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Home My WebLink About2005-02-02 Response Comments to Civil Review SPR I j andover consultants 1 East river Piave inc. Methuen, Massachusetts 01844 Tel. (978) 687-3828 Fax(978) 686-5100 December 20,2004 f b4 {/ Mr.Tim McIntosh V.H.B. 101 Walnut Street P.O.Box 9151 Watertown,MA 0247 1-9 1 5 1 Regarding: Flight Craft Hanger Lawrence Municipal Airport Mr. McIntosh: Please find enclosed the following items: • Site Details plan with revision date December 20,2004. • Hydrocad calculations for pre&post conditions. • Figures I &2, pre&post subcatchment areas. • Table 1,pre-development vs.post-development peak rates of runoff. • Calculations for capacity of existing drainage swale. On behalf of the applicant,Dale Gross,we would like to respond to the comments made in your letter of Engineering Review addressed to the Town of North Andover Planning Board dated December 13,2004. For the purpose of this letter,Andover Consultants,Inc.will be referred to as"ACI". Our responses are in the same order that they were presented in your review letter. Section 8.3—Zoning Bylaw 8.3.5.e.ii It is the opinion of this office that leased land on the airport is a unique situation and that this section does not apply. The plans prepared are consistent with prior projects on the airport. 8.3.5.e.iv The applicant knows of no easements or other legal encumbrances related to this project. 8.3.5.e.vii As mentioned in the drainage report,specific site restraints do not allow for a reduction in peak rates of runoff at Design Point 1. These restraints are high ground water, failed percolation test,and limited leased area. Stormwater runoff is mitigated to the greatest extent practical. 8.3.5.e.ix An elevation plan was submitted to the Planning Board with the Site Plan Application. 8.3.5.e.xvii Exterior lighting is shown on the Site Plan. 8.3.5.e.xviii See comments below. Civil Engineers * Land Surveyors • Land Planners andover consultants Inc. Drainage Comments 1. The 10 min. time of concentration for subcatchment A has been broken down in the f evised Hydrocad calculations. The time of concentration for Subcatchment B has been revised to 10 minutes for pre and post conditions. See revised Figures 1 &2 for Tc paths, Subcatcbment C remains a direct entry of 5 minutes due to its small tributary area. This is justified and is common engineering;practice. 2&3. The CA values are calculated correctly. The Sum CA is the added CA totals from each tributary row. It is common engineering practice to add tributary CA values in series(Sum CA)and multiply them to an intensity value. The intensity value decreases as flow travels through pipes. Separating out the flow from the pipes yield no net difference in flow because the intensity value"I'at Existing CB2 is 4.3 for both overland and pipe flow. Therefore, there is no need to separate the two flows. 4. The attached revised Site Details sheet includes a hood with the proposed catch basin. 5. The Applicant is not required to comply with DEP Stormwater Management Policies. The Sediment& Oil Separator for this design is sufficient in removing sediments and suspended particles and has been accepted in several communities in this area. Therefore, it is the opinion of ACI that there are no discrepancies in this detail. 6. The runoff numbers generated by Hydrocad between 0 and 5 hours area near zero and do not affect the overall results. However,to satisfy your request,I have included revised calculations with the hydrograph beginning at zero hours. 7. Calculations for the existing swale are included with this letter. There are two scenarios included. One scenario calculates the remaining peak runoff rate from the 100-yr storm event,which is not handled by the subsurface drainage system(5.70 cfs). The other scenario calculates the total peak runoff rate from the storm event(13.57 cfs). In both cases the existing swale has the adequate capacity to handle the flow. General Comments 1. The water gate is located on an existing waterline, which happens to be near the electric line. 2. The access road on the north side of the building is not for emergency access. The emergency vehicles will access the building via a key access gate which will allow them to drive over to the taxiway. 3, Issues of views of the taxiway are under the jurisdiction of the Federal Aviation Administration(FAA). The Applicant has submitted a plan to the FAA and is awaiting their comments. 