in feeth = depth of water in well while pumping

in feetR = radius of influence in feetr = radius of well in feet

Figure 5-5 shows the relationship of the terms used inthe following formula for available yield from an artesianwell:

where:m = thickness of aquifer in feetH = static head at bottom of aquifer in feetall other terms are the same as for Equation 5-1.

Figure 5-4. Diagram of water table well.

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Figure 5-5. Diagram of well in artesian aquifer.

c. Determination of values. The well drillerslog provides the dimensions of H and h. The value of Rusually lies between 100 and 10,000. It may bedetermined from observation wells or estimated. A valueof R = 1000 may be used; large variations makes smalldifference in the flow. P may be determined fromlaboratory tests or field tests. Existing wells or test wellsmay provide the values for all of these equations. Figure5-4 also shows the relationship of the terms used in theformula for calculating P:

For artesian conditions, again, as shown in fig. 5-5, theformula becomes:

d. Aquifer testing . Where existing wells orother data are insufficient to determine aquifercharacteristics, testing may be necessary to establish

values used for design. Testing consists of pumpingfrom one well and noting the change in watertable atother wells as indicated in figures 5-4 and 5-5Observation wells are generally set at 50 to 500 feet froma pumped well, although for artesian aquifers they maybe placed at distances up to 1000 feet. A greatenumber of wells allows the slope of the drawdown curveto be more accurately determined. The three moscommon methods of testing are:

-Drawdown Method. Involves pumping one weand observing what happens in observation wells.

-Recovery Method. Involves shutting down of apumped well and noting recovery of water level inobservation wells.

-Water Input Test. Involves running water into awell and determining the rate at which water flows intothe aquifer.The typical test, utilizing the drawdown method, consistsof pumping a well at various rates and noting thecorresponding drawdown at each step.

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e. Testing objectives. A simplified example isgiven in appendix B. When conducting tests by methodssuch as the drawdown method, it is important to noteaccurately the yield and corresponding drawdown. Agood testing program, conducted by an experiencedgeologists, will account for, or help to define, thefollowing aquifer characteristics:

(1) Type of aquifer-water table-confined-artesian

(2) Slope of aquifer(3) Direction of flow(4) Boundary effects(5) Influence of recharge

-stream or river-lake

(6) Nonhomogeneity(7) Leaks from aquifer

5-6. Well design and construction

Well design methods and construction techniques arebasically the same for wells constructed in consolidatedor unconsolidated formations. Typically, wellsconstructed in an unconsolidated formation require ascreen to line the lower portion of the borehole. Anartificial gravel pack may or may not be required. Adiagrammatic section of a gravel packed well is shownon figure 5-6. Wells constructed in sandstone, limestoneor other creviced rock formations can utilize an uncased

borehole in the aquifer. Screens and the gravel pack arenot usually required. A well in rock formation is shown infigure 5-7. Additional well designs for consolidated andunconsolidated formations are shown in AWWA A100.

a. Diameter . The diameter of a well has asignificant effect on the wells construction cost. Thediameter need not be uniform from top to bottomConstruction may be initiated with a certain size casingbut drilling conditions may make it desirable to reducethe casing size at some depth. However, the diametemust be large enough to accommodate the pump andthe diameter of the intake section must be consistentwith hydraulic efficiency. The well shall be designed tobe straight and plump. The factors that control diameteare (1) yield of the well, (2) intake entrance velocity, (3)pump size and (4) construction method. The pump sizewhich is related to yield, usually dominates. Approximatewell diameters for various yields are shown in table 5-3Well diameter affects well yield but not to a majodegree. Doubling the diameter of the well will produceonly about 10-15 percent more water. Table 5-4 gives

the theoretical change in yield that results from changingfrom one well diameter to a new well diameter. Foartesian wells, the yield increase resulting from diametedoubling is generally less than 10 percentConsideration should be given to future expansion andinstallation of a larger pump. This may be likely in caseswhere the capacity of the aquifer is greater than the yieldrequired.

Table 5-3. Well Diameter vs. Anticipated Yield.

Anticipated Nominal Size of Optimum Size Smallest Size Well Yield Pump Bowls Well Casing Well Casing

(gallons/minute) (inches) (inches) (inches)

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Figure 5-6. Diagrammatic section of a gravel-packed well.

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Figure 5-7. Well in rock formation.

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Table 5-4. Change in Yield for Variation in WellDiameter.

