priority scour critical bridge countermeasure plan of ...gis.dot.nh.gov/bridge_scour/hudson...

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Attachment D: Bridge Elevation Summary Showing Existing Streambed, Foundation Depth(s) and Observed and/or Calculated Scour Depths

The Following Materials Are Being Submitted With This Report:

Attachment H: Plan View Showing Location of Scour Holes, Debris, etc,

Attachment B: Map Showing Detour Route(s)

Attachment E: Boring Logs and/or Other Subsurface Information

Attachment F: Survey Cross Sections From Current and Previous Inspection Reports

Attachment G: Supporting Documentation, Calculations, Estimates, and Conceptual Designs for Scour Countermeasures

Attachment A: Photos

Attachment C: Field Verification Card (FVC)

Feature Crossed: Merrimack River

Feature Carried: NH Route 111 WB

Owner: Municipality

New HampshireDepartment of Transportation

Scour Critical BridgePlan of Action (POA) Report

Final Recommended Action:Currently, this bridge has no reported flood history and up to 17 feet of pier scour was predicted. A geotechnical assessment was performed on Pier 3 to determine if the rating could be revised to non-scour critical. Based on the assessment, the bridge remains scour critical and CHA recommends that A-Jack countermeasures be set in place to protect Pier 3. CHA also recommends that the bridge be monitored during and after significant flood events until the A-Jack countermeasures are installed.

Hudson 109/068

POA Report

Scour POA Priority:

Attachment I: Post Flood Inspection Documentation

Post Flood Inspection Tasks

Flood Monitoring Program

Conceptual Structural / Hydraulic Countermeasures

Fixed Monitoring Devices

Increased Inspection Frequency

Priority Countermeasure

PriorityMonitoring

Attachment J: Scour / H&H Backup Calculations

Attachment K: NHDOT Underwater Inspection Report

SCOUR CRITICAL BRIDGE − PLAN OF ACTIONHudson 109/068

1. GENERAL INFORMATIONStructure:

Year Built:

109/068

1970

City, County, State:

Hudson, Hillsborough, New Hampshire

State Highway or Facility Carried:

NH Route 111 WB

Waterway Crossed:

Merrimack River

Owner:

Municipality

Year Rebuilt:

NA

Planned Bridge Replacement (if scheduled):

Anticipated Opening Date:

The superstructure is a 4 span continuous steel multi-girder with a concrete deck. The abutments and piers are concrete. Both abutments and Pier 3 (CHA identification of West Pier) are supported by steel piles and Piers 1 & 2 are supported on concrete seals on ledge rock. Plans are available from 1968.

Structure Size and Description:

Foundation Details:

KNOWN UNKNOWN

Subsurface SoilInformation:

Bridge ADT Info:

Does the Bridge Provide Service to Emergency Facilities and/or an Evacuation Route (Y/N)?:

Bridge on a Major Route.If So, Describe:

WorstAbutment: Left

WorstPier: 3

(Looking Downstream L to R)

Channel Primary Bed Material:

Sand

Channel Secondary Bed Material:

Glacial Till

Embedment (feet): unknown Exposure: None

Embedment (feet): 12 Exposure: Footing Exposed

Scour Summary

Based on information included in the Hillsborough Countywide FIS (6-2004), the Merrimack River has not experienced a significant flood event since the bridge was constructed in 1970. According to the FEMA Independent Evaluation of Recent Flooding in New Hampshire (7-08), Merrimack River flooded near Manchester, NH in 2006 and 2007, with recurrence intervals of 10-50 years.

Flood History:

The superstructure is a 4 span continuous steel multi-girder with a concrete deck originally built in 1970 that has not been reconstructed. Plans are available from 1968. Abutments are composed of concrete, founded on EB piles, and set back from the main channel. Pier 3 (west, pier 1 per the plans) is composed of concrete, founded on piles (30 feet), and located in the channel. Piers 1 & 2 are composed of concrete, located in the channel and founded on spread footings with concrete foundation seals extending to bedrock per plans (14 ft & 10 ft thick min). The design plans (1969) note slope protection at both abutments (stone fill, 6 ft thick). The latest NHDOT Underwater Inspection Report (2005) indicates footing exposure at all of the piers. The report also notes debris at the nose of Pier 2 and 3, as well as rip-rap along its western edge of Pier 2. The foundation seals are exposed at Pier 1 and 2 up to 3.5 and 8 feet, respectively. The remaining embedment is 9.5 feet for footings and Pier 1 and 9 feet for Pier 2, however the design plans indicate that both foundation concrete minimum seals extend to rock. In addition, the footing at Pier 3 is exposed up to 1 foot, leaving a remaining pile cap embedment of 12 feet.

