presentation program outline -...

Presentation Program Outline

OVERVIEW / BACKGROUND

TYPICAL AQUSCAPE DESIGN ISSUES

BRIDGEPORT LAKE PROJECT ELEMENTS

ADDITIONAL LAKE FEATURES

MAINTENANCE / MONITORING

SUMMARY / LESSONS LEARNED

Providing Stormwater Managmentwith Manmade Lake Systems

! Specialized aquascape systems provide exceptional water quality through recreating natural biological processes

! Offer innovative approach integrating stormwater treatment and conveyance to urban development

! Utilize multiple layers of treatment features

– Wetland planters– Biofilters– Retention– Pretreatment wetland filters– Aeration


Providing Stormwater Managmentwith Manmade Lake Systems

LAKE WATER QUALITY FUNCTIONLAKE WATER QUALITY FUNCTION

Manmade Lake Construction Costs Comparable to Landscaping


! Typical manmade lake construction costs range from $50,000 to $100,000 / acre of lake surface for a 5 to 20 acre lake

! Shoreline is generally the largest cost element of lake

! Typical landscaping costs range from $75,000 to $120,000 / acre

Aquascape Systems Offer Numerous Benefits over Conventional BMPs

! Enhanced water quality effectiveness

! Elimination of storm drain infrastructure costs

! Aesthetic benefits! Increased residential lot

premiums on the order of 30% for waterfront views

! Flexible integration with development landplan

! Added value to the community

! Water reuse! Nuisance flow treatment


Critical Issue for Maintaining Minimum Operational Water Feature Quality

! Natural eutrophicationprocess related to oxygen depletion and increased nutrients

! Scum formation! Water transparency! Odors! Algae blooms and control! Alkalinity / dissolved salts! Temperature! Evaporation

TYPICAL AQUASCAPE DESIGN ISSUES

Common Design Techniques Addressing Water Quality Requirements

! Prevent stormwater runoff to minimize nutrient inflow

! Water exchange / flushing prevent eutrophication

! Maximum of 30-day turnover allows some nutrient build-up

! 7-day turnover results in clean water

! Closed aquascape system not flushing require annual replacement in fall


Common Design Techniques Addressing Water Quality Requirements

! Park and golf course lakes dual function as irrigation and benefits to allow flushing

! Irrigation lakes allow high turnover and multiple lakes can be interconnected

! Maximum benefit of flushing if “plug flow” can be achieved in lake

! Plug flow eliminates stratification of inflow and maximum turnover

! Correctly locating inlet and outlet at opposite ends with direction of wind will assist in creating plug flow


Bridgeport Lake Project Background

! 750 home residential development by Newhall Land! Located in City of Santa Clarita (38 miles north of

downtown Los Angeles)! Directly adjacent to the Santa Clara River! 212-acre site ! Original adopted development plan included central

park system but no provisions for stormwater quality! Developer completely revised development plan to

integrate flood conveyance and water quality treatment utilizing continuous lake system

BRIDGEPORT LAKE DESIGN ELEMENTS

LEGEND:Lake or water featureLandscaping areaLake wetland plantersRoadsPaseo, Trail & Sidewalks

BRIDGEPORT LAKE SYSTEMBRIDGEPORT LAKE SYSTEM

Bridgeport Lake Summary of Characteristics

! 15-acre lake surface area! 105 acre-feet normal operating water volume! 30-mil PVC liner! Unique shore compsite of grouted cobble covered in dirt to

match area stone work and natural lake look! 2.7 miles of shoreline – 60% public accessible! Average depth of 7-feet with maximum of 15-feet


LAKE LININGLAKE LINING

Bridgeport Lake Primary Functions

1. Provided runoff water quality treatment for entire development watershed

2. Primary conveyance system for all surface runoff that eliminated the need for the originally planned underground storm drain

3. Aesthetic focal landscape feature integrating with overall design theme of the community


STORM WATER CONVEYENCE PLANSTORM WATER CONVEYENCE PLANLEGEND:

Lake or water featureLandscaping areaLake wetland plantersRoadsPaseo, Trail & Sidewalks

Bridgeport Lake Offered Unique Landuse Planning Benefits

! Original development plan had inherent problems that had not been resolved

! Lake solved many of these issues! Lake system provided the ability to

separate private (gated) development from public development area – difficult to achieve with the central park concept

! Private portion of the development utilized “island” areas created in lake to restrict public access.