Original New Well DiameterWell

Diameter 6" 12" 18" 24" 30" 36" 48"6" 100% 110% 117% 122% 127% 131% 137%

12" 90 100 106 111 116 119 125

18" 84 93 100 104 108 112 11724" 79 88 95 100 104 107 11230" 76 85 91 96 100 103 10836" 73 82 88 92 96 100 10548" 69 77 82 87 91 94 100

Note: The above gives the theoretical increase ordecrease in yield that results from changingthe original well diameter to the new welldiameter. For example, if a 12-inch well isenlarged to a 36-inch well, the yield will beincreased by 19 percent. The values in theabove table are valid only for wells inunconfined aquifers (water table wells) and

are based on the following equation:(Y2/Y1) = (log R/r1)/(log R/r2)

where:Y2 = yield of new wellY1 = yield of original wellR = radius of cone of depression,

in feet (the value of R used forthis table is 400 feet).

r2 = diameter of new well, in feetr1 = diameter of original well, in feet

b. Depth . Depth of a well is usually determinedfrom the logs of test holes or from logs of other nearbywells that utilize the same aquifer. The deeper the well is

driven into a water bearing stratum, the greater thedischarge for a given drawdown. Where the waterbearing formations are thick, there is a tendency to limitthe depth of wells due to the cost. This cost, however,usually is balanced by the savings in operations resultingfrom the decreased drawdown. Construction should sealoff water bearing formations that are or may be pollutedor of poor mineral quality. A sealed, grouted casing willextend to a depth of 20 feet or more from the groundsurface. Check local regulations to determine minimumrequirements. Where the depth of water of poor qualityis known, terminate the well above the zone of poorquality water.

c. Casing . In a well developed in a sand andgravel formation, the casing should extend to a minimumof 5 feet below the lowest estimated pumping level. Inconsolidated formations, the casing should be driven 5feet into bedrock and cemented in place for its full depth.

The minimum wall thickness for steel pipe used forcasing is V/4-inch. For various diameters, EPArecommends the following wall thicknesses:

Nominal Diameter (inch) Wall Thickness (inch)6 .2508 .250

10 .27912 .33014 .37516 .37518 .37520 .375

In the percussion method of drilling, and where sloughingis a problem, it is customary to drill and drive the casingto the lower extremity of the aquifer to be screened andthen install the appropriate size screen inside the casingbefore pulling the casing back and exposing the screento the water bearing formation.

d. Screens . Wells completed in sand and

gravel with open-end casings, not equipped with ascreen on the bottom, usually have limited capacity dueto the small intake area (open end of casing pipe) andtend to pump large amounts of sand. A well designedscreen permits utilizing the permeability of the waterbearing materials around the screen. For a welcompleted in a sand-gravel formation, use of a welscreen will usually provide much more water than if theinstallation is left open-ended. The screen functions torestrain sand and gravel from entering the well, whichwould diminish yield, damage pumping equipment, anddeteriorate the quality of the water produced. Wellsdeveloped in hard rock areas do not need screens if the

wall is sufficiently stable and sand pumping is not aproblem.(1) Aperture size. The well screen

aperture opening, called slot size, is selected based onsieve analysis data of the aquifer material for a naturallydeveloped well. For a homogeneous formation, the slosize is selected as one that will retain 40 to 50 percent othe sand. Use 40 percent where the water is noparticularly corrosive and a reliable sample is obtainedUse 50 percent where water is very corrosive and/or thesample may be questionable. Where a formation to bescreened has layers of differing grain sizes andgraduations, multiple screen slot sizes may be usedWhere fine sand overlies a coarser material, extend the

fine slot size at least 3 feet into the coarser materialThis reduces the possibility that slumping of the lowematerial will allow finer sand to enter the coarse screen.

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The coarse aperture size should not be greater thantwice the fine size. For a gravel packed well, the screenshould retain 85 to 100 percent of the gravel. Screenaperture size should be determined by a laboratoryexperienced in this work, based on a sieve analysis ofthe material to be screened. Consult manufacturersliterature for current data on screens.

