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HomeMy WebLinkAboutItem Th � AGENDA REPORT y3 DATE: April 23, 2001 / TO: Honorable Mayor and City Council THRU: John B. Bahmski, City Manager FROM: Stephen G. Badum, Director of Public Works/City Engineer SUBJECT: EMERGENCY REPAIR - SEAL BEACH SAND RETENTION GROIN SUMMARY OF REQUEST: The proposed City Council action will approve a resolution making findings regarding the urgency of the proposed temporary repair, approve a budget amendment, and authorize the City Manager to negotiate contracts at a cost not to exceed $100,000 to repair the City's sand retention groin. The Seal Beach Sand Retention Groin was originally constructed in 1959 by the U.S. Army Corps of Engineers. The sand retention groin was designed to slow the natural migration of beach sand and maintain healthy beach widths. Wide beaches prevent public and private infrastructure damage from coastal flooding and provide recreational and economic resources to the City. In 1985, an inspection of the structure revealed the initial stages of deterioration. Since then, the groin has progressively deteriorated to the point where it is urgently in need of renovation. While the City has been successful in obtaining grant funds for beach sand replenishment, efforts to obtain grant funding to repair or replace the forty -two yew old groin have not been successful. The estimated cost to repair and renovate the structure is approximately $600,000. During the past winter storm season, the City's sand retention groin sustained heavy damage to one of its pre -cast panels and cap. City staff contacted Moffat & Nichol Engineers (M &NE) and requested that a letter report be prepared to assess the damage and identify potential solutions (see attached). Upon discussions with M &NE staff, it was concluded that a temporary repair is immediately necessary to prevent sand from filtering through the groin in large quantities. The continued flow of sand through the gap in the structure will result in the need for extensive sand backpassing operations before the next winter storm season as well as the threat of coastal flooding and wave damage to adjacent public and private infrastructure. The estimated cost of the temporary repair is between $50,000 and $100,000 including engineering design and construction management services. The design life of the repair is estimated at five to ten years. ,a./.w..t. T Emergency Repair — Sand Retention Groin City Council Agenda Report April 23, 2001 The City's charter authorizes City Council to award contracts without advertising for bids, if such work is deemed by the Council to be of urgent necessity for the preservation of life, health, or property, and is authorized by resolution containing a declaration of the facts constituting such urgency. Due to the urgency of this repair project, staff recommends that the Council pass a resolution declaring emergency conditions and direct staff to negotiate contracts with Moffat & Nichols Engineers and qualified marine contractors at a cost not to exceed $100,000 to repair the City's sand retention groin. FISCAL IMPACT: Funds are not currently budgeted for the proposed work. Staff proposes that the City utilize unexpended funds in the amount of $45,000 from the Environmental Reserve Fund. Additionally, it is recommended that two current projects within the Tidelands CIP be deferred to next year with the funds re- appropriated to this project (Pier Structural Inspection Program, $40,000 and Pier Stairway, $15,000). RECOMMENDATION: It is recommended that the City Council: 1) Approve a resolution making findings regarding the urgency of the proposed temporary repair, 2) Approve a budget amendment deferring and re- appropriating capital improvement project funds, Pier Structural Inspection Program, Acet.#034- 49715 -065, $40,000 and Beach/Pier Access Sidewalk/Stairway, Acct. #034 - 49811-063, $15,000 from the Tidelands Fund and appropriating $45,000 from the Environmental Reserve Fund for the subject project in the amount of $100,000; and 3) Authorize the City Manager to negotiate contracts with Moffat & Nichols Engineers and qualified marine contractors at a total cost not to exceed $100,000 to repair the City's sand retention groin. C Stephen'(; adum, Director of Public Works/City Engineer NOTED AND APPROVED: Agenda Item 1/11 MOFFATT & NICHOL April 5, 2001 City of Seal Beach City Hall, 211 Eighth Street Seal Beach, CA 90740 Attn: Mr. John Bahorski, City Manager Subj: Seal Beach Groin, Damage Condition and Ramifications M &N File: 3874 -01 Dear Mr. Bahorski: The purposes of this letter report are to (1) describe the damaged condition of the groin under Seal Beach Pier; (2) discuss possible consequences if the damage is not repaired; and (3) present concept -level costs to repair it temporarily and for the long -term. Moffatt & Nichol Engineers (MN &E) has served the City since providing engineering and design of the initial groin construction in 1959, as well as monitoring the deterioration of the groin from the 1980's to the present. GENERAL BACKGROUND The beach within the City of Seal Beach is a public beach, separated into two roughly equal segments at the groin, known as West Beach and East Beach. East Beach has a chronic erosion problem resulting in loss of public recreation area and protection of property from coastal storm damage. Past beach nourishment projects have helped reduce this problem. However, one key element to the future stability of East Beach is the groin. The groin holds sand and retains a significantly wider beach at East Beach for a longer period of time than would occur without the groin. It therefore serves the critical function of providing a protective beach for both public and private property landward of East Beach. PREVIOUS GROIN INSPECTIONS Since the initiation of monitoring, the groin has progressively deteriorated and now is substantially damaged. M &NE was first requested to inspect the groin in 1985. The resulting inspection report indicated cracking of and