The Needham Conservation Commission voted unanimously Sept. 25 to close the hearing and issue an order of conditions for proposed terrace retaining walls in the backyard of 109 Heather Lane (DEP file 234-953).

The project, presented by Brandon Lee of Kelly Engineering and applicant Bill Piersack, would install a two-step segmental block retaining wall system to terrace a steep backyard slope. Lee said the terrace steps with two walls, the highest point about 12 feet, and that the design uses segmental block with tiebacks, stone drainage behind the walls and an outlet pipe. He said the additional impervious area within the 100-foot buffer zone would be 176 square feet and that the closest work to the bordering vegetative wetland (BVW) would be about 55 feet.

Commission staff recommended enhanced erosion controls and replacement plantings after a site review. Deborah Anderson, Needham director of conservation, and Timothy Puopolo, Needham conservation specialist, told the commission they had observed two trees removed in the area previously and worked with the applicant to propose four eastern redbud replacements. Anderson recommended a combination of silt sock and silt fence given the steep slope and specified erosion-control details including 12-inch-diameter stakes for installations and requirements for a pre-construction site meeting.

Commission discussion focused on construction technique, public-safety fencing and permits. Commissioner Fred asked about wall construction and whether the wall would be engineered; Lee and Piersack said walls over 4 feet require an engineered design and that the final engineering plans would be provided by the segmental block supplier. Chair Dave Harrer and other commissioners clarified that the terraced design left a 4-foot wall at the property line so that local building-permit requirements for single 4-foot walls would not be exceeded at that line.

The commission included conditions in the order of conditions requiring the proposed erosion controls, pre-construction inspection, and the four replacement eastern redbuds in the location shown on the plan. The commission did not require two-year monitoring of the plantings, stating staff had judged the planting spots suitable. The commission recorded a roll-call vote to close the hearing and later a separate roll-call vote to issue the order of conditions; both votes were recorded as unanimous.

Actions taken: the commission voted to close the hearing for 109 Heather Lane, DEP file 234-953, and voted to issue an order of conditions with the erosion-control and planting conditions noted above. Commissioners voting aye included Commissioner Sue, Commissioner Bill, Commissioner Fred, Commissioner Reid and Chair Dave Harrer.

The applicant, Bill Piersack, confirmed he will pick up permits from the building department once the commission's requirements are satisfied.