New: View water quality readings for the months of May 2008 through Sept. 2008

The Norwalk River Watershed Project Water Quality Report for the April-May 2004 monitoring period:

Go Straight to the Readings

I. Introduction:

Purpose of Study: The Earthplace (formerly NCEA) Harbor Watch/River Watch (HW/RW) Program has been funded by the Connecticut Department of Environmental Protection (CT DEP) to conduct a fourth and fifth year water quality monitoring study on the Norwalk River for the period of July 2002 through June 2004. HW/RW will collect and analyze water samples for both fecal coliform bacteria and Escherichia coli (E. coli) bacteria at ten sites along the main stem of the Norwalk River and the Sivermine River (one site).

Background: From June 1998 through May 1999, HW/RW conducted a first-year water quality monitoring study in the Norwalk River Watershed. This study was funded by the CT DEP and was intended to provide water quality information in support of the Norwalk River Watershed Initiative. The purpose of the study was to obtain data on the levels of fecal coliform bacteria, oxygen levels and conductivity at selected locations in the Norwalk River and in its major tributaries (Silvermine River, Comstock Brook and Cooper Pond Brook). The study also included the collection of benthic macroinvertebrates at two Norwalk River sampling sites and one reference site (Saugatuck River). The study indicated that fecal coliform bacteria levels frequently exceeded the state's water quality criterion for Class B water at a number of sites along the Norwalk River. Most sites met the dissolved oxygen level CT DEP criterion for Class B waters. The first year study also showed that conductivity levels were consistently higher in the upper reaches of the watershed than in the lower watershed. Based upon the water quality data collected and the results of the benthic macroinvertebrate sampling, HW/RW determined that the water quality in the Norwalk River Watershed was moderately impaired.

At the conclusion of the first year of study and during the time when a second year monitoring scope of work document was being finalized with the CT DEP, HW/RW was successful in obtaining short-term funding to support continued water quality monitoring. The Norwalk Harbor Management Commission's Water Quality Committee and the Norwalk Shellfish Commission provided funding for water quality monitoring during July and August 1999. Data collected during this two-month period indicated that fecal coliform bacteria levels continued to exceed the CT DEP Class B river bacteria criterion at selected sites in the Norwalk River Watershed.

The first year's monitoring effort analyzed only for fecal coliform bacteria for which the State's Water Quality Standards provides a criterion for meeting Class B rivers. For the purposes of this second year study, E. coli bacteria levels were also reported. E. coli is one of the two bacteria components of the fecal coliform bacteria group, and it is a more specific indicator of fecal material arising from humans and other warm-blooded animals. For recreational waters the US EPA recommends the use of E. coli because it is a better indicator of a human health risk from water contact than fecal coliform bacteria.

The CT DEP and HW/RW executed a contract for the second year funding in September 1999; the second year monitoring period was from September 1, 1999 through November 30, 2000. Prior to sampling for E. coli, HW/RW was required to amend its Quality Assurance Project Plan (QAPP); as a result, HW/RW only sampled for fecal coliform bacteria in September and in October. HW/RW was authorized to begin testing for E. coli bacteria in November 1999. Sampling took place at 12 sites along the Norwalk River. Monthly reports were prepared and submitted to the CT DEP and disseminated to the Norwalk, Ridgefield, Redding, and Wilton health departments and conservation commissions, the City of Norwalk's Harbor Commission's Water Quality Subcommittee, and the Norwalk River Watershed Action Plan Advisory Committee.

Funding was then made available by the CT DEP to continue testing on the Norwalk River for a third summer (April 1 to September 30, 2001) based on a continuing interest by Norwalk River Watershed Advisory Committees and the CT DEP. The same testing protocols used in 2000 by HW/RW were again used under the original QAPP which was extended on April 25, 2001 to September 30, 2001 by the EPA's Office of Environmental Measurement and Evaluation.

