Technical Supporting Document

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Biscayne Bny. Hoth Munisport and Black Point landfills are located directly on lll&cayne Buy and have been well documnnted to b« affecting surface waters. The.

Biscayne Bay Surface Water Improvement and Management

Technical Supporting Document Principal Authors:

Editors:

Richard W. Alleman Sarah A. Bellmund David W. Black Sandra E. Formati Charles A Gove Lynn K. Gulick

John D. Mulliken Joel A. VanArman

Other Coutributors; Debra 5. Burns

Robert Chamberlin Duane Piper

Dawn A. Reid Jose Valdes

South Florida Water Management District Planning Department

West Palm Beach, Florida November 1995

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BISCAYNE BAY SWIM PLAN 1995

TABLE OF CONTENTS LIST OF ABBREVIATIONS

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l. SYSTEM DESCRIPTION .. A. PHYSICAL FJflheMiamiHiver. .................

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TS-1

TS-13 TS-15 TS-16 TS-16 TS-17 TS-19 TS-22

TS-39 TS-40 TS-42

TS-97 TS-100 TS-113 TS-130 TS-146

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995

Pink shrimp ( Penaeus duorarum)

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Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 LIST OF ABBREVIATIONS Ag A,;

RBMC ROD

BNP IJMP

CARL

~ilver

arsemc

Biscayne Bay Management Committee Bwlogical Oxygen Demand Biscayne National Park Best Management PrRctices

Cd Cr

Conservation and Recreational Lands Comprehensive Development Master Plan Comprehensive Environmental Response, Compensation and Liability Ad colony forming units centimeter cadmium chronuum

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copper

DACS DDT DEHM

D.O. DR!

Department of Agricultural and Consumer Services dichlorodipheny ltrich \oroethane Mdro Dado County Department of Environmental Resources Management dissolved oxygen Development of Regional Impact

EAA EIS 10:!\'P El'A

Everglade~ Agricultural Area Environmental Impact Statement Everglades National Park gnvironmenlal Protedion Agency

FAC

Florida Administrative Code Florida Atlantic UniverHity Florida Department of Community Affairs Florida Department of Environmental Protection Florida Department of Environmental Regulation ~'lorida Department of Natural Resources Florida Department ofTransportation Florida Game and Fresh Water Fish Commission ~'lorida Inland Navigation District ~'lorida International University ~'lorida Keys National Manne Sanctuary Florida Marine Fisheries Commission !ril

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120 105

90 75

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TS-4.

Biscayne Bay Average Monthly

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~'reshwater

Canal Flows by Region_

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995

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lJeetc occurs along the shor.,line of Biscuyne Bay in anas such as Soldier Key, l':!liot Key, ;md Key Bi~cayne neur Bear Cut. In ~uch arcas the amount of rock surfuce exposed during the tidal cycle may be extemivc. Such natural rock subHtrate supports !1 widn nmge of sea life, including numerous bryozoans, hydroids, tunicates, anemones, gastropods, false limpets, chitons, mussels, sponges, clams, cchinodBrms, soft corals, snu urchins und crustacean~. Shrimps, crabs and occasional octopuse> live in shallow tidal pools 1Voss, 1976). Other rocky shores consists of manmade riprap, rock jeUi,s, and seawalls. Riprap shorelmes and jetties can have extensive crevices, holes and cavt'rns that provide substrate ;md shel!Rr for numerous intertidal organisms. l'opulalions or fiflBen common speci"s or juvtmilB fish wnre six to nine times higher along riprad shorelinB than along vertical!y bulkheaded shomline (Lindemann, unpublishc data). Vertical ~eawalls offer less surface area for the attachment of

Techmcal Supporting Document.

