St Tammany Parish comments on the Pearl River Basin, Mississippi Section 211  Feasibility Study – Integrated Draft Feasibility and Environmental Impact Statement  

St. Tammany Parish is providing items that we believe should be included in the soon to be released  document, Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft Feasibility  and Environmental Impact Statement. Recommendations are made on 1) technical inadequacies, 2)  types of analyses that should be provided, 3) expanding the modeling domain/impact area and 4)  necessary clarifications based on review of the public meeting notes and draft Feasibility & EIS Report  (6/2018).  

The four conceptual alternatives presented in the draft Study are listed below, with the alternative  preferred by the Rankin Hinds Pearl River Flood & Drainage Control District being the “Levees with  Lake”:  

• No Action  
• Non-Structural Measures (elevations & relocations)  
• Structural Measures/Levees and Floodwalls  
• Lake Development – Excavate inside and outside of River channel (Locally Preferred  Alternative C)  

Overview of the Preferred Alternative C: Lake Development  

The locally preferred alternative (per the EIS) consists of a 1900 surface acre impoundment with a weir  forming a dam at the lower end. The Pearl River will be widened from about 300 feet to between 1,000  and 2,000 feet. Dredge spoil from the widening will be deposited around the proposed lake’s perimeter, presumably to elevate the land. All spoil is proposed to be deposited within 1,000 feet of the centerline  of the River, much of which is currently wetlands. There will be habitat impacts for two species that are  indigenous to the Pearl River and are protected by the Endangered Species Act.  

St. Tammany Parish objects to the Alternative C “Lake Development” and the “Levees and Floodwalls”  options due to the hydrologic changes and impacts from each. Development in the form of levees and  impoundments in the Pearl River Watershed upstream of St. Tammany Parish could have significant  adverse impacts on a wide range of concerns, including: 

• Water Quantity & Quality
• Business & Industrial Activity
• Population Growth
• Recreation Resources
• Groundwater & Salt Water Intrusion
• Threatened & Endangered Species
• Aquatic & Wildlife Resources  
• Community Cohesion, Cultural & Socioeconomic Resources  
• Recreational & Commercial Fisheries  

The underlined subjects are discussed in more detail, below. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 1  

Water Quantity  

Throughout this discussion, the concept of “low-flow” and “high flow” will be discussed. There are  multiple ways to present these concepts for stream baseflow:  

• The 7Q10 is the minimum low-flow for seven (7) consecutive days in 10 years (established by  USGS for a specific period of record).  
• The 5th percentile is the minimum stream baseflow used by EPA and MSDEQ to establish  permits when the 7Q10 is not available.  
• The 10th percentile minimum stream baseflow used by many hydrologists as a surrogate for  “critical low flow”.  

In summary, 7Q10 < 5th percentile < 10th percentile; thus, the most conservative of the low-flow  surrogates, 10th percentile, will be utilized throughout the discussion below. For high-flow, the 90th percentile will be used for comparisons of pre- versus post- construction of the Ross Barnett (RB)  Reservoir.  

The period of record is also critical to any pre- vs post- RB comparison. St. Tammany considers the  correct period-of-record for comparisons to be pre-Ross Barnett (1938-1960) and post-Ross Barnett  (1965-present). Figure 1 is a map of the Pearl River Basin indicating areas of concern and providing  analyses at these locations.  

USGS 02486000 (Pearl River at Jackson, MS)  

Construction of the Ross Barnett Reservoir (RB) began in 1960 and was completed in 1963. The  33,000 surface acre lake reached “full-pool” capacity in 19651. Following construction of the Ross  Barnett Reservoir near Jackson, MS. Minimum Mean Daily Discharges have remained approximately  the same, from 45 cfs (10/5/1956) to 47 cfs (6/14/1984) for pre-RB versus post-RB, respectively  (Figure 2).  

Extreme low-flows at Jackson were approximated using historic Minimum Mean Daily Discharge by  Month at the gage USGS 02486000 Pearl River at Jackson, MS for the post-RB period of record (1965- 2018). Minimum Mean Daily Discharges by month indicate flows will not meet the minimum 227 cfs  required for Savannah St. WWTP, except during high-flow events in February and March (Table 1).  

Comparing Average Monthly Discharges for the Pre- and Post-RB periods of record, it can be seen that  during the low-flow months, May – November, flows from the RB Reservoir were fairly homogenous  and somewhat higher than pre-RB. However, during the critically low- flow months of July and  August, flows from the Ross Barnett are lower post- than pre-RB (Table 2). Average Monthly  Discharge values are not detailed enough to quantify the low-flow incidences that may cause  significant harm to the downstream NPDES permittees and the environment.  

  

1 Engineer provided date of Ross Barnett “full pool” for the Rankin-Hinds Pearl River Flood and Drainage Control District  during a public meeting held in Slidell, LA on 8/16/2018. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 2  

Figure 1. Pearl River Basin Locations of Concern 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 3  

Figure 2. Pearl River Reach near Proposed Alt. C Impoundment with Flow Characteristics 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 4  

Table 1. Minimum Mean Daily Flows by Month for  

USGS 02486000 Pearl River at Jackson, MS  

USGS 02486000 Pearl River at Jackson, MS  Minimum Mean Daily Discharges by Month  (1968-2018)
Month	Pre-RB   (1938-1960)	Post-RB   (1965-2018)
	Minimum   Discharge, cfs	Minimum   Discharge, cfs
January	276	218
February	590	298
March	806	262
April	707	213
May	350	192
June	270	47
July	151	92
August	103	91
September	79	88
October	45	100
November	85	92
December	131	154
Months in which flows Post-TB < Pre-RB

 

Table 2. Average Monthly Discharges by Month for  

USGS 02486000 Pearl River at Jackson, MS 

USGS 02486000 Pearl River at Jackson, MS  Average Monthly Discharges (1968-2018)
Month	Pre-RB   (1938-1960)	Post-RB   (1965-2018)
	Average   Monthly   Discharge, cfs	Average Monthly Discharge, cfs
January	5,757	7,643
February	9,488	9,208
March	8,725	9,015
April	7,719	8,610
May		4,153 1,715
June	1,640	1,713
July	1,819	1,124
August		956 1,028
September		1,124 507
October		1,252 461
November		2,000 1,128
December		5,013 2,588
Months in which stream baseflows < 227 cfs required for  Savannah St. WWTP permit

 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 5  

A 7Q10 of 227 cfs is the minimum stream baseflow measured on the USGS gage at Jackson required  by MSDEQ for the most recent permit renewal (2017) for the 46 MGD City of Jackson Savannah St.  WWTP discharge. Post-RB, there were 1,613 failures (7.7%) to meet this minimum flowrate (Figure  1). Mean Daily Discharge on the gage at Jackson show many measurements that are lower than the  

required 227 cfs for City of Jackson, Savannah St. Wastewater Treatment Plant (WWTP), as seen on  the hydrograph in Figure 3.  

