NAGOG POND WATER TREATMENT PLANT Acton Conservation Commission NOI - - PowerPoint PPT Presentation

NAGOG POND WATER TREATMENT PLANT

Acton Conservation Commission NOI Extension Request (Meeting 2) December 19, 2018

“The firm yield is the maximum average daily withdrawal that can be extracted from a reservoir without risk of failure during an extended drought period” “A reservoir failure

• ccurs when a reservoir

is unable to provide sufficient water to meet demand”

Operating Range Historic Record (1909-2000) WMA Registration Firm Yield Treatment Plant Design Minimum (MDG)

0.5 0.89 (avg) 0.86 (USGS) 0.5

Maximum (MGD)*

2.0 2.0 1.27 (USGS) 1.23 (DEP) 1.5

* MGD = Million Gallons per Day

Operating Range Historic Record (1909-2000) WMA Registration Firm Yield Treatment Plant Design Minimum (MDG)

0.5 0.89 (avg) 0.86 (USGS) 0.5

Maximum (MGD)*

2.0 2.0 1.27 (USGS) 1.23 (DEP) 1.5

* MGD = Million Gallons per Day

“Water suppliers commonly, if not always, plan to be able to pump above the “Firm Yield” rate from their surface water sources on any one day, both to be able to meet peak day demands and for redundancy in case

• ther sources must go off‐line for repairs, emergencies, etc. Pumps and

water treatment plants for surface water supplies are typically designed for a maximum day withdrawal rate, rather than an average day withdrawal rate.”

• MassDEP email to Acton Special Council Roelofs, 10/13/2016

200 205 210 215 220 225 230 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020

Elevation (NAVD 88) Water WIthdrawal (Million Gallons)

Nagog Pond Water Level and Use

• Avg. Daily Withdrawal (MG)

Max Day Withdrawal (MG) Pond Elevation 12 per. Mov. Avg. (Avg. Daily Withdrawal (MG))

Nagog Pond & Sandy Pond Nagog Pond & Wells Waiver

1960’s Drought ~218 Historic Drawdown ~222

Elevations based on NAVD 88

Safe Drinking Water Act Federal Mandate (310 CMR 22.20A)

• 1989 – Federal Promulgation of Rule
• 1991 – Consent Order issued to

Concord

• 1991 –Watershed Protection Plan
• 1996 – Enhanced Disinfection (ozone)
• 1992-2003 – Land Swap
• 2006 – Long-Term 2 Enhanced SWTR
• 2011-2012 – Nagog Dam

Rehabilitation

• 2013-2014 – Pilot Treatment
• Acton Conservation Commission (RDA)
• Mass DEP Drinking Water Program

Nagog Pond Water Treatment Plant Raw Water Intake – Existing Conditions

Intake

Not to scale – for informational purposes only Mean Sea Level NAVD 88 Inlet Highest point Intake Orifice of the pipe in the pond

210.7 217.32 216.75 211.27

Gatehouse Wet Well Treatment Plant

“If the Town seeks to establish a higher firm yield for Nagog Pond, or if the Town intends to install the new water intake at a lower depth than the old intake, then it will need to obtain an amendment to its Water Withdrawal Permit (BRP WM 02).”

• MassDEP Comments on DEIR

Temporary Cove Dewatering

• The intake construction approach includes the temporary

dewatering of the cove adjacent to the Nagog Pond Dam. The approach was conditionally approved under the Order of Conditions through Special Conditions No. 1 and 2:

• No. 1 – A detailed de-watering sequence and environmental impact

report shall be submitted to the Conservation review prior to the commencement of de-watering. The report will include an analysis of wildlife habitat impacts, both aquatic and buffer zone.

• No. 2 – At the applicant’s expense, a third party monitor, approved by

the Acton Conservation Commission, will be retained to be on-site periodically throughout the de-watering process. The monitor will be responsible for scheduling weekly meetings with the Acton Natural Resources Department to review environmental compliance.

The Town of Concord will comply with these special conditions.

Bald Eagles

Buffer Zones

• 330 ft. and 660 ft.
• Based on level of

disturbance

• Recommendations to

minimize impacts during breeding season Concord continues to coordinate with both DFW and MassWildlife

“…the Town of Concord is providing details on the proposed project to the Service as they become available and soliciting the Service's guidance on the "reasonable efforts to avoid disturbance." In this manner, the Town of Concord is performing their due diligence.”

• T. Wittig, US Fish and Wildlife (11/17/17 email to Brennan, et. al.)