(2) Length. Screen length depends onaquifer characteristics, aquifer thickness, and availabledrawdown. For a homogeneous, confined, artesianaquifer, 70 to 80 percent of the aquifer should bescreened and the maximum drawdown should notexceed the distance from the static water level to the topof the aquifer. For a nonhomogeneous, artesian aquifer,it is usually best to screen the most permeable strata.Determinations of permeability are conducted in thelaboratory on representative samples of the variousstrata. Homogeneous, unconfined (water-table) aquifersare commonly equipped with screen covering the lowerone-third to one-half of the aquifer. A water-table well isusually operated so that the pumping water level is

slightly above the top of the screen. For a screen lengthof one-third the aquifer depth, the permissible draw-downwill be nearly two-thirds of the maximum possibledrawdown. This drawdown corresponds to nearly 90percent of the maximum yield. Screens fornonhomogeneous water-table aquifers are positioned inthe lower portions of the most permeable strata in orderto permit maximum available drawdown. The followingequation is used to determine screen length:

where:L = length of screen (feet)

Q = discharge (gpm)A = effective open area per foot of screen

length (sq. ft. per ft.) (approximately one-half of theactual open area which can be obtained from screenmanufacturers.)

V = velocity (fpm) above which a sand particleis transported; is related to permeability as follows:

P (gpd/ft2) V (fpm)

5000 10 (Max)4000 93000 82500 72000 61500 51000 4500 3

0-500 2 (Min)

(3) Diameter. The screen diameter shabe selected so that the entrance velocity through thescreen openings will not exceed 0.1 foot per secondThe entrance velocity is calculated by dividing the welyield in cubic feet per second by the total area of thescreen openings in square feet. This will ensure thefollowing:

(a) The hydraulic losses in thescreen opening will be negligible.

(b) the rate of incrustation will beminimal,

(c) the rate of corrosion will beminimal.

(4) Installation. Various procedures maybe used for installation of well screens.

(a) For cable-tool percussion androtary drilled wells, the pull-back method may be used. Atelescope screen, that is one of such a diameter that iwill pass through a standard pipe of the same size, isused. The casing is installed to the full depth of the wellthe screen is lowered inside the casing, and then the

casing is pulled back to expose the screen to the aquifer.(b) In the bail down method, the

well and casing are completed to the finished grade ofthe casing; and the screen, fitted with a bail-down shoe islet down through the casing in telescope fashion. Thesand is removed from below the screen and the screensettles down into the final position.

(c) For the wash-down method, thescreen is set as on the bail-down method. The screen islowered to the bottom and a high velocity jet of fluid isdirected through a self closing bottom fitting on thescreen, loosens the sand and allowing the screen to sinkto it final position. If gravel packing is used, it is placed

around the screen after being set by one of the abovemethods. A seal, called a packer, is provided at the topof the screen. Lead packers are expanded with aswedge block. Neoprene packers are self sealing.

(d) In the hydraulic rotary method odrilling, the screen may be attached directly to the bottomof the casing before lowering the whole assembly intothe well.

e. Gravel packing . Gravel packing is theprocess by which selected, clean, disinfected gravel isplaced between the outside of the well screen and theface of the undisturbed aquifer. This differs from thenaturally developed well in that the zone around thescreen is made more permeable by the addition o

coarse material. Gravel-pack material must be cleanand fairly uniform with smooth, well-rounded grainsGravel shall be siliceous material.

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(1) Size. Gravel size is based oninformation obtained by sieve analyses of the material inthe aquifer. The well screen aperture size will beselected so that between 85 and 100 percent of thegravel is larger than the screen openings. Criteria forsizing the gravel are as follows:

(a) Perform sieve analyses on allstrata within the aquifer. The sieve sizes to be used inperforming these analyses are:

3 in. No. 102 in. No. 2011/2 in. No. 401 in. No. 603/4 in. No. 140No. 4

The results of the analysis of any particular sampleshould be recorded as the percent (by weight) of thesample retained on each sieve and the cumulativepercent retained on each sieve (i.e., the total of thepercentages for that sieve and all larger sieve sizes).Based on these sieve analyses, determine the aquifer

stratum which is composed of the finest material.(b) Using the results of the sieve

analysis for the finest aquifer material, plot thecumulative percent of the aquifer material retainedversus the size of the mesh for each sieve. Fit a smoothcurve to these points. Find the size corresponding to a70 percent cumulative retention of aquifer material. Thissize should be multiplied by a factor between 4 and 6, 4if the formation is fine and uniform and 6 if the formationis coarse and nonuniform. Use 9 if the formationincludes silt. The product is the 70 percent retained size(i.e., the sieve size on which a cumulative 70 percent ofthe sample would be retained) of the gravel to be used in

the gravel pack. (c) The uniformity coefficient of thegravel will be 2.5 or less, where the uniformity coefficientis defined as the ratio of the grain size for 40 percentretention to the grain size for 90 percent retention.