Figure 3. Mean Daily Discharge for USGS 02486000 (Pearl River at Jackson, MS) for the period of record  

The previous NPDES permit for the Savannah St. WWTP set the stream baseflow at 290 cfs for which  there were 3,917 failures (18.7%). It seems counter intuitive that the permit should have been issued with a lower stream baseflow, with the River’s history of not attaining adequate flow. A TMDL for  Nutrients2 was implemented by EPA and MSDEQ in 2015 for the Pearl River from Ross Barnett to the  Strong River. It seems plausible that inadequate stream baseflow at the Jackson gage during summer critical conditions may be contributing to the lack of assimilative capacity at this location in the River  incurring the TMDL.  

The EIS authors stated in a public meeting that Richland Creek discharges into the Pearl River between the USGS gage 02486000 Pearl River at Jackson, MS and the Savannah St. WW TP discharge,  contributing to the stream baseflow (Figure 1) that would augment the facility’s permit requirements.  

• Richland Creek has a 7Q10 of 0.9 cfs3, which is inadequate for substantive flow augmentation  for the WWTP (USGS 1991).  

  

  

2 Total Maximum Daily Load Total Nitrogen and Total Phosphorous for the Pearl River from Ross Barnett Reservoir to the  Strong River (Hinds, Rankin, Simpson and Copiah Counties) Pearl River Basin. MSDEQ. MSDEQ, Office of Pollution  Control, Modeling and TMDL Branch. 2015.  

3 USGS. 1991. Low-Flow and Flow-Duration Characteristics of Mississippi Streams. USGS Water Resources Investigations  Report 90-4087. Table 2. Low-Flow characteristics for partial-record stations. Page 153. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 6  

Another approach to quantify low-flow is to use a 10th percentile comparison. Pre-RB 10th percentile  stream baseflow at the Jackson gage was 192 cfs with 828 gage measurements (10%) failing to reach  that flow rate. Post-RB 10th percentile stream baseflow is 244 cfs, but with a larger number of  measurements <10th percentile (1,924) failing to meet the flowrate.  

Finally, using the 10th percentile approach and comparing pre- and post- RB for the USGS gage at  Jackson, Table 3 quantifies the differences in pre- and post-RB. Many of the 10th percentile critical  low-flows are lower post-RB and do not satisfy the minimum stream baseflow required for the  Savannah St. WWTP 7Q10. It is apparent that flow control at the RB Reservoir is making the stream  baseflow lower at least during July and August, summer-critical months for NPDES dischargers, water  quality, habitat, recreation, navigation and coastal interests.  

• It is strongly suggested that the Ross Barnett Reservoir minimum discharges be increased.  

Table 3. 10th Percentile Monthly Mean Daily Flows for  

USGS 02486000 Pearl River at Jackson, MS  

Monthly Mean Daily Flows
Gage Data USGS 02486000 Pearl River @ Jackson, MS
Month	Pre- Ross Barnett  (1938-1960)	Post- Ross Barnett (1965-2018)
	10th percentile   Monthly Average  Discharge, cfs	10th percentile   Monthly Average  Discharge, cfs
January	955	781
February	1960	1625
March	2763	1711
April	1870	232
May	588	274
June	350	239
July	238	232
August	222	214
September	141	212
October	99	206
November	123	223
December	205	293
Values are <227 cfs required by MSDEQ to satisfy Savannah  St WWTP (2017)
[1] Evap losses, EIS Appendix C, Table 5-1, pg 10.

 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 7  

USGS 02488500 (Pearl River at Monticello, MS)  

Monticello, MS is the location of a large NPDES discharger, Georgia Pacific (GP) Paper Mill (Figure  4). The 10th percentile flow post-RB is 512 cfs measured at the gage USGS 02488500 Pearl River at  Monticello, MS, of which there were 854 measurements that failed to meet the 10th percentile (11%).  

The historic minimum flow at that location is 4.02 cfs. Residents along the River relay stories that the  water was so low at that time that one could walk across to the other bank.  

Figure 4. Pearl River Reach near Monticello, MS with Flow Characteristics  

 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 8  

The 7Q10 for the 26.04 MGD (40.3 cfs) GP facility requires a stream baseflow of 760 cfs. There were  4,051 Daily Mean Discharge measurements (20%) that failed to meet that minimum. The Strong  River, upstream of the Monticello gage, augments flow at this location (Figure 1); however, the post RB 10th percentile for the Strong is 36 cfs measured at USGS 02487500 Strong River at D’Lo, MS.  1,160 Daily Mean Discharges failed to meet the 10th percentile (10%). The historic minimum was 12  cfs (8/31/2000).  

• Clearly, stream baseflow, even with augmentation from the Strong River, is inadequate to meet the permit needs for this facility.  

USGS 02489500 (Pearl River at Bogalusa, LA) 

Bogalusa, LA is the location of a large NPDES discharger, International Paper (IP) Mill (Figure 5). The  10th percentile flow post-RB is 1,920 cfs, of which there were 2123 Daily Mean Discharges that failed  to meet the 10th percentile (11%). The historic post-RB minimum flow at that location is 1,080 cfs.  The 7Q10 for the 16 MGD (24.8 cfs) IP facility requires a stream baseflow of 1,260 cfs. There were  162 post-RB Daily Average Discharge measurements (0.8%) that failed to meet that minimum. While  the minimum stream baseflow for this facility was well determined for the permit, there is little margin  of safety in the stream baseflow, potentially incurring in-stream water quality violations during  summer-critical conditions.  

