3._Executive_SummaryRev01.pdf

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I. Executive Summary

A. Goals and Needs:

Goals for the project include upgrades and improvement at a variety of locations due to flooding, erosion, and other deterioration caused by stormwater systems. The work includes repairs to four primary areas outlined and described as Site Areas A, B, C, and D.

Work is expected to be accomplished as maintenance work under the existing Nationwide Permit. All jurisdictional wetland determinations have been obtained as has a state water determination. Stream buffers will be required. Project design decisions will be impacted by the Environmental Impact Analysis. New DNR and notification documents are included and NPDES and land disturbance permits or variances are anticipated. A PCN (Pre-Construction Notification) will be submitted to the USACE Savannah District for the project. Before any project work begins, a letter from the USACE Savannah District shall be received determining Nationwide Permit(s) applicability and conditions based on the submitted PCN.

B. Existing Conditions:

Area A:

Both the north and south side of Gym road is severely eroded due to lack of stabilization and storm water conveyance. The north side has a drainage swale between the roadway and sidewalk which fills up with sediment.

The sidewalk separates two swales which are linked together at the bottom of the slope with a culvert which is not functioning.

Area B:

A stream adjacent to Bldg 600 is currently being piped under the parking lot. On the downstream side of the pipe the discharge has caused erosion around and under a retaining wall. Also the velocity of the discharge has caused a separate channel to be created diverting the flow directing into Little Lake. Originally the stream bypassed Little Lake, as delineated on the drawings.

Area C:

The existing drainage channel alongside Spill Pond 3 has large amounts of sediment limiting the required flow during certain storm events. The upstream flow goes directly into Spill Pond 3 by being blocked, from the drainage channel, by a weir wall. This weir wall was constructed in the

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1970s and reconstructed in 2011 to allow the larger storm events to bypass the spill pond and flow directly through the drainage channel.

Area D:

The site adjacent to the running track is used for USAF Civil Engineering training. Due to the heavy equipment movement the area stays disturbed.

Rills have developed and sediment is being discharged into the downstream wetland.

C. Scope of Demolition:

Demolition for all four sites typically includes removal of silt and regrading. Some piping and inlet construction portions of other construction, including sidewalks, will be removed as necessary in the process.

D. Scope of New Work

Area A:

The proposed improvements include the construction of 24” concrete curb and gutter along both sides of Gym road from the second entrance to the parking lot for Building 401 down to the Rottenwood Creek crossing. On the northern side of Gym Road the area between the new curb and gutter and the existing sidewalk will be filled and graded to provide a positive slope for stormwater conveyance to the road. On the opposite side of this existing sidewalk, the existing drainage swale will be armored with stone to not only eliminate the erosion, but to also slow the velocity of the drainage conveying down the steep slope towards Rottenwood Creek. At the end of the curb and gutter (northern side), the existing inlet and piping will be removed and replaced with a a new curb inlet and drainage piping to direct the road drainage back to the armored swale allowing the drainage to flow to Rottenwood Creek. On the southern side of Gym Road the area behind the new curb and gutter will be graded back to the existing drainage swale.

Area B:

The proposed improvements include the re-grading of the existing drainage feature that originally conveyed the drainage from Building 600.

The construction of a berm across the separate channel will also be included, thus blocking the drainage from diverting into Little Lake.

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Area C:

The proposed improvements include the removal of all debris in the existing drainage channel alongside Spill Pond 3 from the existing weir structure to the drainage pipes under Atlantic Avenue and re-grade to provide a positive constant slope. The new channel shall have a 5’ wide bottom and 5:1 side slopes for maintenance availability.

Area D:

The proposed improvements include the removal of a portion of the existing earth mound providing a 27’ wide buffer between the toe of the earth mound and the existing tree line. Also to prevent further erosion encroachment into the wetland area, jersey barriers shall be placed along the top of the bank at the existing tree line.

E. Construction Cost Analysis

The contractual budget for the work is $564,500. The final estimate is $408,857.27. Even at 10% the project would remain under budget.

G. Project Schedule

We are anticipating 1 week of review and 15 more days to Final Submittal, project design should be complete around 30 November 2013.

Assuming 4 months of contracting and 6 months of construction, work could complete by third quarter FY14.