06 - Erosion Report_v1
Sedimentation & Erosion Control Analysis
Project: Circle K – R&R 2720915
5717 Castle Hayne Road (Hwy 117),
Castle Hayne, NC 28429
New Hanover County
Timmons Group
5410 Trinity Road, Suite 102
Raleigh, NC 27607
(919) 866-4939
rick.baker@timmons.com
REVISIONS:
Table of Contents
1) Sedimentation & Erosion Control Narrative
1. Project Overview
2. Erosion Control
a. Summary
b. Planned Erosion Control and Sedimentation Control Practices
c. Erosion Control Maintenance Plan
2) Resource Maps
1. USGS Map showing Project Site
2. NRCS Soil Survey Map
3. FEMA FIRM Panel 3720323200K
4. NOAA Precipitation Frequency Map
3) Erosion Control Calculations
1. Sediment Basin Sizing
2. Temporary Diversion Ditch Sizing
3. Rip Rap Sizing
1) Sedimentation & Erosion Control Narrative
Erosion Control Narrative
1. Project Overview
The proposed Circle K project is located at the intersection of Castle Hayne Road (Hwy 117) and
Lynn Avenue (SR-1338). The project site currently consists of three (3) lots with vacant land on two
lots and an existing Circle K store on one lot. The project will consolidate all the tracks into one lot.
The total track area of the combined lot is 6.22 acres. The applicant proposes a new 5,200 sf Circle
K store. For reference, the subject property information is as follows:
PINs: R01109-002-002-000, R01109-002-001-000, R01100-015-
001-000
River Basin: Cape Fear
Classification: C; Sw
Stream: Prince George Creek
Stream Index: 18-74-53
Total Project Site Acreage: 6.22 acres
Total Disturbed Acreage: 4.86 acres
Latitude & Longitude: 34°21'16.63"N 77°54'0.37"W
Existing Conditions
There is 0.96 acres (15.4%) of existing impervious cover onsite. Most of the site is in hydrologic soil
group “A”. Half of the site sheets flows to ditch along Highway 117 and the remaining half sheet
flows to the west of the property which then gets collected in a ditch and discharges to the ditch along
Highway 117 via. conveyance pipe. Per FEMA FIRM Panel 3720323200K (02/16/07) the site is not
located in a flood plain. No site development is proposed near a jurisdictional stream.
Proposed Site Improvements
The proposed project consists of a gas station with convenience store (1-story, 5,200 S.F. building),
high speed diesel, truck weighing area and associated parking lot, canopies, driveways, and utilities.
The proposed development will increase the onsite impervious cover from 0.96 acres to 2.38 acres
(38.3% of the project site). Majority of the onsite impervious runoff will be conveyed through a series
of storm network and outlets to two (2) proposed wet ponds on site. The remaining portion of the
impervious runoff sheet flows directly to Castle Hayne Road (Hwy 117) and Lynn Avenue (SR 1338).
The outlet discharge from both the wet ponds is collected via storm conveyance pipe and discharged
to an existing ditch located along the Castle Hayne Road (Hwy 117) right-of-way.
2. EROSION CONTROL
A. SUMMARY
The runoff from the disturbed areas will drain into storm conveyance pipe and collected at
both the proposed wet ponds. Temporary diversion ditches have been placed to capture
runoff onsite and transport them to the sediment basins. The temporary ditches will be
lined with N. American Green matting and outlet onto riprap dissipater pads before exiting
the site. Silt fence will be placed in key areas to prevent localized sediment runoff at the
bottom of slopes. Inlet protection has been added to keep sediment from entering
stormwater pipes. Riprap aprons will be added to keep water from leaving the site at
erosive velocities.
