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HomeMy WebLinkAbout2003-08-19 Response to VHB Comments SPR RF& SHUMW" MEMO Date: August 1, 2003 .lob No.: 00-4207 To: Justin Woods, North Andover Planning Department From: John Scott, Rist-Frost-Shumway Engineering, P.C. Re: Responses to VHB Comments of 07/31/03 Brooks School Athletic Facility We have received and reviewed the third round of comments by the Board's consultants, VHB, dated July 31, 2003. The following is our response thereto, accompanied by revised drawings C301 and C303. We have eliminated mention of those items which VHB has accepted. Responses to Drainage Comments: #15 We have added crushed stone bedding for the riser - see revised drawing C303. #17 Pipe size increased to 12-inch. See note 40 on revised drawing C303. #18 Underdrain added to detention pond 2. See revised drawing C301 . #22 Spot grades along west wall of the Athletic Facility added. See revised drawing C301. #28 Rip-rap apron added to outlet from detention pond #1 . See revised drawing C301 . #33 The revised HydroCAD model and drainage calculations referred to in our previous response & #34 were submitted with our 7114/03 memo. VHB misunderstood that we had revised them a second time. In fact, they did have in their possession our latest product. We have alerted them about this and are confident that a check of the 7/.14 information will result in their being satisfied with our previous responses to these two issues. JtS:rlr AS142071North Andover P1ng.JWoods.080?03.m.wpd Enclosures cc: Timothy McIntosh, VHB (w/ enc.) John Trovage, Brooks School (w/out enc.) Bob Peterson, Cannon (w/out enc.) Tom Regan,'Regan Associates (w/out enc.) SHUMMI' f" lot F M0=MA"%L Date: July 24, 2003 .lob No.. 00-4207 ..v "�"' VED To: Justin Woods, North Andover Planning Department ,11 k 200, From: John Scott, lust-Frost-Shumway Engineering, P.C. NC�rt I'M ANDC Vc/ fi Re: Responses to VHB Comments of 07/18/03 ' § +! �n�rzo► r 'tP�itNt" Brooks School Athletic Facility We have received and reviewed the second round of comments by the Board's consultants, VHB, dated July 18, 2003. The following is our response thereto, accompanied by attachments. We have eliminated those items which VHB has accepted. • Section 7.4 - The project Architects have discussed the height issue with the Town Building Commissioner, who has determined that neither a waiver nor a variance is required. We note further that the roof peak will be several feet lower than in the 2001 design, for which a Building Permit was issued. Responses to General Comments: #3 In computing the invert elevation of the existing sewer line in Manhole 4, we made an interpolation error(subtracted instead of added). The correct invert elevation at Manhole 4 is 183.16. The elevations of the other pipes in the manhole have been adjusted to match. This existing line has been functioning for some time and is of course pitched in the downstream direction. Our apologies for the error. #1 1 Drain manholes 50 and 51 have been added to unlink catch basins 19 and 20 from the main line of the network. Hydraulically this is a negligible change, so we did not feel it necessary to revise and re-run the HydroCAD program. #12 The elevation of the lowest set of openings in the outlet riser to pond #1 has been changed on drawing C303 to match the pond bottom of 173.3. Our apologies for not following through on this correction in our first response. #13 Cleanouts to grade have been added to roof leaders 41 and 45, and for infiltrator outlet 40. These lines will be carrying clean roof runoff and are unlikely to clog. The interior plumbing for the roof drains will incorporate cleanouts, so this should suffice for the underground portion also. A cleanout detail is shown on C502. #15 In our first response, we meant to say "precast concrete base sections," not barrel sections. We have further clarified the details on C303 to show this intent. wRFSlOm N'itiMv wm Vq ry[ p 6 1y� SHi1XMWAV V,n 15o uN � Alt e Mr. Justin Woods July 24, 2003 North Andover Planning Department RFS 00-4207 RE; Responses to VHB Comments of 07/18/03 Page 2 Brooks School Athletic Facility #17 This project is also being reviewed by the Conservation Commission for an amendment to the DEP permit. Their consultant, Eggleston Environmental, has agreed with the proposed design concept in our 7/10/03 memo. As this matter seems closer to the mandate of the Conservation Commission than to that of the Planning Board, we respectfully propose to keep