(d) The plot of cumulative percentretention versus grain size for the gravel should beapproximately parallel to same plot for the aquifermaterial, should pass through the 70 percent retentionvalue and should have 40 and 90 percent retentionvalues such that the uniformity coefficient is less than2.5. Gravel pack material will be specified bydetermining the sieve sizes that cover the range of thecurve and then defining an allowable range for the

percent retention on each sieve.(2) Thickness. The thickness of the

gravel pack will range from a minimum of 3 inches to

approximately 8 inches. A gravel envelope thicker thanabout 8 inches will not greatly improve yield and canadversely affect removal of fines, at the aquifer-graveinterface, during well development.

(3) Pack length. Gravel pack will extenda minimum of 10 feet above the top of the screen. Ipossible, well development should be completed beforeadditional material is placed above the gravel pack. Thaway, gravel can be added as the pack consolidates. Ithis is not possible, a tremie may be placed prior to fillermaterial being added. Then additional gravel can beadded through the tremie to maintain gravel above thetop of the screen. A bentonite seal should be placeddirectly above the gravel pack to prevent infiltration fromfilter material. A gravel-pack well has been shownschematically in figure 5-6.

(4) Disinfection. It is important that thegravel used for packing be clean and that it also bedisinfected by immersion in strong chlorine solution (200mg/l or greater available chlorine concentrationprepared by dissolving fresh chlorinated lime or other

chlorine compound in water) just prior to placementDirty gravel must be thoroughly washed with clean waterprior to disinfection and then handled in a manner thatwill maintain it in as clean a state as possible.

f. Grouting and sealing. Grouting and sealingof wells are necessary to protect the water supply frompollution, to seal out water of unsatisfactory chemicaquality, to protect the casing from exterior corrosion andto stabilize soil, sand or rock formations which tend tocave. When a well is constructed there is normallyproduced an annular space between the drill hole andthe casing, which, unless sealed by grouting, provides apotential pollution channel.

(1) Prevention of contamination fromsurface. The well casing and the grout seal shouldextend from the surface to the depth necessary toprevent surface contamination via channels through soiand rock strata. The depth required is dependent on thecharacter of the formations involved and the proximity ofsources of pollution, such as sink holes and sewagedisposal systems. The grout seal around the casingshould have a thickness of at least 2 inches and agreater thickness is recommended where severecorrosive conditions are known to exist. Locaregulations may govern the grout length and thicknessMaterials for sealing and grouting should be durable andreadily placed. Normally, Portland cement grout wi

meet these requirements. Grout is customarily specifiedas a neat cement mixture having a water-cement ration

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of not over 6 gallons per 94-pound sack of cement.Small amounts of bentonite clay may be used to improvefluidity and reduce shrinkage. Grout can be placed byvarious methods, but to ensure a satisfactory seal, it isessential that grouting be:

-done as one continuous operation-completely placed before the initial set occurs-introduced at the bottom of the space to begrouted

Establishment of good circulation of water through theannular space to be grouted is a highly desirable initialstep toward a good grouting job. This assures that thespace is open and provides for the removal of foreignmaterial.

(2) Prevention of subsurfacecontamination. Formations containing water of poorquality and located above or below the desired waterformation must be sealed to prevent upward ordownward migration of inferior quality water into the well.Sealing of formations above or below the aquifer to beutilized can be accomplished by grouting the annular

space between drill hole and casing for the entire lengthof the casing or by grouting this annular space onlythrough formations containing water of poor quality. Ifonly the formations containing poor quality water are tobe grouted, the sections of the annular space not filledwith grout must be filled with sand to prevent caving ofthe surrounding strata and to support the grout beforethe grout has set. To provide a satisfactory seal, thegrout may need to extend 10 to 25 feet above and belowthe formation producing the mineralized water andshould be 2 to 6 inches thick in all locations.

g. Accessibility . The well location shall bereadily accessible for pump repair, cleaning, disinfection,testing and inspection. The top of the well shall never bebelow surface grade. At least two feet of clearancebeyond any building projection shall be provided.

h. Details relating to water quality. In additionto grouting and sealing, features that are related to waterquality protection are:

(1) Surface grading. The well or wellsshould be located on the highest ground practicable,certainly on ground higher than nearby potential sourcesof surface pollution. The surface near the site should bebuilt up, by fill if necessary, so that surface drainage willbe away from the well in all directions. Where flooding isa problem, special design will be necessary to insureprotection of wells and pumping equipment from

contamination and damage during flood periods and tofacilitate operation during a flood.

