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.
SERVICES
Hydraulic Analysis
Study
Final Design
Bid Process Administration
Construction Administration
From the blog
Learn about ongoing projects and the innovative processes we employ for our clients.
Meet Marko Salih – Southeast Aviation Intern & Avid New York Knicks fan What drew you to Hoyle Tanner? The opportunity to focus on airport engineering and design was...
For transportation agencies, successful project delivery extends well beyond developing plans and specifications. The most challenging risks often emerge after a project moves beyond concept development. Drainage conditions evolve....
Every quarter, we recognize employees who make an exceptional impact on our teams, projects, and culture. Meet our Q2 2026 Movers, Shakers & Innovators and see why their colleagues chose to honor their achievements.
Meet Bailey Jackson – HR Coordinator & Human-Centered Thinker What drew you to Hoyle Tanner? I was working part-time as an HR Assistant at a local community college, looking...
This month, we recognize the employees celebrating work anniversaries at Hoyle Tanner. Together, they represent 59 years of service to our company. We thank them for their dedication, hard work, and contributions to our team’s success.
Happy Parks and Recreation month! This month, we celebrate some cornerstones of our communities. When you think of public parks, maybe you think of Leslie Knope on the comedy...
After 40 years in the civil engineering, surveying, and consulting industries, Tim Bernier, LLS, PLS, CWS, is retiring from Hoyle Tanner as Principal Surveyor. Throughout his career, Tim has...
Meet Sarah Foy – Environmental Engineer & Wastewater Systems Advocate What drew you to Hoyle Tanner? The people! I worked in Matt Scarborough’s research lab in undergrad and heard...
Tyler Heinrich has achieved a major professional milestone by earning his Licensed Land Surveyor (LLS) credential. His accomplishment highlights years of dedication, expertise, and a passion for delivering high-quality surveying services to clients and communities across the region.
!["[At Hoyle Tanner] there is a strong encouragement to keep growing professionally, and no one hesitates to help when you have questions or are learning something new. That positive approach to development creates an environment where people feel comfortable challenging themselves and building new skills." - Marko Salih](https://hoyletanner.com/wp-content/uploads/2026/07/Featured-Images_Marko.jpg)
