04-13-2005 Council Agenda - Laserfiche WebLink

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APPARATUS To conduct the tests a huge cylindrical flooding tank was constructed. (Sec Figure 21. The tank h..ci an inside diameter of 3ci%", was 15" deep and was equipped, with a 3" diameter outlet pipe which pro- truded from the i?otb-nn center Cf the tank. A lubber coated wooden plug ryas used as the stopper for this outlet. The tank was supported about 3 feet above the Boor by four legs to accommodate an 18" x 3ti' x 15" deep receiving tank. To facilitate measurement of the inflow water collected in the tank after each triad, the receiving tank was equipped with casters which allowed it to he rolled out from under the flooding, took. The manhole frames were bolted to the bottom: of the test tank, using a Hat rubber gasket as 0 seal. This pro- vided a watertight joint between the tank and man- hole frame, Water would then be introduced into the flooding tank by hose, filling it to the desired head. Figure 2 Flooding Tank PROCEDURES rith the receiving tank empty and the outlet plugged, the test could begin at the time water began to How through the top of the manhole cover. Duration of the test was one minute by stop watch and the water was allowed to flow into the receiving tank below. After one minute the outlet vas ?lugged so no additional water could enter the receiving tank. The water col- lected in the receiving tank 'vas then me.uured with :. point gauge and recorded as the amount :if iniow that the particular manhole !id would allow to cater dur- int; the >00 mine :c timc i)erioci. There are basically two locations in manhole lids through which surface n.mnoff can enter the manhole lid. One is by direct passage through open pick and vent holes, and the other is by seepage through the manhole lid and frame contact (bearing) surface along the Perimeter of the manhole frame and lid. Ail of these sources would be affected directly by in- creased water head. In addition, the hearing surface itself will permit varying amounts of inflow depending on the quality of the scaling surfaces and whether that ~unite is ground or commercially machined. In order to more closely evacuate. what part of the total manhole inflow can be associated with the bear- ing surface and vent and pickhole areas, the testing was set up to test each source separately. To test for bearing surface inflow, solid manhole covers containing concealed pickholes were used. Five different sized manhole cover assemblies detailed in Appendix C and ranging in size from 22" to 26" in diameter were tested, first with a ground hearing sur- face and then these same sizes were again tested with a machined finish bearing surface. To overcome the variations expected hum one set of castings to another, a total of 136 different casting sets were randomly selected from the Neenah Foundry stock. Over 2000 individual tests were conducted and averaged into 441 categorized separate data points, reproduced in Appendix D of this report. To test for piekhole and vcnthole inflow, manhole lids were sealed to the frames to make watertight bearing surfaces. Each lid contained one hole either %", 1 ", 1fl", 1r or 2" in diameter. Ten trials were run for each hole diameter to determine average values for plotting as shown in Appendix E. Three water head conditions were simulated for each lid to reflect basic runoff situations for both bearing surface and vent and pick hole tests. They are: Test 1: Splashing water on lid simulating steady rainfall with no pending. Test 2: Water on cover allowed to accumulate to k" head. 'Pest Runoff simulation allowed to pond to a 1" head. No attempt was made to `fntroduce dirt, debris, sand or silt into the clear .eater or manhole lid and :'Prne hearing surfaces and holes. 4