Bioretention Rogojan Project Graph and ChartM Gmail
Bioretention Rogojan Project
Mirel Rogojan <bigalrogo@gmail.com>
Donna Breske <donnab@donnabreske.com> Thu, Aug 13, 2020 at 2:30 PM
To: "brian@amsbarylaw.com" <brian@amsbarylaw.com>
Cc: Mirel Rogojan <bigalrogo@gmail.com>
Brian, Good news.
I reached out and received the below e-mail from Doug Beyerlein, PE of Clear Creek Solutions. Clear
Creek Solutions is the company that was contracted by the Washington Department of Ecology to
develop the WWHM2012 Hydrology software program. Clear Creek Solutions continues to manage
the program for the DOE, and the company also provides training for the program.
Doug Beyerlein <beyerlein@clearcreeksolutions.com>
Thu 8/13/2020 12:29 PM
To: Donna Breske
Donna,
I looked at your WWHM2012 project file:
1. The model shows that you will get 100% infiltration. That includes the 100-year storm. Do
you still need a downslope easement?
Doug Beyerlein, PE, PH, D.WRE
Clear Creek Solutions, Inc.
15800 Village Green Drive #3
----------------------------------
Mill Creek, WA 98012
-------------------------
Office: 425-225-5997
beyerlein@clearcreeksolutions.com
www.clearcreeksolutions.com
Bioretention Bottom Elevatior
Bioretention Dimensions
Bioretention Length (ftj
Bioretention Bottom Width (It)
8.f1f1
Freeboard (It)
0.
Effective Total Depth (ft)
Bottom slope of bioretention.(0-1 J
0.0p0
r Sidewall Invert Location -
Front and Back side slope (HN)
3.p0p
Left Side Slope (HN)
3.pD0
Right Side Slope (HN)
`3.00p
Flow Through Llnderdrain Jac•fti
Total Outflow (ac•ftj
4r10 Percent Filtered 100
Facility Dimension Diagram
Riser Outlet Structure
Outlet Structure Data
Riser Height Above bioretention surface (ft) p.g
Riser Diameter (in) 12 J
Riser Type Flat _7 11
Brian,
The above is new information to me. I was not aware that within the WWHM2012, (Western
Washington Hydrology Model). That is, if 100 percent infiltration/filtration is achieved, the sizing
includes the 100-year storm event. Hence, there is basically no reasonable requirement for any sort
of down slope easement since the bioretention system is sized to accept the 100-year storm event,
(3.5 inches+/- in 24-hours). That is a lot of rain in a 24-hour period!
For perspective; From December 18, to December 21, 2019, the region had up to 4 inches in 72
hours. That was a lot of rain. The bioretention system for the Rogojan's is sized to have managed
the December 2019 three-day rain event with no overflow.
Heavy rain could bring Seattle's wettest day of the entire year
Between 2.5 and 4 inches of rain are expected in the area between Wednesday
afternoon and Saturday afternoon. Previous reports indicated that Seattle could see
its wettest day of the year over that period, and possibly the most rainiest day the
area's seen since November 2018.
Below is the verbiage from the 2014 DOE Manual that previously led me to conclude that LID
Performance Standard resulted in a storm water management LID BMP, (Low Impact Development
Best Management Practice), sized only to handle runoff from the 50-year storm event.
From the 2014 DOE Stormwater Management Manual for Western Washington Volume I - Chapter 2 -
Page 56
Low Impact Development Performance Standard
Stormwater discharges shall match developed discharge durations to pre -developed durations for the
range of pre -developed discharge rates from 8% of the 2-year peak flow to 50% of the 2-year peak
flow. Refer to the Standard Flow Control Requirement section in Minimum Requirement #7 for
information about the assignment of the pre -developed condition. Project sites that must also meet
minimum requirement #7 — flow control - must match flow durations between 8% of the 2-year flow
through the full 50-year flow.[emphasis added]
Per Doug Byerlein's e-mail, I am now aware that the 50-yr storm is the minimum threshold per the
DOE Manual. However, the software program, WWHM2012 provides a bioretention system sized to
accept and manage storm water runoff for up to the 100-year event.
Sincerely,
Donna L. Breske, PE
21 Ave A, Suite 4, Snohomish, WA 98290
Mobile: 206-715-9582
Phone: 360-294-8941
11 Donna Brk
Associates
Donna Breske <donnab@donnabreske.com>
To: "brian@amsbarylaw.com" <brian@amsbarylaw.com>
Cc: Mirel Rogojan <bigalrogo@gmail.com>
Brian,
Mon, Aug 17, 2020 at 10:39 AM
I spoke and coordinated some more with Doug Beyerlein at Clear Creek Solutions.
The below graph and chart depict the concept you and discussed on the phone last week.
PREDEVELOPED:
The Predeveloped 501 POC represents the stormwater runoff from the site in it's current condition with
the small house and driveway, assuming no formal stormwater management elements have been
installed, drywells, etc.
The blue line represents storm water flows leaving the site in the current condition.
MITIGATED:
The Mitigated 801 POC represents the storm water runoff routed to and managed by the bioretention
system, from the rooftop of the proposed house and and the proposed driveway. The red line within
the graph demonstrates that there is zero probability of storm water flows released from the
bioretention. The column within the chart with the header Mitigated also demonstrates the zero flows
anticipated to be released from the Bioretention.
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Sincerely,
Donna L. Breske, PE
Mobile: 206-715-9582
Phone: 360-294-8941
11 Donna Breske
Associates
From: Donna Breske
Sent: Thursday, August 13, 2020 2:30 PM
To: brian@amsbarylaw.com <brian@amsbarylaw.com>
Cc: Mirel Rogojan <bigalrogo@gmail. com>
Subject: Bioretention Rogojan Project
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