Design Guide for Community Water Systems - The Water, Sanitation ...

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parameters: average winter (December, January, February) daily flow intoand out of the tank; winter diurnal flow pattern into and out of the tank;water temperature into the tank under the winter design conditions; heattransfer between the water layer and air layer in the tank; heat transfer ratethrough the tank wall and any insulating layer; heat transfer from theoutside tank surface to the atmosphere based on wind speed and airtemperature from the winter design conditions; solar energy input to thetank during daylight under the winter design conditions; and radiation heatloss from the tank to the sky during night time under winter designconditions. If winter design conditions are not available, a reasonablyconservative estimate can be made using the high and low temperaturefrom the record low temperature day from the nearest U. S. weatherstation with 100 years of record for one of the seven days, using theaverage coldest winter day from the nearest U. S. Weather station with100 years of record for the other six days, using sunrise/sunset times andsun angle for the seven days centered on the winter solstice, using averagewind speed for December – February from the nearest U. S. Weatherstation with 100 years of record, and assuming 50% cloud cover for skyconditions. This energy balance should be used to set the winter tankturnover rate, winter pump ON/pump OFF elevations, inlet and outletdesigns to ensure mixing to minimize ice formation, insulationrequirements (if appropriate) and heater requirements (if appropriate).c. The tank should be designed to turn over a sufficient percentage of thestored water daily to minimize aesthetic water quality problems. Thispercentage may vary with local condition, but a 25% daily turnover issuggested as a default value. Note that additional turnover may berequired for winter operations to minimize freezing. Separate inlet andoutlet lines should be provided.7.0.3. Locationa. The bottom of reservoirs and standpipes and footings for elevated tanksshall be above the 100 year return frequency flood level and shall beabove the highest known historic flood elevation. Top of footings forelevated tanks shall be at least one foot above the finished grade.b. The bottom of reservoirs and standpipes and footings for elevated tanksshall be above the true ground water level.c. The bottom of reservoirs and standpipes should be placed above thenormal ground surface. When the bottom must be placed below groundsurface, sewers, drains, standing water and similar sources ofcontamination must be kept at least 50 feet from the reservoir except thatspecially constructed gravity sewers may be located no closer than 20 feetfrom the reservoir. These specially constructed gravity sewers shall bemade of water main pipe pressure tested in place to 50 psig pressurewithout leakage. The top of the reservoirs shall not be less than two feetabove the normal ground surface except that clear wells under filters mayAug. 29, 2003Page 134
e exempted when the total design gives the same protection. The areasurrounding a ground level structure shall be graded in a manner that willprevent surface water from standing within 50 feet of it. Steel storagetanks shall not be located below the ground surface.7.0.4. Roofs on Unpressurized Finished Water Storage StructuresAll unpressurized finished water storage structures shall have suitablewatertight roofs that prevent entrance of birds, animals, insects, and excessivedust. The roof shall be well drained. Downspouts shall not enter or passthrough the storage structure.7.0.5. Protection of Finished Water Storage StructuresAll finished water storage structures shall be protected from trespassing,vandalism, and sabotage. Protection shall include at least the following:a. Locked hatches and other access openings;b. Physical barriers to entrance of ladders; andc. Security fencing with locked gates.See also section 2.5, Security Measures.7.0.6. Vents on Unpressurized Finished Water Storage StructuresAll unpressurized finished water storage structures shall be vented.Overflows shall not be considered vents. Open construction between thesidewall and roof is not permissible. Vents shall meet the following criteria:a. Vents shall be sized with sufficient capacity to pass air so that themaximum flow of water entering or leaving the tank will not causeexcessive pressure or vacuum. Maximum flow of water leaving the tankshall include the rate produced by a catastrophic large main failure nearthe tank. Resistance of air flow caused by the vent screens shall beconsidered in sizing the vents;b. Vents shall be designed to exclude precipitation, shall be screened toexclude birds, insects, and animals and shall terminate a minimum of 24inches above the roof. Eighteen mesh noncorrodible screen may be used.The finished water storage structure shall also be equipped with apressure-vacuum relief mechanism that will operate should the finer meshscreens be frost plugged or clogged with foreign material. The primarypurpose of the vents is to prevent catastrophic structural failure of the tankcaused by pressure differential. No modifications shall be made to ventsto interfere with this primary purpose; andc. Clearwell vents shall vent to the outside.7.0.7. Overflows on Unpressurized Finished Water Storage StructuresAll unpressurized finished water storage structures shall be provided with anoverflow. Overflows shall meet the following criteria:Aug. 29, 2003Page 135
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Design GuideforCommunity Water Syst
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2.18. AUTOMATION. .................
