Response to December 18, 2003 RWQCB comments on Preliminary Water Quality Screening Plan -
Lake Merced Stormwater Enhancement Project

January 12, 2004

North San Mateo County Sanitation District (NSMCSD), a subsidiary of the City of Daly City, and the San Francisco Public Utilities Commission (SFPUC) are working to address a number of integrated resource management issues associated with improving water levels at Lake Merced.  A Memorandum of Understanding between the parties dated November 26, 2001 established a work effort to assess the reintroduction of stormwater from the Vista Grande drainage basin back into Lake Merced as a source of lake recharge.  A proposed Supplemental Environmental Project (SEP) (NSMCSD 2003) would expand upon NSMCSD’s efforts to evaluate the feasibility of using diverted Vista Grande stormwater as a means to increase source water to Lake Merced.  The ultimate goals include implementing Best Management Practices (BMPs) to treat stormwater, increasing the water level of the lake and potentially alleviating flood control problems associated with peak stormwater flows adjacent to South Lake Merced.

On December 8, 2003 the NSMCSD and SFPUC transmitted a Preliminary Water Quality Screening Plan, 2003/04 Wet Season for the Lake Merced Restoration - Phase 2 Pilot Stormwater Enhancement Project (Plan) dated December 2003 to the SF Bay Regional Water Quality Control Board (RWQCB) other interested parties for comments.  RWQCB transmitted comments on the Plan to the NSMCSD and SFPUC on December 18, 2003. Responses to the RWQCB’s December 18, 2003 comments are included below.   

In addition, this document includes a response to RWQCB comments on NSMCSD’s Supplemental Environmental Project (See Appendix A).

Concurrently, the Plan was peer reviewed by Dr. Robert Cooper, Emeritus Professor of Pubic Health at the Univ. of CA, Berkeley.  Dr. Cooper’s comments are dated December 26, 2003 and are attached to this response. Dr. Cooper states, "The methods in the plan appear appropriate to give a preliminary indication of whether there would be a water quality impact due to the pilot diversion."  He also notes the results will be used in the development of a strategy to "scale up" the pilot diversion and design of a future associated monitoring program.  Perhaps his review is best summed up by Dr. Cooper when he states: "Introduction of Vista Grande stormwater to Lake Merced requires consideration of the tradeoff between the potential environmental benefits of adding additional water to the lake and the potential risks such as human health impacts.  The pilot study appears to be an appropriate first step in gathering information required to make an informed decision regarding the balancing of these two potential conflicting priorities." 

Existing and Potential Beneficial Uses of Lake Merced:  While the RWQCB’s Basin Plan lists both Water Contact Recreation and Non-Contact Recreation as existing uses, it is important to understand that swimming has been prohibited at Lake Merced since at least 1950 by SFPUC Resolution and practice. Fishing and boating are the only two potential water contact activities allowed at Lake Merced pursuant to SFPUC and SF Recreation and Park Department requirements. The SF Health Department supports the prohibition of body contact recreation at Lake Merced.  Therefore, the bacteriological criteria applicable to body contact recreation utilized for this pilot project (CCR Title 17, Article 4, 7958 and RWQCB Basin Plan) is highly conservative and provides a significant factor of safety.

Lake Merced is designated by the RWQCB as a potential source of drinking water and by the SFPUC as an emergency drinking water source.  However, it has not been used as such since the 1930’s and does not meet drinking water standards. In the unlikely event that the lake is ever needed for an emergency water supply, the SFPUC would issue a “boil water” order.

RESPONSE TO RWQCB COMMENTS

1) Comment: The proposed Plan appears to be generally directed at the human health threats of coliform and does not adequately address other priority stormwater pollutants of concern appropriate in a baseline study of this nature.  Along with the proposed sampling analysis parameters, the following additional priority stormwater pollutants of
concern should be included in the Plan: Petroleum hydrocarbons (normally EPA 8015 and/or 8020), 17 priority metals (CAM 17); Fecal coliform; and a limited screening for candidate pesticides/herbicides.  Lastly, we strongly recommend use of ammonia and nitrate field kits which can indicate high coliform levels and provide immediate results.  

