20081831 Ver 1_401 Application_20081208

? ? ? Kimley-Horn
and Associates, Inc.
December 15, 2008
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Attn: Cyndi Karoly
2321 Crabtree Blvd., Suite 250
Raleigh, NC 27604
Re: Twelve Mile Creek Sewer Diversion Force Main
NWP # 12 Application Submittal
Monroe, North Carolina
Dear Ms. Karoly:
¦
Suite 300
4651 Charlotte Park Drive
Charlotte, North Carolina
28217
n ,n n l p `-? 1
Enclosed for your review is a copy of a Section 401 Pre-Construction Notification
pursuant to Nationwide Permit # 12 for the above referenced project. Included in the
submittal package are three bound application forms, a copy of the Agent
Authorization Form, and three full size plan sets.
If there is any additional information you need or any way we can assist in
expediting the processing of this application, please do not hesitate to contact me at
[phone] or by email at [e-mail].
Very truly yours,
Kimley-Horn and Associates, Inc.
Tommy Cousins
Environmental Scientist
'u7
DEL I r 2008
DENT. iY
V'F,TLANDS AND S'iORt PATER BRANCK
¦
TEL [phone]
FAX [phone]
AGENT AUTHORIZATION FORM
Name: Scott Huneycutt
Address: 500 N. Main Street, Suite 500, Monroe, NC 28112
Phone: [phone]
Project Name/Description: Twelve Mile Creek Sewer Diversion Pump Station and Force
Main
Date: December 11, 2008
The Department of the Army
U.S. Army Corps of Engineers, Wilmington District
2 0 n 3 1 8 3 1
Attention: Steve Chapin
Field Office: Asheville
Re: Wetland Related Consulting and Permitting
To Whom It May Concern:
I, the current representative, hereby designate and authorize Kimley-Horn and
Associates, Inc. to act in my/our behalf as my/our agent solely for the purpose of
processing of Section 404 permits and Section 401 Water Quality Certifications
applications and to furnish upon request supplemental information in support of
applications, etc. from this day forward until successful completion of the permitting
process or revocation by the owner.
Authorized this the _ day of PEsegM 3e9 ,
Print Representatives Name
ZooB
epresentative's i ature
CC: Ms, Cyndi Karoly
N.C. Wetlands Unit
1650 Mail Service Center
Raleigh, N. C. 27699-1650

i

¦
Pre-Construction Notification Application Form
for Nationwide Permit 12
Twelve Mile Creek Sewer Diversion Pump
Station and Force Main
Union County Public Works
Union County, North Carolina
Prepared for:
N.C. Division of Water Quality
Raleigh, North Carolina
December 2008
OKimley-Horn and Associates, Inc. 2008
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_ and Associates, Inc.
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Kimley-Horn
. and Associates, Inc.
Project Summary Sheet
Project Name: Twelve Mile Creek Sewer Diversion Force Main
Applicant Name and Address: Union County Public Works (Scott Huneycutt
500 N. Main Street. Suite 500
Monroe. NC 28112
Telephone Number: [phone]
Type of Request: ® Nationwide PCN (NWP # 12) ? Individual Permit Application
? Jurisdictional Determination ? Other:
Included Attachments: ® Project Plans ® USGS Map ? NRCS Soil Survey
® Agent Authorization ? Delineation Sketch ? Delineation Survey
? Data Forms (Up & Wet) ® NCDWQ Stream Forms ? USACE Stream Forms
? NCEEP Confirmation ? Aerial Photo ® Site Photos
? Agency Correspondence ? Other: ? Other:
Check if applicable: ? CAMA County ? Trout County ? Isolated Waters
? Section 7, ESA ? Section 106, NHPA ? EFH
? Mitigation Proposed (? NC EEP ? On-Site ? Off-Site ? Other)
County: Union Nearest City/Town: Monroe
Waterway: Twelve Mile Creek River Basin: Catawba
H.U.C.: 03050103 USGS Quad Name: Catawba NE
Property Size (acres): N/A Approx. Size of Jurisdiction on Site (acres): N/A
Site Coordinates (in decimal degrees): See PCN °N See PCN °W
Project Location: See PCN
Site Description: See PCN
Impact Summary (if applicable): Three temporary stream crossings with rip rap stabilization
O
en Water Wetland Stream Channel
NWP
# p
(acres) (acres) Intermittent and/or Unimportant
Aquatic Function Perennial and/or Important
Aquatic Function
Tem Perm T P Temp. Perm. Tem Perm.
p. . emp. erm. If ac if ac If ac If Ac
12 0 0 0 0 0 0 0 0 60 .027 0 0
12 0 0 0 0 0 0 0 0 0 0
12 0 0 0 0 0 0 0 0 0 0
Total 0 0 0 0 0 0 0 0 0 0
Total Permanent Impact to Waters of the U.S. (acres) 0
Kimley-Horn Contact: Tommy Cousins
¦
4651 Charlotte Park Dr. Suite 300
Charlotte, North Carolina
28217
Direct Number: 704 319-7688
¦
TEL [phone]
FAX [phone]
TABLE OF CONTENTS
A. NARRATIVE
B. PRE-CONSTRUCTION NOTIFICATION
(PCN) APPLICATION FORM
C. SITE LOCATION MAPS
SITE VICINITY MAP
SOILS MAP
USGS TOPOGRAPHIC MAP
TEMPORARY STREAM IMPA CT 41
TEMPORAR Y STREAM IMPA CT #2
TEMPORARY STREAMIMPA CT #3
D. REFERENCE MATERIALS
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Kimley-Horn and Associates, Inc.
A. NARRATIVE
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Kimley-Horn and Associates, Inc.
? M " Kimley-Horn
and Associates, Inc.

NARRATIVE

Date: December 2008
'
Subject: Union County Public Works
Twelve Mile Creek Sewer Diversion Force Main
' Union County, NC
Project Description
The purpose of the above referenced project is to construct approximately 2.9 miles (15,125 LF) of 18"
diameter force main along Cureton Parkway and Waxhaw-Marvin Road. The described alignment is
located in Union County. The project will disturb approximately 6.9 acres of land during the construction
period. The proposed force main is being constructed in order to divert sewer flow from the Twelve Mile
Treatment Plant and will tie into an existing 16" force main north of Crane Road. The existing force main
ultimately takes flow to the McAlpine WWTP.
Site Description
' The proposed force main alignment begins at the Twelve Mile Creek WWTP and continues along the south
side of Cureton parkway. From Cureton Parkway it continues along the east side of Waxhaw-Marvin Road.
The proposed force main alignment will cross three jurisdictional streams: Cowhorn Branch, Tarkhill
' Branch, and an unnamed tributary to Twelve Mile Creek. The Cowhorn Branch stream crossing will be on
Union County Public Works property. The Tarkhill Branch stream crossing will be located in a permanent
utility easement and the tributary to Twelve Mile Creek will require obtaining a permanent utility
easement. All streams are located in the Catawba River basin.
B. PRE-CONSTRUCTION NOTIFICATION
(PCN) APPLICATION FORM
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Kimley-Horn and Associates, Inc.

