It’s a very busy week for environmental professionals.  Thus, I thought I would put out a reminder about the 2 year, 24-hour storm event stormwater inspections which will be required at some facilities in Louisville this week.  If your facility has coverage under the Kentucky Pollutant Discharge Elimination System (KPDES) General Permit for Stormwater Discharges Associated with Industrial Activity (KYR00) or another permit with a 2 year, 24-hour inspection requirement and your facility experienced a 2 year, 24-hour or more storm event this week, a special inspection is required.  Refer to section 3.10 of KYR00 or your permit for more details.

If you aren’t sure about what constitutes 2 year, 24-hour event, it is a rainfall event with a probable recurrence interval of once in two years as defined by the National Weather Service in Technical Paper No. 40, “Rainfall Frequency Atlas of the United States,” May 1961, and subsequent amendments, or equivalent regional or state rainfall probability information developed there from.  In Louisville this is 3.2 inches of rain occurring within a 24-hour period.

The Louisville Metropolitan Sewer District (MSD) website allows users to access precipitation data from the MSD monitoring network.  Several of MSD’s rainfall gauges reported more than 3 inches of rain during Saturday, February 24, 2018.  Considering the significant rain on Friday, February 23, 2018, other locations may have also exceeded 3.2 inches in a 24-hour period this week.

PRECIPITATION DATA FROM LOUISVILLE METROPOLITAN SEWER DISTRICT WEBSITE

http://raingauge.louisvillemsd.org/

Station Precipitation (inch) 2/23/2018 Precipitation (inch) 2/24/2018
TR01 – D. R. Guthrie 1.77 2.19
TR02 – PRP Fire Station Training Facility 1.79 2.26
TR03 – Shively PS 1.91 2.14
TR04 – Morris Forman WQTC 2.21 2.24
TR05 – Beargrass Creek PS 1.53 1.86
TR06 – Hite Creek WQTC 1.49 2.59
TR07 – Floyds fork WQTC 1.21 2.19
TR08 – Fern Creek Fire Station #3 1.56 0.45
TR09 – Cedar Creek WQTC 1.50 1.84
TR11 – Northern Ditch PS 1.49 2.91
TR12 – Nightingale PS 1.51 3.03
TR13 – St. Matthews Elementary School 1.47 2.66
TR14 Lea Ann Way 1.34 3.25
TR15 – Grand Avenue 0.85 1.49
TR16 – Stopher Elementary 1.67 2.77
TR17 – Mt. St. Francis 2.08 2.12
TR18 – IVY Tech 2.31 2.87
TR 19 Fairdale High School 1.36 3.24
TR20 – Pond Creek PS 1.54 0.71
TR21 Wheeler Basin 1.78 3.25
TR22 – Billtown Rd PS 1.39 1.53
TR23 – Transylvania Beach PS 1.89 2.04
TR24 – Spencer County Middle School 0.72 0.91
TR25 – Piccadilly 1.12 1.90
TR26 – Buechel Basin 1.17 1.67
TR27 – St. Michael Elementary 1.08 1.78
TR28 – Simpsonville Fire Station 1.20 1.38
TR29 – Hayswood Nature Reserve 2.71 2.20
TR30 – LG Compressor Station 1.93 2.47
TR31 – South Central High School 1.84 2.20
TR32 – Town of Corydon WWTP 2.35 2.09
TR-33 AB Sawyer Park 1.50 3.82
TR34 – Roosevelt-Perry Elementary 1.89 2.32
TR35 – Dunn Elementary 1.59 2.32
TR36 – Klondike Elementary 1.48 4.44
TR38 – Oldham County HS 1.27 2.86
TR39 – Bullitt East HS 1.37 1.67
TR40 – Zoneton Middle School 1.09 1.37

 

The Klondike Elementary station reported the highest rainfall for Saturday, at 4.44 inches.  For comparison, a 10 year, 24-hour storm in Louisville is 4.5 inches precipitation.  The 2 day total at that monitor, 5.92 inches, exceeds the 10 year 2-day storm event of 5.1 inches but does not reach the 25 year 2-day storm event total of 6.1 inches (MSD Design Manual, revised October 22, 2015, Exhibit 10-3).

The 2 year, 24-hour storm inspections are required to “verify the stability of the installed control measures and BMPs,” which isn’t a bad idea for all properties in the Louisville area this week.  Weather websites, such as Weather Underground, also offer historical precipitation data if your site does not have its own rain gauge or is outside of the Louisville area.  As you can see by the data, the amount of rainfall varies dramatically by area, so a site-specific rain gauge is a helpful to get accurate results.

Part of my work at Smith Management Group includes assisting facilities with stormwater and wastewater discharge permitting and permit compliance.  If you have questions or desire assistance, please contact me at (502) 587-6482 x 211 or PattyM@SmithManage.com.