1

OConnor, Michael

From: James Coffin <jcoffin@coffineng.com>

Sent: Thursday, May 18, 2017 2:43 PM

To: OConnor, Michael

Cc: Josh Platt (info@mesmaine.com)

Subject: Masse Dam Removal

Attachments: DEP Response.pdf; Attachments 7&8.pdf; DEMO.pdf; C-2.pdf; C-3.pdf; C-4.pdf

Hi Mike,

I’ve attached the information that you asked for in your letter dated May 1st

for the Masse Dam removal. Let me know if

you have any questions.

Thanks,

Jim

James E. Coffin, P.E. Vice President E.S. Coffin Engineering & Surveying, Inc. P.O. Box 4687 432 Cony Road Augusta, Maine 04330

(207) 623-9475 Phone 1-800-244-9475 Toll Free (207) 623-0016 Fax

jcoffin@coffineng.com

432 Cony Road (207) 623-9475 P.O. Box 4687 Fax (207) 623-0016 Augusta, ME 04330 1-800-244-9475

Professionals Delivering Quality Solutions H:\Land Projects 3\16049\DEP\DEP Response.doc

May 18, 2017

To: Michael O’Connor, Licensing Project Manager

Bureau of Land Resources, Land Division

17 State House Station

Augusta, Maine 04333­0017

Re: DEP Application #L­27396­3E­A­N

Masse Dam Removal

Vassalboro, Maine

Dear Mr. O’Connor,

I have reviewed your letter dated May 1st

, 2017 in regard to the Masse Dam Removal Project and the

Full NRPA permit application that has been submitted to the DEP. The DEP has requested additional

information for the following:

1. Update Attachment 1 and Plan Drawings to include dimensions of Masse Dam and the

dimensions of the dam section you propose to remove.

We have added another detail sheet (C­4) that depicts the dimensions and sections of the

dam that will be removed. In addition the length (39.78’) is depicted on the DEMO Sheet.

2. Update Plan Drawings depicting the location of the cofferdam and pump as well as the

route of the pumped water. Also update Attachment 8 with cofferdam details.

We have added a cofferdam and pump onto the Demo Plan (DEMO) and updated

Attachment #8 with the dewatering notes. We do specify the type of cofferdam as either

concrete waste blocks or sandbags wrapped in poly. We also show where the cofferdam

is located along with the pump, sediment forebay, etc. A detail of the sediment forebay

and spillway have been added to Sheet C­3.

3. Provide additional information in Attachment 7 including estimated timeframes and

detailed descriptions for each step. For example, under “de­watering of the construction

site with cofferdam and pump”, provide a description of when this action will approximately

occur; the size, composition, and location of the cofferdam; where the water will be

pumped downstream; time it will take to construct and dewater the work zone; etc. Please

provide this level of detail for each step of the remaining work listed in Attachment 7.

This information has been added to Attachment #7.

This concludes our response to your letter and if you have any questions, please feel free to call

me at 623­9475.

Sincerely,

James Coffin, P.E.

Attachment 7 – Construction Plan/Sequence

Removal of the Masse Dam and adjacent buildings will be accomplished using a multi­step

process which will include the following:

� Stream draw down ­ 7/20/2016

� Removal of the sawmill building and adjacent building to the south – 8/30/2016

� Revegetation planning with residents – 9/2016

� Seeding exposed banks with annual cover crop – 9/2016

� Work done in 2016 was completed under a DEP Permit by Rule

Remaining work will take place during the construction window in 2017.

De­watering of the construction site with coffer dam and pump. This work will take

place immediately once the contractor arrives on site. A pooling area will be dug

adjacent to the cofferdam. The cofferdam can be constructed out of a variety of

different methods, but Cross Excavation will utilize stacked concrete waste blocks

(3’x6’x2’) or one cubic yard stacked sandbags, both of which will be wrapped with poly

up and over the top and keyed in at the bottom. The cofferdam location is shown on

the DEMO Plan along with the pump and hose. The water will be pumped out of the

cofferdam and into a sediment forebay immediately downstream from the work. The

forebay will allow solids to settle out and then the water will go through the spillway

and into the stream. A turbidity curtain provides the last measure of treatment before

flowing off­site. The time for this work is heavily dependent upon the water level

behind the dam and the weather, where rain will result in the work being prolonged.

Removal of existing dam and sluiceway down to original ledge. Once the water level has

been reduced, the dam and sluiceway removal will begin and this work should take no

more than three days. A hoe ram will be used to break up the dam and sluiceway and

then an excavator will load the rubble into dump trucks where it will be trucked away.

Stabilizing banks and existing retaining walls. Repairing the existing retaining walls and

Grist Mill foundation wall will also take place in dry conditions and will take one to two

weeks to complete. This involves the re­use or replacement of existing granite blocks

and filling in the voids with mortar. The retaining walls will also have a perforated 4”

diameter underdrained installed to alleviate hydrostatic pressure.

Final grading and seeding of site along with removing cofferdam, turbidity curtain,

sediment forebay, etc. This work will take three to seven days to complete depending

on weather conditions. It involves removing the cofferdam, turbidity curtain, filling in

the sediment forebay and pooling areas. Once complete the loaming and seeding of all

disturbed areas will take place. Hay mulch will be placed once the seeding is complete.

Watering will be needed on a daily basis to assure growth.

*Rebuilding of existing retaining walls along sections of north and south side of stream will

primarily utilize stone from existing wall for rebuild (See plan C­3).

Attachment 8 – Erosion & Sedimentation Control Plan

The Erosion & Sedimentation Control Plan is included as Sheet C­2. A dewatering section has

been added to Sheet C­2 that explains how to dewater the site. The contractor will likely utilize

concrete waste blocks wrapped with poly and keyed in at the bottom for the cofferdam

construction. If not then sandbags wrapped with poly will be installed the same way as

mentioned above.