BISCAYNE BAY SWIM PLAN 1995 organi8mS and provide little or no protection from the effects of wave action. Communities that live on vertical seawalls tend to be more limited and consist of sponges, limpets, a few other gastropods and the isopod Ligea, with occasional oysters, mussels and corals. Submerged Aquatic Communities. Sea'Xasses. Seagrasses that are found within Biscayne Bay include turtle grass (ThG:assia tcstudinum), manatee grass (Syringodium filiforme), shoal grass (llalodule wrighth), and species of lfalophila. The standing crop of seagrass leaf biomass alone can exceed 400 giM2 (dry weight) or more than two tons of organic matter per acre (Hefty, 1993). Growth and dbtribution of sea grasses are controlled by light attenuation, photoperiod, temperature, salinity, and sediment type and depth: These grasses may be found as communities cum posed ofmonocultures, mixed gra8s species or in associt•tion with several species of green, red and brown algae. These habitat types comprise the major benthic plant communities in Biscayne Bay and are highly productive (Thorhaug, 1976). Benthic plant communities arc a major source of primary productivity (Thorhaug, 1976). In addition, the root mass of these plants serves to stabilize the sediments. Their leaves create resistance to water currents and promote water clarity, trapping suspended sediments and providing habitat and shelter for a wide variety of benthic organisms (Metro-Dade County Planning Department, 1986). Species diversity and densities of organisms per square meter can be very high. Numerous species of small shrimp, crabs, worms, clams, snails, and echinoderms inhabit these areas with commercial species such as shrimp, stone crabs and lobsters (Milano, 1983). Grass beds tend to be very stable in Biscayne Bay and exhibit the highest production during the summer (Hefty, 1993). Adequate transmission of light to s~agrass and algal communities is essential for their survival and growth. The amount of light penetrating the water column is controlled by water transparency and depth. In Biscayne Bay this relationship has been modified due to the reduction in water clarity from suspended matter, so that deeper areas such liS dredged portions of the bay cmplubians occur in upland drainages and coastrine mangrove habitat and nests on sand beaches and banks. Terrapins have a lacrymal {tear) glaoil thal helps them to survive in saline environments by secreting saiL. This gland is not as effective as that of sea turtles, however, so they are noL entirely independent of fresh, or reduced ~alinity, water. An additional specialization is tbe presence nf interstitial sacs in various parts of the body for storage of water. The legs of terrapins visibly swell from filling of these sacs after drinking fresh water. Terrapins seem better able to ut!lize high salinity habituts, including salt ponds, than the mangrove water snake and the crocodile ging stmtegies are divided into open water feeding during !light and while ~wimming, parasitic or predatory feeding, fon>ging long the hay margin, and foraging in the 11djacent h11hitats in coastal wetlands and upland areas. Birds that fnrag., primarily in t.he open water of the hay while swimming submurgod include cormorants (Phalacrun;rax sp.J, mergansers (Mergus sp., 1-uphvdyteo ~p.), coots (Fuhca sp.J and diving ducks (subfamily Aythyinae). Food sources for these birds include fish, invertebrates, plants, and animals. Birds that forage by plunging from flight to catch fish from the upper layer of surface waters include pelicans (Pelecanus ~p.), ospreys (Pandirm haliaetu.>), terns (subfamily Stnrninae) nnd kingfishers (Me;;acer:rle alcyon). The black skimmer (Rynchops mgra) catches small fish and macroinvmtebrates with its highly specialized kmfc-hkc bill which slices through the wat.er as the bird flies just above the surface. Birds that primurily uiihze airborne foraging stmtegics (picking up food over the bay or land) include bald eagles (llaliaeetus leucocepha/us) and frigatebirds (Fregata mou>u{ic,'ns). Gulls (Larus spp.) arc ubiquitous in the bay and surrhhling ducks (subfamily i\natinal 1!Jil3-N ovr I!Jil2 • -""" m; llJ' :10 hoab. Snum>. !le~keley 1981_

commercial catch from the bay (excluding lob~ter and Hpong(>H) waH worth about $2.7fi million for the period examined. These figure~ include only the dockside value of t.he commercial fish, and do not take into account income which is generated within t.he fi~hing industry it&df or from sport fishing_ Pmk shrimp is the most important speci"" harve~ted (by weight} in Biscayne Hay, accounting for 29% of the total recreational harvest. Gray snapper, white mullet, pilchard (scaled sardine}, white grunt., and ~potted scatrout arc the five most abundant finfish harvested rccrter re~ources of South Florida to ensure their availability for future generations; Provide for the equitable, orderly, cost effective and economically feasible development of water supplic~ to meet South Florida's agricultural, urban, industrial, and environmental needs; and lmprnvH local and regional resource mnnagemcnt decisions through integralion of regional and local water supply plans and land usc planmng.

