20110661 Ver 1_More Info Received_20120412

® Jones & Cnossen
® ENGINEERING PLLC
Civil Engineering I Construction Management I Land Planning
Ms Karen Higgins
NCDWQ — Division of Water Quality
1650 Mail Service Center
Raleigh North Carolina 27699
RE Request for More Information
Chastain Subdivision (DWQ Project #2011 066 1)
Dear Karen
221 N SALEM ST SUITE 200
PO BOX 1062
APEX NC 27502
Office 919 387 1174
Fax [phone]
wwwjonescnossen corn
March 30 2012
I have received your letter Request for More Information dated March 1 20121 and am herein providing the
following responses for continuation of staff's review of the project
1 In accordance with DWQ recommendations a by pass system has been designed The 1 /hr storm
has been routed to the proposed scour hole while larger storm events will discharge to a high flow
by pass channel These new features are shown on the attached plans for review Please note that
the scour hole design will match the recommendations provided by our geotechnical consultant
2 The upland drainage area has been reviewed and the C value has been revised accordingly The new
C value is shown in the calculations
3 A CD is attached with TIFF format copies of the plans
It is hoped that this information is sufficient for approval following your review If you have any questions
or need anything else please let me know
Sincerely
0
. 1 a
eter D Cnossen P E
Jones & Cnossen Engineering PLLC
Cc Divida Johnson — Omega Management
Attachments
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Peter Cnossen Page 1 3/28/2012
140
1
1
3129/2012
Chastain - Phase
10
YI #181A
1 -Year Storm
Peak Flow =
23.8
Outlet Size =
24"
Time to Peak =
5
Incoming Pipe =
36"
Time (min)
Inflow (cfs)
Storage (cf)
Stage (ft)
Outflow (cfs) "
0
0.0
0
0
0
0
0.5
0.6
0
0.00
0.0
17
1
2.3
17
0.02
2.3
-1
1.5
5.0
16
0.02
2.2
83
2
8.3
99
0.14
5.5
85
2.5
11.9
184
0.25
7.5
132
3
15.5
316
0.43
9.8
169
3.5
18.8
486
0.66
12.2
199
4
21.4
684
0.93
14.5
209
4.5
23.3
894
1.22
16.5
204
5
23.8
1098
1.49
18.3
165
5.5
23.3
1263
1.72
19.6
111
6
21.4
1374
1.87
20.5
- 28
6.5
20.2
1402
1.91
20.7
-14'
7
17.6
1388
1.89
20.6
-89
7.5
15.2
1299
1.77
19.9
-140
8
13.1
1159
1.58
18.8
-171
8.5
11.4
987
1.34.
17.4
-178
9
10.0
809
1.10
15.7
-172
9.5
8.6
638
0.87
14.0
-1.61'
10
7.4
476
0.65
12.1
-140
10.5
6.4
336
0.46
10.1
0140.RTG

Peter Cnossen Page 2 3/28/2012
11
5.7
225
0.31
8.3
-77
11.5
4.8
148
0.20
6.7
-59
12
4.3
89
0.12
5.2
-28
12.5
3.6
61
0.08
4.3
-23
13
3.1
39
0.05
3.4
0140.RTG

Peter Cnossen Page 1 3/2812012
140
3/29/2012
Chastain - Phase
10
YI #181A
10 -Year Storm
Peak Flow =
36.3
Outlet Size =
24"
Time to Peak =
5
Incoming Pipe =
36"
Time (min)
Inflow (cfs)
Storage (cf)
Stage (ft)
Outflow (cfs)
0
0.0
0
0
0
0
0.5
0.9
0
0.00
0.0
26
1
3.4
26
0.04
2.8
19
1.5
7.6
45
0.06
3.7
118
2
12.7
163
0.22
7.0
170
2.5
18.2
332
0.45
10.1
242
3
23.6
575
0.78
13.2
311
3.5
28.7
885
1.20
16.4
367
4
32.7
1253
1.70
19.6
394
4.5
35.6
- - 1646
2.24
22.4
395
5
36.3
2041
2.78
25.0
340
5.5
35.6
2381
3.24
27.0
259
6
32.7
2640
3.59
28.4
129
6.5
30.9
- 2768
3.77
29.1
54
7
26.9
2822
3.84
29.3
-75
7.5
23.2
2748
3.74
29.0
-172
8
20.0
2576
3.50
28.0
-242
8.5
17.4
2334
3.18
26.7
-278
9
15.2
2056
2.80
25.0
-294
9.5
13.1
1762
2.40
23.2
-304
10
11.3
1458
1.98
21.1
-295
10.5
9.8
1163
1.58
18.8
-271
0140.RTG

Peter Cnossen Page 2 3/28/2012
11
8.7
892
1.21
16.5
-234
11.5
7.3
658
0.90
14.2
-207
12
6.5
451
0.61
11.7
-156
12.5
5.4
295
0.40
9.5
-121
13
4.7
174
0.24
7.3
0140. RTG

