Sewer Committee Reviews Design Criteria for Rico Business Area
River discharge regulations, winter temperatures, altitude, and seasonal water consumption considered.
Some of the on-screen notes by Alex Wing from the Rico Sewer Committee May 5 web-meeting
Rico Sewer Committee
May 5, 2020 - 5:30 PM - via Internet
Kari Distefano - Rico Town Manager
Rico Sewer Committee members discussed goals, objectives and technical information needs for the proposed business area wastewater treatment system via Internet session May 5, 2020. Members determined that a clear definition of the wastewater system is needed before proposals from equipment vendors may be requested. Research into STEP systems will be begin and be ready for the next monthly meeting.
STEP technology consisting of on-lot processors and a single final-stage treatment facility. A United States Environmental Protection Agency Wastewater Technology Fact Sheet defines STEP as Septic Tank Effluent Pump.
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STEP operating costs and climate performance review needed
An estimate of on-lot STEP processor monthly operating expenses previously provided by one equipment vendor may be too low. The effect of high altitude and cold temperatures on STEP performance needs to be determined. Nearby rural community housing developments which have STEP or similar wastewater systems will be contacted to obtain real-world monthly operating costs and climate performance results.
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Seasonal water consumption may affect wastewater volume
The consumption demand placed on Town of Rico's water system varies by season. Seasonal home occupancy is 41% of total occupancy, stated Town Manager Kari Distefano. Summer water consumption is about one-half of Rico water system pumping capacity; winter consumption is one-third of capacity. Higher summer residential occupancy raises the summer monthly Rico water system consumption, and may cause higher wastewater volume.
Committee members recommended that seasonal monthly water consumption patterns be considered when equipment specifications for the proposed wastewater treatment system are prepared. Estimated irrigation (lawn sprinklers and gardens) water consumption may be deducted from summer monthly water consumption totals, as this use does not contribute to wastewater flows. The final-stage wastewater treatment facility or modules should accommodate seasonal variability, as well as Rico wastewater system expansion to residential areas, if needed or desired in the future.
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Effluent regulatory compliance
Committee members' meeting information packet included a September 2006 correspondence from CDHPE's Water Quality Control Division describing Preliminary Effluent Limits (PELs) for the Dolores River at Rico.
Rather than submit a formal application to CDHPE for a 2020 PEL, committee members proposed to request a verbal estimate of 2020 PEL, as well as changes expected to Colorado PEL standards later in the decade.
CDHPE's Dolores River-Rico PEL requirement will be provided to wastewater treatment system vendors for design and bidding. After vendors reply, Rico will submit a formal CPHPE PEL application.
The next Rico Sewer Committee meeting is June 4, 2020.
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Sewer Committee meeting notes
prepared by Alex Wing
- includes a few edits for clarity -
Items to define
What does build-out look like?
- How many taps?
- What flows summer vs winter will we provide to vendors?
- Kari to make map with build-out options.
What PELs to run with?
- Existing PELs.
- Contact Colorado Department of Health and Environment (CDHPE)
Ability to service whole town, be stepped down to facilitate phased approach.
- Meet PELs (need to nail down what we would use here). Ability to bring in additional unit processes/ops that will meet more stringent regs
- Meet effluent flow estimates
- Minimal space requirements on lot for onsite infrastructure.
- Works with very different summer vs winter flows/loading
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- Level of operator expertise required (and operator time)
- What equipment is needed on lot and size requirements? - residential vs commercial? For step systems, can existing tanks be used with a pump?
- What treatment takes place on lot (if any), what level of treatment takes place offsite?
- Maintenance requirements - reliability with minimal maintenance, costs and intervals?
- Performance at high altitude with cold temps (when flow/loading is lower by >41%)
Companies to contact
- BC Engineering Group - works with several vendors
- Pure Water in Ridgway - Chris Bolane - does OMM on Orenco systems - Pat will contact
Vendors to Contact
- Orenco step systems
- BioMicrobics - Biostep system
- E1 sewer systems (Lawson is an example - grinder pump system)
- (use existing estimate for comparison)
Action items before next meeting
A. Nail down PELs - Pat and Gregg.
- Need a PEL guess - Pat to talk with contact Amy Zimmerman at CDPHE for "ballpark numbers"
- Come up with a number that accounts for DR dilution and expectations of future regs
B. Nail down flows- Kari and Gregg
- Kari to send map to group and agree on build-out
- Extrapolate from expected build-out/# of taps
- Account for irrigation water demand (make assumptions and subtract out of total consumption of Rico water system)
C. Expand vendor list, contact vendors
- One committee member per vendor
- One committee member to find additional vendors