cherry creek basin water quality authority · 2016-01-13 · cherry creek basin water quality...

1

CHERRY CREEK BASIN WATER QUALITY AUTHORITY

TECHNICAL ADVISORY COMMITTEE

MEETING AGENDA Date: Thursday, January 7, 2016 Time: 8:30 AM Place: CliftonLarsonAllen LLP 8390 E. Crescent Parkway, Suite 500 Greenwood Village, CO 80111-2814, (303) 779-4525

Regular Meeting 8:30 – 9:30 Call to Order Action Items

1. Approval of November 5, 2015 Minutes and December 3, 2016 Minutes (Chuck, 2 minutes, emailed separately)

2. TAC recommendation to Board re: 2016 SAP Contractor Interview Team Recommendation (Rich Borchardt and Max Grimes, 15 minutes)

3. Executive Session Determining Positions Relative to Matters That May be Subject to Negotiations, Developing Strategy for Negotiations and Instructing Negotiators Regarding the 2016 Sampling and Analysis Program Contract Pursuant to C.R.S. § 24-6-402(4)(e) (Chuck, 25 minutes)

Presentation Cottonwood W&SD Selenium Treatment Evaluation/Future Plans (Pat Mulhern

(CWSD), Sarah Foster or Jim Bays (CH2MHill), 10 minutes, attachment) Cherry Creek Stewardship Partners Report (Casey, 2 minutes) Capital Project & Maintenance Report CIP Status Report (Jim, 3 minutes, attachment) 2015 Destratification System Annual Report (Jim, 3 minutes, attachment) Cherry Creek at Hess Road Project Summary (Jim, 1 minute, attachment)

Monitoring Report (Craig, 2 minutes, 2 attachments) January Regulatory Report (0 minutes, see attachment)

Management Scenario Identification 9:30 – 11:00 TAC Identification of 5 Recommended Management Scenarios for Reservoir Modeler to evaluate under original contract (Rick facilitates, 90 minutes, attachment)

**Please review the attachments and identify up to 5 model runs before the meeting**

2

Adjournment

Attachments: November 5, 2015 Meeting Minutes (emailed separately) December 3, 2015 Meeting Minutes (emailed separately) Cottonwood Water & Sanitation District Report 2015 Capital Project and Maintenance Status Report , December 24, 2015 2015 Destratification System Annual Report Cherry Creek at Hess Road Project Summary Memo, December 21, 2015 Water Quality Data (Two Attachments) January Regulatory Update

Management Scenario Attachments: Potential Management Scenarios for Reservoir Model Questions for the Reservoir Model

BIOLOGICAL TREATMENT OF SELENIUM IN CONCENTRATE

1

Biological Treatment of Selenium in Concentrate PREPARED FOR: Pat Mulhern/Cottonwood Water & Sanitation District

COPY TO: Luis Tovar/Cottonwood Water & Sanitation District

PREPARED BY: Jim Bays/TPA, Samantha Richardson/DEN, Sarah Foster/DEN

DATE: November 12, 2015

PROJECT NUMBER: 665165

REVISION NO.: 1

Executive Summary The Cottonwood Water and Sanitation District is investigating the potential for cost‐effective treatment of selenium in the concentrate from the Joint Water Purification Plant (JWPP) using passive biological systems. Biological systems include open aquatic systems such as ponds and constructed wetlands, and biochemical reactors, which include enclosed beds of engineered soil, gravel or organic media to create anaerobic environments for microbial treatment. Recent progress in the use of treatment wetlands and anaerobic biochemical reactors (BCR) for selenium treatment indicates that there is potential for a successful application of these technologies to treat JWPP concentrate.

Three conceptual alternatives utilizing passive biological treatment were developed for performance and cost comparisons based on assumptions of varying source waters, flow rates, and selenium concentration: Alternative 1 ‐ Selenium Biochemical Reactor Treatment; Alternative 2 ‐Constructed Wetland Treatment; and Alternative 3 ‐ Selenium Biochemical Reactor and Wetland Treatment. Given an assumed flow of 0.95 mgd of concentrate from 83% RO recovery from current source wells, a sizing analysis indicated that Alternative 1 (a 6.0 acre biochemical reactor treatment wetland system) could meet the average discharge criterion of 4.6 µg/L at a conceptual cost of $4,099,000 (including contingency) and a conceptual annual operational cost of $115,000. Phosphorus would be controlled from the selenium treatment wetland to be at, or lower than, background stream concentrations.

During this analysis, a preliminary review of selenium concentrations from regional stream monitoring data indicated that Lone Tree Creek removes selenium consistent with published information on selenium treatment wetlands, even after accounting for dilution. These local data confirm that selenium can be treated passively by a biological process, and suggest that existing best management practices such as on‐line treatment wetland intended for phosphorus removal also provide selenium removal.

Based upon the results of this feasible study, CH2M recommends that the following activities and steps be implemented to further the biological treatment system project.

1. Meet with the Colorado Department of Public Health and Environment (CDPHE) to review regulatory status and confirm data needs and regulatory constraints.

2. Determine the feasibility of procuring the six‐acre parcel.

3. Plan and implement a pilot investigation of the proposed BCR system configuration. Conduct the pilot at the JWPP site using concentrate generated by or similar to that expected from the full‐scale process. Assuming two treatment trains, flows required would be on the order of a maximum of 150 gallons per day.

4. Continue periodic monitoring of the existing wetlands within the regional stream network to confirm selenium removal capacity.

2

5. Collect water quality data from existing and proposed water sources for the RO system to improve understanding of the nitrate, sulfate and selenium concentrations likely to be found in the RO concentrate.

Introduction Project Background Cottonwood Water and Sanitation District (CWSD) is one of two districts that provides water and wastewater service to portions of Parker, Colorado. CWSD worked jointly with the Arapahoe County Water and Wastewater Authority (ACWWA) to fund the Joint Water Purification Plant (JWPP), a reverse‐osmosis (RO) water treatment facility that treats water from the Cherry Creek alluvial aquifer to meet current and anticipated Safe Drinking Water Act requirements. During operation in 2010, the reject water created during the RO process exceeded the selenium levels allowable in their Colorado Discharge Permit System (CDPS) permit. The Colorado Department of Public Health and Environment (CDPHE) issued a Notice of Violation related to selenium concentrations in the brine stream exceeding the discharge permit limit of 4.6 µg/L. Following the Notice of Violation, the JWPP ceased operation of the RO system and the plant was modified to produce potable water entirely though the plant’s microfiltration system. Since the modification, the JWPP has only delivered potable water to ACWWA and no longer discharges treated concentrate to Windmill Creek.

To resume operation of the RO units, the concentrate will require treatment to meet discharge requirements. Exact discharge criteria will be defined through a potential discharge permit amendment application using ambient stream standards recently adopted by the Water Quality Control Commission. At this point, it is assumed that the discharge will be required to meet a criteria of 4.6 µg/L for selenium. CWSD requested that CH2M assess the feasibility of passive biological treatment technologies for the removal of selenium from the JWPP discharge.

Passive biological treatment systems utilized for selenium treatment include open aquatic systems such as ponds and constructed wetlands, and biochemical reactors, which include enclosed beds of engineered soil, gravel or organic media to create anaerobic environments for microbial treatment (CH2MHILL 2012). Passive treatment systems require less energy and operational effort to maintain than conventional mechanical or chemical treatment systems, but may require extensive areas of land to support the level of treatment necessary to meet discharge criteria.

In an effort to review all potential passive treatment options for the JWPP concentrate treatment, the conceptual performance of wetlands and biochemical reactors were evaluated in this feasibility study.

Purpose and Objectives The study purpose is to identify potential biological treatment alternatives for treating the JWPP RO concentrate stream to reduce selenium and allow the RO units to resume operation. This technical memorandum presents three conceptual alternatives for treating RO concentrate from the JWPP:

1. Alternative 1: Selenium Biochemical Reactor Treatment 2. Alternative 2: Constructed Wetland Treatment 3. Alternative 3: Selenium Biochemical Reactor and Wetland Treatment

These alternatives would apply passive treatment technologies to meet required levels in the discharge permit, thereby allowing the JWPP to restart the RO unit operations to meet increasing water demands.

