The URL can be used to link to this page

Home My WebLink About09/21/2020 - HWG Stomwater Peer Review - - %�. 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 September 21, 2020 Ms. Jean Enright, Planning Director Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Ref: Follow up Stormwater Peer Review Modifications to Previously Approved Plans 1600 Osgood 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 follow up peer review of the modifications to the Stormwater Management Report and Permitting Plans presented to the North Andover Planning Board for the proposed redevelopment of 1600 Osgood Street, North Andover, MA. The plans were prepared for Hillwood Enterprises, L.P. (Applicant) by Langan Engineering & Environmental Services, Inc. HW understands that the Applicant is proposing to redevelop a 167.8-acre site and will reconfigure the parcel into two lots (A and B). Lot A consists of approximately 58 acres, and includes two existing buildings, 1,500 parking spaces, and a relocated solar field. Lot B consists of approximately 110 acres and is proposed to be redeveloped into an e-commerce warehouse, storage, and distribution facility along with parking, landscaping, and other improvements. The Applicant is requesting a modification to the Special Permit because of changes in plans due to comments received from MassDOT regarding the entrance onto Osgood Street, Massachusetts Highway Route 125. The previously approved layout and stormwater management design has been modified because of the driveway access road alterations as well as requirements due to the presence of high ground water determined from additional ground water monitoring conducted at the site. HW has received the following additional documents in response to our September 14, 2020 peer review: • Stormwater Management Report for Proposed Redevelopment, 1600 Osgood Street, North Andover, Massachusetts, prepared by Langan Engineering & Environmental Services, Inc., dated August 2019 and revised September 2020 (502 pages). • Memorandum to Jean Enright, from Casey Raczkowski (Langan), regarding Stormwater Peer Review, dated September 16, 2020. (8 pages). • Permit Site Plans — North Andover, Massachusetts, Proposed Redevelopment for Hillwood Enterprises, L.P. and 1600 Osgood Street, LLC., Distribution Facility, 1600 Osgood Street, prepared by Langan Engineering & Environmental Services, Inc., last revised September 16, 2020 (146 sheets). ors ilt mu. @H,ors1eyW1tfenGrouPii t iren G,ro.0 P, Inc. Town of North Andover September 21, 2020 Page 2of6 Stormwater Management Design Peer Review HW offers the following comments concerning the modified stormwater management design. Our comments are presented to correlate with the stormwater networks described by the Applicant as being revised. The following comments relate to our September 14, 2020 peer review, follow up comments are provided in bold font. Network A-1 and Basins A-1.2, A-1.3, A-1.4, and A-1.5: 1. The Applicant has reconfigured Basin A-1.2 to include Basin A-1.5. Sheet CG106 includes a call out for Basin A-1.5 that should be removed. The label has been removed as recommended, no further comment. 2. The Pond Report for Basin A-1.2 was not provided in the revised Stormwater Report to verify that the inputs on the new pond size were consistent with the design plans. HW recommends that the Applicant provide the Pond Report, however assuming the input is consistent with the revised plan and infiltration rates, the peak elevations within Infiltration Basin A-1.2 appear reasonable. The Applicant has included the Pond Report for Basin A-1.2 in the revised Stormwater Report. No further comment. 3. Basin A-1.2 has greater than 4 feet of separation to estimated seasonal high groundwater(ESHGW) and in accordance with the Geotechnical Report contains soils with an exfiltration rate of approximately 7.2 iph. No further comment needed. 4. It appears that the Applicant has frequently matched the inverts of drainpipes coming into a manhole with the outlet pipes leaving the manhole. The preferred design is to match the crowns of theses pipes to provide full capacity of the larger outlet pipe. For example, in Network A-1 DMH 19 has two 24-inch pipes entering it at elevation 50.90 and a 30-inch pipe discharging from it also at elevation 50.90. The preferred design would be to lower the outlet pipe to 50.40. MH-18 has 12-inch, 18-inch, and 24-inch pipes entering at 51.11 and a 24-inch pipe discharging at 51.11. The 12-inch and 18- inch pipes should inlet at 12 inches and 6 inches higher than the 24-inch outlet pipe, respectively. This is not always feasible when cover over pipes is shallow, however HW recommends that the Applicant investigate locations where adjustments can be made to match the crowns of the pipes. For example, it appears that the outlet pipes from CB-7 and DMH-20 could be raised. The Applicant has acknowledged that the pipe inverts have been matched because of shallow cover. The Applicant has provided the hydraulic grade line which is adequate. 