Office Use Only: Form Version March 05
USACE Action ID No. DWQ No. 2 0 0 8 1 8 3 1
(It any particular item is not applicable to this project, please enter "Not Applicable" or "N/A".)
1. Processing
1. Check all of the approval(s) requested for this project:
® Section 404 Permit ? Riparian or Watershed Buffer Rules
' ? Section 10 Permit ? Isolated Wetland Permit from DWQ
® 401 Water Quality Certification ? Express 401 Water Quality Certification
i 2. Nationwide, Regional or General Permit Number(s) Requested: Nationwide Permit 12
I3. If this notification is solely a courtesy copy because written approval for the 401 Certification
is not required, check here:
' 4. If payment into the North Carolina Ecosystem Enhancement Program (NCEEP) is proposed
for mitigation of impacts, attach the acceptance letter from NCEEP, complete section VIII,
and check here: ?
5. If your project is located in any of North Carolina's twenty coastal counties (listed on page
4), and the project is within a North Carolina Division of Coastal Management Area of
Environmental Concern (see the top of page 2 for further details), check here: ?
II. Applicant Information p E @ H? 0W_ LR
' 1. Owner/Applicant Information
DEC 1 i 2008 Name: _ Union County Public Works (Scott Huneycutt)
' Mailing Address: 500 N. Main Street Suite 500 DENR-WATER QUALITY
Monroe, NC 28112 YiETtANDSAND CM
Telephone Number:_ [phone] Fax Number: [phone]
E-mail Address: ScottHuneycuttgco.union.nc.us
2. Agent/Consultant Information (A signed and dated copy of the Agent Authorization letter
must be attached if the Agent has signatory authority for the owner/applicant.)
Name: Tommy Cousins
Company Affiliation: Kimley-Horn and Associates
Mailing Address: 4651 Charlotte Park Dr., Suite 300
' Charlotte NC 28217
' Telephone Number: [phone] Fax Number: [phone]
E-mail Address: tommy.cousinsgkimley-hom.com
III. Project Information
Updated 11/1/2005
Page 1 of 8
Attach a vicinity map clearly showing the location of the property with respect to local
landmarks such as towns, rivers, and roads. Also provide a detailed site plan showing property
boundaries and development plans in relation to surrounding properties. Both the vicinity map
and site plan must include a scale and north arrow. The specific footprints of all buildings,
impervious surfaces, or other facilities must be included. If possible, the maps and plans should
include the appropriate USGS Topographic Quad Map and NRCS Soil Survey with the property
boundaries outlined. Plan drawings, or other maps may be included at the applicant's discretion,
so long as the property is clearly defined. For administrative and distribution purposes, the
USACE requires information to be submitted on sheets no larger than 11 by 17-inch format;
however, DWQ may accept paperwork of any size. DWQ prefers full-size construction
drawings rather than a sequential sheet version of the full-size plans. If full-size plans are
reduced to a small scale such that the final version is illegible, the applicant will be informed that
the project has been placed on hold until decipherable maps are provided.
1. Name of project: Twelve Mile Creek Sewer Diversion Force Main
2. T.I.P. Project Number or State Project Number (NCDOT Only): Not Applicable
3. Property Identification Number (Tax PIN): DOT Right-of-Way and multiple parcels
4. Location
County: Union Nearest Town: Charlotte
Subdivision name (include phase/lot number): Not Applicable
Directions to site (include road numbers/names, landmarks, etc.): From Charlotte go south
on I-77 to 1-485 east. Take exit 57 for State Hwy 16/Providence Road. Turn right at NC-
16/Providence Rd. Turn right at Gray Byrum (NC 1306) and left at Waxhaw-Marvin Road to
the intersection of Waxhaw-Marvin Road and Kensington Dr.
5. Site coordinates (For linear projects, such as a road or utility line, attach a sheet that
separately lists the coordinates for each crossing of a distinct waterbody.)
Stream Crossing 1 34.9694 ON 80.7996 °W
Stream Crossing 2 34.9690 ON 80.7957 °W
Stream Crossing 3 34.9502 ON 80.7664 °W
6. Property size (acres): Linear Utility Project
7. Name of nearest receiving body of water: Twelve Mile Creek (DWQ Index 03-08-38)
8. River Basin: Catawba River Basin
(Note - this must be one of North Carolina's seventeen designated major river basins. The
River Basin map is available at http://h2o.enr.state.nc.us/admin/maps/.)
9. Describe the existing conditions on the site and general land use in the vicinity of the project
at the time of this application: Project area is residential. See attached Site Description.
Updated 11/1/2005
Page 2 of 8

10. Describe the overall project in detail, including the type of equipment to be used:
See attached Project Description Equipment includes a backhoe and all other necessary
' equipment to install the force main. See the attached reference material for more details
11. Explain the purpose of the proposed work: To provide better sewer service to the residents
' of Union County.
' IV. Prior Project History
If jurisdictional determinations and/or permits have been requested and/or obtained for this
' project (including all prior phases of the same subdivision) in the past, please explain. Include
the USACE Action ID Number, DWQ Project Number, application date, and date permits and
certifications were issued or withdrawn. Provide photocopies of previously issued permits,
certifications or other useful information. Describe previously approved wetland, stream and
buffer impacts, along with associated mitigation (where applicable). If this is a NCDOT project,
list and describe permits issued for prior segments of the same T.I.P. project, along with
' construction schedules. No jurisdictional determinations or permits have been requested for this
proiect.
V. Future Project Plans
Are any future permit requests anticipated for this project? If so, describe the anticipated work,
and provide justification for the exclusion of this work from the current application.
No future permit requests are anticipated
' VI. Proposed Impacts to Waters of the United States/Waters of the State
It is the applicant's (or agent's) responsibility to determine, delineate and map all impacts to
' wetlands, open water, and stream channels associated with the project. Each impact must be
listed separately in the tables below (e.g., culvert installation should be listed separately from
riprap dissipater pads). Be sure to indicate if an impact is temporary. All proposed impacts,
' permanent and temporary, must be listed, and must be labeled and clearly identifiable on an
accompanying site plan. All wetlands and waters, and all streams (intermittent and perennial)
' should be shown on a delineation map, whether or not impacts are proposed to these systems.
Wetland and stream evaluation and delineation forms should be included as appropriate.
Photographs may be included at the applicant's discretion. If this proposed impact is strictly for
' wetland or stream mitigation, list and describe the impact in Section VIII below. If additional
space is needed for listing or description, please attach a separate sheet.
1. Provide a written description of the proposed impacts: Three jurisdictional streams will
be crossed. The streams will be open cut and the force main will be installed below the bed of the
stream. Rip rap will be placed such that the original contours of the stream bank are maintained
' See attached Project Description and Sediment and Erosion Control Practices
Updated 11/1/2005
Page 3 of 8
2. Individually list wetland impacts. Types of impacts include, but are not limited to
mechanized clearing, grading, fill, excavation, flooding, ditching/drainage, etc. For dams,
separately list impacts due to both structure and floodinu.
Wetland Impact Type of Wetland Located within Distance to Area of
Site Number Type of Impact (e.g., forested, marsh, 100-year Nearest Impact
(indicate on map) herbaceous, bog, etc.) Floodplain Stream (acres)
es/no) linear feet)

Total Wetland Impact (acres) 0
3. List the total acreage (estimated) of all existing wetlands on the property: 0 (Project Area)
4. Individually list all intermittent and perennial stream impacts. Be sure to identify temporary
impacts. Stream impacts include, but are not limited to placement of fill or culverts, dam
construction, flooding, relocation, stabilization activities (e.g., cement walls, rip-rap, crib
walls, gabions, etc.), excavation, ditching/straightening, etc. If stream relocation is proposed,
plans and profiles showing the linear footprint for both the original and relocated streams
must be included. To calculate acreage, multiply length X width. then divide by 43.560.
Stream Impact Perennial or Average Impact Area of
Number Stream Name Type of Impact Intermittent? Stream Width Length Impact
(indicate on ma) Before Impact (linear feet) (acres)
Temporary Stream
1 Cowhom Branch Crossing and rip rap Perennial 9' 25 .005
stabilization
Temporary Stream
2 Tarkhill Branch Crossing and rip rap Perennial 30' 20 .014
stabilization
Unnamed tributary Temporary Stream 23'
3 to Twelve Mile Crossing and rip rap Perennial 15 .008
Creek stabilization
Total Stream Impact (by length and acreage) 60 .027
5. Individually list all open water impacts (including lakes, ponds, estuaries, sounds, Atlantic
Ocean and any other water of the U.S.). Open water impacts include, but are not limited to
fill. excavation. dredging. flooding. drainage. bulkheads. etc.
Open Water Impact Name Waterbody Type of Waterbody Area of
Site Number applicable) le)
(if ap Type of Impact (lake, pond, estuary, sound, bay, Impact
(indicate on ma) ocean, etc.) (acres)

Total Open Water Impact (acres) 0
6. List the cumulative impact to all Waters of the U.S. resulting from the moiect:
Stream Impact (acres): .027
Wetland Impact (acres): 0
Open Water Impact (acres): 0
Total Impact to Waters of the U.S. (acres) 0
Updated 11/1/2005
Page 4of8