Location The JWPP is located on land owned by both Cottonwood and ACWWA, south of Jordan Road along the east side of Happy Canyon Creek in Parker, Colorado at an elevation of approximately 5,700 ft. The proposed project location for a conceptual treatment system is adjacent to the JWPP, just west of Happy Canyon Creek, on six undeveloped acres with good access for a tie‐in connection to the existing underground concentrate discharge pipe. The project location is shown on the JWPP Site Map in Appendix A.

On average, Parker receives approximately 17 inches of rain and 54 inches of snow on an annual basis (US Climate Data Center, 2015). The mean annual temperature is approximately 50°F with temperatures averaging 85°F in the summer and 15‐20°F in the winter.

Outline This memorandum is organized to provide initial overviews of the project and the potential use of natural treatment systems for concentrate water quality improvement, followed by a description of the alternatives and anticipated treatment performance, costs and benefits, and a final set of recommendations.

Natural Treatment System Technology Natural treatment systems are constructed or modified ecosystems that use natural biological, physical and chemical processes to improve water quality. They encompass the general category of engineered wetlands, both constructed and natural, but also include biochemical reactors that may operate passively, or may be intensified through the addition of commercial carbon and nutrient feeds to enhance biological treatment. Both active and passive biological treatment technologies have been shown to provide effective treatment of concentration ranges of selenium (CH2M HILL, 2010).

Typically more land‐intensive than active treatment systems, passive biological systems can be less expensive to operate and manage because of lower or negligible energy or chemical inputs (Ziemkiewicz et al., 2003). In passive treatment systems designed to treat selenium, a naturally occurring element with significant ecotoxicological properties, oxidized forms of the element (i.e., selenite, selenate) can be reduced to selenite, elemental selenium, and selenides through microbial reduction, followed by sequestration in soil and sediments (Gusek et al. 2009). Labile organic carbon released from the substrate serves as an electron donor (i.e., an energy source for the microbes providing the treatment). Common electron acceptors (e.g., dissolved oxygen (DO) and nitrate) are removed first or concurrently.

Engineered wetlands designed for selenium removal have spanned the size range of pilot systems on the order of 100 feet square or less, up to full‐scale marshes covering 90 acres or more (CH2M HILL, 2012). In these systems, water moves slowly through a vegetated shallow marsh, coming in contact with decomposing vegetation and anaerobic (low oxygen) sediments. Studies of wetlands treating selenium have indicated that the oxidized forms (i.e., selenate, selenite) are rarely found in wetland sediment. Instead, selenide, elemental selenium and organic selenium are more typically found, indicating that selenium has been transformed biologically. Because constructed wetlands attract birds, and selenium intake through food chain bioaccumulation can lead to physical abnormalities, the use of open water wetlands for selenium treatment is often limited to treat concentrations in the range of 15 µg/L or less.

As an alternative to surface water bodies for treatment of selenium, subsurface flow wetlands have been shown to provide effective selenium reduction in RO concentrate (Bays et al. 2007; Chakraborti et al. 2015). In these systems, water flows below the surface of an engineered media bed of gravel, sand, or soil, through a dense zone of wetland plant roots. This approach offers a method of biological selenium reduction without the concern of ecological uptake or exposure to wildlife.

More commonly, passive treatment systems designed for selenium reduction consist of a vertical or horizontal subsurface flow of water through a reducing organic substrate. This achieves microbial and chemical reduction of selenium naturally, with shorter hydraulic residence times and smaller areas than constructed wetlands. Termed biochemical reactors (BCRs), these passive systems have been employed previously for treatment of a variety of mine‐impacted waters (e.g., ITRC, 2008) and in a variety of forms. The organic substrate utilized has been composed of wood chips, saw dust, mushroom compost, horse manure, field hay, yard wastes, and limestone granules in varying proportions.

The geochemistry of BCRs relies on a staged approach for trace metal removal. Sulfate‐reducing BCRs precipitate trace metals with biogenic sulfide (i.e., natural chemical reduction of selenate to elemental selenium), while selenate‐reducing BCRs remove selenium as elemental precipitates (CH2M HILL, 2010). Because selenium compounds are more readily reduced than sulfur compounds and reduced sulfur compounds can act as a

4

chemical reductant, any sulfides precipitated in the BCR (e.g., acid volatile sulfides) provide additional reducing capacity within the substrate. As additional selenium‐bearing water passes through this substrate, there is not only the benefit of biological reduction, but also the potential for chemical reduction.

Other removal processes occurring in passive treatment systems include volatilization and adsorption. Volatilization of selenium through bacterial, fungal, or algal‐mediated methylation of selenium has been shown to be a significant loss of selenium in wetlands through the conversion to organic forms such as dimethyl selenide (Hanson et al., 1998; Lin et al., 2003). Physical adsorption of selenate to iron, aluminum, or manganese oxy‐hydroxides present within soil or sediments and to organic matter, readily occurs in passive treatment systems (Kadlec and Wallace, 2009).

Because the BCR is comprised of organic media, secondary parameters (e.g., biochemical oxygen demand [BOD], color, sulfide, and reduced nitrogen) are generated that require treatment before discharge. Across different projects, post‐BCR treatment has varied widely, including aerated and non‐aerated ponds, surface flow constructed wetlands, and subsurface flow gravel beds, singly or in combinations. Frequently described as aerobic polishing cells, these treatment units function by trapping particulate organic particles, increasing the DO content of the BCR effluent, as well as oxidizing chemical oxygen demand (COD) or BOD present.

Recent advances in passive biological treatment of selenium have come through the implementation by mining companies and the US Bureau of Reclamation (Reclamation) of treatability pilot studies, full‐scale systems, and additional projects discovered through professional contacts and continued review of the literature (Bays et al. 2012). Pilot studies have indicated consistently that total selenium can be reduced to 20, and

>45 µg/L to

6

In a passive selenium treatment system, nitrate is an alternate electron acceptor that must be reduced to allow optimum reduction of selenium. The higher the nitrate value the greater the area that will be required for effective selenium reduction. Because expected nitrate values in the concentrate were not available, CH2M estimated an assumed value of 9 mg/L, based on the ratio of total dissolved solids (TDS) in source wells to RO concentrate.

These various source well and recovery options, along with the associated selenium, nitrate and TDS feed concentrations, form the basis of analysis for this passive treatment study.

Treatment Performance Modeling The technical approach to sizing passive treatment systems has progressed steadily over the past twenty years since the publication of the first edition of Treatment Wetlands (Kadlec and Knight 1996), a milestone in the evolution of the technology. The use of first‐order removal rates is now commonly accepted for the sizing of passive treatment systems (Kadlec and Wallace, 2009). Removal rate constants are calibrated from data sets from existing wetlands and related systems, such as biochemical reactors. Values generally are found to be distributed around a central tendency. These average values are used to predict performance under different flow and concentrations.

The first‐order model of Kadlec and Wallace, known as the “PkC*” model, was applied using rate constants based on CH2M experience with treatment systems with similar ranges of selenium concentrations. The following general form and specific values selected from the design basis:

Where

C = outlet concentration, mg/L. For this treatment system, the selected value for selenium is 0.0046 mg/L.

Ci = inlet concentration, mg/L. The inlet concentration for this analysis varies depending on the well source and RO recovery. Inlet concentrations were provided in Table 2.

C* = background concentration, mg/L. This represents a biogeochemical background or equilibrium value for local surface waters. Based upon available literature and project experience, a value of 0.001 mg/L was selected for selenium.

P = weathering parameter, a derived factor that describes the hydraulic performance of a system as multiple tanks‐in‐series (TIS) with a distribution of hydraulic residence times, based upon published tracer test results, and as mixtures of compounds, based upon the understanding that there is a distribution of removal rates based upon the form of a parameter compound (e.g., selenium can occur as oxidized anions such as selenate or selenite and reduced compounds such as selenide). The greater the P value, the greater areal efficiency of treatment can be presumed. Constructed surface water wetlands have an average of 4.1 TIS, while subsurface flow wetlands average 11 TIS (Kadlec and Wallace 2009). For conservatism, a value of 3 was selected for surface flow wetlands and 6 for the vertical flow BCR.

q = hydraulic loading, m/yr. This value varies for each alternative for this project and is detailed in the performance section of this technical memorandum.

k = rate constant, m/yr. Values are derived from recent CH2M experience, and published information where available. Details on each value selection are provided below.

