6204-UwharrieMSWLF_PTCApp_Cell14B_UnderdrainPipingPlan_DIN27508_20170309

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Underdrain Pipe Design

The proposed 4” diameter underdrain pipe was evaluated to confirm that the pipe
has the capacity to handle the estimated flow from the seeps that were discovered during
preliminary grading activities. Based on field observation of the seeps, the estimated flow
is less than 5 gallons per minute (gpm).

Utilizing the Hydraflow Express computer program for 4” diameter pipe at the
minimum slope of 0.95% (see attached report), the capacity of this pipe is:

Q = .210 cfs = 94.3 gpm

The capacity of the 4” diameter pipe is 94.3 gpm, and the estimated worst case flow is 5
gpm, for a Factor of Safety of 18.9.

In summary, the 4” diameter underdrain pipe is adequate for the anticipated flow.

Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Mar 9 2017
4'' UNDERDRAIN
CircularDiameter (ft) = 0.33
Invert Elev (ft) = 681.00Slope (%) = 0.95
N-Value = 0.012
CalculationsCompute by: Known Depth
Known Depth (ft) = 0.32
HighlightedDepth (ft) = 0.32
Q (cfs) = 0.210
Area (sqft) = 0.08Velocity (ft/s) = 2.49Wetted Perim (ft) = 0.90
Crit Depth, Yc (ft) = 0.26
Top Width (ft) = 0.14
EGL (ft) = 0.41
0 1
Elev (ft)Section
680.75
681.00
681.25
681.50
681.75
682.00
Reach (ft)
C:\Users\cmoeller\Documents\Uwharrie\
4 inch Pipe SDR 9 of 03 06 17 Underdrain Design.xlsx Page 3 of 4
Project:
Date:
Job#:
Structural Design of Underdrain System Pipes
OBJECTIVE:
METHOD:
1. Determine the maximum vertical pressure acting on the underdrain pipe.
2. Evaluate the pipe for:
a. Wall Crushing b. Wall Buckling c. Ring Deflection
PARAMETERS/INPUT: Max Height of Waste over Pipe 160 ft Unit weight of soil 125 pcf
Thickness of Final Cover 4.0 ft Unit wt. of waste (avg)85 pcf (conservative)
Thickness of fill layer over pipe 25.6 ft
Height of Gravel over pipe 0.3 ft Soil modulus (E' in psi) (Ref. 1)
Nom. Pipe Diameter 4.0 in Subgrade modulus (Ref. 1)
Perforation Diameter 0.375 in Ldl (Deflection Factor) =1 (Conservative)
# Perforations per foot 4 Kbed (Bedding Factor) =0.1 (Conservative)
1,000 psi Fs (soil support factor) =0.5 (Conservative)
Allow. Ring Deflection 7.5%
Outside Pipe Diameter 4.50 in
SDR 9
Min. Wall thickness 0.50 in
Internal Pipe Diameter =3.50 in
DM (Average Diameter of Pipe) =4.00 in
CALCULATIONS:
Computation of the vertical stress acting on pipe -
PE = Soil unit weight x (Hcover + Hseparation layer + Hgravel) + Unit weight of waste x Hwaste
PE =or 120.4 psi
Papplied =0.75 PE =90.3 psi
Design for Wall Crushing -
SDR x Papplied =
2
FS crush = 2.5
Design for Wall Buckling -Where B' = Soil Support Factor,
R = Bouaynce Reduction Factor
=1.00 =1.00 HGW = GW height
H = Total cover height
=786.23 / FS psi: for Factor of Safety (N in equation) = 1
or 113,217 psf
FS buckling =PwcPapplied
Determine the structural durability of the 4-inch underdrain pipes under the maximum design height of waste.
SA =406.4 psi
Sa/Comp. Strenght =
=8.7
Elastic Mod. of HDPE (E) =
(long term term, reduced for
high temperature)
23,809 psi
Elastic Mod. of HDPE (E) =
(short term)106,730 psi
17340 psf
(Assumes that arching occurs over the pipe as it deflects, thus the
load on the pipe is ditributed over a larger area and the unit
pressure is reduced - Ref. 2)
Uwharries Regional3/6/2017
6703-716
5,000 psi
10,000 psi
Compressive Strength of pipe (Ref. 1
- Table C-1 Chapt 3)
C:\Users\cmoeller\Documents\Uwharrie\
4 inch Pipe SDR 9 of 03 06 17 Underdrain Design.xlsx Page 4 of 4
Project:
Date:
Job#:
Structural Design of Underdrain System Pipes
Uwharries Regional3/6/2017
6703-716
Design for Ring Deflection -
Ring Deflection, ∆x =4.13%which is < t 7.50%, therefore
above designed pipe is :
SUMMARY AND CONCLUSION:
The Factors of Safety calculated for the underdrain pipe design are as follows:
Wall Crushing =2.5
Wall Buckling =8.7
The calculated max deflection is less than the maximum allowable deflection for plastic pipes (Ref.1).
REFERENCES:
Made by:CMM
Checked by:
Reviewed by:
=
SATISFACTORY
Ref. 1 - 2nd Edition, Handbook of Polyethylene (PE) Pipe, The Plastics Pipe Institute, Chapt. 3 and Chapt. 6
www.plasticpipe.org
Ref. 2 - Assessment and Recommendations for Improving the Performance of Waste Containment Systems, EPA/600/R-
02/099, 2002, Page 2-24.
Specifications and Contract Documents – Cell No. 14B
Uwharrie Regional MSW Landfill Montgomery, NC
March 2017 HHNT Project No. 6703-716-01

