Flash Flooding ❑ Impervious Cover & Zoning Decisions ❑ Proposal – Wingohocking Overlay District
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Why does E Mt Airy have so many “Road May Flood” signs? ❑ Wingohocking Watershed ❑ Flash Flooding ❑ Impervious Cover & Zoning Decisions ❑ Proposal – Wingohocking Overlay District Kelly O’Day, PE Retired BS Civil Engineering MS Environmental Engineering Mt Airy Watersheds Wissahickon Tookany – Tacony – Frankford (TTF) Gowen Source: 1843 Map of Philadelphia County - Charles Ellet, Jr Wingohocking What happened to Source: Philadelphia Water Dept. Wingohocking Creek? http://phillyh2o.org Wingohocking Creek Encased In Combined Sewer ❑ Early residents built private sewers to carry their raw sewage to Wingohocking Creek tributaries ❑ Raw sewage created local odor & potential health problems ❑ City viewed burying Wingohocking Creek as way to solve potential health hazards ❑ Burying Creek started in Germantown in 1880s, full creek burial completed in 1928 ❑ Progressed upstream and downstream as development increased ❑ Wingohocking Creek was encased in a combined sewer ❑ Carried original creek flow, residential sewage, stormwater runoff ❑ In 1928 discharged to Frankford Creek ❑ Later carried to treatment plant and then to Wingohocking Creek Combined Sewer under construction, 1909 the Delaware River. Wingohocking Sewer Outfall Frankford Creek – Juniata Park Wingohocking Creek Tacony Creek Frankford Creek Tacony Creek Drainage Areas Drains to Tacony Creek By Roosevelt Blvd Historic Wingohocking Drains to Frankford Creek By Juniata Park Hydraulic Capacity and Flooding Natural Rivers versus Combined Sewers ❑ Flooding occurs when upstream flows greater than downstream capacity ❑ Natural streams and rivers have flood plains that hold flood waters during extreme flow events 1. Natural Watershed Burying Wingohocking Changed Watershed Land Use Development & Flood Plain 2. Buried Wingohocking Creek 5. Continued Development, Impervious Cover Germantown Ave Stenton Ave 3. Built streets 4. Built houses 1. Encased Creek in Sewer 2. Filled Creek Channel Up to 48-feet ❑No visible creek ❑Development close to combined sewer ❑Developed area floods when combined sewer capacity exceeded ❑Flooding risk – not identified on FEMA maps Hydraulic Capacity and Flooding Natural Rivers versus Combined Sewers ❑ Flooding occurs when upstream flows greater than downstream capacity ❑ Natural streams and rivers have flood plains that hold flood waters during extreme flow events ❑ Combined sewers are rigid pipelines with fixed capacity, they do not have flood plains to hold flood waters during extreme flow events. Excess stormwater flow: o Overflows manholes o Backs up into plumbing systems o Inundates streets/ sidewalks o Floods adjacent houses/ businesses o Damages pipe, can lead to pipeline failure Belfield Ave & Haines Street Buried Wingohocking Sewer Under Belfield Ave. East Mt Airy Runoff and Deadly East Germantown Flash Flood Thursday, Sept. 8, 2011 “Pastor Todd Dunbar, who heads Praise, Power and Deliverance Church, was left looking for a place to house his congregation after more than six feet of water rushed through the building.” WHYY NewsWorks, 9/10/11 High Flood Water Line City Recognizes Wingohocking Flash Flooding Wingohocking Watershed RCOs Roles in Addressing Flash Flooding 1. Stormwater Regulations Review 2. Zoning Variance Review: address stormwater – flash flooding aspects of projects 3. Support Creation of Historic Wingohocking Overlay District along lines of Wissahickon Overlay District 4. Support PWD’s Germantown Storm Flash Relief Capital Improvement Plan 1. Stormwater Regulations Review The PWD Stormwater Regulations require on-site stormwater management for development projects that disturb 15,000 square feet (5,000 in certain watersheds) of earth disturbance. ❑ City-wide: projects > 15,000 square feet ▪ Water Quality – manage the first 1 inch ▪ Channel Protection – infiltrate or slow release 1-year, 24-hour storm (2.6 inches) ▪ Flood control – peak rate control of post to pre-development conditions ❑ Cobbs & Darby Creeks: projects > 5,000 square feet, Pa Act 167 Stormwater Management Plan ❑ Wissahickon: Overlay District Historic Wingohocking Watershed needs flooding protections Like those provided by Wissahickon Overlay District 2. Zoning Variance Review & Flash Flooding in Wingohocking Watershed Wingohocking Stormwater – Flash Flooding Education ❑ Zoning Committee ❑ Residents ❑ Developers 6. Increase danger of flooding? Flood Prone Wingohocking Zoning Review Questions Submitted to City Officials - 4/1/19 1. When in the City’s zoning review process does PWD review proposed site stormwater control plans for a site with disturbance greater than 15,000 square feet? Does this apply to both “by right” and “by variance” projects? 