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(210-vi-AWMFH, May 1996) United States Department of Agriculture Natural Resources Conservation Service Agricultural Waste Management Field Handbook Chapter 13 Operation, Maintenance, and Safety

Chapter 13: Operation, Maintenance, And 651 Agricultural Waste Management Field Handbook Chapter 13 Operation, Maintenance,

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  • Part 651Agricultural Waste ManagementField Handbook

    Operation, Maintenance, and SafetyChapter 13

    131(210-vi-AWMFH, May 1996)

    United StatesDepartment ofAgriculture


    AgriculturalWaste ManagementField Handbook

    Chapter 13 Operation, Maintenance,and Safety

  • Part 651Agricultural Waste ManagementField Handbook

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    Issued May 1996

    The United States Department of Agriculture (USDA) prohibits discrimina-tion in its programs on the basis of race, color, national origin, sex, religion,age, disability, political beliefs, and marital or familial status. (Not all pro-hibited bases apply to all programs.) Persons with disabilities who requirealternative means for communication of program information (braille, largeprint, audiotape, etc.) should contact the USDA Office of Communicationsat (202) 720-2791 or (202) 720-7808 (TDD).

    To file a complaint, write the Secretary of Agriculture, U.S. Department ofAgriculture, Washington, DC 20250, or call (202) 720-7327 or (202) 720-1127(TDD). USDA is an equal employment opportunity employer.

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    Chapter 13 Operation, Maintenance,and Safety

    651.1300 Introduction 131

    651.1301 Operation 131

    (a) Production function operation .................................................................. 131

    (b) Collection function operation ................................................................... 131

    (c) Storage function operation ........................................................................ 132

    (d) Treatment function operation ................................................................... 133

    (e) Transfer function operation ...................................................................... 134

    (f) Utilization function operation ................................................................... 135

    651.1302 Maintenance 136

    (a) Production function maintenance ............................................................ 137

    (b) Collection function maintenance .............................................................. 137

    (c) Storage function maintenance .................................................................. 137

    (d) Treatment function maintenance ............................................................. 138

    (e) Transfer function maintenance ................................................................. 139

    (f) Utilization function maintenance ............................................................. 139

    651.1303 Safety 1310

    (a) Hazards from gases ................................................................................... 1310

    (b) Hazards with impoundments ................................................................... 1313

    (c) Hazards in equipment operation ............................................................. 1315

    651.1304 Agricultural waste management system plans 1316

    651.1305 References 1317

    651.1350 Appendix 13ACalibrating Manure Spreaders

    651.1360 Appendix 13BManure, Soil, and Plant Testing

    651.1370 Appendix 13COperation, Maintenance, and Safety Guidelines

    651.1380 Appendix 13DAgricultural Waste Management System

    Troubleshooting Guideline

    651.1390 Appendix 13EExample Agricultural Waste Management

    System Plan

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    Figures Figure 131 Stage storage curve 132

    Figure 132 Maintenance of minimum treatment volume 134

    Figure 133 Manure spreader calibration 135

    Figure 134 Waste storage pond warning sign 137

    Figure 135 Confined space warning signs 1312

    Figure 136 Waste storage pond safety features 1314

    Figure 137 Personal safety equipment 1315

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    Chapter 13 Operation, Maintenance, and Safety

    651.1300 Introduction

    The purpose of an Agricultural Waste ManagementSystem (AWMS) is to control and use by-products ofagricultural production in a manner that sustains orenhances the quality of air, water, soil, plant, andanimal resources. Important to the success in achiev-ing this purpose is adequate design and constructionof the AWMS. At least as important to a system'ssuccess are its proper operation and maintenance(O&M). Safety is always coupled with proper O&M asan essential and integral part.

    This chapter describes actions that would be taken bythe operator of an AWMS or choices that would bemade by the decisionmaker. It recognizes that thedecisionmaker and the operator for an AWMS may notbe the same person. For example, on an absenteeowner's farm the decisionmaker and the operator aremost likely different people. However, for the purposeof this chapter, reference to the decisionmaker impliesthe operator when appropriate to the context. Theoperation and maintenance described in this hand-book is not all inclusive, but addresses the most com-mon components.

    Two prerequisites are necessary for proper O&M.First, the decisionmaker must have been involvedthroughout the decisionmaking process in planningthe AWMS. This is essential if the decisionmaker is toaccept full ownership of what is planned. Second, thedecisionmaker must have a complete understanding ofthe systems O&M requirements. The AWMS plan is anessential tool for conveying these requirements to thedecisionmaker. An AWMS plan is prepared as anintegral part of and in concert with conservation plans.The purpose of this chapter is to discuss generaloperation, maintenance, and safety requirements foran AWMS.

    651.1301 Operation

    Operation of an AWMS includes the administration,management, and performance of nonmaintenanceactions needed to keep the system safe and function-ing as planned. The operation actions required dependon such factors as the type of enterprise, the compo-nents of the system, and the level of management.Because of this, the operational requirements for eachAWMS must be system-specific. Following is a generaldescription of the operational requirements for eachfunction of an AWMS.

    (a) Production functionoperation

    The majority of the operational actions required forthe production function are managerial. Examples ofoperation actions could include management of theamount of bedding and washwater used. The AWMSplan should document the production rate assumed inthe design of the system and give a method for deter-mining the actual rate. An important reason for doingthis is to assure that the actual rate does not exceedthat assumed in the design of the system. Repercus-sions can occur if the design rate is exceeded. Forexample, a storage facility of an AWMS could fill upmore quickly than anticipated, requiring that thefacility be emptied earlier than intended. A response isneeded where a production rate exceeds design as-sumptions. For a dairy operation, the response mightbe reducing the amount of daily washwater used,excluding clean water entering the system, or enlarg-ing the storage facility.

    (b) Collection function operation

    The collection function involves the initial capture andgathering of waste from the point of origin or deposi-tion to a collection point. The managerial aspects ofthis function involve frequency and timing, whichshould be described in the AWMS plan. Frequency ofcollection is dependent on the type of operation. For afeedlot, the frequency of collection might be only oncea year. On the other hand, a dairy with a flush systemmight collect waste several times a day.