Temperature effects on k can be taken into account based on the following:

P

i Pqk

CCCC

1

**

)20(20

tt kk

Where

θ = temperature adjustment factor. For nitrate‐nitrogen, θ = 1.11 (Kadlec and Wallace 2009). For selenium, no consistent significant temperature effect has been reported in the passive treatment literature, therefore a θ = 1 was assumed.

Alternative 1 Performance Modeling For Alternative 1, the biochemical reactor area was modeled as three conceptual tanks‐in‐series. CH2M experience indicates that nitrates are required to be reduced to approximately 1.5 mg/L to achieve optimum selenium reduction. The first cell modeled is expected to reduce nitrates to this range and must be sized to achieve this objective. Based on CH2M experience, corroborated by literature values derived from studies of agricultural denitrifying BCRs, the selected first‐order, area‐based rate constant (k) for nitrates is estimated to be 1,876 m/year for a 1.5 m deep BCR.

Selenium removal needs to be modeled as a process of sequential treatment, particularly in presence of high nitrate concentrations. Using information available from previous CH2M pilot studies, a rate constant for selenium of 62 m/year was selected for BCR treatment in the presence of high nitrate concentrations. A greater removal rate of 675 m/year is associated with selenium concentrations where presence of high nitrate concentrations have already been removed. As a conservative measure, 139 m/year was also used for selenium treatment in the vertical upflow bed to further polish down to a concentration of 4.0 µg/L. All values selected are for BCR media depths of 1.5 meters.

Alternative 2 Performance Modeling Two scenarios were modeled for Alternative 2, which utilizes only constructed wetlands for biological treatment. Scenario 1 estimates the expected selenium concentration utilizing the adjacent 6‐acre parcel for a constructed wetland. Scenario 2 determines the total wetland area required to meet a selenium criterion of 4.5 µg/L.

The wetland was modeled as three cells per basin in series resulting in a weathering pattern value (P) of 9. The first‐order model was applied using removal rates calibrated from similar wetlands. Similar to the biochemical reactor criteria, the constructed wetlands also require sequential modeling for the presence of high nitrate concentrations. A nominal rate of 12 m/year was used in the presence of high nitrate, based upon information on selenium treatment wetland performance summarized in Kadlec and Wallace (2009). A greater rate of 19 m/year was used for low nitrate concentrations. In this case, the value of 19 m/year was derived from a preliminary analysis of selenium concentration reduction in the constructed wetland basin in Lone Tree Creek.

Alternative 3 Performance Modeling Two layout scenarios were modeled for this alternative. Scenario 1 determined the final selenium concentration that can be achieved using a 1.27‐acre BCR and the remaining 4.73 acres of available land for a combined biochemical reactor and wetland system. Scenario 2 determined the total BCR and wetland area required to meet a selenium criterion of 4.5 µg/L.

For this alternative, the BCR/wetland combination was modeled using identical rate constants and criteria as those identified in Alternatives 1 and 2.

8

Configuration Alternative 1: Biochemical Reactors The proposed process flow for Alternative 1 is presented in Figure 1 below. The biochemical reactor (BCR) system is proposed as a system of three vertical downflow (VDF) cells, three vertical upflow (VUF) cells and 2 aerobic polishing cells (APC). Flow would be designed to flow by gravity from a tee connected to the existing 12 inch PVC pressurized concentrate line and drained into the first collection vault. From the first collection vault, flow would continue to flow by gravity from the VFD reactors to the VUF reactors and drain into the second collection vault. Flow will continue to flow by gravity from this vault to the polishing basins until it reaches the pump station vault where the treated water is collected and pumped back into the concentrate line for final discharge. A conceptual layout configuration of this alternative is provided in Appendix B.

Figure 1

Alternative 1 Selenium Biochemical Reactor Process Flow Diagram

The VDF cells will operate in parallel as vertical downflow BCRs. The redundancy of three cells provides operational flexibility for future operation and maintenance of the cells. The makeup of each cell will include a bed of organic substrate and lined with high density polyethylene (HDPE). The proposed media consists of 20 percent woodchips, 35 percent sawdust, 10 percent peat moss, 5 percent limestone sand, 25 percent hay, and 5 percent composted manure. Due to the cold environment that this system will be exposed to, an insulated layer will be placed on top of BCR 1A and 1B. The primary function of the VDF cell is to remove all of the nitrate and most of selenium entering the system. This process occurs as water percolates down through the media and gravel beds and into a collection network of louvered plastic inlets, termed Infiltrators, located at the bottom of the cell. Water will be collected in an outlet pipe and routed to the VUF cells.

The VUF cells are BCRs constructed similarly to the VFD cells, but with a media of peat, instead of organic compost. These cells are intended to provide additional treatment of selenium in the outflow water from the VDF cells through particle filtration, adsorption and anaerobic biological reduction fostered by the discharge and capture of the VDF cell byproducts, including sulfide and excess organic carbon.

The APC cells are designed to polish the reduced byproducts of the treatment processes in the VDF and VUF cells. This includes biochemical oxygen demand (BOD) released by the upstream anaerobic cells.

Table 3– Alternative 1 Biochemical Reactor Configuration

Cell Wetland Type Media Treatment Function

N VDF Downflow biochemical reactor Mixed organic Nitrate and selenium reduction

VUF Upflow biochemical reactor Peat Selenium reduction

Particulate filtering, residual sulfide polishing

APC 1 Pulsed vertical downflow Gravel underdrain and sand and gravel layers BOD reduction, sulfide oxidation

Siphon 1 NA NA Siphon reservoir; Passive pulse flow to media bed

APC 2 Pulsed vertical downflow Gravel underdrain and sand and gravel layers BOD reduction, sulfide oxidation

Siphon 2 NA NA Siphon reservoir; Passive pulse flow to media bed

Alternative 2: Constructed Wetlands The proposed process flow for Alternative 2 is proposed as a system consisting of three wetland basins (Figure 2). Inlet water would be designed to flow by gravity from a tee connected to the existing 12 inch PVC pressurized concentrate line and drain into the first collection vault. From the first collection vault, flow would continue to drain by gravity from the first wetland basin to the next through with collection boxes between each basin, until reaching the final pump station vault. From here, treated water would be collected and pumped back into the concentrate line for final discharge.

Although the constructed basins are considered to be wetlands, the depth varies in each depending upon the percentage of shallow marsh and relatively deeper open water. Open zones within a wetland create an open environment that allows water to mix passively through wind action, oxygenation to occur through aquatic photosynthesis, and for precipitates to settle and be sequestered in sediments. Vegetated areas accumulate detrital material which creates zones for trapping and settling of particulates, and for passive redistribution of flow.

The constructed wetlands would be lined with high density polyethylene (HDPE) geomembrane to prevent leakage of water through the berms and bottom and to maintain separation of residuals within the passive treatment systems. A conceptual layout configuration was not developed for this alternative due to land requirements in excess of what was anticipated to be available in order to fully meet the anticipated selenium removal requirements.

10

Figure 2

Alternative 2 Constructed Wetland Process Flow Diagram

Alternative 3: Biochemical Reactor and Constructed Wetland For Alternative 3, flow would be conveyed by gravity from a tee connected to the existing 12 inch PVC pressurized concentrate line and drain into the first collection vault (Figure 3). Inlet water would be designed to flow by gravity from a tee connected to the existing 12 inch PVC pressurized concentrate line and drain into the a collection vault. From the collection vault, flow would continue to drain by gravity from the VFD reactors to the VUF reactors and drain into the second collection vault. Flow will continue to drain by gravity into a series of wetland ponds for further treatment. Treated water would drain into the final pump station vault where it would be collected and pumped back into the concentrate line for final discharge.

A conceptual layout configuration of this alternative is provided in Appendix C.