• There is a need for additional stream baseflow augmentation at this location in the Pearl River. Figure 5. Pearl River Reach near Bogalusa, LA with Flow Characteristics 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 9  

USGS 2492110 (East Pearl River ab Wilson Slough at Walkiah Bluff)  

This site is of particular interest to oyster culture in coastal MS and LA (Figure 5). Adequate freshwater  during summer critical conditions is necessary to mitigate the effects of saltwater intrusion and  survivability of oysters in Lake Pontchartrain and the Mississippi Sound. Walkiah Bluff was constructed  by the USACE to divert freshwater to the East Peal River during low-flow conditions. The 10th percentile Daily Mean Discharge measured at this gage is 1,660 cfs, of which 162 measurements <10th percentile (2007-2018). The historic minimum flow was 1,340 cfs (10/15/2007). A significant amount  of debris is reportedly blocking the structure’s weir lessening the amount of fresh water being diverted.  

• It is suggested that the USACE conduct maintenance on the Walkiah Bluff structure to restore  its capacity.  

Combined Impacts of Additional Impoundment with an Already Dammed Pearl River  

Even without the addition of the proposed impoundment in Alt. C, it can be summarized that the Ross  Barnett Reservoir has changed the flow patterns and Daily Mean Discharges throughout the Pearl River  Watershed (Table 4). 10th percentile discharges are lowered in low-flow, summer-critical conditions  and are increased during 90th percentile high-flow events. The latter will be discussed in another  section.  

Table 4. Select USGS Gages in Pearl River Basin, Low Flow Summary  

USGS   Gage   Number	Description	7Q10, cfs	LOW-FLOW
			PRE-Ross Barnett (1938–1960)				POST-Ross Barnett (1965-2018)
			10th   Percentile, cfs	Number  Events   <10th   Percentile	Minimum  Discharge, cfs	Date	10th   Percentile, cfs	Number  Events   <10th   Percentile	Minimum  Discharge, cfs	Date
				% Events  <10th   Percentile				% Events  <10th   Percentile
2485601	Pearl River @ Ross Barnett  Reservoir	170   (post-1965)	–	–	–	–	–	–	–	–
2486000	Pearl River @ Jackson, MS	103   (1939-1960)		828	45 192	10/5/1956		1,924	47 244	6/14/1984
				10.1%				10.0%
	2486300 Richland Creek nr Jackson, MS	0.9	–	–	–	–	–	–	–	–
2487500	Strong River at D’Lo, MS	19   (1929-1970)		850	16 32	9/2/1954		1,160	12 36	8/31/2000
				10.1%				10%
2488500	Pearl River @ Monticello, MS	359   (1939-1960)	512	854		9/28/1956 289		2,033	4 617	10/18/2015
				11%				10%
2489500	Pearl River near Bogaulsa, LA	1,400   (1939-1960)		827	1,100 1,620	9/15/1954		2,123	1,080 1,920	10/26/1968
				10.20%				11.0%
2492110	East Pearl River ab Wilson  Slough @ Walkiah Bluff	(2007-2017)	–	–	–	–		162	1,340 1,660	10/15/2007
				–				7.40%

 

The EIS proposes to create an additional impoundment approximately 7.5 miles downstream of the  Ross Barnett Reservoir. The EIS authors have provided the Monthly Mean Discharges for the Pearl  River at Jackson for the entire period of record (Figure 3). Because the RB is essentially the new  headwater for this reach of the Pearl River, beginning in 1965 when it reached “full pool”, St.  Tammany Parish objects to the use of pre-RB data in determining flow impacts from the proposed  impoundment. St. Tammany provided the Monthly Mean Discharges by Month for the Jackson gage  pre- and post-RB previously in Table 2. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 10  

• Monthly Mean Discharges should be calculated using ONLY post-RB data when determining  flow impacts from the proposed impoundment.  

Evaporative Losses  

The EIS authors calculated evaporative losses from the proposed 1900 surface acre.  

• Evaporative losses subtracted from either the Minimum Daily Mean Discharges by Month (Figure 6) or the 10th percentile of Mean Daily Discharges (Table 5) indicate the already impacted Pearl River will be further compromised.  

Figure 6. Minimum Mean Daily Flows by Month minus proposed evaporative losses  

Seepage Losses  

Seepage losses/gains in the proposed impoundment were not addressed in the EIS. Losses would  require an increased minimum discharge from the Ross Barnett Reservoir in order to maintain adequate  downstream flows during low-flow events.  

• A geotechnical investigation is needed in order to determine whether there will be gains or  losses in the proposed impoundment due to groundwater effects. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 11  

Table 5. 10th Percentile of Mean Daily Discharges for USGS 02486000 Pearl River at Jackson, MS  

Monthly Mean Daily Discharges
Gage Data USGS 02486000 Pearl River @ Jackson, MS
Month	Pre- Ross Barnett  (1938-1960)	Post-Ross Barnett (1965-2018)
	10th percentile   Monthly Average  Discharge, cfs	10th percentile   Monthly Average  Discharge, cfs	Evap. loss, cfs [1]	10th percentile   Monthly Average  Discharge less   Proposed Evap.  loss, cfs
January	955	781	2.5	779
February	1960	1625	3.4	1622
March	2763	1711	5.3	1706
April	1870	232	7.7	224
May	588	274	9.2	265
June	350	239	10.1	229
July	238	232	9.9	222
August	222	214	9.1	205
September	141	212	7.5	205
October	99	206	5.2	201
November	123	223	3.6	219
December	205	293	2.6	291
[1] Evap losses, EIS Appendix C, Table 5-1, pg 10.
Values are <227 cfs required by MSDEQ to satisfy Savannah St WWTP (2017)

 

High Flow Impacts from the Combined Impoundments (Ross Barnett & Alt. C)  

The current proposal, Alt. C in the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated  Draft Feasibility and Environmental Impact Statement, is expected to demonstrate a reduction of flooding  in the Jackson, MS area due to lowering the tailwater condition, thereby speeding up flows. This  increase in flow due to loss of floodplain storage needs to be mitigated by a volume of storage created  downstream, which is proposed Alt. C impoundment.  

