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HomeMy WebLinkAbout1977-04-22 Drainage Study WITHDRAWN aFF�c COPY DRAINAGE STUDY DOUGLAS DRIVE SUBDIVISION e s 4-- 6 North Andover, Massachusetts r i � October 1977 l ; + i E ���drx�TT d io/•7/7' I DRAINAGE STUDY DOUGLAS DRIVE SUBDIVISION NORTH ANDOVER, MASSACHUSETTS A H c ' L TC Y OCTOBER, 1977 M. Anthony Lally Associates Consulting Environmental Engineers North Andover, Massachusetts 01845 M. Anthony Lally Associates Consulting Enuironmental Engineers M. Anthony Lally, P.E. 200 Sutton Street North Andover, Massachusetts 01845 Tel. (617) 688.1763 October 17, 1977 Mr. Douglas Wilson 130 Lisa Lane North Andover, MA 01845 Re : Drainage Study Douglas Drive Subdivision North Andover, Massachusetts Dear Mr. Wilson: In accordance with our agreement, we are pleased to present, herewith, our report on the drainage study for the referenced project. We recommend an equalization system to compensate for any increased run-- off as a result of the proposed subdivision. Also, replacement of the stone drain on Rea Street in cooperation with the Town will improve overall, drainage characteristics . Please do not hesitate to contact this office if you have any questions regarding this matter. MAL/saw Very truly yours, Enclosure M. ANTHONY LALLY ASSOCIATES Consulting Environmental Engingers G M. thon ally, E. Water • Wastewater • Solid Waste Site Development i TABLE OF CONTENTS Title Page Letter of Transmittal Table of Contents i List of Tables i INTRODUCTION 1 PHASE I Existing Runoff 1 Future Runoff After Development 2 PHASE II 5 DESCRIPTION OF PROPOSED CONTROL FACILITIES 8 APPENDIX Sub-drainage Area IIB - Storm Hydrographs & Storage Requirements LIST OF TABLES Table No. Title Page No. 1. Runoff Rate for Area I Without Control 3 2 . Runoff Rate for Area II Without Control 4 3 . Summary of Discharge Rates With Control System 7 4 . Required Storage Volume and Discharge Control 10 Rates INTRODUCTION The purpose of this drainage study is to determine the impact of a proposed ten lot subdivision off Lisa Lane in North Andover on run- off rates to abutting land areas . The study consists of two phases . It is first necessary to determine existing runoff rates and the effect of development of the proposed Douglas Drive Subdivision on these rates . The second part includes the determination of the im- pact if excess runoff were diverted to the existing stream through abutting properties . Phase II would be provided only if calculations under Phase I indicated an increase in the overall rate of runoff due to the proposed land development. Recommendations to control the runoff also are included in Phase II. The proposed Douglas Drive Subdivision is located off Lisa Lane in North Andover and consists of approximately six (6) acres of land made up of ten lots , each slightly larger than one-half (1/2) acre in size. The total area of land included in the subdivision consists of about 19 acres and is divided into two (2) subdrainage areas which generally extend from Mills Hill toward Rea Street and Jay Road as shown on the attached plan. PHASE I Existing Runoff Existing runoff from Drainage Area II drains toward the brook crossing Rea Street about 1 , 000 feet west of Jay Road across land owned by Mr. Gilbert Rea. Area II consists of about 15. 2 acres . Drainage Area I consists of about 11 acres and drains toward the stream near the end of Jay Road which also crosses under Rea Street. Existing runoff rates for Areas I and II have been determined for 5, 10 , 25 , and .50 year storms using the SCS Modified Soil Cover Complex Method based on the topography of the land, drainage area, soil characteristics , and existing vegetation. This method is used to pro- vide a basic method of estimating peak discharge rates for relatively small drainage areas. -1- Drainage Area I ranges from an elevation of about 260 to approximately elevation 405 , and Drainage Area II ranges from about elevation 277 to elevation 405. The average slope for both of the main drainage areas is approximately nine (9) percent based on the U.S .G.S . topo- graphic map for the area. Soil conditions have been determined .from the U. S . Department of Agriculture, Soil Conservation Service (SCS) report "Soils and Their Interpretations for Various Land Uses" June, 1971 for the Town of North Andover . Based on their relatively slow infiltration and transmission rates , the soils have been classified under Hydrologic Soil Group C. Values of precipitation were obtained from the U. S . Weather Bureau Rainfall Data Maps for 5 , 10 , 25 , and 50 year storms. In order to aid in the determination of existing runoff rates and the potential drainage impacts from the proposed development of the sub- division, Drainage Areas I and II were broken down into Sub-areas A, B, and C as indicated on the attached plan. The existing runoff rates for these areas are presented in Table Nos . 