the infiltrators in the project unless directed otherwise by the Conservation Commission. #18 Detention pond #2 is a dry pond, with outlet invert elevation equal to the bottom of the pond (see response to #12, above). Any groundwater which enters the pond will flow immediately out the outlet pipe. Thus the pond is normally empty, and its entire volume is available as active storage. Lowering the local water table at the pond will not tend to dry out the wetland, as the pond bottom is well above the level of the wetland. The water table under the adjacent hockey rink has been lowered by its underdrain system ever since its construction, as will the water table under the proposed Athletic Facility. There is nothing unusual about lowering a local water table to prevent water problems inside structures, nor is it unusual to construct a dry detention pond. This same issue was raised in 2001 by the Conservation Commission, which is satisfied with this response. The Downstream Defender will be surcharged briefly during major storm events. Operation of i the units and their removal efficiencies are unaffected by submergence. Attached is a confirmatory memo from H.I.L. Technologies, manufacturers of the Downstream Defender. Furthermore, the treatment standard is to remove 80% or more of the total annual TSS load, not necessarily 80% of the TSS in every single event. Most of the annual TSS load occurs during events of ordinary intensity. #21 See memo from H.I.L. Technologies. #22 Finished grade along the west exterior wall is 191 .0, as shown on drawing L241 . Catch basin rims are set 6 inches lower at 190.5. From there,the finished grade slopes upward to the grade along the road. The spot grades on A301 are shown at the very corners of the building, where the grade drops around the north and south ends. If one carefully observes the grade line along the base of the building shown on the West Elevation view on A301, it agrees with L201 . Obviously,the intent is to slope grade away from the building into the drainage system to avoid ponded water against the building. #28 We have extended the riprap of the secondary outlet 14 by 10 ft. to create an apron 15 and have moved the outlet pipe so it discharges onto the apron. The riprap sizing nomograph yields a d50 of 0.4 ft., so 6° stone is used. #32 Finished grade contours have been added around DMH 37. u ��Nll�l�lftll�� � a ����,i� uiuv i11�in�,� S14Uf AV' Mr. Justin Woods July 24, 2003 North Andover Planning Department RFS 00-4207 RE: Responses to VHB Comments of 07/18/03 Page 3 Brooks School Athletic Facility #33 The bypass was added to eliminate ponding in the 25-year storm at basins 19 and 20. It becomes active whenever flow depth exceeds 12" in the pipe to the Downstream Defender, and diverts some of the flow around the Defender,thus avoiding enough head loss to prevent upstream ponding. Though this pipe is surcharged during the height of the 25-year storm, it is passing a high volume of water(4.08 cfs) and is effective at avoiding ponding, which is its purpose. This is confirmed by HydroCAD. #34 Please note that the revised HydroCAD model of 7/1 1/03 has a dt of 0.01 hours (or 0.6 minutes), whereas our original model of 5/29/03 used 0.1 hours. See page 1 of each storm analysis. This allows for an accurate modeling of drainage areas with times of concentration less than 5 minutes. JLS:rIr JLS\4207\North Andover Ping.JWoods.072403.m.wpd cc: Timothy McIntosh,VHB (w/ enc.) John Trovage, Brooks School (w/out enc.) Bob Peterson, Cannon (w/out enc.) Tom Regan, Regan Associates (w/out enc.) 1 i i 1 l i s i0 .S5 AM iiYDf2E3 INTERNATIONAL JUl —23-2003 —�— ��"7 Hydr?,f TLC internationa FAX TRAWSM18910" Company: Ri9t-Frost ghumway pngit~eerinq To: John Scott pate: July 23,2003 603-528-7853 pages: 1 phone#: 603.524-4647 Gc: Fite 2001-067 From: pavid Mangeau _North Andover', MA :tubjelK: Brook School Athletic Facility of the Down Undstream Defender is John, our earlier telephone ccnversatton,the pe1formance Confirming nce of a surcharged conditlon on the outs pnterrded.and sod im Ana not affected by the press l n the flow path through the device rontinuia aurGharged condit ion,to , floatables remain protected from Weehaut. to to contact me at 207-756-6200 axt. 1F you require additional information, please don't hesita t4" ea les Manager Inc, a 94 iHutohins Drive s por6an C (Whil 0002 ec�aom W.L. Te�Bnobgy'fax: (207)756-1)212 • E-mail'. "del: (207) -62 ?echnoi x: Ina.15 a eubaidigrsl of hydro Intarndklon0l pta