In Louisiana, both flood height and duration cause issues on a yearly basis during high flow events.  Further, at all Pearl River gage stations and tributaries assessed, the 90th percentile discharges increased  post-Ross Barnett, as did the maximum flows (Table 5). Table 5 also provides insight as to how many  Daily Mean Discharges were greater than the 90th percentile; in most cases this was in excess of 10%.   

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 12  

These “slugs” of water from Ross Barnett cause bank erosion and excessive sediment transport to  downstream reaches. St. Tammany Parish is concerned with how the proposed impoundment will  compensate for the “slugs” from the Ross Barnett.  

• An unsteady model showing both maximum flooding and duration of flooding needs to be run  for all conceptual alternatives over the entire model domain (Ross Barnett Reservoir to Lake  Pontchartrain and the Mississippi Sound.  
• As with low-flow considerations, the high-flow operational plan must be detailed in the EIS.  • Sediment transport should be included in the modeling effort in the EIS.  

Table 4. Select USGS Gages in Pearl River Basin, High Flow Summary  

USGS   Gage   Number	Description	HIGH-FLOW
		PRE-Ross Barnett (1938–1960)				POST-Ross Barnett (1965-2018)
		90th   Percentile, cfs	Number   Events   <90th   Percentile	Maxium   Discharge,  cfs	Date	90th   Percentile, cfs	Number   Events   <90th   Percentile	Maxium   Discharge,  cfs	Date
			% Events  <90th   Perccentile				% Events  <10th   Perccentile
2485601	Pearl River @ Ross Barnett  Reservoir	–	–	–	–	–	–	–	–
2486000	Pearl River @ Jackson, MS		833	49,600 10,300	2/17/1944	12,300	1924	126,000	4/17/1979
			10.1%				10%
2486300	Richland Creek nr Jackson, MS	–	–	–	–	–	–	–	–
2487500	Strong River at D’Lo, MS		844	20,900 1,500	1/7/1950		1163	30,100 1,363	4/8/2014
			10%				10.1%
2488500	Pearl River @ Monticello, MS		782	57,900 17,700	1/7/1950	20,100	2047	121,000	4/20/1979
			10.1%				10.1%
2489500	Pearl River near Bogaulsa, LA		1390	60,000 23,700	1/26/1947	30,300	1945	130,000	3/12/2016
			17.1%				10.0%
2492110	East Pearl River ab Wilson  Slough @ Walkiah Bluff	–	–	–	–		2236,930 4,510		8/4/2017
			–				10.1%

 

Summary Water Quantity Comments  

In summary, the headwater flow from the Ross Barnett Reservoir minimum discharge (170 cfs), less  the withdrawal for the City of Jackson Water Supply (-48 cfs) and adding the minimal input from  tributaries in the project area (most of which have 7Q10 = 0 cfs) is reflected in the USGS stream gage at Jackson. The Jackson gage reflects that for much of the year, flow is inadequate to provide the  minimal stream baseflow required for the Savannah St, WWTP (227 cfs) during summer critical  conditions. Further, the lack of adequate flow may have contributed to the water quality impairments  and promulgated TMDL in the area, due to lack of assimilative capacity. The location of the proposed  additional impoundment is critical for flow management. Additional stream baseflow is required even  without the additional losses incurred by Alt. C.  

• It is suggested that the Ross Barnett Reservoir should be encouraged to discharge a minimum  flow > 170 cfs required by the MS Board of Commissioners in 1956. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 13  

• A minimum flow release must be specified in the EIS and included in the reservoir operational plan for Alt. C.  
• In the operational plan, the tandem operations of the two gates from the respective reservoirs  must be detailed.  
• The minimum flows from both reservoirs should be formalized through an MOU between Ross  Barnett and proposed Alt. C impoundment for flow management and with the States of  Mississippi and Louisiana.  

Water Quality  

Currently the Pearl River and its distributaries are suffering from inadequate low flow that is impacting  water quality (from reduced assimilative capacity), discharge limits for effluent dischargers (such as International Paper), recreation (due to shallow draft limitations), fish populations (due to low  dissolved oxygen concentrations), aesthetics (impacting swamp tours in St. Tammany Parish), and  saltwater intrusion (affecting drinking water wells, habitat, and coastal marshes) in the lower portion of  the Pearl River.  

Significant environmental impacts exist that are partially attributable to the Ross Barnett Reservoir  discharging inadequate volumes during low flow months. Without adequate flow from Jackson, the  assimilative capacity of the Pearl River will continue to be compromised and the River subsegments  will remain impaired. In fact, EPA has promulgated 21 Total Maximum Daily Loads (TMDL) for  subsegments of the Pearl River in Louisiana and 49 in Mississippi for various pollutants. Failure to  improve the water quality in these stream segments may result in a reduction of development in the  watershed, due to permit denials.  

A number of TMDLs have been promulgated for the Alt. C reach of the Pearl River (Figure 7). The  2015 EPA Nutrient TMDL4 (Ross Barnett to the Strong River) is a major concern to all downstream  stakeholders. The Pearl River in that extensive reach is impaired for low dissolved oxygen (DO) due to nutrients from NPDES dischargers and from nonpoint sources (NPS) from nine (9) Multiple Separate  Storm Sewer System (MS4) communities in the project area. The TMDL calls for a 70% reduction in  Total Phosphorous, much of which must be from reductions in NPS loading from the nine (9) MS4s.  

These tributaries are a major source of pollutants into the Pearl during rainfall events and will discharge  into the proposed impoundment. Without significant water quality improvements from aggressive MS4  and Ross Barnett activities, the water quality in the proposed impoundment will certainly be eutrophic,  incur algae blooms and dissolved oxygen collapse, and potentially exceed CWA standards.  