Recently, additional 319 funding was allocated to continue the HW/RW testing regime on the Norwalk River for twenty-three months beginning July 2002 and ending June 30, 2004. The same testing protocols will be used be used to support the recently granted Total Maximum Daily Load (TMDL) status given to the Norwalk River by CT DEP. The existing QAPP (expires on September 30, 2002) will be extended to the end of the new contract period or June 30, 2004. The June 2002 research was done by HW/RW prior to the beginning of the new contract period of July 2002 in order to maintain continuity for the summer months of 2002. The Silvermine River (Site SM3) was the only tributary to be added back to the testing schedule because of strong interest in a trout habitat restoration project undertaken by the Norwalk River Watershed Initiative during 2001/2002.

Although a draft of the monthly report is submitted to the CT DEP for review and comments prior to its distribution, Harbor Watch/River Watch is solely responsible for the collection, analysis and interpretation of the water quality data that is reported in these monthly reports.

II Methods and Procedures:

Water monitoring is carried out under protocols of an EPA approved and revised EPA Quality Assurance Project Plan (QAPP) re-approved from September 2002 through September 2004. Monitoring teams leave the Nature Center in Westport between 9:30AM and 10:00AM, and return in early afternoon. Each team is comprised of an experienced leader and one or two trained volunteers. Water samples are collected at 10 (Figure A1) of the original 23 monitoring sites within the watershed (QAPP Appendix A1.1). These sites, which represent the more impacted areas, were selected in concert with the CT DEP for study, because results from the first year's study consistently demonstrated elevated fecal coliform bacteria counts. In addition to focusing monitoring efforts at these sites, it was determined to analyze for both fecal coliform and E. coli bacteria.

The following tests are run in situ: dissolved oxygen (QAPP Appendix A3.1) and conductivity (QAPP Appendix A3.5). Water and air temperatures, as well as general observations and storm events are also recorded at each site visit. Observations are recorded (QAPP Appendix 5) on the HW/RW Data Sheet.

Upon return to the lab, fecal coliform and E. coli bacteria membrane filtration tests (QAPP Appendix A3.10) are performed and analyzed according to Standard Methods, 20th edition (9222D & 9222G) and recorded (QAPP Appendix 5) on the HW/RW bacteria log. The frequency of which water quality monitoring for bacteria concentrations occurs is separated into two seasonal testing periods. For the period when the three wastewater treatment plants (WTP) are required to disinfect their wastewater effluent (May 1st to September 30th) monitoring is done four times per month. For the period when effluent disinfection is not required (October 1st to April 30th) monitoring is done monthly.

E. coli bacteria will be evaluated using the criteria published in the CT DEP Surface Water Quality Standards, 12/17/02. The CT DEP E. coli criterion for Class AA, A, and B water is established at three levels (Table1).

Table 1: CT DEP criterion for E. coli bacteria levels as applied to recreational use, effective 12/17/02.

Designated Use Class Indicator Criteria
Recreation
Designated Swimming AA, A, B Escherichia coli Geometric Mean less than 126/100; Single Sample Maximum 235/100
Non-designated Swimming AA, A, B Escherichia coli Geometric Mean less than 126/100; Single Sample Maximum 410/100
All Other Recreational Uses AA, A, B Escherichia coli Geometric Mean less than 126/100; Single Sample Maximum 576/100

The Norwalk River is suitable for non-designated swimming, because people swim in some of the deeper sections of the river. The report will focus on E. coli bacteria levels, because it is the indicator bacteria of choice by the CT DEP. Fecal coliform bacteria levels are reported on Table B1 only as additional data for those who may be interested.

III Results:

NR1=Post Road, Norwalk, SM3=James St., Norwalk, NR4=Glover Ave., Norwalk, NR6=Wolfpit Road, Wilton, NR9=School Road, Wilton, NR13=Branchville Station, Ridgefield/Wilton, NR15=Stonehenge Road, Ridgefield, NR20=Fox Hill Condos, Ridgefield, NR21=Farmingville Road, Ridgefield.

  1. On 4/22 seven days after a light rainfall of 0.24 all Norwalk River monitoring sites met the CT DEP E. coli single sample maximum (SSM) of 410 CFU/100 mLs (Table 2b, Figure 1).

  2. On 5/6 three days after a moderate rainfall of 0.37 inches, all sites met the CT DEP E. coli SSM (Table 2a, Figure 2).

