SW3210301_Add Info (Combined)_20210804

List of Discrepancies in the Submission Materials
Wet Pond #3
Item
Supp.-EZ
Calcs
Plan Sheet
Value Used for Review
Drainage Area
N/a
45.46 ac
N/a
44.99 ac*
Design Volume
107,158 cf
107,241 cf
N/a
107,158 cf
Excavated bottom
560.5
N/a
558.5
558.5
elevation of main pool
(Wet Pond
(Storage
Page, Line 20)
Elevation)**
Sediment Storage Top
561.0
559.0
559.0 (Basin
559.0
Elevation
(Line 21)
(Lowest X-
Bottom)**
Section)
Temporary Pool
566.76
566.76***
N/a
566.99 (from stage -
Elevation
(Line 25)
storage table)
Main Pool Surface Area
38,860 sf (Line
39,712 sf
N/a
39,712 sf
@ Perm. Pool
26)
Volume of the Main Pool
132,396 cf (Line
190,429 sf
N/a
190,429 sf
27)
Average Depth of the
2.89 ft
5.13 ft
N/a
5.13 ft
Main Pool
(Line 28)
Volume of Forebay
26,361 cf (Line
30,373 cf
N/a
30,373 cf
32)
Cleanout Depth of
48 in
72 in
N/a
72 in
Forebay
(Line 34)
Drawdown Time
3 days
46.79 hrs
N/a
2.6 days****
(Line 40)
(1.94 days)
Depth of Forebay
60 in
N/a
78 in
78 in
(Entrance)
(Line 43)
Depth of Forebay (Exit)
54 in
N/a
72 in
72 in
(Line 44)
* I couldn't find the drainage area calculations for the "final" wet pond #3 drainage area (42.94 ac.) so I
used the value from the Application. You will need to provide revised drainage area calculations for this
wet pond.
**The plan sheet indicates that the bottom of the basin is at elevation 559.0. The drawing is unclear
(See comment in general wet pond design issues comment section).
*** The cross -sectional area value at elevation 571 used to interpolate the temporary pool elevation
does not match the cross-section from the provided stage -storage table. The stage -storage table
indicates a cumulative storage volume at elevation 567 as 107,894 cf (which is almost the design
volume) indicating that the temporary pool elevation should be very close to this elevation
**** I calculated this value based on the provided stage -storage table and orifice configuration as
shown on the plans. It is comparable to the value shown in the Supplement-EZ Form. The value from the
calculations is less than the minimum 2-day drawdown time.

Wet Pond #4
Item
Supp.-EZ
Calcs
Plan Sheet
Value Used for
Review
SCM Side Slope
(Blank)
N/a
3:1
3:1
SCM Dewatering Method
Drawdown
N/a
Pump
Pump
Orifice (Line 9)
Excavated bottom
564.0
N/a
563.0 (Storage
563.0
elevation of main pool
(Wet Pond
Elevation)t
Page, Line 20)
Sediment Storage Top
564.5
564.5 (Lowest
563.5
563.5
Elevation
(Line 21)
X-Section)
(Basin Bottom) t
Temporary Pool Elevation
568.0
569.66tt
N/a
569.9 (from
(Line 25)
stage -storage
table) tt
Average Depth of the
2.95 ft
2.95 ft
N/a
3.2 ft ttt
Main Pool
(Line 28)
Cleanout Depth of
48 in
42 in
N/a
42 in
Forebay
(Line 34)
Orifice Diameter
3 in
3 in
3 in & 5 in
3 in
Drawdown Time
3 days
59.70 hrs
N/a
3 days
(Line 40)
(2.49 days)
Depth of Forebay
66 in
N/a
54 in
54 in
(Entrance)
(Line 43)
Depth of Forebay (Exit)
60 in
N/a
54 in
54 in
(Line 44)
t The plan sheet indicates that the bottom of the basin is at elevation 563.5. The drawing is unclear (See
comment in general wet pond design issues comment section).
tt The cross -sectional area value at elevation 573.5 used to interpolate the temporary pool elevation
does not match the cross-section from the provided stage -storage table. The stage -storage table also
has the wrong contour elevations shown. Correcting this results in a temporary ponding elevation of
approximately 569.9
ttt Using Equation 3 and the information provided in Lines 30 & 31 of the Supplement-EZ Form, the
average depth is 3.2 ft (Davg = ((54,465 cf — (0.5 * 0.5 ft * 660 ft * 3.0 ft)) / 16,789 sf) = 3.2 ft. The
average depth value provided in the calculations/supplement is less than the required 3.0 ft (Wet Pond
MDC 2) and is not calculated correctly (The cross -sectional area of the main pool at the permanent pool
elevation used in the average depth calculation ("SA Designed @ Elevation") incorrectly includes the
surface area of the forebay and the cross -sectional area of the main pool at the bottom of the vegetated
shelf used in the average depth calculation ("Area of wet pond at the bottom of the shelf") does not
match the value provided in the stage -storage table (16,789 sf)).