(2) Surface slab. The well casing shouldbe surrounded at the surface by a concrete slab having aminimum thickness of 4 inches and extending outwardfrom the casing a minimum of 2 feet in all directionsThe slab should be finished a little above ground leveand slope slightly to provide drainage away from thecasing in all directions.

(3) Casing. The well casing shouldextend at least 12 inches above the level of the concretesurface slab in order to provide ample space for a tightsurface seal at the top of the casing. The type of seal tobe employed depends on the pumping equipmentspecified.

(4) Well house. While not universallyrequired, it is usually advisable to construct a permanenwell house, the floor of which can be an enlarged versionof the surface slab. The floor of the well house shouldslope away from the casing toward a floor drain at therate of about 1/8 inch per foot. Floor drains should

discharge through carefully jointed 4 inch or larger pipeof durable water-tight material to the ground surface 20feet or more from the well. The end of the drain shouldbe fitted with a coarse screen. Well house floor drainsordinarily should not be connected to storm or sanitarysewers to prevent contamination from backup. The welhouse should have a large entry door that opens outwardand extends to the floor. The door should be equippedwith a good quality lock. The well house design shouldbe such that the well pump, motor, and drop-pipe can beremoved readily. The well house protects valves andpumping equipment and also provides some freezeprotection for the pump discharge piping beyond the

check valve. Where freezing is a problem, the welhouse should be insulated and a heating unit installedThe well house should be of fire- proof construction. Thewell house also protects other essential items. Theseinclude:

-Flow Meter-Depth Gage-Pressure Gage-Screened Casing Vent-Sampling Tap-Water Treatment Equipment (if required)-Well Operating Records

If climatic or other conditions are such that a well houseis not necessary, then the well should be protected

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from vandals or unauthorized use by a security fencehaving a lockable gate.

(5) Pit construction. Pit construction isonly acceptable under limited conditions such astemporary or intermittent use installations where the wellpump must be protected from the elements when not inuse. The design must allow for cleaning anddisinfection. Underground pitless construction for pipingand wiring may be adequate for submersible pumpinstallations. These designs may be used only whenapproved by the responsible installation medicalauthority.

i. Spacing and location. The grouping of wellsmust be carefully considered because of mutualinterference between wells when their cones ofdepression overlap. Minimum well spacing shall be 250feet.

(1) Drawdown interference. Thedrawdown at a well or any other location on the watertable is a function of the following:

-number of wells being pumped

-distance from point of measurement to pumpingwells

-volume of discharge at each well-penetration of each well into aquifer.

For simple systems of 2 or 3 wells, the method of superposition may be used. The procedure is to calculate thedrawdown at the point (well) of consideration and then toadd the drawdown for each well in the field. For multiplewells, the discharge must be recalculated for eachcombination of wells, since multiple wells have the effectof changing the depth of water in equations 5-1 and 5-2.For large systems the following conditions should benoted:

-boundary conditions may change-change in recharge could occur-recharge may change water temperature,

an increase in water temperature increases thecoefficient of permeability

-computer analysis may be helpful to recalculatethe combinations.It is seldom practicable to eliminate interference entirelybecause of pipeline and other costs, but it can bereduced to manageable proportions by careful well fielddesign. When an aquifer is recharged in roughly equalamounts from all directions, the cone of depression isnearly symmetrical about the well and "R" is about thesame in all directions. If, however, substantially more

recharge is obtained from one direction; e.g., a stream,then the surface elevation of the water table is distorted,being considerable higher in the direction of the stream.

The surface of the cone of depression will be depressedin the direction of an impermeable boundary becauselittle or no recharge is obtained from the direction of theimpermeable boundary.