Response:  The monitoring parameters selected in the Plan were based on a review of Vista Grande Stormwater data from 8 representative storms sampled during the 2002/2003 winter (CH2MHill, 2004) and an analysis of stormwater data by EDAW (Aug. 2003) which indicates that bacteria and nutrients are the primary pollutants of concern relative to the discharge of stormwater from the Vista Grande Canal into Lake Merced and protection of beneficial uses.  The Plan was thus designed to monitor the primary pollutants requiring treatment (i.e., bacteria and nutrients).  In addition, the Plan included analysis of the five most common metals detected in typical municipal stormwater (Cr, Cu, Ni, Pb, and Zn), as well as Total Dissolved Solids, Total Suspended Solids, alkalinity and hardness.

These monitoring results are summarized in a January 2004 report titled: Phase 1 Vista Grande Stormwater Monitoring Program prepared by CH2MHill. We understand that the CH2MHill data was not provided in the original submittal and thus Regional Board staff was not fully aware of the extent of the previous 2002/2003 monitoring program.  The SFPUC has previously submitted the EDAW (Aug. 2003) report to Regional Board staff.

A summary of the Vista Grande Stormwater Canal 2002/2003 Phase 1 monitoring results and specific responses to RWQCB recommendations are included below:

Pesticides and Herbicides:  Stormwater was sampled during 5 of the 8 storms using EPA methods 8151 and 8140 Organophosphorous Pesticides and Chlorinated Herbicides. None of the analytes were detected above the method detection limit in any of the ten samples. Therefore, additional sampling for pesticides and herbicides does not appear warranted.

Total Petroleum Hydrocarbons: Stormwater was sampled during all 8 storms using EPA methods 8015.  Of 16 samples collected, only two had levels above 1.0 mg/l (one each at 2.6 and 1.5 mg/L). Given that USEPA’s Stormwater Benchmark for Oil and Grease is 15 mg/l, we believe that additional sampling for TPH is not warranted at this time. The benchmarks are the pollutant concentrations above which EPA determined represents a level of concern. The level of concern is a concentration at which a storm water discharge could potentially impair, or contribute to impairing water quality or affect human health from ingestion of water or fish. The benchmarks are also viewed by EPA as a level, that if below, a facility represents little potential for water quality concern. (See page17031 at:
http://www.epa.gov/fedrgstr/EPA-WATER/2000/March/Day-30/w7203.htm)

Metals: Stormwater was sampled during all 8 storms for Ag, Cd, Cr, Cu, Ni, Pb, and Zn. This list includes all of the metals included on USEPA’s list of Stormwater benchmarks except Fe and Al.  Based on the results of the 2002/2003 sampling, silver and cadmium were not detected. The Plan does call for monitoring the five most common metals detected in typical municipal stormwater (Cr, Cu, Ni, Pb, and Zn), as well as Total Dissolved Solids, Total Suspended Solids, alkalinity and hardness.  We do not believe that the CAM 17 metals is an appropriate list to use to characterize stormwater quality. Rather, the list of CAM 17 metals (22CCR, Section 66261.24(a)), is a list developed to determine if a waste is hazardous in California.  Based on the above information, the monitoring of Cr, Cu, Ni, Pb, and Zn, as included in the December 2003 Plan, is sufficient and the addition of other metals is not warranted at this time.