Field Observation:

The Hillsborough Countywide FIS provides water surface elevation and flow data for bridge. This information was used along with a field soil classification and boring data (sandy till) in order to develop pier scour estimates for the 100-year flood event. The result of this computation indicates the potential for 17 feet of scour at Pier 3, which given the embedment referenced from the 2005 diving report would expose approximately 5 feet of the pile foundation.

Scour Calculations:

Current Item 113 Code: 3 Source of Scour Critical Code: Calculation

Borings:

Yes No

Bridge Maintenance Division5

200535005 Year:Total:

Text9:6/23/2010 Text9:Scour Critical Bridge - Plan of Action: Hudson 109/068 Text9: Page 1 of 6

5. MONITORING PROGRAM RECOMMENDED5a. Regular Inspection Program

Riverbed Profile Readings

Items toWatch:

Changes to the embedments at Piers. All piers have exposed footings. The footings and foundation seals are exposed at Pier 1 and 2 up to 3.5 and 8 feet, respectively. The remaining embedment is 9.5 feet for Pier 1 and 9 feet for Pier 2. The footing at Pier 3 is exposed up to 1 foot, leaving a remaining pile cap embedment of 12 feet. Provide photo documentation of countermeasures at piers.

5b. Fixed Monitoring Device(s)

Type of Instrument:

Installation Location(s):

Sample Interval: 30 min 1 hr. 6 hrs. 12 hrs. Other:

Frequency of Data Download and Review: Daily Weekly Monthly Other:

Scour Critical Elevation(s) For Each Pier:

Criteria of Termination For Fixed Monitoring:

Standard 2 Year Interval

Underwater Inspection Required Items toWatch:

Changes to the embedments at Piers. All piers have exposed footings. The foundation seals are exposed at Pier 1 and 2 up to 3.5 and 8 feet, respectively. The remaining embedment is 9.5 feet for Pier 1 and 9 feet for Pier 2. The footing at Pier 3 is exposed up to 1 foot, leaving a remaining pile cap embedment of 12 feet. Provide photo documentation of countermeasures at piers.

Standard 5 Year Interval

2 Year Interval

1 Year Interval

5c. Flood Monitoring Program

Type:

Discharge

Visual Inspection

Instrument (check all that apply)

Portable Geophysical SonarOther:

(check all that apply)

Flood Monitoring event defined by:

Stage (WSE)

Frequency of Flood Monitoring: 1 hr. 3 hrs. 6 hrs. Other:

Notified By Public

Flood Warning Issued by NWS

Notified by Fixed Monitoring Device

USGS Gage Station #

1 Year Interval

Criteria to End Flood MonitoringConditions Stable / Water Receding

Recommended Post Flood Inspection

Action(s) Required if Scour Critical Elevation Detected: (See Section 7 and Section 8)

Not Applicable:

During PrecipitationEvent, Look For:

Water surface at or above placard elevation.

Revisit Bridge

Close Bridge (See Section 7)

Placard Location: Piers 1 and 3 at the upstream bridge fascia.

Contact Person(s):NHDOT Bridge Design Bureau, Bridge Inspector1.

NHDOT Bridge Maintenance Divisional Superintendent Crew# 52.

NHDOT Bridge Maintenance Divisional Foreman Crew# 53.

NHDOT Bridge Design Bureau, Existing Bridge Section4.

NHDOT Bridge Design Bureau, Administrator5.

Stage (WSE)

NOAA Gage Station #

Scour Critical Riverbed Elevation(s) for Each Pier/Abutment: 1 ft above bottom footing elevation - See Attachment D

NOTE: Additional Details for Action(s) Required May Be Included in Sections 7 and 8.

Action(s) Required if Scour Critical Riverbed Elevation Detected:

Assess changes in channel/riverbed profiles, changes in pier embedment, possible undermining and overall structure stability. Consider closing bridge.

Agency and Department Responsible for Monitoring:

NHDOT

Contact Person:

NHDOT Bridge Design Bureau (603) 271-2731

Riverbed Profile Readings (See Attachment I)

Items toWatch:

Changes to the embedments at Piers. All piers have exposed footings. The footing and foundation seals are exposed at Pier 1 and 2 up to 3.5 and 8 feet, respectively. The remaining embedment is 9.5 feet for Pier 1 and 9 feet for Pier 2. The footing at Pier 3 is exposed up to 1 foot, leaving a remaining pile cap embedment of 12 feet. Provide photo documentation of countermeasures at piers.