! Entire lake edge controlled by HOA and no homeowner dock allowed to maintain lake appearance


BRIDGEPORT LAKE DESIGN ELEMENTS – PRIVATE EDGE OF LAKE

BRIDGEPORT LAKE DESIGN ELEMENTS – PUBLIC EDGE OF LAKE

Stormwater Management and Treatment Elements Integrated in Lake Design

! Bridgeport lake unique in combining multiple levels of treatment systems

! Relies on natural biologic processes

! Lake is living system

1. Aeration2. Wetland Filters3. Lake Edge Planters4. Biofilters5. Retention Treatment

Volume


Layout and Geometry Critical Element Affecting Lake Operation

! Residential lake layout to maximize amount of lake home frontage with multiple “fingers”

! Fingers will develop dead circulation zones and require more extensive pumping infrastructure

! “Snake” type layout preferred for maximum frontage and improved circulation with plug flow

DESIGN ELEMENT– GEOMETRY/LAYOUT

Bridgeport Lake Layout Design Issues

! Available site for lake – long linear and narrow! Incorporated both fingers and islands! High ratio of lake perimeter to surface area! Address competing objectives of minimum requirements for

aquascape design compared to developer need to maximize developable area


Determination of Lake Operating Water level and Depth

! Normal operating water level to be compatible with home pads

! Earthwork balance for project

! Evaluate stepped water levels across lake to accommodate differential grade in site or single water surface

! Increased operating depth for retention of stormwater quality volume

! Maximum depth for design Capital Storm (flood control)


Determination of Lake Operating Water level and Depth

! Average operating depth determines effects of temperature and biological reaction times

! Minimum operating depth of 8 to 12 feet eliminate light penetration– Lower average temperature– Eliminate light penetration– Minimize evaporation– Allow temperature

stratification


Lake Section Developed to Address Safety and Operation Issues

! Safety critical concern since perimeter of lake unfenced with open water body

! Section used concrete ledge 18-inches below water at shoreline

! Extended out 10-feet from shoreline

! Protected PVC liner for near shore maintenance

! Lake bottom slopes at 3:1! Steeped concrete shoreline

extended 4-inches above normal water level and to concrete ledge


Maintaining Dissolved Oxygen for Stabilized Lake System

! Introduced through aeration systems for aquascape

! Conventional methods include bubbler or spray systems, and natural wind action

! Spray system require more horsepower to operation without additional benefits

! Bubblers placed at bottom of lake induce vertical recirculation and reduction of surface temperature through detratification

! Generally sized to provide turnover every 3 hours

! Size and location of bubblers based on shape of lake rather than size

DESIGN ELEMENT– AERATION

Aeration Disk Location

Wastewater Aeration System Employed in Bridgeport Lake

! Fine bubble diffusion system incorporates wastewater treatment plant technology

! Key element relies on “aeration disk” rather than conventional diffuser pipe system

! Ability to develop “fine bubbles” achieved from the flexible rubber skin of the disk that precisely controls size of bubbles.

! Importance of fine bubbles involves increased contact area that provides enhanced oxygen transfer


Aeration System Addressed Difficult Design Conditions

! PACE research has found that placement of several disks in pods dramatically improved overall dissolved oxygen .

! Self-cleaning and difficult to plug! Bridgeport utilizes 12 air

compressors (5 cfm each)! Deliver 60 cfm total to 24 disks! Aeration sized to turnover lake every

3 to 4 hours if aeration operating 24 hours a day

! Aeration critical for Bridgeport with the high potential for eutrophicationfrom shallow depths and high temperatures


