stormwater basin rehabilitation: a unique...

Stormwater Basin Rehabilitation:

A Unique CollaborationBenton G. Webber, PE

Township Engineer

Lancaster Township

Devin Groff

Township Roadmaster

Bill Laudien

Township Manager

Welcome to Lancaster Township

• Formed in 1729, the Township is roughly six square miles in area with a population of roughly 17,000 and nearly 55 miles of roads.

• Creation of Lancaster City (2miles x 2 miles) and various other annexations leaves the Township with nine (9) noncontiguous areas.

• Centuries of community building that only until recently considered stormwater concerns other than drainage.

• Available sites for new development are rare.

• Aging infrastructure suffers from ownership questions, neglect, and cost constraints for upkeep.

What BMPs are we looking at?

• Basin Retrofits

• Erosive Swales

• Floodplain Restoration

• Streambank Restoration

• Riparian Buffer Plantings

Basin RetrofitsPros:

• Fix what’s broken → political will

• Possibly find other stakeholders

• Archival research may help lessen the effort of determining the BMP Effectiveness

• Public awareness

• DEP permitting

Cons:

• No guarantee of finding them

• Possible resistance from involved parties

• Ancillary problems (trash & other nuisances)

• DEP permitting

Conventional Basin from 1980s

• Located in an easement across several properties.

• Maintenance responsibilities very vague.

• Maintenance requirement citation skipped after first deed.

• Neglect leads to obscuring vegetation and basin fills in with sediment.

• Outlet structure is blocked/buried and emergency spillway is actuated regularly.

• Berm begins to erode.

August 2016

• Vegetation obscuring the basin, endwall, berm, & spillway.

• Sediment between 2’ and 3’ deep inside basin. Standing water most of the time.

• Outlet pipe completely buried and hidden.

February 2017

• Berm at spillway is failing.

The Fix• Explain to property owners

• Provide technical guidance on repairs

• Follow-up to answer questions

• Develop shared responsibility for restoration tasks

• Establish a timeline for the work

• Provide inspection during and after rehabilitation

How did we get started with the Kensington Club project?

• Call from Apartment Complex manager that a pipe in a swale had become exposed → sewer service lateral…CLAY PIPE!

• Highly eroded and deep swale

• Entire area was overgrown with vegetation

• Downstream City property owners experiencing a lot of flooding and debris. “Can you do something?” FOUND IT!

• Concrete encasement repair, first…then broach the subject of the basin

• File research produced plans from 1973

2005 image of forgotten basin of 1973

Hamilton ES - City

Kensington Club -Township

Breached berm with discharge barrel

Consensus building

• Make everyone aware, provide documents, and be available to answer questions.

• Prioritize what should happen first.

• Acknowledge property owner responsibilities, but be a partner in resolution.

• Explore grant funding and be creative about how to maximize its usage.

• Plan each step and adjust along the way.

• Keep everyone informed, even with bad news.

2018 image of forgotten basin of 1973

Survey & design plans for basin rehabilitation

Kensington Club basin - highlights

• Reduced stormwater flow rate and generation of sediment & debris

• Re-established a maintainable SWM facility

• Identified ongoing maintenance responsibilities

• Reduced Township’s sediment load by 357K# per year

• Highlighted the need for above issues with general public

• Re-created a pedestrian walkway from the apartment complex to the Elementary School

• Necessitated an informal 4-way partnership in order to leverage each stakeholder’s offerings and to reward each with proportional benefit

Everybody pitched in…

• Lancaster Township

• Kensington Club

• School District of Lancaster

• Lancaster City

• PA Department of Environmental Protection

• Lancaster County Conservation District

Township roles & responsibilities

• Measurements of 2017 field conditions for sediment rate

• Material procurement

• RCE, gravel laydown area, and site restoration

• PC and BOS approval of the SWM Site Plan

• Solicitor and bookkeeping

• Sediment reduction part of our Chesapeake Bay PRP

• Coordination, design, and project management

• Ongoing inspection obligations

Lancaster Township PWD scope on Hamilton ES property

Lancaster Township PWD

• Rock Construction Entrance

Lancaster Township PWD

• Gravel Laydown Area

School District of Lancasterroles & responsibilities

• Allowed project to be constructed partially on their property, plus a Rock Construction Entrance and gravel laydown area

• Agreed to allow ongoing maintenance of the basin

• Restricted our time for construction to the summer break

• Were very patient as the final wrap-up tasks overlapped into School being back in session

• Students participated in opening ceremony for pathway

City of Lancaster and PA DEProles & responsibilities

• City granted waiver and provided technical advice

• City has right to inspect the basin

• City benefits from reduced flow and debris

• City can take advantage of drop manhole for future swale improvements

• DEP provided $200K grant

• DEP allowed activity as a waiver

• DEP provided guidance and administrative direction for grant

September 2018 – 22 months since discovery

Five Take-Aways

• Collaboration will get more done.

• Rebuild & repair, rather than build new.

• Don’t know, if you don’t ask.

• Be on the look-out for grant opportunities.

• Even in the wettest year recently and without all the details being ironed out in advance, we can all work together to solve problems.