The final plan will provid~ a set of technical data, assumptions and selected water supply alternative& thai will provide guidance for local government water resource programs such as comprehensive planning, utility planning and land use decisions. Florida Keys Area of Critical State Concern Plan. The ~'loridu legislature designated an area encompassing most of the Florida Keys an area of critical state concern in 1~)80. The purpose of this designation is to provide mechanisms that will conserve and protect the natural, environmental, historical and economic resources of the region including the scenic beauty and ihe public facilities. Rules contained in Ch. 28-2H F.A.C. requires that a plan be developed that may include recommendations for new regulations that arc needed to preserve water quality, optimization e>f water resources use and to facilitate an orderly and well-planned development that protects the health, welfare, safety and quality of life for residents oft.he state. 4. Local Plans

Dade County Comprehensive Plan. The Dade County Bourd of Cnmm1ssioncrs adopted a coastal management element of the ComprehensiVe llnvP)opment Master Plan in December 19H8. The coastal element also includes the lme so severe that local citizens and the county began to ,;olicit help from state and federal programs. Sev
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IZQJ SWIM

BOUNDARY

Sites Used to Burn Solid Waste After Hurricane Andrew.

Tnchnical Supporting Documenl

BISCAYNE BAY SWIM PLAN 1995 the lack of cmpetition. It may be decades before the red mangrove forest fully recovers. Acres of dama~ed pinelands and hammocks may also be susceptible to similar problems of invasion by undesirable exotic species.

Limited, mostly single event, water quality monitoring was also conducted by the Metro-Dade DERM, the SFWMD and the National Park Service. No comprehensive post-hurricane monitoring program was in place, nor were resources available to carry out such a program. Transportation was limited, personnel were generally allocated to more immediate needs and funding was not available. The use of SWIM funds was particularly inflexible. It b~came apparent that appropnate contingencies had not been built into budgets. ~'urthermore, very little cross training existed between the agencies for the monitoring programs in place. A substantial amount of interagency cooperation occurred, but without detailed knwledge or written descriptions for the local monitoring programs, it was impossible for outside personnel to follow the protocols and locate monitoring stations. The lack of useful post-storm data from the walcr body most affected by the storm shows that activilies need to be thought through and priorilized beforehand. Future scenarios of such an event will likely be similar in the limitation of resources, transportation and communication. There is a clear need to set priorities in advance and form agreements among responsible parties. Floods. ~'londing can affect Biscayne Bay in twc> ways. Large doses of freshwater discharged through the canals and into the bay can cause destruction of the benthic communities such as seagrasses and hardbottom corals and sponges through the toxic effects of low salinity. Secondly, the flooding of urban and agricultural areas can deposit destructive debris and pollutants. An example of impacts that can occur from too much freshwater occurred in August 1988 at the Acrojet (C-111) Canal. This canal terminates at Manatee Bay, a semi-enclosed basin within Barnes Sound. The low tidal range and long Hushing times make this bay vulnerable to the effects of large fresh water inflws. Such pulses of fresh water tend to form units or masses that persist for long periods of time and move within and between the shallow estuaries that make up Biscayne Bay and its associated sounds (Chinn Fatt and Wang, 1987; Wang and Van de Kreeke, 1986). Unfortunately, low tidal range and long flushing times also make Manatee Bay and Barnes Sound vulnerable lo hypersaline conditions during periods of reduced freshwater flow. It is important that this area be carefully managed for fresh water input.

'I'S-68

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 2

Hydrologic Alterations

Introduction. Releases of water from coastal canals occasionally create local problems due to transfer of fr.,sh water, ch.,mical pollution and suspended materiuls from urbun and agriculturallandH into the coastal waters and estuaries. Problems of this type of operation are especially apparent where water is discharged from restricted outflow points (such as pipes and the mouths of canals) into a semi-enclosed estuary, such as Biscayne Bay at unnatural times ofihe year. Other problems occur due to reduction of fresh water flows during the dry season and droughts. The network of canals in South Florida was designed to provide for flood control by moving large volumes of water away from from the developed urban and agricultural areas. The existence of these facilities has resulted in the flow of freshwater out of wf'tlands and flood-prone upland areas toward the coast and into Biscayne Bay. The operation of the canal system changes the spatial and temporal distribution of both surface water runoff and ground waL 40 ppt) in inshore areas when no Willer is released from the eanals, followed hy periods of very low salinity when large volumeH of freshwater 11re discharged from the canals. During dry periods, salinities near the shore increase, and these areas are colonized by marine species_ Hapid

