Los Angeles Regional Water Quality Control Board, November 4, 2004 1 Total Maximum Daily Load for...

Los Angeles Regional Water Quality Control Board, November 4, 2004

1

Total Maximum Daily LoadTotal Maximum Daily Load for Nutrients in for Nutrients in

Malibu Creek and LagoonMalibu Creek and Lagoon

Melinda Becker and Rod CollinsMelinda Becker and Rod Collins

Los Angeles Regional Water Quality Control BoardLos Angeles Regional Water Quality Control Board

November 4, 2004November 4, 2004


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Nutrient ImpairmentsNutrient Impairments

Aquatic toxicity, generally related to Aquatic toxicity, generally related to nitrogen as ammonianitrogen as ammonia

Excessive growth of algae and vascular Excessive growth of algae and vascular plants caused by elevated levels of plants caused by elevated levels of nitrogen and or phosphorusnitrogen and or phosphorus– leads to low dissolved oxygen leads to low dissolved oxygen – Impairment of aquatic habitat Impairment of aquatic habitat – Impairment of recreational useImpairment of recreational use


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Malibu Creek Nutrient Malibu Creek Nutrient TMDLsTMDLs

EPA established Malibu Creek and EPA established Malibu Creek and Lagoon Nutrients TMDL on March 22, Lagoon Nutrients TMDL on March 22, 2003.2003.

EPA found that the evidence of algal EPA found that the evidence of algal impairment was less conclusive for impairment was less conclusive for winter time than during summer winter time than during summer conditions. conditions.

EPA established different numeric EPA established different numeric targets for winter and summer.targets for winter and summer.


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USEPA TMDLUSEPA TMDLNumeric TargetNumeric Target

Nitrogen and PhosphorusNitrogen and Phosphorus

WaterbodyType Summer Winter

TotalNitrogen

(mg/l)

TotalPhosphorous

(mg/l)

Total Nitrogen(mg/l)

Lakes 1.0 0.1 8.0Streams 1.0 0.1 8.0Lagoon 1.0 0.1 8.0


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Draft Regional Board Draft Regional Board TMDLTMDL

Staff’s focus has been to increase the Staff’s focus has been to increase the understanding of the impact of nutrients understanding of the impact of nutrients on excessive growth of algae and on excessive growth of algae and vascular plants and to refine the TMDL vascular plants and to refine the TMDL and allocations accordingly.and allocations accordingly.

Identified unanswered questions in EPA Identified unanswered questions in EPA TMDL and contracted special studies.TMDL and contracted special studies.


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Unanswered QuestionsUnanswered Questions

Is the Creek impaired due to excessive Is the Creek impaired due to excessive algal growth in the winter?algal growth in the winter?

What are the controlling or limiting What are the controlling or limiting factors for algal growth?factors for algal growth?

Do wintertime discharges contribute to Do wintertime discharges contribute to summertime impairments in the summertime impairments in the Lagoon?Lagoon?

Does contaminated groundwater impact Does contaminated groundwater impact surface water nitrogen levels?surface water nitrogen levels?


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Recent Studies Recent Studies

Survey of algal biomass and limiting factors Survey of algal biomass and limiting factors (SCCWRP /UC Santa Barbara)(SCCWRP /UC Santa Barbara)

Bioassessment in coastal watersheds (UCLA)Bioassessment in coastal watersheds (UCLA) Impact of wet weather discharges on Impact of wet weather discharges on

summer impairment in the Lagoon summer impairment in the Lagoon (SCCWRP)(SCCWRP)

OWTS Risk Assessment (City of Malibu)OWTS Risk Assessment (City of Malibu) Groundwater Evaluation under the Rancho Groundwater Evaluation under the Rancho

Las Virgenes Farm (Las Virgenes Municipal Las Virgenes Farm (Las Virgenes Municipal Water District, report pending)Water District, report pending)


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Importance of Benthic Importance of Benthic AlgaeAlgae

Prior surveys focused on floating algal Prior surveys focused on floating algal mats mats

New surveys employed more New surveys employed more quantitative methods and included both quantitative methods and included both floating and benthic algae (diatoms)floating and benthic algae (diatoms)


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Wintertime Impairment?Wintertime Impairment?

