2007/11/21 Council Agenda Packet

PHASE 4-SN0110M IS.11 RI.VEIR CSO INTERCEPTOR —ECLIPSE PIPELINE PROTECTION INTRODUCTION The City of' Everett Dcpartnicnt OF Public N-`orks has requested that URS Corporation evaluate the impacts of the Eclipse part of the proposed Everett Riverfront Development on two Snohomish River CSO Interceptor Pipelines that underlie Chestnut Street (former Eclipse Mill Street) between 36°i Street and Pacific Avenue, and one pipeline that underlies 36"' Street at Chestnut. URS was also asked to develop conceptual -level options and costs for protecting the pipelines. This Eclipse area work is Phase 4 of the 36'x' Street Sewer Protection Project contract between the City and URS. Two other pipelines that underlie 36'x' Street at Chestnut Street were evaluated in 2006 as Phase I of the 36"i Street Sewer Protection Project at another location for a Burlington Northern Santa Fe Railroad (BNS'') rail crossing, and will not be re-evaluated in Phase 4. "fhe Eclipse Development was described by Mr. Souheil Nasr, PJ`. of the City to Messrs_ Cecil Urlich. P.E_ and Brian Il.antilton, P.G., and Dr. Xtangdong Ilan, P.E. of URS over the phone on September 19, 2007 and during several later communications between Messrs. Nasr and Urlich. The development will replace Chestnut Street and a BNSP track by an engineered till. The initial scope was to evaluate the fill height that could be placed without impacting the Pipelines. An expanded scope was to develop conceptual -level design options and costs for protecting the pipelines. The options were developed during meetings between Messrs. Nasr, Urlich and Han on October 26, and Messrs. Nasr, Dave Davis, Jim Miller and Mark Sadler of the City and Urlich and plan on October 29. 'File final till height was confirmed on October 30, 2007. PROJECT BACKGROUND The Everett Rivertrom Development is a proposed retail, coirunercial and residential project alone the west side of the Snoqualmie River between south of 4I" Street to Pacific Avenue. The City is selling, land to a developer, Oliver McMillan. The Eclipse area is along Chestnut Street between 36'x' Street and Pacific Avenue, and is the most northern 2,400 feet of the development. The City provided URS with pipeline plan and profile design drawings for use in the Phase 1 and 4 evaluations_ The URS understanding of the existing pipeline conditions and proposed Eclipse project is based on these documents and on information provided by Mr. Nasr; and on pipeline location discussions between Mr. Sadler and Dr. Han at the site on September 20, 2007. The Eclipse site is about 2,400 feet lone between 36"' Street and Pacific Avenue. The site is on a bench bounded to the west by a slope up to nine feet above the west edge of Chestnut Street and to the east by the west bank of the river. The top of the slope is at an elevation of about 22 feet (El. 22). The road surface near 36°i Street is at about El. 13, but rises to the north. 'File developer initially proposed fillin<g to the 500 -year flood level of around El. 20, which would result in up to 7 feet of till in the lower part of Chestnut and 36'x' Street. On October 30, 2007, the City informed URS that the developer planned to till to the 100 -year flood level at around El. 18.5- This would require that 5.5 feet of fill in the lower part of Chestnut and 36°i Streets. 1Q URS Page 6 of 10