5d. Post-Flood Inspection Tasks Required

Visual Inspection (See Attachment I)

Profile at Substructure (See Attachment I)

Undermining (See Attachment I)


6. COUNTERMEASURE RECOMMENDATIONS

Conceptual Structural / Hydraulic Countermeasures

Basis for the Selection of the Preferred Scour Countermeasure:

Include Information on Hydraulic, Structural or Monitoring Countermeasures.

(1) A-Jacks around Pier 3

Estimated Cost

$ 350,000

(2) $

(3) $

Depth of water requires A-Jacks

Countermeasure Implementation Project Type:

Proposed Construction

Other:

Bridge Maintenance

Programmed Construction - Project Lead Agency

Bridge Design

Highway Design

Recommended Countermeasures to be Performed by:

NHDOT

Contact Person:


Post Flood Inspection Tasks Required

Flood Monitoring Program

Fixed Monitoring Devices

Regular Inspection Program

Lead Agency:

Conceptual Cost Estimate:

H & H Summary Information:

121.7

130.3

85000

102000

148000

109.5

113

120.5

50 year

Flow (cfs) Elevation (ft)

100 year

500 year

Roadway

Low Chord

Flow Impacting Bridge Flow Overtopping Bridge

No

No

No

No

No

No

53000 10410 year No No


7. BRIDGE CLOSURE PLAN

Scour Measurement Results / Monitoring Device (See Section 5)

Criteria For Consideration of Bridge Closure:

Observed Structure Movement / Settlement

Water Surface Elevation Reaches Low Chord

Overtopping Road or Structure

Other: Debris Accumulation Movement of RipRap/Other Armor Protection Loss of Road Embankment

Agency and Department Responsible for Closure:

Contact Person(s):

NHDOT Bridge Design Bureau, Bridge Inspector

(See Attachment C)

Water Reaches Critical Elevation: 109.5 ft NAVD88, placard (50-yr event)

NHDOT Municipality:Transportation Management Center

1.

NHDOT Bridge Maintenance Divisional Superintendent Crew# 52.

NHDOT Bridge Maintenance Divisional Foreman Crew# 53.

NHDOT Bridge Design Bureau, Existing Bridge Section4.

NHDOT Bridge Design Bureau, Administrator5.

Ice Jam

DischargeStage (WSE)USGS Gage Station #

Stage (WSE)NOAA Gage Station #

8. DETOUR ROUTEDetour Route Description: (See Attachment B)

Bridges on Detour Route:

Bridge NumberFeatureCrossed

Load Posting (tons) (Date)

Item 113Code

Traffic Control Equipment (detour signing and barriers) and storage location(s) (NHDOT/Town): NHDOT Bridge Maintenance Divisional Crew 5

Additional Considerations or Critical Issues (susceptibility to overtopping, limited waterway adequacy, lane restrictions, etc.):


News Release, Other Public Notice (include authorized person(s), information to be provided and limitations):

NHDOT Public Information Officer, NHDOT Bridge Design Bureau (603) 271-2731

FeatureCarried

VerticalClearance

(feet)

WidthRestrictions

(feet)

HighwayMaintenance

District: 05

NHDOT Bureauof Traffic

Nashua 132/098 SALMON BROOK 21.8 (N/A)8DANIEL WEBSTER HW unrestricted 55.8


9. BRIDGE REOPENING PLAN9a. Criteria for Consideration to Complete Interim Bridge Reopening:

Agency and Person Responsible for Re-Opening Bridge After Inspection:


Post Flood Inspection Completed

Critical Elevation Marker Is Visible

Reasons for Closure Have Abated

Water Surface Levels Dropping

Diving Inspection Completed within 7 calendar days

Verify Riverbed Elevation (drop line readings)

Streambed Elevation Drops Less than

Streambed Elevation 1.0 Feet

3 Feet

9b. Criteria for Completing Bridge Reopening Process:

Above Critical Footing Elevation. (See Section 5d)


Bridge: Hudson 109/068

Date Taken: 7/29/2009 2:33:52 PM

Description: Upstream Elevation

Source: CHA

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Date Taken: 7/29/2009 2:34:58 PM

Description: Downstream Elevation

Source: CHA

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Text9:6/23/2010 Text9:Attachment A: Bridge Photos: Hudson 109/068 Text9: Page 1 of 4


Date Taken: 7/29/2009 2:27:42 PM

Description: Left Abutment

Source: CHA

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Date Taken: 7/29/2009 2:27:24 PM

Description: Pier1

Source: CHA

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Date Taken: 7/29/2009 2:36:24 PM

Description: Pier 3

Source: CHA

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Date Taken: 7/31/2009 8:20:56 AM