substantial damage to the cap, spalling of concrete sheetpiles, and development of a gap at one construction joint. The report further indicated that without repair, the cap could continue to deteriorate and portions could be lost, spilling would progress, gaps would open allowing transmission of sand, shear keys (interlocks between concrete sheetpiles) would wear out, and sheetpiles could separate from their key and tilt. The groin was inspected by M &NE again in 1994, confirming that these conditions had progressed. Cursor py inspection occurred once again in 1998 by M &NE when high waves and tides on January 30 damaged more of the cap than had previously been damaged. Each inspection report states that the service life of the structure would significantly increase if repairs were made. A shortened service life or inoperable groin would result in increased sand 250 West Wardlow Road, Long Beach, California 90807 P.O. Box 7707 (562) 426 -9551 Fax (562) 424 - 7489 -- City of Seal Beach Mr. John Bahorski, City Manager April 5, 2001 Page 2 1/hq loss from East Beach, increased coastal flooding and wave damage to structures, and consequently increased costs to the City. CURRENT GROIN CONDITION Jim Crumpley and Chris Webb of M &NE visited the site and met with City staff on March 22, 2001. Observations indicated that a portion of the cast -in -place concrete cap for the groin has completely broken apart in the vicinity of the lifeguard tower (Station 9 +10 to Station 9 +50 in the M &NE groin inspection report of 1985). A section over four sheetpiles has fallen off and exposed the now unsupported piles. One of the exposed piles has now failed leaving a gap in the wall through which water now passes at high velocities both ways during the passing of each wave or swell. The portion of the cap section that remains has rotated and appears ready to fail under severe wave action. This condition not only presents a hazard to surfers and swimmers, but a potential conduit for loss of sand from East Beach and a precursor to more extensive groin failure. POTENTIAL CONSEQUENCES IF NOT REPAIRED If repairs are not performed, the damages to the groin will continue and probably accelerate. The gap in the structure allows water to flow through at high velocities (see photos 1 & 2), which will erode the sand around the adjacent sheetpiles where the cap is missing and cause these adjacent sheetpiles to fall. Additionally, the remaining portion of the cap for the damaged section is rotating (see photo 3) and may fall off during a significant wave event leading to more sheetpile loss. Eventually larger sections of the cap could be damaged or destroyed, leading to collapse of longer sections of the concrete sheetpile wall and potential failure of the entire effective length of the groin (the segment seaward of the existing shoreline position at West Beach). The existing condition of the groin results in more rapid loss of sand from East Beach to West Beach than has previously occurred. In this condition, the beach at East Beach could potentially become narrower each year, requiring more frequent sand backpassing from West Beach to East Beach by the City. If not repaired, incremental increases in damage of the groin over time would only exacerbate this condition, leading to progressive narrowing of East Beach and increased coastal flooding to public and private property. Ultimately, the effective segment of the groin could totally collapse without repair or maintenance. In this event, the shoreline at East Beach would recede landward from its present position and encroach on Seal Way. Nearly constant maintenance could be required to keep flooding from occurring under high tides or waves. Little or no protective beach buffer could be maintained at East Beach and properties would regularly be vulnerable to coastal flooding. Additionally, the beneficial effects of the recent cooperatively- funded State and City beach nourishment project would be lost. Damage costs to the City could soar and the quality of life could be diminished. COST OF TEMPORARY REPAIRS We estimate that a temporary repair at the existing gap could be constructed using steel sheetpiles, wales, clamping bolts, and temporary fill material. This would likely cost in the range of $50,000 to $100,000 and would allow for a five to ten year life prior to final repairs. This does not eliminate the need for concrete repairs along other portions of the groin that are equally in need. City of Seal Beach Mr. John Bahorski, City Manager April 5, 2001 ,", Page 3 COST OF LONGTERM REPAIRS Long -term repairs are not as easy to estimate without analyzing alternative approaches for constructibility. However, it is likely to be at least twice the cost of the temporary repair, or in the range of $100,000 to $200,000 to repair the existing gap, and $350,000 to $500,000 to repair the entire groin structure. CONCLUSIONS The Seal Beach groin is in urgent need of repair. Lack of maintenance and consequent continued deterioration of the structure have led to a damaged condition that jeopardizes the structural integrity of the groin and its sand retaining capabilities. The shoreline position at East Beach may recede if the structure is further damaged or collapses. East Beach is a protective buffer to public and private property along Seal Way. These properties will be threatened if the beach retreats posing an ever - present hazard to the City. East Beach also provides important public recreation opportunities. We hope this clarifies existing conditions, and provides information to assist with the City's decision - making in [his matter. Thank you for the opportunity to continue serving the City on this important project. Please call Jim Crumpley or me with any questions or comments. Sincerely, MOFFATT & NICHOL ENGINEERS Chris Webb Project Manager CKW /pjs PmWW397C 2.]W Enclosure City of Seal Beach Mr. John Bahorski, City Manager April 5, 2001 Page 4 1„1 Photo 1 f / City of Seal Beach Mr. John Bahorski, City Manager April 5, 2001 Page 6 Photo 3