B. PLANNED EROSION CONTROL AND SEDIMENTATION CONTROL
PRACTICES
Construction Entrance – Construct Entrance(s) to be located as shown on the plans
Rip Rap Outlet Protection – Rip rap outlet protection to be located as shown on the plans
Temporary Inlet Protection – Construct temporary inlet protection at proposed inlets as
shown on the plans
Temporary Diversion Ditch – Construct temporary diversion ditches to direct flow into the
temporary skimmer basin as shown on the plans
Silt Fence/Silt Fence Outlets – Silt fence and silt fence outlets as shown on the plans
Temporary Skimmer Basins – Construct temporary skimmer basins as shown on the plans
Seeding – Disturbed areas will be seeded (refer to plan sheet C6.0 of the Plans for the
seeding schedule)
C. EROSION CONTROL MAINTENANCE PLAN
a. All erosion and sediment control practices will be checked for stability and operation
following every runoff-producing rainfall, but in no case less than once every week.
Any needed repairs will be made immediately to maintain all practices as designed.
b. Sediment will be removed from the erosion control devices when storage capacity
has been approximately 50 percent filled.
c. All seeded areas will be fertilized, reseeded as necessary, and mulched according to
specifications to maintain a vigorous, dense vegetative cover.
d. Also refer to maintenance requirements listed for each device on plans.
2) Resource Maps
SITE
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/10/2022
Page 1 of 4
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232950 232990 233030 233070 233110 233150 233190 233230 233270 233310 233350
232950 232990 233030 233070 233110 233150 233190 233230 233270 233310 233350
34° 21' 21'' N
77
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34° 21' 21'' N
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34° 21' 12'' N
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34° 21' 12'' N
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N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84
0 50 100 200 300
Feet
0 25 50 100 150
Meters
Map Scale: 1:1,900 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:15,800.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: New Hanover County, North Carolina
Survey Area Data: Version 24, Sep 12, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Oct 5, 2020—Nov 24,
2020
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/10/2022
Page 2 of 4
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
Ke Kenansville fine sand, 0
to 3 percent slopes
A 8.3 94.9%
Ls Lynchburg fine sandy
loam, 0 to 2 percent
slopes, Atlantic Coast
