Monitoring
As part of the TMDL requirements, each municipality must monitor the quality of surface waters discharging to Lake Thunderbird. These monitoring programs are designed to assess the changes in the quality of these waters over time. Data collected may be used to identify land use types or areas in the watershed which are contributing to Lake Thunderbird’s water quality problems. Best management practices are used to reduce these pollutants to levels which meet the TMDL and ultimately align with the uses of the water body.
Oklahoma City, Moore, and Norman each have individual monitoring programs which meet the requirements of the TMDL as well as their community’s needs. Each program may have unique characteristics which provide information and understanding of the watershed.
City of Oklahoma City:
Oklahoma City’s monitoring programs consist of long-term continuous sampling, major outfall monitoring, and illicit discharge detection and elimination monitoring. Three long-term continuous sampling stations are located at or near the terminus of the Hog Creek, Elm Creek and an Unnamed Tributary to Little River as they leave Oklahoma City limits. Samples are continuously collected as flow-paced aliquots over a specific period using automatic samplers. Program goals are to collect information regarding the long-term loading of the study streams.
Major Outfalls are defined as a separate storm sewer system which discharges directly to Waters of the United States and has the following characteristics.
A single pipe with an inside diameter of 36 inches or more (discharge from a single conveyance other than a circular pipe which is associated with a drainage area of more than 50 acres);
Or for municipal separate storm sewers that receive storm water from lands zoned for industrial activity, an outfall that discharges from a single pipe with an inside diameter of 12 inches or more from its equivalent (discharge from other than a circular pipe associated with a drainage area of 2 acres or more).
Oklahoma City monitors these major outfalls for storm water runoff at 27 locations in the Lake Thunderbird watershed using passive samplers. These devices provide sample collection without personnel onsite during hazardous conditions (see pictures). Samples are collected after the storm has passed and sent to the laboratory for analysis. Passive samplers collect the first flush of runoff, which often has the highest concentrations of pollutants during a precipitation event. Program goals are to establish or verify specific land use types which may be contributing higher levels of pollutants which impact Lake Thunderbird.
The Illicit Discharge Detection and Elimination monitoring has been part of the Oklahoma City’s permit since initial program authorization by the Environmental Protection Agency. This program is designed to detect non-storm related discharges during periods of dry weather. Water tests and observations are conducted to determine if flows may be in part or wholly contributed by illicit sources. When detections are made, technicians track the source(s) and work with responsible parties to eliminate those discharges. Oklahoma City has 33 IDDE stations in the Lake Thunderbird watershed.
What are the devices?
The devices are called passive storm water samplers. The purpose of the device is to collect a sample of storm water runoff when a channel or storm drain begins to fill with rainwater runoff. A passive sampler consists of a rigid outer housing which can be partially buried, set on a post, hung in storm drain inlets or various other configurations. When a storm is predicted, OKC staff will insert a clean sampling container into the housing. When precipitation occurs, storm water runoff will fill the internal sampling container. OKC staff will return the following day to collect the samples.
Are these devices dangerous?
No, they are meant to be as unobtrusive as possible. Children should not play around the devices as they can be a trip hazard. Landscaping personnel and residents should be aware of the device to avoid mowing over the housing.
Why does OKC need to sample?
Oklahoma City is required to sample due to water quality problems in Lake Thunderbird. The Oklahoma Department of Environmental Quality and the Environmental Protection Agency require several impacted Cities to develop a plan to comply with necessary pollutant reductions which are causing or contributing to water quality problems in Lake Thunderbird. This requirement is identified in a document called a Total Maximum Daily Load (TMDL). This document provides methodology, data and calculations of the necessary pollutant reductions for each City to meet water quality standards in Lake Thunderbird.
What Cities are impacted?
Oklahoma City, Moore and Norman are primarily impacted by the Lake Thunderbird TMDL. Each City has a unique plan and will conduct monitoring of storm water quality.
What pollutants are being monitored?