4. A pavement detail has been added to the Site Details sheet. The high ground water will not affect the pavement design. If you require any additional information, please feel free to contact me. Thank you. Sincerely, ANDOVER,,E SUI,TA S INC. eph P.Burke, P.E. Senior Civil Engineer cc.North Andover Planning Board JPBijpb P:1199-611LETTER-Vl4B-122004.doe FROM ANDOVER CONSLUANTS, INC. PHONE NO. : 97 6B6 S1(� Jan. 24 005 00:39AM P2 q �- 1 East RivBr PiBCa andover Methuen, Massachusetts 01844 consultants Tol, (978)687-382B Inc. Fax(978)60-5100 January 13,2005 North Andover Planning Board North Andover Town Offices 1-mom 4ao d aG0C3Q , North Andover,MA 01945 JAN 2005 Regarding, Flight Craft Hanger ITI 1<,awrence Municipal Airport Pl.A VNINQ u�`p�+ V NT Members of the Board: On behalf of the applieant,l7ale-Gross,we would 1}�Town of North Andover Planning Board dated e to respond to the conamts made in thO V-H-D' second letter of Engineering Review addressed to the December 29 2004. In this letter, Andover Consultants is responding to the remaining V,H.B,comments that stilt need to be addressed. It is our understanding of VH)3,s letter that the decision on the three remaining comments rests solely with the planning Board, Stetion 8.3—Zoning Bylaw 8.35.e.ii VHB is recommending that the Applicant request a waiver from this section of the Zoning Bylaw. The Applicant does not believe that a waiver is necessary. However,if the Planning Board believes a waiver is necessary,consider this a request for a waiver Of this section of the Zoning Bylaw. Please note that waivers from this section were not needed for prior similat airport projects submitted from this office. $.3.S.avii ,VHB is recommending that the Applicant request a waiver from this suction of the Zoning Bylaw or that the design be revised. As mentioned in the drainage report,specific site restraints do not allow for a reduction in peak rates of runoff: These restraints ate high ground water,failed percolation tasting,and limited leased area, Stormwater TWO is mitigated to the greatest extent practical. The additional impervious area generated by this project is less than 1%of the total impervious area within the airport. The Applicant is providing stormwater quality treatment by installing an oil& sediment chamber to treat collected runoff before it enters t#no existing drainage system. We believe this is sufficient for this project. if the board feels a waiver is necessary, please consider this a request for a waiver of this sections of the Zoning Bylaw. .3.5.e.xvii Exterior lighting is shown on the Site Plan. We have included a lighting detail out sheet. The lights will be simple wall m6unted lights used to light the driveway in front of the hanger building. C'Mi Enalneers • Land Surveyors • Ladd Planners FROM ANDOVER CONSLUANT5,INC. PHONE NO. 978 686 5100 Jan. 24 2005 08:40AM P3 y�anQdeo�sultenta y \ Ina. If you require any additional information,please feet free to contact me. Thank you. Sincerely, ANDUVE ONSULTANTS INC. Joseph P.Burke,P.E. Senior Civil Engineer ' cc.Dale dross 71ftb P:1199-61EETTERNHEI-01 1245.doe andover D Eas ,�� consultants t R Place II O' Methuen, Massachusetts 01844 Tel. (978) 687-3B28 Fax(978) 686-6100 February 1, 2005 North Andover Planning Board North Andover Town Offices 120 Main Street North Andover, MA 01845 Regarding: Flight Craft Hanger Applicant: Dale Gross Lawrence Municipal Airport Members of the Board: On behalf of the applicant,Dale Gross, we would like to respond to the comments made in the V.H.B. memorandum addressed to Jacki Byerley dated January 31, 2005. In the memorandum V.H.B. accepts the increase in runoff for Subcatchment 1 in the drainage report dated November 18, 2004 and revised on December 20, 2005. V.H.B. did however request that the Applicant determine if the downstream wetland system can handle the increased runoff. Using a USGS map and site observation, calculations were performed to estimate the impact the additional volume of stormwater runoff would have on the downstream wetland system. The results are as follows: Existing conditions runoff volume=0.722 ac-ft Proposed conditions runoff volume= 1.061 ac-fit Increased runoff volume=0.34 ac-ft Approximate area of wetland= 10 acres Additional volume of runoff to wetland=0.50 inches The additional volume of runoff estimated above does not consider outlet flow from the wetland. There is, however; an existing stream outlet, which carries the runoff to the Merrimack River. Based on the information provided above, we believe the downstream wetland and stream system has adequate capacity to assimilate the additional runoff generated from this development. If you require any additional information, please feel free to contact me. Thank you, Sincerely, ANDO CONSULTANTS INC. Joseph P. Burke, P.E. Senior Civil Engineer cc. Dale Gross JPB1jpb P:1199-611pb-020105.doe Civil Engineers • Land Surveyors • Land Planners t CHANGEGolf � •,��'••��'��'•..�'' 1k.4 1 � � :(� � �:il ?.��AV_[Rki11=E.\ \ �� i ic ;�1,tr';`•. i/' �-� - �"/ l', ' Cl/�r /•. r' '�/�',�.��,+ ,/mac A t iw '• `�6,�� `��, 7r.0 / � � (�. eo I�� r��r ! /(/� ,9pT• � /l�/J-- �`\\.� 1., 30 OL7 .QA BM LAWRENCE I PPP Ji \� ` �! :Sege UNICIPAL AIR P° T//i `\ L _ `� �� I ► �® oS�� ' - - m� .. �� ` I � �/'� ! � ,�• J�� ,� � ��'` �r-wry �"��• rnprn _µ is r,�I �1 ~` ' sM %i'' t UJLTLAWp �<<>� � • Y'� .sumo" c � � f � `� ,� s ` Cc, � � _ � ��S , Dou I eel.; �� , ° i - �� •9 l�rl1 e -'Belli ; �� •� } ,tt Four Acr s �• ` Al Y 5uftot 16M 50. Lr __ ro onr /y�r aelsl '• ``� ---=J1 � �- �� , � �. /�y�11+�� ' � �' ` � •� ..✓� chi _ � _ O` � r '-'�—, CY�y\ ; �I -�NT RCHAN E� I .\ �_ �. / �` 'S ` -_�� _ =:� .•c 1. 34. FIGURE 1 LOCUS MAP Proposed Site Plan Lawrence Municipal Airport 492 Sutton Street cndover NORTH AND OVER, MASSACHUSETTS I� consultants inc. SCALE: 1"=2083' DATE: Feb. 20,05 1 East River Place, Methuen, Mass.