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Home My WebLink About07/11/2018 - 2nd HWG Stormwater Peer Review - - 1429 OSGOOD STREET f Horsley Wi ittle n G ro u�p, Sustainable Ehvironmental Solutions Ali%„ lil° 294,Washington street-Spite 801 -Boston, A 02108 July 11, 2018 Ms. Monica Gregoire, Staff Planner Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Ref: Mixed-Use Development 1429 Osgood Street, North Andover, MA Dear Ms. Gregoire 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 review of the Site Plan and Drainage Report for the proposed mixed-use redevelopment at 1429 Osgood Street, North Andover, MA. The plans were prepared for Oliver Enterprises, Inc. (Applicant) by Allen & Major Associates, Inc. We understand that the project involves retaining the existing structure while reconfiguring the onsite parking lot, including the installation of new sidewalks, utility improvements, and stormwater management on a 1.96±acre parcel. The proposed work is within the 200 foot Riverfront Area of an unnamed stream and within the 25-foot buffer of the adjacent bordering vegetated wetlands (BVW). The following documents and plans were received by HW: • Response letter in reference to HW comments, prepared by Allen & Major Associates, Inc., dated July 5, 2018; • Drainage Report, 1429 Osgood Street, North Andover, prepared by Allen & Major Associates, Inc., revised July 5, 2018; and • Corridor Development District Plan for Mixed-Use Development, 1429 Osgood Street, North Andover, MA, prepared by Allen & Major Associates, Inc. revised July 5, 2018, which includes: o Cover Sheet o Abbreviations & Notes C-001 o Abbreviations & Notes C-002 o Existing Conditions Plan V-101 o Site Preparation Plan C-101 o Layout and Materials Plan C-102 o Grading and Drainage Plan C-103 o Utilities Plan C-104 o Turning Movement 1 C-105 o Turning Movement 2 C-106 o Landscape Plan L-101 o Landscape Plan L-102 o Landscape Plan L-103 o Details C-501 o Details C-502 Hors[ey%tten.corn 91 @HorsleyWittenGroupHorsley -tenrcu , I nc. Town of North Andover July 11, 2018 Page 2of6 Stormwater Management Design Peer Review The following numbered comments correlate to the HW May 2, 2018 initial peer review letter. Additional comments are provided in bold font. 1. Standard 1 states that no new stormwater conveyances may cause erosion in wetlands of the Commonwealth. a. The existing site currently sheet flows in three directions: • West from the Project site into an existing catch basin that appears to be associated with the drainage system in Osgood Street, also known as Rte 125, a Massachusetts State Highway; • Northwest towards an existing low point at the property boundary; and • Southwest towards the unnamed stream and BVW delineated at the edge of the existing parking lot. The Applicant is intending to maintain these three discharge points and has proposed best management practices (BMPs)to provide additional treatment. To verify that the proposed grass swale located along the southwest property line will not cause erosion at the existing headwall HW recommends that the Applicant provide the velocity calculations for the grass swale. The Applicant has adequately responded to this comment and has provided velocity calculations in Section 6.0 of the Drainage Report. The calculations indicate that the velocity within the grass swale will be less than 2.0 feet per second (fps); therefore, erosion should not be a concern. The Applicant appears to be complying with Standard 1. 2. Standard 2 requires that post-development runoff does not exceed pre-development runoff off-site, for a redevelopment project per MassDEP this standard must be met to the maximum extent practicable. The Applicant has reduced impervious cover to all three discharge points and the HydroCAD modeling calculations provided indicate that the post-development peak discharge rates do not exceed the pre-development discharge rates. The proposed HydroCAD model does not include the proposed BMPs, including the rain gardens and grass swales proposed for water quality treatment. This is a reasonable methodology to verify compliance with Standard 2. HW has the following comments regarding the HydroCAD model: a. The Existing and Proposed Watershed Plans indicate that the existing building has specific breaks in the roof runoff. HW recommends that the Applicant provide a narrative explaining how the roof divide was determined. The Applicant has adequately responded to this comment. The Applicant has provided a narrative explaining how the roof divide was determined in the Response letter, dated July 5, 2018. b. In accordance with Section 7.2 B. b) of the Stormwater Regulations, the Applicant has provided the analysis for the 2-, 10-, 25-, and 100-year storm events and has utilized the 24- hour rainfall amounts as required per the Town of North Andover. No further comment needed. c. Furthermore, in accordance with Section 7.2 B. b) of the Stormwater Regulations the Applicant should provide the analyses for the 1/2-inch storm. HW recommends that the Applicant provide these additional calculations. IV,, p ��I �`� gol 6 �� m W I IIdI'" W';ir' �� M,� � �I�mail.�..�� w � an� �� ...� ��.:� � .. r.„ ...� �� . ��.m. IIL�.. III III.... ,�ul � „an „I� .., r...., ...