02722-1

SECTION 02722 UNDERDRAIN SYSTEM
PART 1 GENERAL
1.1 DESCRIPTION OF WORK
The CONTRACTOR shall furnish all labor, material, supervision, and equipment to complete the
underdrain system including HDPE piping, gravel and geotextile.
1.2 RELATED WORK
Section 01400-Quality Control
Section 02210-Grading
Section 02220-Trenching, Backfilling and Compaction
1.3 SUBMITTALS
Tests and certifications shall be provided to the ENGINEER for the items listed under products.
1. Article 2.1 Gravel
2. Article 2.2 Geotextile Fabric
3. Pipe as identified under Article 2.3 Pipe Schedule and Article 2.4 High Density
Polyethylene (HDPE) Pipe
1.4 QUALITY CONTROL
Quality control shall be in accordance with the requirements of Section 01400 Quality Control
and the testing program requirements of this section.
PART 2 PRODUCTS
2.1 GRAVEL
Gravel for encasing the underdrain pipe shall be a clean washed hard non-carbonaceous mineral
such as quartz. Gravel size shall be ASTM No. 57 or No. 4.
2.2 GEOTEXTILE FABRIC
A. Geotextile shall be a non-woven geotextile of polypropylene filtration fibers or polyester
yarns which are intended to be and shall be suitable for separation and drainage.
Geotextile shall be 6.0 ounce per square yard fabric as called for on the Drawings.

Specifications and Contract Documents – Cell No. 14B
Uwharrie Regional MSW Landfill Montgomery, NC
March 2017 HHNT Project No. 6703-716-01

02722-2

2.3 PIPE SCHEDULE
Pipe Type

SDR

Diameter

Type

Minimum
Pipe Length
Perforated 9 4 inch HDPE Smooth Wall 40 Feet

2.4 HIGH DENSITY POLYETHYLENE (HDPE) PIPE
A. Pipe and Fittings Resin
The pipe supplied under this specification shall be high performance, very high
molecular weight, and high density polyethylene pipe. All pipe and fitting resins shall be
manufactured by the same company which manufactures the pipe in accordance with
these specifications. Complete resin compatibility is expected on the product and total
product accountability is required of the manufacturer. The fittings supplied under this
specification shall be molded or manufactured from a polyethylene compound having a
cell classification equal to or exceeding the compound used in the pipe.
B. Resin physical properties shall comply with the Plastic Pipe Institute (PPI) recommended
material Designation PE 3608/PE 4710 and conform to Material Cell Classification (ASTM
D3350) or 345464C/445474C.
C. Standards
Polyethylene pipe and fittings shall meet all the requirements of NSF listed pipe but are
not required to be NSF listed.
D. The manufacturer shall provide to the CONTRACTOR certified laboratory to verify the
physical properties of the materials supplied under this specification. The manufacturer
shall provide to the CONTRACTOR and the CQA ENGINEER certification that the pipe
produced is represented by the quality assurance data. The OWNER at his own expense
may take random samples for testing by an independent laboratory.
E. Rejection
Polyethylene pipe and fittings which do not meet the requirements of this specification
shall be rejected.
Perforations shall be as detailed, factory machined and trimmed by the manufacturer or
by the pipe supplier in a shop under controlled conditions. No pipe perforating will be
allowed in the field. All perforated pipe shall be free of trimmings and debris when
delivered to the job site.