• Discharges from the proposed Alt. C impoundment will compromise the downstream reaches  even more than the Ross Barnett currently does. 

  

4 Total Maximum Daily Load for Total Nitrogen and Total Phosphorous for the Pearl River from Ross Barnett Reservoir to  the Strong River, Hinds, Rankin, Simpson, and Copiah Counties, Pearl River Basin. Prepared by MDEQ, Office of  Pollution Control, Modeling and TMDL Branch. April 2015. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 14  

Figure 7. EIS Table 3.1 presenting TMDLs in the Study Area  

The West Pearl River in St. Tammany Parish already experiences many environmental consequences  resulting from reduced flow being released from the Ross Barnett, specifically: Quiescence, water  quality degradation, eutrophication and invasive aquatic macrophytes, shoaling, navigation  impediments, saltwater intrusion into the River and shallow drinking water wells, loss of habitat, loss of  commercial fisheries and risk from wasteload allocation (WLA) excursions from the International  Paper (IP) Mill5 in Bogalusa.  

• As discussed previously, all vulnerabilities result from lack of volume and reduced velocity  from the headwaters during critical low-flow months. Thus, any additional headwater reductions are environmentally unacceptable.

  

  

5 Permit limits for the IP Mill were determined from the LDEQ modeling effort published 12/03/2013. Results of the Final  – Evaluation of Biochemical Oxygen Demand Loading from the International Paper – Bogalusa Paperboard Mill (AI#  38936, LPDES# LA0007901) into the Pearl River (Subsegments 090101 & 090107) were utilized to verify permit limits for  the discharger. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 15  

Sediment Loading downstream of the proposed impoundment  

It was pointed out during a public meeting by a resident in Slidell, LA that the shape of the proposed weir is stated to reduce maintenance; presumably, this will reduce dredging needs in the proposed  impoundment. The resident was concerned that the 12’x12’ gates would be opened to release slugs of  sediment that will travel downstream. Some sediment is necessary to maintain bank stability, but an  excess will add to the over-burdened lower Pearl River.  

• St. Tammany Parish would like the EIS to include a discussion of the maintenance procedures  to maintain Alt. C storage capacity and to minimize downstream sediment loading.  

Stakeholders are assured in the EIS that since 96% of the water into the proposed impoundment will be  from the Ross Barnett Reservoir, water quality in the proposed lake will be similar to that in Ross  Barnett Reservoir (EIS Appendix D, Environmental, pg.135):  

However, the water quality of the RB was determined to be impaired for nutrients and temperature.  Following the draft TMDL for Nutrients (MSDEQ 2009), a Water Quality Management Plan was  developed for the Ross Barnett Reservoir (EIS Appendix D, Water Quality, Pg.11):  

 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 16  

Water quality sampling was conducted by the EIS team in July 2014 (EIS Appendix D, Water Quality,  pg.26) presumably to verify “current summer-critical conditions,” and/or to gauge the progress from the  RB SW Management Plan (above). Sampling locations included two on the Pearl River (downstream  of the Ross Barnett Reservoir, upstream of the Jackson water supply intakes) and at three of the  tributaries that will discharge into the proposed impoundment. As seen in Figure 8 (EIS Appendix D,  Water Quality, Pg.43), there were significant failures of DO criteria at two Pearl River sites (Ross  Barnett and Jackson water supply), and failure of temperature standard at three Pearl River sites and  one tributary that discharges into the proposed impoundment.  

Figure 8. Sample Comparison to Water Quality Standards, July 2014  

Further, water quality in the tributaries discharging into the proposed impoundment is dominated by  NPS from the nine MS4s on those tribs. The EIS authors are certain that the 2011 Stormwater Master  Plan enacted to improve water quality from the MS4s will provide relatively “clean” water to the  impoundment. The TMDLs listed in Figure 5 indicate that one of the tribs. (Hanging Moss Creek) has  its own TMDL for BOD, Nutrients and Sediment (2009).  

• The EIS must address whether WQ improvements have been achieved in the MS4s and the Ross  Barnett discharges in the seven (7) years since the Stormwater Master Plan and TMDL were  promulgated.  
• Does the proposed impoundment have a plan to improve water quality prior to release?   

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 17  

Water Quality Modeling  

The modeling effort utilized a 1-D, steady-state approach. While this may be effective when developing a “snapshot” of “worst case” conditions, as with a TMDL, it is not appropriate for average advective  conditions where many tributaries and distributaries confluence in the main stem of the Pearl River.  Further, the model domain only extends to River Mile 279 below Richland Creek. The EIS authors has  made the statement in a public meeting and in the EIS that the Ross Barnett discharge rate contributes minimally to that of the mouth outfalls.  

• St. Tammany Parish is concerned that with the known low-flow (and high-flow) concerns of  downstream communities and NPDES dischargers, an unsteady-state model should be  developed with its modeling domain extending to the Mouth of the West and East Pearl Rivers  at Lake Pontchartrain and the MS Sound, respectively. This would provide a more accurate  method of quantifying downstream flow impacts.  

The geographic boundary of the hydraulic and hydrologic (H&H) model domain should include the  Pearl River watershed from the Ross Barnett Reservoir to the Mississippi Sound and the Biloxi  Marshes of Louisiana. Further, due to the dynamic system downstream, an unsteady model should be  developed that will allow modeling of the entire impacted Pearl River system (Jackson to Lake  Pontchartrain and Mississippi Sound).  

• St. Tammany Parish requests that the Rankin Hinds Pearl River Flood & Drainage Control  District produce a defensible, robust unsteady model of the current conditions and projections  for all of the conceptual alternatives.  

Using data from the July 2014 sampling event, the EIS team developed a model to predict the impact of  the proposed impoundment. Figure 9 (EIS Appendix D, Water Quality, pg.119) presents model output  of dissolved oxygen (DO) for two scenarios: 1) “No Action” (current conditions) and 2) Alternative C  scenario. In the “No action” scenario, DO is significantly higher than the Alt. C scenario; however,  EIS reviewers are assured that the DO in the Alt. C scenario will remain above the CWA criteria of 5.0 mg/L. Reviewers are asked to believe that the flow rates, pollutant concentrations, temperatures and  decay coefficients used in the model are also correct. Assuming the 10th percentile flow rates were to  be used, it is doubtful that the DO would maintain CWA DO minimums.  