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    Timing of collection can be an important consider-ation. For a feedlot without a storage facility, thetiming should coincide with when the waste can beutilized. Timing for a poultry broiler operation may bemost appropriate between production cycles when thefacility is empty of birds.

    (c) Storage function operation

    Storage function components include waste storageponds and structures. Storage structures include tanksand stacking facilities. Monitoring storage levels inrelationship to the storage period is of prime impor-tance in the operation of storage components.

    The AWMS plan should give target storage levels bydate throughout the storage period. To assure that thefacilities do not fill prematurely, these levels shouldnot be exceeded. An excellent way to present this inthe AWMS plan is to equip an impoundment typestorage facility with a staff gauge so that target gaugereadings versus dates are given. A stage-storage curve(fig. 131) can also assist the decisionmaker in moni-

    toring the storage's filling. The stage-storage curverelates the pond's water surface at any elevation to thepond's storage at that elevation. For example, if thewaste storage pond for figure 131 was measured ashaving a water surface elevation of 304 feet, it can bedetermined using the stage-storage curve that thepond contains 12,500 cubic feet of wastewater at thatelevation. This storage can then be compared to antici-pated storage if the pond had filled at the design fillingrate.

    To illustrate comparing actual versus design fillingrate using the stage-storage curve, say the pond aboveis in its 50th day of the storage period, and the designfilling rate is 200 cubic feet per day. Therefore, thetarget storage level for that day would be: 200 cubicfeet per day times 50 days, or 10,000 cubic feet plusthe depth of precipitation less evaporation assumed tooccur during this 50-day period.

    Using the stage-storage curve, it can be determinedthat at a storage of 10,000 cubic feet the water surfaceelevation in the pond would be 303.4. Add the assumeddepth of precipitation less evaporation assumed forthis 50-day period to this elevation.

    Figure 131 Stage-storage curve

    Top of embankment - elev. 309.5310





    3000 10 20 30 40 50

    Storage - cubic feet x 1,000



    on -

    feet Spillway crest - elev. 308.2

    Elevation 304

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    For this example, if the precipitation less evaporationwas assumed in design to be 0.6 feet, the target fillingelevation for the 50th day would be 303.4 + 0.6 = 304.0,which would indicate actual filling is at the assumeddesign rate. However, actual precipitation amountsmay vary from that assumed in design. For this reason,actual precipitation less evaporation should also beevaluated. For example, if the actual precipitation isless than that assumed, it would mean the pond aboveis filling at a rate in excess of the 200 cubic feet perday. On the other hand, if the actual precipitation lessevaporation is more, the pond is filling at a rate lessthan the 200 cubic feet per day.

    Keeping a record of the waste accumulation through-out the storage period should be recommended. Arecord of precipitation and evaporation amounts mayalso be important in determining the source of filling.

    Storage components are generally operated so theyare empty at the beginning of the storage period andare filled to or below capacity at the end. The manage-ment of storage components may need to be coordi-nated with the management of the production functionif the rate of filling exceeds that assumed in design.Uncovered impoundment storage components aresubject to storm events that prematurely fill them. TheAWMS plan should describe a procedure for emptyingthese facilities to the extent necessary in an environ-mentally safe manner to provide the capacity neededfor future storms.

    The design of liquid storage components may require astorage volume reserve for residual solids after theliquids have been removed. The amount reserved forthis purpose depends on such things as the agitationbefore pumping and the care taken in pumping.

    (d) Treatment function operation

    Treatment components include waste treatment la-goons, composting, oxidation ditches, solid/liquidseparation, and drying/dewatering. The treatmentfunction reduces the polluting potential of the wasteand facilitates further management of the waste.Proper operation of this function is essential if thedesired treatment is to be achieved.

    (1) Waste treatment lagoonsProper operation of waste treatment lagoons includesmaintaining proper liquid levels and assuring that themaximum loading rates are not exceeded. Lagoons aredesigned for an assumed loading rate. The AWMS planshould document the maximum loading rate andsuggest that it be monitored to assure that it is notexceeded. This can be done by comparing the sourcesand amounts of waste entering the lagoon to what wasconsidered in design, such as number of animals.

    Laboratory testing may be required if loading becomesa serious question. If the design loading rate is ex-ceeded, the lagoon may not treat the waste as neededand undesirable and offensive odors may result. Therate of filling is important as well. If the rate of fillingexceeds the design rate, the storage period is reducedand the lagoon must be pumped more frequently. Seesection 651.1301(c). The AWMS plan should describe aprocedure for emptying part of the lagoon contentsfollowing a storm event that fills the lagoon prema-turely to near its capacity to provide storage for futurestorms.

    The AWMS plan must emphasize the need to maintainthe liquid level in anaerobic lagoons at or above theminimum design volume (fig. 132). The proper pHmust also be maintained if the desired treatment is tobe achieved. As such, the pH should be measuredperiodically. The minimum acceptable pH is about 6.5.If pH falls below 6.5, a pound of hydrated lime or lyeshould be added per 1,000 square feet of lagoon sur-face daily until the pH reaches 7.0.

    Aerobic lagoons require a design surface area and adepth within the range of 2 to 5 feet to effectively treatwaste. This information must be provided in theAWMS plan. Mechanically aerated lagoons require thata minimum design volume be maintained and thedesigned amount of aeration be provided for effectivetreatment and odor reduction. The plan should recom-mend that these operational aspects be carefullymonitored.

    (2) Composting facilitiesComposting requires careful management to effec-tively treat waste. It relies on a proper blend of ingre-dients, called the recipe, to achieve the microbialactivity necessary to stabilize reactive constituentsand to attain the temperature necessary to destroydisease-causing organisms. For this reason, the AWMS

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    plan should address careful monitoring of internaltemperatures in the compost pile. The plan should givethe recipe and recommendations for its adjustment ifthe temperature levels are either too low or too high.Caution should be given to the potential for spontane-ous combustion. The plan must also address mixingrequirements. See chapter 10 for a complete discus-sion of the management responses necessary foreffective composting.