Figure 3

Alternative 3 Selenium Biochemical Reactor and Constructed Wetland Process Flow Diagram

Performance The treatment performance model was used to assess the feasibility of achieving the selenium criterion for each of the three alternatives and two source well options. Detailed performance data for each alternative, scenario and source well option are provided in Appendix D. Table 4 identifies each scenario by listing the method of treatment (i.e., Alternatives 1, 2 and 3); the source well location (i.e., current or relocated), RO recovery percentage (i.e., 65, 75 or 83%); the sizing objective (i.e., the target selenium criterion of 4.6 µg/L or what can be treated within the assumed area available); the treatment area required to meet the objective; and the relative selenium performance as a percentage of the target criterion (e.g., 100% achieves 4.6 µg/L; 20% achieves 23 µg/L; 115% achieves 2.1 µg/L).

From this detailed comparison of treatment performance, and based upon the results of a review workshop conducted October 1 2015, CWSD considers the most likely project water source going forward is the 83% RO recovery from treatment of water from the current wells. To standardize and simplify comparisons between the various alternatives presented below, the assumed water source is limited to the 83% RO recovery flow rate of 0.95 mgd of water from the current wells.

12

Table 4 – Summary of Selenium Reduction Performance

Scenario Item No.

Treatment Alternative

Source Well Location

JWPP RO Recovery

(%) Sizing Scenario Total Treatment Area (acres)

% of Se Target

Achieved

1 Alternative 1 Current 65% Target Se 6.9 114%



4 Alternative 1 Relocated 65% Target Se 5.8 116%



7 Alternative 2 Current 65% Available Area 6.0 20%






13 Alternative 2 Relocated 65% Available Area 6.0 48%
















29 Alternative 3 Relocated 83% Available Area 6.0 43$


Alternative 1: Selenium Biochemical Reactor Performance by the Alternative 1 BCR treatment system is detailed in Table 5 for the removal of selenium, nitrate‐nitrogen and BOD for each component. The system is projected to reduce selenium by 76% from 17.1 µg/L to an outflow concentration of 4.0 µg/L, which is below the 4.6 µg/L selenium target. The proposed system would require 1.96 acres of vertical downflow (VDF) BCR, 0.42 acres of vertical upflow (VUF) peat wetland, and 1.31 acres of subsurface flow aerobic polishing cell (APC). The hydraulic loading rate (flow divided by area) for the combined BCR cells (VDF+VUF) would be 37 cm/d and for the combined APC cells would be 68 cm/d. The hydraulic residence time would be 2.8 days for the combined BCR cells and 0.8 days for the combined APC cells.

The areas for the BCR cells and the APC cells are within the range of experience. For example, individual BCR cells implemented in West Virginia for selenium treatment in coal mine drainages range from

14

become a detriment, given the likelihood that wildlife using the wetland may require monitoring for toxicological effects. The system would have a greater construction cost, but a lower unit cost.

Table 6 – 6‐Acre Constructed Wetland Performance Current Well Option ‐ 83% RO Recovery, 0.95 MGD

Wetland Basin Se in (mg/L) Se out (mg/L)

Se k (m/yr)

NO2/3‐N in (mg/L)

NO2/3‐N out (mg/L)

NO2/3‐N k (m/yr)

HLR (cm/d)

HRT(d)

Area (acre)

Wetland 0.0415 0.0335 12 9.00 4.04 44.70 14.8 4.4 6.00

Table 7 – Calculated Constructed Wetland Performance Current Well Option ‐ 83% RO Recovery, 0.95 MGD

Wetland Se in (mg/L) Se out (mg/L)

Se k (m/yr)

NO2/3‐N in (mg/L)

NO2/3‐N out (mg/L)

NO2/3‐N k (m/yr)

HLR (cm/d)

HRT(d)

Area (acre)

Nitrate Removal Basins

0.0415 0.0257 12 9.00 1.50 44.70 6.5 10.1 13.73

Selenium Removal Basins

0.0257 0.0046 19 1.50 ‐0.13 44.70 2.4 27.1 36.64

Total Constructed Wetland HRT and Area: 37.2 50.37

Alternative 3: Biochemical Reactor and Constructed Wetland Performance by the Alternative 3 treatment system is summarized in Tables 8 and 9. Similar to Alternative 2, the area was constrained to the six acres assumed to be available for the first scenario (Table 8) and expanded to the full area necessary to achieve the selenium target in the second (Table 9). For the available area, the system is projected to reduce selenium by 37% from 17.1 µg/L to an outflow concentration of 10.8 µg/L, which is greater than the 4.6 µg/L selenium target. The proposed system in the first scenario would include 1.27 acres of vertical downflow (VDF) BCR for nitrate reduction followed by 4.73 acres of surface flow wetland for selenium reduction.

In the full‐size scenario, a 1.27‐acre BCR component would reduce nitrate to 1.5 mg/L, and a 27‐acre surface flow wetland would reduce the final concentration to the target selenium criterion. Alternative 3 would have a smaller area requirement than Alternative 2 but would still be impracticably large given the land area limitations in the project vicinity. The BCR outflow concentrations in the 6‐acre scenario would be reduced from 100 mg/L to 69 mg/L, a significant improvement but a concentration too high for local stream discharge. For the full‐size system, outflow BOD is estimated to be within 33 mg/L, a concentration possibly suitable for discharge.

While Alternative 3 would result in lower cost than Alternative 1, and would require relatively little maintenance, Alternative 3 would not meet the water quality criterion within the available 6‐acre project footprint. The wetland would be large enough to treat the byproducts exported from the BCR. Concern over exposure to wildlife would be lessened, given the lower inlet concentrations to the marsh, but this Alternative would still requirement management of odor causing potential.

Table 8: Alternative 3 Selenium Reduction Performance – 6 acre area Current Well Option ‐ 83% RO Recovery, 0.95 MGD

Treatment Basin

Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO3 in (mg/L)

NO3 out (mg/L)

NO3 k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

BOD k (m/yr)

HLR (cm/d)

HRT (d)

Area (acres

)

VDF 0.0415 0.0330 62 9.00 1.50 1876 N/A N/A N/A 69.8 1.5 1.27

Wetland 0.0330 0.0256 19 1.50 0.80 44.70 100.00 69.01 36 18.8 3.5 4.73


Table 9: Alternative 3 Selenium Reduction Performance – Calculated area Current Well Option ‐ 65% RO Recovery, 1.95 MGD

Treatment Basin

Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO3 in (mg/L)

NO3 out (mg/L)

NO3 k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

BOD k (m/yr)

HLR (cm/d)

HRT (d)

Area (acres

)

VDF 0.0415 0.0330 62 9.00 1.50 1876 N/A N/A N/A 69.8 1.5 1.27

Wetland 0.0330 0.0046 19 1.50 ‐0.08 44.70 100.00 22.68 36 1.6 40.6 54.92


Conceptual Cost Estimate A cost estimate was prepared for each alternative for the 83% recovery, 0.95 MGD, current source well scenario. Capital costs and non‐construction costs (i.e., engineering, services during construction, commissioning and startup, legal) are summarized for each alternative in Table 10.

The cost estimates for each alternative include the following assumptions:

Access roads to service the new treatment system (3.4% of construction costs)

Commissioning and startup (2%)

Plant computer system

Major rock excavation or blasting is not included in this estimate. The 2008 geotechnical recommendations from Ground Engineering Consultants reported some claystone bedrock in two out of three test pits at depths greater than 5 ft. These two test pits are not located in the project location.

Boardwalks for other site improvements are not included in this estimate

New outfall is not required and therefore not included in this estimate.

Permitting is not included in this estimate

16

Table 10 Conceptual Costs Estimate for Proposed Systems

Treatment Alternative Total Capital Cost Operating Cost

Alternative 1: BCR $3,789,000 $115,000

Alternative 2: Wetland (50‐ac) $9,540,000

Operational costs are comparatively low for passive treatment systems such as engineered wetlands and biochemical reactors, compared to conventional treatment systems. Costs may typically include labor for observation, monitoring, and general system maintenance. Non‐labor costs may include power for pump operation and operation of monitoring equipment. Chemical costs and the collection, transport and disposal of treatment residuals are not typically incurred. The JWPP alternatives include wetland and BCR maintenance, and therefore span the full range of passive treatment system maintenance activities.