(2) Location. Where a source orecharge, such as a stream, exists near the proposedwell field, the best location for the wells is spaced oualong a line as close as practicable to and roughlyparallel to the stream. On the other hand, multiple watesupply wells should be located parallel to and as far aspossible from an impermeable boundary. Where thefield is located over a buried valley, the wells should belocated along and as close to the valleys center aspossible. In hard rock country, wells are best locatedalong fault zones and lineaments in the landscape whererecharge is greatest. These are often visible using aeriaphotographs. Special care should be exercised to avoidcontamination in these terrains since natural filtration islimited.

j. Pumps. Many types of well pumps are onthe market to suit the wide variety of capacity

requirements, depth to water and power source. Electricpower is used for the majority of pumping installationsWhere power failure would be serious, the design shouldpermit at least one pump to be driven by an auxiliaryengine, usually gasoline, diesel or propane. The mosappropriate type is dictated by many factors for eachspecific well. Factors that should be considered foinstallation are:

-capacity of well-capacity of system-size of well-depth of water-power source

-standby equipment-well drawdown-total dynamic head-type of well

(1) Type. There are several types of welpumps. The most common are lineshaft turbinesubmersible turbine, or jet pumps. The first two operateon exactly the same principal. The difference beingwhere the motor is located. Line-shaft turbine pumpshave the motor mounted above the waterline of the weland submersible turbine pumps have the motor mountedbelow the water line of the well. Jet pumps operate onthe principal of suction lift. A vacuum is createdsufficient to "pull" water from the well. This type of pump

is limited to wells where the water line is generally nomore than 25 feet below the pump suction. It also hassmall capacity capability.

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(2) Choice. Domestic systems commonlyemploy jet pumps or small submersible turbine pumpsfor lifts under 25 feet. For deeper wells with highcapacity requirements, submersible or lineshaft turbinepumps are usually used and are driven by electric

motors. A number of pump bowls may be mounted inseries, one above the other to provide the necessarydischarge pressure. Characteristics for various types opumps used in wells are listed in table 5-5.

Table 5-5. Characteristics of pumps used in water supply systems.Source: Manual of Individual Water Supply Systems, UDHEW.

Practical Usual well- Usual

Type of Pump suction pumping pressure Advantages Disadvantages Remarkslift depths heads

Reciprocating:1. Shallow well... 22-26 ft. 22-26 ft 100-200 ft 1. Positive ac- 1. Pulsating dis- 1. Best suited for2. Deep well... 22-25 ft. Up to 600 Up to 600 tion. charge. capacities of 5-25

feet feet above 2. Discharge 2. Subject to vi- gpm against moder-cylinder. against variable bration and ate to high heads.

heads. noise. 2. Adaptable to3. Pumps water 3. Maintenance hand operation.containing sand cost may be high. 3. Can be installedand silt. 4. May cause de- in very small diame-4. Especially structive pres- ter wells (2" cas-

adapted to low sure if operated ing).capacity and high against closed 4. Pump must belifts. valve. set directly over

well (deep wellonly).

Centrifugal:1. Shallow well 20 ft. maxi- 10-20 ft. 100-150 ft. 1. Smooth, even, 1. Loses prime 1. Very efficienta. straight centrifu- mum flow. easily. pump for capacitiesgal (single stage) 2. Pumps water 2. Efficiency de- above 50 gpm &

containing sand pends on operat- heads up to aboutand silt. ing under design 150 feet.3. Pressure on heads & speedsystem is even &free from shock.4. Low-startingtorque.5. Usually relia-ble and good ser-vice life.

b. Regenerative 28 ft. maxi- 28 ft. 100-200 ft. 1. Same as 1. Same as 1. Reduction invane turbine type mum straight centrifu- straight centrifu- pressure w/in-(single impeller) gal except not gal except main- creased capacity not

suitable for tains priming as severe aspumping water easily straight centrifugal.containing sandor silt.2. They are self-priming.

2. Deep well Impellers 50-300 ft. 100-800 ft. 1. Same as shal- 1. Efficiency de-a. Vertical line submerged low well turbine. pends on operat-shaft turbine ing under design(multi-stage) head & speed.

2. Requires

straight welllarge enough forturbine bowlsand housing.3. Lubrication &alignment ofshaft critical.4. Abrasion from

sand.

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Table 5-5. Characteristics of pumps used in water supply systems.Source: Manual of Individual Water Supply Systems, UDHEW.

Practical Usual well- Usual

Type of Pump suction pumping pressure Advantages Disadvantages Remarkslift depths heads

b. Submersible tur- Pump & 50-400 ft. 80-900 ft. 1. Same as shal- 1. Repair to mo- 1. Difficulty w/seal-

bine motor sub- low well turbine. tor or pump re- ing has caused un-(multi-stage) merged 2. Easy to frost- quires pulling certainty as to

proof installa- from well. service life to date.tion. 2. Sealing of3. Short pump electrical equip-shaft to motor. ment from water

vapor critical.3. Abrasion fromsand.