    (3) Solid/liquid separationSolid/liquid separation facilities include settling basinsand a variety of stationary and mechanical screeningdevices. Maximum and minimum allowable flow ratesare critical for these type facilities and need to bedocumented in the AWMS plan. If the flow rate ex-ceeds the rate assumed in design, the residence time insettling basins may not be adequate for efficient set-tling. If it exceeds the design capacity of a screeningdevice, its efficiency will diminish. Generally, thescreen manufacturers information provides data onminimum and maximum flow rates. However, thedecisionmaker may need to fine tune the flow rate tofit the consistency of waste produced.

    The frequency of cleaning out settling basins needs tobe established by the design and documented in theAWMS plan. Solids sometimes adhere to screeningdevices and, if allowed to dry, can clog the screen.Rinsing the screen following use should be empha-sized in the AWMS plan as a way to help avoid thisproblem.

    (4) Oxidation ditchesOxidation ditches require a high level of managementto effectively treat the waste in a safe manner. Carefulattention must be given to assure that pumps andother equipment are operating properly and that theditch is not overloaded. Velocities must be maintainedthat do not permit solids to settle and accumulate.Input from the designer is essential in developing theoperational requirements for oxidation ditches.

    (e) Transfer function operation

    Transfer function components include reception pits,pipelines, picket dams, pumps, and other equipment,such as tank wagons, agitators, chopper-agitationpumps, and elevators. A surveillance type inspectionshould be recommended to assure that the compo-nents are functioning properly.

    A clean water flush following use of pipelines, tankwagons, and conveyors is helpful in minimizing thebuild up of sludge. Methods for unplugging pipelinesshould be described. Draining of pipelines or otherprotective freeze protection measures should beaddressed.

    Struvite, a phosphate mineral that can form a hard-scale deposit in pipelines and other similar wastetransfer components, is a potential problem in anAWMS that utilizes recycled lagoon or waste storagepond effluent for flushing. Occasional clean water

    Figure 132 Maintenance of minimum treatment volume

    Minimum treatmentvolume

    Do notemptybelowthis


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    flushes of the transfer component or addition ofstruvite formation inhibitors to the wastewater may beeffective in reducing struvite buildup. If a struvitebuildup occurs, the system may need to be cleanedwith an acid solution.

    Proper agitation prior to transfer needs to be de-scribed in the AWMS plan. Agitation should be contin-ued long enough so that the solids in the waste, includ-ing those in corners and recesses, are moved intosuspension. The plan should address the spacing andduration of agitation. It should also give any precau-tions needed during agitation to prevent damage topond liners. The consequences of inadequate agitationcan be solids buildup, which can lead to difficultproblems.

    (f) Utilization function operation

    Utilization is a function in an AWMS for the purpose oftaking advantage of the beneficial properties of agri-cultural wastes, such as its nutrient content. Compo-nents of utilization are land application of nutrientsand biogas generation. Land application is the mostprevalently used method.

    The AWMS plan should establish the amount, method,placement, and timing of land application of agricul-tural wastes. The timing required should considerclimate and stage of crop growth to maximize cropuptake and minimize environmental impact. Timingshould also consider the potential for prematuregermination of planted crops if the waste is appliedtoo early. Testing the waste and the soil for nutrientcontent must be recommended as good practice foruse in determining the actual rates of application. Seeappendix 13A for more information on manure testing.

    For liquid waste applied with an irrigation system, theplan should give sprinkler numbers, size and types ofsprinklers, length of setting, and flow rates of wasteand dilution water, if any. For slurry or solid wastes,the plan should indicate the necessity of calibratingspreading equipment to assure the desired rate ofapplication is achieved (fig. 133). Appendix 13A alsodescribes several methods of manure spreader calibra-tion.

    Utilization involving biogas/methane production andrecovery requires a high level of management to besuccessful. Complicating the operation of a digester iscoordinating use of gas once it is produced. Sincecompression and storage of biogas is not practical, itsuse must generally match the energy production. Thedesigner of the biogas system must be involved indeveloping the specific operational requirements.

    Figure 133 Manure spreader calibration

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    Methane production and recovery system optionsinclude the covered anaerobic lagoon, complete mixdigester, and plug flow digester. Because each oper-ates at a constant level and does not provide for wastestorage, they must be operated in conjunction with astorage facility of some type. Operation of biogascomponents is dependent upon proper loading ofwaste in terms of volatile solids, total solids, andwaste volume. As such, their loading must be care-fully monitored. Some manure requires treatment,such as solid/liquid separation and dilution, before itenters a lagoon or digester. The amount of gas pro-duced is a good indication of proper loading. If gasproduction falls off, the loading should be checked.

    (1) Covered anaerobic lagoonOperation of a covered lagoon for biogas productionis much like that of a lagoon not associated withbiogas production. The exceptions are that it is oper-ated to have a constant liquid level, loaded at a higherrate, and has a minimum hydraulic retention time.

    The inlet and outlet of the covered lagoon must re-main free-flowing to maintain the required liquid level.The lagoon cover requires special attention to assurethat methane produced is captured and directed towhere it will be used. The cover should be periodi-cally inspected for accumulation of excessive rainwa-ter, tearing, wear holes, and proper tensioning. Exces-sive rainwater should be removed in the mannerprescribed by the designer, usually by pumping ordraining it into the lagoon or storage facility.

    (2) Complete mix and plug flow digestersThese digesters require a constant temperature withina narrow range of variation to produce an optimumamount of biogas. Temperature is maintained by aheating system. The digester operating temperaturemust be monitored and kept within the temperaturerange specified by the designer. If the heating systemis not functioning properly, waste should be routedaround the digester to the storage facility. Both di-gesters have a cover of some kind. Like the lagooncover, they must be periodically inspected to assurethey are in good condition and are directing the gas tothe exit point.

    Effluent from anaerobic digesters has essentially thesame amount of nutrients as the influent. As such, theO&M plan must address use of the effluent for landapplication.

