20050578 Ver 1_More Info Received_20051018

[Fwd: Pennybyrn Updates]
Subject: [Fwd: Pennybyrn Updates]
From: Boyd Devane <[e-mail]>
Date: Tue, 18 Oct 2005 11:17:15 -0400
To: daryl lamb <[e-mail]>
CC: Cyndi Karoly <[e-mail]>
Attached is what the consultant sent me today showing the nutrient reduction they
would achieve if they were allowed to fill the stream but treat the existing runoff.
My initial review showed that their consultant was using reduction figures lower
than one's we normally accept and I'm not sure yet about their loading rates.
However, Danny and I are for pushing them to have extended detention wetlands before
the ponds just to achieve the greatest practicable removal. Any thoughts on that?
Subject: Pennybyrn Updates
From: "Moreschi, Monte" <[e-mail]>
Date: Mon, 17 Oct 2005 13:46:08 -0400
To: Boyd Devane <[e-mail]>
CC: "Moreschi, Monte" <[e-mail]>
Boyd,
Attached are the site summary table and nutrient removal calculations in a Section 7 update. This information was
requested by Danny and you. It will be formally sent to you overnight tomorrow but I figured you can never have it
to early.
Thanks,
Monte J. Moreschi, PE, LEED Accredited Professional
KOONTZ-BRYANT, P.C.
6909 International Drive, Suite 100
Greensboro, North Carolina 27409
[phone] Direct
[phone] Fax
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Pennybyrn Updates
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Site Summary Table.doc
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Section 7 Updates.pdf!
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10/18/2005 11:27 AM

Where `A' is the area in acres and `1' is the percent impervious cover as a whole number.
The volume is in cubic feet. The removal efficiency percentages for wel pond >3~1P's are
listed in the following table:
Wet Ponds
BMP /Desi Ratio Phos horns Removal Eta;
Desi 4 Permanent Vo1=Runoff Vol 35%
Desi 5 Permanent Vol = 2,5 times Runot~ Vol 40%
Desi 6 Permanent Vo1= 4 times Runoff Val 50%
The West Wet Pond Volume is 2.5 times larger than the Runoff Volume so a phosphorus
removal efficiency of 40 percent is used. The East Wet Pond Volume is 4.times larger
than the Runoff Volume so a phosphorus removal efficiency of SO percent is used.
Therefore, the West Wet Pond removes 10.50 lbs of phosphorus per year. The Fast Wet
Pond removes 3.87 lbs of phosphorus per year. The total phosphorous removed by the
wet ponds is 14.371bs of phosphorus per year.
I)EVBI.OPF.D PHOSPHOROUS LOADING (~l/ITHBUFFER UNDISTURBED)
The next steps calculate the theoretical phosphorus loading and removal if the buffer is
not disturbed and the wet ponds only treat proposed impervious areas. Therefore, the
existing impervious area is not routed through either pond as in the current plan. The
third step is to calculate the phosphorous loading of existing impervious areas that under
the current plan are treated in the West Wet Pond, The forth step is to calculate the
phosphorus removed by just treating the new impervious areas with similar wet ponds.
Step 3 -Calculation of Phosphorous LoAding with buffer not disturbed and only
proposed impervious areas routed through the ponds.
The existing impervious area from approximately sixteen (lb) acres is thirty-seven (37)
percent impervious. Therefore, its phosphorous loading from the attached table 1 is 0.89
lb/acre/yr or 14.24 ]bs of phosphorous per year. This is currently piped to City Lake
without any stonnwater treatment.
The proposed area to the West Wet Pond is approximately five (5) acres. The proposed
impervious area for this area is fifty-four (54) percent. Therefore, its phosphorous
loading from the attached table 1 is 1.25 lb/acre/yr or 6,251bs of phosphorous per year.
The proposed are to the East Wet Pond is approximately six (6) acres. The proposed
impervious area for this area is fifty-six (56) percent. Therefore, its phosphorous loading
from the attached table 1 is 1.29 lb/acre/yr or 7.74 lbs of phosphorous per year.
Therefore, the total phosphorous loading is 28.23 ]bs ofphosphorous per year.

four (54) percent. Therefore, its Annual runoff "R" is twenty point fifty-six {20.56)
inches. The total nitrogen loading is three hundred twenty three (323) pounds per year.
The proposed area to the Bast Wet Pond is approximately six (6) acres. The proposed
impervious area is fifty-six (56) percent. Therefore, its Annual runoff "R" is twenty one
point twenty-five (21,25) inches. The total nitrogen loading is ninety-five (95) pounds
per year.
Step 2 -Total Nitrogen Removal
The proposed wet ponds treat all proposed impervious areas flowing to the North, which
includes the addition to the nursing Home and community commons & independent living
building, along with, associated roads and parking lots. The West Wet Fond also treats
existing impervious area from approximately sixteen (16) acres on-site.
The removal percentages are based on national averages in Table 1 located in Appendix
2. We used a thirty three (33) percent removal percentage for Total Nitrogen in a
Stormwater Wet Pond.
Therefore, the West Wet Pond removes approximately one hundred seven (107) pounds
of total nitrogen per year. The East Wet Pond removes approximately thirty-one (31)
pounds of total nitrogen per year. The total nitrogen removed by the wet ponds is
approximately one hundred thirty-eight (138) pounds of nitrogen per year.
DEVELOFED TOTAL NITROGENLOADINC (f~'ITHIIUFFER UNDISTURBED
The next steps calculate the theoretical total nitrogen loading and removal if the buffer is
not disturbed and the wet ponds only treat proposed impervious areas. Therefore, the
existing impervious area is not routed through the either pond as in the current plan. The
third step is to calculate the total nitrogen loading of existing impervious areas that under
the current plan are treated in the West Wet Pond. The forth step is to calculate the total
nitrogen removed by just treating the new impervious areas with similar wet ponds.
Step 3 -Calculation of Total Nitrogen Loading with buffer not disturbed and only
proposed impervious Wrens routed through the ponds.
The existing impervious area from approximately sixteen (I ti) acres is thirty-seven (37)
percent impervious. Therefore, its Annual runoff"R" is fourteen point ffty-eight (14.58)
inches. The total nitrogen loading is approximately one hundred seventy-four (174)
pounds per year.
The proposed area to the West Wet Pond is approximately five (5) acres. The proposed
impervious area for this area is fifty-four (54) percent. Therefore, its Annual runoff "R"
is twenty point fifty-six (20.56) inches. The total nitrogen loading is approximately
seventy-six (76) pounds per year.