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4.3.11. Waste Disposal. ...........
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CHAPTER 6 -- MINIMUM CONSTRUCTION R
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Maximum Hour Demand -- The amount o
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(This page is intentionally blank.)
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and deviations are subject to indiv
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(blank)Aug. 29, 2003Page viii
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a. A description of the nature and
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a. Hydrological data, stream flow,
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4. Be conducted under the same oper
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maintaining the new technology and
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1.2.1. Plans shall include:a. Suita
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name, number, effective date, publi
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e. The site will provide all-weathe
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chlorine residual by methods in "St
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etween them, a six-inch band of con
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a. Regulated recreational activitie
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e done to determine the degree and
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1. Pumping rate;2. Pumping water le
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sieve analyses of the water bearing
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e circulated in the annular space s
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emoved. Therefore, every well shoul
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3.2.6.4. Pitless well units.a. The
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SIZE (inches)6 id.8101214 od.161820
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Chapter 4 -- Tre atment4.0. General
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settling basins shall be not less t
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3. Shall have valves located outsid
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d. Be automatic. Timers on automati
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2. Uniformity coefficient not great
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j. During air scour, the backwash w
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. An easily readable meter or flow
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4.3.4. Design Pressure Drop or Tran
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4.3.9. Flow Meters.Totaling rate of
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utilized, shall be 1.0 milligrams p
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. Removal of precursors prior to ch
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5. Consideration shall be given to
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. Pre-treatment requirements. Iron,
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t. Housing. Bagged salt and dry bul
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4.7. Iron and Manganese ControlIron
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Where phosphate treatment is used,
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3. Series and parallel flow piping
Page 102 and 103: approval of the department before u
Page 104 and 105: contact time must be provided to co
Page 106 and 107: a. Sanitary sewers with the approva
Page 108 and 109: 1. Obtain a letter of approval from
Page 110 and 111: 6. The provisions for the final dis
Page 112 and 113: a. Missouri River or Mississippi Ri
Page 114 and 115: 5.0.3. General equipment design.Gen
Page 116 and 117: minimize chemical dust created by t
Page 118 and 119: 1. At least 30 days of chemical sup
Page 120 and 121: e. Hand pumps shall be provided for
Page 122 and 123: 5.2. Chemicals.5.2.1 Shipping conta
Page 124 and 125: outside atmosphere, above grade and
Page 126 and 127: 5.4.2. Acids.a. Acids shall be kept
Page 128 and 129: 4. Anhydrous ammonia contact with c
Page 130 and 131: combustible material.2. Powdered ac
Page 132 and 133: fluoride feed line when a metering
Page 134 and 135: possibility for overfeed.h. Protect
Page 136 and 137: caution.d. Where taste and odor con
Page 138 and 139: e installed to monitor the flow of
Page 140 and 141: the generator dielectrics. Sufficie
Page 142 and 143: published by the National Fire Prot
Page 144 and 145: g. Water from pump gland drainage s
Page 146 and 147: 6.3. Pumps.6.3.1.Pumps shall be siz
Page 148 and 149: 6.4.2.2. Suction lines.Suction line
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Page 154 and 155: a. Overflows shall be sized to perm
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Page 158 and 159: largest pump out of service shall b
Page 160 and 161: 7.1.4. CostsAs part of the final en
Page 162 and 163: 7.4. Hydropneumatic Storage7.4.1. H
Page 164 and 165: provided on larger tanks as needed
Page 166 and 167: 7.5.2. Fire Suppression Rating Sche
Page 168 and 169: in areas served by rural water dist
Page 170 and 171: connected directly to any sewer. Su
Page 172 and 173: 8.6.5. Force mains.There shall be a
Page 174: 8.11.2. Filling device.A filling de
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