    651.1302 Maintenance

    Maintenance of an AWMS includes actions that aretaken to prevent deterioration of the system compo-nents, to repair damage, or to replace parts. Mainte-nance includes routine and recurring actions. Thepurpose of maintenance is to assure proper function-ing and to extend the service life of AWMS compo-nents and equipment.

    The two types of maintenance required by an AWMSare preventive and reactive. Preventive maintenanceinvolves performing regularly scheduled procedures,such as lubricating equipment and mowing grass.Reactive maintenance involves performing repairs orrehabilitation of system components and equipmentwhen they have deteriorated or cease to functionproperly. Examples of reactive maintenance includerepair of a leak in a waste storage structure and re-placement of a badly corroded piece of pipeline.

    Essential to reactive maintenance is the discovery ofitems requiring attention before there is a seriousconsequence. Timely discovery can best be accom-plished by regularly scheduled inspection of theAWMS components and equipment. The general main-tenance and inspection requirements that should beconsidered for inclusion in the AWMS plan for eachfunction of an AWMS are described in this section.

    Proper maintenance of equipment used in an AWMS isessential for continuous operation. A thorough inven-tory of each function and its related equipment isrecommended as a way to organize what must bemaintained. The AWMS plan should recommendactions that will assist in the maintenance of equip-ment. An action to include would be collecting and filinginformation on equipment, such as name plate data,shop manuals, catalogs, drawings, and other manufac-turer information. Other actions to recommend:

    Prepare checklists that give required mainte-nance and maintenance frequency.

    Keep a log book of the hours each piece ofequipment is used to assist in determiningwhen maintenance should be performed.

    Keep a replacement parts list indicating wherethe parts can be obtained.

    Keep frequently needed replacement parts onhand.

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    (a) Production functionmaintenance

    (1) Roof gutters and downspoutsA good time to inspect roof gutters and downspouts isduring storm events when leaks and plugged outletscan easily be discovered. Maintenance items wouldinclude cleaning debris from the gutters, unpluggingoutlets, repair of leaks, repair or replacement of dam-aged sections of gutters and downspouts, repair ofgutter hangers and downspout straps, and repair ofprotective coatings.

    (2) DiversionsMaintenance of diversions includes, as appropriate tothe type of construction, mowing vegetation, eliminat-ing weeds, repair of eroded sections, removal of debrisand siltation deposits, and repair of concrete. Inspec-tions should be made on a regularly scheduled basisand after major storm events.

    (b) Collection functionmaintenance

    Maintenance requirements for the collection functionare primarily directed at mechanical equipment. Regu-larly scheduled lubrication and other preventive main-tenance must be performed on electric motors,sprockets, and idle pulleys according to themanufacturers recommendations.

    Flush systems employ pumps, valves, and mechanicalequipment involving gear boxes, stems, and guides.This type equipment also needs regularly scheduledpreventive maintenance. Broken sprockets, idlepulleys, drive cables and rods, chains, and scraperblades must be repaired when they are seen to bedamaged.

    Tractors used in collection must be regularly main-tained according to the manufacturers recommenda-tions. Equipment used in collection must be underconstant surveillance to assure continuous and properoperation. Grates and covers on reception pits must bekept in place and in good condition.

    (c) Storage function maintenance

    (1) Waste storage pondsRegularly scheduled inspections and timely mainte-nance are required for waste storage ponds becausetheir failure can result in catastrophic consequences.The consequences of failure may affect public safetyand environmental degradation. Inspections shouldfocus on and result in the repair of leaks, slope fail-ures, excessive embankment settlement, erodedbanks, and burrowing animals.

    Flow from toe and foundation drains should be in-spected for quantity of flow changes and for discol-oration. If flows from these drains suddenly increase,it could mean a leak has developed. If the flow isnormally clear and suddenly becomes cloudy with silt,piping of the embankment could be suspected. Appur-tenances, such as liners, concrete structures, pipe-lines, and spillways, need to be inspected and repairedif found to be deficient. Vegetative cover needs to beroutinely maintained by mowing, and weeds andwoody growth need to be eliminated. Safety features,such as fences, warning signs (fig. 134), tractor stopblocks, and rescue equipment, need careful mainte-nance.

    Earthen waste storage ponds should be inspectedcarefully during and after they are emptied. Generally,these ponds are completely emptied over a short time.A consequence of this drawdown may be inside bankfailures, especially where the pond is constructed inheavier soils or has an imported soil liner constructed

    Figure 134 Waste storage pond warning sign




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    of heavier soils. Therefore, it should be recommendedthat the pond be carefully inspected during and imme-diately after emptying. Some pond features are bestinspected when the pond is filling or is full. For ex-ample, inspection for toe drainage and foundationleaks is best done when the pond is filling or full.

    (2) Waste storage structurestanksInspection and maintenance of waste storage tanksdepend on the type of tank and the material used inconstruction. However, regardless of the constructionthey should be inspected regularly for leaks and degra-dation. Concrete tanks should be inspected on aregularly scheduled basis for cracks and degradationof the concrete. Any sudden or unexpected drop orrise in the liquid level should be documented, thecause investigated, and the problem corrected.

    Inspection or repair of waste storage tanks is a hazard-ous undertaking because it may involve entry into thetank where toxic, oxygen displacing, or explosivegases may be present. The safety section of this chap-ter gives a procedure for safe entry into confinedspaces. Because of the caustic nature of wastes, aspecialist in the repair of concrete should be consultedif cracks or degradation of concrete are observed.

    An important consideration for below ground tanks ismaintaining the water table below the elevationsassumed in the design of the tank. Drains installed tocontrol the water table must be inspected on a regularbasis to assure that they are operating properly. Ifapplicable, a caution should be included in the AWMSplan that liquid waste or water should not be allowedto pond on the ground surface surrounding the tank.This ponding can result in hydrostatic pressures thatexceed the tanks design loadings, which can causecracking or uplift.