I Total Stream Impact (linear feet): 60
7. Isolated Waters
' Do any isolated waters exist on the property? ? Yes ® No
Describe all impacts to isolated waters, and include the type of water (wetland or stream) and
the size of the proposed impact (acres or linear feet). Please note that this section only
applies to waters that have specifically been determined to be isolated by the USACE.
' 8. Pond Creation
If construction of a pond is proposed, associated wetland and stream impacts should be
' included above in the wetland and stream impact sections. Also, the proposed pond should
be described here and illustrated on any maps included with this application.
Pond to be created in (check all that apply): ? uplands ? stream ? wetlands
' Describe the method of construction (e.g., dam/embankment, excavation, installation of
draw-down valve or spillway, etc.):
Proposed use or purpose of pond (e.g., livestock watering, irrigation, aesthetic, trout pond,
local stormwater requirement, etc.):
Current land use in the vicinity of the pond:
Size of watershed draining to pond: Expected pond surface area:
' VII. Impact Justification (Avoidance and Minimization
Specifically describe measures taken to avoid the proposed impacts. It may be useful to provide
information related to site constraints such as topography, building ordinances, accessibility, and
financial viability of the project. The applicant may attach drawings of alternative, lower-impact
site layouts, and explain why these design options were not feasible. Also discuss how impacts
were minimized once the desired site plan was developed. If applicable, discuss construction
techniques to be followed during construction to reduce impacts. All stream impacts will be
' temporary. Channels will be restored to existing contours The channel banks will be stabilized
with rip rap. Stream channels will be crossed at 90° angles See attached Sediment and Erosion
' Control Practices.
VIII. Mitigation
' DWQ - In accordance with 15A NCAC 2H .0500, mitigation may be required by the NC
Division of Water Quality for projects involving greater than or equal to one acre of impacts to
freshwater wetlands or greater than or equal to 150 linear feet of total impacts to perennial
streams.
USACE - In accordance with the Final Notice of Issuance and Modification of Nationwide
Permits, published in the Federal Register on January 15, 2002, mitigation will be required when
necessary to ensure that adverse effects to the aquatic environment are minimal. Factors
' including size and type of proposed impact and function and relative value of the impacted
aquatic resource will be considered in determining acceptability of appropriate and practicable
mitigation as proposed. Examples of mitigation that may be appropriate and practicable include,
Updated 11/1/2005
' Page 5 of 8
but are not limited to: reducing the size of the project; establishing and maintaining wetland
and/or upland vegetated buffers to protect open waters such as streams; and replacing losses of
aquatic resource functions and values by creating, restoring, enhancing, or preserving similar
functions and values, preferable in the same watershed.
If mitigation is required for this project, a copy of the mitigation plan must be attached in order
for USACE or DWQ to consider the application complete for processing. Any application
lacking a required mitigation plan or NCEEP concurrence shall be placed on hold as incomplete.
An applicant may also choose to review the current guidelines for stream restoration in DWQ's
Draft Technical Guide for Stream Work in North Carolina, available at
http://h2o.enr.state.nc.us/ncwetlands/strmgide.html.
1. Provide a brief description of the proposed mitigation plan. The description should provide
as much information as possible, including, but not limited to: site location (attach directions
and/or map, if offsite), affected stream and river basin, type and amount (acreage/linear feet)
of mitigation proposed (restoration, enhancement, creation, or preservation), a plan view,
preservation mechanism (e.g., deed restrictions, conservation easement, etc.), and a
description of the current site conditions and proposed method of construction. Please attach
a separate sheet if more space is needed.
No mitigation is anticipated for temporary impacts.
2. Mitigation may also be made by payment into the North Carolina Ecosystem Enhancement
Program (NCEEP). Please note it is the applicant's responsibility to contact the NCEEP at
[phone] to determine availability, and written approval from the NCEEP indicating
that they are will to accept payment for the mitigation must be attached to this form. For
additional information regarding the application process for the NCEEP, check the NCEEP
website at hqp://h2o.enr.state.nc.us/wrp/index.htm. If use of the NCEEP is proposed, please
check the appropriate box on page five and provide the following information:
Amount of stream mitigation requested (linear feet): N/A
Amount of buffer mitigation requested (square feet): N/A
Amount of Riparian wetland mitigation requested (acres): N/A
Amount of Non-riparian wetland mitigation requested (acres): N/A
Amount of Coastal wetland mitigation requested (acres): N/A
IX.
Environmental Documentation (required by DWQ)
Does the project involve an expenditure of public (federal/state/local) funds or the use of
public (federal/state) land? Yes ® No ?
2. If yes, does the project require preparation of an environmental document pursuant to the
requirements of the National or North Carolina Environmental Policy Act (NEPA/SEPA)?
Updated 11/1/2005
Page 6 of 8

t Note: If you are not sure whether a NEPA/SEPA document is required, call the SEPA
coordinator at [phone] to review current thresholds for environmental documentation.
Yes ? No
3. If yes, has the document review been finalized by the State Clearinghouse. If so, please
' attach a copy of the NEPA or SEPA final approval letter. Yes ? No ?
X. Proposed Impacts on Riparian and Watershed Buffers (required by DWQ)
It is the applicant's (or agent's) responsibility to determine, delineate and map all impacts to
required state and local buffers associated with the project. The applicant must also provide
' justification for these impacts in Section VII above. All proposed impacts must be listed herein,
and must be clearly identifiable on the accompanying site plan. All buffers must be shown on a
map, whether or not impacts are proposed to the buffers. Correspondence from the DWQ
Regional Office may be included as appropriate. Photographs may also be included at the
applicant's discretion.
' 1. Will the project impact protected riparian buffers identified within 15A NCAC 2B .0233
(Meuse), 15A NCAC 2B .0259 (Tar-Pamlico), 15A NCAC 02B .0243 (Catawba) 15A NCAC
2B .0250 (Randleman Rules and Water Supply Buffer Requirements), or other (please
' identify )? Yes ? No
2. If "yes", identify the square feet and acreage of impact to each zone of the riparian buffers.
If buffer mitigation is required calculate the required amount of mitigation by applying the
buffer multipliers.
Zone* Impact Multiplier Required
(square feet) Mitigation
1 3 (2 for Catawba) 0
2 1.5 0
' Total 0
* Zone 1 extends out 30 feet perpendicular from the top of the near bank of channel; Zone 2 extends an
additional 20 feet from the edge of Zone 1.
3. If buffer mitigation is required, please discuss what type of mitigation is proposed (i.e.,
Donation of Property, Riparian Buffer Restoration / Enhancement, or Payment into the
Riparian Buffer Restoration Fund). Please attach all appropriate information as identified
within 15A NCAC 2B .0242 or .0244, or .0260. No buffer mitigation is anticipated.
XI. Stormwater (required by DWQ)
Describe impervious acreage (existing and proposed) versus total acreage on the site. Discuss stormwater
controls proposed in order to protect surface waters and wetlands downstream from the property. If
percent impervious surface exceeds 20%, please provide calculations demonstrating total proposed
impervious level. This project will not result in an increase in impervious area Proposed storm water
Updated 11/1/2005
Page 7 of 8
controls needed to protect surface waters include temporary construction entrances check dams, silt
fence and inlet protection
XII. Sewage Disposal (required by DWQ)
Clearly detail the ultimate treatment methods and disposition (non-discharge or discharge) of
wastewater generated from the proposed project, or available capacity of the subject facility.
No wastewater will be generated during the completion of the proposed project
XIII. Violations (required by DWQ)
Is this site in violation of DWQ Wetland Rules (15A NCAC 2H .0500) or any Buffer Rules?
Yes ? No
Is this an after-the-fact permit application? Yes ? No
XIV. Cumulative Impacts (required by DWQ)
Will this project (based on past and reasonably anticipated future impacts) result in additional
development, which could impact nearby downstream water quality? Yes ? No
If yes, please submit a qualitative or quantitative cumulative impact analysis in accordance with
the most recent North Carolina Division of Water Quality policy posted on our website at
http://h2o.enr.state.nc.us/ncwetlands. If no, please provide a short narrative description:
The force main will provide better service to existing residents. Future developments may impact
streams and wetlands however this force is conveying existing wastewater flow.
XV. Other Circumstances (Optional):
It is the applicant's responsibility to submit the application sufficiently in advance of desired
construction dates to allow processing time for these permits. However, an applicant may
choose to list constraints associated with construction or sequencing that may impose limits on
work schedules (e.g., draw-down schedules for lakes, dates associated with Endangered and
Threatened Species, accessibility problems, or other issues outside of the applicant's control).
Applicant/Agent's Signature Date
(Agent's signature is valid only if an authorization letter from the applicant is provided.)
Updated 11/1/2005
Page 8 of 8
C. FIGURES
SITE VICINITY MAP
SOILS MAP
USGS TOPOGRAPHIC MAP
TEMPORARY STREAMIMPA CT 41
TEMPORAR Y STREAMIMPACT 42
TEMPORARY STREAM IMPACT #3
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Title Location Map
Prepared For.
Project Twelve Mile Creek Sewer Diversion Pump Station and Force Main
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Prepared For
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9 Union County, North Carolina
Date Project Number Figure
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PIN# 06162001
DB 351; PG 482
s,.. SS-MH
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n-486.18'
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EXISTING 10" /
FORCE MAIN
\
TEMP ARV
l STIR M CROSSING
365 SF RIP RAP
EXISTING 14"
FORCE MAIN l
6? PROPOSED 18"
DIP FORCE MAIN
? s
F F
V X
STREAM CROSSING #1
SCALE 1•=q0•

