SW8880315_APPROVED PLANS_19880427

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW8 g80315
DOC TYPE
❑ CURRENT PERMIT
X❑ APPROVED PLANS
❑ HISTORICAL FILE
❑ COMPLIANCE EVALUATION INSPECTION
DOC DATE
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EROSION CONTROL NARRATIVE, CALCULATIONS AND NOTES r(
A. NARRATIVE: THE PROJECT SITE IS LOCATED IN CARTERET COUNTY _.
OFF OF GIBBS CREEK ROAD. THE SITE CONTAINS APPROXIMATELY
13 ACRES. APPROXIMATELY 2.6 ACRES WILL BE DISTURBED FOR \`i�\J
CONSTRUCTION OF STREETS AND SWALES. THE AREA IS TO BE ^ '
DEVELOPED AS A RESIDENTIAL SUBDIVISION. ALL RUNOFF CALCULATIIONS 1]G
ARE BASED ON THE RATIONAL METHOD, THE 10•YEAR DESIGN STORM
AND RAINFALL DATA FOR THE GENERAL AREA. CONSTRUCTION IS Q
TO BEGIN UPON APPROVAL OF AN EROSION CONTROL PLAN.
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B. EROSION CONTROL CALCULATIONS: THE PROJECT WILL BE DRAINED
BY A COMBINATION OF EXISTING FARM DITCHES AND NEW ROADSIDE (�
SWALES. THE ACCESS ROAD, GIBBS COURT, WILL BE CROSSED `y \m
AT THREE LOCATIONS WITH PIPE AS SHOWN ON THE PLAN. THE
REQUIRED OUTLET TREATMENT AND SUPPORTING CALCULATIONS FOLLOW:
PIPE# A=AREA_ DRAINED (ACRES_) PIPE SIZE Q=0_4(6m/hr)A OUTLET VELOCITY
1 3.43 18" 8.23CFS 4.66F/S V' v
2 2.85 15" 6.84CFS 5.57F/S
3 4.03 15" 9.68CFS 7.89F/S
BASED ON THE PIPE OUTLET VELOCITY CALCULATION, ENERGY DISSIPATORS
ARE REQUIRED AT ALL OUTLETS AS FOLLOWS:
PIPE# DISSIPATOR LENGTH DISSIPATORTH
- 1 10' lz' _ WIDTH
2 10' 12' �-
3 10' 12'
THE VELOCITIES HAVE BEEN CHECKED IN THE SWALE SECTIONS
FOR THE PROJECT. THE NEW SWALES WILL HAVE 3 to 1 SIDE
SLOPES AND A MINIMUM DEPTH OF 2 FEET. ALL CALCULATIONS 1.iJ v
ARE BASED ON MANNINGS EQUATIONS WHERE N=.022.
SWALE Q (CFS) SLOPE((FT/FT) CROSS -SECTIONAL AREA(FT2 VELOCITY(F/S)
- 3 - -- - -- - - - -.1
1 NW 3.79 .0038 1.78 2.13 um, v
1 NE 4.44 ,0057 1.73 2.57 z N
1 SW 0.50 .0057 .327 1.53
1 SE 0.50 .0057 .327 1.53
2 NW 5.06 .0031 2.43 2.08
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2 NE 1.78 .0259 .504 3.53 LL z
2 SW 0.55 .0031 .456 1.21 U. Z
2 SE 0.19 025, .087 2.18 = p
3 NE 1.87 .0049 \ .908 2.1 F 7
"z NW 3 84 nnTF nn m
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;;W 0.41 .0027 .37 1.11 t.
7.58 .0022 3.83 1.98 ,' L o 3
10.37 .0014 5.47 1.89 [_ J N
15.31 .0010 8.37 1.83
9.16 .0010 5.63 1.63 (•�
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THESE CALCULATIONS INDICATE THAT SWALES 1 NE AND 2 NE HAVE
VELOCITIES THAT REQUIRE EXTRA STABILIZATION OF THE SEED (n
AND MULCH ON THE SIDE SLOPES UNTIL A PERMANENT STAND OF
GRASS. IS ESTABLISHED. STABILIZATION: METHODS MAY INCLUDE Cc
TACKING WITH EMULSIFIED ASPHALT, JUTE MATTING OR OTHER W
EROSION CONTROL MATTING THAT IS APPROVED BY THE ENGINEER.
C. EROSION CONTROL MEASURES: TEMPORARY EROSION CONTROL MEASURES
WILL INCLUDE ANY TEMPORARY GRASSING REQUIRED UNTIL A PERMANENT
STAND OF GRASS IS ESTABLISHED, THE USE OF MULCH AND MULCH Z
STABILIZATION WHERE INDICATED ON THE PLANS AND INSTALLATION 4 w
OF A CONSTRUCTION ENTRANCE. PERMANENT EROSION CONTROL
MEASURES WILL INCLUDE THE ESTABLISHMENT OF PERMANENT STANDS
OF GRASS IN THE SWALES AND ROAD SHOULDERS AND THE ENERGY
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DISSIPATORS AT THE PIPE OUTLETS. °D
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D. EROSION CONTROL NOTES: J
1. ALL DISTURBED AREAS SHALL BE SEEDED AND MULCHED IN
ACCORDANCE WITH THE SEEDING SCHEDULE WITHIN 30 DAYS
OF DISTURBANCE. Z w
2. ADDITIONAL MEASURES MAY BE REQUIRED IF THOSE SHOWN O O
ON THIS PLAN DO NOT HALT EROSION. d U a
E. CONSTRUCTION SEQUENCE:
1. INSTALL CONSTRUCTION ENTRANCE.
2. CLEAN OUT EXISTING DITCHES WHEN SHOWN.
3. INSTALL PIPE WITH ENERGY DISSIPATORS.
4. PROCEED WITH CONSTRUCTION IN LOGICAL SEQUENCE.
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DATE PRINTED
MAR 2 4 IM