Flatwoods
B/D 0.4 4.5%
St Stallings fine sand A/D 0.0 0.6%
Totals for Area of Interest 8.7 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/10/2022
Page 3 of 4
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—New Hanover County, North Carolina
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/10/2022
Page 4 of 4
National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOODHAZARD AREAS
Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREENArea of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.The basemap shown complies with FEMA's basemapaccuracy standards
The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 11/10/2022 at 6:59 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximatepoint selected by the user and does not representan authoritative property location.
1:6,000
77°54'20"W 34°21'33"N
77°53'42"W 34°21'3"N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
SITE
10/4/22, 2:49 PM Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=34.3555&lon=-77.8992&data=depth&units=english&series=pds 1/4
NOAA Atlas 14, Volume 2, Version 3
Location name: Castle Hayne, North Carolina,
USA*
Latitude: 34.3555°, Longitude: -77.8992°
Elevation: 16.51 ft**
* source: ESRI Maps ** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Duration Average recurrence interval (years)
1 2 5 10 25 50 100 200 500 1000
5-min 0.517
(0.482‑0.558)
0.614
(0.572‑0.662)
0.718
(0.667‑0.774)
0.800
(0.740‑0.861)
0.903
(0.832‑0.970)
0.980
(0.899‑1.05)
1.06
(0.967‑1.14)
1.14
(1.03‑1.23)
1.24
(1.12‑1.34)
1.33
(1.18‑1.43)
10-min 0.826
(0.769‑0.891)
0.982
(0.914‑1.06)
1.15
(1.07‑1.24)
1.28
(1.18‑1.38)
1.44
(1.33‑1.55)
1.56
(1.43‑1.68)
1.69
(1.54‑1.81)
1.81
(1.64‑1.94)
1.97
(1.76‑2.12)
2.09
(1.86‑2.26)
15-min 1.03
(0.962‑1.11)
1.24
(1.15‑1.33)
1.46
(1.35‑1.57)
1.62
(1.50‑1.74)
1.82
(1.68‑1.96)
1.98
(1.81‑2.13)
2.13
(1.94‑2.29)
2.28
(2.06‑2.45)
2.47
(2.22‑2.67)
2.62
(2.33‑2.84)
30-min 1.42
(1.32‑1.53)
1.71
(1.59‑1.84)
2.07
(1.92‑2.23)
2.34
(2.17‑2.52)
2.70
(2.49‑2.90)
2.98
(2.73‑3.20)
3.26
(2.98‑3.51)
3.55
(3.21‑3.82)
3.94
(3.53‑4.25)
4.25
(3.78‑4.59)
60-min 1.77
(1.64‑1.90)
2.14
(1.99‑2.31)
2.65
(2.46‑2.86)
3.05
(2.83‑3.29)
3.60
(3.32‑3.86)
4.03
(3.70‑4.34)
4.49
(4.10‑4.83)
4.97
(4.51‑5.35)
5.65
(5.07‑6.10)
6.20
(5.52‑6.70)
2-hr 2.10
(1.93‑2.29)
2.56
(2.36‑2.79)
3.26
(3.00‑3.55)
3.83
(3.52‑4.18)
4.67
(4.26‑5.09)
5.39
(4.90‑5.87)
6.17
(5.58‑6.71)
7.03
(6.30‑7.63)
8.30
(7.36‑9.03)
9.38
(8.26‑10.3)
3-hr 2.24
(2.07‑2.46)
2.73
(2.52‑3.00)
3.50
(3.21‑3.82)
4.15
(3.80‑4.54)
5.13
(4.66‑5.59)
5.98
(5.41‑6.52)
6.92
(6.22‑7.54)
7.98
(7.10‑8.68)
9.58
(8.43‑10.4)
11.0