5. The Applicant is proposing to convert three single grate catch basins within the closed drain pipe network to Extend Dry Detention Basin A-1.4 to double grates. HW has no objection to this conversion. Basin A1.4 has not been modified from the previously approved design. No further comment needed. 6. Underground Detention Basin A-1.3 has not been altered. K du� II.� � � a ��O)0) � M,�� . s�� 8 06 5� �600(. rc' ud F w � R 1 ��u��,�.��i�-��,' . ��'�� a , lo 11:°x: Town of North Andover September 21, 2020 Page 3of6 No further comment needed. 7. HW has no objection to the revised grades within the southern parking lot. No further comment needed. 8. HW understands that the plans will be revised to include the relocation of the chiller unit pad to the south side of the existing 48-inch pipe. This relocation is anticipated to impact Basin A-1.2 and require some pipe reconfiguration. HW recommends that the Pond Report be provided for Basin-A1.2 for this change as well as the Hydraflow summaries. The Applicant has included the Pond Report for Basin A-1.2 in the revised Stormwater Report. No further comment. Network A-2 and Wet Pond A-2: 9. Notes on Revision Table page 2 reference Network A-1 and Sheet CG107. Minor adjustments proposed for CB-1, CB-6, and FES-2. Edits appear to be associated with Network A-2 and not Network A-1. HW has no comments associated with the minor adjustments. No further comment needed. 10. HW has no objection to the revised grades within the southeastern parking lot. No further comment needed. 11. Wet Pond A-2 has not been altered. No further comment needed. Network B-1 and Basin B-1: 12. The Applicant has raised the bottom of the extended detention basin because of information obtained in the monitoring wells regarding the ESHGW elevation. Monitoring well LB-122 (OW) noted a high groundwater at elevation 31.0. The bottom of the extended dry detention basin labeled Pond B-1 was raised from elevation 30 to elevation 31. HW agrees with the ESHGW and bottom elevation of basin. No further comment needed. 13. The Pond Report for Pond B-1 was not provided in the revised Stormwater Report to verify that the inputs on the new pond size were consistent with the design plans. HW recommends that the Applicant provide the Pond Report, however assuming the input is consistent with the revised plan the peak elevation of the extended detention basin will be approximately 6 inches below the stone emergency overflow and approximately 1 foot below the top of the basin. These parameters are considered acceptable. The Applicant has included the Pond Report for Basin B-1 in the revised Stormwater Report. No further comment. 14. The Total Suspended Solids (TSS) removal work sheet for B-1 includes an infiltration basin prior to discharge into the extended detention basin. HW was not able to locate the infiltration basin on the plan set and believes that manhole MH-5 is intended to be a proprietary stormwater structure. HW recommends that the Applicant confirm this and provide the required documentation for review. Information for either the location of the K du� II.� � � a ��O)0) � M,�� . s�� 8 06 5� �600(. rc' ud F w � R� ��u��,�.��i�-��,' . ��'�� a , lo 11:°x: Town of North Andover September 21, 2020 Page 4 of 6 infiltration system and sizing calculations or the type and sizing calculations for the water quality unit at MH-5 should be provided. HW further recommends that the TSS work sheet for B-1 be adjusted if necessary. The Applicant has clarified the call outs for Basin B-1 and has provided the required documentation. No further comment. 15. Sheet CG108 includes a call out to "two parallel lines of 145 LF 12" HDPE @ 0.5%" that appears to be left over from the previous submission. The call out has been removed as suggested. No further comment. 16. The closed drainage system between DMHs 13-12-11-10-9-8-5 is set at 0.3%. This is a relatively flat pipe and may be difficult to install at this shallow slope. HW recommends that an as-built survey be conducted immediately upon installation to verify that the entire line is properly installed. The pipe sizing calculations indicate that the velocity should be adequate to prevent scour. However HW further recommends that the closed drainage network be inspected quarterly and cleaned annually to maintain long term functionality. The Applicant has noted that an as-built survey will be conducted and that the pipes will be cleaned annually. No further comment. 17. Approximately 500 feet of retaining wall has been eliminated parallel to Basin B-1. HW has no issue with the revised grading. No further comment needed. Network C-1 and Basin C-1: 18. The Applicant has stated that it has added a second 24-inch outlet pipe from Basin C-1 to Basin C-2. A second pipe is shown on Sheet CG 104 however it does not appear to be labeled and the Structure Table for the C-2 Network has not been adjusted to include the second pipe from C-HW-1. The second 24-inch pipe has been labeled and information has been included in the schedule. No further comment. 