1 and 2 , RUNOFF RATES FOR AREA I (AREA II) WITHOUT CONTROL. Future Runoff After Development Generally, development of a wooded area results in increased runoff rates due to the stripping of existing vegetation and construction of roads, pavement, etc. on the land. Adjustments must be made to the runoff rates to consider the extent of future vegetative cover, residential lot size, proposed drainage systems, runoff from roof tops , driveways, etc. to determine future runoff from the proposed Douglas Drive Subdivision. The total runoff rates from-Areas I and II have been determined for the proposed subdivision for 5 , 10 , 25 , and 50 year storms assuming all of the lots were residentially developed. Tables 1 and 2 present the runoff rates resulting from the development of the subdivision. The tables show that the total runoff from Area I toward Jay Road would be decreased as a result of diverting flow from Sub--area IC to Sub--areallB by the construction of Douglas Drive. Future runoff toward Rea Street -2- TABLE NO. 1 RUNOFF RATES FOR AREA I WITHOUT CONTROL Runoff Rates (Cubic Feet/Second) Prior to After Development beyelo'pment I - Total Area 11 acres 9 acres 5-yr. storm 16 . 5 16 . 0 10-yr. storm 21. 4 20. 6 25-yr. storm 29 .4 27. 2 50-yr. storm 35 . 2 29. 4 IA , - (Not to be Developed) 6 acres 6 acres 5-yr. storm 8. 9 No- Change 10-yr. storm 12 . 5 No Change 25-yr . storm 16 . 0 No Change 50-yr. storm 20 . 5 No Change IB - 3 acres 3 acres 5-yr . storm 4 . 5 6 . 9 10-yr. storm 6 . 4 9 . 1 25-yr . storm 8 . 0 11. 2 50-yr. storm 9 . 6 12. 8 IC - 2 acres 2 acres 5-yr. storm 3 . 0 3. 7* 10-yr. storm 4 .3 5 . 0* 25-yr. storm 5. 3 6 . 4* 50-yr. storm 6. 4 7. 5* IB and C 5 acres 3 acres 5-yr. storm 7. 6 6.9** 10-yr . storm 10 . 7 9 . 1** 25-yr. storm 14 . 2 11. 2** 50-yr. storm 16 . 0 12 . 8** *Flow from Area IC to be diverted to Swale by Douglas Drive after roadway construction. **Flow from Area IB; IC to be diverted by Douglas Drive. -3- TABLE NO. 2 RUNOFF RATES FOR AREA 11 WITHOUT CONTROL Runoff Rates' (Cubic Feet/Second) Prior to After. Area Development Development II - Total Area 15 . 2 acres 17 . 2 acres 5-yr. storm 21. 4 28. 4* 10-yr. storm 28 . 5 37 . 0* 25-yr . storm 38 . 3 48. 2* 50-yr. storm 48 . 1 57 . 7* IIA - (.Not to be developed) 7 . 2 acres 7 . 2 acres 5-yr. storm 10. 7 No Change 10-yr. . storm 14 . 7 No Change 25-yr. storm 19 . 6 No Change 50-yr . storm 23 . 1 No Change IIB 8 . 0 acres 10 . 0 acres* 5-yr. storm 12 . 0 20 . 7 10-yr. storm 16. 0 26 . 5 25-yr. storm 21 . 4 33 . 2 50--yr. storm 26 . 3 39. 7 *Includes flow from 2 acre area IC .which will be diverted to swale by Douglas Drive (See Table- No. 1) and flow of lcfs from new catch basin at Lisa Lane. -4- would be increased substantially, not only due to development of Sub-area IIB, but also since runoff from Sub-area IC has been diverted towards Rea Street by Douglas Drive as ,shown on the plan. Table Nos. 1 and 2 show that for a 5-year storm, the existing runoff rates from Area I and Area II are approximately 16 . 5 and 21 . 4 cfs, respectively. The future runoff rates after development for the 5-year storm for Area I is estimated to be about 16 . 0 cfs and for Area 11 is about 28 . 4 cfs. For a 10-year storm, the existing runoff from Area I is 21. 4 cfs while after development the runoff is 20. 6 cfs. Existing runoff from Area 11 for the 10-year storm is 28. 5 cfs and after develop- ment is 37 . 0 cfs . For a 25--year storm, existing runoff rates from Area I and Area II are 29 .4 cfs and 38. 3 cfs while the future rates after development are 27. 2 and 48. 2 cfs , respectively. For a 50-year storm, existing runoff from Area Z is. 35...2. cis.; future: runoff after development is about 29 .4 cfs . Existing runoff from Area II for the 50--year storm is about 48. 1 cfs , and future runoff is estimated to be about 57 . 7 cfs . Runoff rates prior to and after development for each of the Sub-areas are also presented in Table Nos . 