Addendum # 1 - Answers to Questions

Description

City of Isle of Palms, South Carolina Request for Proposals (RFP) 2018-02 Phase 3 Drainage - Outfall Design and Permitting Addendum #1 – Answers to Questions 1. Can the City define “reasonable expectation of sea level rise”, or will the selected consultant provide input as part of the scope of services? Answer: The City will rely on the selected consultant to provide input on determining what a reasonable expectation of sea level rise shall be, but from reviewing NOAA and USACE projections, the City would assume that a two-foot increase over 50 years would be a reasonable projection. 2. Can the City define “reasonable expectation of increase in impervious surfacing”, or will the selected consultant provide input as part of the scope of services? Answer: The City will rely on the selected consultant to provide input on determining what a reasonable expectation of increase in impervious surfacing shall be; however, the City can provide as-built surveys showing the percentage of lot coverage of new construction, as well as building permit records showing the rate that properties are being redeveloped. The City’s impervious coverage limit is set at 40% of the lot area. 3. For the Hurricane Joaquin design condition – does the City expect the design to prevent flooding of structures during the Hurricane Joaquin surge (stage up to elevation 5.0 ft NAVD 88) and the associated rainfall amounts (20”+ over a 72-hour period)? Answer: The RFP includes a task that requires the chosen consultant to provide conceptual solutions and an estimated cost and level of service for each of these solutions. The City expects to be able to make a final decision on the level of service at that time. The City also recognizes that the chosen consultant will only be working on the identified outfalls and cannot be held responsible for water that may not be able to get to the outfall. The City will rely on the selected consultant to provide information on the surge elevations and rainfall amounts associated with Hurricane Joaquin, and the City would expect the selected consultant to use these conditions to recommend outfall improvements that would allow enough water to pass through the outfall to prevent a storm of this magnitude from damaging structures. The City is unaware of any major damage to structures that occurred during Joaquin within the associated drainage basins. 4. Will the City have other design considerations, i.e.