Total Coliform: The December 2003 Plan calls for monitoring 3 bacteria indicators: Total coliform, E coli, and Enterococci.  RWQCB staff has requested that fecal coliform be added. We do not believe that monitoring for fecal coliform is warranted for several reasons: Regulatory authorities allow for the replacement of fecal with E. coli.  The State Water Resources Control Board is working with counties up and down the state for coastal monitoring and has approved of counties using E. coli as a surrogate for fecal coliform.  EPA, Region IX’s water quality group has approved the use of E. coli as a surrogate for fecal coliform.  The San Francisco Bay Regional Water Quality Control Board’s  NPDES Division has approved the use of E. coli as a replacement for fecal coliform in San Francisco’s Bayside NPDES permit.  The Quanti-Tray method of analysis, which is used extensively in California coastal monitoring programs for total and E. coli, does not provide a result for fecal coliform. Lastly, the Peer Review by Dr. Robert Cooper, Emeritus Professor of Pubic Health at the Univ. of CA, Berkeley dated December 26, 2003 indicates that fecal coliform analysis is not necessary for the Pilot Screening Program.

Use of ammonia and nitrate field kits:  We are currently researching this suggestion and would like to discuss the RWQCB’s experience in using ammonia and nitrate field kits for providing an indication of high coliform levels at our January 15, 2004 Meeting.

In summary, the monitoring program for the pilot program would include the following analytes, methods and reporting limits:

Table 1 –  Summary of Bacteriologic and Chemical Analyses

*Modified with MUG for E. Coli

2) Comment: The proposed Plan does not have adequate sampling station locations to monitor the priority stormwater pollutants of concern appropriate in a baseline study of this nature.  At a minimum, monitoring locations should be located:  a) Before entering the Continuous Deflection System (CDS) unit; b) After leaving the CDS unit; c) In Soil and water samples in the wetland treatment area; d) LM-1; e) LM-2; f) LM-3 and, g)
LM-PR. 

Sampling should also be performed at different lake water levels, not just at the surface, to evaluate pollutant stratification in the Lake water.    Board staff feels that the additional monitoring locations are important in gathering appropriate and meaningful information about the overall fate and transport of stormwater pollutants in the Lake.

Additionally, Regional Board staff strongly support the use of dye test studies to calibrate detention times and identify optimum sampling locations, however we find insufficient details in the Plan.  Please discuss the proposed dye test in a more detailed and strategic manner (dye type, application rates/locations, sampling, etc.).

Response:  Several additional monitoring stations will be added. However, please note that the intent of the Plan is to provide preliminary screening information to determine if future, more detailed, evaluation is warranted. The intent of the Plan is not to provide an exhaustive analysis of all aspects of the pilot wetland treatment system.  Has the Regional Board required such sampling for other discharges of municipal stormwater to surface water bodies in the San Francisco Bay Area?

Additional monitoring stations: Additional stations will be added as requested with the exception of the sample station prior to entering the CDS Unit and soil sampling in the wetland.  The monitoring results from the 2002/2003 show that the CDS does not significantly affect the level of bacteria and nutrients that are the focus of the Plan (CH2MHill, 2004).  We will also supplement in-lake sample stations LM-1, 2, 3 and LM-PR with three additional sample stations to better monitor the lateral extent of discharges to Lake Merced.  Given the limited duration of the test we do not believe that collecting and analyzing soil samples in the wetlands will provide meaningful results.

Vertical Sampling: Vertical sampling does not appear warranted at this time. Lake Merced is a shallow lake (generally less than 20 feet deep) and experiences primarily isothermal conditions with infrequent, weak stratification based on bimonthly ambient multi level monitoring data collected by the SFPUC (EDAW, Aug. 2003).  During the summer there is a slight period of stratification evident in some profiles, but it is not sufficiently strong to impede mixing on a seasonal basis for current lake elevations.   During the winter, the lake does not typically stratify at all. Water depth immediately offshore of the treatment wetlands is generally less than 15 feet.  Bacteriological and nutrient loading concerns, which are the focus of this project, will be adequately addressed based on the surface samples proposed in the Plan.  We do not believe that vertical sampling is warranted for this preliminary water quality screening plan.