(9.55‑12.0)
6-hr 2.77
(2.55‑3.05)
3.38
(3.11‑3.71)
4.32
(3.97‑4.75)
5.15
(4.71‑5.64)
6.38
(5.80‑6.96)
7.45
(6.73‑8.14)
8.67
(7.77‑9.45)
10.0
(8.88‑10.9)
12.1
(10.6‑13.2)
13.9
(12.0‑15.2)
12-hr 3.25
(2.96‑3.60)
3.96
(3.61‑4.37)
5.10
(4.65‑5.64)
6.11
(5.53‑6.73)
7.62
(6.85‑8.38)
8.96
(8.01‑9.84)
10.5
(9.29‑11.5)
12.2
(10.7‑13.4)
14.9
(12.8‑16.3)
17.2
(14.7‑18.9)
24-hr 3.80
(3.44‑4.26)
4.61
(4.17‑5.18)
5.96
(5.39‑6.69)
7.15
(6.45‑8.00)
8.98
(8.01‑10.0)
10.6
(9.38‑11.9)
12.5
(10.9‑13.9)
14.6
(12.6‑16.3)
17.8
(15.1‑20.1)
20.7
(17.2‑23.4)
2-day 4.48
(4.08‑5.00)
5.42
(4.93‑6.04)
6.95
(6.30‑7.75)
8.28
(7.48‑9.23)
10.3
(9.24‑11.5)
12.1
(10.7‑13.5)
14.1
(12.4‑15.8)
16.4
(14.2‑18.5)
19.9
(16.8‑22.5)
22.9
(19.1‑26.1)
3-day 4.77(4.34‑5.32)5.76(5.24‑6.43)7.34(6.66‑8.19)8.70(7.87‑9.70)10.8(9.64‑12.0)12.5(11.2‑14.0)14.5(12.8‑16.3)16.8(14.6‑18.9)20.2(17.2‑22.8)23.2(19.4‑26.4)
4-day 5.07
(4.61‑5.65)
6.11
(5.56‑6.82)
7.74
(7.02‑8.63)
9.13
(8.25‑10.2)
11.2
(10.0‑12.5)
13.0
(11.6‑14.5)
15.0
(13.2‑16.8)
17.2
(15.0‑19.3)
20.5
(17.5‑23.2)
23.4
(19.7‑26.7)
7-day 5.85
(5.38‑6.44)
7.05
(6.48‑7.76)
8.87
(8.13‑9.74)
10.4
(9.49‑11.4)
12.6
(11.4‑13.8)
14.5
(13.1‑15.9)
16.5
(14.8‑18.2)
18.7
(16.6‑20.7)
22.0
(19.1‑24.5)
24.7
(21.2‑27.7)
10-day 6.61
(6.08‑7.22)
7.91
(7.29‑8.66)
9.80
(9.01‑10.7)
11.4
(10.4‑12.5)
13.7
(12.5‑15.0)
15.6
(14.1‑17.1)
17.7
(15.9‑19.4)
19.9
(17.7‑22.0)
23.2
(20.4‑25.7)
25.9
(22.4‑29.0)
20-day 8.86
(8.23‑9.59)
10.6
(9.81‑11.4)
12.9
(11.9‑13.9)
14.8
(13.7‑16.0)
17.5
(16.1‑18.9)
19.7
(18.1‑21.4)
22.1
(20.1‑24.0)
24.6
(22.2‑26.9)
28.2
(25.1‑31.0)
31.2
(27.4‑34.5)
30-day 10.9
(10.2‑11.7)
12.9
(12.1‑13.9)
15.5
(14.6‑16.6)
17.6
(16.5‑18.9)
20.6
(19.1‑22.0)
22.9
(21.2‑24.6)
25.3
(23.3‑27.2)
27.8
(25.4‑30.0)
31.3
(28.2‑34.0)
34.0
(30.4‑37.1)
45-day 13.6
(12.8‑14.5)
16.1
(15.1‑17.2)
19.1
(17.9‑20.3)
21.5
(20.2‑22.9)
24.8
(23.2‑26.5)
27.5
(25.6‑29.3)
30.2
(28.0‑32.3)
33.0
(30.4‑35.5)
36.8
(33.5‑39.8)
39.8
(36.0‑43.3)
60-day 16.3
(15.4‑17.4)
19.2
(18.2‑20.5)
22.5
(21.2‑23.9)
25.1
(23.6‑26.7)
28.6
(26.9‑30.4)
31.3
(29.3‑33.3)
34.0
(31.7‑36.3)
36.8
(34.0‑39.3)
40.4
(37.1‑43.5)
43.1
(39.4‑46.7)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequencyestimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimatesat upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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PF graphical
10/4/22, 2:49 PM Precipitation Frequency Data Server
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Maps & aerials
Small scale terrain
10/4/22, 2:49 PM Precipitation Frequency Data Server
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Large scale terrain