    A popular material for aboveground waste storagetanks is fused glass-coated steel. This material isvirtually indestructible to the caustic action of thewaste if the coating remains intact; however, deterio-ration of the steel may result if the coating is damaged.As such, it is important that the surface of these tanksbe regularly inspected and repairs made. The areaaround bolts should be checked for loss of coating andrusting. Repairs should be made according to themanufacturers recommendations.

    Cathodic protection is required for some installations.When included, the cathodic protection system shouldbe inspected to assure that it is functioning properly.The cathodic protection inspection requirements aredependent upon the type of system installed. Thedesigner of the cathodic protection should be con-sulted on what to include in the O&M plan.

    Steel tanks generally are not designed to withstand aload against the outside of the tank. Because of this,waste or other material should not be allowed to buildup against the outside wall of the tank.

    Careful attention needs to be given to the maintenanceof safety features associated with waste storage tanks.These features include warning signs, grates and lidsfor openings, fences, barriers, and rescue equipment.Grates, lids, and gates should be secured in placewhen left unattended.

    (3) Waste storage structuresStackingfacilities

    Concrete and lumber are used in the construction ofwaste stacking facilities. Concrete should be inspectedfor cracks and premature degradation. If any problemsare found with the concrete, appropriate repairsshould be made.

    Lumber should be inspected for damage either bynatural deterioration or from man, animal, or weatherevent causes. Damaged lumber should be replaced.Roofs should be inspected regularly for leaks anddamaged trusses, and repairs made promptly.

    (d) Treatment functionmaintenance

    (1) Waste treatment lagoonsThe inspection and maintenance requirements for awaste treatment lagoon are about the same as thosefor a waste storage pond. One difference is that pondsgenerally are completely emptied, whereas lagoonsretain a minimum storage pool. Maintenance of aer-ated lagoons would be complicated by the aerationequipment involved. The AWMS plan should indicatethat the maintenance of the aeration equipment is tobe according to the manufacturers recommendations.

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    (2) Composting facilitiesComposting facilities vary widely mainly becausethere are several methods of composting. However,many facilities use standard construction materials,such as concrete, concrete blocks, lumber, and steel.

    Concrete should be inspected regularly for cracks anddeterioration, and repaired as necessary. Lumbershould be inspected for deterioration and physicaldamage, and replaced if found to be nonservicable.Protective coatings for steel structures should beinspected and repaired when damage is found. Manu-factured composters should be maintained accordingto the manufacturers instructions.

    (3) Solid/liquid separation facilitiesSettling basins are constructed of earth, concrete, orother material. Inspection and maintenance of thesefacilities are much the same as those for componentsconstructed of similar material.

    Screening devices are generally constructed usingvarious kinds of steel. These devices should be in-spected regularly for deterioration of protective coat-ings, and repaired as necessary. Many of these devicesalso involve the use of electric motors, pumps, andgears. These should be routinely maintained as recom-mended by the manufacturer.

    (4) Oxidation ditchesThe channel for oxidation ditches is generally con-structed of concrete. The concrete should be in-spected regularly for cracks and deterioration, andrepairs made as needed. The rotor should be lubri-cated regularly and inspected for proper operation.Other equipment, such as pumps, agitators, and valvesused in its operation, should be maintained as recom-mended by the manufacturer.

    (e) Transfer functionmaintenance

    Components and equipment for the transfer functionof an AWMS vary widely. Manufactured transfer equip-ment, such as pumps, conveyors, and tank wagons,should be maintained according to the manufacturersinstructions. Pipelines should be inspected to assurethat proper cover is maintained, vents are not plugged,valves are working properly, and inlet and outletstructures are in good condition.

    (f) Utilization functionmaintenance

    Waste utilization equipment includes solid manurespreaders, liquid manure spreaders, injection equip-ment, and irrigation equipment. The equipment shouldbe maintained according to the manufacturers recom-mendation.

    If covered lagoons are used for biogas production,maintenance is similar to that needed for uncoveredlagoons. The covered lagoons and other covereddigesters need routine inspection of the covers orenclosures to check for tears or other opening thatwould allow gas to escape. Timely repairs must bemade. The covered lagoon is generally designed for aconstant level that is controlled by a pipe that dis-charges to either another lagoon or a waste storagepond. This pipe must be kept free of obstructions.Digestors accumulate sludge that must be periodicallyremoved. Some digesters are heated, and use pumps tocirculate heated water. These pumps must lubricatedand impellers and seals repaired as necessary.

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    651.1303 Safety

    Safety hazards are inherent to an agricultural wastemanagement system. Some of these hazards lie hiddenand await the unsuspecting. Others may be moreobvious, but are just as formidable to the careless. Forthese reasons, attention to safety must always be givenfirst consideration in the planning, design, construc-tion, and operation of an AWMS.

    Hazards associated with an AWMS can be minimizedby incorporating safety features in the design andconsequent construction of AWMS components. TheAWMS plan needs to address operation and mainte-nance of these safety features. The safe operationrequires that those involved in its operation be awareof the systems hazards, follow procedures of safeoperation, and maintain its safety features. Theseprocedures must be clearly defined in the AWMS plan.

    Hazards associated with an AWMS are many and lurkin each of its functions. Because safety hazards ofsimilar nature are not limited to one function, they willbe described as those associated with gases, impound-ments, and equipment operation.

    Most states have rules and regulations for occupa-tional safety and health in agricultural operations. Thestate occupational safety and health agency should becontacted to determine applicable regulations. TheAWMS plan should be developed to be in accordancewith these rules and regulations and the type of haz-ards that will be involved in the AWMS.

    (a) Hazards from gases

    A variety of gases can be generated in the operation ofan AWMS. Some of these gases are toxic and cancause illness and even death at relatively low concen-trations. Other gases are not toxic, but can displaceoxygen and result in asphyxiation. What makes thesegases especially insidious is that some are colorlessand odorless, and defy detection except with special-ized equipment. Colorless gases produced by anAWMS include carbon dioxide, ammonia, hydrogensulfide, and methane. Numerous odorous gases areproduced by an AWMS. These gases fall into the gen-

    eral classification of amines, amides, mercaptans,sulfides, and disulfides.

