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HomeMy WebLinkAbout2021/08/13 - 2nd Stormwater Peer Review - 325 Johnson Street %�. Horsley Wiften Group 0 SUStainable, Ehvirownental Solutions 112 W'at r `tr t-61 Floor-Boston,MBA 02109 .......... 5 -2 1 ho,r 1 ten August 13, 2021 Ms. Jean Enright, Planning Director Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Ref: 2nd Stormwater Peer Review 325 Johnson Street North Andover, Massachusetts Dear Ms. Enright and Board Members: The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board with this letter report summarizing our second peer review of the Special Permit- Watershed Permit Application and Plan presented to the North Andover Planning Board for the proposed garage at 325 Johnson Street, North Andover, MA. The plans were prepared for Kevin &Alison Sparks (Applicant) by Sullivan Engineering Group, LLC. HW understands that the Applicant is proposing to construct a 720 square foot (sf) garage and small expansion to the existing gravel driveway. The entire parcel is located within the Watershed Protection District of Lake Cochichewick. The existing house, existing gravel driveway and proposed garage are located within the 100-foot buffer zone of a wetland resource area. The Applicant is proposing to disconnect the on-site wastewater cesspool and connect into the municipal sanitary system as part of the proposed project. The Applicant intends to manage the roof runoff from the proposed garage with a 1,000-gallon subsurface drywell. HW has received the following additional documents in response to our initial review: • HydroCAD model for 1,000 gallon drywell, dated August 9, 2021 (13 pages). • Plot Plan of Land, 325 Johnson Street, North Andover, Massachusetts, prepared by Sullivan Engineering Group, LLC, revised August 9, 2021 (1 Sheet). Stormwater Management Design Peer Review HW offers the following comments concerning the Special Permit Application and the stormwater management design. The comments below correlate to our initial review dated June 8, 2021. Follow up comments are provided in bold font. 1. The property is located within the R3 Zoning District and the lot was created in 1989. In accordance with the Watershed Protection District regulations, for lots created prior to October 24, 1994, a 100-foot non-disturbance zone is applicable as well as a 325-foot non-discharge zone. In accordance with Section 195-4.19 A. (4): Town of North Andover August 13, 2021 Page 2 of 4 Building requirements. All construction in the Watershed Protection District shall comply with best management practices for erosion, siltation, and stormwater control in order to preserve the purity of the groundwater and the lake; to maintain the groundwater table; and to maintain the filtration and purification functions of the land. The Applicant has proposed a 12-inch diameter staked mulch soxx along the edge of the existing gravel driveway closest to the wetland resource area as well as around the limit of work associated with the proposed garage. a. HW recommends that the Applicant consider extending the erosion control barrier to allow construction equipment access to the rear of the house to install the concrete pads for the heat pump and the generator. The erosion control barrier has been adjusted as suggested. No further comment. b. HW recommends that the Applicant include a detail for the proposed erosion control barrier. The Applicant has provided a detail of a 12-inch mulch soxx. HW has no further comment. c. HW recommends that the Applicant clarify the type of equipment that will be used to install the 6-inch PVC sewer service as well as the proposed gas service that are located outside of the erosion control barrier. The Planning Board may choose to condition the type of equipment that will be used to install the utilities within the wooded area of the property. HW notes that a portion of the proposed service connections are outside of the 100-foot non-disturbance zone. The Applicant has noted on the Plot Plan that a mini-excavator& a skid steer will be used to install the sewer and gas services. This type of equipment is reasonable. HW has no further comment. d. HW recommends that the Applicant clarify the extent of the limit of work to include the service connections and clearly document how the trees to be removed will be noted in the field to avoid any miscommunication and removal of trees proposed to remain. The Applicant has added a note on the plan stating that a colored ribbon will be tied around each tree proposed for removal prior to any work onsite. HW has no further comment. 