Laserfiche WebLink
Exhibit 19 (16) <br />PROTECTION OF THE HYDROLOGIC BALANCE <br />BATES PORTAL & SUBSOIL & TOPSOIL STOCKPILES #1 <br />• <br />Notes for Calculations: <br />1. Pages 2 through 4 present a spread sheet calculation of the incremental increase in the <br />runoff volume for the Bates Portal based on the 10 year -24 hour event. It is assumed the <br />flow from the Bates Portal area (prior to disturbance) was accounted for in the slang of Pond <br />007. Therefore, the disturbance and resulting flow created by TR -55 is an incremental flow <br />increase. The calculation is based on the difference between the flow from the undisturbed <br />and the disturbed area applied to the increase is disturbed area (1.57 acres). <br />2. At the Bates Portal and SAE for Subsoil Stockpile #1, for continuity, curve numbers of 94 for <br />newly graded areas and 89 for disturbed areas were used based on Exhibit 19(15) unless <br />otherwise noted. <br />3. Design Points for the Bates Portal are shown on Map 13 -A and discussed in Section <br />2.05.3(4). <br />4. Peak flow for ditches and culverts were calculated with SedCad 4.0. All new ditches have <br />minimum freeboard of 0.3 feet. It is assumed all ditches, except D -24C and D- 24 -C4, are cut <br />into bedrock and therefore rip rap has not been evaluated. <br />5. Sediment yield (incremental volume) was calculated using the Universal Soil Loss Equation <br />(USLE), as shown on page 4 for the Bates Portal. <br />6. The design for Ditch 26 is based on vegetation and soils data as found in Exhibits 15 and 14 <br />respectively. Curve number is based on Table 2 -2d - Runoff curve numbers for avid and <br />semi -arid rangelands. The soil type is D, and cover type is Pinon- Juniper with a 'Good' <br />hydrologic condition, yielding a curve number equal to 71. Runoff is calculated based on the <br />10 -year 24 -hour event, precipitation equal to 3.0 ". A design is included for the dirt portion of <br />the channel, and the concrete box portion of the channel. <br />7. The increased runoff from the Bates Portal disturbance has been added to pond 007 and <br />pond 007 has adequate capacity for the increased runoff. However, downstream culverts <br />and ditches have not been evaluated for capacity. <br />8. The SAE for Subsoil Stockpile and Topsoil Stockpile #1 requires the construction of a 2.5 <br />foot high berm around the area and installing silt fences in the low points. The SAE <br />demonstration on pages Exh.19(16) -25 through 31 shows that 26 feet of silt fence will result <br />run-off from the area with a peak settable concentration of less than 0.5 mill. The SAE is <br />shown on Maps 11 & 12. <br />ENGINEER'S CERTIFICATION <br />The calculations and information <br />03/11 were prepared by m <br />and the information pres <br />Tamm <br />State of <br />• <br />TR -55 <br />on pages Exh.19(16) -2 through 31 with a date of and <br />.rvision during the months of January and March 2011, <br />krrect to the best of my knowledge and belief. <br />' /2s/ I <br />Date <br />EXH.19(16) -1 <br />03/11 <br />_::�..;� r ...�: -a �swa' at��, te.,.. sevc. ssiw,• a�.` � ..'uYa '�.,rR,t�'&�+�w_;*ia1s�,� �., <br />