Jet:1. Shallow well 15-20 ft. Up to 15-20 80-150 ft. 1. High capacity 1. Capacity re-

below ejec- feet below at low heads. duces as lift in-tor ejector. 2. Simple in op- creases.

eration. 2. Air in suction3. D oes not have or return lineto be installed will stop pump-over the well. ing.4. No movingparts in the well.

2. Deep well 15-20 ft. 25-120 ft. 80-150 ft. 1. Same as shal- 1. Same as shal- 1. The amount ofbelow ejec- 200 ft. low well jet. low well jet. water returned totor maximum ejector increase w/

increased lift-50%of total waterpumped at 50 ft. lift& 75% at 100 ft. lift.

Rotary:1. Shallow well 22 ft. 22 ft. 50-250 ft. 1. Positive ac- 1. Subject to(gear type) tion. rapid wear if

2. Discharge con- water containsstant under vari- sand or silt.able heads. 2. Wear of gears3. E fficient oper- reduces effi-

ation. ciency.2. Deep well Usually 50-500 ft. 100-500 ft. 1. Same as shal- 1. Same as shal- 1. A cutless rubber(helical rotary type) submerged low well rotary. low well rotary stator increases life

2. Only one mov- except no gear of pump. Flexibleing pump device wear. drive coupling hasin well. been weak point in

pump. Best adaptedfor low capacity &high heads.

1Practical suction lift at sea level. Reduce lift 1 foot for each 1,000 feet above sea level.

(3) Capacity selection. The designcapacity of the pump must exceed the systemrequirements. However, the capacity of the pump must

not exceed the capacity of the well. Pumpmanufacturers publish charts giving the pump discharge

capacity for their particular pumps at various operatingpressures. The total dynamic head (TDH) of the systemmust be calculated accurately from the physica

arrangement and is represented by the followingequation:

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where:HS = suction lift; vertical distance from

the waterline at drawdown underfull capacity, to the pump center-

lineHD = discharge head; vertical distance

from the pump centerline to thepressure level of the discharge pipesystem

HF = friction head; loss of head on pipelines and fittings

V2

= velocity head; head necessary to2g maintain flow

The brake horsepower of the motor used to drive thepump may be calculated from the following equation:

where:P = brake horsepower requiredH = total dynamic head in feetQ = volume of water in gpme = combined efficiency of pump and motor

5-7. Development and disinfectionAfter the structure of the well is installed, there remaintwo very important operations to be performed before thewell can be put into service. Well development is theprocess of removing the finer material from the aquiferaround the well screen, thereby cleaning out and opening

up passages in the formation so that water can enter thewell more freely. Disinfection is the process of cleaningand decontaminating the well of bacteria that may bepresent due to the drilling action.

a. Development . Three beneficial aspects ofwell development are to correct any damage or cloggingof the water bearing formation which occurred as a sideeffect of drilling, to increase the permeability of theformation in the vicinity of the well and to stabilize theformation around a screened well so that the well willyield sand-free water.

(1) A naturally developed well relies onthe development process to generate a highly permeablezone around the well screen or open rock face. Thisprocess depends upon pulling out the finer materialsfrom the formation, bringing them into the well, andpumping them out of the well. Development work shouldcontinue until the movement of fine material from theaquifer ceases and the formation is stabilized.

(2) Artificial gravel packing provides a

second method of providing a highly porous materiaaround the screen. This involves placement of aspecially graded gravel in the annular space between thescreen and the wall of the excavation. Developmenwork is required if maximum capacity is to be attained.

(3) Development is necessary becausemany drilling methods cause densification of theformation around the hole. Methods utilizing drillingfluids tend to form a mud cake. Good development wileliminate this "skin effect" and loosen up the sandaround a screen. Removal of fines leaves a zone of highporosity and high permeability around the well. Watercan then move through this zone with negligible headloss.

(4) Methods of development inunconsolidated formations include the following:

(a) Mechanical surging is thevigorous operation of a plunger up and down in the welllike a piston in a cylinder. This causes rapid movemenof water which loosen the fines around the well and they

can be removed by pumping. This may beunsatisfactory where the aquifer contains clay streaks orballs. The plunger should only be operated when a freeflow of water has been established so that the tool runsfreely.