  3. On 5/13, two days after a light rainfall of 0.26 inches, all sites met the CT DEP E. coli SSM (Table 2a, Figure 2).

  4. On 5/20, four days after a light rainfall of 0.28 inches, sites NR21, NR15 and NR13 all exceeded the CT DEP E. coli SSM (Table 2a, Figure 2).

  5. On 5/27, the same day of heavy rainfall of 1.03 inches, all sites except NR9.5 and NR9 exceeded the CT DEP E. coli SSM (Table 2a, Figure 2). A maximum E. coli value of 2840 CFU/100mLs was observed at Site NR1.

  6. During the period when UV lights are turned on to disinfect the effluent discharge from the two Ridgefield and the Georgetown waste water treatment plants (May 1 through September 30) only two Sites NR9.5 and NR9 meet the CT DEP geomean criterion of 126 CFUmLs for a Class B river (Table 2a, Figure 3a). The percent frequency of tests (4 to date) exceeding 410 CFU/100 mLs is over 10% for all sites except Site NR9.5 and NR9 (Table 2a).

  7. During the period when disinfection is not required by the two Ridgefield and the Georgetown waste water treatment plants NPDES permit (October 1, through April 30) five of the monitoring sites exceed the CT DEP geomean criterion (Table 2b, Figure 3b). The maximum geomean is 1154 CFU/100mLs at Site NR21 (Table 2b). In addition, all sites exceeded the 10% frequency limit of bacteria counts in excess of 410 CFU/100mLs (Table 2b).

  8. Conductivity geomeans range from 570 uS at Site NR21 to 510 uS at Site NR15 (Figure 4). After the confluence with Cooper Brook (just above Site NR13) conductivity geomeans are reduced to 350 uS and stay at or below this value for the balance of the Norwalk River (Figure 4).

  9. Dissolved oxygen means and all individual samples meet the CT DEP criterion of 5 mg/L or greater at all sites on all sampling dates (Figure 5).

Footnote: Water quality on 4/22 is exceptionally good at Site NR21 (Table 2b, Figure 1). According to the Ridgefield WTP Manager the UV lights were turned on in mid-April to test the system. The observed fecal coliform count at the WTP discharge stream was 14 CFU/100mLs on 4/22.

IV. Discussion:

Rainfall for April was 6.02 inches, which is well over the monthly average of 4.0 inches. The HW/RW sampling date of 4/22 was preceded by only one period of precipitation of 0.24 inches on 4/14. May followed with a total of 2.71 inches which means a dry summer may be on the way. The first three sampling days in May 5/6, 5/13 and 5/20 were barely influenced by rainfall (Figure 2). As a result, the April and May test dates (with the exception of 5/27) show the Norwalk River watershed with little stormwater runoff impacting the system. Water quality, for all four dates is generally fair (Figure 1, Figure 2, Table 2a, Table 2b).

Nevertheless, rising water temperatures observed on 5/13 (19 C-20 C) and on 5/20 (16 C-18 C) are beginning to provide a better environment for E. coli bacteria (Table B1). This is a possible reason for the observed increase in all bacteria counts on 5/13 and 5/20.

Heavy rain of 1.03 inches on 5/27 (the day of testing) provides a view of the Norwalk River watershed under heavy stormwater runoff conditions. Observed bacteria counts exceed the SSM of 410 CFU/100 mLs on all sites except Sites NR9.5 and NR9. As problem sites become evident in the warming waters of the Norwalk River it would appear that four northern sites: NR21, NR23, NR15 and NR13, will be on the list for more detailed evaluation by HW/RW, as well as the four southern sites NR6, NR4, SM3 and NR1 (Figure 2).

Conductivity values show wide ranges mS at sites NR21, NR20and NR15 and narrow ranges below (downstream of Site NR13). The reason for the wider conductivity ranges in the northern end of the watershed is not known. It would appear that water from Cooper Brook, Bennett Brook and Comstock Brook may have a stabilizing effect on the river, as well as helping to lower conductivity geomeans (Figure 4). The low value of 155 mS observed at Site NR4 on 5/6 can not be explained (Figure 4).