19. Page 3 of the revision table notes that the bottom elevation of Infiltration Basin C-3 was raised from 38 to 39. HW believes that the Applicant is referring to Infiltration Basin C-1. Basin C-1 has adequate separation to groundwater. No further comment needed. Basin C-1 is the correct reference. 20. The Pond Report for Pond C-1 was not provided in the revised Stormwater Report to verify that the inputs on the new pond outlets and bottom elevations were consistent with the design plans. HW recommends that the Applicant provide the Pond Report, however assuming the input is consistent with the revised plan and infiltration rates the peak elevations within infiltration Basin C-1 appear reasonable. The Applicant has included the Pond Report for Basin C-1 in the revised Stormwater Report. No further comment. K du ojeoI.� � 1 8 ��O)0, � M,�� 8 06 5� �600(. ud �� m� �:m � tl T-11T� � i,�� R 1 ��u��,�.��i�-��,' . ��'�� a , lo i:°x: Town of North Andover September 21, 2020 Page 5 of 6 Network D-1 and Basins D-1.2, D-1.2, and D-1.3: 21. The approved design included one large infiltration basin with a bottom elevation of 40.0. Groundwater monitoring well LB-101(OW) noted high groundwater at elevation 40.5 closest to Osgood Street. The Applicant has now separated the original basin into three systems because of the ground water elevation and because of MassDOT's driveway interconnection. Extended Dry Detention Basin D-1.1 is closest to Osgood Street with a bottom elevation of 42.5. The modifications to Basin D-1.1 appear reasonable. No further comment needed. 22. Infiltration Basin D-1.2 is further west and connected to Basin D-1.2 with two parallel 24- inch pipes. The Bottom elevation is 41.5, providing 4 feet of separation from the bottom of the system to ESHGW. Monitoring well LB-102(OW) noted high ground water in this basin at elevation 37.1. No further comment needed. 23. Underground Infiltration Basin D-1.2 captures a significant amount of the parking lot runoff and runs parallel to and is connected to Surface Infiltration Basin D-1.2 by a pipe network. The bottom of the stone is at elevation 41.5 providing 4 feet of separation to ground water. The stormwater report refers to this basin as D-1.3. HW recommends that the plan be revised to avoid confusion. The call out for the underground infiltration basin has been revised to reference D- 1.3 on Sheet CG103. No further comment. 24. The Pond Reports for the D-1 Basins were not provided in the revised Stormwater Report to verify that the inputs on the new pond outlets and areas were consistent with the design plans. HW recommends that the Applicant provide the Pond Report, however assuming the input is consistent with the revised plan and infiltration rates the peak elevations within the three D-1 Basins appears reasonable. The Applicant has included the Pond Report for Basin D-1.1, D-1.2, and D-1.3 in the revised Stormwater Report. No further comment. 25. A detail sheet has been added to the Plan set for Underground Infiltration System D1-3. HW recommends that the Applicant provide a schedule of elevations on the Detail Sheet for ease in construction. The Applicant has added the schedule of elevations to Sheet CG505 as requested. No further comment. 26. HW understands that the Applicant is intending to replace the proposed isolator rows within the subsurface infiltration system D-1.3 with a proprietary separator. HW has no objection to this modification. However, we do recommend that sizing calculations for the hydrodynamic separator be provided for review. The Applicant has provided the sizing calculations for the proposed proprietary separator. No further comment. K du� II.� � � a ��O)0) � M,�� . s�� 8 06 5� �600(. ud F w � R 1 ��u��,�.��i�-��,' . ��'�� a , lo 11:°x: Town of North Andover September 21, 2020 Page 6of6 General Comments: 27. The Saturated Hydraulic conductivity value (k) utilized in Table 4: Groundwater Recharge Volume and Drawdown has been increased from 2.41 inches per hour (iph) to 8.27 iph. It appears that the infiltration calculations provided in Appendix H of the Stormwater Report support the revised values. No further comment needed. 28. Sheet CG203—The Table listed for D-1.2 Network is overlapped with the Basin Pond Reference Table and should be shifted for clarify. Sheet CG203 has been corrected. No further comment. 29. Sheet CG201 is missing a portion of the A-1.2 Inflow Network Table. Sheet CG201 has been corrected. No further comment. 30. HW has no objection to the adjustments being made for compensatory flood storage. The Applicant is providing adequate storage. No further comment needed. Conclusions The Applicant has adequately responded to HW 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. F Janet Carter Bernardo, P.E. Senior Project Manager CC: Conservation Commission u I �� , . � � d� I.� � � a ��, � M�� u� , � R 1 ��u��,�.��i�-��,' . ��'�� a , lo i:°x: