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Home My WebLink About09/14/2020 - HWG Stormwater Peer Review - - 1450 Osgood 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 September 14, 2020 Ms. Jean Enright, Planning Director Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Ref: 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 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 documents for review: • E-mail dated September 10, 2020, from Timothy O'Neill regarding two additional revisions to the plan set and notification that the Conservation Commission has continued its hearing until September 23, 2020. • Tables listing revisions per stormwater conveyance train and sheet number (5 pages). • Geotechnical Engineering Study for 1600 Osgood Street, North Andover, Massachusetts, prepared by Langan Engineering & Environmental Services, Inc., dated June 19, 2020 (259 pages). ors it mu. @H,ors1eyW1tfenGrouPii t iren G,ro.0 P, Inc. Town of North Andover September 14, 2020 Page 2of5 • Stormwater Management Report for Proposed Redevelopment, 1600 Osgood Street, North Andover, Massachusetts, prepared by Langan Engineering & Environmental Services, Inc., dated August 2019 and revised August 2020 (297 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 August 28, 2020 (133 sheets). 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. 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. 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. 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. 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. 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. 6. Underground Detention Basin A-1.3 has not been altered. 7. HW has no objection to the revised grades within the southern parking lot. K-\Rrum c,WW. l,0 8 i� ( 'l 8 065 600 . u � ��'A\ � ! � III III d I Town of North Andover September 14, 2020 Page 3of5 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. 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. 10. HW has no objection to the revised grades within the southeastern parking lot. 11. Wet Pond A-2 has not been altered. 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. 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. 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 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. 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. 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. 17. Approximately 500 feet of retaining wall has been eliminated parallel to Basin B-1. HW has no issue with the revised grading. K-\Rrum c,WW. lA) 8 i� ( �l 8 065 600 . u � ��11 R � ! � III III d I Town of North Andover September 14, 2020 Page 4 of 5 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. 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. 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. 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. 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. 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. 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. 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. 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. K m��,I��. ��lii i�i 'i i"7 ..* �' ".�.m �oo��i ��... ��,..� s 'rye II d ,„ . III d WW i �� ! �!,W II'��I � ��' !,��W ..�.� � �`� l,�� II,� �I�� II,�, � �, �II�� Osgood�Iulmul w �,�- � � � � � � � I Flleer "I, �. w 'u )j I Stl mJ111"',, Town of North Andover September 14, 2020 Page 5 of 5 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. 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. 29. Sheet CG201 is missing a portion of the A-1.2 Inflow Network Table. 30. HW has no objection to the adjustments being made for compensatory flood storage. The Applicant is providing adequate storage. Conclusions HW recommends that the Planning Board require that the Applicant address these comments as part of the Board's review process. 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 K-\P rqj ects\2,0 1,, 8 F T � g11'! 60 s,good SL11h)