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Home My WebLink AboutSS5 - Balboa Island Drainage - PowerPoint:r:1 I *"TON' a P reTir ■ • r raTe' • .mow 440`•L• kill. ..a rani 3 I =1 COL,�INS ISLAND _ MARINE AVENUE BRIDGE _ � • � � � � � ro _ � raj, �� `S' . 40, h _ ',.Balboa Avenue, . �1G•§ALBdA•� I • -' - ,_ - ~': Park viii e� ISLAND FERRY 14 '10 131 . _ PARK AVENUE r .r r r i Balboa Island Elevations • Balboa Island is lower than all other island in the bay. • Surface elevations range from 4.5 feet to 8.5 feet. (Lido Isle: 10'-13') • The west side of the island is the low end. Balboa Island: High Tide is Higher than Streets ➢ High tide elevations in Newport Bay typically range from 4.5 feet to 7 feet. ➢ King tides are up to elevation 8 feet! ➢ West end street and sidewalk elevations are about 5 feet. Tide gates are closed to prevent high tides backing up through storm drains and flooding into the streets and private property Ray Ti Road /11\ INIONION MMEN P Present Storm Drain System with Tide Gates ➢ Balboa Island has 25 tide gates (with 25 drain lines) located along the periphery of the island ➢ These gates are manually shut when tides get above 4.5 feet (NAVD88 reference datum) r s(w a �♦ ♦!' � `;'``, sir ss ._s� _� s ... = sls �.•i s s `� �� C :`:•'SIC BE �r ♦ ♦ • : �I I C � 11111 . IM Tide Gates ➢ Protects the island from flooding due to high tides ➢ Currently manually operated Manually Operated with Valve Key Motor -operated, Locally Controlled with Manually -Operated Switch Utility Department staff mobilize almost daily to open and close tide gates, rain or shine, to protect streets from flooding during high tides. ^' 360 tide events/year 1600 labor hours/year s��FF 00 e 4G"�T F 44el SEA WAq A I i I L -LL - -_..�-_yam_ .:�..��,,.:s._-' •_ �•-z�tz^c7s�^�'�e--�� •;s_y,>t •3.T�K. ...w-r�: z"`- —Y. _ r`�,,,,- ^'swcav�.- •..�-i. � -_ T.T.• All Rainfall -related Street Flooding Thanksgiving Day 2019 Note low finish floor elevations of cottages. The real threat from a flood is the water just needs to rise for a moment, and the damage is done! Flooding Event, Balboa Avenue at Marine Avenue Looking East (2-27-2010) Street Flooding Overtopping Curb at Turquoise Avenue (12-22-2010) City crews come out with portable pumps and move from street end to street end. ➢ A dozen or more staff come out 12-18 times a year, often at night, often on overtime, deploying and operating truck mounted portable pumps and discharge lines at all street ends on Balboa Island. ➢ During wet years, working 800-900 labor hours/year pumping just on Balboa Island. ➢ Flooding events can be expected to be more frequent requiring larger crews and bigger pumps. Proposed Long -Term Drainage Solution Replace this manually -operated tide -gate system with an automated pump station. Install a new storm drain system that gravity drains to this pump station ✓ An automated pump station would reduce/eliminate street flooding during storm events and protect houses, vehicles and other property from flooding. ✓ Drainage protection is "24/7" and not dependent upon calling in crews and equipment. ✓ Would greatly reduce staffing and equipment demands. ✓ Low flow urban runoff water would be collected in the pump station and diverted into the sanitary sewer rather then being allowed to drain directly into the bay as currently happens. This would improve bay water quality. 0 0 0 Pump Station Concept Adjacent to Grand Canal (to Serve Islands's East Quadrant) Pump Station J A ��-- 7�\ A 41k Discharge line subject to potential sand clogging and beach erosion. Limited street space requires underground emergency generator. Less desired options for locating the above -ground control panels. Potential Pump Station Locations A - Park Avenue at West End B - North Side of Island C - South Side of Island D - Balboa Avenue at Grand Canal—Limited Area. Sand Accumulation Clogging Outlet Discharge Line Concept- South/North Sides of Balboa Island o Safety issues for boaters and beachgoers near discharge endwall. o Will likely get close scrutiny by Coastal Commission. R71'ALLL, a ,LL Evaluating Pump Station Locations A - Park Avenue at West End — Recommended Location B - North Side of Island — Limited Area. Difficult discharge and permitting issues C - South Side of Island — Limited Area. Difficult engineering and permitting issues D - Balboa Avenue at Grand Canal — Limited Area. Sand Accumulation Clogging Outlet West End Pump Station L Ambor, - -4 fro . , ocation Draft Concept Pumped Flows "Bubbles -out" at Outlets within Bridge Abutment Draft Concept �� ) ,, t A J d � �; ;` � �L��9.. � ,♦ 1' "' A�k1yf1 � /n� �r �� , r ��0 L_ STOP K - �A� ♦• R. aacee � a.