118-22 Correspondence - Jenne Associates.pdf

To: Township of West Orange Re: Engineering Services for Investigation into Stream Flooding along the Tributary to Wigwam Brook FULL ENGINEERING ANALYSIS Date: April 11, 2022 Page 2 of 4 JENNE ASSOCIATES, LLC Consulting Engineers 2. Undertake an in depth field evaluation of the stream and pipe system from its confluence with Wigwam Brook upstream to Mountain Avenue where the stream channel begins, documenting stream and adjacent ground conditions, crossing structures (bridges/culverts) and other factors that affect the amount and velocity of the water. Included in this effort will be an evaluation of the route the water flows over the properties on Park Drive North and Park Drive West, discussions with the residents affected by the flooding as well as DPW staff that have responded to the cleanup efforts. 3. Working with the West Orange Tree Consultant, undertake an evaluation of the visible tree limbs and other debris currently lying on the ground adjacent to the stream that could wash into the stream (and then be carried down to the pipe system entrance) as well an evaluation of the potential of exiting trees in the area to drop additional branches in the future. 4. Develop a scope of work for a pipe inspection contractor to undertake a video inspection of the condition of the underground pipe system and provide onsite coordination with the contractor during the filed operation. It is anticipated that this work will be contracted for directly by West Orange. 5. Develop a scope of work for a NJ Licensed Land Surveyor to: • Undertake a topographic survey of the stream from where the properties flood along Park Drive West and Park Drive North to the driveway bridge/culvert located just upstream of the pipe inlet location; • Obtain cross sections of the stream up to the Bloomfield Way bridge/culvert as well as the geometry and elevations of the pipe system and other bridges/culverts crossing the stream. • Obtain cross sections and crossing bridge/culvert geometry along Wigwam Brook from where the tributary joins to a point 500’ downstream. • Stream cross sections will be every 100’ as required by NJDEP. The stream cross section and pipe/bridge/culvert information is necessary to undertake the stream flow computer modeling required to establish stream flow characteristics, evaluate the reduction in flooding that can be expected from alternate improvement options

s necessary to undertake the stream flow computer modeling required to establish stream flow characteristics, evaluate the reduction in flooding that can be expected from alternate improvement options investigated and as will be required for any NJDEP permitting required for the construction. 6. Based on the surveys and the video inspection, evaluate the condition of the underground pipe system documenting any structural or other issues that need to be addressed that either impact the ability of the pipe to handle the floodwater flowing through it or have the potential to cause a future problem or possible failure/collapse. Any conditions of structural concern will be brought to the immediate attention of West Orange to be further evaluated and addressed. 7. Undertake a hydrologic analysis of the stream, in accordance with NJDEP requirements, to establish the peak flow rates that can be expected to occur for various intensity (and probability of occurrence) rainfall events.