Large scale map
Large scale aerial
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3km
2mi
+
–
100km
60mi
+
–
100km
60mi
10/4/22, 2:49 PM Precipitation Frequency Data Server
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US Department of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
National Water Center
1325 East West Highway
Silver Spring, MD 20910
Questions?: HDSC.Questions@noaa.gov
Disclaimer
+
–
100km
60mi
10/4/22, 2:40 PM Precipitation Frequency Data Server
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=34.3555&lon=-77.8992&data=intensity&units=english&series=pds 1/4
NOAA Atlas 14, Volume 2, Version 3
Location name: Castle Hayne, North Carolina,
USA*
Latitude: 34.3555°, Longitude: -77.8992°
Elevation: 16.51 ft**
* source: ESRI Maps ** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1
Duration Average recurrence interval (years)
1 2 5 10 25 50 100 200 500 1000
5-min 6.20
(5.78‑6.70)
7.37
(6.86‑7.94)
8.62
(8.00‑9.29)
9.60
(8.88‑10.3)
10.8
(9.98‑11.6)
11.8
(10.8‑12.6)
12.7
(11.6‑13.7)
13.7
(12.4‑14.7)
14.9
(13.4‑16.1)
15.9
(14.2‑17.2)
10-min 4.96
(4.61‑5.35)
5.89
(5.48‑6.35)
6.91
(6.41‑7.44)
7.67
(7.10‑8.26)
8.63
(7.96‑9.27)
9.37
(8.59‑10.1)
10.1
(9.22‑10.9)
10.8
(9.82‑11.7)
11.8
(10.6‑12.7)
12.5
(11.2‑13.6)
15-min 4.13
(3.85‑4.45)
4.94
(4.60‑5.33)
5.82
(5.41‑6.27)
6.47
(5.99‑6.97)
7.30
(6.72‑7.84)
7.91
(7.25‑8.50)
8.52
(7.77‑9.16)
9.11
(8.26‑9.81)
9.90
(8.88‑10.7)
10.5
(9.33‑11.3)
30-min 2.83
(2.64‑3.05)
3.41
(3.18‑3.68)
4.14
(3.84‑4.46)
4.69
(4.34‑5.05)
5.40
(4.98‑5.80)
5.95
(5.46‑6.40)
6.52
(5.95‑7.01)
7.09
(6.43‑7.63)
7.87
(7.06‑8.50)
8.50
(7.56‑9.18)
60-min 1.77
(1.64‑1.90)
2.14
(1.99‑2.31)
2.65
(2.46‑2.86)
3.05
(2.83‑3.29)
3.60
(3.32‑3.86)
4.03
(3.70‑4.34)
4.49
(4.10‑4.83)
4.97
(4.51‑5.35)
5.65
(5.07‑6.10)
6.20
(5.52‑6.70)
2-hr 1.05
(0.966‑1.14)
1.28
(1.18‑1.40)
1.63
(1.50‑1.77)
1.92
(1.76‑2.09)
2.34
(2.13‑2.54)
2.70
(2.45‑2.93)
3.09
(2.79‑3.36)
3.51
(3.15‑3.82)
4.15
(3.68‑4.51)
4.69
(4.13‑5.13)
3-hr 0.747
(0.689‑0.819)
0.910
(0.838‑0.997)
1.16
(1.07‑1.27)
1.38
(1.26‑1.51)
1.71
(1.55‑1.86)
1.99
(1.80‑2.17)
2.31
(2.07‑2.51)
2.66
(2.37‑2.89)
3.19
(2.81‑3.47)
3.66
(3.18‑3.99)
6-hr 0.463
(0.427‑0.509)
0.564
(0.520‑0.620)
0.722
(0.663‑0.792)
0.859
(0.786‑0.941)
1.07
(0.968‑1.16)
1.24
(1.12‑1.36)
1.45
(1.30‑1.58)
1.67
(1.48‑1.82)
2.02
(1.77‑2.20)
2.33
(2.01‑2.54)
12-hr 0.270
(0.246‑0.298)
0.329
(0.300‑0.363)
0.424
(0.386‑0.468)
0.507
(0.459‑0.559)
0.632
(0.568‑0.695)
0.744
(0.665‑0.816)
0.870
(0.771‑0.954)
1.01
(0.888‑1.11)
1.23
(1.07‑1.35)
1.43
(1.22‑1.57)
24-hr 0.158
(0.143‑0.178)
0.192
(0.174‑0.216)
0.248
(0.225‑0.279)
0.298