Description: Right Abutment

Source: CHA

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Date Taken: 7/31/2009 8:20:51 AM

Description: Upstream Channel

Source: CHA

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11 King Court

Keene, NH 03431-4648

Main: (603)-357-2445

New Hampshire Scour Investigation

Hudson 109/068

Attachment B: Detour Route

Hudson

109/068

GOING WEST ON NH 111

DETOUR MAP


Detour (miles): Last ADT:

Foundation Details:

KNOWN

UNKNOWN Worst Abutment: Left

Worst Pier: 3(Looking Downstream L to R)



Diving Insp Reports: 10/20/2005

FIELD VERIFICATION CARD (POA Attachment C)

Owner: Municipality



Town, County: Hudson - Hillsborough

Contact Person: NHDOT Bridge Design Bureau (603) 271-2731

BRIDGE INFORMATION

Superstructure Type: Stringer/Multi-Beam or Girder

Superstructure Material: Steel

Scour Critical Feature: Pier 3


Red List: No

Number of Spans: 4

USGS Gage Station: USGS Station Prox To Bridge:

GENERAL INFORMATION

Scour Measurement Results / Monitoring Device

CRITERIA FOR CONSIDERATION OF BRIDGE CLOSURE

Observed Structure Movement / Settlement

Water Surface Elevation Reaches Low Chord

Overtopping Road or Structure

Date/TimeNotified:

Completed ProperNotification

Close BridgeRevisit BridgePost-Flood Inspection Recommendation

POST-MONITORING VERIFICATION

ACTION TAKEN

REFERENCE PHOTOS

Dates:

Water Reaches Critical Elevation: 109.5 ft NAVD88, placard (50-yr event)

Agency:

What To Look For: Changes to the embedments at Piers. All piers have exposed footings. The footing and foundation seals are exposed at Pier 1 and 2 up to 3.5 and 8 feet, respectively. The remaining embedment is 9.5 feet for Pier 1 and 9 feet for Pier 2. The footing at Pier 3 is exposed up to 1 foot, leaving a remaining pile cap embedment of 12 feet.

(Left to Right Convention Looking Downstream)

CRITERIA FOR CONSIDERATION TO COMPLETE INTERIM BRIDGE REOPENING:

Agency and Person Responsible for Re-Opening Bridge After Inspection:


Critical Elevation Marker Is Visible

Reasons for Closure Have Abated

Water Surface Levels Dropping

Verify Riverbed Elevation

Above Critical Footing Elevation. (See Section 5d)

(Continued on Next Page)

Interim Reopening Date:Interim Reopening Approved By: Time:

INTERIM REOPENING COMMENTS

Traffic Control Equipment (detour signing and barriers) and storage location(s) (NHDOT/Town): NHDOT Bridge Maintenance Divisional Crew 5

HighwayMaintenance

District: 05

NHDOT Bureauof Traffic

Streambed Elevation Drops Less than

Streambed Elevation 1.0 Feet

3 Feet

Other: Debris Accumulation Movement of RipRap/Other Armor Protection Loss of Road Embankment Ice Jam

DischargeStage (WSE)USGS Gage Station #

Stage (WSE)NOAA Gage Station #

NOAA Gage Station: NOAA Station Prox To Bridge:

10 200535005 Year:Total:

Text9:6/23/2010 Text9:Attachment C: Field Verification Card: Hudson 109/068 Text9: Page 1 of 2

Upstream Low Water

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Upstream Elevation of Bridge at Low Water

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Scour Critical Feature at Low Water

DocID_11842.JPG

Text9:6/23/2010 Text9:Attachment C: Field Verification Card: Hudson 109/068 Text9: Page 2 of 2

ROADWAY

ELEVATION (FT)

LOW CHORD

ELEVATION (FT)

FOOTING ELEVATION (FT) STREAMBED ELEVATION (FT)

TOP BOTTOM CHA FIELD (2009)

SUBSTR.

UNIT

2) THE SUBSTRUCTURE LABELING CONVENTION ESTABLISHED BY CHA DEFINES LEFT AND RIGHT LOOKING DOWNSTREAM.

3) STREAMBED ELEVATIONS GIVEN ARE APPROXIMATE AT EACH SUBSTRUCTURE UNIT AND ALONG THE FASCIA INDICATED.

vFOR DETAILED SUBSTRUCTURE RIVERBED PROFILE MEASUREMENTS SEE ATTACHMENT I. ATTACHMENT H PROVIDES THE LOCATION OF

vSCOUR RELATED FEATURES AND OTHER MINOR STREAMBED VARIATIONS.

