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SC&MB - La Selva Beach Trestle

Photos 

Closeup of the Bridge

Detail of the deck and towers. Note the corroded members. The bucket / boom belongs to a J.L. Patterson inspection team.

Photo taken by Howard Cohen, 2012

Enlarge

View this photo at westcoastrailforums.com

BH Photo #281467

Map 

Street View 

Description 

NOTE: The original structure has been demolished. Stacy & Whitbeck has installed a modern analogue of the structure with the same overall design but modern construction techniques and mitigation.

Bridge is comprised of 9 deck girder spans of varying lengths, affixed to steel towers or bents. Three primary spans are mounted to towers, whereas the approach spans are affixed to the bents.

In 2012, a survey conducted by J.L. Patterson and associates on behalf of the the Santa Cruz County Regional Transit Commission [SCCRTC], which found the bridge structurally deficient, with "significant section loss with portions of columns having either 100% loss of member flanges or webs" and "the lateral and longitudinal bracing is for all intents and purposes non-existent in many of the towers". As such, the bridge is unfit for rail traffic, and the SCCRTC thusly decided the bridge will be reconstructed "from the footings up", and opted to install a bridge constructed by the firm Stacy & Witbeck.

As of August 2014 work on a replacement bridge has begun. All parts were fabricated offsite by S&W so therefore all that will be done on-site is assembly. Removal of the original bridge began in September, 2014 and installation of the replacement bridge's girder sections was complete by December 5th, 2014.

First post of the replacement project, over on West Coast Rail Forums: http://westcoastrailforums.com/thread-6953-post-86530.html#p...

Prepwork for new bridge begins, removal continues: http://westcoastrailforums.com/thread-6953-post-87168.html#p...

Facts 

Overview
Deck plate girder bridge over Leonard Gulch on The Santa Cruz & Monterey Bay Railroad (SC&MB)
Location
La Selva Beach, Santa Cruz County, California
Status
In Process of Demolition and Replacement
Future prospects
Original bridge is in poor condition, as per a 2012 inspection by the SCCRTC. It is currently being replaced, with an anticipated completion date of December, 2014.
History
Built 1927, Completely Replaced 2014
Builder
- Stacy & Witbeck
Railroads
- Iowa Pacific Holdings (IP)
- Santa Cruz & Monterey Bay Railway (SC&MB)
- Sierra Northern Railway (SERA)
- Southern Pacific Railroad (SP)
- Union Pacific Railroad (UP)
Design
Deck plate girder
Dimensions
Length of largest span: 70.0 ft.
Total length: 340.0 ft.
Deck width: 16.4 ft.
Also called
Leonard Gulch Trestle
Manresa Beach Trestle
Approximate latitude, longitude
+36.93727, -121.86603   (decimal degrees)
36°56'14" N, 121°51'58" W   (degrees°minutes'seconds")
Approximate UTM coordinates
10/600980/4088514 (zone/easting/northing)
Quadrangle map:
Watsonville West
Elevation
60 ft. above sea level
Inventory number
BH 60639 (Bridgehunter.com ID)

Update Log 

  • December 6, 2014: Updated by Alex Lewis: Replacement project is nearly complete. Updated accordingly.
  • October 26, 2014: Updated by Alex Lewis: Updated as per recent information on WCRF.
  • September 25, 2014: Updated by Alex Lewis: Another update to keep pace with construction.
  • September 19, 2014: Updated by Alex Lewis: Removal continues, changes noted.
  • September 11, 2014: Updated by Alex Lewis: Additional photos added
  • August 21, 2014: New Street View added by Ralph Demars
  • August 20, 2014: Updated by Alex Lewis: Construction began. Linking to relevant posts on WCRF.
  • April 11, 2014: Updated by Alex Lewis: Fixed a discrepancy in the number of spans, as per a SCCRTC document.
  • April 10, 2014: Updated by Alex Lewis: Added categories "Iowa Pacific Railroad", "Santa Cruz & Monterey Bay Railway"

Sources 

Comments 

SC&MB - La Selva Beach Trestle
Posted September 25, 2014, by Alex Lewis

In this case, it seems to be the width of the longitudinal bracing members initially, proximity to the marine environment, and the lack of paint. The 1st of Howard's photos show the bridge in 2012 and the bracing appears relatively intact, albeit unpainted and sporting a substantial amount of rust. Compared to the remainder of the members on the bridge, it's also pretty thin--more surface area to corrode once exposed, so the reaction occurs correctly.

As for paint and corrosion, points where the paint's chipped off could have provided an "entry" for oxidants, and it just works away from there if the initial point remains exposed.

I haven't cracked open a chemistry textbook in about a year and a half so I might be a bit rusty (no pun intended) myself on these principles.

SC&MB - La Selva Beach Trestle
Posted September 20, 2014, by K. A. Erickson

Is there any reason why some bracing would be worse off than others?

Because I have seen this before. The mid section of one bracing was corroded. And yet it sported a coat of nice green highway paint.