�. .. . Town of North Andover July 11, 2018 Page 3of6 The Applicant has adequately responded to this comment. Analyses for the /2-inch storm have been provided. The Applicant appears to be complying with Standard 2. 3. Standard 3 requires that the annual recharge from post-development shall approximate annual recharge from pre-development conditions. a. In accordance with the MassDEP Standards the Applicant is required to meet Standard 3 to the maximum extent practicable. By reducing impervious area the Applicant believes it has met this Standard. No further comment needed. b. In accordance with Section 7.2 C. d) of the Stormwater Regulations the Planning Board may alter or eliminate the recharge volume requirement if the site is in an urban redevelopment area. The Applicant has provided soil test pits noting that the estimated seasonal high ground water(ESHGW) prevents it from providing infiltration; however the Applicant has provided non-structural practices including filter strips and grass channels as required in the Stormwater Regulations. No further comment needed. c. It appears that the Applicant is in compliance with Standard 3. No further comment needed. The Applicant appears to be complying with Standard 3. 4. Standard 4 requires that the stormwater system be designed to remove 80% Total Suspended Solids (TSS) and to treat 0.5-inch of volume from the impervious area for water quality. a. The Applicant has utilized rain gardens with pea stone diaphragms for pretreatment to provide the 80% TSS removal. No further comment needed. b. In accordance with Section 7.2 D. b) and c)of the Stormwater Regulations the Applicant should provide the water quality volume for the 1/2-inch storm, however it appears that the Applicant has not provided sizing calculations for the rain gardens or provided the 1/2-inch storm analysis. HW recommends that the Applicant provided the sizing calculations for the rain gardens in accordance with Volume 2, Chapter 2, page 26 of the MSH. The Applicant has adequately responded to this comment and has provided the sizing calculations for the rain gardens. The calculations show that the proposed rain gardens do not meet the MSH sizing criteria of 5%to 7% of the area draining to it. The Applicant has stated that it has sized the proposed rain gardens as large as practicable. c. HW recommends that the Applicant provide a detail for the pea stone diaphragm. The Applicant has adequately responded to this comment. The Applicant is complying with the structural stormwater best management practice (BMP) of Standard 4 to the maximum extent practicable. They are improving existing conditions by removing impervious cover and providing various BMPs to improve water quality prior to discharging into the adjacent wetland resource areas. The long- term operation and maintenance of the proposed BMPs will be critical for maintaining the functionality of the stormwater system. .. ), � ". � � .. m . �. 14,111 " - , m„. . Town of North Andover July 11, 2018 Page 4of6 The Applicant appears to be complying with Standard 4. 5. Standard 5 is related to projects with a Land Use of Higher Potential Pollutant Loads (LUHPPL). a. The Applicant has noted that the proposed land use is not considered a LUHPPL; however the Layout& Materials Plan indicates that open storage bins are proposed. HW recommends that the Applicant clarify the proposed use of the property as well as document what material will be placed in the storage bins. The Applicant has provided a narrative clarifying the proposed use of the property in its July 5, 2018 Response letter. The Applicant is proposing to store exterior material in the bins including crushed stone, gravel, granite block, precast concrete curbing, and/or loam and has relocated the bins further from the wetland resource areas. The Applicant should be aware that the storage bins should not contain chemical fertilizers, manure, or road de-icing materials. The Conservation Commission may choose to limit the types of materials stored on the property. Standard 5 is not applicable to the proposed use. 6. Standard 6 is related to projects with stormwater discharging into a critical area, a Zone 11 or an Interim Wellhead Protection Area of a public water supply. a. Standard 6 is not applicable to this site. No further comment needed. 7. Standard 7 is related to projects considered Redevelopment. a. In accordance with Section 7.2 E of the Stormwater Regulations and Volume 1, Chapter 1, page 2, of the MSH a redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural best management practice requirements of Standards 4, 5, and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. The Applicant has designed the project to meet the MassDEP Standards to the maximum extent practicable and has improved existing conditions by reducing impervious cover and installing rain gardens for water quality treatment. As noted previously HW recommends that the Applicant provide sizing calculations for the rain gardens. The Applicant has provided sizing calculations for the rain gardens. The Applicant appears to be complying with Standard 7. 