INVESTIGATION

DBRIDGE ELEVATION SUMMARY

NEW HAMPSHIRE BRIDGE SCOUR

ORIGINAL

DESIGN PLANS

CHA 100-YEAR SCOUR

ELEVATION (FT)

DATE: 5/10

114.8 (PILE CAP)

vUPSTREAM ELEVATIONv

LEFT ABUT.

PIER 1

PIER 2

PIER 3

RIGHT ABUT.

133.1

132.4

131.3

130.3

129.6

126.7

122.5

121.4

120.0

123.2

117.8

83.3

77.8

84.3

111.3

80.3

74.8

108.3 (PILE CAP)

HUDSON 109/068

LOW CHORD ELEVATION

(TYP)

N.T.S.


LARA

P1P2 P3

ROADWAY ELEVATION

(TYP)

STREAMBED ELEVATION

(TYP)

FOOTING ELEVATIONS

(TYP)

LEDGE

(TYP.)

2005 DIVING

N/A

N/A

N/A

67.0

N/A

N/A

N/A

N/A

N/A

N/A

N/A

79.8 (US)

69.8 (DS)

83.3 (US)

N/A

121.8

81.2

76.3

84.7

115.7

(FTG.)/70.3 (SEAL)

(FTG.)/60.8 (SEAL)

80.3 (FTG.)/71.3 (SEAL)

1) UNLESS OTHERWISE SPECIFIED, ALL ELEVATIONS ARE REFERENCED TO NAVD88. NAVD88 = DESIGN PLAN DATUM - 0.7 FT.

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ANNOTATION SCALE 200


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INVESTIGATION


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HUDSON 109/068

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BORING LOGS

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CHA File No:

18925.2003.1510

11 King Court

Keene, NH 03431-4648

Main: (603)-357-2445


Hudson 109/068 Attachment G: Scour Countermeasures

Attachment G:

Supporting Documentation, Calculations,

Estimates, and Conceptual Designs for Scour

Countermeasures

Interoffice Memorandum

To: Bill Horne

From: Phil Pierce

Date: May 25, 2010

Subject:

Discussion of Pile Foundation Scour for a 100-Year Event Bridge ID No.: Nashua-Hudson 109/068

CHA Project No. 18457.3600.1510

This memo addresses issues related to pile stability/capacity and CHA’s proposed Item 113 Rating.

Given:

Four-span bridge originally built in 1970 that has not been reconstructed.

Abutments are composed of concrete, founded on EB piles, and set back from the main channel.

Piers 1 & 2 are composed of concrete, located in the channel and founded on spread footings with concrete

foundation seals extending to bedrock per plans (14 ft & 10 ft thick min) – hence being of no concern from a

scour perspective.

Pier 3 is composed of concrete, founded on piles (30 feet), and located in the channel.

The latest NHDOT Underwater Inspection Report (2005) indicates footing exposure at Pier 3 of up to 1 foot,

leaving a remaining pile cap embedment of 12 feet.

Pier scour estimate calculations indicate the potential for 17 feet of scour at Pier 3 during a design year storm

event, which would expose approximately 5 feet of the pile foundation.

The bridge has apparently not been subject to any significant flooding since it was built, hence its scour resistance

is untested.

The design plans (1969) note slope protection at both abutments (stone fill, 6 ft thick). Existing conditions

contain stone protection on the slopes in good condition. No stone was shown on the plans for placement around the piers.

Evaluation/Conclusions: CHA has considered these conditions and concludes that a refined pile group analysis would probably indicate potential

instability of the pile group during design flood scour. Although a simplified evaluation of pile buckling strength indicates sufficient strength of an individual pile, it does not account for potential lateral displacement of the pile cap.

Further, the resistance of the superstructure to such lateral displacement of the pier caps cannot be easily estimated.

Recommendations: Given these conditions and conclusions, and considering an ADT of 35,000 (which is significant), and given the

Department’s expressed desire to avoid reliance on long-term monitoring of bridges as a POA response to potential scour, CHA

recommends installation of a physical scour countermeasure at Pier 3. Specifically, the use of A-Jacks would be appropriate due to the depth of water surrounding the pier.

Accordingly, CHA recommends that Item 113 be coded as 3 (scour critical) with the accompanying need for monitoring

during and after major events, until such time as this countermeasure is installed. Following successful installation, the rating could be changed to 7 to remove the bridge from scour critical status.

