Loch Alsh Reservoir Dam Rehabilitation

Ambler Borough retained G&A for the remediation of the Loch Alsh Reservoir Dam, located on Stuart Farm Creek in Upper Dublin Township.  The 300 foot long masonry gravity dam was constructed for a water supply reservoir in the early 1900’s.  The 16 foot high structure has a normal pool storage capacity of 53 acre-feet.  PADEP classified Loch Alsh as a high hazard structure since its failure would inundate downstream residential areas. Inadequate spillway capacity, seepage through the dam, and scour along its toe and abutments warranted its rehabilitation.

G&A provided planning, design, permitting, and construction administration for this critical project.  The spillway was improved to convey 100% of the Probable Maximum Flood (PMF) event.  An Articulated Concrete Block (ACB) system was used to protect the embankment from scour during overtopping events, and new parapet walls will prevent flood waters from scouring the dam  abutments and protect downstream areas during overflow conditions.


Borough of Ambler

Ambler, PA

Market Segment



Alexander Dyke, P.E.
Executive Vice President

Trevor Woodward, P.G.
Geotechnical Services Manager