DESIGNED BY GLH
P
=11 Kimley-Hom

and AssoctiateS
Inc
DATE
11-12-08
UNION COUNTY PUBLIC WORKS DESIGN ENGINEER:
ERICA VANTASSEL
SHEET NUMBER
DRAWN BY NJM ,
.
TWELVE MILE CREEK SEWER P.E UCENSE NUMBER:
CHECKED BY EVT 4651 CHARLOTTE PARK DRIVE, SUITE 300,
CHARLOTTE
NORTH CAROLINA 25217 PROJECT NO. 1
, 015127003 DIVERSION FORCE MAIN
PHONE: [phone] FAX: [phone]
ms aocumem, togetner wnn the cwnc" ana aesigns presentee herein, as an instrument of s"ce, is intended only for the speciftc purpose and client for which It was prepared. Reuse of

Glover
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m
148-'- n
00 PUE X149+00 150+00
EXISTING 10"
FORCE MAIN See 08 2081; PG 5
For Sanitary Sewer Easement
(Easement does not fit physical
location of force main tine) I
STREAM CROSSING #2
SCALE 1"-40
DESIGNED BY GLH Jp ? Kim le liom
Y DA's UNION COUNTY PUBLIC WORKS DESIGN ENGINEER:
ERICA VANTASSEL SHEET NUMBER
and Associates, Inc. „-,2-oa
DRANK BY NAM
TWELVE MILE CREEK SEWER P.E. LICENSE NUMBER:
2
CHECKED BY EVT 4651 CHARLOTTE PAR. SUITE 300. PROJECT No.
CHAR NORTH CAROLINA
015127003
DIVERSION FORCE MAIN
PHONE: [phone] FAX: [phone]
This dog mt. taaether with the ro ceots and designs oresented herein. as an instrument of eerrice. is intended eniv for the seecific aurnese en d di.nf for which 14 wn. --A R..... of

1

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TEMPORARY
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ee DB 20767; PG 134 See DS 3017; PG 414
' or Sanitary Sewer Easement / For Sanitary Sewer Easement
(Easement does not fit physical (Easement does not fit physical
location of force main line) I location of force main line)

PROPOSED 18 DI FORCE MAIN
REMOVE AND REPLACE
EXISTING 10" FORCE MAIN

STREAM CROSSINGS
ENGINEER: SHEET NUMBER
' SCALE 1•.4p' Kimley-Horn DATE UNION COUNTY PUBLIC WORKS .1. ERICA VANTASSEL
DESIGNED BY GLH
DRANK BY _ ? and Associates, Inc. 11_12_08
NJM C 2008 P.E. LICENSE NUMBER:
1 CHECKED BY EVr 4651 CHARLOTTE PARK DRIVE, SUITE 300, PROJECT NO. TWELVE E MILE CREEK SEWER
CHARLOTTE, NORTH CAROLINA 28217 015127003 DIVERSION FORCE MAIN
PHONE: [phone] FAX: [phone]
This document, together with the concepts, and designs presented herein, as an Instrument of service, Is intended only for the specific purpose and client for which It was prepared. Reuse of
D. REFERENCE MATERIALS
Kimley-Horn and Associates, Inc.

Practice Standards and Specifications
Definition A temporary sediment control measure consisting of fabric buried at the
bottom, stretched, and supported by posts.
Purpose To retain sediment from small disturbed areas by reducing the velocity of
sheet flows to allow sediment deposition.
Conditions Where Below small-disturbed areas that are less then 14 acre per 100 feet of fence.
Practice Applies Where runoff can be stored behind the sediment fence without damaging the
fence or the submerged area behind the fence.
Do not install sediment fences across streams, ditches, or waterways, or
other areas of concentrated flow.
Sediment fence should be placed along topographic elevation contours, where
it can intercept stormwater runoff that is in dispersed sheet flow. Sediment
fence should not be used alone below graded slopes greater than 10 feet in
height.
Planning A sediment fence is a system to retain sediment on the construction site. The
Considerations fence retains sediment primarily by retarding flow and promoting deposition.
In operation, generally the fence becomes clogged with fine particles, which
reduce the flow rate. This causes a pond to develop behind the fence. The
designer should anticipate ponding and provide sufficient storage areas and
overflow outlets to prevent flows from overtopping the fence. Since sediment
fences are not designed to withstand high water levels, locate them so that
only shallow pools can form. Tie the ends of a sediment fence into higher
ground to prevent flow around the end of the fence before the pool reaches
design level. Curling each end of the fence uphill in a "J" pattern may be
appropriate to prevent end flow. Provide stabilized outlets to protect the fence
system and release stone flows that exceed the design storm.
Deposition occurs as the storage pool forms behind the fence. The designer can
direct flows to specified deposition areas through appropriate positioning of
the fence or by providing an excavated area behind the fence. Plan deposition
areas at accessible points to promote routine cleanout and maintenance. Show
deposition areas in the erosion and sedimentation control plan. A sediment
fence acts as a diversion if placed slightly off the contour. A maximum slope
of 2 percent is recommended. This technique may be used to control shallow,
uniform flows from small disturbed areas and to deliver sediment-laden water
to deposition areas. The anchoring of the toe of the fence should be reinforced
with 12 inches of NC DOT #5 or #57 washed stone when flow will run parallel
to the toe of the fence.
Sediment fences serve no function along ridges or near drainage divides where
there is little movement of water. Confining or diverting runoff unnecessarily
with a sediment fence may create erosion and sedimentation problems that
would not otherwise occur.
Rev. 6/06 6.62.1

Straw barriers have only a 0-20% trapping efficiency and are inadequate. Straw
bales may not be used in place of sediment fence. Prefabricated sediment fence
with the fabric already stapled to thin wooden posts does not meet minimum
standards specified later in this section.
Anchoring of sediment fence is critical. The toe of the fabric must be anchored
in a trench backfilled with compacted earth. Mechanical compaction must be
provided in order for the fence to effectively pond runoff.
Design Criteria Ensure that drainage area is no greater than '/< acre per 100 feet of fence. This
is the maximum drainage area when the slope is less than 2 percent. Where
all runoff is to be stored behind the fence, ensure that the maximum slope
length behind a sediment fence does not exceed the specifications shown in
Table 6.62a. The shorter slope length allowed for steeper slopes will greatly
reduce the maximum drainage area. For example, a 10-20 % slope may have
a maximum slope length of 25 feet. For a 100-foot length of sediment fence,
the drainage area would be 25ft X 100ft = 2500sq.ft., or 0.06 acres.
Table 6.62a Maximum
Slope Length and Slope for
which Sediment Fence is
Applicable
Slope Slope Length (ft) Maximum Area (W)
<2% 100 10,000
2 to 5% 75 7,500
5 to 10% 50 5,000
10 to 20% 25 2,500
>20% 15 1,500
Make the fence stable for the 10-year peak storm runoff.
Ensure that the depth of impounded water does not exceed 1.5 feet at any point
along the fence.
If non-erosive outlets are provided, slope length may be increased beyond
that shown in Table 6.62x, but runoff from the area should be determined and
bypass capacity and erosion potential along the fence must be checked. The
velocity of the flow at the outlet or along the fence should be in keeping with
Table 8.05d, Appendix 8.05.
Provide a riprap splash pad or other outlet protection device for any point
where flow may overtop the sediment fence, such as natural depressions or
swales. Ensure that the maximum height of the fence at a protected, reinforced
outlet does not exceed 2 feet and that support post spacing does not exceed 4
feet.
The design life of a synthetic sediment fence should be 6 months.
Construction MATERIALS
Specifications 1. Use a synthetic filter fabric of at least 95% by weight of polyolefins or
polyester, which is certified by the manufacturer or supplier as conforming to
the requirements in ASTM D 6461, which is shown in part in Table 6.62b.
Synthetic filter fabric should contain ultraviolet ray inhibitors and stabilizers
to provide a minimum of 6 months of expected usable construction life at a
temperature range of 0 to 1201 F.
6.62.2 Rev. 6106
1