1 and 2. PHASE II In order to minimize potential adverse impacts on abutting property due to increased drainage from the proposed development, and to main- tain or reduce the existing flow in the stream near Jay Road, -the construction of a drainage swale is recommended at the back of the lower lots off Douglas Drive as shown on the plan.. The swale is intended to intercept runoff from the developed area draining towards Jay Road and Rea Street as well as to collect the street drainage from Douglas Drive. A discharge structure would be constructed at the end of the swale in order to control the flow to the stream across Mr. Rea ' s land and to maintain it at or below the existing flow rate in this direction. Also, a control outlet would be provided in Area I towards Jay Road to maintain or reduce: the flow in the stream at the end of ,lay Road. The total runoff rate after development from Sub-area IIB, which will flow into the swale, is estimated to be 20 . 7 , 26 . 5 , 33. 2, and 39 . 7 cfs respectively for a 5 , 10 , 25 , and 50 year storm frequency. This in- -5- eludes additional flow from the proposed catch basin at Lisa Lane as well as flow diverted from Sub-area IC by Douglas Drive. A new catch basin is proposed as requied by the Highway Surveyor, at the south-westerly corner of the proposed intersection of Douglas . Drive and Lisa Lane. This catch basin is expected to add about 1 cfs of flow to the Douglas Drive drainage system and has been included in the drainage flow studies . The existing runoff rate 'from' Sub-area TIB for a 5, 10 , 25 , and 50 year storm is estimated to be 12. 01 16 . 0 , 21. 4 , and 26. 3 cfs respectively. This indicates that future runoff rates after development from this Sub-area are greater than the existing rates from the area. Therefore, the outlet control structure of the swale shall be designed to maintain a flow rate equal to or less than the existing runoff rate : 12 . 0 cfs during a 5 year storm, 16 . 0 cfs during a 10 year storm, 21. 0 cfs during a 25 - year storm and 26. 0 cfs during a 50 year storm. Additional flow into the swale shall be stored during storm events which exceed control discharge rates . Discharge rates from the Swale control structure are presented in Table No. 3 , SUMMARY OF DISCHARGE RATES WITH CONTROL SYSTEM. These rates shall be maintained so that the total flow rate from Area II entering the stream on the abutting property shall not exceed the rates which presently exist. The existing runoff from Sub-areas IB and C is 7 . 6 , 10 . 7 , 14. 2 , and 16. 0 cfs respectively for a 5 , 10 , 25 , and 50 year storm. After develop- ment, flow from Sub-area IC is diverted to Sub-area IIB. Future runoff, therefore, is estimated to be 6. 9 , 9 . 1, 11. 2 , and 12 . 8 cfs , respectively for a 5, 10 , 25, and 50 year storm. The outlet control structure for Area I shall be designed to maintain the rates as shown in Table No. 3 so that future runoff towards Jay Road is less than the existing runoff rates in that direction. The Swale shall be constructed with a slope to drain so that excess runoff stored in the Swale during a storm period will be completely discharged towards the existing streams after a storm event has ended. The storage of water for an extended period of time could create a potential nuisance as well as a possible mosquito breeding area. This -6- TABLE NO . 3 SUMMARY OF DISCHARGE RATES WITH CONTROL SYSTEM (Cubic Feet Per Second) Area I Total IA IB + IC IC Storm Frequency Present Future Present Future Present Future (1) Present Future 5-year storm 16 . 5 16 . 0 8.9 8. 9 7 .6 6.9 3. 0 (1) 10-year storm 21.4 20 . 6. 12.5 12. 5 10.7 9 .1 4 .3 (1) 25-year storm 29 .4 27 . 2 16 .0 16 . 0 14 . 2 11. 2 5..3 . (1) 50-year storm 35 . 6 29 . 4 20. 5 20 . 5 16. 5 12. 8 (2) 6. 4 (1) (1) IC Diverted to Swale by Douglas Drive (2) Control Rate Not to Exceed Area II Total IIA IIB Storm Frequency Present Future Present Future Present (3) Future (4) 5--year storm 21.4 21. 4 10 .7 10 . 7 12. 0 20 .7 (3.7 From IC) i 10-year storm 28 .5 28.5 14. 7 14.7 16. 0 26. 5 (5. 0 From IC) 25-year storm 38 .3 38 . 3 19 .6 19 . 6 21.4 33. 2 (6.4 From IC) 50-year storm 48 . 1 48 .1 23 . 1 23.1 26. 3 39 . 7 (7.5 From IC) (3) Variable Control Rate (4) Includes diverted flow from IC and Additional Flow of 1 cfs from new Catch Basin at Lisa Lane , ...... ......... - -- --- - ..... _..__.. drainage control system would be dry most of the time , only being activated during storm events which exceed control discharge rates . DESCRIPTION OF PROPOSED CONTROL FACILITIES As indicated in Table Nos . 