NHDOT PROTECTIVE COUNTERMEASURES 4/26/2010

ESTIMATED COST OF PROPOSED COUNTERMEASURES - A-Jacks:

109/068Hudson

60236 Over 10'52 17.5 A-Jacks width = 1.5 times pier width

unknown 35 A-Jacks Length is along its center17 A-Jacks area based on 1.5 times pier width is 5972 sq ft

alternatively, A-Jacks area based on ys = 17.0 width (3 sides) => 2066 sq ftuse A-Jacks based averaged area

SSU CM TYPE Length (ft) Width (ft) Depth (ft) No. Items Quantity Unit Unit Price Subtotal1 1 LS $30,000 $30,0001 1 LS $20,000 $20,000

198 21 1 466 SY $30 $13,990198 21 1 2687 EA $68 $181,373

1 1 LS $15,000 $15,000Proposed work: $15,000 - Only Minor streambed leveling required - Install A-Jacks [1 A-Jack covers 1.5624 SF) $275,362 - Water diversion is not necessary 25% $68,841

$344,203

$350,000

Assumptions:Environmental impact associated with the proposed work is judged to be: minorGiven the estimated quantities for this item, the unit price is judged to be equal to average unit prices.

Notes:The cost of mitigating or eliminating potential environmental impacts is not included in this estimate. The cost of environmental permit preparation is also not included herein.

Predicted scour depth, ys, ft

Conceptual Budget

Total Estimated Cost

Subtotal

Mobilization

Contingency

Note: use the size of the footing for this calculation - should be conservative, but one side was exposed during the last underwater inspection.

Site Prep

Item

Bridge Width Low Flow Water DepthMax. Vertical Opening Pier Width (ft)

Pier Length (ft)Remaining embedment

Bridge No. SSU's Protected Pier 3Town Spans Protected

Dist. Between Abutment Faces Approved Countermeasure Type A-Jacks N/A

Underwater placement support (Divers)A-Jacks (tied together)

Access to pier via bargebarge rental

A-Jacks Pier 3

6/23/2010 Attachment G

11 King Court, Keene, NH 03431-4648

Main: (603) 357-2445 www.chacompanies.com

DATE: 4/26/10

Drawn By: DC

ATTACHMENT GNEW HAMPSHIRE BRIDGE SCOURINVESTIGATION

HUDSON 109/068

CONCEPTUAL COUNTERMEASURE DRAWING

PLACARD INSTALLATION LOCATION

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ALL WORK IS TO BE PERFORMED IN DRY CONDITIONS

CONCEPTUAL ONLY

NOT FOR CONSTRUCTION

NOT TO SCALE

ATTACHMENT

GDATE: 05/10

INVESTIGATION


www.cloughharbour.comMain: (603) 357-2445


Drawing Copyright c 2009 CHA

HUDSON 109/068

RIGHTLEFT

PIER 3

LEFT

26.2 FT.

13.0 FT. 50-YEAR FLOOD

ELEVATION 109.5 FT.

NAVD88

(SEE NOTE)

PIER 1

RIGHTLEFT

25.2 FT.

10.5 FT. 50-YEAR FLOOD

ELEVATION 109.5 FT.

NAVD88

(SEE NOTE)

PIER 3

1) ELEVATION 109.5 CORRESPONDS TO A 50-YEAR FLOOD EVENT.

NOTES:

2) PLACARD LOCATION IS UPSTREAM NOSE OF PIERS 1 AND 3 ON BOTH SIDES.

3) PLACARD LOCATION IS MEASURED TO LOW CHORD AND TOP OF FOOTING.

NHDOT POST FLOOD INSPECTION REPORT (POA Attachment I)

Bridge: Post Flood Inspection Date:Hudson 109/068GENERAL INFORMATION

Town: Hudson


Owner: Municipality


Major Basin (HU8): Merrimack River

Functional Class: 14 - Urban Other Principal Arterial

Detour Length: 10 (miles)

Year Built: 1970

Year ofReconstruction: NA

ADT: 35005 Year of ADT: 2005

Overall Fed Sufficiency Rating: 63

RedList: No

Item 60: 7 Item 61: 6 Item 71: 9 Item 113: 3

Current:

HYDRAULIC INFORMATION

FEMA Study:

Whitman & Howard Information

USGS Report:

Tidal Influence: Other Hydrologic & Hydraulic Data:Hillsborough Countywide FIS (6-05) provides water surface elevation and flow data for bridge. FEMA datum is NAVD88. Merrimack River Watershed (Nashua River to Shawsheen River).

