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Town of Mashpee Conservation Commission <br /> 16 Great Neck Road North <br /> Mashpee, MA 02649 <br /> NOI 0 Hollow Road / 0 South Sandwich Road (Besse Bog), Town of Mashpee. <br /> Proposed replacement of the undersized, buried culvert with a 9-foot-wide with a 5.17-foot-tall <br /> precast concrete box culvert. (Representative: Tighe&Bond) 43- <br /> 3430 <br /> Christopher Houle, P.E., Senior Project Manager with Tighe &Bond, appeared on behalf of the Mashpee Department of <br /> Public Works regarding the proposed culvert replacement and associated drainage improvements along Main Street at an <br /> unnamed intermittent stream near the Besse Bog Conservation Area. Mr. Houle was joined by Tighe&Bond <br /> representatives Catherine Rice, Corey Bracken and Nick Shaw and the Mashpee DPW Director. <br /> Mr. Houle explained that the Town's ongoing sewer infrastructure improvements along Main Street had increased the <br /> urgency of addressing drainage issues at the site. The existing culvert was estimated to be approximately 12 inches in <br /> diameter and was completely buried at both ends, with only small portions of the headwalls visible, and was not <br /> functioning as intended. The Town proposed replacing it with a precast concrete box culvert approximately nine feet <br /> wide by five feet two inches tall. <br /> The crossing was designed in general conformance with the Massachusetts River and Stream Crossing Standards to the <br /> maximum extent practicable, although Mr. Houle noted that the standards did not apply to the intermittent stream. The <br /> design nevertheless sought to improve aquatic and terrestrial organism passage and included two feet of embedment <br /> material within the box culvert and a reduction in overall culvert length. The proposed culvert would pass the five-year <br /> flow event with approximately 0.3 feet of freeboard and would not overtop the roadway through the 500-year storin <br /> event. <br /> Additional work included replacing the existing wooden sidewalk with a paved sidewalk,repaving within the project <br /> limits and relocating utilities as necessary. Stormwater improvements were also proposed. Mr. Houle explained that the <br /> site was at a low point in the roadway and that two existing drainage catch basins believed to be connected to leaching <br /> structures were unable to handle existing runoff, resulting in overtopping, erosion and gullies on both sides of the <br /> roadway. The proposed system would capture runoff, provide additional pretreatment and direct it to an underground <br /> infiltration system. <br /> The culvert replacement would be limited to the existing right-of-way, with limited clearing necessary for installation of <br /> the stormwater system within buffer-zone areas. The underground infiltration system was designed to manage the 10- <br /> year storm event without discharge and provide an estimated 75%reduction in peak flows for the 100-year storm event. <br /> The roadway was intended to be closed during culvert installation. Mr. Houle stated that the project was believed to <br /> qualify as a limited project under 310 CMR 10.53 under the maintenance provision and as redevelopment under the <br /> Stormwater Management Standards. There were no Natural Heritage concerns at the site. Because the project was within <br /> a Zone 11 area, a higher level of stormwater pretreatment was proposed. Resource areas included inland bank, bordering <br /> vegetated wetlands and land under water bodies and waterways. <br /> Mr. Colombo questioned the classification of the waterway as an intermittent stream given the significant drought <br /> conditions since November 2024 and asked how it had been determined that the stream was not perennial. Corey <br /> Bracken, Project Environmental Scientist with Tighe &Bond, explained that the stream did not appear on USG <br /> topographic maps or the 25K hydro layer and that site observations had not shown flowing water. He stated that wetland <br /> scientists had visited the site and that no records identified the stream as perennial. The waterway was described as <br /> intermittent water overflowing from Besse Bog and flowing south of the culvert. <br /> Mr. Houle added that he had walked the stream farther south and observed that it was largely a dug ditch,presumably <br /> associated with former cranberry farming, with mature trees growing from it and very dry conditions. After confirming <br /> 8 <br />