1 and 2 , there would be a net increase in runoff in specific subdrainage areas as a result of the proposed development. It Is necessary that flow equalization be provided. The net effect of development on Drainage Area I is negligible as the con- struction of Douglas Drive will intercept runoff from Sub-area IC and direct it to the closed drainage system and into Drainage Area II . A small reduction in flow rate has been determined for Area I as a result of the indicated developments . It is intended that a drainage control system would be provided to equalize the calculated flow increases for Area II and also to attempt to reduce the flow to Area I. The developed area down-stream of the indicated Drainage Area I has been experiencing drainage problems due to previous development. By providing drainage control in conjunction with proposed development, it is anticipated that some improvement will result in the current overall drainage situation. A drainage swale approximately 20 feet wide and 600 feet long with an average water depth during a storm event of about 2 feet is proposed. This drainage Swale would be designed with an outlet control con- figuration which would regulate the flow to maintain the rate flow at or below existing conditions . This Swale would receive drainage flow from the required closed street drains and also would intercept overland flow from both Areas I and II . The discharge rate to Area I would be controlled not to exceed 12 . 8 cfs which is about 3. 2 cfs below the calculated present discharge rates . A net decrease in flow rate of 5 . 8 cfs has been calculated for the entire Area I, for a 50-year storm, which is due to the diversion and equal- ization of flow from IC. The flow from Sub-area IIB will be discharged into the proposed swale where a variable discharge rate would control the flow to maintain it at the calculated rates as indicated in Table No. 3 , SUMMARY OF DISCHARGE RATES WITH CONTROL SYSTEM. It is also pro- posed that an existing stone culvert located approximately 1,000 feet west of Jay Road under Rea Street would be replaced in 1 cooperation with the Town. The proposed drainage Swale would be designed with 25% extra capacity to allow for vegetation and other deposits. The Swale is proposed to be free draining and therefore would be dry except for temporary retainage of flow when the discharge rate exceeds the control structure design capacity. A requirement will be attached to each lot sold that erosion control by placing baled hay at the downstream edge of each lot below Douglas Drive will be necessary during construction until surface stabilization has occurred. This system is considered desirable from both maintenance and aesthetic factors. It is agreed that maintenance if the Swale, if necessary, would be provided by the present land owner who would retain owner- ship of land on which the swale is to be located. An easement to the drainage swale will be granted to the Town for access and maintenance purposes from the present land owners after completion of the sub- division and at such time as the Town desires. The final design of the proposed Swale would be based on existing contour elevations to make it as compatable with the natural topography as possible. Discharge control would be provided by naturally contoured embankments with riprapped discharge areas for flow- Aispersion and energy dissipation. Therefore, discharge from the proposed control systems is intended to provide overland sheet flow and not to create drainage gullies to abutting land" areas .' _9- Table No. 4, REQUIRED STORAGE VOLUMES AND DISCHARGE CONTROL RATES presents the design requirements for the proposed drainage control system. TABLE NO* 4 REQUIRED STORAGE VOLUMES AND DISCHARGE CONTROL RATES Storm Re 'uired Storage Control Rate Frequency (Cu.Ft. ) (c,fs) Area I Area II 5--yr. storm 13 ,050. 0 6. 9 12 . 0 10-yr. storm 11,580. 0 9 . 1 16.0 25-yr. storm 12 ,150 . 0 11. 2 21. 0 50-yr . storm 13 ,950 . 0 12 . 8 26 . 0 *Including 25% increase allowance for. sediment and debris accumulation. The proposed development including the indicated drainage control system is considered to have no adverse impact on existing runoff rate and should improve, to some extent, the overall situation by reducing flow rates within the study area. -10- APPENDIX SUB-DRAINAGE AREA IIB -- STORM HYDROGRAPHS & STORAGE REQUIREMENTS 7%naE 70 A� a9 as' "W/ . 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