GmnupWw utl(V,wn 1ronN M RFSSHUMWAY ME Date: July 14, 2003 ,JUI, 1 4 200 00-4207 4 Job No.: NORTH ANDOVE_R M F NT To: Justin Wood, North Andover Planning Department t,. NNINQ UFPARTMEaNT e From: John Scott, Rist-Frost-Shumway Engineering, P.C. F Fr Responses to VHB Comments of 07/01/03 Brooks School Athletic Facility We have received and reviewed the comments by the Board's consultants,VHB, dated July 1, 2003. The t following is our response thereto, accompanied by attachments. We use the same order as in VHB's 'r letter. f ° Section 4 - No response. r; • Section 5 - The Operations Standards of Section 5.7 of the bylaw will be incorporated III verbatim into the Earthwork specifications in the construction documents. • Section 6 - There will be no signs associated with the project. Buildings at the School are not !' separately identified with free-standing signs. Here and there on campus are f small signs directing visitors to various buildings, and the new facility will be added to some of them. There will be no signs in the sense of the bylaw. • 7.1 - No response. 7.4 - The height listed in the Application was incorrect. The height listed was the I vertical distance from first floor to the roof peak. By Mass. Building Code convention, height is measured as the distance between average ground elevation around the perimeter(186-6") and the mid-point of the pitched roof (220'-2"). Thus the height is 33'-8", which is less than the allowed 35'. !; A variance is not therefore required. This would explain why the project received a Building Permit in 2001 and no height issue was raised at that time. • 8.1 .1 & 8.1.2 - We stand by our comments in the Narrative, and refer to the 1999 parking report which was well received by the Planning Board at that time. This facility will not be open to the general public. Most of the users of the Facility will be boarding students who will come and go on foot. All of the functions in the Facility which draw a crowd (e.g., basketball games) are already occurring in the existing gym, t the same ty pe of fa cility as This is no �'✓ so there is no need to increase parking. Th Yp that covered by the bylaw. i 1 I IOVmV�uLL RFSSHUMW" Mr. Justin Woods July 14, 2003 North Andover Planning Department RFS 00-4207 RE: Responses to VHB Comments of 07/01/03 Page 2 Brooks School Athletic Facility 9 8.1.3 - Parking dimensions have been added to the plans in conformance with the bylaw. • 8.1 .4 - See response to General Comment #4, below. 6 8.3-5(c) - The "L" and "A" drawings have been signed and stamped. i • 8.3-5(e-i) - Locus map provided in Application Package. • 8.3-5(e-ii) - No response. 8.3-5(e-iv) - There are no easements or legal conditions that affect the proposed development. `r 8.3-5(e-v) - Grading plans have been cleaned up for better legibility. • 8.3-5(e-xii) - Seat wall section provided. There will be no signs. • 8.3-5(e-xiii) - Dimensions of road and walkway widths have been added and curbing locations have been clarified. r • 8.3-5(e-xviii) - See responses to Drainage Comments, below. 1 8.3-5(e-xix) - No response. fi Y 8.3-5(e-xx) - DEP permit 242-1057 remains in effect from the 2001 project. We are proceeding with an amendment to that permit covering the changes to the project with the Conservation Commission. • 8.3-5(e-xxi) - See responses to General and Drainage Comments, below. Responses to General Comments: #1 This is correct. #2 There is an existing fire hydrant adjacent to Service Road in the southwest corner of the site, which shows on the plans. The Fire Department has been consulted on multiple occasions by the project team. They participated in the Technical Review Committee meeting of 05/08/03. #3 Sewer elevations have been added. The typical trench detail on C502 applies to gravity sewers. 1 RFS SP' M f Mr. Justin Woods July 14, 2003 North Andover Planning Department RFS 00-4207 RE; Responses to VNB Comments of 07/01/03 Page 3 Brooks School Athletic Facility #4 Three handicapped spaces are now shown. A symbol will be painted on the pavement, plus a sign. #5 Identification of curb tip-downs has been added. Detail of tip-down on C502 corrected. #6 Layout data added. #7 The existing parking area, which will not be re-graded, sheet flows in an easterly direction, across the gradual grassy slope and into the wetland. Contours are shown on the plan, and the flow direction is evident. #8 See response to 8.3-5(e-xiii), above. #9 The wall at the northeast corner of the new building has been eliminated. There