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HomeMy WebLinkAbout20210755 269 Broadway Site Plan CHA comment letterMay 24, 2022 Deborah LaBreche, PE City Engineer City of Saratoga Springs 474 Broadway Saratoga Springs, NY 12866 RE: 20210755 — 269 Broadway Review for Planning Board — Fifth Review CHA Project No. 58389-1003 Dear Ms. LaBreche: I am pleased to provide this letter prepared by CHA Consulting, Inc. pursuant to our independent engineering review of the referenced project on behalf of the Saratoga Springs Planning Board. The project includes a six - story mixed -use building on a 0.75-acre parcel at 269 Broadway. The Applicant is represented by MJ Engineering (MJE) with geotechnical engineering support from Terracon. During the course of the review of this project, concerns about its potential impacts related to groundwater came to the forefront after the Applicant provided a revised geotechnical study that provided information that was new and/or different from information contained in the previously submitted geotechnical engineering study. The project currently proposes two levels of underground parking 15 to 20 feet below observed static groundwater levels. The plans and geotechnical study provided by the applicant propose a secant wall system socketed into bedrock as a means to cut off groundwater and divert it around the project site. Dewatering will be required both during and after construction. The Applicant's 5/18/2022 submission provided additional information relative to concerns raised about potential impacts to groundwater, including the following, as summarized in the email transmittal from Walt Lippmann of MJ Engineering: 1. Hydrogeological Report (prepared by Terracon) dated 5/18/2022 2. Revised SWPPP dated 5/1/2022 a. Revised Section 3.2 Soils and Groundwater b. Section 6.5 Storm Water Quantity Analysis (incorporates proposed post construction dewatering) c. Revised model to account for the estimated post construction dewatering flows 3. Revised Site Plans dated 5/18/2022 a. Sheet C-120, incorporates an eight (8) foot wide sidewalk from Broadway to Hamilton b. Sheet C-110 and Sheet C-130, as per the City's arborist, the revised plans show the northern most tree along Broadway to remain as well as a portion of sidewalk adjacent to this tree to avoid disruption to the root system "Satisfying Our Clients with III Dinners Circle, P.O. Box 5269, Albany, NY 12205-0269 Dedicated People Committed to Total Quality„ T 519.453.4500 e 518.458.1 735 * www.chacompanies.com Deborah LaBreche, PE City Engineer May 24, 2022 Page 2 CHA's previous review comments are summarized in our letters dated September 15, 2021, November 5, 2021, February 11, 2022, February 18, 2022 and March 8, 2022. For clarity, this letter will not repeat comments from previous letters. This letter focuses primarily on additional information submitted by the Applicant on May 18, 2022 to address the following outstanding questions/concerns: 1. Design of the secant pile wall and dewatering systems should demonstrate no adverse effects to surrounding properties due changing groundwater levels or ground movements during construction and/or long term. The design should include a construction instrumentation and monitoring plan for groundwater levels, and structure and ground movements. 2. Springs are reputedly present within the project area. Both the further explorations and instrumentation proposed by the geotechnical engineer of record, and the design of the building, secant pile wall system, and dewatering system should address the possible impacts of springs on the project. 3. The design of the secant pile wall and dewatering systems should include an evaluation by a professional hydrogeologist that demonstrates no adverse impacts to the springs in Congress Park. CHA's review of the Applicant's 5/18/2022 submission is summarized below: Hydrogeological Report We have reviewed the hydrogeological report in the context of the questions/concerns raised above and note the following: 1. The report states that further investigations and monitoring of groundwater and movement will be done during construction. Stop work thresholds and contingency plans will be in place in the event of unforeseen conditions, and the City Engineer's office will have access to all reports. We believe the Applicant has responded appropriately and addressed the construction phase concern. 2. The report in not as clear with respect to addressing the potential for long-term impacts after temporary dewatering and construction have ended. It seems that any permanent changes in groundwater levels and flow patterns would be likely occur concurrently with the completion of the secant wall system, if at all, and would therefore be observed by the hydrogeologist during construction monitoring. We recommend the hydrogeological report be clarified to address the long-term question. If the hydrogeologist is unable to definitively address this question currently then the construction phase monitoring program should not be concluded until the hydrogeologist has reviewed the actual data collected and concluded that no negative long term impacts on other properties are likely. 3. The report satisfactorily addresses the question about the potential for impacts to the springs in Congress Park. RPvitPd SWPPP We reviewed the revised SWPPP to determine if it addresses the discharge of groundwater from dewatering operations into the City's stormwater system. According to the Hydrogeological Report, the construction phase (temporary) dewatering volume is 150,000 gallons, and the long-term dewatering will result in a discharge of 14 gallons/minute. We note the following: 1. Section 3.2 — Soils and Groundwater has been revised to indicate the presence of groundwater at 5-10 feet deep, which appears consistent with the geotechnical report. 