Table 12 summarizes a projection of potential labor and non‐labor operating costs for Alternative 1. Labor is anticipated to include routine inspection, sample collection, data review and monitoring, seasonal berm mowing and maintenance, and periodic outreach in the form of community or technical tours or similar activity. Non‐labor costs are assumed to include routine pump station maintenance and upkeep, power costs, and laboratory analysis for weekly samples. Assuming a 10% contingency, the annual maintenance cost is on the order of $115,000, in 2015 dollars. When annualized over a 20‐year period, assuming a 2.0% interest rate, the Net Present Value for this operation and maintenance cost is estimated to be on the order of $95,000 per year. This general cost would be expected to apply to Alternatives 1 and 3, based on the assumption of constructing a multi‐cell system within the 6‐acre available area. Alternative 2 may be expected to be less expensive to operate and monitor, given the relatively fewer number of cells.

Table 12. Conceptual Annual Operation and Maintenance Costs for Alternative 1 Category Activity Cost Notes

Labor Routine Inspection $ 20,000 2 hrs/day, 3 days/week hydraulic and grounds inspection @ $65/hr

Sample Collection $ 27,000 8 hrs/week @ $65/hr

Data Review and Reporting $ 6,000 8 hrs/month @ $65/hr

Berm Maintenance $ 3,000 48 hrs @$65/hr

Outreach $ 3,000 48 hrs @$65/hr

Labor Subtotal $ 59,000 ~ 0.5 full‐time equivalent

Non‐Labor Pump Station Maintenance $ 2,000 2.5% pump station cost (assume $75,000 capital cost)

Power $ 16,000 $0.10 per KW‐hr (assume 1 KW/1.341 hp for 20 hp)

Laboratory $ 28,000 5 samples (e.g., I, BCR vault, VUF, APC1, APC2 vault); 3x/mo x 12 mo

Non‐Labor Subtotal $ 46,000

Subtotal $105,000

Reserve Contingency $ 10,500 10%

Total $115,000

Periodic media replacement will be required for maintenance in Alternatives 1 and 2. Two types of media replacement are projected: organic compost media used as the basis for the BCR construction and operation, and engineered phosphorus treatment media used to meet discharge standards in the system outflow. Conventional understanding of the lifespan of an organic BCR media bed is 20 years. Replacing the media beds would consist of a sequential process of removing the soil and organic cover cap, removing the distribution piping, removing and replacing the spent media with fresh material, replacing the distribution system and cover, and restoring the site to design grade and appearance. This operation is obviously a significant effort, and would require planning and preparation. A preliminary estimate to perform this operation is $530,000, which includes a 30% contingency and the cost of transporting spent media to an approved hazardous waste landfill. Assuming a 2% interest rate, the

18

annualized Net Present Value of this cost over a 20‐year period is estimated to be approximately $22,000 per year.

The media‐based approach to phosphorus control assumes the use of a Water Treatment Residual (WTR) for the purpose of this analysis. The use of WTRs for phosphorus control in wastewater and stormwater is an increasingly accepted application, and provides both protection of downstream waters through reduction in phosphorus released from BCR media leaching and decomposition (e.g. Elliot et al. 2002; Yang et al., 2009; Lee et al. 2015). Preliminary estimates indicate that approximately 3,600 kg of WTR would be required annually to capture excess phosphorus in the effluent from the BCR system. This would be expected to reduce an assumed BCR outflow concentration of 0.8 mg/L to an outlet phosphorus concentration of 0.2 mg/L. Assuming an average cost of $50 per ton for WTR, $50 per ton for landfill disposal, and an annual production of about 44 tons of WTR/sand media at a volume ratio of 1:10, an annual cost for P media would be on the order of $4,000. Actual costs may vary. Handling of the media (i.e., installation and replacement) would be expected to be a relatively brief operation (less than a week). The media bed could be constructed as a flow‐through bed within specially prepared roll‐off containers, designed to be readily replaced and moved by truck, or a similar modular approach.

Discussion The use of passive biological treatment for treatment of selenium has progressed in recent years to where it is now possible to forecast performance and establish preliminary estimates of cost and maintenance. From the analysis presented in this memorandum, CH2M concludes that selenium in the JWPP concentrate could be reduced to concentrations that meet state water quality criteria using a passive biological treatment system. Alternative 1 offers the best potential to achieve this objective within the constraints of available land area and for a reasonable capital and operating cost.

Additional concerns can be anticipated about the suitability for this type of treatment system within a growing community. Given the proximity to neighborhoods, the BCR system described in Alternative 1 would need to be a “good neighbor” and all potential for odor control addressed. The infrequent media maintenance would be designed and publicized as a short‐term refurbishment, likely to be performed during an appropriate time of year and with an adaptive plan to manage odors during transfer. Odor control during refurbishment could be accomplished using masking agents or oxidizing foams, similar to what is currently implemented during sediment and biosolids handling and drying processes. The refurbishment would be a relatively short process, estimated to be performed within a week period. Each BCR could be managed to be completed during different years. Sulfide concentration distribution could be modeled during site and operational planning to confirm the potential for odor concerns and construction and management plans developed to prevent exceedance of odor thresholds at specific site locations. Consideration could be given to the benefit of installing hydrogen sulfide meters along the site perimeter and other locations, as warranted.

Landscaping of the site could be performed such that all basins are capped with an earthen cover and contoured and planted by design to mimic a rolling prairie. Operation of the site would be quiet; the only mechanized features would be the concentrate return pump station, which would be constructed in subsurface vaults. Educational signage or materials could be prepared that would serve to inform the local community confirming the intent and safety of the BCR system.

Additional information could be collected that would help support the implementation of a biological treatment system. As an initial step, a discussion should be held with CDPHE representatives to develop an appropriate regulatory approach and the likely acceptance of the proposed approach by regulatory agencies.

Second, the availability of the full six acres assumed for this analysis should be confirmed, and steps taken toward purchasing the land.

Third, information could be gathered on the natural selenium assimilation capacity of existing wetlands within the local watershed. Wetlands such as that established on Lone Tree Creek could be further monitored to support model calibration and establish an assimilation capacity of the regional stream network.

A fourth step would be the implementation of a short‐term, small‐scale pilot study to demonstrate the ability of a BCR approach such as that described in the report to achieve water quality criteria while confirming removal rates and sizing criteria employed in this report. This study would also allow demonstration of odor control design techniques as well as phosphorus media treatment approaches.

Finally, additional information should be collected that would be used to refine or confirm the assumptions employed in this report, including the concentrations of nitrate‐nitrogen, selenium, sulfate, and phosphorus in the source waters, as they become available. This would enable final determinations of concentrations that could be expected under future operations, and allow a final sizing analysis to be performed.

Recommendations Based upon the results of this feasible study, CH2M recommends that the following activities and steps be implemented to further the biological treatment system project.

1. Meet with CDPHE to review regulatory status and confirm data needs and regulatory constraints.

2. Determine the feasibility of procuring the six‐acre parcel.

3. Plan and implement a pilot investigation of the proposed BCR system configuration. Conduct the pilot at the JWPP site using concentrate generated by or similar to that expected from the full‐scale process.

4. Continue periodic monitoring of the existing wetlands within the regional stream network to confirm selenium removal capacity.

5. Collect water quality data from existing and proposed water sources for the RO system to improve understanding of the nitrate, sulfate and selenium concentrations likely to be found in the RO concentrate.

20

References Bays, J., P. Frank and K. Ortega. 2007. Oxnard's Membrane Concentrate Pilot Wetlands Project. In Proc. Water Reuse Association, Tampa FL.

Bays, J., J. Tudini, R. Thomas, D. Evans and T. Harrison. 2013. Advances in the Use of Passive Wetland Systems for Selenium Treatment of Mine‐impacted Water. Proc. 2013 Annual Meeting of the Society of Mining, Minerals and Exploration.

Chakraborti, R., J. Bays, T. Ng, L. Balderrama, and T. Kirsch. 2015. A pilot study of a subsurface‐flow constructed wetland treating membrane concentrate produced from reclaimed water. Water Sci. Technol. 72.2:260‐268.

CH2M HILL. 2010. Review of Available Technologies for the Removal of Selenium from Water. Prepared for the North American Metal Council. www.namc.org/docs/00062756.PDF (Accessed October 27 2015).

CH2M HILL. 2012. Regulating Wetlands Pilot Study for Concentrate Management. Bureau of Reclamation Science and Technology Program Report No. 3699. http://www.usbr.gov/research/ science‐and‐tech/projects. (Accessed 10/27/2015).

