ITB_24_069 Addendum 3.pdf

Addendum Number 3

Invitation to Bid (“ITB”) 24-069

Lisa Lane Pond Rehabilitation Project

COMPLETE THIS ADDENDUM, SIGN and SUBMIT with the ITB

RESPONSE DUE DATE: June 21, 2024, 2:00 p.m.

To All Prospective Offerors: In reference to the ITB listed above, the following answers to questions, additions, deletions, and change are hereby incorporated into the ITB:

**Questions**

Number Question Response

1. When does the City of Sandy Springs anticipate to issue NTP?

The NTP will be issued immediately after the Purchase Order is issued.

2. Is contractor responsible for testing? If so, what kind of testing will be required for concrete or any other materials subject to QA Control?

Yes, concrete testing for the wall will be required to meet GDOT specifications for Type A Concrete.

3. Why is this project being re-bid? Funding restraints.

4. Is there any soil report available? No.

5. Is there any hydrological report available to determine runoff conditions?

Yes, see Exhibit A

6. What is the area of the basin draining towards the pond? Is its runoff coefficient available?

The total area draining to the pond is 58-acres. 17-acres is pavement while the remaining 41-acres is a mixture of grass/trees.

7. What is the current level of water in the pond? Contractor shall verify before bid.

Another on-site visit would need to be coordinated to visit.

8. Watermann Water Quality systems seem to be no longer used in the industry, does the City have any approved supplier / alternate for this item?

Watermann will need to be constructed by the contractor out of PVC or the existing Watermann can be salvaged. The Watermann doesn’t have a patent anymore. The City will consider alternatives provided by contractor.

9. Will any kind of NPDES or water monitoring be required?

No.

10. Sing in sheet posted online says Bid Due Date is July 21st 2024. Bonfire and other addenda documents say its June 21st 2024. Please clarify exact bid due date.

Bid due date is June 21, 2024.

11. What kind of rock / granular material should be used (if deemed necessary by the Engineer) for the wall’s foundation 3FT undercut backfill? Is there any specs / testing to comply with?

GDOT Foundation Backfill Material, Type II would be required. Testing will be performed by the City, as required.

12. Is there any DBE/SBE/WBSE or any other minority requirement?

No, there are not minority requirements.

13. What should be the percentage for the payment and performance bonds? On ITB Document is not shown.

The percentage for both bonds is 100% of the contract amount.

14. What is the material for the existing wall to be demolished and removed? Does it contain rebar embedded?

Rock, stone, concrete, and reinforcement steel are anticipated to be removed.

15. Would the city consider use of ashlar formliner concrete finish in lieu of the ashlar façade and capstone items?

The City may consider concrete ashlar finish in lieu of veneer. If approved the veneer line item would not be eligible for payment.

16. What other documents, excluding the initial bid, would we need to supply before signing a contract?

Please review the bidding on instructions on pg. 5 of the ITB.

17. As a registered DBE, seeing that this is a government project, could that bring us any advantage in the decision making process?

The city currently doesn’t have a DBE policy.

18. What is the extent of tree removal required behind the wall?

Minimal, scope is limited to within the existing easement. Most of the interior basin trees were removed in 2011 during the initial retrofit. Trees removed within Right-of-Entry (ROE) limits are up to the contractor;

however, depending on the extent of damage, damaged trees may need to be removed and stumps ground.

19. Will we be accessing the site from a private residence driveway?

Contractor shall provide a construction exit within the existing easement. A bid item is included in the bid for this. A right of entry, pending homeowner approval, will be provided for the convenience of the contractor.

20. If the private residence driveway is used for access, will replacing the concrete driveway be covered under contingency?

No. The contractor is responsible for any needed repairs. The cost of restoration of driveway must be included in the grading complete item.

21. Will the driveway be able to be protected during construction?

This is recommended. Contractor shall still construct a construction exit within the existing easement.

22. Will additional riprap be placed in the outlet, or can the existing rock be used to line the outlet area?

Existing rock can be used to line the outlet area.

23. Instead of installing Ashlar granite on the concrete wall, can an Ashlar form lining be used on the concrete wall?

The City may consider concrete ashlar finish in lieu of veneer. If approved the veneer line item would not be eligible for payment.