2. We recommend a brief narrative be added to Section 5.1—Temporary Erosion and Sediment Control Measures to discuss the temporary dewatering operation. We would not normally anticipate water quality to be a concern with respect to groundwater provided that it does not come in contact with disturbed soil between the points of extraction and discharge. We also anticipate that the dewatering Deborah LaBreche, PE May 24, 2022 City Engineer Page 3 volume of 150,000 gallons can be discharged to the storm sewer with appropriate protective measures in place. 3. Section 6.5.3 — Pre -development Watershed Conditions and Design Points now indicates that Design Point 1 (DP1), which is the catch basin northwest of the project site, will be the design point for the permanent dewatering system. Table 6-6—Summary of Pre and Post Development Peak Discharge Rates at Design Points has been revised to include the permanent dewatering flow of 14 GPM or 0.03 CFS. This additional flow does not appear to be significant, and according to the information submitted will not result in post -development discharge rates exceeding pre -development rates for any of the storm events considered. Revised Site Plans Our review of the revised site plans confirms the following revisions have been made: 1. The sidewalk on the south side of the building has been widened to 8 feet in response to comments made at the last Planning Board meeting. The sidewalk is proposed as part of the civic space for the project. We note that plans for connecting the sidewalk to the Saratoga Greenbelt Trail system are not yet known and are beyond the Applicant's control. With that in mind, it appears this revision responds appropriately to the comments; however, the transition to the Hamilton Street sidewalk narrows to 5 feet wide and may need to be addressed in the future when the Greenbelt Trail plans are further advanced. 2. The plans have been revised to protect the existing street tree on Broadway at the north end of the site, based upon discussions between the Applicant and the City Arborist. This includes retaining the existing sidewalk along the north half of the project frontage. We note that this will result in the elimination of radiant sidewalk in this area. Radiant heating has also been removed from the new sidewalk from the Broadway building entrance to the southeast property corner. Radiant heat is still shown on the Hamilton Street sidewalk and on both east -west sidewalks. The Planning Board should be aware of this change and confirm it is consistent with their intent. City Engineering and Planning Department Review CHA is also in receipt of email correspondence from the City Engineer's office dated 5/20/2022 summarizing the thirteen comments previously issued by the City of Saratoga Springs Engineering and Planning Departments along with the City Engineer's current disposition (in CAPITAL LETTERS) for each comment. I have added my comments in italics: 1. Verify flow into the City storm sewer during and after construction. Show hydraulic calculations that verify the 15" pipe will be sufficient. - IS THIS IN THE LATEST HYDROGEOLOGYY REPORT? It is covered in the revised SWPPP. See SWPPP comments above. 2. Will the dewatering be temporary or permanent? A formal submittal will be required and possibly a PE stamp. WE KNOW IT IS PERMANAENT BASED ON THE CITY'S FLOW TEST ACROSS THE STREET - DOES THE PROJECT NOW INCLUDE THIS? Yes, please refer to the hydrogeological report. 3. Show how suspended particles will be settled/filtered out or this will be a violation of SWPPP. TONY IS REVIEWING SWPPP. See SWPPP comment #2 above. 4. .DONE 5. Applicant needs to research original springs and potential impacts to the foundation. - IS THIS IN THE LATEST HYDROGEOLOGYY REPORT? Yes, please refer to the hydrogeological report. 6. t F, rm r,I allutilities S E) W r te-sc- l e— DONE Deborah LaBreche, PE City Engineer May 24, 2022 Page 4 7. A "pre -blast" type survey will be required to confirm no negative impacts to adjacent properties. IS THIS REQUIRED OF THE PROJECT? No blasting is proposed for this project. Applicant indicated during the meeting we attended at City Hall that their intent is to conduct a pre -construction photo survey of the area to document existing conditions in the event of complaints of damage to neighboring properties. This is common construction practice, and we believe it to be a good one. 8. ;, par-ts. DONE 9. What is the status of the school property easement? Has it been filed? Show what is proposed for the switch gear on the plans? Matt suggested it may make sense to leave as is and get permission from the Bank and Hospital. UPDATE? The Planning Board requested at the last meeting that the easement be resubmitted to the current City Attorney. The current plans show the switch gear on the property to the north, closer to Hamilton Street than it currently is and screened by Junipers. The existing transformer for the property to the north remains as is. The new transformer for 269 Broadway is shown within the footprint of the service/trash area with gated access to the northern sidewalk. 10. Need permission from north property owner to remove their lights and traffic signs. DO WE HAVE THIS? Unknown. 11. DONE 12. Detail 8/C502 needs to specify OPEN RIGHT as Matt requested. - IS THIS DONE? Yes. Note #2 on the detail indicates valves open to the right. 13. DONE If you have any questions, please call me at 518-453-3927. Sincerely, A h . S Hato Jr., P.E. Vi -P ide t cc: Matt Zeno Susan Barden MJ Engineering (wlippmann@mjels.com) 269 Broadway LLC (gerard.moser@goprimegroup.com) V:\Projects\ANY\K5\058389.000\Corres\1003 269 South Broadway\58389_1003_letter5.docx