100-Yr Water Velocity (feet per sec): 6.2

Angle Of Attack 5

Watershed Area (sq. mi): 3982

(Flood Flow)

BRIDGE INFORMATIONBridge Length (in feet): 602.00 Plans Available: Borings Available:

Abutment Foundation: EB Piles Pier Foundation: EB Piles

2005 2006 2007

Flood / Scour HistoryComments:

Based on information included in the Hillsborough Countywide FIS (6-2004), the Merrimack River has not experienced a significant flood event since the bridge was constructed in 1970. According to the FEMA Independent Evaluation of Recent Flooding in New Hampshire (7-08), Merrimack River flooded near Manchester, NH in 2006 and 2007, with recurrence intervals of 10-50 years.

Flood History:

:

Bridge Width (in feet): 36.00

Substructure Channel Stability Hydraulic Adequacy Scour Risk

Posting 44.5 , E2

Bridge Plan File Loc: 3-14-2-1

(scale of 1-9)(worst - best)

100-Yr Overtopping Relief: No Overtopping

6/24/2004

Bridge Scour ReportNov 1992 :( )

RESULTS OF POST FLOOD INSPECTION

:(Actual Metric Tons, Signed)

Date of Interim Bridge Reopening:Date of Bridge Closure:

Date of Post Flood Inspection: Post Flood Inspection Completed By:

NA NA

Foundation Details:

KNOWN

UNKNOWN Worst Abutment: Left

Worst Pier: 3(Looking Downstream L to R)



Diving Insp Reports: 10/20/2005

Superstructure Type: Stringer/Multi-Beam or Girder

Superstructure Material: Steel

Scour Critical Feature: Pier 3


Red List: No

Number of Spans: 4

USGS Gage Station: USGS Station Prox To Bridge:

Dates:

What To Look For: Changes to the embedments at Piers. All piers have exposed footings. The footing and foundation seals are exposed at Pier 1 and 2 up to 3.5 and 8 feet, respectively. The remaining embedment is 9.5 feet for Pier 1 and 9 feet for Pier 2. The footing at Pier 3 is exposed up to 1 foot, leaving a remaining pile cap embedment of 12 feet.

NOAA Gage Station: NOAA Station Prox To Bridge:

Text9:6/23/2010 Text9:Attachment I: Post Flood Inspection Report: Hudson 109/068 Text9: Page 1 of 1

CHA File No:

18925.2003.1510

11 King Court

Keene, NH 03431-4648

Main: (603)-357-2445


Hudson 106/068 Attachment J: Scour/H&H Backup

Calculations

Attachment J: Scour/H&H Backup Calculations

COMPLETED BY DWC DATE

CHECKED BY KKD PROJ. NO.

PROJ. NAME & LOCATION Hudson 109/068 SUBJECT Scour Calcs

COMPLEX PIER SCOUR CALC

Q100 (cfs) 102000 FEMA Flood Study Q 100 FEMA Flood Study

Vavg (fps) 6.2 Average bridge opening velocity FEMA Flood Study, X-Sect C Floodway TableV1 (fps) 7.4 Velocity at pier (Vavg x Multiplier (1.2)) Multiplier varies from 0.9 to 1.7, see description below.*

Y1 (ft) at pier 29 113 - 84 (100-yr WSE - bed at Pier 3) WSE: FEMA Flood Study/ Bed: Dive Report θ (deg) 5 Angle of Attack Field Estimateh1 (ft) 1 85 - 84 (Top of footing - bed at Pier 3 nose) Bed: Dive Report / Pier: Design Plansa (ft) 4.5 Pier Width (average) Design Plans (From Town of Hudson)L (ft) 24.8 Pier Length (bottom) Design Plans (From Town of Hudson)f (ft) 2.6 Distance between the front edge of the pile cap/footing a Design Plans (From Town of Hudson)

apc (ft) 17.5 Widthof foundation seal/pile cap Design Plans (From Town of Hudson)Lpc (ft) 34.5 Length of foundation seal/pile cap Design Plans (From Town of Hudson)Topc (ft) 13 Thickness of footing + foundation seal (pile cap) Design Plans (From Town of Hudson)D95 (ft) 0.002 Sand bed Boring logs on Design Plans

9/7/2009

18457

VARIABLE CALC / NOTES SOURCE

95 ( ) g g gD50 (ft) 0.0006 Sand bed Boring logs on Design Plans

* Velocity multiplier varies from 0.9 for a pier near the bank in a straight uniform reach to 1.7 for a pier in the main current of flow on a sharp bend.Pier is in the channel along the inside of a gradual bend; use 1.2X multiplier.