'l'S-70

Techniclll Supporting Document

BISCAYNE BAY SWIM PLAN 1995 reduction in Rahnitics occurs when fre"hwatcr ib dibcharged from the canals and damages the marine communJticb, and yet these discharges frequently do not continue long enough to provide an estuarine habitat. Restoration of fu vorable hydreperiods in the coastal arum; could establish more productive conditions and benefit the native fauna. A better hydroperiod would provide for a seasonal reduction in balinity dming the wet season to support brackibh or freshwater habitats that are necessnry for the early life stage" of marine and estuarine organisms and a seasonal ris" in salinity during the dry season that would favor the growth and dev.,lopment of juvenile and adult marine organisms. One of the challenges of restoring hydroperiods or modeling flows is the lack of lopographk elevation data for the Biscayne llay watershed. Current data has a resolution of five feet_ Contours this grnss are extremely inadequate where a few inches difference in elevation may have a significant impad to hydrology, especially in South Dad., County. Minimum Flows to Bis.,ayne Bay, In Chapter 373.042, ~'lorida Statute~, the SFWMD is mandated to establish minimum flows and lllvels for water bodies within its jurisdiction. Although the concept of minimum l"vels does not apply to a tidally controlled lagoon such as Biscayne Bay, minimum flows should be determined as a means to protect "nvironmental resourc!ls within the system. Insufficient information presently "xists to set definitive minimum flows for this cnmplex ecosystem, but this plan identifieb the major issues and defines methods to address them_ Strong and quantifiable links need to be established between the presence or absence of desirable ecological features and the quantity, distribution and tuning of freshwater inflows in order to establish mmimum flows for Biscayne Bay. The definition of minimum flows and levels is a complex legal issue, but the underlying concept is relatively simple. This discussion is aot a legal interpretation, and does not constitute the official position of the SFWMD with regard to the meaning of minimum flows and levels. Ongoing legal research and case law in B'lorida or elsewhere may significantly change concepts of minimum flows and levels McanwhilH, decisions that affect flows to natural systems such as Biscayne llay must be made and a working concept is needed to guide agency actions until definitive minimum flows can be establishelL Natural systems arc adapted to certain p;lt!Rrns of freshwater inflows. Changes in inflows can change and degrade these sy~tems, The purpose of setting minimum flows is to avoid diversions nfw;1t"r that may cause significant degradation of natural areas. On the other hand, the need to avoid bignificantly damaging natural systems is not the only consideration in determining flows to natural areas. Many other statutes, rul.,s, and policies relate to wakr deliveries to natural systems. In many situations, the SFWMD delivcm far more than the minimum, as in wetland r"storation programs. In pnrticular cases the SFWMD may nttempt to supply optimllm qunntities of w11ter for specific environmental purposes such as providing the best possible end11nger"d Hpecies habitat_ In other cases restoration of certain areas to pre-development hydrologic conditions may be the objective. In lnHs extreme cases the SFWMD strikes a balance between benefit" of environm.,ntal enhancement and other objectives such as flood protection and providing water for other beneficial uses. In these situations the limited conc.,pt. of minimum flows and levels is not of critic3l importance because deliveries 11re well in excesH of the minimum.