(0.269‑0.334)
0.374
(0.334‑0.418)
0.442
(0.391‑0.494)
0.519
(0.454‑0.581)
0.607
(0.523‑0.679)
0.743
(0.627‑0.837)
0.864
(0.716‑0.977)
2-day 0.093
(0.085‑0.104)
0.113
(0.103‑0.126)
0.145
(0.131‑0.161)
0.172
(0.156‑0.192)
0.215
(0.192‑0.240)
0.252
(0.224‑0.282)
0.294
(0.258‑0.329)
0.341
(0.295‑0.384)
0.414
(0.351‑0.468)
0.478
(0.398‑0.543)
3-day 0.066(0.060‑0.074)0.080(0.073‑0.089)0.102(0.093‑0.114)0.121(0.109‑0.135)0.149(0.134‑0.167)0.174(0.155‑0.195)0.202(0.178‑0.226)0.233(0.202‑0.262)0.281(0.239‑0.317)0.322(0.269‑0.366)
4-day 0.053
(0.048‑0.059)
0.064
(0.058‑0.071)
0.081
(0.073‑0.090)
0.095
(0.086‑0.106)
0.117
(0.105‑0.130)
0.135
(0.120‑0.151)
0.156
(0.138‑0.175)
0.179
(0.156‑0.201)
0.214
(0.183‑0.242)
0.244
(0.205‑0.278)
7-day 0.035
(0.032‑0.038)
0.042
(0.039‑0.046)
0.053
(0.048‑0.058)
0.062
(0.056‑0.068)
0.075
(0.068‑0.082)
0.086
(0.078‑0.095)
0.098
(0.088‑0.108)
0.111
(0.099‑0.123)
0.131
(0.114‑0.146)
0.147
(0.126‑0.165)
10-day 0.028
(0.025‑0.030)
0.033
(0.030‑0.036)
0.041
(0.038‑0.045)
0.047
(0.043‑0.052)
0.057
(0.052‑0.062)
0.065
(0.059‑0.071)
0.074
(0.066‑0.081)
0.083
(0.074‑0.091)
0.097
(0.085‑0.107)
0.108
(0.093‑0.121)
20-day 0.018
(0.017‑0.020)
0.022
(0.020‑0.024)
0.027
(0.025‑0.029)
0.031
(0.029‑0.033)
0.036
(0.034‑0.039)
0.041
(0.038‑0.045)
0.046
(0.042‑0.050)
0.051
(0.046‑0.056)
0.059
(0.052‑0.065)
0.065
(0.057‑0.072)
30-day 0.015
(0.014‑0.016)
0.018
(0.017‑0.019)
0.022
(0.020‑0.023)
0.024
(0.023‑0.026)
0.029
(0.027‑0.031)
0.032
(0.029‑0.034)
0.035
(0.032‑0.038)
0.039
(0.035‑0.042)
0.043
(0.039‑0.047)
0.047
(0.042‑0.052)
45-day 0.013
(0.012‑0.013)
0.015
(0.014‑0.016)
0.018
(0.017‑0.019)
0.020
(0.019‑0.021)
0.023
(0.022‑0.025)
0.025
(0.024‑0.027)
0.028
(0.026‑0.030)
0.031
(0.028‑0.033)
0.034
(0.031‑0.037)
0.037
(0.033‑0.040)
60-day 0.011
(0.011‑0.012)
0.013
(0.013‑0.014)
0.016
(0.015‑0.017)
0.017
(0.016‑0.019)
0.020
(0.019‑0.021)
0.022
(0.020‑0.023)
0.024
(0.022‑0.025)
0.026
(0.024‑0.027)
0.028
(0.026‑0.030)
0.030
(0.027‑0.032)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for agiven duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are notchecked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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Small scale terrain
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Large scale terrain
Large scale map
Large scale aerial
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100km
60mi
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100km
60mi
10/4/22, 2:40 PM Precipitation Frequency Data Server
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National Weather Service