[1,

IJ I

Practice Standards and Specifications
2. Ensure that posts for sediment fences are 1.33 lb/linear ft steel with
a minimum length of 5 feet. Make sure that steel posts have projections to
facilitate fastening the fabric.
3. For reinforcement of standard strength filter fabric, use wire fence with a
minimum 14 gauge and a maximum mesh spacing of 6 inches.
TahlP 6.62h Snecifications For Sediment Fence Fabric
Temporary Silt Fence Material Property Requirements
Supported' Un-Supported' Type of
Test Material Units Silt Fence Silt Fence Value
Grab Strength ASTM D 4632 N (lbs)
Machine Direction 40D 550 MARV
(90) (90)
X-Machine Direction 400 450 MARV
(90) (90)
Permittivity' ASTM D 4491 sec-1 0.05 0.05 MARV
Apparent Opening Size' ASTM D 4751 mm 0.60 0.60 Max. ARV'
(US Sieve #) (30) (30)
% 70% after 70% after
Ultraviolet Stability ASTM D 4355 Retained 500h of exposure 500h of exposure Typical
Strength
' Sift Fence support shall consist of 14 gage steel wire with a mesh spacing of 150 mm (6 inches), or prefabricated poylmer mesh of
equivalent strength.
2 These default values are based on empirical evidence with a variety of sediment. For environmentally sensitive areas, a review of
previous experience and/or site or regionally specific geotextile tests in accordance with Test Method D 5141 should be performed
by the agency to confirm suitability of these requirements.
3 As measured in accordance with Test Method D 4632.
Rev. 6/06
CONSTRUCTION
1. Construct the sediment barrier of standard strength or extra strength
synthetic filter fabrics.
2. Ensure that the height of the sediment fence does not exceed 24 inches
above the ground surface. (Higher fences may impound volumes of water
sufficient to cause failure of the structure.)
3. Construct the filter fabric from a continuous roll cut to the length of the
barrier to avoid joints. When joints are necessary, securely fasten the filter
cloth only at a support post with 4 feet minimum overlap to the next post.
4. Support standard strength filter fabric by wire mesh fastened securely to
the upslope side of the posts. Extend the wire mesh support to the bottom of
the trench. Fasten the wire reinforcement, then fabric on the upslope side of
the fence post. Wire or plastic zip ties should have minimum 50 pound tensile
strength.
5. When a wire mesh support fence is used, space posts a maximum of 8 feet
apart. Support posts should be driven securely into the ground a minimum of
24 inches.
6. Extra strength filter fabric with 6 feet post spacing does not require wire
mesh support fence. Securely fasten the filter fabric directly to posts. Wire or
plastic zip ties should have minimum 50 pound tensile strength.
6.62.3

7. Excavate a trench approximately 4 inches wide and 8 inches deep along
the proposed line of posts and upslope from the barrier (Figure 6.62a).
8. Place 12 inches of the fabric along the bottom and side of the trench.
9. Backfill the trench with soil placed over the filter fabric and compact.
Thorough compaction of the backfill is critical to silt fence performance.
10. Do not attach filter fabric to existing trees.
SEDIMENT FENCE INSTALLATION USING THE SLICING METHOD
Instead of excavating a trench, placing fabric and then backfilling trench,
sediment fence may be installed using specially designed equipment that
inserts the fabric into a cut sliced in the ground with a disc (Figure 6.62b).
Installation '-The base of both end posts should be at least one foot higher than the
Specifications middle of the fence. Check with a level if necessary.
2. Install posts 4 feet apart in critical areas and 6 feet apart on standard
applications.
3. Install posts 2 feet deep on the downstream side of the silt fence, and
as close as possible to the fabric, enabling posts to support the fabric from
upstream water pressure.
4. Install posts with the nipples facing away from the silt fabric.
5. Attach the fabric to each post with three ties, all spaced within the top 8
inches of the fabric. Attach each tie diagonally 45 degrees through the fabric,
with each puncture at least 1 inch vertically apart. Also, each tie should be
positioned to hang on a post nipple when tightened to prevent sagging.
6. Wrap approximately 6 inches of fabric around the end posts and secure
with 3 ties.
7. No more than 24 inches of a 36 inch fabric is allowed above ground
level.
8. The installation should be checked and corrected for any deviations before
compaction.
9. Compaction is vitally important for effective results. Compact the soil
immediately next to the silt fence fabric with the front wheel of the tractor,
skid steer, or roller exerting at least 60 pounds per square inch. Compact the
upstream side first, and then each side twice for a total of 4 trips.
6.62.4
Rev. 6/06

Practice Standards and Speciicatiorzs
Wire
Figure 6.62a Installation detail of a sediment fence.
Rev. 6/06
Steel
post
Wire
fence
24"
b' max. standard strength tabric with wire tence
6' max. extra strength fabric without wire fence

24

5" down & 4"
forward along
the trench
Plastic or
ire ties
Natural
ground
Y
\ Filter
fabric
Cross-Section
View
Filter
fabric Backfil) trench Natural
and compact ground
thoroughly
•• • • •• • • • •• •
'4• • ' Upskope
• •. min • .•
•.: • ' • •• ' min
6.62.5
E
The Slicing Method
Ponding height POST SPACING:
mcnc . 24' 6' max . on open runs
4' max . on pooling areas
Attach fatxic to Y
upstream side of post
FLOW -? it
Drive over each side of silt
fence 2 to 4 times with POST DEPTH:
2 feet
device exerting 60 p.s.i. or
greater
compacted soil compacted soil

//
\\\ \\\ \\ 16
°a
\\\/\\/\\ \\ ?\
C

No more than 24" ofa 36" fabric
is allowed above ground.
Top of Fabric -}
Belt
tole 8'
i
ATTACHMENT DETAILS:
• Gather fabric at posts, If needed.
• Utilize three ties per post, all within top 8' of fabric.
• Position each fie diagonally, puncturing holes vertically
a minimum of 1' apart.
• Hang each tie ona post nipple and tighten securely.
Use cable ties (50lbs) or soft wire.
Roll of sift fence
Post
installed
after
compaction
Silt Fence
t
12"
1

Horizontal chisel point Slicing blade
( 3" width ) ( 0.7^ width) Completed Installation
Vibratory plow is not acceptable because of horizontal compaction
Figure 6.62b Schematics for using the slicing method to install a sediment fence. Adapted from Silt Fence that Works
6.62.6 Rev. 6106
I
Practice Standards and Specifications

Maintenance Inspect sediment fences at least once a week and after each rainfall. Make any
required repairs immediately.
Should the fabric of a sediment fence collapse, tear, decompose or become
ineffective, replace it promptly.
Remove sediment deposits as necessary to provide adequate storage volume
for the next rain and to reduce pressure on the fence. Take care to avoid
undermining the fence during cleanout.
' Remove all fencing materials and unstable sediment deposits and bring the
area to grade and stabilize it after the contributing drainage area has been
properly stabilized.
References ASTMD 6461-99. "Standard Specification for Silt Fence Materials" ASTM
International. For referenced ASTM standards, visit the ASTM website,
www.astm.org, or contactASTM Customer Service at [e-mail]. For
Annual Book ofASTM Standards volume information, refer to the standard's
Document Summary page on the ASTM website.
ASTM D 6462 - 03. "Standard Practice for Silt Fence Installation" ASTM
International. For referenced ASTM standards, visit the ASTM website,
www.astm.org, or contactASTM Customer Service at [e-mail]. For
Annual Book ofASTM Standards volume information, refer to the standard's
Document Summary page on the ASTM website.
C. Joel Sprague, PE, Silt Fence Performance Limits and Installation
Requirements. Sprague and Sprague Consulting Engineers and TRY
Environmental, Inc.
Carpenter Erosion Control. http://wwvv.tommy-sfm.com/
Kentucky Erosion Prevention and Sediment Control Field Manual, 2004.
Runoff Control Measures
' 6.20, Temporary Diversions
Outlet Protection
6.41, Outlet Stabilization Structure
Appendix

