Low Impact Development Manual for Michigan - OSEH - University ...

the tank can accommodate.) (www.starkenvironmental.
com/downloads/Interface_Engineering.pdf) That level
of capture would yield approximately 500 gallons per
inch of rain per 1000 SF of capture area. Table 7.7
includes available capture volumes based on drainage
area and annual rainfall.
Peak rate mitigation
Overall, capture and reuse takes a volume of water out
of site runoff and puts it back into the ground. This
reduction in volume will translate to a lower overall
peak rate for the site.
Water quality improvement
Pollutant removal takes place through filtration of recycled
primary storage, and/or natural filtration through
soil and vegetation for overflow discharge. Quantifying
pollutant removal will depend on design. Sedimentation
Table 7.7
Annual rainfall yield (in gallons) for impervious surfaces
Annual Rainfall Yield in Gallons for Various Impervious Surface Sizes and Rainfall Amounts
Impervious
Surface Area (sf)
will depend on the area below the outlet that is designed
for sediment accumulation, time in storage, and maintenance
frequency. Filtration through soil will depend on
flow draining to an area of soil, the type of soil (infiltration
capacity), and design specifics (stone bed, etc.).
Maintenance
Rain barrels
• Inspect rain barrels four times per year, and after
major storm events.
• Remove debris from screen as needed.
• Replace screens, spigots, downspouts, and leaders
as needed.
• To avoid damage, drain container prior to winter, so
that water is not allowed to freeze in devices.
Rainfall (inches)
26 28 30 32 34 36 38 40
200 3,079 3,316 3,553 3,790 4,027 4,264 4,501 4,738
400 6,159 6,633 7,106 7,580 8,054 8,528 9,002 9,475
600 9,238 9,949 10,660 11,370 12,081 12,792 13,502 14,213
800 12,318 13,265 14,213 15,160 16,108 17,056 18,003 18,951
1,000 15,397 16,582 17,766 18,951 20,135 21,319 22,504 23,688
1,200 18,477 19,898 21,319 22,741 24,162 25,583 27,005 28,426
1,400 21,556 23,214 24,873 26,531 28,189 29,847 31,505 33,164
1,600 24,636 26,531 28,426 30,321 32,216 34,111 36,006 37,901
1,800 27,715 29,847 31,979 34,111 36,243 38,375 40,507 42,639
2,000 30,795 33,164 35,532 37,901 40,270 42,639 45,008 47,377
2,200 33,874 36,480 39,086 41,691 44,297 46,903 49,508 52,114
2,400 36,954 39,796 42,639 45,481 48,324 51,167 54,009 56,852
2,600 40,033 43,113 46,192 49,272 52,351 55,431 58,510 61,589
2,800 43,113 46,429 49,745 53,062 56,378 59,694 63,011 66,327
3,000 46,192 49,745 53,299 56,852 60,405 63,958 67,512 71,065
3,200 49,272 53,062 56,852 60,642 64,432 68,222 72,012 75,802
3,400 52,351 56,378 60,405 64,432 68,459 72,486 76,513 80,540
3,600 55,431 59,694 63,958 68,222 72,486 76,750 81,014 85,278
3,800 58,510 63,011 67,512 72,012 76,513 81,014 85,515 90,015
* Values represent the following percentage of precipitation (i.e., runoff coefficient) to account for losses: 95%
LID Manual for Michigan – Chapter 7 Page 154