The Lowell Conservation Commission on Oct. 22 continued a request for determination of applicability (RDA) for work at 36 Shirley Avenue, saying the applicant must confirm the base flood elevation and provide engineering or survey details before the commission can approve an addition proposed inside the FEMA 100-year floodplain.

The item was filed by contractor and resident Keith Soar of 15 Leverett Street, who told the commission he seeks a small kitchen expansion and described the proposed work as a shallow addition supported on a single pier. “My plan was to call just 1 foot, and we have no foundation veil, anything, and it's just 1 pier, and that's all,” Soar said.

Commission members said the filing lacked the information required to evaluate floodplain impacts, including the base flood elevation and a grading or topographic plan showing compensatory flood storage. “Typically, we recommend that this goes to engineering for design,” a commission member said, explaining that any new structure in the floodplain can displace water and that the displaced volume must be compensated elsewhere on the site at the same elevations.

Commission staff noted that confirmation of the relationship between the existing structure and the base flood elevation is the minimum information needed to determine whether the proposed single pier is a de minimis addition. Soar told the commission the bottom of the framing would be about 2½ to 3 feet above ground; commissioners said that alone does not establish where the base flood elevation lies relative to the structure.

Next steps: the commission continued the RDA to its Nov. 12 meeting to allow the applicant to provide the base flood elevation and any engineering or survey documentation. A motion to continue to the Nov. 12 meeting was made by a commission member and seconded; the commission voted unanimously to continue.

The commission recommended that Soar consult a civil engineer or surveyor; staff also noted the city engineer's database includes catch basin and manhole elevations that may help determine the flood line. Soar said he would contact his surveyor the following day and follow up with the commission office.