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 occurs when a reservoir is unable to provide sufficient water to meet demand”

Operating Range Historic Record WMA Firm Yield Treatment Plant (1909-2000) Registration Design Minimum 0.5 0.89 (avg) 0.86 (USGS) 0.5 (MDG) Maximum 2.0 2.0 1.27 (USGS) 1.5 (MGD)* 1.23 (DEP) * MGD = Million Gallons per Day

Operating Range Historic Record WMA Firm Yield Treatment Plant (1909-2000) Registration Design Minimum 0.5 0.89 (avg) 0.86 (USGS) 0.5 (MDG) Maximum 2.0 2.0 1.27 (USGS) 1.5 (MGD)* 1.23 (DEP) “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, * MGD = Million Gallons per Day both to be able to meet peak day demands and for redundancy in case other 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

Nagog Pond Water Level and Use Nagog Pond & Sandy Pond Nagog Pond & Wells 5 230 4.5 Water WIthdrawal (Million Gallons) 225 4 3.5 Elevation (NAVD 88) 220 3 2.5 215 2 210 1.5 Waiver 1 205 0.5 0 200 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 Avg. Daily Withdrawal (MG) Max Day Withdrawal (MG) Pond Elevation 12 per. Mov. Avg. (Avg. Daily Withdrawal (MG))

Historic Drawdown ~222 1960’s Drought ~218 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

Not to scale – for informational purposes only Intake Mean Sea Level Inlet Highest point NAVD 88 Treatment Plant 217.32 216.75 Gatehouse 211.27 210.7 Wet Well Intake Orifice of the “If the Town seeks to establish a higher firm yield for Nagog pipe in the pond 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

PROPOSED INTAKE PIPE TO MATCH EXISTING INTAKE PIPE INVERT ELEVATION IN UPSTREAM GATEHOUSE WALL

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.)