I 8.03, Estimating Runoff
I Rev. 6/06 6.62.7
!s1
6.62.8 Rev. 6/06

n
0
u

u

1

Rev. 6/06
Practice Standards arid Spec ficatiarts
Definition A small temporary stone dam constructed across a drainage way.
Purpose To reduce erosion in a drainage channel by reducing the velocity of flow.
Conditions Where This practice maybe used as atemporary measure to limit erosion by reducing
Practice Applies velocity in small open channels. When needed, they can be used in channels,
roadside ditches, and temporary diversions.
Check darns may be used to:
• reduce velocity in small temporary channels that are degrading, but
where permanent stabilization is impractical due to their short period of
usefulness;
• reduce velocity in small eroding channels where construction delays or
weather conditions prevent timely installation of nonerosive liners.
Do not use check dams in intermittent or perennial streams.
Planning Check dams are an expedient waytoreduce gullyinginthebottom ofchannels
that will be filled or stabilized at a later date. The dams should only be used
Considerations while permanent stabilization measures are being put into place.
Check darns installed in grass-lined channels may kill the vegetative lining
if submergence after it rains is too long and/or silting is excessive. All stone
and riprap must be removed if mowing is planned as part of vegetative
maintenance.
Design Criteria The following criteria should be used when designing a check dam:
• The drainage area is limited to one half acre.
• Keep a maximum height of 2 feet at the center of the dam.
• Keep the center of the check dam at least 9 inches lower than the outer
edges at natural ground elevation.
• Keep the side slopes of the dam at 2:1 or flatter.
• Ensure that the maximum spacing between dams places the toe of the
upstream dam at the same elevation as the top of the downstream dam
(Figure 6.83a).
• Stabilize outflow areas along the channel to resist erosion.
• Use NC DOT Class B stone and line the upstream side of the dam with
NC DOT #5 or #57 stone.
• Key the stone into the ditch banks and extend it beyond the abutments a
minimum of 1.5 feet to avoid washouts from overflow around the dam.
6.83.1
1
LI
Construction L Place stone to the lines and dimensions shown in the plan on a filter fabric
Specifications foundation.
2. Keep the center stone section at least 9 inches below natural ground level
where the dam abuts the channel banks.
3. Extend stone at least 1.5 feet beyond the ditch bank (Figure 6.83b) to keep
water from cutting around the ends of the check dam.
4. Set spacing between dams to assure that the elevation at the top of the
lower dam is the same as the toe elevation of the upper dam.
5. Protect the channel after the lowest check dam from heavy flow that could
cause erosion.
6. Make sure that the channel reach above the most upstream dam is stable.
7. Ensure that other areas of the channel, such as culvert entrances below the
check dams, are not subject to damage or blockage from displaced stones. .
Figure 6.83a Space check dams in a channel so that the crest of downstream dam is at elevation of the toe of upstream dam.
6.83.2 Rev. 6106
L = The distance such that points
A and B are of equal elevation

Practice Stastdards and Specifications

f

L

0
[1
1

9" min
Plan View
1'V1 _F ni!'nn-r 4*rZ __ 44-=-7
Fi Ite
Cross-Section View
rilter Cloth
1.5' min.
Figure 6.83b Stone check dam stone should be placed over the channel banks to keep water from cutting around the
dam.
Maintenance Inspect check dams and channels at least weekly and after each significant (1/2
inch or greater) rainfall event and repair immediately. Clean out sediment,
straw, limbs, or other debris that could clog the channel when needed.
Anticipate submergence and deposition above the check dam and erosion from
high flows around the edges of the dam. Correct all damage immediately. If
significant erosion occurs between dams, additional measures can be taken
such as, installing a protective riprap liner in that portion of the channel
(Practice 6.3 1, Riprap-line and Paved Channels).
Remove sediment accumulated behind the dams as needed to prevent damage
to channel vegetation, allow the channel to drain through the stone check dam,
and prevent large flows from carrying sediment over the dam. Add stones to
dams as needed to maintain design height and cross section.
References RunofJConveyazce >'feasures
6.30, Grass-lined Channels
6.3 1, Riprap-lined and Paved Channels
North Carolina Department of Transportation
Standard Specifications for Roads and Structures
Rev. 6/06
6.83.3
w
6.83.4 Rev. 6/06 1