The primary pollutants are Nitrogen, Phosphorus and suspended solids. A secondary pollutant is oxygen demanding substances. Extra nutrients in the Lake have caused excessive algae growth which can create taste and odor problems in drinking water, in-lake oxygen problems, among others. Suspended solids include the sediments and other solids in the water which eventually make it to the Lake. Once in the Lake, these solids can settle and smother fish habitat, reduce water clarity and water depths.
Is this the only monitoring that is being done in OKC?
No, this is one of several monitoring projects in the watershed. Oklahoma City has installed three permanent stations to determine the long-term pollutant loads delivered to Lake Thunderbird. Several other areas are being monitored periodically to determine if illegal dumping or discharges are contributing to the problems.
Can I remove this device?
The devices have been installed in areas that are best for acquiring a sample which is representative of the drainage landscape. Most devices are in areas which should not prohibit daily activities. If a device is located in an area which impacts a property owner, it can be moved by City personnel.
Can I mow around it or trim around it?
Yes, the point is to acquire a sample which represents the activities in your area. We anticipate no change in your daily activities or maintenance of your landscape. We do ask that you report any damage to the devices and refrain from tampering as these devices are critical in understanding the watershed dynamics.
How often will the devices be checked?
Technicians will periodically check the samplers to make sure that damage has not occurred between sampling events. Typical damage or maintenance may include sediment accumulation in the housing, debris on the post, theft or other intentional damage, etc. Generally technicians will check the devices every two months during the dry parts of the year and monthly during the wetter times of the year. Other visits may include putting a sampling container into the housing or collecting the sample container for laboratory analysis.
Will personnel be collecting samples during odd hours?
Generally no, but there are always exceptions. The devices were selected to limit the interruption of nearby residents by collecting samples without having personnel onsite. City technicians will collect the samples after the precipitation event has passed and typically the next day during normal working hours.
How many times will these sites be sampled each year?
OKC’s goal is to collect each quarter (4 times/year). However, as we all know, weather forecasts are not always accurate. Many sampling events may be cancelled or postponed until the correct target rainfall is predicted.
How long will this study last?
The study is currently set for 5 years. Certain stations are selected for monitoring each year. If you have not seen a technician at the passive sampler, it may be because that station is not scheduled for monitoring that year.
What personnel will be checking on these devices?
The personnel are from the Public Works Department’s Storm Water Quality Management Office. Most can be recognized by City issued shirts/jackets which should be clearly marked as City of Oklahoma City. They should be in a City vehicle which should also be clearly marked. The personnel are all water quality professionals which perform biological collections, water quality analysis and collect other environmental data each day.
As these devices are installed in drainages, you may see a technician at a storm drain, in a ditch or culvert. We did not install these devices in backyards or areas which would need special access. Please feel free to stop and ask questions of the technician. If a question has not been answered by this document, please send the question to Derek Johnson so we can add it (with response).
City of Moore
The primary goal of the City of Moore’s monitoring program is to obtain baseline data on receiving streams in Moore for use in determining long-term water quality trends. Moore’s Compliance and Monitoring plans can be found here:
City of Norman
The City of Norman’s Monitoring Plan was developed to establish a baseline for flow and pollutant loading in streams flowing from or through Norman to Lake Thunderbird. Pollutants to be monitored include nitrogen, phosphorus, and total suspended solids. Gauging Stations used to measure flow have been installed at 10 monitoring stations that are sampled monthly, and quarterly sampling occurs at 7 of 14 major discharge/significant stormwater outfall locations each year. As part of the routine sampling at these sites, in-stream parameters, such as pH, temperature, dissolved oxygen, specific conductance and turbidity, are also measured. This monitoring will provide baseline information for pollutant loading reduction and provide the necessary data to support the design and installation of appropriate Best Management Practices (BMPs) for the various creeks and streams in the watershed.
As data are accumulated through monitoring activities, it will be analyzed and reviewed to determine if the load reduction required by the TMDL report is being achieved. These data will also make it possible to identify sub-watersheds where structural BMPs may be necessary to achieve the required pollutant load reductions.