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 Since Biscayne Bay is a very important natural system and a SWIM priority water body, most of which lies within a national park, it is a candidate for enhancement and restoration. However, the heavily urbanized nature of much of the watershed makes this an objective challengmg to obtain. Thus, determination of minimum flows is necessary but only one of a series of required steps. A solid understanding of the relationships between freshwater inflows, salinity, and environmental responses is required in order to establish appropriate flows. The S~'WMD will first utlempt to determine desirable hydrodynamic und water quality (including salinity) and ecological patterns for the bay and quantify links between these conditions and freshwater inflows. The next task will be to attempt to establish delivery schedules that equal or exceed the minimum needed to maint~1in these patterns. With this information, the agencies can not only avoid damage to Biscayne Bay but also make informed decisions to manage the system for positive environmental benefits. The SWIM planning process is an important tool for accomplishing this task_ Management of ecological systems in South florida must consider the substantial natural variations in hydrological conditions between ~easons and between years_ I>:cosystems in this region are not only tolerant of such variation, they often 5eem to depend on it to maintain their structure and productivity. Thus, interpreting the concept of minimum f1ows and levels in a simple, absolute sense could create serious environmental problems. For example, water deliveries to ENP across the Tamiami Trail were at one time regulated by a minimum delivery schedule that chunged by month but was independent of variation in rainfall from year to year. Better results have been obtained with a more complex schedule that is adjusted on the basis of actual rainfall measurements. This rainfall-based approach more closely matches the natural situation where flow would have occasionally stopped entirely. Although discussions by biologists and hydmlogists about the ideal delivery schedule for ENP are ongoing, there is general agreement that the answer lies in some kind of modified rainfall formula and not in a minimum delivery schedule. The same concept would presumably apply to other biological systems in the region, perhaps even Biscayne Bay, since under natural conditions they would all have been influenced by the large variations in rainfall from year to year. Consideration of minimum flows to Biscayne Ba! cannot be separated from the issue of spatial distribution of inflows. In genera , flows to the bay are now concentrated at the mouths of canals. This situation makes large flows more disruptive by creating zones of fresh water around the outflow points during high flows. In uddition, during periods of moderate to low flow, discharge from canals is probably less beneficial than the natural delivery pattern that spread out much of the fresh water into the coastal wetlands_ 'l'he concentrated discharge has more tendency to flow out into the bay rather than creating a salinity gradient in the wetlands and more favorable salinity conditions along the shore. Modification of the spatial pattern of discharge could increase effective flows to the important marginal wetlands without any increase in total flows to the bay. Understanding the complex relationships between freshwater inflows and in the bay will require both additional data \:ollection and analysis of available data_ The existing water quality monitoring network was not designed to address this issue. Stations are mostly lo~,ated either in canals, at the mouths of cunals, or well out in the hay. l'art.icularly in the Biscayne National Park area, there is need for salinity information away from the mouths of canals but within one mile of the western shon1, and also back in the fringing mangrove wetlands. These are the areas that probably had reduced salinity before the early 1901Js when sheet 11ow and ~alinity

Technical Supporting Oocument

BISCAYNE BAY SWIM Pl.AN 1995 ground water contributed much frc~hwatcr to the bay. Even with the modern water management system, a strong ~alinity gradient can build up on the southwest oide of the bay during wet periods as reported by de Sylva and Scotton (1972)_ ThiH shallow and poorly flushed part of the bay is also subject to hypersalinity during dry seasons. Monitoring salinity in the critical ~horeline environment and determining how it varies with changes in canal inflows to the bay is an important part of und!l usage of such areas in Biscayne Bay during dry and wet years would sh"d light on the importanc" of freshwater inflows. An especi~lly valuubh> exp; use has been restricted'! Coliform bacteria are indicators of pollution by sewage. Although these bacteria rarely produce serious disease themselves, they indicate thfl possihle presence of more dangerous microhes. Monitoring data confirm that there is a serious chronic sewage contamination problem in the Biscayne Bay system. Most of the stations in tributaries to the northern bay, and some in tributaries to the south, show high coliform values compared to public health standards. Lower counts in the bay itself are not great cuse for comfort, since coliforms are rapidly killed in saltwater while some of the pathogen~ found in sewage ur~ men: reHist '"

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Pathogens. Many pathogens, includmg viruses, bacteria, fungi, and parasites that can n>use human disease, are found naturally in marme environments. Pathogens howevf'r often are dischurged from combined sewage overflows, municipal treatment plants, and runoff. The amounts and types of pathogens in discharges vary with the health nf the human population in the ca1chment areu. While some bacteria like coliforms which

TS-77

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 arc associated directly Wlth feces may occur in relatively constant numbers, those associated directly with medical conditions ranging from nematode worm infections to viral diseases can only be introduced from existing human re~ervuir~. By and large, pathogens are adapted for life in the human gut, and so estuarine systems such as Biscayne Bay provide poor habitat. The rate at which pathogens die off varies, however, according to a number offactnrs including sunlight, temperature, salinity and starvatinn and the phlsiological stale of Lhc Orf(anism itself (Gamcson 19831 In estuaries, the dilution o seawater by freshwater may decrease mortality ral
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Figme TS-20. Water Quality Monitoring Stations in the Southern Portion of the Biscayne Bay Watershed

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Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 the data by parameter and station were checked viRually. 'I' he test wa~ not conducted on data sets with less than three years of monthly results. 'rhirteen paramet~rs wew evaluated for temporal trends.

