APPCOR11234 - Laserfiche WebLink

Home Browse Search

^. 3b tit: UTAf 1: N~r1'UNIRUL IIiCHNtOU Fti, C'EN rN AL PENNtiVI-\'ANtA of the soil used in the construction, the concentration of sediment in the runoff walcr, and the particle-size distribution of the sediment in the runoff water. The efficiency of devices for which data are not avail;tblc is also discussed. OFFSTNEAAI PONDS D 0 Three offstream ponds were constructed in basin 2A. Each pond was designed to trap about 0.50 in. (13 mm) of runoff from the contributing construction area. Generally a I.00 in. (25.4 mm) storm would produce 0.5 in. (13 mm) of runoff. Figure 21 is a sketch map of basin 2A showing the main features. A separate culvert system was used ill connection with e:tclt of the offstream ponds. Each culvert system collected drainage from the constrttc- ~ `. '~~ /.. ~.. S70 1000 IFFi ` ._ , /~' 'iTi ~''~. ~..-.. 100 700 Om Mn[0.5 µpmimalr nq EXPLANATION l:orotruNon arY ® Cut area - ~-~ ~ Baeln boundary ® Fill arse Q, Stream paging sits Q Cleared arse FIGIIaL 21.~-Location of the construction area, the o(Isl ream sedimenl.cuntrol ponds, and the stream-gaging silt in basin 2A. . ~.. ~ . .. .^a ~.. ~.. FROtiION AND ofDIMGN"I~-CUNI'HUI. h11S\Slllt l:S lion area and discharged it directly to the sediment ponds. An ;tdJititln:t system was used to carry the normal streamflow from the upstream dminagt area through the construction site. Construction of the ponds began in Jum 1973 and was completed in October 1973. The three offstream ponds, constructed in basin 2A, can be seen in ligtt« 22. The west pond received runoff from 4 acres (1.6 ha) of the consinlcuon area and a 6 acre (2.4 ha) field. Runoff from an area of shout 5 acres (2.11 ha drained into the center pond. The east pond received drainage from an arc, o(about 8 acres (3.2 ha). Inflow to the center and east ponds was entirely from the construction area. Figure 23 shows the center and cast offstream ponds as viewed from the west side of the construction area. Ilccausc the west pond w;ls located in a low area, it .vas opcr;uitmal lium the time it was completed In October 1973. The center and east ponds were located to receive drainage from culvert outlets (figs. 21, 2]), and they u•c« not fully operational until 1974 when the culvert systems were completed. Diversion ditches directed runoff water into the center and east pond> from the time they were constructed until the drainage structures were completed. The offstream ponds intercepted the sediment-laden runoff from tltc construction area. Water remaining in the pond since the last storm would, in theory, be displaced by the incoming sediment-laden water. If the water displaced from the pond was sediment free, the pond would have a tr:tp efficiency of 100 percent. As sediment-laden water continued to he discharged into the ponds from the construction area an efficiency of less a; it ..`i~; ... -•~ ...N~: i]e..~ 1: Y.TI .. n~ .... ."r,Yu .~.. tuUvt+wN JP~I ~.. ~~~r M1 - t ~1~?fi,~,t« S ~~t~a-;~,RR.~`~~~~~.~}~{{it~nhq.~~1fr''~ffpp~JJ~+.~.L.. I`.I~,..i,l"~'F'•' _.~ :~~y~~.~.,~7~}'~I~'T::~'1~~:!t~~Ik~.~~IN'~t~,"{jr1'~'i`II, 1l, yt'1'.1}:ti ~ ~ I ,~`e I V L~ v,i ~~,.IIia1~~11. ~i+~Yl .~,n ,~.~ y 7 7! • t. ~.. .1 1 .' I . .. .,,.+L a ,. e'~. ~. ~ ~ , fl' oe_ _ ' Fleuae 27.-~l~hc west, ttntcr, anJ u1sl ulletl nlm pmu6 iu h,1,in 7A, luly I I, I'll J,