    No direct tie between odors and safety problems hasbeen found; however, odors can be a nuisance andcause complaints and even lawsuits. As such, they arean important consideration in the operation of anAWMS and need to be minimized. Chapter 8, SitingAgricultural Waste Management Systems, describesways that odor problems can be minimized.

    Gases can accumulate in any area of an AWMS whereproper ventilation is not provided, such as animalhousing and covered manure impoundments. Certainactivities, such as agitation, can release gases that cancause problems if the facility is not properly venti-lated. The major gases that may be produced by anAWMS and the consequences if these gases are en-countered by humans and animals are described in thefollowing paragraphs.

    (1) Gases produced in an AWMSCarbon dioxide (CO2)Carbon dioxide is a by-product of manure decomposition. Most of the gasbubbling up from storage and lagoons is CO2. Carbondioxide is not highly toxic in itself, but contributes tooxygen deficiency or asphyxiation. Concentrationsabove 10 percent (by volume) can cause a human topant violently, and at increased levels are narcoticeven if adequate oxygen is available. At 25 percentconcentration, death occurs to humans after a fewhours. Animals can tolerate up to a 7 to 9 percent CO2concentration, but with considerable discomfort.Concentrations above 10 percent may cause dizzinessand even unconsciousness in animals.

    Ammonia (NH3)Ammonia is released from freshmanure and anaerobic decomposition. Odors from aslittle as 0.0001 percent concentration can be detectedand identified. Mixtures over 16 percent with air areexplosive. Low concentrations, 0.0025 to 0.0030 per-cent, can irritate eyes and the respiratory tract ofhumans; higher levels can cause suffocation. Ammoniais an irritant to animals at concentrations up to 0.02percent inducing sneezing, salivation, and appetiteloss. Above 0.005 percent, eye inflammation developsin chickens. Prolonged exposure may increase respira-tory diseases and pneumonia.

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    Hydrogen sulfide (H2S)Hydrogen sulfide is pro-duced by anaerobic decomposition of organic wastes.It smells like rotten eggs at low concentrations, butcannot be detected at higher concentrations becauseit overpowers the sense of smell. High concentrationscan be released by agitation and pumping. H2S is themost toxic gas associated with manure storage, beingboth an irritant and asphyxiant. It is also flammable.Low concentrations severely irritate the eyes andrespiratory tract of humans within an hour. Concen-trations of 0.1 percent cause immediate unconscious-ness and death through respiratory paralysis. Animalsliving continuously in facilities where the level of H2Sis 0.002 percent develop nervousness, appetite loss,and fear of light. Concentrations at 0.005 to 0.02percent can cause vomiting, nausea, and diarrhea.

    Methane (CH4)Methane is an odorless gas pro-duced by anaerobic decomposition of organic wastes.It is not normally considered a toxic gas; however, it ishighly explosive when mixed with air in concentra-tions as low as 5 percent. Lighter than air, methanetends to accumulate near the top of stagnant cornersof buildings or covered manure impoundments. Accu-mulations of methane can be asphyxiating to bothhumans and animals; however, explosions are a moreserious concern.

    Carbon monoxide (CO)Carbon monoxide gases inan AWMS result from operation of internal combus-tion engines and from gas, oil, and coal heaters ratherthan the decomposition of organic wastes. CO ismentioned because it is generated by equipment usedin the operation of an AWMS. It is a colorless, odor-less, toxic gas that can cause drowsiness at low con-centrations and death at high concentrations.

    (2) Gas hazard situation categoriesGases generated by an AWMS can be lethal if ventila-tion systems break down, during agitation of waste,and in poorly ventilated confined spaces, such asmanure tanks including those that are uncovered. Thehazards to both humans and animals include death,incapacitation, impairment of the ability to self rescue,or acute illness. A hazardous atmosphere occurs whenflammable gases and vapors reach their flammablelimit, when oxygen concentration is below 19.5 per-cent or above 23.5 percent, and when concentration oftoxic gases exceeds permissible exposure limits. The

    AWMS plan should address these hazards and how toappropriately remediate or improve them. It is impor-tant that others, such as family members, who mayfrequent an AWMS be aware of the hazards of thesesituations as well.

    Ventilation breakdownsVentilation depends onproperly operating fans or vents. With no naturaldrafts to replenish the air in confined areas, death byasphyxiation from lack of oxygen and increased car-bon dioxide, by poisoning from other gases, or bysome combination of these can occur. Operators mustbe alert to failure of ventilation systems and takeimmediate action to either repair the system or acti-vate a backup system until repairs can be made. Op-erators must also be aware of the dire consequencesof purposely blocking ventilation systems, which maybe considered during cold weather to reduce heat loss.

    AgitationAgitation of wastes to facilitate transferand other waste management functions is a commonpractice in an AWMS. This activity may release largequantities of noxious gases and create dangerous andpossible lethal conditions even with maximum ventila-tions. If agitation is done outdoors, it seldom is aproblem; however, lethal conditions are a potentialwhen it is done within buildings. To minimize thehazards, agitation should be done on mild days so thebuilding can be ventilated to full capacity. For natu-rally ventilated buildings, it is best done on windydays. Animals should be removed from the buildingbefore the agitation is started, but if they are notremoved, they should be observed for signs of illeffects.

    Confined spaceDeath resulting from personsentering a covered waste storage tank or other con-fined space in an AWMS occurs all too often in theUnited States. Multiple deaths frequently occur whenthe first person to enter the confined space and thewould-be rescuers all succumb to the atmosphere ofthe facility. These are tragic occurrences, and everysafety precaution should be used to prevent them.

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    Often a person enters a tank as a spur-of-the-momentreaction to the desperate need for assistance to ananimal or person who has accidentally fallen into thefacility. Steps can be taken to avoid this type of acci-dent. First, the AWMS design should include, and itsplan should indicate, maintenance of such devices asgrates and covers that prevent accidental entry fromhappening. Design consideration should also be givento:

    Features that minimize the need for confinedspace entry.