Dissolved Ox,rgen. Average dissolved oxygen m.O.) in Biscayne Bay during the collection perio ranged from 1.6 mg/L (TM08) to 8.0 mg/L (GL03) (Figure B-3 and B-4). In general, dissolved oxygen concentrations vary with temperature and time of day. Higher temperatures tend to reduce the amount of dissolved oxygen. Since sunlight stimulates the growth of plants that produce oxygen, the highest concentrations tend to occur in the afternonns and the lowest levels occur late at night or early in the morning. Dissolved oxygen concentrations should average at least 5.0 mg/L for healthy systems. The State water quality criteria (17-3.02 ~'.A.C.) for Class 3 waters reflect this. All of the surface water monitoring stations were located in Class 3 waters. Ground water within the Biscayne Aquifer is normally very low in D.O. concentration, and, because of the high degree of interaction between ground water and the surface water in the canals, it is not unusual to observe lower D.O. concentrations in the canals. Averuge D.O. (one meter depth) W!l~ less than 5.0 mgiL at thirty-eight percent of the m1mitored stations and twenty-five percent were below 4.0 mg/L_ All of the averages in th" latter cat.,gory were located within the tributaries. Water at marine stations in the bay itself was well oxygenated and met Class 3 standards. D.O measured near the bottom was evaluated for trends, because these values were more stable than measurements from the water column, and were more likely to have hffects on the biota. Twenty-three stations had a significant trend {Figure B-31). The stations were di~tributed throughout the bay and seven tributaries. All of the trend~ had a positive slope except for Wagner Creek {WC01). Bottom D.O. concentrations at Station WC04 declined from 1988 to 19fJ2. Turbidity. Median turbidity ranged from 0.5 Nephelometric Turbidity Units (NTUl {llll42) to 7.0 N'I'U (LR02) (lo'igure B-5 and B-6). The State water quality criteria sets the maximum at 29 N'l'U above background. Eighty-three percent ofthe monitored stations had median turbidity below ::1.4 NTlJ_ With the exception ofGL02 {Goulds Canal), the highest median turbidity occurred at the stations within the northern bay and tributaries. Turbidity at thirty-five stations changed significanlly within the period of record. Eighty-three percent of the trends were negative (Figure B-32). Turbidity increased, however, at six statinH_ All of these stations were locat.ed within tribuk'l.ries and included the Bbcayne Canal (BS04), Miami River (MR04 & MR05), 'ramiami Canal (1'M03), Black Creek (lltOlJ and Goulds Canal (GLO~l-

TS-84

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 Color. Color was measured at a total of 100 stations. Average color ranged from 2.5 Platinum Cobalt Units (PCU) (many stations) to 60 PCU (many stations). Average V ulu~s for color for the Period of R~C(>rd !lfe shown in Figures B-7 and B-8. Thirty percent of the means fell below 5 PCU. Thirty·fivc percent of the means wen1 between 5 PCU and 14.9 PCU and thirty-five percent were greater than 14.9 !'CU. One or more monitoring stations in ev.,ry tributary had a mean value in the highest category. Mean color V!llues in the bay were lower, but the means were higher in the northern portion of the hny. Thnre is no color critnrion for surface waters.

a o mnans were m the upper portion ofBiscay'ne Bay· Four of the means were especially h1gh. These were located in the Miami River {M1W7; 1..1). Little River (LR03; 1.3), Wagner Creek (WCO~; l.6) nnd Goulds Canal (GL02; 1.7). Ammonia Nitrogen. Ammonia nitrogen (total) concentrations were measured at a total of seventy-eight stations since 1979 (noncontinuous). Median ammonia nitrogen concentrations ranged from 0.03 mg/L (CD02) to 0.96 mgiL (GL02) {Figures B-11 and B-12). The State water quality criteria does not set an absolute value for ammonia concentrations except for freshwater. Unionized ammonia cannot exceed 0.02 mg/L in freshwater. Dade County. however, has established a maximum concentration of 0.5 mg/L total ammonia nitrogen for surface walmd Goulds Canal (GL02; 0.96 mg/L). Fifty-one percent of the median concentrations fell below 0.10 mg/L, thirty-three percent were between O.l-0.29 mg/L and fifteen percent were more than 0.29 mg/L. Except for one station in Manatee Bay (BB5l), the highest ammonia nitrogen concentrations all occurred within the tributaries. Median ammonia nitrogen concentrations at the bay monitoring stations ranged from 0.05 mg/L to 0.10 mg/L. Ammonia nitrogen concentr>llions changed significantly at eleven stations during the period of record. All of these siatit were greater than or

since \988. The 60 mglkg (mouth of percent of the values .5 mglkg. ~'our percent of

PEL.