Elliott, H.A., G.A. O’Connor, P. Lu, and S. Brinton. 2002. Influence of water treatment residuals on phosphorus solubility and leaching. J. Environ. Qual. 31:1362–1369. doi:10.2134/jeq2002.1362

Gusek, J., K. Conroy, and T.Rutkowskie. 2009. Past, Present and Future for Treating Selenium‐Impacted Water. Tailings and Mine Waste ’08. Proc. 12th International Conference. CRC/Balkema Press Inc., London, UK. Pp.281‐290.

Hansen, D., P.J. Duda, A. Zayed, and N. Terry. 1998. Selenium Removal by Constructed Wetlands: Role of Biological Volatilization. Environ. Sci. Technol., 32: 591‐597.

Irvine Ranch Water District. 2015. San Joaquin Marsh. Hidden Gem, Natural Wonder. http://www.irwd.com/san‐joaquin‐marsh/san‐joaquin‐marsh (Accessed October 27 2015).

Interstate Technical Regulatory Council (ITRC). 2010. Biochemical Reactors. http://www.itrcweb.org/miningwaste‐guidance/to_bioreactors.htm (Accessed October 27 2015).

Kadlec, R. and R. Knight. 1996. Treatment Wetlands. CRC Press, Boca Raton, FL.

Kadlec, R.H. and S. Wallace. 2009. Treatment Wetlands, 2nd Ed. CRC Press, Boca Raton, FL.

Kepke, J., Bays, J. and J. Lozier. 2009. Concentrate treatment using wetlands. Water (J. Australian Water Association) 36 (7), 57–63. Lee, Y.L., B. Wang, H. Guo, J. Yong Hu, and S. L. Ong. 2015. Aluminum‐Based Water Treatment Residue Reuse for Phosphorus Removal. Water 7: 1480‐1496. Lin, Z. and N. Terry. 2003. Selenium removal by constructed wetlands: Quantitative importance of biological volatilization in the treatment of selenium‐laden agricultural drainage water. Environ. Sci. Technol. 37, 606–615. Meek, A., K. O’Dell, B. Faulkner. 2012. Arch‐Eastern Birch Mine. Presented to West Virginia Mine Drainage Task Force Symposium. March 27 2012. http://wvmdtaskforce.com/proceedings/12/4A‐Meek‐2012‐PPT_3‐28.pdf SELENIUM TREATMENT United States Climate Data. 2015. Monthly Precipitation and Temperature Data. www.usclimatedata.com

Yang, Y., Y.Q.Zhao, A.O. Babatunde, and P. Kearney. 2009. Two strategies for phosphorus removal from reject water of municipal wastewater treatment plant using alum sludge. Water Science and Technology, 60 (12): 3181‐3188.

Ziemkiewicz, P.F., J.G. Skousen, and J. Simmons. 2003. Long‐term performance of passive acid mine drainage treatment systems. Mine Water Environ., 22:118‐129.

Acronyms and Abbreviations: ACWWA: Arapahoe County Water and Wastewater Authority

cfs: cubic feet per second

μg/g: microgram per gram

μg/L: microgram per liter (equivalent to parts per billion, or ppb)

BMP: best management practice

CDPS: Colorado Discharge Permit System (CDPS)

CWSD: Cottonwood Water and Sanitation District

gpm: gallons per minute

gpd: gallons per day

GW: groundwater

GWTF: Groundwater Treatment Facility

IRWD: Irvine Ranch Water District

JWPP: Joint Water Purification Plant

LA: load allocation

lbs/day: pounds per day

lbs/yr: pounds per year

mg/kg: milligram per kilogram

mg/L: milligram per liter (equivalent 2 parts per million, or ppm)

NO3: nitrateNSMP : Nitrogen‐Selenium Management Program

NPDES: National Pollutant Discharge Elimination System

pH: potential of hydrogen ( measurement of acidity of a water sample)

psi: pounds per square inch

Se: selenium

Se (IV): selenite

Se (VI): selenate

SSF: subsurface flow

TDS: total dissolved solids

TIN: total inorganic nitrogen (ammonia + nitrite + nitrate)

TMDL: total maximum daily load

TSS: total suspended solids

USEPA: United States Environmental Protection Agency

WLA: wasteload allocation

WWTP: Wastewater Treatment Plant

22

Appendix A

JWPP Site Map

FIGURE XSite MapJoint Water Purification PlantArapahoe County, Colorado

I:\665063_COTTONWOOD_WATER_SANITIATION_DISTRICT\GIS\MAPFILES\SITE_MAP.MXD JQUAN 9/14/2015 9:23:48 AM

VICINITY MAP

S Jordan Rd

S Kalispell Way

E Nichols

Ave

E Nichols

Pl

WELL

WELL

CPIPE CONCENTRATE

CPIPE TANK

360VFLO

W

CPIPE FINISH

CPIPE RAW

160VFLOW

CPIPE GAS

CPIPE FINISH

Fence Line

Fence Line

Fence Line

Fence Line

Happ

yCa

nyon

Cre

ek

5713

5715

5723

5712

5712

5708

5712

5717

5719

5714

5715

5706

5715

5716

5710

5711

5717

5716

5715

5716571

6

5716

5716

5718

5711 5714

5723

5716

5719

5720

5717

5716

5717

5723

5721

5719

5718

5717

5716

5715

5714

5713

5717

5716

5715

5714

5713

5713

5712

5711

5710

5708

5706

5707

5708

5709

5722

5720

5712

5708

5713

5714

57135712

5711

5721

5716

5722

5721

5720

5724

5723

5722

5721

5715

5718

5719

5720

5716

5711

5715

5714

5718

5719

5718

5710

5712 5713

5716

5717

5721

5713

5712

5714

0 10050

Feet

LEGEND

StreamBuildingSanitary LineStorm SewerTelephone LineTankFence LineWallOther PipesMiscelleous1ft ContourFEMA 100yr FloodplainParcel Boundary

Site Location

sricha13Rectangle

Appendix B

Alternative 1 Configuration 0.95 MGD, Current Well Location

FIGURE 2Alternative 10.95 MGD - Current Well OptionJoint Water Purification PlantArapahoe County, Colorado

I:\665063_COTTONWOOD_WATER_SANITIATION_DISTRICT\GIS\MAPFILES\MGD_0_95_CURRENT_WELL_OPTION.MXD JQUAN 10/13/2015 11:06:47 AM

VICINITY MAP

CPIPE TANK

360VFLOW

160VFLO

W

CPIP

E FINISH

CPIPE CONCENTRATE

CPIP

E FINISH

CPIP

E CO

NC

EN

TRATE

Fence Line

Fence Line

Fence Line

Fence Line

Happy Canyon Creek

VDF0.65 acres

VUF0.14 acres

APC0.66 acres

APC0.66 acres

VDF0.65 acres

VUF0.14 acres

VDF0.65 acres

VUF0.14 acres

0 10050

Feet

LEGEND

StreamBuildingSanitary LineStorm SewerTelephone LineTankFence LineWallOther PipesMiscelleousFEMA 100yr FloodplainParcel BoundaryVDFVUFAPC

Site Location

24

Appendix C

Alternative 3 Configuration 0.95 MGD, 6 Acre Wetland and Bioreactor Option

FIGURE 3Alternative 30.95 MGD - Current or Relocated Well OptionJoint Water Purification PlantArapahoe County, Colorado

I:\665063_COTTONWOOD_WATER_SANITIATION_DISTRICT\GIS\MAPFILES\MGD_0_95_CURRENT_RELOCATED_WELL_OPTION.MXD JQUAN 10/16/2015 8:51:37 AM

VICINITY MAP

CPIPE TANK

360VFLOW

160VFLO

W

CPIP

E FINISH

CPIPE CONCENTRATE

CPIP

E FINISH

CPIP

E CO

NC

EN

TRATE

Fence Line

Fence Line

Fence Line

Fence Line

Happy Canyon Creek

VDF0.43 acres

VDF0.43 acres

VDF0.43 acres

0 10050

Feet

LEGEND

StreamBuildingSanitary LineStorm SewerTelephone LineTankFence LineWallOther PipesMiscelleousFEMA 100yr FloodplainParcel BoundaryVDFWetland