• St. Tammany Parish requests that a modeling scenario be conducted using “worse-case  conditions” of 10th percentile flow rates and 320C temperatures, with a minimum 20% increased  loadings to represent a margin of safety for growth.  

Further, DO appears to FAIL EPA anti-degradation criteria for dissolved oxygen (< 0.2 mg/L) with Alt.  C impoundment. LDEQ’s water quality standards define degradation as “a lowering of water  quality, as demonstrated by data analysis, water quality models, or other scientifically defensible  method.” So, a lowering of the dissolved oxygen content, as predicted by a model, is considered  degradation. Per LAC 33: IX, Chapter 15 (Water Quality Certification Procedures), LDEQ has the  responsibility to certify that federal permits or licenses will not violate water quality standards,  so the application of the antidegradation policy is not limited to industrial discharges.  

• In reviewing the discharge from the proposed Alt. C impoundment, MSDEQ and USACE are  encouraged to require compliance with the CWA anti-degradation standard upon  submittal of the final EIS and again at the USACE permit application.

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 18  

Figure 9. Predicted DO vs Observed DO at Sample Location downstream of the Ross Barnett gates  

Future Major NPDES Dischargers in the Area  

An additional new domestic wastewater treatment facility is forecast to be constructed across the Pearl  River from the Savannah St. facility and downstream of the proposed Alt. C impoundment weir. The  new facility is accounted for in the 2015 TMDL, but indicates that additional development is  anticipated. Future growth is not discussed in the EIS or accounted for in the flows and loads in the model.  

• Although additional wastewater is accommodated in the 2015 Nutrient TMDL (EPA 2015), it is  recommend that a growth factor be included in the EIS model that includes additional  stormwater runoff and water supply needs to assure that minimum flow needs and CWA  standards are met.  

Summary of Water Quality Concerns  

In summary, documentation in the sampling events and the 2015 TMDL demonstrate that water quality  from the Ross Barnett Reservoir is currently impaired with excess nutrients (eutrophic) and exceeds  EPA Clean Water Act (CWA) criteria for temperature. The proposed additional lake will certainly  exacerbate these environmental impacts unless the Alt. C inflows demonstrate considerable  improvement.  

• The Ross Barnett Reservoir operational plan should be modified to address its water quality  issues and the MS4s should be compelled through regulatory audits to improve water quality  from their respective stormwater outfalls. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 19  

As discussed previously, a minimum discharge from the Reservoir and the proposed lake is required to  provide adequate stream baseflow in order to minimize environmental impacts.  

• A minimum discharge must be determined from a large-scale modeling effort that satisfies  stream baseflow necessary for downstream dischargers, public health, habitat and ecosystem  needs. This minimum discharge from Ross Barnet and the proposed lake development should  be specified in each operational plan and be strengthened by an MOU with the States of  Mississippi and Louisiana.  
• Further, St. Tammany Parish would like the Ross Barnett operations plan to be reviewed to see  if stream baseflow could be augmented when needed to address the environmental impacts in  Louisiana resulting from low flow events.  

Business & Industrial Activity  

Construction of the Ross Barnett Reservoir began in 1960 and was completed in 1963. The 33,000  surface acre lake reached “full-pool” capacity in 19656. Following construction of the Ross Barnett  Reservoir near Jackson, MS, historical low flow discharge rates measured at the USGS stream gauge  Pearl River @ Bogalusa have decreased from 1100 cfs7 down to 1020 cfs8. It appears that the  controlled discharges from the Ross Barnett Reservoir have contributed to the reduced historic low  flows in the West Pearl River @ Bogalusa.  

Regulatory compliance for the International Paper Mill on the Pearl River near Bogalusa, LA is  dependent upon a minimum flow of 1260 cfs in the Pearl River measured at the stream gauge USGS  02489500 (Pearl River near Bogalusa, LA). During the August 2011 excursion (black liquor release),  the critical low flow was an historic 1160 cfs. This reduction in flow (coupled with permit exceedances  at the Mill, resulted in egregious environmental damage to approximately 60 river miles of the Lower  Pearl River.  

• A minimum flow release must be quantified in the EIS and included in the reservoir  operational plan. Further, the minimum flow should be formalized through an MOU with  the states of Mississippi and Louisiana.  

Further, the additional 19009 surface acre impoundment proposed by the Rankin Hinds Pearl River  Flood & Drainage Control District may further reduce the flow by as much as 10.1 cfs (per the EIS)  due to evaporative losses in the proposed impoundment.  

  

6 Engineer provided date of Ross Barnett “full pool” for the Rankin-Hinds Pearl River Flood and Drainage Control District  during a public meeting held in Slidell, LA on 8/16/2018.  

7 1100 cfs (daily mean discharge) for 9/15/1954 pre-construction.  

8 1020 cfs (daily mean discharge) 10/29/1963 post-construction.  

9 Surface acreage of the proposed lake will be enlarged from the existing 300 ft. stream profile. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 20  

Population Growth  

Apparently, the minimum flowrate for discharges released from the Ross Barnett Reservoir is based  upon regulatory compliance to accommodate the Wasteload Allocation (WLA) for Jackson, MS  Wastewater Treatment Plant (WWTP). Providing a growth factor with consequent discharge and load  estimates assures that assimilative capacity and dissolved oxygen are preserved in the stream segments downstream of this discharger.  

• The State of Mississippi should assure that a growth factor is built into this release. 

Recreation Resources  

Boating for recreation and navigation are currently compromised due to reduced flow & velocity during  critical low-flow events. Inadequate stream baseflow effects increased siltation, debris accumulation  and nuisance rooted macrophyte establishment.  

• Minimum flow agreements between the two reservoirs, along with Best Management  Practices throughout the highly erosional upper Pearl River watershed, will help reduce  further sedimentation in the lower watershed.  