Chromium. Chromium concentratwns were determined in 105 samples and ranged from less than detectable (many stations) to 1077 mglkg (Miami River). Sixteen percent of the values exceeded the recommended NOEL of 33 mglkg. One sample exceeded the recommended PEL of240 mg/kg. Cop};er. Copper concentrations were determined in 269 samples and ranged from less t an detectable (many statinns) to 790 mglkg (Miami River). Forty-seven percent i>f the sample results exceeded the recommended NOEL of 28 mglkg. Seven percent of the values Wtlre equal io or greater than the PEL of 170 mglkg. Lead. Lead concentrations wem determined in 287 sediment samples since 1988 atidranged from less than detectable (many stations) to 2450 mglkg (Miami River). Most of the samples (62 %) excfleded the recommended NOF;L concentration of 21 mglkg. Twenty-four percent of the sample results equalfld or exceeded the rflcommended PEL concentration of 160 mglkg. concenirution was dt1termined in 162 samples and ranged 1 (m!my stations) tn 18.3 mglkg (Aerojet Cunal). Forty-four excet1ded the recommended NOEL nf 0.1 mglkg. Thirty-nne ;;-,;~;;;,!;results were equal to or greater than the recommended P~~L nf

Silver. Silver concentration was determined in 41 samples since 1988 and ranged from less than detectable (many stations) to 0.08 mglkg (Barnes Sound). All of the samplt1 results were below thfl recommended NOEL of0.5 mglkg. llinc. Zinc concentration was detnrmined in 27fi Smpounds} ranged up lo 57.1:\ mglkg (Sunset Harbor Marina). The recommended NOEL for total PA!Is is 2,900 mglkg.

Storm water. Stormwatcr is the rainfall runoff that is generated after a storm event_ H has been nationally recognized as a main source of non·point pollution to surface waters. The U.S. Environmental Protection Agency (El'A) co!lected a baseline evaluation of stormwater chemistry data in the National Urban Runoff Program and reported it in 19ll3. Non-point source pollution is usually associated with land use activities that do not have a discrete point of origin. The issues associated with stormwater runoff arc primarily those of volume of flow, rate of flow, and water quality. Early management of stormwatcr consisted of routing it to storm sewers and receiving water biJdies as rapidly as possible. In the early 1970s it became apparent. that this was having a severely detrimental effect on water quality of receiving surface waters. Stormwater impacts are generally calculated based upon the type of land use in the basin. Storm water runoff from residential, industrml, commercial, and agricultural land uses are very different and have different chemical characteristics (Whalen and Cullum, 1988). The quality of stormwater runoff is dependent on the land use from which it originates_ Stormwati!r from residential 11reas carries contaminant loads indicative af this land u~e. Thi! qualit; of resid(mtial stormwater primarily depends upon the intensity of development, w 1ethcr onsite disposal systems are utilized or regional sewage treatment and the amount of landscaping maintained in the areu. Industrial land use carries such contaminants as metals, organic chemicals, or other products related to the main manufacturing processes in the basin. Runoff from roads is a major snurce of ~uspendHd solids, lead, ~inc, gasoline hyproducts, and polynuclear aromatic hydrocarbons Stormwater runoff from agriculture carries pollutants such as fertilizers, pesticides and other chemicals. The land usc for the study area is depicted in Figure TS-21 for the northern portion of the study site and in Figure TS22 for the oouthern portion of t.he planning area. Due to the identification of known non-point pol!utant sourc ~

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ften caused the buoyant samplers to tip over and occasionally damaged electronic parts. Nonetheless, data from two of the monitored basins have been summarized to date. Table TS-14 indicates that, while the contaminants from storm water runoff appear typical compared to National Urban Runoff Program data, a s1gnificant volume of nutrients, trace metals and other pollutants were entering the Miami River via stormwater runoff. This monitoring was conducted before the sy&tems were retrofitted with treatment devices. Table TS-14. Result~ Repurled from 1989 Storm water Monitoring in Two Basins in th C't fM'lflml'thtOtfllt0 th M'tam!·n·tver. Bas1n 50 Basin 26 Bas1n 26 Basin Basin Basin 50 Median Median Average Average Parameter (units are mg/L 50 Event Event except Turbidity) No.of Loading/E No.of loading/ Mean Mean vent (kg) Events Event(kg) Eveflts Cone. Cone