    Provisions that allow for maintenance of equip-ment outside the space or for equipment partsthat can be easily retracted for maintenance.

    Corrosion resistant equipment that performswith minimum maintenance in caustic environ-ments.

    Power ventilation systems that provide for botha supply of fresh air and exhaust of accumu-lated gases.

    Secondly, the people who operate or frequent anAWMS must be made aware of the absolute rule thatno one enters these facilities under any circumstanceunless preparations have been made for their safeentry. Signs (fig. 135) should be prominently postedand maintained that warn of the hazard. Children andthose that cannot read must be given special instruc-tion to assure that they are aware of the hazard.

    Entry into a confined space is sometimes necessary.Examples include:

    To inspect a tank for cracks and leaks. To rescue someone or something.

    Confined spaces should, however, only be enteredafter preparations have been made for a safe entry.For this reason, the AWMS plan needs to address safeentry into confined spaces.

    Some States may regulate entry into confined spacesfor agricultural operations. The appropriate occupa-tional and safety agency should be contacted to deter-mine what the requirements are. The U.S. Departmentof Labor, Occupational Safety and Health Administra-tion, has rules and regulations on entering confinedspaces (Federal Register 1993). The regulatory aspectsof these rules do not apply to agriculture. However,from a safety standpoint these rules should be fol-lowed to ensure the safety of persons required to enterhazardous confined spaces. Following is a summary ofthe practical aspects of these rules as they apply toentry of AWMS confined spaces:

    Any condition making it unsafe to remove anentrance cover to a confined space shall beeliminated before the cover is removed.

    When entrance covers are removed, the open-ing shall be promptly guarded by a railing,temporary cover, or other temporary barrierthat will prevent an accidental fall through theopening and will protect persons working inthe space from objects entering the space.

    Before a person enters the space, the internalatmosphere shall be tested with a calibrateddirect-reading instrument for the followingconditions in the order given:1. Oxygen content2. Flammable gases and vapors3. Potential toxic air contaminants

    Figure 135 Confined space warning signs






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    No hazardous atmosphere can be within thespace whenever any person is inside the space.

    Continuous forced air ventilation shall be usedas follows: A person may not enter the space until the

    forced air ventilation has eliminated anyhazardous atmosphere.

    The forced air ventilation shall be so di-rected as to ventilate the immediate areaswhere a person is or will be present withinthe space and shall continue until all personshave left the space.

    The air supply for the forced air ventilationshall be from a clean source and may notincrease the hazards in the space.

    No one should enter a confined space without aqualified safety watcher stationed outside thespace. Persons entering confined space shouldknow the hazards that may be faced duringentry, be equipped with a full body harnesswith a retrieval line attached to a mechanicalrescue device, and be able to communicatewith a safety watcher. The safety watcher mustbe able to communicate with those inside thespace and be able to perform the actions re-quired to retrieve those inside the space.

    The atmosphere within the space shall beperiodically tested as necessary to ensure thatthe continuous forced air ventilation is prevent-ing accumulation of a hazardous atmosphere.

    If a hazardous atmosphere is detected duringentry: Each person shall leave the space immedi-

    ately. The space shall be evaluated to determine

    how the hazardous atmosphere developed. Measures shall be implemented to protect

    persons from the hazardous atmospherebefore any subsequent entry takes place.

    To fully implement the above procedure, the AWMSplan should recommend employing a safety profes-sional who has the training and the testing equipmentnecessary to ensure a safe confined space entry. Localor State Government safety agencies may provide thisservice upon request. Some States require insurancecompanies that supply coverage for occupationalaccidents to provide their clients with consultationservices on safety related problems.

    A well thought-out plan of action for dealing withemergencies involving accidental entry into confinedspaces needs to be included in the AWMS plan. Theplan should recommend that the decisionmaker edu-cate all who are involved in the operation of an AWMSin carrying out the plan. An AWMS plan should:

    Include a rescue service that could be calledfor assistance in an emergency.

    Suggest that equipment needed for emergencyrescue, such as self contained breathing appa-ratus, life lines, and harnesses, be close athand.

    Address the specific hazards from gases ineach of the applicable functions of the AWMS.

    Safety equipment used in confined space is describedin chapter 12.

    (b) Hazards with impoundments

    Impoundment type components, such as waste storageponds, waste treatment lagoons, and waste storagetanks, present a drowning hazard. The hazard forearthen waste impoundments is similar to that associ-ated with any farm pond. However, crusts that mayform on the water surface and slime formation makewaste impoundments more hazardous.

    Crusts have the appearance that they would support apersons weight; however, they often will not. Theconsequence of falling through the crust on a wasteimpoundment would be similar to falling through theice on a pondthere is no escape. Slime that forms onthe surface of impoundments makes them very slip-pery, and as such makes it easy for a person to loosetheir footing on inclines. In cold climates, ice forma-tion can make any surface unsafe. Geotextile liners aregenerally smooth, and when wet they are so slippery afoothold cannot be achieved.

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    The best approach to minimizing the hazards ofdrowning in waste impoundments is to include fea-tures in the design to exclude both animals and people(fig. 136). This can be accomplished with fences andwarning signs. Gates should be locked to limit accessexcept to those who need to enter the impoundmentarea. Provision needs to be provided for emergencyexit in case someone accidentally enters these areas.Prominent signs indicating the hazard should bedisplayed. The AWMS plan needs to emphasize theimportance of maintaining these safety features.

    On some occasions, personnel must operate nearthese impoundments. The AWMS plan should recom-mend that life rings, life lines, poles, and boats beclose at hand to assist in making a rescue.

    Design of push-off ramps should include: Sturdy guard rails to prevent people and equip-

    ment from falling into waste impoundments. Loading ramps with a traction surface to mini-

    mize slipping. Walkways constructed of nonslip surfaces.

    People can do little to escape if they fall into a storagetank with vertical walls. The side of the tank is slickand has nothing to hang onto unless it is provided. Forthis reason tank access should be limited to those whohave need for entry. A ladder on the outside of thetank should terminate above the reach of people orshould have locked entry guards.