8. Standard 8 requires a plan to control construction related impacts including erosion, sedimentation or other pollutant sources. a. The Applicant has included a Site Preparation Plan and Erosion and Sediment Control Notes in accordance with Standard 8. The Applicant has noted on page 1-7 of the Drainage Report that the Stormwater Pollution Prevention Plan (SWPPP)will be prepared and submitted prior to construction. The Conservation Commission may choose to include a Special Condition requiring the SWPPP to be provided to the Commission at least 14 days prior to any land disturbance. b. In accordance with Section 8.0 of the Stormwater Regulations, if a SWPPP is required per the NPDES General Permit the Applicant is required to submit a complete copy of the SWPPP as part of its application for a Land Disturbance Permit. HW recommends that the �, i I,IV, p � h! .. sii a 2 I,.131- 6, � m� I W I II ,Ir, I��. '.�......��.�.I ..,...�� M. � �I�m.�ii.��I � � m.�. I� ��. � �� .... ��.��r��...�� IIL�,..�"III III ,�iu � ��I� Town of North Andover July 11, 2018 Page 5 of 6 Applicant provide the SWPPP to the Town for review and verify that the Erosion and Sediment Control Criteria listed under Section 8.2 of the Stormwater Regulations is clearly referenced. HW recommends that the Applicant provide the SWPPP to the Town for review. c. HW recommends that the size of the Fiber Roll be added to Detail 7 on Sheet C-501. Furthermore HW recommends that the size of the siltation fence be added to the detail. The Applicant has adequately responded to this comment and has added the size of the Fiber Roll to Detail 7 on Sheet C-501. The Applicant appears to be complying with Standard 8. 9. Standard 9 requires a Long Term Operation and Maintenance (O & M) Plan to be provided. a. The Applicant has included an O&M Plan in accordance with Standard 9. HW recommends that the Applicant provide additional information related to the maintenance of the grass swale and pea stone diaphragm. Furthermore the Applicant may choose to separate the narrative for the bioretention area and the grass channel so that the plants in the rain gardens are not mowed. The Applicant has adequately responded to this comment. Additional information regarding the maintenance of the grass swale and pea stone diaphragm has been provided. The Applicant appears to be complying with Standard 9. 10. Standard 10 requires an Illicit Discharge Compliance Statement to be provided. a. The Applicant has stated that an illicit discharge statement signed by the property owner will be provided prior to the discharge of any stormwater. The Conservation Commission may choose to include a Special Condition requiring the Applicant to provide the signed illicit discharge statement prior to construction. 11. 25 foot No Disturb Zone a. The Applicant is proposing the removal of asphalt along the southwest property boundary. The removal of impervious cover is strongly encouraged, however a portion of this asphalt is on the abutting parcel; permission from the property owner will be required as well as an Order of Conditions from the Conservation Commission. HW recommends the Applicant obtain permission from the property owner to work on the adjacent property and that the work is included in the Order of Conditions issued by the Conservation Commission. 12. Low Impact Development a. The Applicant has proposed reducing impervious cover, installing rain gardens and a grass channel. The proposed stormwater practices are considered low impact development in accordance with the MSH. No further comment needed. 13. Miscellaneous Comments: a. The proposed plan set including the Layout& Materials Plan, the Grading & Drainage Plan, and the Utilities Plan illustrate subsurface trenches in the area of the existing catch basin and Bioretention Area#2. It is not clear what these trenches are. HW recommends that the Applicant clarify the purpose of these trenches. lI p o lh it 6 � d�m r III III III ��.II_I :�_ Town of North Andover July 11, 2018 Page 6of6 The Applicant has clarified the purpose of the trenches in the July 5, 2018 Response letter. The primary and reserve trenches for the septic system are relocated and shown on the Layout& Materials Plan (Sheet C-102). b. As noted previously Osgood Street is a state highway and the Applicant is discharging stormwater into the state drainage system. HW recommends that the Applicant document to the Planning Board that permission to continue to discharge into the Massachusetts Department of Transportation (MassDOT) drainage network will be received prior to construction. The Applicant is reducing the flow to this catch basin as well as providing water quality as will be required by MassDOT. The Conservation Commission may choose to include a Special Condition requiring the Applicant to provide this documentation prior to any land disturbance. Conclusions HW is satisfied that the Applicant has adequately responded to our previous 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 857-263-8193 or at jbernardo@horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. a ' " fgfl �rlaN', ' ,,,,,w^„,'�➢ �fw...1�"' a,, ,;,.'prro',�iw"+wwm`,.,,,.. u; a,w' "° �" ...� .,,�r.,:' Josephine Ibanez Janet Carter Bernardo, P.E. Environmental Scientist Senior Project Manager .,,. 4i ';mini '...III- no„w .. 'i�� i, i'...III ..,,III,. ,. V-, i��r:i� ,,....,:; &9 ^i A IV,w p tl, q/ �� h .i "' � m m'il m 'tl W r ;. .ar.... 1 1 T mil... � � n a �z0" 1 � � �. ��.m. IIL III III