Specifications and Contract Documents – Cell No. 14B
Uwharrie Regional MSW Landfill Montgomery, NC
March 2017 HHNT Project No. 6703-716-01

02722-3

PART 3 EXECUTION
3.1 GENERAL
The underdrain collection system shall be installed in accordance with the construction details
shown in the Drawings. The pipe shall be embedded in gravel with the geotextile providing
separation of the gravel from the in situ soils.
3.2 HANDLING OF PIPE
Pipe shall be stored on clean, level ground to prevent undue scratching and gouging of the pipe.
Polyethylene pipe shall be protected from extreme heat and direct sunlight. If the pipe must be
stacked for storage, stacking shall be completed in accordance with the pipe manufacturer's
recommendations. Polyethylene pipe shall be moved in a manner that does not damage the
pipe. The pipe will not be dragged over sharp objects or cut by chokers or lifting equipment.
3.3 PIPE INSTALLATION
A. All pipes shall be installed in accordance with the manufacturer's recommendations and
the requirements of these specifications.
B. Perforations shall be cut into the pipe by the manufacturer as detailed in the Drawings.
No field cuts for perforation will be allowed. Perforated pipe shall be laid in the trench
as detailed in the Drawings. The CQA ENGINEER will observe and document the
perforated pipe backfill prior to acceptance for payment.
C. The pipe interior shall be kept clean before and after laying. Pipe shall be kept clean
before installation by proper storage and handling. After installation, pipe shall be
encapsulated in geotextile fabric and covered with stone. Any open pipe ends shall be
plugged and covered with clean fabric.
3.4 REPAIR OF DAMAGED SECTIONS
High Density Polyethylene Pipe (HDPE)
Sections of High Density Polyethylene pipe having cuts or gouges in excess of 10% of the wall
thickness of the pipe shall be removed. New polyethylene pipe section shall be rejoined using
the butt fusion joining method. The number of pipe joins shall be kept to a minimum number of
joints. The CQA ENGINEER shall advise the Ownder to reject pipe installations where in his/her
opinion, the CONTRACTOR’s installation methodology does not meet this objective.
3.5 PIPE JOINING
Perforated and Non-Perforated Pipe (HDPE)
Sections of High Density Polyethylene pipe and fittings shall be joined into continuous lengths on
the job site above ground. The joining method shall be the butt fusion method and shall be
Specifications and Contract Documents – Cell No. 14B
Uwharrie Regional MSW Landfill Montgomery, NC
March 2017 HHNT Project No. 6703-716-01

02722-4

performed by qualified persons and in strict accordance with the pipe manufacturer's
recommendations. The butt fusion equipment shall be capable of meeting all conditions
recommended by the pipe manufacturer, including, but not limited to, temperature
requirements, alignment and fusion pressures. Pipe will be fused at approximately 500oF with
minimum 150 psi fusion pressure.
3.6 HANDLING OF FUSED PIPE
Fused segments of High Density Polyethylene pipe shall be handled carefully to avoid damage to
the pipe. When lifting fused sections of pipe, chains or cable type chokers must not be used.
Nylon slings are required. Spreader bars are recommended when lifting long fused sections.
Care shall be exercised to avoid cutting or gouging the pipe.
3.7 TRENCHING AND BACKFILL
Pipe shall be laid as detailed in the Drawings. Pipe laid outside the landfill cell shall be laid in
accordance with Section 02220 - Trenching, Backfill and Compaction.
3.8 INSPECTION AND ACCEPTANCE
All Work shall be subject to inspection and approval prior to final acceptance and payment.
Final acceptance shall be contingent upon the following:
A. OWNER accepts the High Density Polyethylene pipe installation when the installation is
complete, all testing results are satisfactory, installation documentation and site
inspection is complete, and pipes have been flushed.
B. CONTRACTOR shall clean all HDPE pipe by water flushing. Beginning at cleanouts lines
shall be flushed until completely free of debris. CONTRACTOR shall recover and remove
all debris and flush water from the system and dispose of all debris in an
environmentally safe manner.
C. Final cleanup shall observed and documented by the CQA ENGINEER and approved by
the ENGINEER and/or the OWNER.

--END OF SECTION--