Site Location

Appendix D

Treatment Performance Data

JWPP Concentrate Selenium Treatment Options - 83% RO Recovery, 0.95 MGD

Alternative 1: Selenium Biochemical ReactorWell

LocationFeed Rate

(mgd)Biological

CellSe in

(mg/L)Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

BOD k (m/yr)

Cell Depth(m)

Cell Depth(ft)

HLR (cm/d)

HRT(d)

Area(ac)

Relocated 0.95 N VDF 0.0171 0.0137 62 9.00 1.50 1876 N/A N/A N/A 1.5 4.9 69.8 1.5 1.27Relocated 0.95 VDF 0.0137 0.0046 675 1.50 0.21 1876 N/A N/A N/A 1.5 4.9 129.0 0.8 0.69Relocated 0.95 VUF 0.0046 0.0040 139 0.21 0.07 1876 N/A N/A N/A 1.5 4.9 211.1 0.5 0.42Relocated 0.95 APC1 N/A N/A N/A N/A N/A N/A 100 45 547 1.2 3.9 136.6 0.4 0.65Relocated 0.95 APC2 N/A N/A N/A N/A N/A N/A 45 21 547 1.2 3.9 135.6 0.4 0.66

Total Bioreactor HRT and Area: 3.58 3.69 114% of Se GoalCurrent 0.95 N VDF 0.0415 0.0330 62 9.00 1.50 1876 N/A N/A N/A 1.5 4.9 69.8 1.5 1.27Current 0.95 VDF 0.0330 0.0046 675 1.50 0.06 1876 N/A N/A N/A 1.5 4.9 68.8 1.6 1.29Current 0.95 VUF 0.0046 0.0040 139 0.06 0.02 1876 N/A N/A N/A 1.5 4.9 211.1 0.5 0.42Current 0.95 APC1 N/A N/A N/A N/A N/A N/A 100 45 547 1.2 3.9 136.6 0.4 0.65Current 0.95 APC2 N/A N/A N/A N/A N/A N/A 45 21 547 1.2 3.9 135.6 0.4 0.66

Total Bioreactor HRT and Area: 4.32 4.29 114% of Se Goal

Alternative 2: Constructed Wetland

Well Location

Feed Rate(mgd) Wetland Option

Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

Marsh Zone

Depth (m)

Deep Zone Depth (m)

HLR (cm/d)

HRT(d) Area

Relocated 0.95 Wetland - 6 Acre 0.0171 0.0139 12 9.00 4.04 44.70 0.5 1.0 14.8 4.4 6.00 33% of Se GoalRelocated 0.95 Wetland - Calc 1 0.0171 0.0108 12 9.00 1.50 44.70 0.5 1.0 6.5 10.1 13.73Relocated 0.95 Wetland - Calc 2 0.0108 0.0046 19 1.50 0.02 44.70 0.5 1.0 4.9 13.4 18.11

Total Constructed Wetland HRT and Area: 23.5 31.84 100% of Se GoalCurrent 0.95 Wetland - 6 Acre 0.0415 0.0335 12 9.00 4.04 44.70 0.5 1.0 14.8 4.4 6.00 14% of Se GoalCurrent 0.95 Wetland - Calc 1 0.0415 0.0257 12 9.00 1.50 44.70 0.5 1.0 6.5 10.1 13.73Current 0.95 Wetland - Calc 2 0.0257 0.0046 19 1.50 -0.13 44.70 0.5 1.0 2.4 27.1 36.64

Total Constructed Wetland HRT and Area: 37.2 50.37 100% of Se Goal

Alternative 3: Selenium Biochemical Reactor and Wetland

Well Location

Feed Rate(mgd) Biological Cell

Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

Cell Depth

(m)

Cell Depth(ft)

Marsh Zone Depth

(m)

Deep Zone Depth(m)

HLR (cm/d)

HRT(d)

Area(ac)

Relocated 0.95 N VDF 0.0171 0.0137 62 9.00 1.50 1876 N/A N/A 1.5 4.9 N/A N/A 69.8 1.5 1.27Relocated 0.95 Wetland 0.0137 0.0046 19 1.50 -0.01 44.70 100.00 32.62 N/A N/A 0.5 1.0 3.3 19.8 26.83

Required HRT and Area: 21.4 28.10 100% of Se GoalRelocated 0.95 N VDF - 6 acre 0.0171 0.0137 62 9.00 1.50 1876 N/A N/A 1.5 4.9 N/A N/A 69.8 1.5 1.27Relocated 0.95 Wetland - 6 acre 0.0137 0.0108 19 1.50 0.80 44.70 100.00 69.01 N/A N/A 0.5 1.0 18.8 3.5 4.73

Required HRT and Area: 5.0 6.00 43% of Se GoalCurrent 0.95 N VDF 0.0415 0.0330 62 9.00 1.50 1876 N/A N/A 1.5 4.9 N/A N/A 69.8 1.5 1.27Current 0.95 Wetland 0.0330 0.0046 19 1.50 -0.08 44.70 100.00 22.68 N/A N/A 0.5 1.0 1.6 40.6 54.92

Required HRT and Area: 42.1 56.19 100% of Se GoalCurrent 0.95 N VDF - 6 acre 0.0415 0.0330 62 9.00 1.50 1876 N/A N/A 1.5 4.9 N/A N/A 69.8 1.5 1.27Current 0.95 Wetland - 6 acre 0.0330 0.0256 19 1.50 0.80 44.70 100.00 69.01 N/A N/A 0.5 1.0 18.8 3.5 4.73

Required HRT and Area: 5.0 6.00 18% of Se Goal

JWPP Concentrate Selenium Treatment Options - 75% RO Recovery, 1.33 MGDAlternative 1: Selenium Biochemical Reactor

Well Location

Feed Rate(mgd)

Biological Cell

Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

BOD k (m/yr)

Cell Depth(m)

Cell Depth(ft)

HLR (cm/d)

HRT(d)

Area(ac)





Well Location


Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

Marsh Zone

Depth (m)

Deep Zone Depth (m)

HLR (cm/d)

HRT(d) Area





Well Location


Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

Cell Depth

(m)

Cell Depth(ft)

Marsh Zone Depth

(m)

Deep Zone Depth(m)

HLR (cm/d)

HRT(d)

Area(ac)

Relocated 1.33 N VDF 0.0134 0.0115 62 9.00 1.50 1876 N/A N/A 1.5 4.9 N/A N/A 97.8 1.1 1.27Relocated 1.33 Wetland 0.0115 0.0046 19 1.50 0.05 44.70 100.00 36.21 N/A N/A 0.5 1.0 4.1 16.2 30.68





JWPP Concentrate Selenium Treatment Options - 65% RO Recovery, 1.95 MGDAlternative 1: Selenium Biochemical Reactor

Well Location

Feed Rate(mgd)

Biological Cell

Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

BOD k (m/yr)

Cell Depth(m)

Cell Depth(ft)

HLR (cm/d)

HRT(d)

Area(ac)





Well Location


Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

Marsh Zone

Depth (m)

Deep Zone Depth (m)

HLR (cm/d)

HRT(d) Area





Well Location


Se in (mg/L)

Se out (mg/L)

Se k (m/yr)

NO2/3-Nin (mg/L)

NO2/3-Nout (mg/L)

NO2/3-N k (m/yr)

BOD in (mg/L)

BOD out (mg/L)

Cell Depth

(m)

Cell Depth(ft)

Marsh Zone Depth

(m)

Deep Zone Depth(m)

HLR (cm/d)

HRT(d)

Area(ac)

Relocated 1.95 N VDF 0.0105 0.0095 62 9.00 1.50 1876 N/A N/A 1.5 4.9 N/A N/A 143.3 0.8 1.27Relocated 1.95 Wetland 0.0095 0.0046 19 1.50 0.15 44.70 100.00 41.30 N/A N/A 0.5 1.0 5.3 12.5 34.67





26

Appendix E

Alternative 1: BCR Capital Cost Estimate Relocated Well Option ‐ 83% RO Recovery, 0.95 MGD

Alternative 1: BCR Capital Cost Estimate Relocated Well Source ‐ 83% RO Recovery, 0.95 MGD