Wet Pond Design Issues
General
- Please clarify the difference between the "Storage Elevation" and the "Basin Bottom" as shown
on the wet pond cross -sections. There must be at least 6 in of sediment storage between the
excavated bottom of the pond and the top of the sediment storage zone (Wet Pond MDC 3).
The way that it is currently shown on the plans, it appears as though the excavated bottom of
the pond (solid line) is above the sediment storage top elevation (dashed line). Please see
attached image.
- Please clearly indicate the top of the sediment storage zone in the forebays in the cross -
sections. Wet Pond MDC 3 requires that the forebay and main pond have at least 6 inches of
sediment storage depth (The sediment storage top elevation should be at least 6 inches above
the excavated bottom of the forebay). Since the forebay entrance is deeper than the exit (and
the sediment storage elevation is typically constant) there will be more sediment storage depth
provided near the entrance than the exit (See attached image).
Wet Pond #3
- You will need to provide updated drainage area information (Size and BUA) for this SCM (Since
the "final' DA is different than the DA information submitted as part of the Phase 2 submission).
- There does not appear to be sufficient sediment storage provided within the forebay (Wet Pond
MDC 3). The plans indicate that the forebay exit is at elevation 559.0 and the stage -storage table
begins at elevation 559.0 (It is unclear what elevation the top of the sediment storage zone is
at).
- The temporary pool surface elevation is at approximately 566.99 ft based on the provided stage -
storage table. This is higher than the invert of the first bypass weir (566.8 ft). Unlike other SCMs,
there is no requirement that the design volume of a wet pond must be stored below any bypass
weir/orifice, only that it is drawn down to the permanent pool elevation within 2-5 days,
however it is recommended to move the bypass weir above the temporary ponding elevation. If
the invert of the bypass weir is not moved, its effect on the drawdown must be accounted for in
the calculations.
- Please provide riprap calculations showing that both the inflow and outflow of each SCM are
protected from erosion (General MDC 4). There does not appear to be riprap sizing calculations
for the 54" RCP pipe flowing into the forebay.
Wet Pond #4
- The main pool is too small (Wet Pond MDC 1). When selecting an SA/DA value to use, it is
recommended to interpolate a value from the table that corresponds to the actual average
depth of the main pool and the actual percent impervious cover of the drainage area (The
interpolated SA/DA table value is approximately 2.35). If you wish to use a value directly from
the table, you should round the average depth down to the nearest whole number and the
percent impervious cover up to the nearest 10% (which would result in an SA/DA value of 2.51).
Both of these methods result in a minimum required main pool surface area that is larger than
the provided main pool surface area.

The forebay entrance must be deeper than the forebay exit (Wet Pond MDC 5b). The cross-
section in the plans (Sheet C3.30) shows both the entrance and exit of the forebay at elevation
563.5.
Section A -A of the outlet structure shows the drawdown orifice having a diameter of 5 inches
(Which would result in a drawdown time faster than 2 days).
The contour elevations shown in the temporary ponding stage -storage table appear to be
incorrect.
- Please label the stormwater maintenance access/easement and ensure that the easement
includes the outlet pipe.
- It is recommended to include an emergency spillway (The cross-section on plan sheet C3.30
shows an emergency spillway, but the plan view does not appear to have one).

Combining the Submissions Together
Application
- Section I J — Change the project name to "Cresswind Phases 2 & 3".
- Section II, 4a & b — Combine these items from both phases (showing the total acres of E&SC
disturbance and any permits that are needed for either Phase 2 or Phase 3).
- Section III, 1c — Resolve this discrepancy between the submissions (It is recommended to
indicate that the Applicant is also the Property Owner since KH Wesley Chapel, LLC owns the
property).
- Section IV, 1— Update the treatment summary to mention two wet ponds (you may also want to
mention the phased nature of this project/permit).
- Section IV, 4 — Combine these items from Phase 2 & Phase 3. This item should be equal to the
total property area of Phases 2 & 3.
- Section IV, 6 — Combine these items from Phase 2 & Phase 3. This item should be equal to the
total on -site surface water of Phases 2 & 3.
- Section IV, 7 — This item will need to be recalculated (= Section IV, 4 — Section IV, 5 — Section IV,
6).
- Section IV, 8 —This item will need to be recalculated based on the total amount of BUA that will
be added for Phases 2 & 3 and Section IV, 7.
- Section IV, 9 — Increase this item to 2 drainage areas (one for wet pond 3 & one for wet pond 4).
- Section IV, 10 — Combine the drainage area information from Phases 2 & 3, revising as needed
(The information in this table should be a reflection of the drainage areas to wet pond 3 and wet
pond 4 in the final, post -construction conditions and should be consistent with the calculations
& supplement form).
Supplement-EZ Form
Cover Page
o Line 1— Change the project name to "Cresswind Phases 2 & 3".
o Lines 2-4 — Combine these items from both phases. NOTE: Line 2 is project area, not
property area.
o Line 13 — Change this item to indicate 2 wet ponds (you will also need to "re -load" the
form to get the second column on the wet pond page).
Drainage Area Page
o Line 2 — Change this item to indicate 2 drainage areas (you will also need to "re -load"
the form to get the second drainage area column).
o Entire Site Column — This column is an accounting of all of the BUA that will be located
within the project area in post -construction conditions (it is not merely just a
summation of the values from the drainage area columns). For example, any BUA that
does not drain to either wet pond 3 or wet pond 4 would be included in this column
(This column would also include the on -site portion of the BUA within the drainage
areas).
■ The "Type of SCM", "Design Storm", "Design Volume", & "Calculation Method"
items are not required for the entire site column.

