Exhibit C Attachment A Discharge Limits and Monitoring Requirements.pdf
PDF 119 KB Posted
- Attached to
- NCC WTP Operations and Maintenance
- Solicitation number
- RFP FAAA 2027000059 1
- Issued by
- Gilpin County, Colorado
About this file
This document is Exhibit C Attachment A to the North Clear Creek Water Treatment Plant (NCCWTP) Operations and Maintenance Scope of Work, detailing discharge limits and monitoring requirements for the facility's water treatment operations. The scope establishes predicted influent parameters including flow rates of 80-600 gallons per minute, pH levels of 4.1-6.4 standard units, and concentrations of various dissolved and recoverable metals including cadmium, copper, iron, manganese, and zinc. The Operator is required to monitor effluent at three designated outfalls with varying frequencies and sample types. Outfall 001, the primary treated water discharge from the facility, requires continuous flow monitoring, daily pH grab samples, weekly composite samples for suspended solids and hardness, and weekly composite or grab samples for various heavy metals. Outfalls 002 and 003, representing bypass discharges, require monitoring only when flow continues for at least two hours, with daily pH monitoring and weekly grab samples for heavy metals.
The monitoring program encompasses influent sampling at four locations (300I, 400I, 500I, and 600I) at varying frequencies ranging from continuous flow recording to semi-annual grab samples. Influent 300I sampling occurs quarterly, while influents 400I, 500I, and 600I are sampled semi-annually during high flow conditions in June and low flow conditions in December. Effluent limitations for Outfall 001 include specific maximum concentrations for parameters such as total suspended solids (30-45 mg/L), cadmium (0.61-1.5 µg/L), lead (2.0-51 µg/L), and manganese (1531-2772 µg/L). The document also establishes annual acute toxicity testing requirements using Pimephales promelas and Ceriodaphnia dubia species to ensure water quality standards are maintained.
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NCCWTP Operations and Maintenance Scope of Work Attachment A
Discharge Limits and Monitoring Requirements
1. Predicted Influent
Parameter Predicted Influent Flow (gallons per minute) 80 – 600 pH (standard units) 4.1 – 6.4 Cadmium, dissolved (mg/L) 0.002 – 0.01 Copper, dissolved (mg/L) 0.05 - 1.3 Iron, total recoverable (mg/L) 25 - 150 Manganese, dissolved (mg/L) 8 - 28 Zinc, dissolved (mg/L) 2 - 9 Sulfate, total (mg/L) 900 - 1600
2. Effluent Monitoring and Limitations
The North Clear Creek WTP Operator (Operator) shall monitor all effluent parameters at the frequencies and sample types listed below.
Outfall Description 001 Outfall 001 is the outfall from the North Clear Creek Water Treatment
Plant prior to contact or commingling with any surface or ground water. Outfall 001 will be monitored at the overflow of the V-Notch weir located in the facility effluent vault (TK-400).
002 Outfall 002 is the outfall from the bypass structure which passively discharges untreated influent when the influent vault (TK-050) water level exceeds storage capacity. Outfall 002 will be monitored from the vault door adjacent to the 12” bypass pipe.
003 Outfall 003 is the outfall from the bypass structure which diverts flow from the source conveyance pipeline through the bypass storm drain (BPST) around the North Clear Creek Water Treatment Plant. Outfall 003 will be monitored from Manhole 18, located upstream of the influent vault.