Dissolved oxygen means and all individual samples meet the CT DEP D.O. criterion of 5 mg/L or more (Figure 5).

V. Index of Figures, Tables and Appendices:

Table 1 CT DEP criterion for E. coli bacteria levels as applied to recreational use, effective 12/17/02.

Table 2a May 6, 2004 to May 27, 2004 E. coli bacteria concentrations, geometric means and % frequency exceeding 410 colonies /100 mL at 10 monitoring stations in the Norwalk River watershed during the period of time when the two Ridgefield and one Georgetown wastewater treatment facilities are required by permit to disinfect sewage effluent.

Table 2b October 16, 2003 to April 22, 2004 E. coli bacteria concentrations, geometric means and % frequency exceeding 410 colonies/100 mL at 10 sampling stations in the Norwalk River Watershed during the period of time when the two Ridgefield and one Georgetown wastewater treatment facilities are not required by permit to disinfect sewage effluent.

Figure 1 E. coli bacteria concentrations and rainfall at 10 monitoring sites in the Norwalk River Watershed on April 22, 2004.

Figure 2 E. coli bacteria concentrations and rainfall at 10 monitoring sites in the Norwalk River Watershed during May 2004.

Figure 3a Geometric means of E. coli bacteria concentrations at 10 monitoring sites in the Norwalk River watershed during May 2004 (4 testing days) when the two Ridgefield and one Georgetown wastewater treatment facilities are required by permit to disinfect sewage effluent.

Figure 3b Geometric means of E. coli bacteria concentrations at 10 monitoring sites in the Norwalk River watershed from October 16 trough April 22, 2004 (7 testing days) when the two Ridgefield and one Georgetown wastewater treatment facilities are not required to disinfect sewage effluent.

Figure 4 Conductivity values (S) at 10 monitoring sites in the Norwalk River watershed for April and May 2004.

Figure 5 Dissolved oxygen levels at 10 monitoring sites in the Norwalk River Watershed for April and May 2004.

Appendix A

Table A1 Site identification, site location, GPS coordinates and town for sampling and testing (headwaters to the mouth)

Figure A2 Norwalk River testing sites (northern and southern watershed maps)

Appendix B

Table B1 Station number (sampling site), date, time, air temperature, water temperature, dissolved oxygen, conductivity, fecal coliform bacteria, E. coli bacteria, rainfall, number of days prior to sampling and QA/QC activity in March 2004.

Table B2 Results of fecal coliform bacteria counts (colonies/100 mL) inter-laboratory services with the Norwalk Public Health Laboratory (NPHL).

VI. References:

Harris, R. B. and P. J. Fraboni. Quality Assurance/Quality Control Plan for the Norwalk River Watershed Monitoring Project (QA No. CT00162) (re-approved October 2001 and extending to September 2002).

US Environmental Protection Agency. 1986. Ambient Water Quality Criteria for Bacteria, US EPA 440/5-84-002, Washington, DC.

Harris, R. B. and P. J. Fraboni. 1999. Water Quality Data Final Report for the Norwalk River Watershed (June 1998 -May 1999).

Harris, R. B. and P. J. Fraboni.2000. Water Quality Data Final Report for the Norwalk River Watershed (July 1999-September 2000).

Harris, R. B. and P. J. Fraboni.2001. Water Quality Data Final Report for the Norwalk River Watershed (July 2001 -September 2001).

CT DEP, Water Quality Standard 12/17/02.


Water Quality Data Report For The Norwalk River Watershed August 2002

Dick Harris, Principal Investigator, Staff Scientist/Director of the Harbor Watch/River WatchSubmitted Program - Earthplace, Westport, CT Phone: (203) 227-7253.

Peter Fraboni, Associate Director & QA/QC Officer for the Harbor Watch/River Watch - Earthplace, CT, Westport Ct.

View water quality readings for the months of May 2008 through September 2008

View water quality readings for the months of October 2007 through April 2008

View water quality readings for the months of May through September 2007

View water quality readings for the month of August 2004

 

 

 
 

 

Home | Atlas | Contact Us| Publications | Events | Watershed Information | Links | Water Quality

© Norwalk River Watershed Association, a 501(c)(3) nonprofit membership organization