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HomeMy WebLinkAboutStormwater Report - 21 CLARK STREET 10/14/1987 Drainage Study prepared for Positive Start Realty J.J.B. Associates, Inc. 145 Marston 6treet, Lawrence October 14, 1987 SUMMARY The existing drainage from this 2.66 acre site flows overland in an easterly direction with sheet flow onto the Lawrence Airport property to the brook and ul- timately to the Merrimack River. The predevelopment flows were calculated for 25, 50, and 100 year storm events with a peak flow in a 100 year storm of 7 cfs. The postdevelopment flows were also calculated for a 25, 50, and 100 year storm with a peak flow in a 100 year storm of 9 cfs, or an increase of 2 cfs. In order to provide a zero increase in the rate of runoff, a small retention area (9,000 cubic feet) will be constructed in the northeasterly corner of the property. S y TR-55 Tc and Tt THRU SUBAREA COMPUTATION VERSION 1. 11 Project Positive Start Realty User: JJB Date: 10-02-87 County : No. Andover Essex State: Ma Checked: Date: Subtitle: Predevelopment ------------------------------------------------------------------------------- Flow , Type 2 year Length Slope Surface n Area Wp Velocity Time rain (ft) (ft/ft) code (sq/ft) (ft) (ft/sec) (hr) ------------------------------------------------------------------------------- Sheet 3. 0 200 0. 01 e 0. 367 Shallow Concent 'd 100 0. 01 u 0. 017 Time of Concentration = 0, 38* Shallow Concent 'd 200 0. 01 u 0. 034 Travel Time = 0. 03* --- Sheet Flow Surface Codes --- A Smooth Surface F Grass , Dense --- Shallow Concentrated --- ,. Fallow (No Res. ) G Grass , Burmuda --- Surface Codes --- 'Cultivated < 20 % Res. H Woods , Light P Paved p Cultivated > 20 % Res. I Woods , Dense U Unpaved Grass-Range, Short * Generated for use by GRAPHIC method TR-55 GRAPHICAL DISCHARGE METHOD VERSION 1. 11 Project Positive Start Realty User: JJB Date: 10-02--87 county No. Andover Essex State: Ma Checked: Date: oubtitle: Predevelopment Data: Drainage Area 2. 66 Acres Runoff Curve Number 75 Time of Concentration: 0. 38 * Hours Rainfall Type III Pond and Swamp Area NONE --------------------------------------------- --------------------------------------------- Storm Number 1 2 3 ' ---------------------- ' ------ ' ------ ' ------ ' Frequency (yrs) ; 25 50 ; 100 24-Hr Rainfall (in) 5. 5 6. 0 6. 6 Ia/P Ratio ; 0. 12 ; 0. 11 0. 10 Runoff (in) ; 2. 86 3. 28 3. 80 Unit Peak Discharge ; 0. 704 10. 710 10. 715 (cfs/acre/in) Pond and Swamp Factor ; 1. 00 ; 1. 00 ; 1. 00 0. 0% Ponds Used ' ----------- ---- ' ---- - ' ------ ' Peak Discharge (cfs) ; 5 ; 6 7 - Value (s) provided from TR-55 system routines TR-55 CURVE NUMBER COMPUTATION VERSION 1. 11 Project Positive Start Realty User: JJB Date: 10-02-87 _'ounty No. Andover Essex State: Ma Checked: Date: _ Subtitle: Postdevelopment Subarea Post ------------------------------------------------------------------------------- Hydrologic Soil Group COVER DESCRIPTION A B C D Acres (CN) ------------------------------------------------------------------------------- FULLY DEVELOPED URBAN AREAS (Veg Estab. ) Open space (Lawns ,parks etc. ) Good condition; grass cover > 75% - 0. 92 (61) - - Impervious Areas Paved parking lots , roofs , driveways 1. 