valpark drainage project

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College of Agriculture and Life Sciences

College of Engineering

ValPark Drainage Project

Jonathan GuthrieBrandon Thomas

Greg Turner

March 12, 2010


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ValPark Drainage ProjectGuthrie, Thomas, Turner

March 12, 2010BAE 472 - Irrigation and Drainage

Executive Summary

The ValPark Lot #3 experiences flooding after storm events and becomes muddy and difficult totravel. The 2 acre parking area is a well used lot that is used to generate income for the client. Theproblem was to remove the standing water and muddy conditions as well as reduce the sedimentloss that runs off of the lot and into Rocky Branch stream. Currently the discharge contains a highamount of sediment and soil loss is estimated at 43.9 Mg/yr. The design criterion were to be able todrain a 10-yr, 24-hr storm event without having any flooding and muddy conditions, lose no morethan 5% of available parking, and reduce soil loss while keeping maintenance requirements to aminimum. Cost was an issue as well as the lot is a for-profit venture. The project looked at various

solutions and a re-grading plan was chosen that uniformly distributed the slope so that the floodprone area had adequate slope for drainage. The re-grading plan also utilized existing subsurfacedrains that were poorly placed. The proposed design meets the criteria for parking loss by losingonly 5% of available parking and estimated soil loss is reduced to 30.6 Mg/yr.


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Table of Contents

Executive Summary ............................................................................................................................................ iTable of Contents .............................................................................................................................................. iiProblem Statement ............................................................................................................................................ 1Objectives & Constraints .................................................................................................................................. 2Solution Approaches ......................................................................................................................................... 2Analysis and Design Specifications ................................................................................................................. 3

Grading and Site Layout Design............................................................................................................. 3

Parking Space Marker Design ................................................................................................................. 4

Cost Statement ................................................................................................................................................... 5Operation & Maintenance Instructions .......................................................................................................... 6Critical Evaluation ............................................................................................................................................. 6Bibliography ........................................................................................................................................................ 8

Billing Log ........................................................................................................................................................... 9Appendices........................................................................................................................................................ 10

I.Stormwater Runoff and Sewer Calculations..................................................................................... 10

II. Soil Loss Calculations ....................................................................................................................... 12

III. Plan Drawings .................................................................................................................................. 13


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Problem Statement

ValkPark is a rental parking businlocated off of Hillsborough Streetadjacent to N.C. States Dan Allewest to east at a five percent aversloping lot closest to the Dan Allof vehicles traveling on the lot, sesouthern most point of the prope

subsurface drainage that is poorly

Figure 1:

ess that leases spaces to students at N.C. State Unin Raleigh, North Carolina. The area of concernParking Deck. As shown in Figures 1 and 2, Lo

ge grade. After a storm event water ponds at then Parking Deck. Also, due to lack of vegetation adiment is transported easily. A small stream is locrty that drains to Rocky Branch. The parking lot

placed and does not drain much of the water.

ValPark site map (Source: Wake County GIS).

Dan Allen D

Stream

Lot #3

iversity. It isis a 2-acre lott #3 slopes frombottom of thend the frequencyated at theas existing

ck


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Figure 2: ValPark bird's eye view (Source: 2010 Microsoft Corporation).

Objectives & Constraints

The main objective is to implement a design that will remove stormwater from the lot as quickly andefficiently as possible. This is critical to the parking lot being used after rain events without vehiclesbecoming soiled. The design should be as cost efficient and low-maintenance as possible andsediment loss from the lot should be minimized. Additionally, the lot is currently laid out to provide240 spaces and the design should minimize the number of spaces lost. The project constraints are

summarized below:

1. Completely drain parking lot after a 10-year, 24-hour storm event within the next 24 hours.2. Have a reduction in total available parking spots less than five percent.3. The design should require little to no maintenance.4. Reduce annual soil loss due to erosion.


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the lot to a drainage main that will run along the southern-most edge of the lot. The majordisadvantage of this design is that the ditches and ditch-to-main pipes will be a maintenance issue

due to clogging.

The other possible solution is to re-grade the entire lot in a way that will encourage sheetflow of water towards the three existing surface drains in the eastern end of the lot. This approachwill require a significant portion of earth to be removed at the west end of the lot for a cut/fill ratioof 1.3 to be achieved. In addition to re-grading, the railroad ties that are currently used as parkingpace markers will be replaced with makers fashioned from steel angle. This will help fix the problemof concentrated flow between the ties, which contributes to sediment loss. As in the other possible

solution, the parking clusters will be positioned parallel to the slope of the lot. This will positionvehicles perpendicular to the slope, which will reduce the cross-sectional area of vehicle tires to theflow path. This will reduce disruption to sheet flow of water as much as possible. This is the bestapproach due primarily to lower maintenance.

Analysis and Design Specifications

Grading and Site Layout Design

The main tool used in designing a grading plan for the proposed site was AutoCad Civil 3D2009. An existing topographic map and raster images of the surrounding area were obtained fromthe NCSU Libraries GIS data site (www.lib.ncsu.edu/gis). See Appendix III for the ExistingConditions Layout Sheet.

The proposed design allows for a more uniformly distributed stormwater runoff. A 3:1slope is specified at the entrance of the parking lot to increase cut volumes and to permit a smoother

slope in the parking area. To avoid the installation of new stormwater structures, the proposeddesign directs flow to the existing inlets. The design utilizes a 1.3 cut-fill ratio to allow forsettlement after construction as recommended by SWCE/e5, totaling the earthwork volume atapproximately 10,200 cubic yards. See Appendix III for the Proposed Grading Plan.

In designing the layout, the main objective was to maintain as many parking spaces aspossible while achieving successful drainage of the site. To prevent parked vehicles from impedingflow during a storm event, parking spaces were aligned perpendicular to the contours (See Appendix

III for the Proposed Layout). In the proposed design allocates for 227 parking spaces, which is95% of the original 240 spaces, thus meeting the projects design objective. Also, the existingrailroad ties being used for space designation obstructed runoff to the inlets. The design specifies anew parking space marker as described in the next section.

In order to use the existing drainage network, stormwater calculations were made to


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Another design objective was to reduce the amount of sediment lost annually due to erosion.Following the RUSLE model for estimating sediment transport, the current and proposed sediment

losses were calculated. An overall reduction of 30% was achieved with the proposed design; seeAppendix II for detailed calculations. Table 1 shows the estimated annual soil loss for bothconditions

Table 1: Estimated Annual Soil Loss for ValPark Lot #3

.

Parking Space Marker Design

The parking space markers will be made from 3 x 3 x 3/16 steel angle and will be 9 feet long,extend 1 foot above ground level, and extend 1.5 feet below the surface. The markers will not beanchored with concrete as this would hinder periodic removal for surface maintenance. As statedabove, the markers have a low height and deep anchor depth to minimize possible bendingmoments on the structures; this is necessary for the design because vehicles will inevitably drive overor otherwise apply forces to the structures. The main units, one of which is pictured in Figure 3below, will be constructed with 2 sections of bent angle iron with a cross-member welded betweenthem. There will be 38 of the pictured units installed in the center parking area of the lot, and each

unit will be spaced 8.5 feet apart. Separate 9-foot cross-members of the same size steel angle will bebolted between each main unit to create a continuous barrier along the entire length of each parkingcluster. 3/8 16 x 1 hex head coarse bolts and matching nuts will be used for this task. Thismethod of joining markers is necessary to allow for portability and land variations. Additionally, thisdesign minimizes material and manufacturing costs. Since ValPark assigns numbers to every parkingspace, a space number can be stenciled onto each side of the cross-members. If desired, every partmay be painted to resist corrosion. Parking along the perimeter of the lot can utilize the existingrailroad ties to demarcate spacing.