0

1
L
Rev. 6/06
Practice Standards and Specifications
Purpose To prevent sediment from entering, accumulating in and being transferred
by a culvert or storm drainage system prior to stabilization of the disturbed
drainage area. This practice allows early use of the storm drainage system.
Conditions Where Rock pipe inlet protection may be used at pipes with a maximum diameter
Practice Applies of 36 inches. This inlet protection may be used to supplement additional
sediment traps or basins at the pipe outlet, or used in combination with an
excavated sediment storage area to serve as a temporary sediment trap. Pipe
inlet protection should be provided to protect the storm drainage system and
downstream areas from sedimentation until permanent stabilization of the
disturbed drainage area.
Do not install this measure in an intermittent or perennial stream.
Planning When construction on a project reaches a stage where culverts and other storm
Considerations drainage structures are installed and many areas are brought to the desired
grade, there is a need to protect the points where runoff can leave the site
through culverts or storm drains. Similar to drop and curb inlets, culverts
receiving runoff from disturbed areas can convey large amounts of sediment
to lakes or streams. Even if the pipe discharges into a sediment trap or basin,
the pipe or pipe system itself may clog with sediment.
Design Criteria When used in combination with an excavated sediment storage area to serve
as a temporary sediment trap, the design criteria for temporary sediment traps
must be satisfied. The maximum drainage area should be 5 acres, and 3600
cubic feet of sediment storage per acre of disturbed drainage area should be
provided.
The minimum stone height should be 2 feet, with side slopes no steeper than
2:1. The stone "horseshoe" around the pipe inlet should be constructed of
Class B or Class I riprap, with a minimum crest width of 3 feet. The outside
face of the riprap should be coved with a 12-inch thick layer of #5 or 957
washed stone.
In preparing plans for rock pipe inlet protection, it is important to protect the
embankment over the pipe from overtopping. The top of the stone should be a
minimum of 1 foot below the top of the fill over the pipe. The stone should tie
into the fill on both sides of the pipe. The inside toe of the stone should be no
closer than 2 feet from the culvert opening to allow passage of high flows.
The sediment storage area should be excavated upstream of the rock pipe inlet
protection, with a minimum depth of 18 inches below grade.
6.55.1
IFA -19
tov, Definition A horseshoe shaped rock dam structure at a pipe inlet with a sediment storage
area around the outside perimeter of the structure.
Q
Natural Ground
6.55.2
Rev. 6/06
Figure 6.55a Rock pipe inlet protection plan view and cross-section view
' Practice Standards acrd Specifications
Construction 1. Clear the area of all debris that might hinder excavation and disposal of
Specifications spoil.
2. Install the Class B or Class I riprap in a semi-circle around the pipe
inlet. The stone should be built up higher on each end where it ties into the
embankment. The minimum crest width of the riprap should be 3 feet, with a
minimum bottom width of 11 feet. The minimum height should be 2 feet, but
also I foot lower than the shoulder of the embankment or diversions.
3. A 1 foot thick layer of NC DOT 45 or #57 stone should be placed on the
outside slope of the riprap.
4. The sediment storage area should be excavated around the outside of the
stone horseshoe 18 inches below natural grade.
5. When the contributing drainage area has been stabilized, fill depression
and establish final grading elevations, compact area properly, and stabilize
with ground cover.
Maintenance Inspect rock pipe inlet protection at least weekly and after each significant (%
' inch or greater) rainfall event and repair immediately. Remove sediment and
restore the sediment storage area to its original dimensions when the sediment
has accumulated to one-half the design depth of the trap. Place the sediment
that is removed in the designated disposal area and replace the contaminated
part of the gravel facing.
Check the structure for damage. Any riprap displaced from the stone horseshoe
must be replaced immediately.
a After all the sediment-producing areas have been permanently stabilized,
remove the structure and all the unstable sediment. Smooth the area to
' blend with the adjoining areas and provide permanent ground cover (Surface
Stabilization).
I References Inletprotection
6.52, Block and Gravel Inlet Protection (Temporary)
Sediment Trap and Barriers
6.60, Temporary Sediment Trap
Surface Stabilisation
6.15, Riprap
North Carolina Department of Transportation
Erosion & Sedimentation Guidelines for Division Maintenance Operation,
1993.
Nrginia Erosion and Sediment Control Handbook 1992. STD & SPEC
3.08, Culvert Inlet Protection. pages 1I1-46 -111-51 (Culvert Inlets Sediment
Trap).
I Rev. 6106
6.55.3
6.55.4
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Practice Standards and Specifications
Purpose To protect the soil surface from erosive forces and/or improve stability of soil
slopes that are subject to seepage or have poor soil structure.
Conditions Where Riprap is used for the following applications:
Practice Applies • cut-and-fill slopes subject to seepage or weathering, particularly where
conditions prohibit establishment of vegetation,
• channel side slopes and bottoms,
• inlets and outlets for culverts, bridges, slope drains, grade stabilization
structures, and storm drains
• streambank and stream grades,
• shorelines subject to wave action.
Planning Riprap is a versatile, highly erosion-resistant material that can be used
Considerations effectively in many locations and in a variety of ways to control erosion on
construction sites.
GRADED VERSUS UNIFORM RIPRAP
Riprap is classed as either graded or uniform. Graded riprap includes a wide
mixture of stone sizes. Uniform riprap consists of stones nearly all the same
size.
Graded riprap is preferred to uniform riprap in most applications because it
forms a dense, flexible cover. Uniform riprap is more open, and cannot adjust
as effectively to movement of the stones. Graded riprap is also cheaper to
install requiring less hand work for installation than uniform riprap, which
must be placed in a uniform pattern. Uniform riprap may give a more pleasing
appearance.
Riprap sizes are designated by either the mean diameter or the weight of
the stones. The diameter specification is often misleading since the stones
are usually angular. However, common practice is to specify stone size by
the diameter of an equivalent size of spherical stone. Table 6.15a lists some
typical stones by weight, spherical diameter, and the corresponding rectangular
dimensions. These stone sizes are based upon an assumed specific weight of
165 lb/ft'.
A method commonly used for specifying the range of stone sizes in graded
riprap is to designate a diameter for which some percentage, by weight, will be
smaller. For example, "d85" specifies a mixture of stones in which 85% of the
stone by weight would be smaller than the diameter specified. Most designs
are based on "d5Gor median size stones.
Riprap and gravel are often designated by N.C. Department of Transportation
specifications (Table 6.15b).
6.15.1
RR
Definition A layer of stone designed to protect and stabilize areas subject to erosion.
76?15-
Table 6.15a
Size or Riprap Stones
Mean Spherical Length Rectangular Shape
Weight (lb) Diameter (ft) (ft) Width/Height (ft)
50 0.8 1.4 0.5
100 1.1 1.8 0.6
150 1.3 2.0 0.7
300 1.6 2.6 0.9
500 1.9 3.0 1.0
1000 2.2 3.7 1.3
1500 2.6 4.7 1.5
2000 2.8 5.4 1.8
4000 3.6 6.0 2.0
6000 4.0 6.9 2.3
8000 4.5 7.6 2.5
20000 6.1 10.0 3.3
source: Va SWCC
When considering riprap for surface stabilization, it is important to anticipate
visual impacts, including weed control, hazards from snakes and other animals,
danger of slides and hazards to areas below steep riprap slopes, damage and
possible slides from children moving stones, and general safety.
Proper slope selection and surface preparation are essential for successful
long-term functioning of riprap. Adequate compaction of fill areas and proper
use of filter blankets are necessary.
Sequence of construction-Schedule disturbance of areas that require
riprap protection so that the placement of riprap can follow immediately after
grading. When riprap is used for outlet protection, place the riprap before or
in conjunction with the installation of the structure so that it is in place before
the first runoff event.
Design Criteria Gradation-Riprap should be a well-graded mixture with 50% by weight
larger than the specified design size. The diameter of the largest stone size
in such a mixture should be 1.5 times the dsu size with smaller sizes grading
down to 1 inch.
The designer should determine the ripmp size that will be stable for design
conditions. Having determined the design stone size, the designer should
select the size or sizes that equal or exceed that minimum size based on riprap
gradations commercially available in the area.
Thickness---Construction techniques, dimensions of the area to be protected,
size and gradation of the ripmp, the frequency and duration of flow, difficulty
and cost of maintenance, and consequences of failure should be considered
when determining the thickness of riprap linings. The minimum thickness
should be 1.5 times the maximum stone diameter, but in no case less than 6
inches.
Quality of stone Stone for riprap may consist of field stone or quarry stone.
The stone should be hard, angular, of such quality that it will not break down
6.15.2
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Practice Standards and Specifications
Table 6.15b
Sizes for Riprap and Erosion
Control Stone Specified by
the N.C. Department of
Transportation
Riprap Erosion Control
Class Class Class Class
1 2 A B
5 to 200 lb 25 to 250 lb 2" to 6" 5" to 15"
30% shall 60% shall
weigh a weigh a
minimum of 60 minimum of 100
Ibs each lb each
No more than No more than 10% tolerance
10% shall 5% shall weigh top and bottom
weigh less than less than 50 lb sizes
15 lb each each
Equally Equally
distributed, distributed,
no gradation no gradation
specified specified
source: North Carolina Aggregates Association
on exposure to water or weathering, and suitable in all other respects for the
purpose intended. The specific gravity of the individual stones should be at
least 2.5.
Size of stone-The sizes of stones used for riprap protection are determined
by purpose and specific site conditions.
• Slope stabilization-Riprap stone for slope stabilization, not subject to
flowing water or wave action, should be sized for stability for the proposed
grade. The gradient of the slope to be stabilized should be less than the
natural angle of repose of the stone selected. Angle of repose of riprap
stones may be estimated from Figure 6.15a.
Riprap used for surface stabilization of slopes does not add significant
resistance to sliding or slope failure, and should not be considered a
retaining wall. The inherent stability of the soil must be satisfactory
before riprap is used for surface stabilization. Slopes approaching 1.5:1
may require special stability analysis.
• Outlet protection-Design criteria for sizing stone, and determining the
dimensions of riprap pads at channel or conduit outlets are presented in
Practice 6.4 1, Outlet Stabilisation Structure.
• Channel stabilization and streambank protection-Design criteria for
sizing stone for stability of channels are contained in.4ppendix 8.05.
Filter blanket-A filter blanket is a layer of material placed between the riprap
and the underlying soil to prevent soil movement into or through the riprap.
6.153
s
41
39
Q
U)
0 37
cc
0 35
a)
a?
Q 33
Mean Stone Size d50, ft
Figure 6.15a Angie of repose for different rock shapes and sizes.
Adapted from: FHWA, HEC-15, pg. 49 - April 1988
A suitable filter may consist of a well-graded gravel or sand-gravel layer or a
synthetic filter fabric manufactured for this express purpose. The design of a
gravel filter blanket is based on the ratio of particle size in the overlying filter
material to that of the base material in accordance with the criteria below. The
designed gravel filter blanket may consist of several layers of increasingly
large particles from sand to erosion control stone.
A gravel filter blanket should have the following relationship for a stable
design:
d15 filter
85 base 5
d15 filter
5 1e < 40
d50 filter
so base <_ 40
In these relationships, filter refers to the overlying material, and base refers
to the underlying material. These relationships must hold between the filter
material and the base material (soil foundation), and between the riprap and
the filter. More than one layer of filter material may be needed. Each layer of
filter material should be at least 6 inches thick.
6.15.4 Rev. 12/93
Practice Standards and Specifications
A synthetic filter fabric may be used with or in place of gravel filters. The
following particle size relationships should exist:
• Filter fabric covering a base with granular particles containing 50% or
less (by weight) of fine particles (less than U.S. Standard Sieve no. 200
[0.074mm]):
a. d85 base (mm)
EOS* filter fabric
(mm)
b. total open area of filter should not exceed 36%.
• Filter fabric covering other soils:
a. EOS is no larger than U.S. Standard Sieve no. 70 (0.21mm),
b. total open area of filter should not exceed 10%.
*EOS - Equivalent opening size compared to a U. E. standard sieve size.
No filter fabric should have less than 4% open area, or an EOS less than U.S.
Standard Sieve No. 100 (0.15mm). The permeability of the fabric must be
greater than that of the soil. The fabric may be made of woven or nonwoven
monofilament yarns, and should meet the following minimum requirements:
• thickness 20 - 60 mils,
• grab strength 90 - 120 lb, and
• conform to ASTM D-1682 or ASTM D-177.
Filter blankets should always be provided where seepage is significant,
or where flow velocity and duration of flow or turbulence may cause the
underlying soil particles to move through the riprap.
Construction Subgrade preparation-Prepare the subgrade for riprap and filter to the
SpecificationS required lines and grades shown on the plans. Compact any fill required in
the subgrade to a density approximating that of the surrounding undisturbed
material or overfill depressions with riprap. Remove brush, trees, stumps,
and other objectionable material. Cut the subgrade sufficiently deep that the
finished grade of the riprap will be at the elevation of the surrounding area.
Channels should be excavated sufficiently to allow placement of the riprap in
a manner such that the finished inside dimensions and grade of the riprap meet
design specifications.
Sand and gravel filter blanket-Place the filter blanket immediately after
the ground foundation is prepared. For gravel, spread filter stone in a uniform
layer to the specified depth. Where more than one layer of filter material is
used, spread the layers with minimal mixing.
Synthetic filter fabric-Place the cloth filter directly on the prepared
foundation. Overlap the edges by at least 12 inches, and space anchor pins
every 3 ft along the overlap. Bury the upstream end of the cloth a minimum of
12 inches below ground and where necessary, bury the lower end of the cloth
or over lap with the next section as required. See Figure 6.14a Page 6.14.6.
Rev. 12/93 6.15.5
0
Take care not to damage the cloth when placing riprap. If damage occurs
remove the riprap, and repair the sheet by adding another layer of filter material
with a minimum overlap of 12 inches around the damaged area. If extensive
damage is suspected, remove and replace the entire sheet.
Where large stones are used or machine placement is difficult, a 4-inch layer
of fine gravel or sand may be needed to protect the filter cloth.
Stone placement-Placement of riprap should follow immediately after
placement of the filter. Place riprap so that it forms a dense, well-graded
mass of stone with a minimum of voids. The desired distribution of stones
throughout the mass may be obtained by selective loading at the quarry, and
controlled dumping during final placement. Place riprap to its full thickness
in one operation. Do not place riprap by dumping through chutes or other
methods that cause segregation of stone sizes. Take care not to dislodge the
underlying base or filter when placing the stones.
The toe of the riprap slope should be keyed to a stable foundation at its base
as shown in Figure 6.15b. The toe should be excavated to a depth about 1.5
times the design thickness of the riprap, and should extend horizontally from
the slope.
The finished slope should be free of pockets of small stone or clusters of large
stones. Hand placing may be necessary to achieve the proper distribution
of stone sizes to produce a relatively smooth, uniform surface. The finished
grade of the riprap should blend with the surrounding area. No overfall or
protrusion of riprap should be apparent.
Figure 6.15b Riprap slope protection
(modified from VDH&T).
6"
filt
T
in '
Maintenance In general, once a riprap installation has been properly designed and installed
it requires very little maintenance. Riprap should be inspected periodically for
scour or dislodged stones. Control of weed and brush growth may be needed
in some locations. '
References Runoff Conveyance Measures '
6.3 1, Riprap-lined and Paved Channels
6.15.6 Rev.12/93