� '� YJ�. .�-' i�" -.e �■ __ �_: as � ., - I �- - Stormwater Discharge Hidden under Planter 7 Draft Concept Pump Station Concept ➢ Stormwater flows enter the pump station wet well via underground � pipe. ➢Storm water flows pass through trash and debris removal screens. ➢ Two small pumps send small dry - weather nuisance flows to sewer. ➢ Storm flows discharged into bay by four electric non -clog, tube style submersible pumps - multistage centrifugal pumps operating in a vertical position. Iso VIEW -1 SCALE ,, Good Access for Pump Station Maintenance at West End of Park Avenue -4, --------------------- --------------- VW — — ✓ Underground pump station with quiet electric motors. Draft Concept ✓ Discharge lines outlet in bridge abutment. ✓ Safe discharge via "bubble -up" flow. ✓ No sand clogging or exposed discharge lines. ✓ No conflict with beachgoers. Emergency Generators and Electrical/Control Cabinets would be Hidden within Landscaped Areas ➢ One or two 80 kw natural gas emergency generators Draft Concept ➢ Electrical and control panels ➢ Aesthetically located within planter areas Construct/Rebuild Storm Drain System to Gravity Drain to Pump Station 6f f W-1 ➢ 60 -inch storm drain mainline runs down Park Avenue flowing west. ➢ Lateral drains, ranging in diameter from 18 -inch to 36 -inches, gravity flow to the Park Avenue mainline. Construction Cost Estimates for the Different Drainage System Options 4 PUMP STATIONS 2 PUMP STATIONS 1 PUMP STATION A -Park Ave. at West End A -Park Ave. at West End A -Park Ave. at West End B -North Side of Island C -South Side of Island D -Balboa Ave. @ Grand D -Balboa Ave. @ Grand Canal Canal Pump Station w/ Discharge Lines $7,4001000 $5,350,000 $3,850,000 (demo/civil/struct/mech/elect/gen) Storm Drain Piping System $31575,000 $41687,500 $61075,000 11,000 Lr x 16- avi 12,500 Lr x _L6- ave 13,500 Lr x L4" avea SUBTOTAL $10,975,000 $10,037,500 $91925,000 25% CONTINGENCY $21700,000 $2,500,000 $21500,000 TOTAL $13,700,000 $12500,000 $12,400,000 Advantage Summary for Pump Station Options 4 Pump 2 Pump 1 Pump Stations Stations Station 1 Lowest Cost Option 2 Best Space for Future Maintenance Above -Ground Emergency 3 Generators 4 No Check Valves Discharge Lines Not Subject to Sand 5 Clogging Adequate Space for Electrical and 6 Control Cabinets Discharge Flows have Lower Conflict 7 with Boaters and Beachgoers �I Lower Hurdles for Coastal 8 Development Permit Summary of Recommended Option ➢ The best option is a single pump station with a capacity 40,000 gallons per minute. This would protect the island from a 100 -year extreme rain event. ➢ A 60 -inch diameter storm drain would be installed along Park Avenue (west end) to feed the pump station. ➢ A total of 131,500 feet of new storm drain pipe would be constructed to gravity drain the entire island to the pump station. ➢ 50 new catch basins would be constructed. ➢ Pumps would be electric -powered with 1 or 2 on-site, natural gas generators installed to provide emergency back-up power. ➢ Construction Cost Estimate w/ contingency: —$12,400,000 (Pump Station and Storm Drain System) Construction Challenges 1. Traffic control and parking impacts. 2. Avoiding/Relocating water, gas and other utilities. 3. Dewatering— Groundwater is 3 to 5 feet below ground surface. 4. Stockpiling and export of trench material. 5. Maintaining Collins Isle access. 6. Work site constraints on the island. 7. All Work is in close proximity to occupied residences. 8. Other Funding Allocation Schedule Design Allocation 2020-2023 $1,600,000 FY 23/24 FY 24/25 FY 25/26 TOTALS $1,600,000 Construction Allocation $41800,000 $31800,000 $3,800,000 $12,400,000 Action Design and Permitting Pump Station West End Storm Drains East End Storm Drains Potential Project Schedule ➢ 2020-2023: Prepare Construction Documents and Obtain Permits ➢ April 2024: Construct Pump Station (9 month duration) ➢ April 2025: Construct West End Storm Drains (9 month duration) ➢ April 2026: Construct East End Storm Drains (9 month duration) In 0N � is Questions/Discussion 5� 4,�� .�, �,., s�,• 'rites ,,�>s`-: .` oF�• �. �� r Tv MAP jj It -LAM Own TZ • "�.....r ' .a'?[�'w � e# .i .. t�'- +fin.. ,t'd, «� a � . � • _,..8. .,:.�'. G+� j . all -� _ _ , �- •� .-..� � 7-:y � T � �, `^`� �" � _ .� •. �� .' f _ - _ ��" f ter-' J' -- '^� ,. e '( .._ _- 11.4 c*. ,ter'_ J. .•�'I^: •+yfir� ldfti y~�.� •� j '