Derry Township Stormwater Requirements
What triggers a stormwater plan for a home project, and what to expect.
Derry Township requires stormwater management for many residential projects that add impervious surface. For homeowners in Hershey, that can include a patio, pool, garage, addition, driveway expansion, or new home. This page gives a general overview so you know what to expect before you apply for a permit.
What Counts as New Impervious Area
Stormwater requirements are based on new impervious area, meaning surfaces that do not absorb rainwater, such as roofs, pavement, patios, and pool decks.
The Township counts new impervious area cumulatively since December 21, 2010, so additions, sheds, patios, and driveway expansions built since then count toward the total when you add something new.
How the Requirements Scale
Derry Township exempts new impervious area up to 5 percent of the lot area, with a minimum of 200 SF and a maximum of 1,000 SF. Exempt projects must still avoid creating drainage problems for neighboring properties. Beyond the exempt amount, a stormwater management plan and report are required, and larger projects carry additional design and documentation requirements.
The thresholds and requirements are set by § 174-12 of the Township’s ordinance.
Erosion and sediment control is required for any earth disturbance, even when a project is exempt from stormwater management.
What the Township Reviews
When a plan is required, the submission typically includes an application, a stormwater management plan and report, and the required fees. The Township’s consulting engineer reviews it, and approval is needed before work begins.
Approval can also involve recorded documents, such as an operation and maintenance agreement, before a permit is issued. It helps to start early, particularly if a contractor is waiting to begin.
How Elsa Associates Helps
Elsa Associates determines whether your project triggers the requirement and, when it does, designs a practical solution and prepares the plan, report, and supporting documents for submission. Because Elsa Associates works with the Township’s ordinance regularly, it can usually tell you early what to expect and whether the design can be kept simple.
Read more about civil engineering in Hershey and Derry Township, start with Do I Need a Stormwater Plan?, or read our Stormwater Management Basics for Homeowners guide.
Refer to the Ordinance
This page is a general overview, not a substitute for the ordinance, which the Township can amend. Stormwater management is governed by Chapter 174 of the Derry Township code. Refer to the Derry Township Stormwater Management Ordinance for current requirements, and visit the Derry Township website for applications and submission guidance.
Planning a Project in Derry Township?
Before you apply for a permit, an early conversation can clarify whether stormwater management applies to your project and what the Township will need to see.