Dye test: A dye test was conducted on December 22, 2003. Additional information concerning the Dye test is included in Appendix B. The intention of the dye test was to identify any noticeable short-circuiting of water flows in the system and to approximate mixing and retention times for the pilot test. Water was pumped from Lake Merced using portable pumps and discharged into the upstream end of the 300 ft long perforated pipe to approximate a storm discharge. The weather was clear and it had not rained for the past 24 hours. Total flow was approximately 570,000 to 608,000 gallons based on the flow rate of 3000 to 3200 gpm over a time period of 3 hrs.15 min. The amount of dye injected was sufficient for a strong visual observation at 1 ppm for 126,000 gallons to a weak visual of 100 ppb for 1.26 million gallons. SFPUC biologists monitored the shoreline from a boat in the open water near the shoreline beyond the tule growth that occurs along the lake edge.  No dye was observed in the open water during the 3 hr and 15 min test based on a flow rate of 3000-3200 gpm.

3)  Comment: During sampling, visual observations should also be noted for changes in appropriate wildlife conditions (particularly the number and type of flora and fauna) and other general conditions (e.g., weather, floating trash, water levels, recreational use, etc.).  In addition, it would be an opportunity to conduct and maintain a photographic history of changes in key areas of the Lake.

Response:  The suggested additions to the visual monitoring will be included in the revised Plan.

4) Comment: The Plan does not contain adequate information regarding the Vista Grande Stormwater diversion volume flow rate limits and associated safeguards to cease and desist a diversion, should environmental or human health water quality threats occur.  For example, should significant surface runoff occur over the wetland treatment area, or,
if high pollutant concentrations are found in the Lake, there should be a clear strategy and associated procedures so that the stormwater diversion discharge will be immediately shut off.  

Please describe this section in more detail and include an evaluation of the wetland areas bio-retention capacity and effectiveness.  This evaluation should describe flow attenuation as well as pollutant removal.  Specific flow rate limits should also be discussed and appropriate adaptive management safeguards that will be in place to
prevent water quality threats.  The Plan should clearly describe what would be considered an environmental or human health threat (i.e., coliform exceeds DHS limits, or other parameters exceed Basin Plan limits, etc.).

Response: The Phase 2 pilot project will be approached in stages, starting with small releases of Vista Grande water and increasing the size of those releases only after monitoring the effects of earlier releases.  We will have the ability to regulate and continuously measure the flow into Lake Merced up to a maximum flow rate of about 4000 gpm.  We plan to start at a lower flow rate of 500 gpm with the first storm and collect samples. If the levels are acceptable, then we can increase the flow rate during subsequent storms. This will give us an opportunity to judge the treatment effectiveness relative to flow rate. 

The flow rate and duration of pilot discharges are listed in Table 2, below. Samples will be collected at onshore and in the wetlands during the storm. For safety reasons and to allow sufficient time for stormwater to mix with lake water, off shore samples will be collected within 24-48 hours following discharge. If pollutant concentrations are found to exceed the levels listed in Table 3, the discharge rate of the subsequent test will be reduced or the test will be discontinued. The total volume in South Lake as of December 1, 2004 is approximately 925,000,000 gallons. The individual pilot discharges would range from about 0.1 to 1% of the total lake volume in South Lake.

Vista Grande Stormwater Phase 2 Discharge Rate and Duration

¹One storm will be monitored to access lake water quality in the absence of diversion of Vista Grande Stormwater.

²Volume assumes that flow rate can be maintained for entire duration period.

Target and Maximum Levels for Phase 2 Pilot Stormwater Treatment Project

Notes:     DHS: CCR Title 17, Article 4, 7958

RWQCB: Basin Plan

¹Swimming in Lake Merced is prohibited.

Regional Board staff has asked for an evaluation of the wetland areas bio-retention capacity and effectiveness.  The primary objective of the Phase 2 pilot test is specifically to provide such an estimate of the effectiveness of the existing natural wetland. Literature data for coliform die off rates and nutrient uptake are highly variable. The dye test conducted on December 22, 2003 (See Response to Comment 2) indicated that there was no obvious short-circuiting during the 3 hr and 15 min test based on a flow rate of 3000-3200 gpm and a total flow of approximately 570,000 to 608,000 gallons.

