Appendix F - Bridge Replacement Scoping Form & Preliminary … · 2016. 9. 26. · The proposed design typical section for the road between the project limit tie-ins and the bridge

US 21 Bridge Replacement over Harbor River South Carolina Department of TransportationAppendix F - Bridge Replacement Scoping Trip Risk Assessment Form & Preliminary Stormwater Management Design Study

Environmental Assessment P026862

FAppendix F - Bridge Replacement Scoping Trip Risk Assessment Form & Preliminary Stormwater Management Design Study

South Carolina Department of Transportation US 21 Bridge Replacement over Harbor RiverAppendix F - Bridge Replacement Scoping Trip Risk Assessment Form & Preliminary Stormwater Management Design Study

P026862 Environmental Assessment

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COUNTY: DATE:

ROAD #: STREAM CROSSING:

Purpose & Need for the Project:

I. FEMA Acknowledgement

Is this project located in a regulated FEMA Floodway? Yes No

Panel Number: Effective Date: (See Attached)

II. FEMA Floodmap Investigation

FEMA Flood Profile Sheet Number illustrates the existing 100 year flood:

Passes under the existing low chord elevation.

Is in contact with the existing low chord elevation.

Overtops the existing bridge finished grade elevation.

III. No Rise/CLOMR Preliminary Determination

Preliminary assessment indicates this project may be constructed to meet the

"No-Rise" requirements. A detailed hydraulic analysis will be performed to verify

this assessment.

Justification:

Preliminary assessmnet indicates this project may require a CLOMR/LOMR.

Impacts will be determined by a detailed hydraulic analysis.

Justification:

BRIDGE SCOPE AND RISK ASSESSMENT FORM

Page 1 of 4

bstokesText Box450025 0162 E

IV. Preliminary Bridge Assessment

A. Locate Existing Plans

a. Bridge Plans Yes File No. Sheet No. (See Attached)

No

b. Road Plans Yes File No. Sheet No. (See Attached)

No

B. Historical Highwater Data

a. USGS Gage Yes Gage No. Results:

No

b. SCDOT/USGS Documented Highwater Elevations

Yes Results:

No

c. Existing Plans Yes See Above

No

V. Field Review

A. Existing Bridge

Length: ft. Width: ft. Max. span Length: ft.

Alignment: Tangent Curved

Bridge Skewed: Yes No Angle:

End Abutment Type:

Riprap on End Fills: Yes No Condition:

Superstructure Type:

Substructure Type:

Utilities Present: Yes No

Describe:

Debris Accumulation on Bridge: Percent Blocked Horizontally: %

Percent Blocked Vertically: %

Hydraulic Problems: Yes No

Describe:


Page 2 of 4

V. Field Review (cont.)

B. Hydraulic Features

a. Scour Present: Yes No Location:

b. Distance from F.G. to Normal Water Elevation: ft.

c. Distance from Low Steel to Normal Water Elev.: ft.

d. Distance from F.G. to High Water Elevation: ft.

e. Distance from Low Steel to High Water Elev.: ft.

f. Channel Banks Stable: Yes No

Describe:

g. Soil Type:

h. Exposed Rock: Yes No Location:

i. Give Description and Location of any structures or other property that could be

damaged due to additional backwater.

C. Existing Roadway Geometry

a. Can the existing roadway be closed for an On-Alignment Bridge Replacement

Yes No

Describe:

If "yes", does the existing vertical and horizontal curves meet the proposed

design speed criteria?

If "No", will the proposed bridge be:

Staged Constructed

Replaced on New Alignment


Page 3 of 4

bstokesText BoxMean Tide Level: -0.46'Mean High Water: +2.58'

bstokesText BoxF.G. and Low Steel elevs. are minimum elevs. on ex. bridge.

VI. Field Review (cont.)

A. Proposed Bridge Recommendation:

Length: ft. Width: ft. Elevation: ft.

Span Arangement:

Notes:

Performed By:


BRIDGE SITE DIAGRAM: (Show North Arrow and Direction of Flow)

Page 4 of 4

bstokesText Box 21.85 ft. Min.

bstokesText BoxMax.

bstokesLine

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Preliminary Stormwater Management Design Study US 21 (Sea Island Parkway) Harbor River Bridge Replacement

ii | June 28, 2016

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1

2

IntrodThe SouthHighway 2existing brHarbor Rivinvolves rebridge on in a rural aon either s

The existithat is 24-bridge concreating ais collectewetlands. project lim

The projecEstuarine habitats asands.