Groundwater & Salt Water Intrusion  

Private drinking water wells in STP were inventoried in 2011; there were determined to be 114 wells  within ¼ mile of the West Pearl River in STP that are registered with Louisiana Department of Natural  Resources; many of which are considered to be shallow (<75’ deep). These shallow wells are  extremely vulnerable to saltwater intrusion. With increased population pressure in the Pearl River  Basin, the cone of depression will draw saltwater up into the wells. With less fresh water available, the  number of well failures is expected to increase, impacting development and public health.  

• Base flow augmentation in the Pearl River from the reservoirs should be studied to determine  minimum stream baseflows needed to relieve salt water intrusion impacts in downstream  drinking water wells and coastal marshes.  

Since 2006, the Louisiana Coastal Protection and Restoration Authority (CPRA) and the US Geological  Survey (USGS) have developed and maintained a Coastwide Reference Monitoring System (CRMS)  for wetland restoration efforts. There are three CRMS sites in the vicinity of coastal Pearl River and a  number of coastal restoration projects that are in the construction or engineering/development phase  (Figure 10). These projects are vital to the restoration and resiliency of the Louisiana coastline and  provide surge protection to inland communities.  

The CRMS site houses monitoring datasets of hydrogeomorphological parameters that characterize  coastal habitats in Louisiana. Some of the parameters that are monitored include water level, soil  porewater salinity, percent organic content and surface elevation/accretion. The CRMS site link is:  http://www.lacoast.gov/crms2/Home.aspx. All CRMS indicate increased saline concentration in  porewater, perhaps attributable to less fresh water flowing down the Pearl River in low flow months.  

• St. Tammany Parish recommends that monitoring at the CRMS sites continue, particularly to  monitor for salt water intrusion. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 21  

Figure 10. Locations of Coastal Restoration Projects and CRMS sites in the Pearl River vicinity  

The Pearl River in Louisiana is considered to be a national treasure. It is designated by LDEQ as an  Outstanding Natural Resource Water (ONRW) and by LDWF as a Scenic River and is subject to higher  WQ standards. In 2013, the LDEQ conducted a 33.5 mile intensive survey and water modeling effort to  test the proposed permit limits for the IP Mill in Bogalusa, LA. Dissolved oxygen (DO) was modeled  for the Pearl River from the Mississippi state line, upstream of Bogalusa, LA (RKm 137), to just  downstream of Walkiah Bluff, MS (RKm 84.3)10. Permit limits for the IP Mill outfalls were dependent  upon a minimum Pearl River discharge of 1260 cfs at Bogalusa.  

• Any reduction in Pearl River baseflow, particularly in low-flow events, is unacceptable.  Advective flows provide reaeration that is critical to assimilation of pollutants from permitted  dischargers to assure the health of the River and the ecosystem.  

  

10 Final – Evaluation of Biochemical Oxygen Demand Loading from the International Paper – Bogalusa Paperboard Mill  (AI# 38036, LPDES# LA0007901) into the Pearl River (Subsegments 090101 & 090107) December 3, 2013. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 22  

Threatened & Endangered Species  

The Louisiana Department of Wildlife and Fisheries may be assuming jurisdiction over the property in  and near the Pearl River owned by the USACE (Pearl River Navigation Channel). The LDWF plans to  restore habitat for Gulf Sturgeon and other endangered species with projects such as removing weirs.  The primary intent is to restore Sturgeon spawning grounds and population in the Pearl River from  Lake Pontchartrain up to the Ross Barnett Reservoir. The hope is to eliminate the endangered /  threatened status of this fish.  

• Any project implemented downstream of the Ross Barnett Reservoir needs to address minimum  stream baseflow and structures that impede habitat and spawning should be identified and  mitigations offered.  

Additional Alternatives to the Proposed “Levees with Lake”  

St. Tammany Parish also objects to the current “Levees with Lake” proposal for the problems listed  above. It also does not appear to be optimized for environmental impacts or cost. St. Tammany Parish also objects to the “Levees Only” options due to increases in downstream flooding.  

As discussed in the November 20, 2013 Public Meeting, there are other project alternatives that should be considered. Not included in the Feasibility study to reduce Jackson area flooding were nonstructural  alternatives (elevations, not just buy-outs), better management of the Ross Barnett Reservoir, and  development of better local stormwater management plans.  

A nonstructural option that was not discussed in the study or the public meeting was modification to the  operation of the existing Ross Barnett Reservoir. This alternative may have the least environmental  impact and financial costs. The reservoir appears to have the storage capacity to handle local  recreational and water needs while serving at least a limited flood protection role.  

• St. Tammany Parish suggests that the Ross Barnett Reservoir be optimized to include some  modicum of floodplain storage as an undiscussed nonstructural option.  

Finally, local stormwater management is essential to a community’s resilience. For instance, New  Orleans has collaborated with international leaders in stormwater management to produce the “Greater  New Orleans Urban Water Plan” that allows the area to manage its water resources. Responsible  development and redevelopment through local zoning and development regulations is an essential part  of “Living with Water” (http://livingwithwater.com/).  

• St. Tammany suggests that the stormwater management plans for Jackson, Flowood and vicinity  be thoroughly evaluated for opportunities to reduce runoff at the source.  

Comments above are also supported by St. Tammany Parish Council Resolutions (2008, 2013 and  2018).  

 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 23  

EXHIBIT  

Summary of St. Tammany Parish Concerns and Recommendations  

Low-Flow Concerns:  

Flows at the Jackson gage are inadequate to provide the minimal stream baseflow required for the  Savannah St, WWTP (227 cfs) during summer critical conditions. Further, the lack of adequate flow  may have contributed to the water quality impairments and promulgated TMDL in the area. Additional  stream baseflow is required even without the additional losses incurred by the Alt. C impoundment.  