By performing a real pilot test, actual data on the treatment capability can be obtained by leveraging the existing infrastructure (the CDS unit and a pipeline under John Muir Road).

Again, the Plan calls for starting with a low flow rate and ramping up to find the maximum rate where treatment is effective.  If the Phase 2 program provides positive results, then additional, more detailed modeling and analysis will be conducted as part of evaluating building a larger constructed wetland and/or using a larger natural wetland area.    The pilot project is a positive step in adding a local watershed source of water to Lake Merced using a “treatment train” approach.  Ultimately, additional treatment may still be necessary. 

5) Comment: Lastly, we request additional efforts by Daly City and the San Mateo
County Stormwater Program to further investigate priority stormwater pollutant source areas and to minimize runoff to the Vista Grande Canal to the maximum extent practicable. 

Response: The City of Daly City is a co-permittee agency of the San Mateo Countywide Stormwater Pollution Prevention Program.  The City has been involved since the inception of the program in 1993.  As such, Daly City is responsible for compliance with NPDES stormwater best management practices associated with all municipal specific program requirements aimed at the prevention of pollutants to enter stormwater.

Since January 2001, as part of a cooperative effort with the San Francisco Public Utilities Commission to raise water levels at Lake Merced, Daly City has been examining the issue associated with coliform in the stormwater being discharged in the Vista Grande Drainage Basin.  Daly City’s interest is to examine the re-introduction of stormwater within the Vista Grande Drainage Basin watershed back into Lake Merced as a sustainable source of water to maintain lake levels.  To date, Daly City has spent over $403,000 toward finding and addressing the source of coliform within the Vista Grande Drainage Basin, and as yet, a “smoking gun” source has yet to emerge.

Efforts to date include:

·        Bioassay of canal water using trout produced inconsistent results.

·        Sampling begun in May 2001 note both total and fecal coliform present.

·        Begin DNA fingerprinting in September 2002 noting presence of animal and human DNA.

·        Smoke Testing of 31 miles of Vista Grande Drainage Basin conducted in Spring of 2002.  Nine cross connection problems identified and all problems corrected.

·        Installed two Continuous Deflection System (CDS) Units in Fall 2002, units became operational in December 2002 with eight storm events tested and analyzed.

·        Developed a response plan to address 113 chronic sewer lateral (identified as three or more call outs absent corrective action).  Notice to Repair sent out in April 2003.  To date, 93 home repairs have been verified, 3 are under permit, 8 in permit process and 9 enforcement actions pending.

·        Conducted a Sewer System Evaluation Survey to conduct dye testing of homes within the 24-inch sub basin of the Vista Grande Drainage Basin in July 2003.  Purpose was to systematically identify if sewer cross connections existed in the basin.  Basin divided into seven zones downstream to upstream home dye test sequence and retrieval of cotton test pads.  950 homes testing accounting for 92 storm drain manholes.  Two cotton pads retrieved positive for dye.  Some 2,562 feet of pipe video inspected yet no cross connection was found.

References: 

EDAW, Inc., August 2003, Task 3 Technical Memorandum:  Lake Setting, Alternative Lake Levels and Supplemental Water Requirements, Supplemental Water Sources, Lakeside Vegetation (Draft).http://sfwater.org/detail.cfm/MSC_ID/60/MTO_ID/55/MC_ID/7/C_ID/1618/holdSession/1

Appendix A:VISTA GRANDE PILOT PROJECT SEP CRITERIA

Section A.            Basis and Purpose

The North San Mateo County Sanitation District, a subsidiary of the City of Daly City, appreciates the Regional Board’s encouragement of the submittal of Supplemental Environmental Project (SEP) in lieu of a portion of an imposed ACL.  The SEP proposed by the NSMCSD complies with the integrity of an SEP scope of work consistent with an ACL liability calculated by Regional Board staff in the amount of $30,180.  The NSMCSD also appreciates that the Regional Board does not select projects but rather allows a Discharger to identify a project it would like to fund in furtherance of an identified community interest.  The SEP identified by the NSMCSD proposes reasoned, rational and appropriate preliminary pilot project focused to help determine if the introduction of stormwater to Lake Merced will impact the lake’s beneficial uses.  The SEP is supported by the San Francisco Public Utilities Commission (SFPUC) and California Trout, the lead public interest group that has filed a claim with the State Water Resources Control Board that named Daly City as a co-defendant.

