Hoyle Tanner prepared a hydrologic and hydraulic study for the replacement of a structurally deficient corrugated metal pipe (CMP) and reinforced concrete pipe.
The existing crossing is comprised of two adjacent culverts. The west culvert is a 4’ diameter reinforced concrete pipe and the east culvert is a 3’ diameter CMP. Due to its deteriorated condition and history of flooding in this area the Town of Derry is investigating replacement options for these culverts.
Hoyle Tanner performed hydrologic and hydraulic analysis and evaluated the existing opening of the culvert and recommended a new culvert type and opening that passes the 50-year flood event with a minimum of 1′ of freeboard per New Hampshire Department of Transportation (NHDOT) requirements. The recommended structure type will be 30’ in span. The project was fully funded through Town funds.
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Hydraulic Analysis
Study
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