Technical Manual: Conduits through Embankment Dams (FEMA 484)

Conduits through Embankment DamsProject name: Lake Darling DamLocation: North DakotaSummary: Grouting voids existing outside an outlet works conduitLake Darling Dam is a zoned embankment dam built in 1935 on the Upper SourisRiver for the purpose of providing water supply for fish and wildlife habitat andproduction. The embankment dam has a structural height of about 40 feet, ahydraulic height of about 32 feet. The embankment dam holds 112,000 acre-feet ofwater at the maximum normal water surface elevation. The catchment basin abovethe embankment dam is over 9,000 square miles. The original outlet works consistedof twin (side-by-side) 10-foot by 14-foot cast-in-place, reinforced concrete conduitsplaced on alluvial foundation soils in the central embankment area. Two antiseepcollars were constructed around the exterior of the conduits at locations that roughlyalign with the upstream and downstream edges of the embankment dam crest.Figure B-43 shows the outlet works discharge at the downstream embankment toe.The discharge from the outlet filled a tailwater pool used for fish and wildlifepurposes. A small control structure on the downstream end of the tailwater poolprovided limited water surface elevation control capabilities. A cross section with aprofile of the outlet works and design cross section of the embankment dam isshown on figure B-44. Roller gates controlling releases from the reservoir arelocated immediately downstream of the intake structure near the upstream toe of theB-50Figure B-43.— Lake Darling Dam outlet works discharge, circa 1990.