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Practice Standards and Specifications
Outlet Protection
6.41, Outlet Stabilization Structure
Appendices
8.05, Design of Stable Channels and Diversions
8.06, Design of Riprap Outlet Protection
I Rev. 12/93
6.15.7

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Practice Standards and Specifications
Purpose To provide a means for construction vehicles to cross streams or watercourses
without moving sediment into streams, damaging the streambed or channel,
or causing flooding.
Conditions Where Where heavy equipment must be moved from one side of a stream channel
to another, or where light-duty construction vehicles must cross the stream
Practice Applies channel frequently for a short period of time.
Planning Careful planning can minimize the need for stream crossings. Try to avoid
crossing streams. Whenever possible, complete the development separately
Considerations on each side and leave a natural buffer zone along the stream. Temporary
stream crossings can be a direct source of water pollution; they may create
flooding and safety hazards; they can be expensive to construct; and they can
cause costly construction delays if washed out.
Both fords and culverts may involve placing fill in an intermittent or periennial
stream or wetland. The need for permits from the U.S. Army Corps of
Engineers or the N. C. Division of Water Quality should be determined when
planning the project.
Select locations for stream crossings where erosion potential is low. Evaluate
stream channel conditions, overflow areas, and surface runoff control at the
site before choosing the type of crossing. When practical, locate and design
temporary stream crossings to serve as permanent crossings to keep stream
disturbance to a minimum.
Plan stream crossings in advance of need and, when possible, construct them
during dry periods to minimize stream disturbance and reduce cost. Ensure
that all necessary materials and equipment are on-site before any work is
begun. Complete construction in an expedient manner, and stabilize the area
immediately.
Often stream crossings are provided in conjunction with operations in a
natural watercourse. Land disturbing activity in connection with construction
in, on, over, or under a lake or natural watercourse shall minimize the extent
and duration of disruption of the stream channel. Where relocation of a
stream forms an essential part of the proposed activity, the relocation shall
minimize unnecessary changes in the stream flow characteristics. Pumping
or diverting stream flow around a work area is often the best way to minimize
the disruption of the stream channel. Any diversions should be stabilized with
adequate geotextile fabric or stone.
After the bypass is completed and stable, the stream may be diverted (Practice
6.15, Riprap). Small stream flows may be diverted around work areas with a
coffer dam and pump instead of construction of a bypass channel.
6.70.1
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Definition Abridge, ford or temporary structure installed across a stream or watercourse
for short-term use by construction vehicles or heavy equipment.
6
Unlike permanent stream crossings. temporary stream crossings may be al-
lowed to overtop during peak storm periods. However, the structure and ap-
proaches should remain stable. Keep any fill needed in flood plains to a mini-
mum to prevent upstream flooding and reduce erosion potential. Use riprap to
protect locations subject to erosion from overflow.
If permanent utility crossings are planned, stream crossings may be located at
these locations to minimize stream impacts.
Stream crossings are of the three general types: bridges, culverts, and fords
Consider which method best suits the specific site conditions.
Bridges-Where available materials and designs are adequate to bear the ex-
pected loadings, bridges are preferred for temporary stream crossing.
Bridges usually cause the least disturbance to the stream bed, banks, and sur-
rounding area. They provide the least obstruction to flow and fish migra-
tion. They generally require little maintenance, can be designed to fit most
site conditions, and can be easily removed and materials salvaged. However,
bridges are generally the most expensive to design and construct. Further,
they may offer the greatest safety hazard if not adequately designed, installed,
and maintained, and if washed out, they cause a longer construction delay and
are more costly to repair.
In steep watersheds it is recommended to tie a cable or chain to one corner of
the bridge frame with the other end secured to a large tree or other substantial
object. This will prevent flood flows from carrying the bridge downstream
where it may cause damage to other property.
Culvert crossings- Culverts are the most common stream crossings. In many
cases, they are the least costly to install, can safely support heavy loads, and
are adaptable to most site conditions. Construction materials are readily avail-
able and can be salvaged. However, the installation and removal of culverts
causes considerable disturbance to the stream and surrounding area. Culverts
also offer the greatest obstruction to flood flows and are subject, therefore,
to blockage and washout. Clean stone should be used for back fill around
culverts
Culverts should be used when vehicles will make repeated trips across the
stream during construction, or track mud into the stream.
Fords-Fords, made of stabilization material such as rock, are often used in
steep areas subject to flash flooding, where normal flow is shallow (less than
3 inches deep) or intermittent. Fords should only be used where crossings are
infrequent. Fords are especially adapted for crossing wide, shallow water-
courses (Figure 6.70a).
6.70.2 Rev. 6/06
Practice Standards and Specifications
When properly installed, fords offer little or no obstruction to flow, can safely
handle heavy loadings, are relatively easy to install and maintain, and in most
cases, may be left in place at the end of the construction.
Problems associated with fords include the following:
1. Approach sections are subject to erosion. Generally, do not use fords
where the bank height exceeds 5 feet.
2. Excavation for the installation of the riprap-gravel bottom and filter
material causes major stream disturbance. In some cases, fords may be
adequately constructed by shallow filling without excavation.
3. The stabilizing material is subject to washing out during storm flows and
may require replacement.
4. Mud and other contaminants are brought directly into the stream on
vehicles unless crossings are limited to no flow conditions.
Stream Channel
5' max bark
height I ,... Surface Flow
Diversions
i
Stone approach section
5:1 max, slope on road
over
otextile
fabric
Snrfnro Fl-,
Figure 6.70a A well constructed ford offers little obstruction to flow while safely handling heavy loading.
Rev. 6/06 6.70.3
Clean Stone Ge-ote.xtile
Fabric
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