Existing 44Proposed 31

Reduction 30%

Annual Soil Loss

(Mg/yr)Plan


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Figure 3: Parking space marker main unit.

Cost Statement

Taking into account engineering design, labor, parking space marker construction and installationthe total cost for the project was estimated at slightly above $57,000. See Table 2 below for anitemized cost estimate.

Table 2: Itemized cost statement.

Item Description Quantity Unit Cost (USD) Extended Cost (USD)

Engineering Design (per hour) 70 100.00 7000Earthwork (per cubic yard) 10200 4.50 45900

Metal Work (per hour) 38 15.00 570

Marker Installation (per hour) 38 12.00 456

3" X 3" X 3/16" Steel Angle (per 18' length) 63 50.00 3150.00

3/8" - 16 X 1" Hex Head Bolt Coarse (per bolt) 292 0.27 78.84

1 of 4 bolt holes formounting cross-members

Cross-member

Below-ground depth of 1.5feet

Space number can be stenciled hereAbove-groundheight of 1 foot


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Operation & Maintenance Instructions

The grading plan is designed to keep maintenance at a minimum but some periodicmaintenance will be required. Annual grading of the gravel should be performed each spring tominimize erosion and prevent flooding problems from returning. This can be performed in the timeperiod between the end of the spring semester and the first summer session. The task should takeless than a day and is important to prevent future problems. A chain drag harrow will be pulledupslope to smooth and redistribute gravel and soil. A drag harrow can be purchased from agricultureor landscaping supply stores and models are available that can be pulled behind a truck. The use of ablade to redistribute the gravel may be required on a less frequent basis.

Another area of the design that requires maintenance is the drain system. The lot is graded tomove water towards the drains, thus any trash and debris that is easily transported will be directedtowards the drains and can collect on the grates or in the basin which can reduce the draining abilityand cause flooding.

Figure 4: Drop Inlet before re-grading

A weekly schedule is recommended to have landscapers or maintenance personnel removetrash and debris from the grates. At a minimum, monthly maintenance should be performed. Sometrash can slip through the grates and collect in the basin, thus it is important to check under the

grates and remove any trash that has collected in the basin to prevent clogging of the drain line.

Periodically, the parking space markers should be checked to make sure they have notbecome loose; if they have they can simply be re-set in their holes and new dirt can be compactedaround them.


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should be intercepted and redirected with the railroad tie parking space markers. After discussionwith Dr. Huffman, it was realized that this design would have concentrated flow in between ties,

which would cause sediment loss. More attention was then given to the existing drainage structuresand the main objective evolved to utilize these structures to minimize costs. The design succeeds atutilizing the existing drains by grading towards them. The design for the steel space markers allowswater to sheet flow, which will minimize sedimentation. However, the cost of the markers issignificant.

One design constraint that was difficult to meet was the conservation of parking spaces.With the specified design there is a five percent reduction in the number of parking spaces, which

meets the specified constraint. The intention of the design was to keep costs minimal whileachieving the desired results; paving the lot would be an easy solution but would be cost prohibitive.The stated cost of the project is significant but still lower than the cost of paving. Paving wouldrequire less maintenance but the initial cost would be much higher.


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Bibliography

Midwest Steel Supply Online Store. Midwest Steel Supply Co., 4 Mar. 2010. Web. 4 Mar. 2010..

NutsandBolts.com. Northeast Fasteners Co., Inc., 4 Mar. 2010. Web. 4 Mar. 2010..

EPA - Stormwater Menu of BMPs. US Environmental Protection Agency, 24 May 2006. Web. 4 Mar.2010. .

Fangmeier, Delmar D., William J. Elliot, Stephen R. Workman, Rodney L. Huffman, and Glenn O.Schwab. Soil and Water Conservation Engineering. Clifton Park, NY: Thompson Delmar Learning,2006. Print.