Wintertime impairment Wintertime impairment – Recent surveys that quantify benthic algae Recent surveys that quantify benthic algae

(diatoms) show wintertime impairment(diatoms) show wintertime impairment– Impairment for floating algae based on > Impairment for floating algae based on >

than 30 % cover (Biggs)than 30 % cover (Biggs)– Impairment for benthic algae (diatoms) Impairment for benthic algae (diatoms)

based on>60% cover (Biggs)based on>60% cover (Biggs)


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Factors that Stimulate Factors that Stimulate GrowthGrowth

Nutrients: nitrogen and phosphorus Nutrients: nitrogen and phosphorus LightLight CurrentCurrent Others: grazing, substrate, temperature, Others: grazing, substrate, temperature,

etc.etc.


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NutrientsNutrients

Nitrogen (N) and/or phosphorus (P) may Nitrogen (N) and/or phosphorus (P) may limit growth limit growth

N to P ratios predict limiting nutrientN to P ratios predict limiting nutrient– Ratios of < 10 N to 1 P, suggest Nitrogen Ratios of < 10 N to 1 P, suggest Nitrogen

limitationlimitation– Rations > 30 N to 1 P, suggest Phosphorus Rations > 30 N to 1 P, suggest Phosphorus

limitationlimitation– Between 10 and 30, co-limitingBetween 10 and 30, co-limiting

High levels saturate growth, neither High levels saturate growth, neither limiting without drastic reductionslimiting without drastic reductions


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Light as a Controlling Light as a Controlling FactorFactor

Recent studies show that light merely Recent studies show that light merely determines the type of algae present determines the type of algae present and does not impact total algal biomassand does not impact total algal biomass

Light promotes floating algae, but in Light promotes floating algae, but in shaded areas benthic algae (diatoms) shaded areas benthic algae (diatoms) flourishes if sufficient nutrients are flourishes if sufficient nutrients are availableavailable


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Current as a Controlling Current as a Controlling FactorFactor

Common wisdom suggested that high Common wisdom suggested that high currents sweep algae away. Therefore, currents sweep algae away. Therefore, algae not a problem during wet algae not a problem during wet weather.weather.

More true for floating algae, less true for More true for floating algae, less true for benthic algaebenthic algae

Benthic algae recovers quickly after a Benthic algae recovers quickly after a storm eventstorm event

Faster currents deliver more nutrients Faster currents deliver more nutrients to benthic algaeto benthic algae


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SCCWRP/UCSB StudySCCWRP/UCSB Study

In many areas nutrient levels were In many areas nutrient levels were saturated, thus drastic reductions would be saturated, thus drastic reductions would be required to limit algal growth.required to limit algal growth.

However, data suggest that the site below However, data suggest that the site below Tapia WRF is nitrogen limited during the Tapia WRF is nitrogen limited during the discharge prohibition period.discharge prohibition period.

In general, reducing nutrient In general, reducing nutrient concentrations would probably reduce concentrations would probably reduce benthic diatoms but have less impact on benthic diatoms but have less impact on floating macroalgae.floating macroalgae.


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UCLA Study: General UCLA Study: General TrendsTrends

In shaded areas bottom algae is more In shaded areas bottom algae is more abundant versus unshaded areas, and abundant versus unshaded areas, and positively correlated with phosphorus. positively correlated with phosphorus.

IIn unshaded areas floating algae is more n unshaded areas floating algae is more abundant versus shaded areas and abundant versus shaded areas and positively correlated with nitrogen.positively correlated with nitrogen.

In shaded areas high nutrients are In shaded areas high nutrients are correlated to poor conditions of aquatic correlated to poor conditions of aquatic invertebrate communities.invertebrate communities.


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Malibu Lagoon StudyMalibu Lagoon Study

Dense stands of Dense stands of Ruppia maritimaRuppia maritima results in low DO during dry season in results in low DO during dry season in western Lagoon.western Lagoon.

Nutrient levels in surficial sediment of Nutrient levels in surficial sediment of western portion of Lagoon are greater western portion of Lagoon are greater than some of the most eutrophic than some of the most eutrophic systems studied worldwide.systems studied worldwide.


