12.07.2015 Views

Technical Manual: Conduits through Embankment Dams (FEMA 484)

Technical Manual: Conduits through Embankment Dams (FEMA 484)

Technical Manual: Conduits through Embankment Dams (FEMA 484)

SHOW MORE
SHOW LESS
  • No tags were found...

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Appendix B—Case HistoriesProject name: Rolling Green Community Lake DamLocation: MarylandSummary: Sliplining of an existing spillway conduit using Snap-Tite® HDPERolling Green Community Lake Dam failed in February 1999. Constructed in 1965,the 22-foot high, low hazard embankment dam contained a 24-inch diameter CMPspillway. The spillway riser had been gradually deteriorating, and the owner hadattempted repairs at the top of the riser by use of a larger CMP sleeve and concretegrout. However, no repairs to the lower portion of the riser were attempted, and thebase of the riser collapsed on February 6, 1999. A large portion of the embankmentdam was washed away, leaving a void about 30 feet in diameter and 10 feet deeparound the original riser location (figure B-67).A CCTV inspection of the barrel portion of the CMP revealed that the remainingsections of pipe were in good condition. The engineer elected to slipline the existing24-inch diameter barrel with 20-inch (outside diameter) Snap-Tite® pipe (SDR 32.5).The space between the two pipes was filled with a grout composed of fly ash andcement (compressive strength 2,500 lb/in 2 ), and a new aluminum riser wasconstructed within the upstream portion of the embankment dam.Figure B-67.—When the 35-year old corrugated metal pipe riser collapsed,a large portion of the low hazard embankment dam was washed away.This left a void about 30 feet in diameter and 10 feet deep around theoriginal riser.B-87

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!