SW6201004_Response to Comments_20210427

Blackhawk Landing
Response to DEQ Plan Submittal Comments
Dated April 21, 2021

1. hƩźŭźƓğƌ /ƚƒƒĻƓƷƭ Б ε ЊЉ ΛtƩźƚƩ /ƚƒƒĻƓƷƭ Ћ ε Ќ ƩĻƭƦĻĭƷźǝĻƌǤΜ The full build-out potential of the
off-site drainage areas is 100% BUA. That means that the entire off-site portion of the drainage area
should be considered 100% impervious for the calculations. Currently, the submission shows an off-
site area of 441,638 sf and an off-site impervious area of 334,642 sf (Which is only approximately
75% BUA, not 100%). It is recommended to divert off-site runoff around the proposed SCM since
-site area as on-site BUA.

Response: Per the conversation on 4/23/21, the drainage areas have been revised. All documents
show that the off-site drainage area matches the off-site impervious area for a 100% Build-Out
Potential.

2. hƩźŭźƓğƌ /ƚƒƒĻƓƷ ЋЉ ΛtƩźƚƩ /ƚƒƒĻƓƷ ЏΜ It appears as though the drainage area to the SCM is
incorrect, there are areas within the SCM drainage area (See attached) that do not appear to drain
to the wet pond. It is unclear where the highlighted portion of the off-site drainage area (DA.png)
goes since it is not within the drainage area to any inlet & there does not appear to be a conveyance
from this area to the wet pond. In addition, the portion of the project area near Ledger Brook Lane
(DA 2.png) appears to just directly discharge into the wetland via the pipe network & overland flow.
If it is not possible to direct the BUA associated with the Ledger Brook Lane portion of the project to
an SCM, the wet pond can be oversized to treat this area. If this is the case, the drainage area to the
wet pond should not include the Ledger Brook Lane area but rather a note should be added to the
Supplement-EZ Form indicating that the wet pond is oversized and by how much. The drainage area
to the wet pond in the calculations and plans should reflect the actual area that drains to the wet
pond. Please show this drainage area on the plans and base the calculations off of this area.

Response: Per the conversation on 4/23/21, the drainage areas have been revised. Only what is
being directed to the SCM is enclosed in the drainage. All documents show that the off-site drainage
area matches the off-site impervious area for a 100% Build-Out Potential. The Supplement EZ form
includes a note stating the SCM is oversized and the difference in the design volume.