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Improvements to Single and Two-Family Residential Properties
Any improvement to one and two-family homes which creates more than 400 square feet of net new impervious area is required to include an on-site stormwater management facility, subject to Engineering approval of the site plan. Demolition of one and two-family homes also requires Engineering approval of the site plan. This Engineering review of a site plan must be completed before Zoning Department and Building Department permit submittals.
Impervious Area Definition
Impervious area is defined as any surface that has been compacted or covered with a layer of material so that it is highly resistant to infiltration by water. Impervious areas include:
- Roofs
- Asphalt, concrete, paver and stone driveways
- Sidewalks
- Porous asphalt or concrete
- Decks, pools, and patios
The site plan submittal shall include a comprehensive overview of site conditions in accordance with the Engineering Site Review Application 8-24-21 (PDF) . If the site plan is not in conformance with the checklist, the review and approval process will be delayed, which may delay zoning and building department approvals.
Depending on the amount of net new impervious area created, the stormwater management requirements will differ. Small projects are classified as those that create between 400 and 4,999.99 square feet of net new impervious area; large projects are those that create 5,000 square feet or more of net new impervious area.
Stormwater Management Infographic for Small and Large Projects (Examples)
Rain Garden Flyer (English) and Folleto del Jardín de Lluvia (En Español)
Outside Agency Approvals Required for One and Two Family Site Improvements
- If disturbance of 5,000 square feet or more of land is proposed, approval from Mercer County Soil Conservation District (MCSCD) is required.
- If improvements will encroach into or disturb riparian areas along regulated waterways, wetlands and / or flood hazard areas, then approval from New Jersey Department of Environmental Protection (NJDEP) is required.
Construction Phase Inspections
The applicant shall contact the Engineering Department at 609-921-7077 at least 48 hours in advance of the following construction activities, which require Engineering inspection:
- Stormwater management facilities (rain gardens, grass swales, and other management systems) installation - prior to placement of soil bedding and after final grading and planting
- Final site grading prior to seed or sod placement
- Excavation in the public right of way including through curb, sidewalk, landscape, and roadway surfaces for utility or driveway connections - a Permit to Excavate or Occupy the Public Right-of-Way is required
- Changes to the approved site plans
Prior to issuance of a Certificate of Occupancy (CO) by the Building Department, the Engineering Department will complete a final inspection and prepare a punch list of repair work, if necessary. The applicant must contact the Mercer County Soil Conservation District for final compliance inspection and certification. The Engineering Department cannot recommend the issuance of the CO without MCSCD acceptance.