24. Will a Geotechnical report be provided for this project?

No.

25. What will be the protocol if we encounter rock during excavation or construction?

Rock removal will not be paid with additional funds. Rock removal would be paid for under grading complete.

26. Will Geotechnical testing for compaction and concrete be required?

Only for concrete, see response #2.

Exhibit A

City of Sandy Springs, Georgia 6775 Lisa Lane Detention Pond

HYDRAULIC AND HYDROLOGICAL STUDY

PREPARED BY:

1634 White Circle, Suite 101 Marietta, GA 30066

(770) 421-8422 phone www.aei.cc

March 15, 2011

6775 Lisa Lane

City of Sandy Springs, Georgia

HYDRAULIC AND HYDROLOGIC REPORT

LOCATION

This project is located near 6775 Lisa Lane in Sandy Springs, Fulton County, Georgia. Lisa Lane is located just off of Mt. Vernon Highway, north of Abernathy Road and just east of SR 400 / US 19. It is north of I-285. See the location map below:

LOCATION MAP FOR LISA LANE DETENTION BASIN

Location of

Detention Basin

EXISTING CONDITIONS

The existing drainage facility is classified as a dry detention basin. The basin is approximately 0.2 acres and contains runoff from a drainage basin of 58.0 acres and resides in the backyard of the residence of 6775 Lisa Lane. There is a 18-inch CMP and 48-inch CMP that drains into this detention basin, both coming from Lisa Lane. The existing basin is contained within an existing drainage easement. It also contains large trees, 2-ft. to 3-ft. of sedimentation and debris.

The existing outfall structure is a special designed concrete block wall as shown above and contains a V-notch weir design. The concrete block wall is 66-ft. in length, 8-ft. in height and 2-ft. in depth. The existing detention outfall structure is in average to poor condition however appears to be functional adequately. The pictures below show the existing detention basin and outfall structure.

EXISTING DETENTION STRUCTURE

EXISTING OUTFALL STRUCTURE EXISTING OUTFALL STRUCTURE

LOOKING INSIDE BASIN FROM OUTFALL STRUCTURE

PURPOSE

This project will create watershed improvement plans for the City of Sandy Springs for compliance with the City’s National Pollutant Discharge Elimination System (NPDES) Phase II Municipal Separate Storm Sewer System (MS4) Permit. The Georgia Environmental Protection Agency requires that municipalities with Phase II permits within the Metropolitan North Georgia Water Planning District (District) be in compliance with the District-Wide Watershed Management Plan. One of the elements of the plan is the development and implementation of watershed improvement plans.

BACKGROUND

The City of Sandy Springs became the second largest City in metro Atlanta upon incorporation in December 2005. Since that time, the City has implemented a variety of new programs and processes. In the fall of 2006, they applied for and received coverage under the NPDES Phase II MS4 permit program for the City’s stormwater conveyance system. This action was a requirement in taking over certain permit activities from Fulton County. The permit allows the City to discharge stormwater into waters of the State of Georgia. As such, the City must meet specific program operating goals and standards. Specific goals must be met in 6 key areas: public education and outreach, public involvement/participation, illicit discharge detection and elimination, construction site stormwater runoff control, post-construction stormwater management and pollution prevention/good housekeeping for municipal operations. In addition to these specific NPDES permit requirements, the City is also required to meet the requirements of the Metropolitan North Georgia Water Planning District (MNGWPD), which include industrial inspections, completion of the MS4 inventory, floodplain mapping, and Total Maximum Daily Load (TMDL) plan implementation.

A stormwater conveyance system consists of connected structures that collect stormwater at one or more locations and discharge it at a single outfall, typically to a stream or drainage channel. The system’s structures include pipes, manholes, catch basins, culverts, and open channels. As part of the NPDES Phase II MS4 Permit, the City must develop and implement an extensive nonpoint source pollution program described above.

Discharges of untreated and unmitigated stormwater to the separate storm sewer system contribute to increased nonpoint source pollution and degradation of receiving waters. Nonpoint source pollution is increased from spills, dumping and improper connections to the storm sewer system from residential, industrial, commercial or institutional establishments. The impacts of nonpoint source pollution and stormwater runoff adversely affect public health and safety, drinking water supplies, recreation, fish and other aquatic life, property values and other uses of lands and waters.

