Attachment_1_-_Statement_of_Work.docx

DEATH VALLEY NATIONAL PARK

Repair Wastewater Lagoon and Access Road at Stovepipe Wells

PMIS NO. 339146

PROJECT SCOPE OF WORK

NATIONAL PARK SERVICE PACIFIC WEST REGION

August 2, 2024

THIS PAGE INTENTIONALLY LEFT BLANK

PMIS 339146 / Repair Wastewater Lagoon and Access Road at Stovepipe Wells Death Valley National Park

1.0 Overview

In late August, 2023, the Park experienced a historic flood event. This flood event severely damaged Park infrastructure. The Park has a two-cell evaporative/percolation wastewater lagoon at Stovepipe wells. This lagoon berms were severely damaged by the stormwater. Large, eroded flow channels are now present. The NW corner of the lagoon was eroded away causing the exterior fence to fall down. On three sides of the lagoon site, the berm tops, which serve as vehicle access around the site, are now sloped towards the lagoon cells and need to be graded to slope away from the lagoon cells to direct stormwater away from the lagoon cells. Approximately 300 lf of the access road was also damaged. It has been temporarily repaired. The access road was damaged by flooding, is in need of repair, requiring also one new drainage structure and new inlet/outlet works at one existing culvert.

The purpose of this project is to restore the lagoon by repairing the erosion damage, make permanent repairs to the access road and drainage features, remove invasive vegetation, recompact the lagoon berms, re-grade the site, and replace the section of downed fence.

2.0 Project Location

The lagoon is located near Stovepipe Wells at approximately the following coordinates:

Latitude: 36.610413° Longitude: -117.144512°

LOCATION OF PROJECT

Figure 1: Map showing approximate location of the wastewater lagoon.

3.0 Scope of Work

Figure 2: Map showing proposed work. Berm damage shown in Figure 3.

A B C

D E

Figure 3: Stovepipe Wells two-cell lagoon site showing erosion damage to lagoon berms. Vegetation to be removed.

· Collect a soil sample from the existing lagoon berm material and perform laboratory analysis of the soil particle size distribution. Select an import material that has a similar particle size distribution and similar color to the existing berm material. Follow submittal requirements for laboratory results, physical samples, and source invasive species inspection.

· Select material for road reconstruction that meets the specified requirements and is similar in color to the existing road material. Follow submittal requirements for laboratory results, physical samples, and source invasive species inspection.

· Repair erosion on lagoon berms:

· Erosion channels (6 inches to 2 feet in depth, various widths) are present on the berms of both lagoon cells.

· Fill erosion channels, compact, and regrade berms to match existing slope.

· Remove all vegetation from the interior face of the lagoon berms and dispose of it outside of the park.

· Approximately 500 CY of soil required to repair erosion.

· Replace fencing and repair erosion at NW corner of lagoon site:

· Approximately 160 CY of soil required to repair the eroded lagoon corner.

· Downed fence shall be replaced with approximately 670 LF of 6’ high chainlink. Fence posts to be set 3’ in the ground and set with concrete. Fence shall have top rail, bottom tension wire, and ends of new fence line shall have horizontal brace and truss rod.

· Fence corner posts shall be 2-3/8. Line posts, top rail and braces shall be 1-7/8. All shall be galvanized steel.

· Place 6” of gravel under each post.

· Regrade access road on top of lagoon berms and outer slopes of berms

· Site is approximately 3.3 acres.

· Regrade and compact approximately 4,000 SY of roadway at 3% slope, sloping away from the lagoon cells, on 3 sides of the site, to restore a 14’ wide vehicle access surface.

· Regrade center berm so it is crowned in the middle and compact.

· Regrade exterior berm slopes (beyond the 14’ access surface) to no more that V:3H, tapering the soil so that it intersects the fence line no more than 2” below the bottom wire.

· On the exterior of the fence, clear vegetation within 8’ of the fence and regrade the exterior perimeter so that the soil slopes away from the fence and intersects the fence no more than 2” below the bottom wire.

· Repair lagoon access road

· The lagoon access road is approximately 20’ wide and 885lf, inclusive of a cul-de-sac located just outside the lagoon perimeter fence.

· Rebuild 60 lf of the top 2’ of access road by excavating the material and replacing it with NDOT Type II aggregate road base material.

· Regrade the entire length of the road.

· Replace flare ends and install 8’ of riprap scour protection at the inlet and outlet flow channel of the existing 36” HDPE culvert.

· Install a new concrete “arched” culvert under the access road, at the wash that begins approximately 250’ from the cable gate at the campground. Culvert shall be not less than 36”x29” and extend 4’ beyond the toe of the road embankment slope on both upstream and downstream ends. Scour protection shall be installed for a distance of 8’ from both ends of the culvert. Contractor to field verify necessary length of culvert, approximately 44 lf.

· Contractor to locate the underground power service prior to excavating for drainage structures.

· Existing sewer main is approximately 30’ southeast of the access road centerline, roughly parallel to the access road.

Figure 4: Fence and berm damage at the NW corner of the lagoon.

Figure 5: Lagoon Access Road

4.0 Definition of Contract Line Items

Contract Line Item No. 01 – Lagoon Berms All excavating, backfill, compaction, grading, soil, hauling, devegetation, disposal, labor, materials, and appurtenances to complete the work as specified.

Contract Line Item No. 02 – Lagoon Fence and Erosion Repair at NW Corner All excavating, backfill, compaction, grading, fill, hauling, disposal, concrete, gravel, labor, materials, and appurtenances to complete the work as specified.

Contract Line Item No. 03 – Access Road and Drainage Structure All excavating, backfill, compaction, grading, fill, hauling, disposal, concrete, gravel, labor, materials, and appurtenances to complete the work as specified.

5.0 Technical Details

1. Contractor shall field verify the quantity of soil required to repair the erosion and communicate this quantity with NPS.

2. Contractor shall follow and abide by the attached Death Valley Invasive Species Policy for construction equipment and commercial trucks entering the park.

3. Contractor to take and submit to NPS 20 annotated photos showing completed repairs of the lagoon, fence, access road, and drainage structure.

4. Contractor to clean site after completion of project.

5. Contractor to coordinate with Park for access to lagoon; lagoon has a gate to the facility as well as a wire gate on the access road.

6.0 Submittals

Contractor to provide the following submittals to NPS for review and approval:

a. Imported Backfill Soil

i. Laboratory analysis results for particle size distribution and proctor

ii. Two 5 gallon buckets of the proposed material for color approval

iii. Name and location of source pit, point of contact at source pit

iv. Plasticity index of proposed soil backfill material.

v. See Section 312000 Earth Moving for approved material type

b. Riprap Laboratory analysis results for particle size distribution and proctor

i. Material size range

ii. Samples for color approval

iii. Name and location of source pit, point of contact at source pit

iv. See Section 312000 Earth Moving for approved material type

c. Concrete

i. Proposed concrete material

d. Fencing materials

e. Culvert

7.0 Attachments

1. DEVA Standard Specifications

2. SOP - Invasive Species - Death Valley 2020

3. SECTION 312000 Earth Moving image1.png image2.jpeg image3.jpeg image4.jpg image5.jpeg image6.jpeg image7.jpeg image8.jpeg image9.jpeg image10.jpeg image11.jpeg image12.jpeg image13.jpeg image14.jpeg image15.jpeg image16.jpg