DrainThe hydrofor Hydraudesigned wbe used todrainage avalues for details the

ductionh Carolina De21 Bridge overidge to be rever, to conneeplacement onew alignme

area and the side.

ng 2,851-foo-feet wide witnsists of two causeway a

ed by scuppeThere are no

mits.

ct site is locasystems arend adjacent

nage Dologic analysiulic Design Swith Geopako determine pareas will be Hilton Head

e drainage de

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n/Existepartment of er the Harboeplaced is 0.5ect Saint Heleof the existinent and tying roadway cor

ot long bridgeth two 10-foo12-foot drivin

across the mars that dischao closed drai

ated in a rurae found withintidal wetland

Design is is to be pe

Studies datedk Drainage uspeak runoff vless than 10 most represesign criteria


ting Cof Transportatir River in Be54 miles longena Island ang swing-spanback in to th

rridor consist

e over the Haot driving laneng lanes witharshy floodplarge directly inage system

l area and lien the study pds. The pred

Criterierformed in ad May 26, 200sing a 10-yeavalues for sto00 acres. Thesent the rainf

for the proje


onditionion proposes

eaufort Countg and spans nd Harbor Isn bridge withhe existing rots of marshe

arbor River ises. The existh 4-foot pavelains. Runoffinto the Har

ms or major d

es within the roject corridoominant soils

a ccordance w09. Storm drar design stoorm drainagee published Sfall pattern foect.


ns s to replace tty, South Caa navigable land. The pro

h a proposedoad. The projs, wetlands,

s a center swting road on eed shoulders f from the exibor River an

drainage cros

100-year floor and includs consist of m

with SCDOT’srainage systeorm. The Rate calculationsSCDOT rainfor the project


June 28, 20

the existing Urolina. The waterway, thoposed proje fixed, high leject site is locand water bo

wing-span brideither end ofand is built o

isting bridged bordering ssings within

oodplain. de deepwatermuddy, fine

s Requiremeems will be ional Method

s since all fall intensity site. Table 2

016 | 1

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2 | June 28, 2016

Table 2-1. Drainage Design Criteria DRAINAGE DESIGN

DESIGN ELEMENT DESIGN CRITERIA SOURCE

Design Discharge

Cross-Line Pipes 50-year SCDOT Requirements for Hydraulic Design Studies, May 26, 2009 Section 2.2.2 and 2.2.3

Systems and Ditches

0 – 40 AC 10-year

40 – 500 AC 25-year

> 500 AC 50-year

Spread Criteria

Roadway Design Storm 10-year SCDOT Requirements for Hydraulic

Design Studies, May 26, 2009 Section 2.2.4 Spread Width ½ travel lane

Bridge Design Storm 10-year

HEC-21, Section 3.1 Spread Width Shoulder Width

Minimum Ditch and Pipe Grades Ditch = 0.1%, Pipe = 0.3% SCDOT Requirements for Hydraulic Design Studies, May 26, 2009 Section 2.2.5 Minimum Velocity of Pipe 3 ft/sec

Minimum Pipe Size

Storm Drainage Systems & Cross-Line Pipes 18" SCDOT Requirements for Hydraulic

Design Studies, May 26, 2009 Section 2.2.6 Yard Drains & Driveway

Pipes 15"

Minimum Cover

Yard Drains 1.0' SCDOT Requirements for Hydraulic Design Studies, May 26, 2009 Section 2.2.7 Pipes except Yard Drains

2.0' for CB-16 3.0’ for CB-17 & 18

Grassed swales are to be designed in accordance with SCDOT’s Stormwater Quality Design Manual. A grassed swale is allowed a maximum drainage area of 5 acres to properly treat the runoff. It must be capable of conveying the 10-year, 24-hour storm event without overtopping or reaching erosive peak runoff velocities and shear stresses.

3 Proposed Conditions The proposed design typical section for the road between the project limit tie-ins and the bridge consists of two 12-foot travel lanes and two 10-foot shoulders, in which 4-feet of the shoulders will be paved. The bridge consists of two 12-foot travel lanes and two 10-foot paved shoulders.

Conceptual drainage designs were prepared for each of the five proposed bridge alternatives. The proposed drainage designs consist of deck drains spaced throughout the bridge where runoff will be collected in closed drainage systems suspended underneath the bridge. The bridge deck drain systems are proposed to tie to manholes located at the ends of the bridge. Closed drainage will convey the bridge runoff from the manholes into grassed swales. The grassed swales will provide water quality treatment before outfalling into the surrounding marshes and outside of 1,000-feet away from shellfish beds, per OCRM requirements.