National Water Center
1325 East West Highway
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Questions?: HDSC.Questions@noaa.gov
Disclaimer
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100km
60mi
3) Erosion Control Calculations
BASIN NAME
BASIN TYPE
TOTAL DRAINAGE AREA 1.34 acres
Tc (TIME OF CONCENTRATION) 5 min
C VALUE 0.16
I (10 YEAR STORM) 7.15 in/hr
SURFACE AREA CALCULATION:
Q10 = CIA 2 cfs
SURFACE AREA (AC) = 325 SF * Q10 (CFS)
SURFACE AREA REQUIRED 498 ft2
RECTANGLE BASIN PROVIDED 35' X 106'
SURFACE AREA PROVIDED 4,299 ft2
BASIN VOLUME CALCULATION:
BASIN VOLUME DESIGN = 1,800 ft3/acre
BASIN VOLUME REQUIRED 2,412 ft3
BASIN VOLUME PROVIDED 11,502 ft3
TOP OF EMBANKMENT ELEVATION 19
EMBANKMENT WIDTH 5 ft
BOTTOM ELEVATION 14.00
EMERGENCY SPILLWAY ELEVATION 18.00
BASIN DEPTH 4 ft
EMERGENCY SPILLWAY WIDTH 15 ft
SEDIMENT STORAGE VOLUME 2,210 ft3
@ 18'
PROVIDE 3 BAFFLES
SKIMMER SIZE 1.5 inch
ORIFICE DIAMETER 1 inch
DEWATERING TIME 2.95 days
BASIN 1
SKIMMER
BASIN NAME
BASIN TYPE
TOTAL DRAINAGE AREA 0.87 acres
Tc (TIME OF CONCENTRATION) 5 min
C VALUE 0.50
I (10 YEAR STORM) 7.15 in/hr
SURFACE AREA CALCULATION:
Q10 = CIA 3 cfs
SURFACE AREA (AC) = 325 SF * Q10 (CFS)
SURFACE AREA REQUIRED 1,011 ft2
RECTANGLE BASIN PROVIDED 45' X 102'
SURFACE AREA PROVIDED 4,505 ft2
BASIN VOLUME CALCULATION:
BASIN VOLUME DESIGN = 1,800 ft3/acre
BASIN VOLUME REQUIRED 1,566 ft3
BASIN VOLUME PROVIDED 11,980 ft3
TOP OF EMBANKMENT ELEVATION 21
EMBANKMENT WIDTH 5 ft
BOTTOM ELEVATION 16.00
EMERGENCY SPILLWAY ELEVATION 20.00
BASIN DEPTH 4 ft
EMERGENCY SPILLWAY WIDTH 15 ft
SEDIMENT STORAGE VOLUME 3,018 ft3
@ 20'
PROVIDE 3 BAFFLES
SKIMMER SIZE 2 inch
ORIFICE DIAMETER 0.75 inch
DEWATERING TIME 2.95 days
BASIN 2
SKIMMER
DITCH NAME
TOP WIDTH "A" 6 FT
MIN. DITCH DEPTH (FT) "B" 1 FT
BOTTOM WIDTH (FT) "C" 0.0
SIDE SLOPE "D" 3:1
LINER TYPE North American Green, S75
TEMPORARY DIVERSION DITCH: EC108
DITCH NAME
TOP WIDTH "A" 6 FT
MIN. DITCH DEPTH (FT) "B" 1 FT
BOTTOM WIDTH (FT) "C" 0.0
SIDE SLOPE "D" 3:1
LINER TYPE North American Green, S75
TEMPORARY DIVERSION DITCH: EC109
DITCH NAME
TOP WIDTH "A" 6.6 FT
MIN. DITCH DEPTH (FT) "B" 1.1 FT
BOTTOM WIDTH (FT) "C" 0.0
SIDE SLOPE "D" 3:1
LINER TYPE North American Green, S75
TEMPORARY DIVERSION DITCH: EC110
DITCH NAME
TOP WIDTH "A" 4.98 FT
MIN. DITCH DEPTH (FT) "B" 0.83 FT
BOTTOM WIDTH (FT) "C" 0.0
SIDE SLOPE "D" 3:1
LINER TYPE North American Green, S75
TEMPORARY DIVERSION DITCH: EC111
RIPRAP SIZING CHART
EC215 CLASS B
4.5' W X 9' L X 18" D
EC216 CLASS B
3.8' W X 7.5' L X 18" D
RIPRAP SIZING CHART
EC217 CLASS B
7.5' W X 15' L X 18" D
0 CLASS B
3.8' W X 7.5' L X 18" D