Spring Lane and Hendren StreetProposed Flood Relief ProjectNovember 12, 2013

www.phillywatersheds.org

Outline

Review of Past Problems and Project ObjectivesPWD Involvement and InitiativesWatershed and Neighborhood FindingsPWD Proposed Contributions to SolutionsHomeowner InvolvementChoices and Decision Making

Hendren Street and Spring Lane

Review of original problemStabilize the Spring Lane OutfallProtect the existing 4” force mainAddress the flooding impacts experienced by residents

Infrastructure Damage: Failed Outlet-700 Block Spring Lane

Infrastructure Damage: Failed Outlet -700 Block Spring Lane

Impaired Driver Safety: Standing Water-700 Block Spring Lane

PONDED WATER LIMITS AFTER JUNE 2013 THUNDERSTORM

Impaired Driver Safety: Sediment Deposition @ Hendren & Spring Intersection

Roadway/Lawn Interface Deterioration Eroded gutter@ Hendren & Spring Intersection

Homeowner Impacts: Erosion and Pavement Damage- 600 Block Hendren Street

PWD Involvement and Initiatives

Initiative 1: Homeowner Surveys

Quantify number of homeowners adversely affected by stormwater runoffConcurrently gather data to evaluate provision of sanitary sewer service

Initiative 2: Analysis

Determine Source(s) and destinations of problematic runoffEvaluate Potential remedies

Initiative 3: Recommendations

PWD Survey Response Summary

45 Surveys Distributed / 19 Responses (42%)15 Surveys on Spring Lane/ 7 Responses (47%)30 Surveys on Hendren / 12 Responses (40%)

PWD Survey Summary: Septic

ID Good Condition Fair Condition Poor Condition

Spring Lane 4 2 1

Hendren Street 3 5 4

Total 7 7 5

PWD- Analysis- Source of Runoff

Drainage Area to Spring Lane is approximately 25 Acres

Runoff Sources: Manatawna Avenue to Spring Lane

Runoff Sources: Hendren Street and Yards to Spring Lane

Summary of Observations:

PWD’s installation of storm sewers/inlets in Manatawna Avenue, Hendren Street and Spring Lane will provide control of stormwater from city streets and public rights-of-way, however, runoff from private property, driveways and roof tops will need to be directed and connected to this infrastructure.

Manatawna Stormwater Improvements

Inlets can be added in Manatawna to intercept this street runoffHOWEVER, this represents only a small fraction of the total land area currently contributing to Hendren and Spring flooding.

PWD Analysis: Runoff Path

YardsHendren StreetColonial Swale and YardsResidencesLow Point in Spring (Damaged Storm pipe and Headwall)

Runoff Paths: Colonial Gutter

Runoff Paths: Yards-Hendren to Spring

Runoff Paths: Streets- Spring to Field

Runoff Paths: Streets -Low Point Spring

PWD Analysis: Significant Runoff Generators

Surface Character affects the amount of runoffImpervious Surface like roofs, drives, streets and walks prohibit infiltration of stormwater. Nearly 100% RunoffPervious, Vegetated Surfaces absorb some runoff, however runoff still occurs, especially in more intense storms

Watershed Statistics: Impervious Surface

25 Acres Total Drainage Area

25% Impervious (6.3 acres)2.3 acres streets (public)4.0 acres roof tops and driveways (privately owned)

75% Pervious (18.6 acres – privately owned)

Public vs. Private Runoff Generators

Runoff from streets and public rights-of-way 2.3 Acres or 9%

Yards, roofs and driveways 18.5 acres + 4 Acres = 22.5 Acres or 91%

Sanitary Sewer Service

Existing Sanitary ChallengesOf the respondents to the survey, 62% indicated that their existing septic system was only in “fair” or “poor” condition

Sanitary Sewer Design Considerations

Spring LaneSouth side of Spring served by a standard depth gravity sewer.

