Stormwater Monitoring Challenges and Trip-ups

Transcription

1 ASCE Oregon EWRG Stormwater Monitoring Challenges and Trip-ups in search of the elusive EMC January 25, 2017 Presented by Curtis Nickerson Bryan Berkompas

2 It s a challenge! Targeting an ephemeral event Challenge to get representative data Difficult working conditions

3 Overview Stormwater monitoring basics Planning a monitoring project Site selection consideration Instrument selection and installation Pointers for project implementation

4 Stormwater monitoring basics Water quality sampling In-situ WQ measurements Flow metering Rain gauging Stormwater sediment sampling

5 Water quality sampling approaches Manual grab sampling instantaneous measurement Time-paced composite sampling time-averaged concentration Flow-weighted composite sampling event-mean concentration can calculate loading

6 Monitoring project planning Monitoring infrastructure has typically been an after thought Get in on the facility design process More difficult to retrofit for monitoring

7 Start planning early! Prepare planning documents Select site(s) Procure equipment and materials Install and test equipment Train staff

8 Allow yourself 4-6 months to prepare

9 Before you can implement the project

10 Monitoring site selection Locations driven by project objectives Characterization Pollutant source tracing Permit compliance BMP effectiveness evaluation

11 Select sites that isolate flows of interest but provide monitorable conditions

12 Site selection considerations Access Security Future changes to infrastructure Confined space Traffic control Vandalism Power source Cell phone access Flooding Flow conditions Pipe characteristics Tidal influence Backwater Permanent site for sampling equipment Off-site, co-mingled sources Freezing conditions

13 Ensure access and security

14 Flow metering options flume weir bubbler flow meter pressure transducer look-down sensor area-velocity meter Venturi tube meter mag meter

15 Flow monitoring challenges Channel or pipe slope too steep Water depth too shallow No defined channel Backwater conditions, including tidal effects Large range of flows Straight reaches/ pipe sections too short

16 Include monitoring in infrastructure design

17 Include monitoring in infrastructure design flume

18 Retrofit with primary devices Thelmar weir

19 Addressing difficult hydraulic conditions foam wedge

20 Addressing poorly defined channel

21 Flow monitoring at flow control structures bypass secondary orifice primary orifice measure water level then calculate flow from orifice and weir equations

22 Custom equipment 3-in. magmeter medium to high flows (max. 160 gpm) tipping bucket trickle and low flows (<1.8 gpm)

23 Custom equipment secondary drain primary drain

24 Manual grab sampling Swing arm sampler

25 Passive grab sampler

26 Grab sampling from deep manholes extension pole suction from pump sample tubing sample bottle sealed canister

27 Grab sampling from deep manholes

28 Catch basin insert sampling

29 Catch basin insert sampling

30 Autosampler examples

31 Addressing high velocity or shallow flows low flow strainer

32 Customized samplers cubitainer

33 Customized autosamplers drum sampler

34 Customized autosamplers drum sampler

35 Customized autosamplers mega sampler

36 Rainfall measurement Onsite rage gauge or nearby if accessible realtime Need open area Security a concern

37 Tipping bucket rain gauge

38 Tipping bucket rain gauge

39 Considerations for monitoring station installation Don t believe design plans always measure and inspect critical elements Orifice sizes/ condition Weir position Incorrect construction

40 Considerations for monitoring station installations

41 Considerations for monitoring station installation

42 Expect extreme weather

43 Expect extreme weather

44 Tips for hardening monitoring stations Sturdy housing Concrete pad or wooden platform Conduit for electrical cable and suction line (below ground if vehicle traffic present) Anchor housing if security a concern Seal gaps to exclude rodents and insects Stainless steel fasteners if zinc a concern Use quick connects for sampler suction line Use zip-ties to organize cables in the hole Keep suction line and electrical cables out of flow line to protect from debris

45 Un-hardened monitoring station

46 Hardened monitoring station

47 Hardened monitoring station

48 Hardened monitoring station

49 Above ground installation preferred, but sometimes not possible. Manhole hanger

50 Underground installation

51 Telemetry is a game changer! Provides remote control of samplers and flow meters Frequent automatic downloading of data on a set schedule We use Campbell Scientific data logger/controllers for flexibility with instrumentation and programming Communicate via cellular, radio, and even satellite option

52 Benefits of telemetry Reduced labor to arm samplers prior to storm events Ability to modify instrument settings remotely immediately prior to or during a storm One person (Storm Controller) can monitor status of numerous stations concurrently Automatic notifications based on alarm settings Field staff deployed only as-needed

53 Insert screen shot of logger net Loggernet connect screen

54 m in ft Targeting a storm with telemetry sdn1-tele Flowlink 4 for Windows 2.0 Level (1.906 ft) Rainfall (0.08 in) Sample ( m) Sat Oct PM 6PM 9PM 7 Sun 3AM 6AM 9AM 10/6/2007 2:00:00 PM - 10/7/ :00:00 AM

55 Tips for data collection phase Make sure you have sufficient, well trained staff Train for confined space entry, instrument operation, sample collection and handling methods Rotate storm response assignments make schedules as predictable as possible Be ready to improvise! Storms rarely occur as advertised Equipment malfunctions People make mistakes

56 Tips for data collection phase Develop and use SOPs for everything Detailed field sheets completely filled out! Double check equipment Ice samples immediately and thoroughly Be safe! often dark, wet, cold and windy

57

58 Sample processing options Decaport sample splitter for sample compositing/ splitting

59 Sample processing options Churn sample splitter to fill bottles for laboratory analysis

60 Hydrologic data QC actions Conduct routine maintenance and calibration Download and check flow and rainfall data regularly Is it believable? If not, investigate Check instrument performance Check site for potential causes of strange data

61 Check instruments Rain gauge calibration check

62 Check instruments Secondary flow measurement

63 Water quality QC actions Collect field and trip blanks routinely Backflush sampler tubing thoroughly Replace sampler tubing periodically Adjust laboratory decon procedures if necessary Raise sampler strainer out of baseflow/sump between sampling events

64 Questions? Curtis Nickerson