■ The "Drainage Area" of the entire site refers to the project area of the entire
site.
o The sum of the "Breakdown of New BUA not on Subdivided Lots" items should add up to
the "New BUA not on Subdivided Lots" item.
o The sum of the "New BUA on Subdivided Lots" and the "New BUA not on Subdivided
Lots" items should equal the "Total BUA in Project" (Since there are no off -site
components nor existing BUA).
o The "Percent BUA" should equal the "Total BUA in Project" divided by the "Total
Drainage Area"
o The "Design Volumes" should be consistent with the calculations.
o Please ensure that the BUA values shown are consistent with the other submittal items.
- Wet Pond Page
o The discrepancies between the information in the Supplement-EZ Form and other
submittal items is noted in the "List of Discrepancies in the Submission Materials"
section. Please ensure that the information entered into the Supplement-EZ Form
matches the rest of the submission. If you have any questions about the Supplement-EZ
Form, please reach out to me.
O&M Agreement Form
- We can use the Phase 2 & Phase 3 O&M Form signatures that we currently have (since we have
one for each phase/wet pond) or you can provide a revised O&M Agreement form combining
the two phases/wet ponds, either option will work.
- Please revise the wet detention pond summary information so that it is consistent with the
other submittal items.
o Per the plans, the proposed wet ponds do not appear to incorporate vegetated filter
strips (a vegetated filter strip is typically located downstream of the outlet structure and
is different than the vegetated shelf).
o The normal pool elevation corresponds to Line 23 of the Wet Pond Page of the
Supplement-EZ Form.
o The temporary pool elevation corresponds to Line 25 of the Wet Pond Page of the
Supplement-EZ Form.
o The cleanout depth is the distance from the normal pool elevation to the sediment
storage elevation (This might be different for the main pool & forebay).
o The sediment storage elevation is the elevation of the top of the sediment storage zone
(Line 21 for the main pool and must be calculated for the forebay)
o The bottom elevation is the excavated bottom of the main pool (Line 20) and the
forebay (elevation of the "forebay exit")
Calculations
- Please ensure that the calculations are revised for consistency with the other submittal items
and are done for the final, post -construction conditions. You may either keep separate
calculation books for each phase (provided each calculation booklet reflects the final, post -
construction conditions) or combine them into a single calculation booklet.

Stormwater Narrative
The stormwater narrative should cover both phases since they are now being permitted as one
project.
Plan Set
- You may either keep separate plan sets for each phase (provided each plan set reflects the final,
post -construction conditions, i.e. shows what the Phase 2 area will look like once Phase 3 is
complete) or combine them into a single plan set (or you can have two main plan sets with some
shared common plans).
- Please dimension the project area (Phase 2 & 3) boundary with bearings and distances (Section
VI, 8i). You may wish to show this on a single plan sheet.
- Please identify and dimension all proposed BUA for this project (Section VI, 8j). The information
shown in the Application and Supplement-EZ Form should be verifiable from the plans. You may
wish to show this on a single plan sheet.
- Please place a note on the plans stating the identity of the person that made the wetland
determination (Section VI, 8m).
- Please delineate the drainage areas to the proposed SCMs in the plans (Section VI, 8o). You may
wish to show this on a single plan sheet.
- Please ensure that maintenance accesses and easements are clearly shown on the plans and
extend to the nearest public right-of-way (General MDCs 8 & 9). It was noted during review that
the roads associated with this project will be private roads.
- An electronic copy of the Phase 3 plan sheets was not uploaded to the repository. Please ensure
that the relevant plan sheets for Phase 3 get uploaded.