Peter Cnossen Page 1 3/2812012
140
1
1 3/29/2012
Chastain - Phase
10
YI #1816
1 " /HR Storm
Peak Flow =
5.1
Outlet Size=
12"
Time to Peak =
5
Incoming Pipe =
42"
Time (min)
Inflow (cfs)
Storage (cf)
Stage (ft)
Outflow (cfs)
0
0.0
0
0
0
0
0.5
0.1
0
0.00
0.0
4
1
0.5
4
0.00
0.2
8
1.5
1.1
11
0.01
0.4
20
2
1.8
31
0.03
0.7
33
2.5
2.6
65
0.07
1.0
47
3
3.3
112
0.12
1.3
61
3.5
4.0
173
0.18
1.6
73
4
4.6
246
0.26
1.9
81
4.5
5.0
327
0.34
2.2
84
5
5.1
412
0.43
2.4
80
5.5
5.0
491
0.51
2.7
70
6
4.6
561
0.58
2.9
52
6.5
4.3
613
0.64
3.0
40
7
3.8
653
0.68
3.1
21
7.5
3.3
674
0.70
3.1
4
8
2.8
678
0.70
3.1
-10
8.5
2.4
668
0.69
3.1
-20
9
2.1
648
0.67
3.1
-28
9.5
1.8
620
0.64
3.0
-35
10
1.6
585
0.61
2.9
-40
10.5
1.4
544
0.57
2.8
-43
0140. RTG

Peter Cnossen Page 2 3/28/2012
11
1.2
501
0.52
2.7
-44
11.5
1.0
457
0.47
2.6
-47
12
0.9
410
0.43
2.4
-46
12.5
0.8
364
0.38
2.3
-46
13
0.7
318
0.33
2.2
0140.RTG

Peter Cnossen Page 1 3/28/2012
140
1 1
1 3/29/2012
Chastain - Phase
10
YI #181 B
1 -Year Storm
Peak Flow =
21.0
Outlet Size =
12° & 18"
Time to Peak =
5
Incoming Pipe =
42"
Time (min)
Inflow (cfs)
Storage (cf)
Stage (ft)
Outflow (cfs)
0
0.0
0
0
0
0
0.5
0.5
0
0.00
0.0
15
1
2.0
15
0.02
0.5
46
1.5
4.4
61
0.06
-0.9
104
2
7.4
165
0.17
1.6
174
2.5
10.5
339
0.35
2.2
248
3
13.7
587
0.61
2.9
322
3.5
16.6
909
0.94
3.6
389
4
18.9
1298
1.35
4.3
437
4.5
20.6
1734
1.80
5.0
467
5
21.0
2201
2.29
11.5
285
5.5
20.6
2486
2.58"
13.4
214
6
18.9
2701
2.81
14.7
126
6.5
17.9
2827
2.94
15.4
74
7
15.5
2901
3.02
15.8
-6
7.5
13.4
2895
3.01
15.7
-68
8
11.6
2827
2.94
15.4
-114
8.5
10.1
2712
2.82
14.7
-140
9
8.8
2572
2.67
14.0
-154
9.5
7.6
2418
2.51
13.0
- 163
10
6.5
2255
2.34
11.9
-161
10.5
5.7
2094
2.18
10.6
-149
0140. RTG

Peter Cnossen Page 2 3/28/2012
11
5.0
1945
2.02
9.2
-125
11.5
4.2
1820
1.89
7.6
-101
12
3.8
1719
1.79
5.0
-37
12.5
3.2
1683
1.75
5.0
-54
13
2.7
1628
1.69
4.9
0140. RTG

Peter Cnossen Page 1 3/28/2012
140
1
1
1 3/29/2012
Chastain - Phase
10
YI #181B
10 -Year Storm
Peak Flow =
29.7
Outlet Size =
12" & 18"
Time to Peak =
5
Incoming Pipe =
42"
Time (min)
Inflow (cfs)
Storage (cf)
Stage (ft)
Outflow (cfs)
0
0.0
0
0
0
0
- 0.5
0.7
0
0.00
0.0
21
1
2.8
21
0.02
0.6
68
1.5
6.2
89
0.09
1.1
153
2
10.4
242
0.25
1.9
255
2.5
14.9
498
0.52
2.7
365
3
19.3
862
0.90
3.5
473
3.5
23.5
1335
1.39
4.4
572
4
26.7
1907
1.98
8.8
539
4.5
29.1
2446
2.54
13.2
478
5
29.7
2924
3.04
15.9
415
5.5
29.1
3339
3.47
17.8
338
6
26.7
3677
3.82
19.3
224
6.5
25.2
3901
4.05
20.2
153
7
22.0
4053
4.21
20.7
37
7.5
19.0
4090
4.25
20.9
-56
8
16.3
4034
4.19
20.7
-130
8.5
14.3
3904
4.06
20.2
-178
9
12.5
3726
3.87
19.5
-210
9.5
10:7
3516
3.66
18.6
-237
10
9.2
3279
3.41
17.6
-251
10.5
8.0
3028
3.15
16.4
-251
0140. RTG

Peter Cnossen Page 2 3/28/2012
11
7.1
2777
2.89
15.1
-239
11.5
5.9
2538
2.64
13.7
-234
12
5.3
2304
2.39
12.2
-207
12.5
4.5
2097
2.18
10.7
-186
13
3.9
1911
1.99
5.3
0140. RTG

JONES &
,CNOSSEN
ENGINEERING, PLLC
Job No. to9lo -,L , Sh. Of
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1. CONSTRUCT ROCK DAM AT BREACH IN EXISTING CREEK BANK.
2. GRADE BANKS OF EROSIVE FEATURE TO MAXIMUM 2:1 SLOPES.
3. INSTALL MIRAFI I I OON OR EQUIVALENT GEOTEXTILE LINER ON
NEWLY GRADED SLOPES.
4. INSTALL G -8" OF WASHED STONE (NO. 57) ON BOTTOM TO
CUSHING FOR PLACEMENT OF RIP -RAP.
5. INSTALL RIP -RAP (CLASS 2) AND SHAPE TO PROMOTE ENERGY
DISSIPATION THROUGH SCOUR HOLE.
G. SEED AND STRAW DENUDED AREAS OUTSIDE SCOUR HOLE THAT
MAY HAVE BECOME DISTURBED DURING REPAIR OPERATIONS.
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