Table 1 - Outfall 001 – Effluent Monitoring Requirements
Effluent Parameter
Effluent Limitations Maximum Concentrations
Monitoring Requirements
30-Day Average Daily Maximum Frequency Sample
Type
Effluent Flow (MGD) 0.65 Report Continuous Recorder pH (su) -- 6.5-9.0 Daily Grab TSS, effluent (mg/l) 30 45 Weekly Composite Oil and Grease (visual) -- Report Weekly Visual Oil and Grease (mg/l) 10 Contingent Grab TDS (mg/l) -- Report Quarterly Composite Hardness as CaCO3 (mg/l) -- Report Weekly Composite Cd, PD (µg/l) 0.61 1.5 Weekly Composite Cu, PD (µg/l) 64 -- Weekly Composite
Effluent Parameter
Effluent Limitations Maximum Concentrations
Monitoring Requirements
30-Day Average Daily Maximum Frequency Sample
Type
Fe, TR (µg/l) 5400 -- Weekly Composite Pb, PD (µg/l) 2.0 51 Weekly Composite Mn, PD (µg/l) 1531 2772 Weekly Composite Ni, PD (µg/l) 43 388 Weekly Composite Ag, PD (µg/l) 0.05 1.4 Weekly Composite Zn, Dis (µg/l) 740 -- Weekly Composite Sulfate (mg/l) -- Report Quarterly Composite LC50 Statre 96Hr Acute Pimephales promelas -- LC50 ≥100%
(daily min) Annual Grab
LC50 Statre 48Hr Acute Ceriodaphnia dubia -- LC50 ≥ 100%
(daily min) Annual Grab
Bypass Monitoring
In the event that any flow is bypassed through Outfall 002 or Outfall 003 and continues for at least 2-hours, the following samples shall be collected.
Table 2 - Outfall 002 and Outfall 003 - Bypass Monitoring
Parameter Monitoring Requirements Frequency Sample Type
Flow (MGD) Continuous Recorder pH (su) Daily Grab Cd, PD (µg/l) Weekly Grab Cu, PD (µg/l) Weekly Grab Fe, TR (µg/l) Weekly Grab Pb, PD (µg/l) Weekly Grab Mn, PD (µg/l) Weekly Grab Ni, PD (µg/l) Weekly Grab Ag, PD (µg/l) Weekly Grab Zn, PD (µg/l) Weekly Grab
3. Influent Monitoring
Regardless of whether or not an effluent discharge occurs, the Operator shall monitor influent parameters at the following required frequencies.
Influent Description
300I Influent 300I is the influent vault (TK-050) located at the North Clear Creek Water Treatment Plant.
400I Influent 400I is the Gregory Incline manhole where flow is continuously recorded.
500I Influent 500I is the collection trench were Gregory Gulch is diverted into the conveyance pipeline.
600I Influent 600I is the National Tunnel flume located under the pedestrian bridge at Mill Street.
Table 3 – Influent 300I - Monitoring
Parameter Monitoring Requirements
Frequency Sample Type Flow (MGD) Continuous Recorder pH (su) Quarterly Grab
TDS (mg/l) Quarterly Grab
Hardness as CaCO3 (mg/L) Quarterly Grab
Cd, PD (µg/l) Quarterly Grab
Cu, PD (µg/l) Quarterly Grab
Fe, TR (µg/l) Quarterly Grab
Pb, PD (µg/l) Quarterly Grab
Mn, PD (µg/l) Quarterly Grab
Ni, PD (µg/l) Quarterly Grab
Ag, PD (µg/l) Quarterly Grab
Zn, PD (µg/l) Quarterly Grab
Sulfate (mg/L) Quarterly Grab
Table 4 - Influent 400I, Influent 500I and Influent 600I - Monitoring
Parameter Monitoring Requirements
Frequency Sample Type Flow (MGD) Continuous Recorder pH (su) Semi-annually Grab
Cd, PD (µg/l) Semi-annually Grab
Cu, PD (µg/l) Semi-annually Grab
Fe, TR (µg/l) Semi-annually Grab
Pb, PD (µg/l) Semi-annually Grab
Mn, PD (µg/l) Semi-annually Grab
Ni, PD (µg/l) Semi-annually Grab
Ag, PD (µg/l) Semi-annually Grab
Zn, PD (µg/l) Semi-annually Grab
Semi-annual sampling to occur during high flow (June) and low flow (December)
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