Aeration Disk Location

Aeration disks

LAKE WATER QUALITY MANAGEMENT AERATION SYSTEMLAKE WATER QUALITY MANAGEMENT AERATION SYSTEM

Aeration Disks

Lake Runoff Pretreatment Achieved through Wetland Filters

! Located at all runoff inflow points to lake! Basin separated from lake with low-height concrete wall! Gravel infiltration basin with void volume to retain frist flush

volume ! Wetland vegetation planted above gravel to assist in flow

distribution

DESIGN ELEMENT– WETLAND FILTER

Lake Runoff Pretreatment Achieved through Wetland Filters

! 24 – water quality wetland filters

! Average surface area 250 s.f.! Basin 3-feet deep with

bottom six inches filled with gravel

! Low flow storm drain pipe discharges to open end vertical standpipe– Nuisance flows discharge to

bottom end of pipe and gravel bed

– High flows overtop standpipe and into vegetated area

DESIGN ELEMENT– WETLAND FILTER

Lake water quality filters

Water Quality Filter

STORMWATER RUNOFF TREATMENT: WATER QUALITY FILTERSSTORMWATER RUNOFF TREATMENT: WATER QUALITY FILTERS

WATER QUALITY FILTER BASINWATER QUALITY FILTER BASIN

WATER QUALITY FILTER BASIN UNDER CONSTRUCTIONWATER QUALITY FILTER BASIN UNDER CONSTRUCTION

Perimeter Wetland Planters Further Enhance Lake Water Quality

! 40 locations periodically located along lake shoreline based on aesthetics and operation

! Combined total surface area of wetlands 12,000 square feet

! Constructed as concrete shelves into lake perimeter shoreline and enclosed with 4-inch thick masonry wall submerged 0.1 to 0.5 below normal lake level

! Planter configuration allow control and limited extent of plant growth into lake open water.

! Soil depth of two feet for wetland planting

DESIGN ELEMENT– WETLAND PLANTER

Primary Lake Water Quality Element Utilized Biofilters

! “Biofilters” function similar to natural aquarium filter system! Consist of self-contained submerged gravel beds that lake water

is circulated underneath through a slotted pipe system! Naturally occurring biologically mass coats the gravel and strips

the water of constituents passing through the filter that promote algae growth

! Recirculation will also promote dissolved oxygen

DESIGN ELEMENT– BIOFILTER


! Important aspect of the use of biofilters is layout and location to maximize the water quality

! Biofilters designed so velocity does not exceed 0.5 gpm per square foot of 24-inch biofilter

! Amount of biofilter depends on amount of lake turnover time– Industry average without biofilters range from 5 to 15 days



! Total of 15 biofilters! Placed at the end of each lake

“finger” to promote circulation! Approximately 1,000 square

feet in surface area! Each treating 500gpm flow

providing a total biofilter rate of 7,500 gpm

! Biofilters 3 to 4 feet deep filled with gravel and submerged 18 to 24-inches below lake surface

! Pumped water from lake distributed through herringbone pattern slotted pipe system underneath gravel bed

! Recirculation occurs 24-hours a day


Maximum Biofilter PerformanceEnsured Through Backwashing

! Effective backwashing required to remove material accumulating in gravel voids

! Build-up leads to gravel bed “packing”! Simply reversing pump slow in the gravel bed is not sufficient to

remove material! Backwash system used a portable pump lowered into vertical

standpipe within the biofilter and lake water withdrawn for 10-15 minutes in reversed direction with discharge to sanitary sewer.

! Rodding of gravel also used! Backwash at least 2 times a year


DESIGN ELEMENT– BIOFILTER UNDER CONSTRUCTION

BIOFILTER POST CONSTRUCTIONBIOFILTER POST CONSTRUCTION

Lake Biofilters

* Biofilter recirculation piping is represented by black lines.

Biofilter

LAKE WATER QUALITY MANAGEMENT: BIOFILTERSLAKE WATER QUALITY MANAGEMENT: BIOFILTERS

Aeration Disks

Water Quality Filter

Biofilter

WATER QUALITY ENHANCEMENT SYSTEMWATER QUALITY ENHANCEMENT SYSTEM

Unique Lake Features Improved Aesthetics and Operation

! Leak detection system below PVC liner

– Not standard but developer required as insurance

– Consisted of 9,400 feet of 3-inch perforated pipe along bottom and perimeter of lake

– Observation manholes provided at 1,000 foot intervals

! Developed new type and construction method for shoreline specific to this lake

– Developer desired lake edge that allowed grass to grow to edge and less engineered appearance

– Shaped concrete edge with cobbles and stone embedded during curing process


Unique Lake Features Improved Aesthetics and Operation

! Numerous architectural features– pedestrian bridges– faux roadway bridges– landmark island / lighthouse– amphitheater– water garden fountains

! Recreation Features– pedestrian trail system– marina


Bridgeport Lane BridgeBridgeport Lane Bridge


Paseos & WalkwaysPaseos & Walkways


!