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A total of 168 bacteria samples have been collected from seventeen stonnwater basins in the City of Miami. This tldivity has been llf'!'ective in demonstrating the degree of contamination from sanitary sewage and other sources with high concentrations of bacteria and has lnd to many enforcement cases. Eighty-one percent of the coliform bacteria samples collected violated a water quality standard and 16 of the 17 basins were aiTected (Markley, et al., 1990). A project to characterize surface water effects of storm runoff by rapid sampling during storm events was completed by Metro-Dade DEHM. SampleH wem collected from the Miami Canal from the salinity control structure upstream to the Florida Turnpike Extension. In general, the degradation of water quality observed following a storm evc I'"'' I"""" tll "~'' of l.ws wol.b l.hc ~., "''" ' onf,dcnce 'to I erv,ll '" prov 1 uJdY, 1\,l'di ne pork, 1976; Smith ct a/., 1950; P. Molar, personal cornmunic&tion). In addition, manr.;roves protect the coast from the effects of hurricanes. Thayer c1 al. (1987) found that mangrove prop root habitats m Florida Bay were impurtant tu thP. life history of the grlly snapper (Lu(ianus ,;riseus) and other species, and that 68% of the wet weight biomass of gray snappers was obtained from mangrove habit.at. Dade and Monroe countws contain areas of both mixed and dominant mangrove forests. Mangrove communities are nece~sary for the integrity of the coastal wetland system but are not adequately protected from development. The benefits pnJVidf•d hy these phml. communities tend to be devalued or undervl!lued whun dedsJOns are made tu dredge and fill col!stal wetlands for th., purpose of development. CoaHtal wetland communiti"s provide benefits of water quality tr~atment, biological diversity, flood control, and hurricane protection, that are either perml!nently lost from the system or have to be replaced through expensive additional construction or mitigation. Currently Dade County codes and ~'DJ•:P rules regulate trimming and sum., destruction of red, white and black m!mgroves. However, destruction and removal of these communities still occur, duP. primarily to heavy development pressure. In additirm, water tables have bilen lowerod by development and sheet flow of freshwater from the uplands has bnen converted to channelized flows and the timing of these flows has been altered by the construction of canals and levees parallel to the coast. These changes huve resulted in decreased integrity of mangrove ecosystems, decreased ability to filter pollutants, loss of nutrients to the bay, loss of habitat, and th(• redu~ed ability of mangrove communities to further assimilal!• changes.

'l'S-123

Technical Supporting Document

BISCAYNE BAY SWIM PLAN 1995 Marshlands. Prior to construction of the coastal canal system, marshes along the shore of lliscayne Bay were dominated by fr.,shwater ~pecies. '!'he fringe forests. currently dominated by mangroves, contained fre.ohwater species prior io the artificial reduction of fr.,shwalcr flow (Teas, 1976). The area westward of the mangrove fringe was dominated by marsh grass (Juncu.~ roemerianus and Dtslichl1s sp•cata) and then sawgrass (Cladiu.m Jamo•censis) marshes (Teas, 1976). Many freshwater plants still persist in coastal marshes, due, perhaps tt> seepage t>f ground water from the Biscayne Aquifer. In other areas, however, the coastal canals and levees have cut off the now of freshwater and saline vq-:ctalion has replaced the freshwater plants (Teas, 1976). In some areas, especially in South Bay and Card Sound, the flow of freshwater, combined with poor tidal exchange has created hypersaline soils that can maintain litUe vegetation with the exception of stunted mangroves. Saltmarshes are not abundant in Biscayne Bay, pmbably because thc5e communities tend to he invaded by mangroves. Growth of mangroves eventually shades out and eliminates the understory of marsh vegetation.

convey arc exotic wetland and Bra~ilian pepper. AlthouJh these change and . , the invaded areas are still va uable, since they continue as wetlands. 1

Coastal Ut\and Habitats. Uflands m th

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