(b) Air surging involves injecting aiinto a well under high pressure. Air is pumped into a welbelow the water level causing water to flow out. The flowis continued until it is free of sand. The air flow isstopped and pressure in an air tank builds to 100 to 150psi. Then the air is released into the well causing wateto surge outward through the screen openings.

(c) Overpumping is simply pumping

at a higher rate than design. This seldom brings besresults when used alone. It may leave sand grainsbridged in the formation and requires high capacityequipment.

(d) Backwashing involves reversaof flow. Water is pumped up in the well and then isallowed to flow back into the aquifer. This usually doesnot supply the vigorous action which can be obtainedthrough mechanical surging.

(e) High velocity jetting utilizesnozzles to direct a stream of high pressure wateroutward through the screen openings to rearrange thesand and gravel surrounding the screen. The jetting toois slowly rotated and raised and lowered to get the action

to all parts of the screen. This method works better oncontinuous slot well screens better than perforated typesof screens.

(5) Development in rock wells can beaccomplished by one of the surging methods listedabove or by one of the following methods.

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(a) Explosives can be used to breakrock formations. However it may be difficult to tell inadvance if the shooting operation will produce therequired result.

(b) Acidizing can be used in wells inlimestone formations. Fractures and crevices areopened up in the aquifer surrounding the well hole by theaction of the acid dissolving the limestone.

(c) Sand fracking is the action offorcing high pressure water containing sand or plasticbeads in to the fractures surround a well. This serves toforce the crevices open.

b. Disinfection of completed well. Thedisinfection of the completed well shall conform toAWWA A100.Bacteriological samples must be collected and examinedin accordance with Standard Methods for theExamination of Water and Wastewater.

c. Disinfection of flowing artesian wells.Flowing artesian wells often require no disinfection, but ifa bacteriological test, following completion of the well,

shows contamination, disinfection is required. This canbe accomplished as follows. The flow from the well willbe controlled either by a cap or a standpipe. If a cap isrequired, it should be equipped with a one-inch valve anda drop-pipe extending to a point near the bottom of thewell. With the cap valve closed, stock chlorine solutionwill be injected, under pressure, into the well through thedrop-pipe in an amount such that when the chlorinesolution is dispersed throughout all the water in the well,the resultant chlorine concentration will be between 50and 100 mg/l. After injection of the required amount ofstock chlorine solution, compressed air will be injectedthrough the drop-pipe, while simultaneously partially

opening the cap valve. This will permit the chlorinesolution to be mixed with the water in the well. As soonas chlorine is detected in the water discharged throughthe cap valve, the air injection will be stopped, the capvalve closed and the chlorinated water allowed to remainin the well for 12 hours. The well will then be allowed toflow to waste until tests show the absence of residualchlorine. Finally, samples for bacteriological examinationwill be collected in accordance with Standard Methodsfor the Examination of Water and Wastewater. If thewell flow can be controlled by means of a standpipe,disinfection can be accomplished as described for awater table well.

5-8. Renovation of Existing WellsWell yield can be maintained by proper operatingprocedures. The most common cause of dediningcapacity in a well is incrustation which results frommaterial being deposited on the well screen and thereby

clogging the openings. A second cause is corrosion othe screen which is a chemical reaction of the metalThis action results in the screen being dissolved andenlarging the openings, allowing caving to occurRecords of pump performance and pumping levels arevery important in a good maintenance program.

a. Incrustation . The effect of incrustation isusually decreased capacity due to clogging of the screenopenings. For incrustation due to calcium deposits oprecipitation of iron and manganese compoundstreatment with an acid solution will dissolve the depositsand open up the screen. For bacterial growths and slimedeposits, a strong chlorine solution has been foundeffective. In some instances, explosives may be used tobreak up incrustation from wells in consolidated rockaquifers.

b. Corrosion . The best method to prevencorrosion is to use a metal which is resistant to theattack. Once a screen has deteriorated, the only methodof rehabilitation may be to remove it and install a newscreen. The design of the initial installation should allow

for removal of the screen in the future. Corrosion is alsoa problem in pumps. The use of pumps constructed ospecial non-corrosive materials will help. Care should betaken to use pumps with single metal types. Chemicainhibitors can be injected into wells to prevent corrosionbut this is costly.

c. Downhole Inspections. Special televisionequipment has been developed to permit a visuainspection of a wel