are no site walls other than the seating wall (see response to 8.3-5(e-xii), above). T #10 There will be no signs. Responses to Drainage Comments: r Please note that in response to a comment from Eggleston Environmental, consultant to the Conservation Commission, sediment forebays have been created in the two detention ponds via the use of stone berms. #11 RFS feels that requiring all catch basins to flow into drain manholes would result in an excessive number of underground structures on a small site, at very little benefit to the stormwater system. The Town has allowed linked catch basins on similar previous projects on the campus. We do acknowledge the 25%TSS removal for deep-linked catch basins does not apply when they are linked. The TSS calculations have been revised to dispense with this element. #12 The pond bottom and lowest outlet are intended to match so there is no standing water; the mismatched elevations have been corrected. #13 A manhole has been added to the downspout leader pipe on the northwest corner. #14 Notes calling for flared end sections at outfalls 40 and 41 have been added. They were left off i unintentionally. #15 The riser has been changed to a precast concrete barrel section with flat top incorporating a flush grate. i #16 Legible copy of SCS Map 23 attached. l RFSSHUIVIWAY Mr. Justin Woods July 14, 2003 North Andover Planning Department RFS 00-4207 RE: Responses to VHB Comments of 07/01/03 Page 4 Brooks School Athletic Facility #17 The recharge calculations have been revised due to new information revealed by the soils investigation. The revised design incorporates sufficient roof area to compensate forthe entire Maintenance Building. #18 The location of the test pit is shown on C301 and the boring locations are shown on both C201 and C301 . #19 Norse Environmental Services performed test pits and percolation tests on July 3, 2003. Report is attached. Based on the results, it is apparent that the original soil on-site has been removed and otherwise disturbed. See separate memo of July 10, 2003 to VHB and Eggleston for discussion of the results and impact on the recharge design. Revised drainage calculations are enclosed, which include revised recharge calculations. #20 Fill increased in extent and fill slope flattened to minimize breakout. #21 Sizing calculations for the Downstream Defenders included in Drainage Calculations. �I #22 Spot elevations at building corners and more contour numbers added to plans. #23 Note 4 corrected. #24 Redundancy eliminated. #25 Wording clarified. #26 Conflict between notes and details eliminated. #27 Figure 3 included - see revised riprap sizing calculations included in Drainage Calculations. For most of the outfalls,the result is an absurdly small stone, so 6" minus was selected as the j, minimum size. #28 Apron for outfall 10 shown; outfalls 13 and 40 go to a level spreader. #29 This was an errant note left over from the 2001 plans which escaped erasure. We have reused #16 for a new note. #30 Riprap sizing calculations revised. #31 Schedule of apron sizes added to plans. #32 This manhole rim has been raised and surrounding ground surface mounded slightly. I i FSSIIUMWAY Mr. Justin Woods July 14, 2003 North Andover Planning Department RFS 00-4207 RE: Responses to VHB Comments of 07/01/03 Page 5 Brooks School Athletic Facility #33 A bypass has been added around the Downstream Defenderto divert high flows around the unit into the detention pond. This bypass precludes any surcharging of catch basins 19 and 20. The basins have been moved slightly to coordinate their location with curb tip-downs. #34 We understand that VHB prefers to limit times of concentration to a minimum of 5 minutes, for pipe sizing purposes. This is a very conservative approach, as it theoretically forces more flow thru certain pipes, as all the peaks occur at once. RFS feels this is unnecessarily conservative. Our design shows that the system can handle the 25-year storm and is required by the Town DPW. #35 The small volume in the sumps has been assumed full in the revised calculations. JLS:rlr AS\42071Norfh Andover PIngJWoods.071403.rn.wpd CC: Timothy McIntosh, VHB (wl enc.) John Trovage, Brooks School (w/out enc.) Bob Peterson, Cannon (w/out enc.) Tom Regan, Regan Associates (w/out enc.) OEM�Amok ao)4 Pa©1q4 sHuMW" MEMO- D.ate July 10, 2003 RECEO VED Job No.; 00-4207 J1„ 2003 To: Lisa Eggleston, P.E., Eggleston Environmental PLANNING, ANDOV RfMEfVT Timothy McIntosh, P.E.,Vanasse Hangen Brustlin, Inc. From; John