2. Can an RCO, neighbor or citizen raise flooding concerns about a proposed project less than 15,000 square feet on sites upstream of flash flood prone areas in Wingohocking Sewershed? If yes, when in the process and who should be contacted? 3. Can an RCO request the Water Department to prepare a hydraulic assessment/ flash flood assessment for a proposed project in the Wingohocking Sewershed prior to the RCO public meeting for a ZBA variance application? 4. Can developers voluntarily submit site plans for stormwater reviews for projects less than 15,000 square feet for sites upstream of flash flood prone areas in Wingohocking Sewershed? If yes, who should be contacted? 5. Are PWD stormwater regulation plan reviews in the Wingohocking Sewershed available for public review? 6. How does L&I, the Planning Commission and Water Department review the Variance Appeal question 6, “will the variance you seek …. increase the danger of flooding?” question? Is there any independent assessment of the accuracy of the applicant’s response? 7. The Planning Commission representative at the ZBA hearing is specifically asked if the Planning Commission has any comments on the variance application before the Board votes. Does Planning Commission staff, Flood Task Force or PWD staff advise the Planning Commission representative about any potential flooding issues of the variance application in the Wingohocking Sewershed prior to the ZBA hearing? 3. Support Historic Wingohocking Overlay District Wissahickon Overlay Provides Prototype Wissahickon Watershed Overlay (WWO) ❑ To help reduce flooding, erosion, siltation, and channel enlargement, additional stormwater management requirements and impervious coverage limits may apply to projects in Wissahickon watershed. ❑ Requirements depend on the location and amount of impervious cover proposed ❑ In the WWO District: ▪ Planning Commission determines if additional stormwater management requirements are applicable ▪ Depending on location, lot size, and change in impervious area, PCPC may restrict new impervious cover, or impose additional stormwater management requirements beyond PWD’s Stormwater Regulations ▪ PCPC does not use an earth disturbance threshold when determining whether stormwater management is required. Therefore, it is possible for development projects to trigger Stormwater Management Requirements under the WWO without triggering the Stormwater Regulations. ▪ Water Department reviews the Stormwater Management Plan Historic Wingohocking Watershed needs a Flash Flooding Overlay District 4. Support PWD’s Germantown Storm Flood Relief Capital Improvement Plan Germantown Storm Flood Relief Capital Improvement Plan PWD Long Term solution Likely Actions ❑ Reduce impervious cover ❑ Retain more stormwater in watershed ❑ Address high risk properties ❑ Increase hydraulic capacity ❑ RFP issued Nov., 2015 ❑ Draft Report – Nov., 2018 ❑ Report – Summer, 2019 How Can E Mt Airy Residents Help Reduce Wingohocking Flooding Risk? ❑ Understand that EMA runoff affects downstream EMA & E Germantown ❑ Reduce Impervious Cover to Reduce Stormwater Runoff & Flash Flood Risk o Rain Barrels, Rain Gardens o Redirect roof runoff to yard o Reduce impervious cover ❑ Review proposed land use changes for stormwater . Flash Flood impacts ❑ Encourage EMA BID, EMAN, Mt Airy USA to initiate/ expand/ support stormwater reduction programs ❑ Support Historic Wingohocking Zoning Overlay Now that we know why E Mt Airy has so many “Road May Flood” signs, it’s time to Act! Special Thanks WHYY NewsWorks– E Germantown Flooding Articles PWD - Wingohocking Combined Sewer Constructions Photos Adam Levine – PhillyH2O blog: Historical information on Wingohocking Creek OpenDataPhilly – incredible Philadelphia data resources available on-line.