(A)            Measures that go beyond all legal obligations of the Discharger.

The NSMCSD does not have any legal obligation associated with Lake Merced as it is an asset of the SFPUC.  As owner of Lake Merced, the SFPUC is agreeable to working with the NSMCSD in accomplishing the pilot study as an appropriate first step toward the examination of the use of stormwater discharge, one of four source water alternatives being examined as part of comprehensive review on how to improve and sustain water levels at Lake Merced.  The NSMCSD is not under any other regulatory obligation associated with stormwater discharge save that associated with its participation as a co-permittee agency under the San Mateo Countywide Stormwater Pollution Prevention Program that incorporates best management practices.

The SEP provides an opportunity, as part of NSMCSD ongoing voluntary cooperation with the SFPUC, to accelerate an examination into the re-introduction of stormwater generated throughout Daly City as a source water into the lake.  Presently, stormwater flows are directed away from the lake and discharged onto the beach beneath Fort Funston.  During heavy rainfall events, stormwater from Vista Grande Canal has overflowed onto John Muir Drive and into Lake Merced.  Thus, overflows have caused flooding problems and roadway/pathway destruction along Lake Merced.  Diversion of stormwater could potentially provide dual benefits of flooding protection and a sustainable source of lake recharge.

(B)       The SEP should benefit or study surface water quality and quantity, and the beneficial uses of waters of the State.

Of the four subjects offered, Environmental Restoration, described as projects that either restore or create natural environments, best characterizes the purpose of the SEP.  The SEP intends to provide a pilot study level of analysis of stormwater quality that expands upon evaluating the feasibility of using Continuous Deflection Units to treat stormwater as a means to increase source water into Lake Merced that is part of an ultimate goal of increasing and sustaining water level of the lake.  The pilot project represents an appropriate next phased study approach to stormwater testing performed during the 2002-03 rainy season during which stormwater was diverted, treated through two CDS units, tested and pumped back into the Vista Grande Canal.  The SEP intends to examine baseline lake water quality and, upon regulatory approval, open an existing gate valve at the headworks of the Vista Grande Tunnel.  A limited flow of stormwater would enter the CDS units and be directed into an existing overflow structure that crosses beneath John Muir Drive to a newly installed 300-foot perforated 12-inch HDPE pipe installed along a vegetated bank at Lake Merced.  The pilot testing at limited flows is patterned after BMP guidance TC-10 (Infiltration Trenches) and TC-21 (Treatment Wetland).  It is expected that the infiltration trench and existing natural wetland will assist with the removal of total suspended solids, biochemical oxygen demand, nutrients and possibly bacterial organisms before reaching the lake’s open water.  As testing results are assessed, stormwater that flows through the CDS units can be increased as storm events permit or the gate valve closed.  The following factors, both qualitative and quantitative, will be used to judge the project’s overall effectiveness: Lake Water Level, Receiving Water Quality, CDS and Infiltration/Vegetation Treatment, Flood Frequency and Vegetation Coverage.

Further, an SEP should be located near the Discharger, in the same watershed.  The Vista Grande Stormwater Pilot Project at Lake Merced is approximately one mile away from the NSMCSD Treatment Plant and is in the watershed that could be used to help sustain lake levels.

Section C. Approval Process

1. North San Mateo County Sanitation District, a subsidiary of the City of Daly City.  Contact person is Patrick Sweetland, Director of Water and Wastewater Resources (650) 991-8201.