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Update – LARWQCB TMDLUpdate – LARWQCB TMDL

Slide of lagoonSlide of lagoon


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Malibu Lagoon StudyMalibu Lagoon Study

Wet-weather discharges of particulate Wet-weather discharges of particulate TN and TP from Malibu Creek settle in TN and TP from Malibu Creek settle in the western Lagoon the western Lagoon

N and P from sediment is strongly linked N and P from sediment is strongly linked to excessive growth of R. maritima and to excessive growth of R. maritima and low DO in the Lagoon during summer.low DO in the Lagoon during summer.

Releases from sediment in the summer Releases from sediment in the summer represents 18% of TN and 5% TP total represents 18% of TN and 5% TP total dry-weather loading to the Lagoon.dry-weather loading to the Lagoon.


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Malibu Lagoon Study Malibu Lagoon Study

Deposition of particulate organic N and P Deposition of particulate organic N and P major source to sedimentmajor source to sediment

Diffusion of high dissolved inorganic Diffusion of high dissolved inorganic nitrate/nitrite from surface water to nitrate/nitrite from surface water to sediment only about 5% of loading to sediment only about 5% of loading to Lagoon sediment Lagoon sediment

Deposition occurs during episodic rain Deposition occurs during episodic rain eventsevents

Nutrient sources may result from stormwater Nutrient sources may result from stormwater runoff or instream sediment, instream algae runoff or instream sediment, instream algae or ocean sediment or ocean algae.or ocean sediment or ocean algae.


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Staff’s ConclusionStaff’s Conclusion

Based on the weight of evidence, Staff Based on the weight of evidence, Staff concludes:concludes:– The Creek is impaired for algae during the The Creek is impaired for algae during the

winter wet-weather seasonwinter wet-weather season– Wintertime nutrient discharges to the Creek Wintertime nutrient discharges to the Creek

and Lagoon contribute to summertime and Lagoon contribute to summertime impairments in the in the western Malibu impairments in the in the western Malibu LagoonLagoon

– Reducing nitrogen and phosphorus will Reducing nitrogen and phosphorus will reduce eutrophicationreduce eutrophication


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Staff RecommendationStaff Recommendation

Extend EPA’s recommended summer Extend EPA’s recommended summer time numeric targets of 1.0 mg/L total time numeric targets of 1.0 mg/L total nitrogen and 0.1 mg/L total phosphorus nitrogen and 0.1 mg/L total phosphorus to the winter season. to the winter season.


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Background - ImpairmentsBackground - Impairments

Map with nutrient concentrationsMap with nutrient concentrations


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Nutrient SourcesNutrient Sources

Tapia WRFTapia WRF Malibu OWTS and associated contaminated Malibu OWTS and associated contaminated

groundwatergroundwater Rancho Las Virgenes, historic sludge injection Rancho Las Virgenes, historic sludge injection

and associated contaminated groundwaterand associated contaminated groundwater Other OWTSs and potential contaminated Other OWTSs and potential contaminated

groundwatergroundwater Runoff from golf courses and other landscaped Runoff from golf courses and other landscaped

areasareas Runoff from livestock holding areasRunoff from livestock holding areas


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IssuesIssues

Potential Impacts of Recommended Potential Impacts of Recommended Actions on Tapia WRFActions on Tapia WRF– Reduced nitrogen and phosphorus load Reduced nitrogen and phosphorus load

allocation allocation 14.6 mg/L TN to 1.0 mg/L14.6 mg/L TN to 1.0 mg/L 2.6 mg/L TP to 0.1 mg/L 2.6 mg/L TP to 0.1 mg/L

– Investigate alternatives to Malibu Creek Investigate alternatives to Malibu Creek discharge, such as:discharge, such as:

Increased discharge at LA River outfallIncreased discharge at LA River outfall Ocean outfallOcean outfall


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Map of nitrogen contributing areasMap of nitrogen contributing areas


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Map of sludge injection areasMap of sludge injection areas


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Board DirectionBoard Direction

Staff is seeking comments and direction Staff is seeking comments and direction from the Board on:from the Board on:– General findings and conclusionsGeneral findings and conclusions– Additional studies Additional studies – Implementation time framesImplementation time frames– OtherOther


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QuestionsQuestions

Staff contacts:Staff contacts:– Rod CollinsRod Collins

(213) 576-6691(213) [email protected]@rb4.swrcb.ca.gov

– Melinda BeckerMelinda Becker(213) 576-6681(213) 576-6681mbecker @rb4.swrcb.ca.govmbecker @rb4.swrcb.ca.gov

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