The City has seven stream segments that are listed on the Georgia 303(d) list as not meeting their designated uses. Total Maximum Daily Load (TMDL) Implementation Plans have been developed for these watersheds.

The segments are:

• Ball Mill Creek

• Chattahoochee River (South of Dam)

• Chattahoochee River (North of Dam)

• Crooked Creek

• Long Island Creek

• Marsh Creek

• Nancy Creek

All segments are listed for fecal coliform. Long Island Creek and Nancy Creek are also listed as partially supporting due to Biota Impacted.

In the late 1990s and early 2000s, Fulton County initiated studies to produce water resource management plans. The plan that covered the area that is now the City of Sandy Springs was titled Sandy Springs Water Resources Management Plan and was completed in March 2001 by a joint venture headed by Brown and Caldwell. The plan included Watershed Management Plans of the area. This project will update the plans to create Watershed Improvement Plans (WIPs) specifically in the basins that have TMDL Implementation Plans for pollutants of concern other than Fecal Coliform.

PROPOSED IMPROVEMENTS

Proposed Improvements for Water Quality - In order to bring the detention basin into compliance with the NPDES Phase II MS4 Permit, we propose modifying the existing dry detention basin into an extended dry detention basin. In doing this, the water quality component of the detention facility will be incorporated into the existing detention basin. Specifically, we propose using a Watermann Water Quality Device or equivalent near the proposed detention outfall structure. Additionally, the existing basin will be re-graded and cleaned-out to provide the necessary water quality volume and storage volume for peak flow runoff.

In order to determine the volume of water that needs to be treated for water quality, we used the following calculations for this basin:

Calculate Water Quality Volume (WQV) Total Drainage Basin = 58.0 acres For the 58.0 acres Pavement = 17.0 acres Grass/Trees = 41.0 acres

RV = 0.05+0.009(I) = 0.05+0.009(17/58 x 100%) = 0.314 WQV = (1.2RVA)/12 = (1.2*0.314*58)/12 = 1.82 acre-feet

This shows the water quality volume to be 1.82 acre-feet for the first 1.2-inch storm. Now we calculate the required orifice diameter required to release the 1.82 acre-feet over a 24-hour period:

Calculate the Required WQV-ED Orifice diameter to release 0.327 ac-ft over 24-hours Average ED release rate = (1.82 ac-ft)(43560 ft2/ac)/(24 hr)(3600 sec/hr) = 0.92 cfs Average head = 1.5 ft.

Q = CA(2gh)0.5 A = 0.92/[(0.6)((2)32.2 ft/s2)(1.5 ft))0.5] = 0.16 ft2, A=пd2/4 Diameter = 0.46 ft = 5.5”

Use 8” pipe with 8” gate valve to achieve equivalent diameter

Water will be released from the outlet structure through an 8” pipe to achieve the required diameter to release 1.82 ac-ft over a 24-hour period.

DRAINAGE AREA MAP – See plan package for drainage area map.

MAINTENANCE PLAN – There is not an easy way to access the existing structure and pipe. In order to give access to City Personnel for both construction and future maintenance of the pipe, an existing easement is located at the effected property as shown on the construction plans. Additionally, we propose the following schedule for maintaining the extended dry detention basin to ensure it is functioning properly:

ACTIVITY SCHEDULE

• Note erosion of banks or bottom

• Maintenance of Watermann or approved equal Semi-annual Inspection

• Inspect for damage to embankment

• Monitor for sediment accumulation

• Check to ensure the inlet and outlet devices are debris-free

Annual inspection

• Repair eroded area

• Mow side slopes

• Litter and debris removal

• Pesticide / nutrient management

Standard Maintenance

• Seed to restore damaged ground cover Annual maintenance or as needed

• Remove sediment from forebay area 5 to 7 year maintenance

• Monitor sediment accumulations and remove sediment when pond volume has been reduced by 25% 25 year maintenance

I hereby acknowledge receipt of Addendum Number 3 for #24-069 Lisa Lane Pond Rehabilitation Project and have incorporated the changes into my response for the above-mentioned Invitation to Bid.

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