1

K4: ARMORING COEFFICIENTCOMPLEX PIER SCOUR COMPUTATIONS CASE 2

Reference for methodology: HEC-18 Fourth EditionBridge 109/068 100-Year Event

Sand Bed K4: PIER COMPONENTPier #3

D95 (ft) = 0.0020D50 (ft) = 0.0006

COMPLEX PIERS SCOUR ANALYSIS V1: APPROACH VELOCITY (ft/s) = 7.44y: DEPTH (ft) = 29.00

Reference for methodology: HEC-18 4th Edition Chapter 6 a: PIER WIDTH (ft) = 4.50Ku = 11.17

PIER COMPONENT Yes Vc95: CRITICAL VELOCITY FOR D95 (ft/s) = 2.47Bent Number Pier #3 Vc50: CRITICAL VELOCITY FOR D50 (ft/s) = 1.65V1: VELOCITY (fps) 7.44 ViC95: INITIAL SCOUR VELOCITY FOR D95 (ft/s) = 1.06Y1: DEPTH (ft) 29 ViC50: INITIAL SCOUR VELOCITY FOR D50 (ft/s) = 0.66

ATTACK ANGLE, Degrees 5 VR: VELOCITY RATIO (ft/s) = 11.40h1: PIER STEM HEIGHT ABOVE BED (ft) 1.00 K4 = 1.00 Note: If D50 < 2mm or D95 < 20mm, then K4=1INDIVIDUAL PIER WIDTH (ft) 4.50a: PIER WIDTH (ft) 4.50 K4: FOOTING COMPONENTL: PIER LENGTH (ft) 24.80 Pier #3f: PIER SETBACK FROM EDGE OF PILE CAP (ft) 2.60 D95 (ft) = 0.0020PIER SHAPE (S=SQUARE, C = CIRCULAR, SN = SHARP NOSE) sn D50 (ft) = 0.0006K1: SHAPE COEFFICIENT 1.00 V1: APPROACH VELOCITY (ft/s) = 6.97K2: ANGLE COEFFICIENT 1.29 y: DEPTH (ft) = 30.95K3: BED COND. COEFFICIENT 1.10 a: CAP WIDTH (ft) = 17.50K4: BED AMORING COEFFICIENT 1.00 Ku = 11.17Khpier: WEIGHTING FACTOR FOR PIER SCOUR 0.29 Vc95: CRITICAL VELOCITY FOR D95 (ft/s) = 2.49g: gravitational constant (ft/s2) 32.20 Vc50: CRITICAL VELOCITY FOR D50 ft/s) = 1.67

FROUDE NUMBER, Fr 0.24 ViC95: INITIAL SCOUR VELOCITY FOR D95 (ft/s) = 0.99LOCAL SCOUR DEPTH (ft), Yspier 3.9 ViC50: INITIAL SCOUR VELOCITY FOR D50 (ft/s) = 0.62

VR: VELOCITY RATIO (ft/s) = 9.40FOOTING COMPONENT Yes K4 = 1.00 Note: If D50 < 2mm or D95 < 20mm, then K4=1Bent Number Pier #3V2: VELOCITY (fps) 6.97Y2: DEPTH (ft) 30.95ATTACK ANGLE, Degrees 5hopc: PRE-SCOUR PILE CAP BOTTOM HEIGHT ABOVE BED (ft) -12.00D50 (ft) 0.0006Ks (ft) 0.0009Ku critical velocity transport coefficient 11.17Vc critical transport velocity (fps) 1.67Yf: distance from bed to top of footing (ft) 2.95Vf : Average velocity in the flow zone above the top of footing (fps) 5.69apc: PILE CAP WIDTH (ft) 17.50Lpc: PILE CAP LENGTH (ft) 34.50Topc: PILE CAP THICKNESS (ft) 13.00CAP SHAPE (S=SQUARE, C = CIRCULAR, SN = SHARP NOSE) sY2max = 3.5*apc (ft) 61.25 See 6.18K1: SHAPE COEFFICIENT 1.10K2: ANGLE COEFFICIENT 1.11K3: BED COND. COEFFICIENT 1.10K4: BED AMORING COEFFICIENT 1.00Kw: WIDE PIER ADJUSTMENT FACTOR 1.00FROUDE NUMBER, Fr 0.22LOCAL SCOUR DEPTH (ft), Ysfc 13.1

TOTAL SCOUR DEPTH = Yspier + Ysfc 17.0

Calc. By: DWC Date: 9/7/2009Check By: KKD Date: 11/19/2009

5/25/2010 1 of 1 Attachment J

CHA File No:

18925.2003.1510

11 King Court

Keene, NH 03431-4648

Main: (603)-357-2445


Hudson 109/068 Attachment K: Underwater Inspection

Reports

Attachment K: Underwater Inspection Reports

priority scour critical bridge countermeasure plan of ...gis.dot.nh.gov/bridge_scour/hudson...

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