Item Cost ($)

Vertical Downflow Wetland 569,000

Vertical Upflow Wetland 262,000

Aerobic Polishing Cells 811,000

Overall Sitework 83,000

Plant Computer System 34,000

Yard Electrical 72,000

Yard Piping 100,000

Access Roads 56,000

Contractor Markup ‐ Overhead 199,000

Contractor Markup ‐ Profit 110,000

Contractor Markup ‐ Mob/Bonds/Insurance 115,000

20% Construction Cost Contingency: 482,000

Total Construction Cost: 2,893,000

Total Non‐Construction Costs: 634,000

Total Capital Cost: 3,527,000 NON‐CONSTRUCTION COSTS INCLUDE ENGINEERING, SERVICES DURING CONSTRUCTION, COMMISSIONING & STARTUP AND LEGAL/ADMIN

CHERRY CREEK BASIN WATER QUALITY AUTHORITY 2015 Capital Project and Maintenance Status Report

December 24, 2015

1. Cherry Creek Stream Reclamation at Norton Farms (CCB 5.11) a. Description: Final design and construction of stream reclamation at Parker’s Norton Farms Open Space

Park in partnership with Town of Parker and UDFCD. b. Status: Board approved $30,000 for design and signed IGA with UDFCD and Parker on 05/16/13. Board

approved $225,000 for construction on September 18, 2014 and signed IGA Amendment with UDFCD and Parker.

c. Action Items: Project final design is moving forward. 53 Corporation was selected as the project contractor. The 404 permit ia approved for the project. The construction is slated to begin in early January 2016.

2. Cherry Creek Stream Reclamation – CCSP to EcoPark (aka: Arapahoe Rd, CCB 5.14) a. Description: Preliminary design of stream reclamation in partnership with SEMSWA, UDFCD, Aurora,

and Arapahoe County. Project extends from Cherry State Park boundary to Eco-Park (Reaches 2 - 5). b. Status: Board approved $25,000 for design funding on 12/20/12 which provided $150,000 for final

design. Board approved $500,000 IGA amendment for construction on 10/17/13. Board approved $250,000 IGA amendment for construction on 5/21/14. UDFCD is project lead agency on Reach 5; SEMSWA is project lead agency on Reach 2. Reach 5 - Drop Structure #14 - construction started in 6/14 w/ Edge Construction. Construction is complete on Drop Structure 14; the final walk-thru was performed on 11/6/14.

c. Action Items: Assist project partners with engineering planning, design and construction. i. Reach 5 - ECI Construction was selected as the project contractor. Construction Notice to Proceed

was issued on 9/21/15; construction completion date is 3/19/16. Construction is 8% complete. ii. Reach 2 - CH2MHill was selected as the Engineer for this project. Design continues on the project

with construction anticipated to start in 2016. The 95% construction plan set is submitted for agency review. The 404 permit process is underway.

3. Piney Creek Stream Reclamation - at Caley Avenue (CCB 6.5)

a. Description: Design of the stream reclamation in partnership with UDFCD and SEMSWA. b. Status: CH2MHill was selected as the Engineer for both the Piney Creek Reach 6 and 7 projects.

UDFCD, under a separate contract hired Stanley Consultants to perform a geomorphic study for Piney Creek upstream of Buckley Road to better understand the sediment transport through Piney Creek. The final draft was submitted on December 22, 2014. Board approved $50,000 IGA amendment for project design on 8/21/14 and an additional $500,000 on 8/20/15. Preliminary design continues on the project with construction anticipated to start in the fall of 2015.

c. Action Items: Assist project partners with engineering design & construction. Project partners are meeting to determine the best approach to stabilize the most critical sections of Reach 6 and 7 in a logical sequence based on funds available. Project approach combines stream reclamation details from Stantec's geomorphic approach with CH2M Hill's hydraulic analysis / traditional stream design approach. Additional sources of potential funding are being identified and contacted for grant assistance. All projects are being designed to the fifty percent level, at which time the project sponsors will review the best approach to proceed with available funding. Sediment samples have been taken along Piney Creek and sent to ACZ Laboratories for total phosphorus testing. The initial cultural resources survey identified three potential sites in Reach 6 (The Ranches). Recent flooding has created additional erosion. Design/Build options are being evaluated with close permitting coordination with the Corps. Survey has been completed on the Tower Road section of Piney Creek where deposition occurred during recent storms. This area is identified as a material source for the upstream reaches as needed. Edge Contracting, Inc., was selected as the project contractor for Reach 6. Left Hand Construction was selected as the project contractor to remove sediment from Piney Creek downstream of Tower Road.

MAINTENANCE

1. Reservoir De-stratification Operations (OM-7) a. Description: Routine operations and maintenance of aeration distribution system and compressor. b. Status: Board directed staff to prepare an O&M manual for 2013. The aeration system stopped operating

on 10/22/13 due to motor failure. The motor and 16,000 hour service parts were installed on 04/16/14 and 04/17/14. The exposed section of HDPE pipe was replaced on 04/10/14. Piping in the manholes was modified on 06/11/14 so that the compressor can be exercised weekly without any air entering the underwater destratification mixing system. Exercising the compressor was performed during the 2014 and 2015 aeration seasons.

c. Action Items: The system is shut down for the winter.

2. PRF Weed Control (OM 14.1) a. Description: Weed control at PRFs within Cherry Creek State Park who contracts with weed-control

company (VMI) and Authority pays VMI directly for related work. b. Status: Mowing and chemical application work completed for 2014. c. Action Items: None.

3. PRF Reseeding at CCSP (OM 14.2)

a. Description: Routine restoration of PRF vegetation at Cherry Creek State Park. b. Status: On hold c. Action items: None.

4. PRF Maintenance Activities a. Maintenance work identified in the 2015 CIP was approved by the Board on 9/17/15. Improvements will be completed this fall. Grading work at Mountain-Lake Loop and Cottonwood Creek Phase 1 sites is complete. Boulder work at the Cottonwood Wetland outlet structure is complete. Work at 12-Mile Park, Phase 2 remains outstanding, as well as revegetation at all sites.

CHERRY CREEK RESERVOIR

DESTRATIFICATION FACILITIES

OPERATION AND MAINTENANCE

ANNUAL REPORT

2015

i

Prepared For:

Prepared By:

JRS Engineering Consultant LLC 6013 E. Briarwood Drive Centennial, CO 80112 (303) 726-5577 James R. “Jim” Swanson P.E.



℅ CHUCK REID CLIFTONLARSONALLEN LLP

8390 E CRESCENT PARKWAY, SUITE 500 GREENWOOD VILLAGE, CO 80111

ii

COVER .………………………………….…………......…………………..……………………..............

PRESENTATION ..……..….………………………………..……………………....……....................... Page i

TABLE OF CONTENTS .….………………………………..……………………....…........................... Page ii

INTRODUCTION.…….………………………………………………………………..……..................... Page 1

START-UP PROCEDURE AND OPERATING POLICY UPDATE................................................... Page 1

2015 START-UP.............................................................................................................................. Page 2

OPERATION PERIOD / INSPECTIONS.…………….………………………………..…..................... Page 2

EQUIPMENT REPAIRS AND MAINTENANCE ………..………………............................................... Page 3

ELECTRICAL USAGE / RATE SCHEDULE........................................................................................ Page 3

RECOMMENDATIONS ...................................................................................................................... Page 3

APPENDIX A - OPERATION POLICY REGARDING ICE

APPENDIX B - DESTRATIFICATION SYSTEM COMPRESSOR START-UP PROCEDURE

APPENDIX C - 2015 AERATION EQUIPMENT OPERATING DATA LOG

APPENDIX D - 2015 ELECTRICAL MONITORING LOG

APPENDIX E - 2015 AERATION SYSTEM MAINTENANCE SUMMARY

TABLE OF CONTENTS

1


℅ Chuck Reid

CliftonLarsonAllen

8390 E. Crescent Parkway, Suite 500

Greenwood Village, Colorado 80111

CHERRY CREEK BASIN WATER QUALITY AUTHORITY RESERVOIR DESTRATIFICATION FACILITIES

cherry creek basin water quality authority · 2016-01-13 · cherry creek basin water quality...

Documents