!

STR ICTLY FOR BIDDEN

FORB IDDEN

!

All neig hborhood stormwater drains in yards, streets, parks,etc. drain to the lake. Therefore, dumping ofhazardous materia l (including , but not limited to,oil, brake fluid, antifreeze, cleaning solu tions, etc.)Is .

Introduction of fish, an imals, or plants (native or otherw ise)is damag ing to the resources and is therefore

.

Dispose of all litter and debris properly.

our lake is a living biolog ical hab itat for thousands oforg anisms rang ing from alg ae to waterfowl and other animal life.In order to keep th is unique resource healthy and beautifu l, a fewsimple rules must be observed:

Mature Lake Edge WetlandsNaturally filtersout pollutants, with avarietyof plant life.

.

Water Quality Filter (prior to planting)Interceptsurban stormdrain runoff andfiltersout

pollutantsprior to lake discharge.

Lake Biofilter (prior to lake fill)Provides lakewater filtration andbiological nutrient removal.

Lake

Storm D rainOutlet

GravelLake

Gravel

DiffuserPipe

Soil forWetlandsPlanting

Copyright Pacific Advanced Civil Engineering, Inc. 2000©

MAINTENANCE / MONITORING: COMMUNITY EDUCATION

Operations Program for the Lake Involved Regular Scheduled Items

! Regular maintenance 3 days / week (4-6 hours / day)

! Primary maintenance duties– Debris Removal– Aquatic plant maintenance– Water quality treatments (algae

removal)– Lake water testing (monthly)– Mechanical equipment replacement /

maintenance– Biofilter backwash– Fountain water feature maintenance


Lake Operation / Maintenance Observations and Costs

! Chemical only used occasionally to not impact natural biologic processes of lake– Cutrine (algaecide)– Tripleline (defoamer)– Clearigate (herbicide)– Copper sulfate (control

algae growth)– Aquashade (filter sunlight

control algae growth)– Dimillin (mosquito and

midge control)– Microzyme (decomposition

and digestion of biomass sludge)


Lake Operation / Maintenance Observations and Costs

! Observations from lake operation– Application of herbicides

are more than 50% less normally required for lake this size

– Amount of “make-up” is only 70% of anticipated because of nuisance water reuse

– Primary maintenance item is floating debris/trash removal

! Operating Costs


$10,000/month($700/ acre ofLake)

Total O & M

$1,000/monthReplacement / Miscellaneous

$3,000/monthPower for Recirculation & Aeration

$6,000/monthMonthly Maintenance

LEGEND:Lake or water featureLandscaping areaLake wetland plantersLake water quality filtersLake biofiltersRoadsPaseo, Trail & Sidewalks

BridgeportValencia, CA

SANTA CLARA RIVER

BRIDGEPORT LAKE SYSTEMBRIDGEPORT LAKE SYSTEM

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Aquascape Provide Effective Solution for Stormwater Management

1. Exceptional water quality achieved far beyond traditional methods while adding value to community

2. Manmade lake system involves recreating natural system that relies on biological processes for treatment

3. Multi-function facility providing aesthetic / recreational amenity, stormwater conveyance, runoff treatment, and habitat enhancement

4. Efficient user of water compared to typical landscape areas5. Early integration of lake feature into site plan requires

coordination with all project consultants and stakeholder

SUMMARY / LESSONS LEARNED

Resorts / Pools / RecreationResorts / Pools / Recreation

Entry Features / FountainsEntry Features / Fountains

Flood Control / Stormwater Quality / WetlandsFlood Control / Stormwater Quality / Wetlands

Hydraulic Modeling / ResearchHydraulic Modeling / Research

WATER

RESOURCE

ENGINEERING

CONSULTANTS

Potable / Waste / Reclamation Water SystemsPotable / Waste / Reclamation Water Systems

Lakes / ReservoirsLakes / Reservoirs

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