74 (98) - - - Total Area (by Hydrologic Soil Group) 1. 74 . 92 SUBAREA: Post TOTAL DRAINAGE AREA: 2. 66 Acres WEIGHTED CURVE NUMBER: 85* -------------------------------------------------------------------------------- * -, generated for use by GRAPHIC method TR-55 To and Tt THRU SUBAREA COMPUTATION VERSION 1. 11 Project : Positive Start Realty User: JJB Date: 10-02-87 ?ounty : No. Andover Essex State: Ma Checked: Date: _ Subtitle: Postdevelopment --------------------------------------------------------- ---------------------- - Flow Type 2 year Length Slope Surface n Area Wp Velocity Time rain (ft) (ft/ft) code (sq/f-t) (ft) (ft/sec) (hr) ------------------------------------------------------------------------------- Sheet 3 . 0 200 0. 01 e 0. 367 Shallow Concent'd 100 0. 01 u 0. 017 Time of Concentration = 0. 38* Shallow Concent'd 200 0. 01 u 0. 034 Travel Time = 0. 03* --- Sheet Flow Surface Codes --- A Smooth Surface F Grass , Dense --- Shallow Concentrated --- B Fallow (No Res. ) G Grass , Burmuda --- Surface Codes --- C Cultivated < 20 % Res. H Woods , Light P Paved D Cultivated > 20 % Res. I Woods , Dense U Unpaved E Grass-Range, Short * - Generated for use by GRAPHIC method TR-55 GRAPHICAL DISCHARGE METHOD VERSION 1. 11. Project Positive Start Realty User: JJB Date: 10-02-87 County No. Andover Essex State: Ma Checked: Date: Subtitle: Postdevelopment Data: Drainage Area 2. 66 Acres Runoff Curve Number 85 Time of Concentration: 0. 38 * Hours Rainfall Type III Pond and Swamp Area NONE Storm Number 1 i 2 3 ' ---------------------- ' ----- - ' ------ ' ------ ' Frequency (yrs) 25 50 ; 100 24-Hr Rainfall (in) 5. 5 ; 6. 0 6. 6 Ia/P Ratio 0. 06 0. 06 ; 0. 05 Used ; 0. 10 0. 10 ; 0. 10 Runoff (in) ; 3. 83 ; 4. 30 ; 4. 87 Unit Peak Discharge 10. 716 10. 716 10. 716 (cfs/acre/in) Pond and Swamp Factor ! 1. 00 ; 1. 00 1. 00 0. 0% Ponds Used ' ---------------------- ' ------ ' ------ ' ------ ' Peak Discharge (cfs) 7 ; 8 9 * - Value (s) provided from TR-55 system routines TR-55 STORAGE VOLUME FOR DETENTION BASINS VERSION 1 . 11 "roject : Positive Start Realty User: JJB Date : 10-02-87 lounty : No. Andover Essex State: Ma Checked : __ ..... Date: .................... ____ 5ubtitle: Postdevelopment Drainage Area: 2.66 Acres Rainfall Frequency: 25 years Rainfall-Type: III Runoff : 3.8 inches Peak Inflow: 7.296413 cfs Detention Basin Storage Volume: .2 acre-feet Peak Outflow: 4 cfs | | � ` � ��. TR-55 STORAGE VOLUME FOR DETENTION BASINS VERSION 1 . 11 "roject : Positive Start Realty User: JJB Date: 10-02-87 / lountv : No. Andover Essex State: Ma Checked : Date: . � Subtitle: Postdevelopment � Drainage Area: 2.66 Acres Rainfall Frequency: 50 years Rainfall-Type: III � Runoff : 4.3 inches � Peak Inflow: 8. 190363 cfs � Detention Basin Storage Volumes .2 acre-feet � =- ak Outflow: 6 cfs . � � � , TR-55 STORAGE VOLUME FOR DETENTION BASINS VERSION 1 . 11 oroject : Positive Start Realty User: AB Date: 10-02-87 lounty : No. Andover Essex State: Ma Checked : Date: 5ubtitle: Postdevelopment Drainage Area: 2.66 Acres Rainfall Frequency: 100 years Rainfall-Type: III Runoff : 4.9 inches Peak Inflow: 9.272634 cfs Detention Basin Storage Volume: .2 acre-feet Peak Outflow: 7 cfs � � ` s , , N � - • ■■ -_ ► � \ ,Ili KI �� \►\\all I I ■��.. oil ■■� 1 \, 1'611 ■ .�aw>