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American Tunnel Bulkhead <br /> Page 3 <br /> Total Perimeter area of rock irregularity = £PIn D <br /> where PIn = Perimeter of section n that has a surface <br /> within the area from section n + 1 when <br /> overlaying section n ( ft) <br /> D = distance between section n and section n + 1 <br /> (ft) <br /> This gave a Total Perimeter area of rock irregularity for <br /> the bulkhead of 600. 7 sq. f t. <br /> The percentage of intact rock perimeter area irregularity <br /> calculated by this estimation is 52% which is larger than the <br /> required 10% and therefore a more detailed measurement and analysis <br /> is not required . <br /> It is anticipated that this bulkhead will be poured during the week <br /> of July 4, 1995 pending availability of the concrete batch plant. <br /> I will contact you with a firmer date when more information becomes <br /> available concerning the batch plant' s schedule so you can schedule <br /> your pre-pour inspection the day before the pour . The bulkhead <br /> forms will basically be ready for a complete inspection by June 23 , <br /> 1995. <br /> The prepour flow measurements are being taken daily. The flow <br /> measurements (through June 16, 1995) range from 925 GPM to 2310 + <br /> GPM. This wide range is due to the Terry Tunnel bulkhead diverting <br /> part of the flow that normally exits the Terry Tunnel to the <br /> American Tunnel level. To date this increased flow has not <br /> bothered form construction nor is it expected to. The coffer dam <br /> was constructed lg foot high giving an 8 foot available head to <br /> force water through the 12 inch diversion pipe. This should be <br /> adequate to handle flows in the 4000 - 4400 GPM range without any <br /> pressure against the back wall of the bulkhead although, there <br /> might be some backup from the air-side of the bulkhead (discharge <br /> pipe) if this quantity is reached. <br /> The weir installed in the American Tunnel has a capacity of 2310 <br /> GPM. It is not possible to install one with a larger capacity <br /> without backing water over the tracks. Therefore, SGC requests <br /> that the flow measurement submittal requirement be a combination of <br /> visual observation (DMG' s) , weir readings plus by-pass estimates <br /> (if any) in the American Tunnel and water balance information based <br /> on outside American Tunnel flows less historic lower American <br /> Tunnel flows and certification that the bulkhead was not exposed to <br /> damaging flows. <br />