Update on the Comprehensive Wastewater Management Plan

David Young, P.E.

Michaela Bogosh, P.E.

June 29, 2021

Select Board Meeting

Agenda

▪ Overview of the problem and sources

▪ Dennis’s Comprehensive Wastewater Management Plan▪ Non-infrastructure components

▪ Effluent Recharge

▪ Costs

▪ Next Steps

The problem

3

Dennis Watersheds

Controllable Nitrogen Sources –Swan Pond River Watershed

Overall Load

72%

3%

6%

12%

5%

2%

Wastewater

Landfill/Solid Waste

Fertilizers

Impervious Surfaces

Water Body Surface Area

"Natural" Surfaces

Stormwater

Watershed SepticLoad Reductions

▪ Figure shows required septic load reduction to meet Total Maximum Daily Load

6

Nitrogen Entering Our Groundwater from Title 5 Septic Systems

Is Our Biggest Issue

CWMP

8

CWMP and Program Status

▪ Draft CWMP submitted to Commonwealth of Massachusetts Environmental Policy Act (MEPA) Office and the Cape Cod Commission (CCC) (Summer 2017)

▪ Bass River Railroad/Cape Cod Rail Trail Bridge Abutment Widening (2016-2018)

▪ Economic Study conducted

▪ Aquaculture Pilot Project in Swan Pond (Summers 2018-2019)

▪ Initial Archeological Surveys of

future pumping stations completed

▪ Effluent recharge field

investigations (Aug. & Oct. 2020)

▪ Final CWMP to be submitted 20219

Watershed Septic Load Reduction Required

Bass River 60%

Herring River 58%

Swan Pond 100%

Chase Garden Creek

+24%

Sesuit Harbor Awaiting MEP Report

CWMP Alternatives

▪ Seven collection and treatment scenarios (1A to 7D) were initially evaluated based on:▪ Current and future community development

▪ TMDLs for embayments

▪ Seven screened down to five

▪ Scenario 6A was selected by WIC

▪ Highlights of Scenario 6A:▪ Meets MEP and TMDL nitrogen reduction thresholds;

▪ Allows for effluent recharge sites in multiple watersheds (Bass River and Swan Pond);

▪ Provides a phasing plan that provides for implementation flexibility;

▪ Allows for a potential regional solution between Dennis, Harwich, and Yarmouth; and

▪ Supports desired smart economic development.

10

Phasing Plan

11

1. Buildout Average Daily Flow with Planning District and I/I (GPD)

Phase Estimated Flow (gpd) 1

1 305,000

2 671,000

3 205,000

4 67,000

5 347,000

6 99,000

7 120,000

8 146,000

Total 1,960,000

Non-Infrastructure Components

▪ Public Outreach

▪ Fertilizer Education▪ Brochure

▪ Presentation

▪ Stormwater Best Management Practices

12

Swan Pond Aquaculture Demonstration Project

Route 6 Bass River Bridge(s) - Proposed Widening

14

▪ Potential solutions evaluated to help improve the Bass River water quality ▪ Removal of the flow restrictions from the former railroad bridge south

of Route 6 (completed) and the Route 6 east and west bound bridges

▪ Removing both restrictions would result in a 25 percent reduction in total time required to exchange water in that area

▪ Removing both restrictions will decrease concentrations by approximately 6-percent

▪ Removing restriction of railroad

bridge results in a 2-percent

reduction in concentration

Route 6 Bass River Bridge(s)- Proposed Widening cont.

15

▪ Larger restriction is from the Route 6 east and west bound bridge▪ Currently no plan to widen to pre-bridge conditions

▪ Reached out to MassDOT several times

▪ Dennis and Yarmouth in 2016

▪ Dennis, Harwich and Yarmouth in 2018

▪ MassDOT stated that bridge is neither functionally obsolete or structurally deficient and therefore will not be considered for widening at this time

Effluent Recharge and Recharge Sites

▪ Concentration of 35 mg/L-N in septic systems

▪ Wastewater Treatment Plant reduces concentration to 3 mg/L-N

▪ Treated effluent is sent to the subsurface

16

Effluent Recharge

DISCHARGE

Effluent Recharge Site Overview

17

DHY Shared Facilities Comparison

18

WWTF and

Effluent

Recharge Cost

Comparison

Capital Costs O&M Costs Equivalent Annual

Costs1

Annual Savings

Town Regional Town Regional Town Regional $ / year %

Dennis $109 M $72 M $5.0 M $2.8 M $9.9 M $6.0 M $3.8 M 39%

Harwich $82 M $44 M $2.8 M $1.7 M $6.5 M $3.6 M $2.9 M 44%

Yarmouth $152 M $136 M $9.6 M $5.0 M $16.4 M $11.1 M $5.3 M 32%

Total $343 M $252 M $17.4 M $9.5 M $32.8 M $20.7 M $12.0 M 37%

1. Equivalent annual costs based on 30-year loans at 2% interest.2. 2024 Costs with projected ENR of 13,060.

Dennis Recommended Program Comparison

19

Dennis Capital Costs O&M Costs

Equivalent Annual

Costs1

Annual

Savings

Town Regional Town Regional Town Regional $ / year %

Collection System $225 M $225 M $2.8 M $2.6 M $12.8 M $12.7 M $0.2 M 1.2%

WWTF $71 M $49 M $4.7 M $2.5 M $7.9 M $4.7 M $3.2 M 41%

Effluent Recharge

with PRB$39 M $24 M $0.3 M $0.3 M $2.0 M $1.3 M $0.7 M 34%

Non-Traditional

Technologies$10.4 M $10.4 M $0.1 M $0.1 M $552,000 $552,000 $0 0%

Total $345 M $308 M $7.9 M $5.5 M $23.3 M $19.3 M $4.1 M 17%1. Equivalent annual costs based on 30-year loans at 2% interest.2. 2024 Costs with projected ENR of 13,060.

Dennis Recommended Program - Phase 1

20

DennisCapital Costs O&M Costs

Town Regional Town Regional

Collection System $49.0 M $49.0 M $ 0.70 M $ 0.61 M

WWTF2$53.5 M $39.1 M $ 0.74 M $ 0.39 M

Effluent Recharge with PRB $20.7 M $12.7 M $ 0.16 M $ 0.10 M

Non-Traditional Technologies $1.3 M $1.3 M $ 86,400 $ 86,400

Total $124.5 M $102.1 M $1.69 M $1.18 M 1. 2024 Costs with projected ENR of 13,060.2. Estimated design flow of 1.3 MGD

Next Steps

21

Next Steps

▪ WIC endorsed Town-only solution in March 2021 Meeting

▪ Need confirmation from Select Board

▪ Finalize CWMP

▪ Begin following next WIC Meeting, July 12th

▪ 2 months

▪ MEPA begins review upon submission of CWMP

▪ 30-40 days to issue certificate

▪ CCC begins review following MEPA Certificate

▪ 208 Consistency Plan Review completed to become eligible for 0% interest State Revolving Fund (SRF) loans

▪ 30-40 days to review

▪ ~5 months to finalize CWMP process and receive final approval

▪ Mid November 2021

Questions?