    2.      Location is Vista Grande Drainage Basin in Daly City and Lake Merced in San Francisco.

3.      SEP dated September 8, 2003 previously submitted.  Preliminary Water Quality Screening Plan 2003-04 Wet Season dated December 4, 2003 sent to staff.

4. 4.General Cost: $30,180 for SEP.  Pipe installation performed in November 2003 is $49,680.

5. As submitted in SEP subject to revision.

Section D.            Reporting Requirement

Reporting dates acknowledged upon Executive Officer approval.

Section E.            Final Notification

Requirements acknowledged.

Section F.            Third Party Oversight

SEP Budget contains requisite 6% for SEP project oversight to be performed by Dr. Robert C. Cooper, Professor Emeritus of the School of Public Health, University of California at Berkeley.  Dr. Cooper was chosen as the NSMCSD would be hard-pressed to find another individual possessing Dr. Cooper’s credentials to assess potential public health impacts.

Appendix B

Summary of Dye Test Performed Dec. 22, 2003

  Lake Merced Pilot Wetland Treatment Study

On the morning of Dec. 22, 2003, the SFPUC and City of Daly City performed an initial flow characterization study of a proposed wetland treatment area on a vegetated area in proximity to the newly installed Continuous Deflection System (CDS) device as a storm water treatment structure.  The intention of the dye test was to identify any noticeable short-circuiting of water flows in the system and to approximate mixing and retention times for the pilot test. Water was pumped from Lake Merced using portable pumps and discharged into the upstream end of the 300 ft long perforated pipe to approximate a storm discharge. The weather was clear and it had not rained for the past 24 hours.

Total flow was approximately 570,000 to 608,000 gallons at a flow rate of 3000 to 3200 gpm over a time period of 3 hrs. 15 min. The amount of dye injected was sufficient for a strong visual observation at 1 ppm for 126,000 gallons to a weak visual of 100 ppb for 1.26 million gallons.

SFPUC biologists monitored the shoreline from a boat in the open water near the shoreline beyond the tule growth that occurs along the lake edge.  No dye was observed in the open water during the 3 hr and 15 min test.

The dye test indicates that there is no obvious short-circuiting of water flows in the system and retention rates should be sufficient for a short term test.  Dye was observed in the band of tules between the shoreline and the open water.  However, no dye was observed in the open water indicating the absence of any obvious short circuiting within the wetlands at a flow of 3000 gpm over 3.25 hours. 

Pumping started at 10:00 am. Dye was injected at 10:10 am., using 12 oz of 20% Rhodamine WT in a single slug injection.  12 oz. is sufficient for visible observation of 187,500 gal at 100 ppb.  No visual dye observations on the bank side of the tule buffer by 10:45 am.  Daly City crews used 1500 Dye capsules.  The rate was 500 tablets per 100,000 gal., therefore a half hour interval was used for dye injection  First tablets were placed at 10:40. Tablets were placed in cheesecloth bags, and suspended in the pipe at the mixing area where the trash pump outlet hoses were inserted.  The tablets dissolve completely in six to nine minutes.  500 tablets will provide a strong visual (1 ppm) for 127,000 gallons of water.  1500 tablets result in 340 grams of rhodamine WT active ingredient input into the lake.  Visual observation made at 11:15 revealed the dye plume had reached the tule buffer from the shore side, but no visual dye observations were made from the open water side of the tules.  Observations were being made on a continuous basis, traversing the length of the study area and penetrating into the tules. The final bundle of 500 dye tablets were placed in the pipe at 11:45 am.   The final 12 oz of liquid dye were poured in at 12:20 resulting a total of 476 gm of rhodamine wt active ingredient released into the treatment area.  Final observations at 1:10 pm on the shore side of the tules showed visual evidence of the dye within the treatment area.  However, no dye was observed in the open water. At that time, Daly City personnel noticed the visual plume that had migrated to the trash pump intakes, perhaps as a result of flow induced by the pumpage.  Pumping stopped at 1:15 pm.