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Rahway Alternatives Being Evaluated

Current Forms of Upper Rahway (Cranford) Alternatives Being Evaluated:
  • Alternative #1: Channel work from Lenape Dam to Lincoln Ave. Bridge, and modification to Lenape Park Detention Basin*
  • Alternative #2: Channel work from Springfield Ave. Bridge to Lincoln Ave. Bridge, and modification to the Nomahegan levees and Lenape Park Detention Basin*
  • Alternative #3: Channel work from Lenape Dam to Lincoln Ave. Bridge and dredging Orange Reservoir to increase storage capacity*
  • Alternative #4: Channel work from Lenape Dam to Lincoln Ave. Bridge and new outlets at Orange Reservoir
  • Alternative #5: Channel work from Lenape Dam to Lincoln Ave. Bridge and the construction of South Mountain Regional Detention Basin*
  • Alternative #6: South Mountain Regional Detention Basin*
  • Alternative #7: Non-Structural Plan
  • Alternative #8: Modification to Lenape Park Detention Dam and new outlet at Orange Reservoir
  • Alternative #9: Modification to Lenape Park Detention Dam, new outlet at Orange Reservoir and channel work from Springfield Ave. Bridge to Lincoln Ave. Bridge in Cranford   

* Alternatives with a line through them have been screened out due to results of continued analysis as well as public feedback gathered in spring 2014. These alternatives will not be part of the study as it moves forward.

Current forms of Lower Rahway (Robinson's Branch) Alternatives Being Evaluated:

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Upper Rahway (Cranford) Alternative #4


Channel work from Lenape Dam to Lincoln Ave. Bridge and new outlets at Orange Reservoir

Alternative #4: Channel work from Lenape Dam to Lincoln Ave. Bridge and new outlets at Orange Reservoir.

This plan includes approximately 15,500 ft channel work throughout the extent of the Rahway River in Cranford Township, from Kenilworth Blvd, just downstream of Lenape Dam, to a point approximately 1,500 ft downstream of the Lincoln Avenue Bridge. Approximately 1,400 ft of the channel work is expected in Nomahegan Park. The downstream slope is approximately 2.6 ft/mile with a maximum deepening of about 3.7ft near Hansel Dam. The new trapezoidal channel will consist of a combination of natural bed channel or riprap material, a 60 ft. bottom width with side slopes raging from one vertical on two horizontal (1:2), to one vertical on two and a half horizontal (1:2.5). There will be approximately 2,000 ft of new and removed/replaced retaining walls. Also, the Union Ave. and North Ave. Bridges are going to be removed and replaced. This plan requires little to no dredging in the reservoir, the installation of additional outlet pipes and pre-storm lowering of the reservoir to maximize use of the existing reservoir capacity.

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Upper Rahway (Cranford) Alternative #7


Non-Structural Plan

Alternative #7: Non-Structural Plan with a 1% chance of annual exceedance along the Rahway River at Cranford.

Non-structural measures are currently under identification and evaluation for approximating 374 structures contained in the 1% annual exceedance (100-yr) flood inundation map for the Rahway River at Cranford. Potential measures for evaluation includes structure rising (elevating), wet floodproofing, dry floodproofing (sealants and closures), ringwalls/ring levees and other actions.

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Upper Rahway (Cranford) Alternative #8


Modification to Lenape Park Detention Levees and Orange Reservoir Outlet Modification

Alternative #8: Modification to Lenape Park Detention Levees and Orange Reservoir Outlet Modification.

This plan includes the modification of the Lenape Park Dry Detention Dam to increase the water storage capacity in the basin. This modification will include three main components; (1) raising the existing Lenape dam structure and widening the orifice, (2) raising embankments 6 ft. above the existing, and (3) adding 6 ft. of floodwalls to the existing embankments in the northern area of Lenape Park near Fadem Rd. at Springfield Township.

In addition, the plan requires the installation of two additional 36 in. diameter outlet pipes in Orange Reservoir and operation of the dam two days prior to a storm event for a drawdown of about 10ft. to15 ft. from a maximum depth of about 30 ft. to a depth of about 15 feet.  This plan requires little to no dredging in the reservoir.

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Upper Rahway (Cranford) Alternative #9


Modification to Orange Reservoir and Lenape Park Detention Levees, and Channel Improvements

Alternative #9: Modification to Orange Reservoir and Lenape Park Detention Levees, and Channel Improvements.

This plan includes the modification of the Lenape Park Detention Dam to increase the water storage capacity in the basin. This modification will include three main components; (1) raising the existing Lenape dam structure and widening the orifice, (2) raising embankments 6 ft. above the existing, and (3) adding 6 ft. of floodwalls to the existing embankments in the northern area of Lenape Park near Fadem Rd. at Springfield Township.

In addition, the plan requires the installation of two additional 36 in. diameter outlet pipes in Orange Reservoir and operation of the dam two days prior to a storm event for a drawdown of about 10ft. to15 ft. from a maximum depth of about 30 ft. to a depth of about 15 feet.  This plan requires little to no dredging in the reservoir.

Some channel work is expected from Nomahegan Park to Lincoln Ave. Bridge. The extent and magnitude of the channel work will be determined in the coming months. The channel work may be minimal, with a deepening of up to 2.5 ft in the Hansel Dam area, minimizing the impact to the channel banks. Modification of Hansel and Droeschers Dam may be possible for this alternative. No bridge modification will be considered and a minimum use of retaining walls. 

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Lower Rahway (Robinson’s Branch) Alternative #1


Floodwalls/Levees and Channel Improvements

Alternative #1: Floodwalls/Levees and Channel Improvements.

This plan includes approximately 6,500 ft of channel work of a 35 ft wide trapezoidal channel, from Maple Ave. to the confluence with the Rahway River, approximately 6,600 ft of levees and floodwalls and approximately 750 ft of retaining walls.

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Lower Rahway (Robinson’s Branch) Alternative #2


Modification to Middlesex Reservoir

Alternative #2: Modification to Middlesex Reservoir.

This plan will include the analysis of the storage available for flood risk reduction in the Robinsons Branch and possible modifications of the existing spillway and outlet. This alternative will require lowering the reservoir level prior to a storm event. This alternative might be analyzed in combination with the Robinsons Branch Alternative 1 or non-structural flood risk management measures.

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Lower Rahway (Robinson’s Branch) Alternative #3


Non-Structural

Alternative #3: Non-Structural.

The nonstructural measures to be considered in this project are: dry flood proofing, wet flood proofing, elevation (aka. raise), barriers (aka. ringwall) and buyouts as explained in Upper Rahway Basin Alternative #7 above. The nonstructural analysis will be done for the Robinsons Branch and other areas along the Rahway River.

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Lower Rahway (Robinson’s Branch) Alternative #4

No Action

Alternative #4: No Action.

No Action is always one of the original alternatives considered as it provides a baseline of data for comparative purposes, showing what might be expected in a study area if no action is taken. 

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