A new pump station will require acquisition of additional right-of-way

Sanitary Sewer Design Considerations

Hendren StreetSouth side residents (uphill) can be served by standard depth (8-feet Separate) sewersNorth side residents (downhill) are below standard depth sewers

PWD Stormwater Remedies:

Localized Damage solution is available; Repair damage at Spring Lane outfall

Interim: Armor and reinforce

Typical Repair of Damaged Outfall

PWD Stormwater Remedies:

Construction of a Storm Sewer pipe and inlet system in public rights of way is possible

Will provide for safe conveyance of captured runoff

Will fortify repair of damaged Spring Lane outfall and protect forcemain

Actions Required beyond PWD’s Proposed Stormwater Remedies:

Doesn’t Solve the Entire ProblemRequires that private property runoff be redirected to intercept 100% of runoffWill not resolve homeowner flooding emanating from private property runoff

Stormwater: Increase Effective Runoff Collection – Connect All Roofs to Proposed Main

Stormwater: Increase Effective Runoff Collection – Connect All Roofs to Proposed Main

PWD Sanitary Sewer Remedies:

Construction of Sanitary Sewer and Pump station is possible

Will provide alternative to replacement of failing septic systemsRequires additional efforts to provide service to entire neighborhood

Downslope properties that have plumbing discharge below street level may need to install ejector/grinder pumps

Choices Related to PWD Action

Construction Impacts

Financial and Action Commitment

Choices Related to PWD Action

Construction ImpactsPotential roadway changes

WideningADA WalksCurbs or swalesDriveway crossings

Tree, Shrubbery and Fence Removal Probable

Construction Choices Related to PWD Action: Fence POTENTIALLY at Risk

Construction Choices Related to PWD Action: Fence POTENTIALLY at Risk

Construction Choices Related to PWD Action: Trees POTENTIALLY at Risk

Construction Choices Related to PWD Action: Shrubbery POTENTIALLY at Risk

Construction Choices Related to PWD Action: Shrubbery and Specimen Tree at Risk

Consequences of PWD Action:Shrubbery and Specimen Tree at Risk

ALTERNATIVE APPROACH

Reduced extent of curbing and street wideningIntercept Runoff with Roadside Swales in-lieu of Curbing

Retain Neighborhood CharacterProvides Infiltration

Reduces Runoff VolumeImproves Water Quality

Alternative Approach: Hendren Street Section @ Regulated Width

Alternative Approach: Hendren Street

Section - Retained Narrow Width- No Curb

Choices Related to PWD Action:Financial and Action Commitment

PWD Responsibility Homeowner Responsibility3540 feet of Storm Water Main: Construct, Own & Maintain

3293 feet stormwater laterals and appurtenances from downspouts to edge of street: Construct, Own & Maintain

462 feet stormwater laterals to edge of street: Construct only. (will be owned and maintained by homeowner)

Decommission septic system

3075 feet of Sanitary Sewer Main: Construct, Own & Maintain. 453 feet sanitary laterals to edge of street: Construct only. (will be owned and maintained by homeowner)

3806 feet sanitary laterals and appurtenances from house to edge of street including : Construct, Own & Maintain

Pump station and + 700 Feet of Forcemain: Construct, Own & Maintain

Grinder Pump (if required): Construct, Own & Maintain

Inlets: Construct, Own & MaintainSwales: Construct, Own & Maintain

Pay Assessment fee: $9.00/lineal foot of frontage

Driveway restoration in area of disturbance only Pay monthly service fee

Remove vegetation within construction limits*

Acquire permits and approvals for construction within the public rights-of-way, Only

Acquire permits and approvals for construction within homeowner property limits

* Landscaping outside the right of way that is affected by construction will be replaced with young nursery stock of similar species. Landscape replacement within the right of way will be replaced depending on the situation. Utility, safety and maintenance issues will be evaluated.

Steps to Obtain Public Sewers

Residents signed petition to PWD or their CouncilpersonCity Council Ordinance is required for a public sewerProcess from Ordinance to construction can take a few years

Impact to Customers

Each property owner is assessed at the rate of $9.00 per linear foot of property frontage Plumbing which drains to the back of the house needs to be redirected to the front of the house (PWD has zero interest loans available)Yard drains, downspouts should be connected to new stormsewer via new stormwater lateral (PWD has zero interest loans available)

Benefits of PWD Actions

Reduced runoff from street and connected roofs…reduced property damageImproved Driver Safety-Reduced standing waterElimination of maintenance associated with on-lot septic systemAlternative to replacement of expensive on-lot septic systemImproved marketability of property

Homeowner Solution Choices

PWD Installation of Stormwater and Sanitary Sewer conveyance System?

…or

Limit PWD’s actions to Repair of Damaged Spring Lane outfall?

Other?