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Billing Log

Date Task Man-Hours1/13/2010 Research for Topic Statement 6

1/18/2010 Site visit 2



2/5/2010 Project planning/ Approaches 9

2/24/2010 ArcMap analysis 6

2/26/2010 ArcMap analysis 22/26/2010 Research 4

2/28/2010 AutoCAD analysis 4




3/5/2010 Research 4

3/9/2010 Research/ Analysis/ Report 33/10/2010 AutoCAD/ Research/ Report 9

3/11/2010 Analysis/ Report 9

Billable Hours: 70


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Appendices

I.Stormwater Runoff and Sewer CalculationsCheck existing drains by comparing runoff calculations using SCS-TR55 Method

Precipitation Frequency Estimates

For a 10yr- 24hr storm the precipitation depth is 128mm

For peak flow:

u p

3

3

u

q q AQF

,

peak runoff rate (m /s)

q = unit peak flow rate (m /s per ha/mm of RO)

A = watershed area (ha)

where

q

=

=


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Ia/P C0 C1 C2

0.1 2.5532 -0.6151 -0.164

0.3 2.4653 -0.6226 -0.1166

0.35 2.419 -0.6159 -0.0882

0.4 2.3641 -0.5986 -0.0562

0.45 2.2924 -0.5701 -0.0228

0.5 2.2028 -0.516 -0.0126

And

NumberCurveCN

(m/m)slopelandAverageSg

(m)lengthslopeL

,

)S(4407

9

1000

LT5.0

g

7.0

0.8

c

=

=

=

=

where

CN

The drainage area is 0.809 ha, the slope length to the drains is 71m. For a gravel parking lot with soilgroup B the curve number is 85. The Tc is found to be 4.5 min, which gives a qu of 0.001 m

3/s perha/mm. With the storm depth of mm, the peak flow is found to be 0.07 m3/s. To determine if thedrains are adequate compare to the capacity of the drains.

The existing drains use a 24 RCP main with = 0.012 to move water, so: = 610 = 4 (.610) = 0.292m = 2r = D = 1.916m

So using the Manning equation

= 1.012 0.292

1.916

(0.001) = 0.75/and = = 0.75 0.292 = 0.22 Since this is greater than the peak flow determined from the SCS-TR55 method the drains are

(hours)ionconcentratofTimeTc

tablein thefoundtscoefficienareC,C,C

,

10q

21o

)log(C36609.3C

u21o

=

=+

where

T cTC

c


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II. Soil Loss CalculationsIn order to estimate the soil loss for the existing and proposed sites, the RUSLE equations shown

below was used.

A=RKLSCP

A = average annual soil loss (Mg/ha)

R = rainfall and runoff erosivity index for geographic location

K = soil erodibility factor

L = slope length factor

S = slope steepness factorC = cover management factor

P = conservation practice factor

For Raleigh the estimated R-factor is 4200 according to Figure 7-3 in SWCE/5e. The K-factor forCecil soil found on the site is 0.033. The L factor is based on the slope length, field slope angle, anda dimensionless component, b. Equations are shown below.

lengthslope

factorlengthslope

,

22L

exponentessdimensionl

,

05.0)(sin269.0sin

sin

steepnessslopes

angleslopefield

where,

)(tan

8.0

1

=

=

=

=

++

=

=

=

=

l

l

L

where

b

where

b

s

b

The S-Factor equation is dependent on the actual field slope and slope length. For a slope less than9 percent and greater than 4 meters long, the following equation was used:

03i810 S


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annual soil loss for each condition. Changes in the proposed site showed an annual soil lossreduction of approximately 30%. The table below shows a summary of the input parameters to

arrive at this solution.

III. Plan Drawings

See attached.

Plan s (deg) (rads) b l (m) R K L S C P A (Mg/ha/yr)Annual Soil

Loss (Mg/yr)

Existing 0.048 2.75 0.05 0.394 71 4200 0.033 1.587 0.548 0.45 1.0 54.2 43.9

Proposed 0.035 2.00 0.03 0.338 71 4200 0.033 1.487 0.408 0.45 1.0 37.8 30.6


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