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HomeMy WebLinkAbout2002-10-07 Engineer Review Massachusetts Electric A National Grid Company , October 15,2002 Daniel McIntyre,P.E. Principal Engineer John Chessia Coler& Colantonio 101 Accord Park Norwell, MA 02061 Dear Mr. Chessia: Based on our discussion last week we have reviewed the drainage for the proposed Woodchuck Hill Substation in North Andover. User Defined Curve Number The substation yard is graded essentially flat with processed gravel and surfaced with a 6 inch layer of crushed stone. Our experience at other electric substations is that rainfall is stored in the stone and infiltrates into the ground. However in order to prepare the drainage analysis we needed to assign the substation yard area a runoff curve number. A curve number of 40 was selected. Review of the drainage calculations indicates that a soil classification of"B"was used to match the native soils of the site, Travel Time Our initial assumption was that travel time of watershed no. 1 would increase from 9 minutes under existing conditions to 18 minutes under proposed conditions. The watershed worksheets are attached showing potential travel times routes. This is primarily due to the assumed sheet flow through the substation yard crushed stone. As a sanity check we revised the proposed drainage to Mosquito Brook using the same time of concentration as existing conditions. The runoff from watershed no. 1 does increase but the combined flows to Mosquito Brook(watershed no. 1 plus watershed no. 2)remains essentially the same. This is because runoff from watershed no. 1 hits Mosquito brook quicker and does not combine with the peak of watershed no, 2. Recharge Trench We agree with your recommendation to construct a stone recharge trench along the driveway to minimize runoff from the pavement to the side-slope along wetland series no. 1. Also the grading in the area between the substation yard and driveway has been revised to create a slight depression to further increase recharge and decrease runoff. Attached is a marked up drawing showing the recharge trench and revised grading. If these changes arc acceptable we will revise the drawing formally for construction, Thanks for all your help in expediting this review. Please call if you have any questions or require additional information. Sincerely, Daniel McIntyre, P.E. Massachusetts Electric 6 Bearfoot Road 10/21/2002 15:00 FAX 781 982 5490 COLLtt & COLAMON10 [a002 L-oLJLANTON1 Z ENGINEERS ANo SUE--NTISTS October 21,2002 Kathy McKenna Town Planner Planning Board Town Hall Annex 27 Charles Street North Andover,MA. 01845 RE: Engineering Review Foster Street Electric Substation New England Power Company Site Plan Dear Ms. McKenna: In response to your request,Coler& Colantonio,Inc. has reviewed the submittal package for the above referenced site, Our efforts included a comparison of information submitted with respect to the requirements of the North Andover Zoning Bylaws. The submittal package included the following information: Plans Entitled a "Woodchuck Hill Substation No. 56, North Andover, Mass." consisting of 11 sheets dated March 21, 2002, prepared by National Grid USA Service Company,Inc. Received October 4, 2002, "Stormwater Design Report Woodchuck Hill Substation", prepared by National Grid USA Service Company. Received October 4,2002. "Sound Study — Proposed Woodchuck Hill Sub. North Andover, MA" dated August 16, 2002, and prepared by National Grid USA Service Company. Received October 4, 2002. During our review of the project, further information and plan revisions were requested of the engineer. The information requested was provided on October 16, 2002. Our comments are as follows: 101 Accord Park Drive 781 992-5400 Norwell,MA 02061•1685 Fax:781 982-5490 10/21/2002 15:00 FAX 781 882 5490 COLOR & COLANTONIO Ia003 ,Site Plan Review 1. Section 8,3)5,)c.) The submitted site plaits do not have a certified engineering stamp as rewired. The landscape plan has no documentation stating that a certified landscape architect registered in the Commonwealth of Massachusetts performed the designed. 2. Section 8.3)5.)vii.) The curve number and time of concentration figures used in the submitted calculation package for the electric substation stone yard area does not appear to accurately reflect the proposed conditions. We note that this will be offset by the inclusion of the recharge trench along the driveway and the depression designed between the substation yard and driveway. Both these measures were added following our conversation with the engineer. No credit has been taken for these measures in the drainage calculations submitted. We do not anticipate a measurable impact on Mosquito Brook from this project. 3. Section 8.3)5.)vi.) The submitted plans do not have a table of zoning information. It is unclear that the Zoning Board needs this information for this type of project, 4. Section 8.3)5.)x,) The submitted plan does not demonstrate any parking locations. It is understood that the proposed use of the site will not require frequent visit or high occupancy visits. As a result the vehicles that are at the site should,be able to utilize the driveway and turnaround areas for sufficient parking. 5. Section 8,3)5)xi.) The Notice of Intent was not submitted for our review. The locations of vernal pools were not shown on site plans but are referenced within the drainage calculations submitted. Reportedly the Conservation Commission has approved the plans, therefore this issue has been addressed by others. 6. Section 8,3)5.)xii.) The location of any signs associated with the project were not indicated on the plans. The size, location and type of sign for the substation should include safety warnings, ownership and contact details incase of emergency etc, 7. Section 8.3)5.)xvi.)The location of refuse storage, if any, was not indicated. This has been addressed in the narrative associated with the submittal. We do not recommend a durnpster at this location due to the potential for vandalism. 8. Section 8.3)5.)xv.)Trees with a diameter over 12" were not indicated. It is unclear if the Board waived this requirement. 9. Section 8.3)5.)xvii.) The location and direction of lighting was not indicated. The detail provided indicates that the lights are for emergency use only. 10. Section 8.3)5.)xxii.)Typically reviewed by Town Staff. 11. Section 8.3)5.)xxiii,)Typically reviewed by Town Staff. 10/21/2002 15:01 FAX 781 982 5490 COLER & CCLANTONIO €91004 12. Section 8.3)5.)ii.)d.) Although it is unclear that the proposed drainage system meets TSS zvmoval standards based on the data provided. It is understood that the Conservation Commission approved it therefore it should be satisfactory. For this site we do not anticipate significant sediment generation given its limited use. We appreciate the opportunity to assist the Planning Board on this project and hope that this information is sufficient for your needs. if you have any questions please do not hesitate to contact us. Very truly yours, COLER &COLANTONIO,INC. ohn C. Chessia,P.E. Associate XC: National Grid USA Service Company,Inc.