4

5

The deck less than within the was deterthat a12-indrainage s

Catch basthe approaon superesystems to

Smooth wminimum used in th

TempThroughomaintainefence will or streams

Inlet protethe proposdrop inlet located in

Appropriareduce dis

All erosionfrom Sect

PermThe drainawill conveoutfalling constructewater qua100-feet wthroughoustresses. Tside slope

In Alternatcreated beand grass

drains closes10-feet. Decshoulder andmined that dnch diametersystem off of

sins should bach slabs an

elevated sideo the roadwa

wall pipe will bpipe grade ine roadway d

porary ut the duratiod at the consbe placed whs.

ection is to besed improvemlocations andthe curb and

tely sized enscharge velo

n control meaions 804 and

manent age systemsy the runoff tinto the marsed and maintlity BMPs. Th

with a 2-foot wut to achieve The minimum

es will be no s

tives 1A, 1B,etween the psed swales w

US

st to the cresk drains shoud that 0 cfs weck drains wr PVC pipe wf the bridge.

e placed at td to tie in thes of the road

ay drainage s

be used to con the systemrainage syste

Sedimon of the projstruction limithere the con

e provided atments. Type d Type E andd gutter secti

nergy dissipacities.

asures were d 815.

Waters are proposeto a distanceshes. The lastained per SChe proposedwide base anwater quality

m longitudinasteeper than

, and 3, the dproposed roawill run adjace


st of the bridguld then be swill run off of with 6-inch diawould convey

the ends of the bridge deckdway in lieu osystems.

onvey the runs should be 0ems is 18-inc

ment anject, a singlets along the lstruction imp

t all existing aB Inlet Struc

d F Inlet Struons.

ters will be in

proposed ac

r Qualied to outfall a greater thanst 100-feet ofCDOT’s Storm grassed swand 0.5-foot hiy benefits anal grade reco 2H:1V.

ditches and gdway fill slop

ent to the fill s


ge should bespaced so thathe bridge at

ameter openy the runoff fr

he approach k drain systeof catch basin

noff in the clo0.3 percent. ch diameter.

nd Eroe row of silt felength of the pacts are adj

and proposedcture Filters wucture Filters

nstalled at al

ccording to S

ity Conat each end on 1,000-feet ff the ditches mwater Quaales will haveigh earthen fd reduce run

ommended is

grassed swalpes and the eslopes to bey


e placed so that the spreadt its ends. Things would crom the deck

slabs to collems. Manholens to tie the b

osed drainagThe minimum

osion Cence will be iproject. A doacent to mar

d inlets that awill be used awill be used

l storm drain

SCDOT Stand

nsideraof the bridge from shellfishshould be grlity Design Me a minimumflow control snoff velocitiess 0.5 percent

es are propoexisting roadwyond the 1,00


June 28, 20

hat spread wd will remain hrough analycollect runoff k drains to the

ect runoff froes should bebridge deck d

ge systems. Tm pipe size t

Controlnstalled and ouble row of rshes, wetlan

are impactedat manhole a at catch bas

age outlets t

dard Drawing

ationsinto ditches

h beds beforerassed swale

Manual to prom flow length structures sps and shear . Front and b

osed to be way. The ditc00-foot shellf

016 | 3

will be

ysis, it and e

om used

drain

The to be

silt nds,

d by and sins

to

gs

that e es ovide

of aced

back

ches fish


4 | June 28, 2016

bed minimum distance and then can discharge directly to the marsh. By utilizing the existing causeway section that will be abandoned, construction disturbance impacts to the surrounding wetlands will be minimized.

In Alternatives 2A and 2B, the roadway alignments are further from the existing corridor. To pipe the drainage systems to a point where the fill slopes meet to create swales similar to that in Alternatives 1A, 1B, and 3 would create systems lower than the existing ground they would outfall upon. Therefore, it is suggested that the drainage systems be piped to a distance near the 1,000-foot shellfish bed minimum and then outfall into grassed swales that are constructed into berms along the fill slopes of the proposed roadway. The grassed swales on the berms will treat the runoff for 100-feet and then discharge directly into the marsh.

6 Project Maps See Figures 1 through 7 for the project’s vicinity, location, quad mapping, soils, FEMA flood information, and drainage areas.