Scott, P.E., Rist-Frost-Shumway Engineering, P.C. Re: Brooks School Athletic Facility - Soils Results We have received comments on our submissions to the North Andover Conservation Commission (from and the Planning Board (from Vanasse Hangen Brustlin, Inc. (VHB)). Both o Eggleston Environmental) f you advised that site-specific soils testing be conducted to confirm the design of the groundwater recharge facilities. Accordingly,test pits and percolation tests were conducted by Norse Environmental Services, Inc. on July 3, 2003. Norse's report and DEP Form 11 are enclosed. Norse found that the soils were not the Sutton type shown on the SCS county maps. The soils are more like a Woodbridge soil, with no percolation observed. Woodbridge is a hydrologic group C soil, whereas soils with very low percolation are in group D. Norse notes evidence that soils on-site have been disturbed. While we have no topography of the parcel which pre-dates the construction of the hockey rink, it appears obvious that a good bit of the original bank on the west side of the rink was cut back to make way for the building. This disturbed bank is the proposed site for the Athletic Facility footprint. Later when the lower athletic fields were constructed north of the rink, further cuts into this bank no doubt were made. Smaller amounts of earthwork took place on the south side of the site for the Maintenance garage and the former Peabody House. Thus,the site of most of our added impermeable rooftop and pavement will be on soils that have been disturbed at various times in the past. DEP design criteria call for recharging the first 0.10" of rainfall for group C soils, whereas it is 0.25" for group B soils. Our submitted design, priorto the Norse investigation, assumed Sutton group B soils. DEP requires no post-development recharge for group D soils. The north side rechargers are situated in fill. The bottom of the units (elev. 183.17) will be 3.0 feet above the seasonal high watertable (ground elev. 181 .6; estimated high watertable 18" down). DEP guidelines call for a minimum depth of 2 feet between recharges and the watertable, so this criterion is met. Rather than argue whether this is a group C or group D site, we propose the following concept: ' RFSSHUMWAY Ms. Lisa Eggleston, P.E, Eggleston Environmental July 10, 2803 Mx Timothy k�cIntoch, P.E., Vono`xe �1ongen RnouHin, Inc. RFS 00-4707 RE: Brooks kuSchonl AthloticFoc|lih/ - SoiloResolb Page 2 1 . Size the recharger system using group C sizing criteria. 2. Extend the fill generously beyond the infiltrators to minimize any breakout problems. 3. In the hydraulic model, use group D for the soils around the site in the areas where prior disturbance is obvious, and assume zero exfi|trotinn from the nachongen. This will result inoconservative design for the drainage piping and detention ponds and will provide recharge for however muck the soils can absorb, im the spirit cf replicating whatever recharge iu happening now. We are proceeding with addressing the other issues raised by your respective firms and will respond with revised plans, calculations, etc. shortly. But as the soils issue appears to be the most important, ,/e wanted to bring this fo your attention inadvance. If either nf you have serious objections tnanything contained herein, vve would appreciate u coll. ][S:rlr JLS\4207VEqe6*mm M6mmsh.077003m.^pd Eno|oyun*v cc: Julie Ponino, N. Andover Cons. Comm. (w/notenc.) Justin Woods, M. Andover Planning Board (w/outenc.)� RFSGiD@V_IPN@Qff SHUMW" MEMO Date: June 2, 2003 Job No.: 00-4207 To: Julie Parrino, North Andover Conservation Commission From: John L. Scott, Rist-Frost-Shumway Engineering, P.C. Re: Watershed Protection District at Brooks School Enclosed is a plan of the Brooks School campus with Watershed Protection District (WPD) boundaries, including the limits of the Conservation, Non-Disturbance, and Non-Discharge zones within the WPD. We inadvertently left this out of the materials submitted last Friday. The Athletic Facility project area drains into the northerly wetland, which does not connect to Lake Cochichewick. Thus, the project is outside the District. JLS:Hr JLS14207\Norfh Andover ConsJPardno.060203.rn.WPd Enclosures PO cc: Justin Woods, North Andover Planning Dept. (wl enc.) JUN 0 A 2005 John Trovage, Brooks School (w/ enc.) Tom Regan, Regan Associates (w/enc.) NOI"�'fl] �NOOVFR Bob Peterson, Cannon Design (wl enc.) 11-ANNING i)F-,PARTMENT Lisa Eggleston (wl enc.) Timothy McIntosh, VH13 (w/enc.)