    Figure 136 Waste storage pond safety features

    Life ring withattached rope

    Locked gate

    Warning sign

    Fence to excludechildren and animals

    Unloading ramp withnon-skid surface


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    Some tanks have platforms for such equipment assolid/liquid separators and pumps. The platformshould be equipped with guard rails to prevent acci-dental falls into the tank. A rope dangling from theplatform would allow improved opportunity forsurvival from an accidental fall from the platform intothe tank.

    Providing a means of survival from accidental entryshould also be considered for below-ground tanks;however, whatever is done should never invite entry.Examples of things to consider include:

    A ladder hinged to the tank cover that can bepulled down with a rope to allow escape.

    Perches installed on the tank floor or wall thata person can stand on to attain fresh air andcall for help.

    The AWMS plan should discuss the specific hazards ofimpoundments in each applicable function. Generally,this hazard would be discussed in an AWMS plan forsystems that have waste storage ponds or tanks in thestorage function and for systems that have wastetreatment lagoons in the treatment function. Seechapter 12, section 651.1204, for additional informa-tion on safety equipment for impoundments.

    (c) Hazards in equipmentoperation

    Equipment used in an AWMS is varied. Chapter 12,Waste Management Equipment, describes equipmentused in an AWMS, as well as safety aspects of equip-ment operation. A few guiding principles in the safeoperation of equipment should be included in theAWMS plan. Safety procedures should also be in-cluded. The procedures could include:

    Assuring that moving parts that would exposean operator to injury are properly guarded.

    Providing and using backup signals on equip-ment as appropriate.

    Maintaining electrical equipment and assuringthat it is properly grounded.

    Perhaps the most important safety precaution is assur-ing the equipment operators are trained in the safe useof the equipment before being allowed to operate it.

    This should be recommended in the AWMS plan. It isequally important that operators only be allowed touse equipment when they are well rested and notunder the influence of a drug, prescribed or otherwise,which would impair their ability to operate the equip-ment safely.

    The decisionmaker should be advised in the AWMSplan of the necessity of requiring workers to usepersonal protective equipment when appropriate (fig.137). Rollover protective structures and seat beltsshould be on all equipment that is ridden. Safety beltsshould be used if there is a potential of falling.

    Because many surfaces in an AWMS are slippery,shoes or boots with soles having good traction shouldbe used. Hearing protection should be used if the noiselevel and duration would contribute to hearing loss.Operators should use eye and face protection if ma-chines or operations present potential eye or faceinjury. Work areas should be well ventilated. If theyare not, workers should use appropriate respiratoryprotection. Proper lighting is also important in provid-ing a safe work environment.

    The AWMS plan should discuss the specific hazards ofthe equipment used in each function of the AWMS.

    Hard hat Safety gloves

    Hearing protection


    Safety goggles

    Figure 137 Personal safety equipment

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    651.1304 Agriculturalwaste management systemplans

    The purpose of an AWMS plan is to convey to thedecisionmaker details of the construction and O&Mrequirements of the system. It is important to remem-ber this in its preparation. As such, the plan shouldhave an easily followed format, use familiar terms, andbe concise. It should be neat, invite reading, and beworthy of retention. Presenting the plan to the deci-sionmaker in a 3-ring binder encourages retention. Anelectronic copy could be provided those decisionmak-ers having computers. See Chapter 2, Planning Consid-erations, and Chapter 9, Agricultural Waste Manage-ment Systems, for more information on the AWMSplan.

    The preparation of the AWMS plan requires input fromall disciplines involved in the planning and design ofthe system. Information from the AWMSs planningdocumentation must be extracted for inclusion in theplan. This would include information extracted frominventories, investigation reports, alternatives consid-ered, design reports, installation schedules, and otherinformation that is necessary for explaining the systemrequirements. However, it is generally not appropriateto include the planning and design documents in theirentirety.

    An AWMS component design report should be re-viewed to ascertain O&M activities that may have beenidentified as necessary for the components perfor-mance. These O&M activities should be included in theO&M plan. The plan should include maps, charts, andother illustrative aids that enhance understanding ofthe systems O&M requirements. Appendix C is anexample AWMS plan for a simple agricultural wastemanagement system. A suggested format follows.

    Name, address, and location of AWMSThis isself-explanatory.

    General statementShould indicate the purpose ofthe AWMS and the importance of O&M.

    General description of AWMSShould include thetype and size of operation and the basic componentsof the AWMS. Including a plan view drawing of thecomponent layout would be helpful for describing theAWMS.

    Decisionmakers responsibilitiesIt is suggestedthat this section clearly state that proper and safesystem operation and maintenance within the lawsand regulations are the responsibility of the decision-maker.

    Component installation scheduleShould con-sider proper sequence of installation so that eachcomponent will function as intended in the system.

    Operation and Maintenance of production, col-lection, storage, treatment, transfer, and utiliza-tion functions The specific O&M requirements foreach function of the AWMS should follow the compo-nent installation schedule section. These requirementsshould expand on the general O&M considerationsdescribed in this chapter and include the appropriatesafety requirements.

    Decisionmakers acknowledgmentThis lastsection is intended to include a signature line allowingthe decisionmaker to attest to having read and under-stood the plan.

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    651.1305 References

    Federal Register. 1993. Part II, Department of Labor,Occupational safety and health administration,29 CFR Parts 1910, Permit-required confinedspaces for general industry; final rules (Jan. 14).

    Midwest Plan Service. 1985. Livestock facilities hand-book. MWPS-18, Iowa State University.

    Oregon Department of Insurance and Finance, OregonOccupational Safety and Health Division. 1989.Oregon occupational safety and health code,Oregon administrative rules, ch. 437, Div. 81,Agricultural Operations and Farming.

    Renner, Donald C. 1993. Establishing a maintenanceprogram. Water/Engin. & Manage. (Feb.)

    United States Department of Agriculture. 1991. Penn-sylvania manure storage studyFinal report.Soil Conserv. Serv., Harrisburg, PA.

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