Figure 66-1. Vicinity

Map

USPrelimin

S 21 (Sea Island nary Stormwater Parkway) Harbo



June 28, 20016 | 5


6 | June 28, 2016

Figure 6-2. Location Map

Figure 6

6-3. USGS QQuad Map

USPrelimin




June 28, 20016 | 7


8 | June 28, 2016

Figure 6-4. Soils Map

Figure 66-5. FEMA F

lood Map

USPrelimin




June 28, 20016 | 9


10 | June 28, 2016

Figure 6-6. FEMA Flood Map

Appendix F NEPABridgeScope_RiskAssessmentFormAppendix F SC21 Harbor River Bridge Hydro Report_2016.06.28US 21 Bridge Replacement over Harbor River Environmental Assessment_20160819 149US 21 Bridge Replacement over Harbor River Environmental Assessment_20160819 150

Yes: XNo: Results: Length: 2,851Max span Length: 85.2Angle: End Abutment Type: Concrete CapCondition: Little riprap on west end. Superstructure Type: Concrete deck.Substructure Type: Steel girders on concrete caps and piles. Percent Blocked Horizontally: 0Percent Blocked Vertically: 0Location: No scour observed on banks. Distance from FG to Normal Water Elevation: 11.76Distance from Low Steel to Normal Water Elev: 9.76Distance from FG to High Water Elevation: 8.72Distance from Low Steel to High Water Elev: 6.72Soil Type: Muddy, fine sands.damaged due to additional backwater: Due to the vast floodplains of the surroundings marshlands, backwater from the bridge should not affect any property of structures. However, nearby Saint Helena Island and Harbor Island contain structures located in flood zones. Power lines on concrete piles are present south of the existing bridge. Describe: Existing bridge is only means of vehicular transportation to and from islands south east of Saint Helena Island. Length_2: 3,602Elevation: 89.00Span Arangement: 16 @ 126'-0" / 13 @ 122'-0"Notes 1: Performed By: Brandon StokesIs in contact with the existing low chord elevation: OffOvertops the existing bridge finished grade elevation: OffPasses under the existing low chord elevation: OffPreliminary assessment indicates this project may be constructed to meet the No-Rise requirements: YesPreliminary assessment indicates this project may require a CLOMR/LOMR: OffNo - Bridge Plans: OffYes - Road Plans: YesNo - Road Plans: OffYes - Historical Highwater Data: OffNo - Historical Highwater Data: OffYes - SCDOT/USGS Document Highwater Elevations: OffYes - Bridge Plans: YesNo - SCDOT/USGS Document Highwater Elevations: OffYes - Existing Plans: YesNo - Existing Plans: OffWidth: 47Tangent: YesCurved: OffYes - Bridge Skewed: OffNo - Bridge Skewed: YesYes - Riprap on End Fills: YesNo - Riprap on End Fills: OffYes - Utilities Present: YesNo - Utilities Present: OffYes - Hydraulic Problems: OffNo - Hydraulic Problems: YesDescription - Hydraulic Problems: Shellfish (oysters/barnicles) are growing on bridge piles, slightly reducing the hydraulic opening under the bridge.Description - Utilities Present: DIP connected to north and south side of bridge, as well as electrical conduit on south side. Power lines run parallel to bridge on south side.Yes - Scour Present: OffNo - Scour Present: YesYes - Channel Banks Stable: YesNo - Channel Banks Stable: OffDescription - Channel Banks Stable: Channel banks consist of march grass and oyster beds. Yes - Exposed Rock: OffNo - Exposed Rock: YesLocation - Exposed Rock: Yes - Can existing roadway be closed: OffNo - Can existing roadway be closed: YesStaged Constructed: OffReplaced on New Alignment: YesDesign speed criteria: N/AFile No: 7.629File No_2: 7.223/7.230Gage No: Results 1: Sheet No_2: Sheet No: 42-76Justification for CLOMR/LOMR: Justification for No-Rise requirements: The proposed bridge will be longer than the existing bridge and maintain the existing bridge low chord at a minimum, providing a larger hydraulic opening. This will increase the floodplain limits under the bridge and, therefore, there should be no increase in the flood profile. Purpose Need for the Project: The existing US Highway 21 Bridge over Harbor River located in Beaufort County, SC is to be replaced by a bridge on new alignment. The existing bridge is classified as structurally and functionally obsolete. Panel Number: 450025 0135 EFEMA Flood Profile Sheet Number: N/AEffective Date: 11/04/1992County: [Beaufort]Date: 06/28/2016Road: US 21Stream Crossing: Harbor River

Documents

Appendix F - Bridge Replacement Scoping Form & Preliminary … · 2016. 9. 26. · The proposed design typical section for the road between the project limit tie-ins and the bridge