2. The Applicant has applied for a Special Permit for work within the 100-foot Non- Disturbance Buffer, in accordance with Section 195-4.19 C. (2): (a). Any activities which cause a change in topography or grade. The Applicant is proposing some minor changes to the grades in the vicinity of the proposed garage. (b). Vegetation removal or cutting, other than in connection with agricultural uses or maintenance of a landscape area. KµTm w 1\�',21 20 w l 'Aorth 1..... M 32 5, Johnson Stl.i .tl,\ ork\2 6 t'ICI Pc�er R.1.11" 11 IAT ..15,IAw , Town of North Andover August 13, 2021 Page 3 of 4 The Applicant is proposing to cut 9 trees between 6-inches and 20-inches in diameter to clear the area of the proposed garage as well as the extension of the gravel driveway. (e). Any surface or subsurface discharge, including, but not limited to, stormwater runoff; drainage of any roadway that is maintained by the Division of Public Works or any private association; outlets of all drainage swales; outlets of all detention ponds. The Applicant is proposing to install a drywell for subsurface discharge of stormwater runoff. (g). Construction of any accessory structure or expansion of any existing structure by less than 50% of the gross floor area if the existing primary structure is less than 2,500 square feet and the primary structure will be connected to municipal sewer upon completion of the project. The existing house is listed in the Application as being 2,034 sf. The garage is proposed to be 720 sf. The Applicant is proposing to decommission the existing cesspool and install a 6-inch sewer service from the existing house to Johnson Street. No further comment required. 3. In accordance with Section 195-4.19 C. (3) the following applicable uses are prohibited within the Non-Disturbance Zone: (d). The use of, or method of application of, any lawn care or garden product (fertilizer, pesticide, herbicide) that may contribute to the degradation of the public water supply. The Applicant has stated that no pesticides, fungicides, chemicals, or non- organic fertilizers will be used in lawn care or maintenance. (e). The use of lawn care or garden products that are not organic or slow-release nitrogen. The Applicant has stated that no pesticides, fungicides, chemicals, or non- organic fertilizers will be used in lawn care or maintenance. a. The Planning Board may choose to include as a condition of approval that the Applicant is prohibited from using any pesticides, fungicides, chemicals, or non- organic fertilizers on the property. No further comment required. HW's suggestion for a Condition of Approval stands. 4. In accordance with Section 195-4.20 G: Within the Non-Disturbance Zone and Non-Discharge Buffer Zone, any runoff from impervious surfaces shall, to the extent possible, be recharged on site and diverted toward areas covered with vegetation for surface infiltration. Where on- site recharge is not feasible due to soil or other natural conditions, other mitigating measures such as sedimentation ponds, filter berms, or restoring �i__ � � ��� " � ���1�°M i. _� w w� � �. �. �2 � � �� M ,1). &doc 11� Town of North Andover August 13, 2021 Page 4 of 4 wetlands shall be used only where other methods are not feasible and after approval by the Board of Health, Building Inspector and the Division of Public Works to assure that the methods used for on-site infiltration and/or other measures shall remain effective. The Applicant has proposed a 1,000-gallon drywell to infiltrate the roof runoff from the proposed garage. HW has the following comments associated with the drywell design: a. The Applicant has noted that the drywell has been sized to handle the 100-year rain event. However, it appears from the HydroCAD model that the peak elevation within the drywell during the 100-year event is 256.99, which is above the interior drywell elevation of 256.8. The drywell is proposed to be set at elevation 254.3 and has an internal height of 2.5 feet. HW recommends that the Applicant adjust the design slightly to reduce the peak elevation. The Applicant has adjusted the design slightly to retain the 100-year storm event in the drywell as required. HW has no further comment. Conclusions HW is satisfied that the Applicant has adequately addressed our comments. The Applicant is advised that provision of these comments does not relieve him/her of the responsibility to comply with all Town of North Andover Codes and By-Laws, Commonwealth of Massachusetts laws, and federal regulations as applicable to this project. Please contact Janet Bernardo at 508-833-6600 or at jbernardo@horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. r °duu'4d'""h; Janet Carter Bernardo, P.E. Associate Principal CC: Conservation Commission \ w.j �[s\2(.)2 1\2 1 w l A th -\ 1L . B 325 Johnson. ��.� ��.tl.� � � _\ ...,.5 Johriison.