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Culvert-assessment study helps town plan for investment, habitat preservation

Most of the culverts – structures that allow water to flow under roads, trails or other obstructions – in Cape Elizabeth are in pretty good shape.

Some, not so much.

A 2017-18 Culvert and Habitat Assessment Study, presented to the Town Council on April 8, 2019, identified three culverts in town that should be replaced within the next four years, based on their condition and importance to wildlife habitat.

View Culvert Study Presentation

The culvert in most critical need of replacement is at Willow Brook, about a half-mile south of Scott Dyer Road and a quarter mile east of Spurwink Avenue.

"Barely 200 feet away from this culvert is the Spurwink Marsh, (and) running across the top of the culvert are two sewer lines," Town Planner Maureen O'Meara told town councilors at their meeting April 8, 2019. Unlike most culverts, the structure is not under a road but it does direct water under a greenbelt trail, and was not considered a priority prior to the study. "The bottom of the culvert is deteriorated badly. We don't know what's going to happen to those sewer lines if these culverts completely fail, but it doesn't look good," she said.

O'Meara and Public Works Director Robert Malley presented slides and photographs from field assessments conducted in 2017-18.

The study, funded in part by a grant from the Maine Coastal Program, with help from the Wells National Estuarine Research Reserve, and examined the properties, condition and habitat impact of 16 culverts in town to help develop a plan for culvert replacement.

It's the first evaluation of town infrastructure to focus on culverts, O'Meara said, but, the habitat component is a highlight. "One of the best parts about this study was that we had a lot of technical assistance from habitat folks," she said, crediting especially Jake Aman from the Wells Estuary Reserve. Not only does the town now have an inventory and data on culvert habitat impacts, but has also developed partnerships with habitat organizations that can help analyze that data and help identify sources of funding.

Aman first approached the town in early 2017 with aerial photos of culverts near the Spurwink Marsh that showed signs of "scouring" – soil erosion caused by water trying to flow through a structure that is either too small or in bad shape.

Included in the study is an "at-a-glance" table summarizing the location, age, condition, habitat value and priority for replacement for each culvert.

"I think what we learned from this exercise that we needed to budget for these infrastructure replacements," said Malley, who participated in the field assessments and, with a panel of stakeholders from local and state government and conservation organizations, helped to identify which town culverts should be examined.

"I think some times we take our infrastructure for granted, everything's flowing underneath the road as we drive over it." Malley said. But, "it was a good exercise to climb down and measure these culverts and to see them. Some were fine and some were not so fine, so it was a productive exercise and I'm glad we did it."

Of the 16 culverts, six were singled out for hydraulic analysis, conceptual improvement designs and preliminary cost estimates. The Willow Brook culvert and a culvert at Mitchell Road and Pond Cove Brook, both identified as high priorities for replacement, would cost $275,000 and $315,000 respectively. Two others identified for replacement in the next 5-10 years were at Trout Brook and Ocean House Road ($320,000); and Trout Brook at Spurwink Avenue ($270,000).

"So you can see that we're looking at the first 1-4 years at about $600,000 investment in culverts, and then the next 5-10 years probably another $600,000 investment in culverts," O'Meara said.

The proposed 2019-20 municipal budget includes $65,000 for planning and engineering to replace the Willow Brook culvert. Some culverts will compete well for grant funding because of their habitat impacts, O'Meara said. "In those situations we're probably still going to have to come up with 50 percent of the match," she said. "In other places we may not compete very well and the culvert replacement is really going to be coming out of the town's capital improvement budget." Town staff, with the help of the priorities set in the culvert study, will recommend grant opportunities as they come up as well as recommendations for avoiding emergency situations.

The problematic culvert at Sawyer Road at the Scarborough border, "overtopped multiple times a year with flooding," O'Meara said, was part of the study but is under a separate hydraulic analysis because of its tidal influences. The Maine Coastal Program is also helping with that study, in conjunction with the town of Scarborough. [news article]

The council on April 8 voted to accept the Culvert and Habitat Assessment Study with thanks.