03/10/2004 ZONING BOARD OF APPEALS Minutes

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Southside Realty Trust Engineering Review Page six 3. The detail required to accurately set the grades at the proper stations and elevations needs to be shown on this sheet and how it ties to Route 130. 4. A waiver in the maximum allowable grade at Route 130 has been requested but there is not enough detail on the plans to show why this requirement cannot be met. With the degree of gradient shown on the plan, safety is of prime concern for the entrance. D. Construction Details 1. No construction details have been presented for the project such as typical road cross section, catch basins, manholes, pavement thickness, roadbase materials, water line details, sewer connections, riprap, or trenching. 2. In addition, there needs to be a detailed plan for each of the bioretention areas that have been proposed. The generic sketch presented in the drainage calculation document is not sufficient to show how each will be constructed. Also there needs to be a detail of how the forebay and riprap would be constructed at the infiltration basin shown on the "SWM° area. 3. The test logs included in the drainage calculations indicate that there is as much as 52" of sandy loam or loamy sand on top of the deep sand deposits. This upper material will prevent the rapid infiltration of stormwater runoff if it is not removed from the bioretention areas. Notes to this affect should be included on the plans. This material should also be removed from the roadbed areas to prevent frost heaves. IV. Further Comments A. There is a significant concern over the type of drainage design that is proposed for the site given the steep slopes and amount of impervious cover. No plan has been included to indicate how snow removal during winter months would be handled or how this might impact the proper removal of runoff from paved surfaces. B. The Mashpee Subdivision Rules and Regulations require catch basins to be installed at regular intervals and at street intersections to adequately capture runoff. There are several places within the project where these could be used with effect. C. It is recommended that an alternative method to bioretention be considered bearing in mind that water quality issues can be met by infiltrating the "first flush" of 1" of runoff. If bioretention continues to be the method of choice to meet the water quality standards, a method of implementing leaching pits below the infiltration areas could be considered and the areas designed such that frozen conditions will not impact the proper disposal of storm runoff. D. While it is understood that the project does not have to meet the rigid standards normally required for site plan approval, the development is intense enough to require a reasonably high level of detail to insure that the project can be constructed and will function as designed.