• Ross Barnett Reservoir should be encouraged to discharge a minimum flow > 170 cfs required  by the MS Board of Commissioners in 1956.  

o Base flow augmentation in the Pearl River from the reservoirs should be studied to  determine minimum stream baseflows needed to relieve salt water intrusion impacts in  downstream drinking water wells and coastal marshes.  

o Any project implemented downstream of the Ross Barnett Reservoir needs to address  minimum stream baseflow and structures that impede habitat and spawning should be  identified and mitigations offered.  

• A minimum flow release, must be specified in the EIS and included in the reservoir operational plan for Alt. C. to satisfy the needs of NPDES dischargers, water quality, habitat, recreation,  navigation and coastal interests,  
• The minimum flows from both reservoirs should be formalized through an MOU between Ross  Barnett and proposed Alt. C impoundment for flow management and with the States of  Mississippi and Louisiana.  
• In the Alt. C operational plan, the tandem operations of the two gates from the respective  reservoirs must be detailed.  
• Ross Barnett operations plan should be reviewed to see if stream baseflow could be augmented  when needed to address the environmental impacts in Louisiana resulting from low flow events.  
• Salinity monitoring of the CRMS sites in the Lower Pearl River Basin should be continued.  

o Additionally, funding to sample representative community wells would be a benefit to  determining long-term impacts of freshwater flow to offset salt water intrusion.  

• Ross Barnett Reservoir should be optimized to include some modicum of floodplain storage as a  nonstructural option not discussed in the EIS.  

Losses during low-flow conditions must be more critically calculated:  

• Evaporative losses subtracted from either the Minimum Daily Mean Discharges by Month (Figure 6) or the 10th percentile of Mean Daily Discharges (Table 5) indicate the already impacted Pearl River will be further compromised.  
• Seepage losses/gains in the proposed impoundment were not addressed in the EIS. Losses  would require an increased minimum discharge from the Ross Barnett Reservoir in order to  maintain adequate downstream flows during low-flow events. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 24  

o A geotechnical investigation is needed in order to determine whether there will be gains  or losses in the proposed impoundment due to groundwater effects.  

 High-Flow Concerns:  

“Slugs” of water from Ross Barnett Reservoir during high-flow events cause bank erosion and  excessive sediment transport to downstream reaches. St. Tammany Parish is concerned with how the  proposed impoundment will compensate for the “slugs” from the Ross Barnett.  

• As with low-flow considerations, the high-flow operational plan must be detailed in the EIS.  • Sediment transport should be included in the modeling effort in the EIS.  

Some sediment is necessary to maintain bank stability, but an excess will add to the over-burdened  lower Pearl River.  

• St. Tammany Parish would like the EIS to include a discussion of the maintenance procedures  to maintain Alt. C storage capacity and to minimize downstream sediment loading.  

Water Quality:  

Water quality in the tributaries discharging into the proposed impoundment is dominated by NPS from  the nine MS4s on those tributaries: 

• The EIS must address whether WQ improvements have been achieved in the MS4s and the Ross  Barnett discharges in the seven (7) years since the Stormwater Master Plan and TMDL were  promulgated.  
• Does the proposed impoundment have a plan to improve water quality prior to release?  • In reviewing the discharge from the proposed Alt. C impoundment, MSDEQ and USACE are  encouraged to require compliance with the CWA anti-degradation standard upon  submittal of the final EIS and again at the USACE permit application. 
• Although additional wastewater is accommodated in the 2015 Nutrient TMDL (EPA 2015), it is  recommend that a growth factor be included in the EIS model that includes additional  stormwater runoff and water supply needs to assure that minimum flow needs and CWA  standards are met.  
• Although additional wastewater is accommodated in the 2015 Nutrient TMDL (EPA 2015), it is  recommend that a growth factor be included in the EIS model that includes additional  stormwater runoff and water supply needs to assure that minimum flow needs and CWA  standards are met.  
• The Ross Barnett Reservoir operational plan should be modified to address its water quality  issues and the MS4s should be compelled through regulatory audits to improve water quality  from their respective stormwater outfalls.  
• St. Tammany suggests that the stormwater management plans for Jackson, Flowood and vicinity  be thoroughly evaluated for opportunities to reduce runoff at the source. 

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 25  

Modeling Requirements:  

The EIS authors state that the Ross Barnett discharge rate contributes minimally to that of the mouth  outfalls.  

• Rankin Hinds Pearl River Flood & Drainage Control District should produce a defensible,  robust unsteady model of the current conditions and projections for all of the conceptual  alternatives.  
• The geographic boundary of the hydraulic and hydrologic (H&H) model domain should include  the Pearl River watershed from the Ross Barnett Reservoir to the Mississippi Sound and the  Biloxi Marshes of Louisiana to provide a more accurate method of quantifying downstream  flow impacts.  
• A modeling scenario should be conducted using “worse-case conditions” of 10th percentile flow  rates and 320C temperatures, with a minimum 20% increased loadings to represent a margin of  safety for growth.  
• A minimum discharge from the Ross Barnett Reservoir and the proposed lake is required to  provide adequate stream baseflow in order to minimize environmental impacts.  

o A minimum discharge must be determined from a large-scale modeling effort that  satisfies stream baseflow necessary for downstream dischargers, public health, habitat  and ecosystem needs.  

• An unsteady model showing both maximum flooding and duration of flooding needs to be run  for all conceptual alternatives over the entire model domain (Ross Barnett Reservoir to Lake  Pontchartrain and the Mississippi Sound.  
• Providing a growth factor with consequent discharge and load estimates assures that  assimilative capacity and dissolved oxygen are preserved in the stream segments downstream of  this discharger.  

o The State of Mississippi should assure that a growth factor is built into this release. 

• A Water Budget should be developed for LA from Lake Pontchartrain to LS-MS state line to  determine water needs for the Lower Pearl River Basin 

Maintenance of existing structures:  

A significant amount of debris is reportedly blocking the structure’s weir lessening the amount of fresh  water being diverted.  

• It is suggested that the USACE conduct maintenance on the Walkiah Bluff structure to assure  adequate freshwater to East Pearl during critical low-flow conditions

St Tammany Parish comments to the Pearl River Basin, Mississippi Section 211 Feasibility Study – Integrated Draft  Feasibility and Environmental Impact Statement 090618 26